Adding upstream version 252.22.upstream/252.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

66 files changed, 21617 insertions, 0 deletions

diff --git a/src/libsystemd-network/arp-util.c b/src/libsystemd-network/arp-util.c
new file mode 100644
index 0000000..99a5f69
--- /dev/null
+++ b/src/libsystemd-network/arp-util.c
@@ -0,0 +1,140 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Axis Communications AB. All rights reserved.
+***/
+
+#include <arpa/inet.h>
+#include <linux/filter.h>
+#include <netinet/if_ether.h>
+
+#include "arp-util.h"
+#include "ether-addr-util.h"
+#include "fd-util.h"
+#include "in-addr-util.h"
+#include "unaligned.h"
+#include "util.h"
+
+int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *mac) {
+        struct sock_filter filter[] = {
+                BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                         /* A <- packet length */
+                BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(struct ether_arp), 1, 0),           /* packet >= arp packet ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hrd)), /* A <- header */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPHRD_ETHER, 1, 0),                       /* header == ethernet ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pro)), /* A <- protocol */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_IP, 1, 0),                       /* protocol == IP ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_hln)), /* A <- hardware address length */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct ether_addr), 1, 0),          /* length == sizeof(ether_addr)? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_pln)), /* A <- protocol address length */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, sizeof(struct in_addr), 1, 0),             /* length == sizeof(in_addr) ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, ea_hdr.ar_op)),  /* A <- operation */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REQUEST, 2, 0),                      /* protocol == request ? */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ARPOP_REPLY, 1, 0),                        /* protocol == reply ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                /* Sender Hardware Address must be different from our own */
+                BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be32(&mac->ether_addr_octet[0])),   /* X <- 4 bytes of client's MAC */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_sha)),       /* A <- 4 bytes of SHA */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 4),                                  /* A == X ? */
+                BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be16(&mac->ether_addr_octet[4])),   /* X <- remainder of client's MAC */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ether_arp, arp_sha) + 4),   /* A <- remainder of SHA */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 1),                                  /* A == X ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+                /* Sender Protocol Address or Target Protocol Address must be equal to the one we care about */
+                BPF_STMT(BPF_LDX + BPF_IMM, htobe32(a->s_addr)),                               /* X <- clients IP */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_spa)),       /* A <- SPA */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 1),                                  /* A == X ? */
+                BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                         /* accept */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ether_arp, arp_tpa)),       /* A <- TPA */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 0, 1),                                  /* A == 0 ? */
+                BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                         /* accept */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                                  /* ignore */
+        };
+        struct sock_fprog fprog = {
+                .len    = ELEMENTSOF(filter),
+                .filter = (struct sock_filter*) filter,
+        };
+
+        assert(fd >= 0);
+
+        if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog)) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const struct ether_addr *mac) {
+        union sockaddr_union link = {
+                .ll.sll_family   = AF_PACKET,
+                .ll.sll_protocol = htobe16(ETH_P_ARP),
+                .ll.sll_ifindex  = ifindex,
+                .ll.sll_halen    = ETH_ALEN,
+                .ll.sll_addr     = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
+        };
+        _cleanup_close_ int s = -1;
+        int r;
+
+        assert(ifindex > 0);
+        assert(mac);
+
+        s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (s < 0)
+                return -errno;
+
+        r = arp_update_filter(s, a, mac);
+        if (r < 0)
+                return r;
+
+        if (bind(s, &link.sa, sizeof(link.ll)) < 0)
+                return -errno;
+
+        return TAKE_FD(s);
+}
+
+int arp_send_packet(
+                int fd,
+                int ifindex,
+                const struct in_addr *pa,
+                const struct ether_addr *ha,
+                bool announce) {
+
+        union sockaddr_union link = {
+                .ll.sll_family   = AF_PACKET,
+                .ll.sll_protocol = htobe16(ETH_P_ARP),
+                .ll.sll_ifindex  = ifindex,
+                .ll.sll_halen    = ETH_ALEN,
+                .ll.sll_addr     = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff },
+        };
+        struct ether_arp arp = {
+                .ea_hdr.ar_hrd = htobe16(ARPHRD_ETHER),  /* HTYPE */
+                .ea_hdr.ar_pro = htobe16(ETHERTYPE_IP),  /* PTYPE */
+                .ea_hdr.ar_hln = ETH_ALEN,               /* HLEN */
+                .ea_hdr.ar_pln = sizeof(struct in_addr), /* PLEN */
+                .ea_hdr.ar_op  = htobe16(ARPOP_REQUEST), /* REQUEST */
+        };
+        ssize_t n;
+
+        assert(fd >= 0);
+        assert(ifindex > 0);
+        assert(pa);
+        assert(in4_addr_is_set(pa));
+        assert(ha);
+        assert(!ether_addr_is_null(ha));
+
+        memcpy(&arp.arp_sha, ha, ETH_ALEN);
+        memcpy(&arp.arp_tpa, pa, sizeof(struct in_addr));
+
+        if (announce)
+                memcpy(&arp.arp_spa, pa, sizeof(struct in_addr));
+
+        n = sendto(fd, &arp, sizeof(struct ether_arp), 0, &link.sa, sizeof(link.ll));
+        if (n < 0)
+                return -errno;
+        if (n != sizeof(struct ether_arp))
+                return -EIO;
+
+        return 0;
+}
diff --git a/src/libsystemd-network/arp-util.h b/src/libsystemd-network/arp-util.h
new file mode 100644
index 0000000..b66a81b
--- /dev/null
+++ b/src/libsystemd-network/arp-util.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2014 Axis Communications AB. All rights reserved.
+***/
+
+#include <net/ethernet.h>
+#include <netinet/in.h>
+
+#include "socket-util.h"
+#include "sparse-endian.h"
+
+int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *mac);
+int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const struct ether_addr *mac);
+
+int arp_send_packet(
+                int fd,
+                int ifindex,
+                const struct in_addr *pa,
+                const struct ether_addr *ha,
+                bool announce);
+static inline int arp_send_probe(
+                int fd,
+                int ifindex,
+                const struct in_addr *pa,
+                const struct ether_addr *ha) {
+        return arp_send_packet(fd, ifindex, pa, ha, false);
+}
+static inline int arp_send_announcement(
+                int fd,
+                int ifindex,
+                const struct in_addr *pa,
+                const struct ether_addr *ha) {
+        return arp_send_packet(fd, ifindex, pa, ha, true);
+}
diff --git a/src/libsystemd-network/dhcp-client-internal.h b/src/libsystemd-network/dhcp-client-internal.h
new file mode 100644
index 0000000..a6f3752
--- /dev/null
+++ b/src/libsystemd-network/dhcp-client-internal.h
@@ -0,0 +1,4 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+extern const struct hash_ops dhcp_option_hash_ops;
diff --git a/src/libsystemd-network/dhcp-identifier.c b/src/libsystemd-network/dhcp-identifier.c
new file mode 100644
index 0000000..68f6a7c
--- /dev/null
+++ b/src/libsystemd-network/dhcp-identifier.c
@@ -0,0 +1,272 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <linux/if_infiniband.h>
+#include <net/ethernet.h>
+#include <net/if_arp.h>
+
+#include "sd-device.h"
+#include "sd-id128.h"
+
+#include "dhcp-identifier.h"
+#include "netif-util.h"
+#include "siphash24.h"
+#include "sparse-endian.h"
+#include "string-table.h"
+#include "udev-util.h"
+
+#define HASH_KEY       SD_ID128_MAKE(80,11,8c,c2,fe,4a,03,ee,3e,d6,0c,6f,36,39,14,09)
+#define APPLICATION_ID SD_ID128_MAKE(a5,0a,d1,12,bf,60,45,77,a2,fb,74,1a,b1,95,5b,03)
+#define USEC_2000       ((usec_t) 946684800000000) /* 2000-01-01 00:00:00 UTC */
+
+static const char * const duid_type_table[_DUID_TYPE_MAX] = {
+        [DUID_TYPE_LLT]  = "DUID-LLT",
+        [DUID_TYPE_EN]   = "DUID-EN/Vendor",
+        [DUID_TYPE_LL]   = "DUID-LL",
+        [DUID_TYPE_UUID] = "UUID",
+};
+
+DEFINE_STRING_TABLE_LOOKUP_TO_STRING(duid_type, DUIDType);
+
+int dhcp_validate_duid_len(DUIDType duid_type, size_t duid_len, bool strict) {
+        struct duid d;
+
+        assert_cc(sizeof(d.raw) >= MAX_DUID_LEN);
+        if (duid_len > MAX_DUID_LEN)
+                return -EINVAL;
+
+        if (!strict)
+                /* Strict validation is not requested. We only ensure that the
+                 * DUID is not too long. */
+                return 0;
+
+        switch (duid_type) {
+        case DUID_TYPE_LLT:
+                if (duid_len <= sizeof(d.llt))
+                        return -EINVAL;
+                break;
+        case DUID_TYPE_EN:
+                if (duid_len != sizeof(d.en))
+                        return -EINVAL;
+                break;
+        case DUID_TYPE_LL:
+                if (duid_len <= sizeof(d.ll))
+                        return -EINVAL;
+                break;
+        case DUID_TYPE_UUID:
+                if (duid_len != sizeof(d.uuid))
+                        return -EINVAL;
+                break;
+        default:
+                /* accept unknown type in order to be forward compatible */
+                break;
+        }
+        return 0;
+}
+
+static int dhcp_identifier_set_duid_llt(
+                const struct hw_addr_data *hw_addr,
+                uint16_t arp_type,
+                usec_t t,
+                struct duid *ret_duid,
+                size_t *ret_len) {
+
+        uint16_t time_from_2000y;
+
+        assert(hw_addr);
+        assert(ret_duid);
+        assert(ret_len);
+
+        if (hw_addr->length == 0)
+                return -EOPNOTSUPP;
+
+        if (arp_type == ARPHRD_ETHER)
+                assert_return(hw_addr->length == ETH_ALEN, -EINVAL);
+        else if (arp_type == ARPHRD_INFINIBAND)
+                assert_return(hw_addr->length == INFINIBAND_ALEN, -EINVAL);
+        else
+                return -EOPNOTSUPP;
+
+        if (t < USEC_2000)
+                time_from_2000y = 0;
+        else
+                time_from_2000y = (uint16_t) (((t - USEC_2000) / USEC_PER_SEC) & 0xffffffff);
+
+        unaligned_write_be16(&ret_duid->type, DUID_TYPE_LLT);
+        unaligned_write_be16(&ret_duid->llt.htype, arp_type);
+        unaligned_write_be32(&ret_duid->llt.time, time_from_2000y);
+        memcpy(ret_duid->llt.haddr, hw_addr->bytes, hw_addr->length);
+
+        *ret_len = offsetof(struct duid, llt.haddr) + hw_addr->length;
+
+        return 0;
+}
+
+static int dhcp_identifier_set_duid_ll(
+                const struct hw_addr_data *hw_addr,
+                uint16_t arp_type,
+                struct duid *ret_duid,
+                size_t *ret_len) {
+
+        assert(hw_addr);
+        assert(ret_duid);
+        assert(ret_len);
+
+        if (hw_addr->length == 0)
+                return -EOPNOTSUPP;
+
+        if (arp_type == ARPHRD_ETHER)
+                assert_return(hw_addr->length == ETH_ALEN, -EINVAL);
+        else if (arp_type == ARPHRD_INFINIBAND)
+                assert_return(hw_addr->length == INFINIBAND_ALEN, -EINVAL);
+        else
+                return -EOPNOTSUPP;
+
+        unaligned_write_be16(&ret_duid->type, DUID_TYPE_LL);
+        unaligned_write_be16(&ret_duid->ll.htype, arp_type);
+        memcpy(ret_duid->ll.haddr, hw_addr->bytes, hw_addr->length);
+
+        *ret_len = offsetof(struct duid, ll.haddr) + hw_addr->length;
+
+        return 0;
+}
+
+int dhcp_identifier_set_duid_en(bool test_mode, struct duid *ret_duid, size_t *ret_len) {
+        sd_id128_t machine_id;
+        uint64_t hash;
+        int r;
+
+        assert(ret_duid);
+        assert(ret_len);
+
+        if (!test_mode) {
+                r = sd_id128_get_machine(&machine_id);
+                if (r < 0)
+                        return r;
+        } else
+                /* For tests, especially for fuzzers, reproducibility is important.
+                 * Hence, use a static and constant machine ID.
+                 * See 9216fddc5a8ac2742e6cfa7660f95c20ca4f2193. */
+                machine_id = SD_ID128_MAKE(01, 02, 03, 04, 05, 06, 07, 08, 09, 0a, 0b, 0c, 0d, 0e, 0f, 10);
+
+        unaligned_write_be16(&ret_duid->type, DUID_TYPE_EN);
+        unaligned_write_be32(&ret_duid->en.pen, SYSTEMD_PEN);
+
+        /* a bit of snake-oil perhaps, but no need to expose the machine-id
+         * directly; duid->en.id might not be aligned, so we need to copy */
+        hash = htole64(siphash24(&machine_id, sizeof(machine_id), HASH_KEY.bytes));
+        memcpy(ret_duid->en.id, &hash, sizeof(ret_duid->en.id));
+
+        *ret_len = offsetof(struct duid, en.id) + sizeof(ret_duid->en.id);
+
+        if (test_mode)
+                assert_se(memcmp(ret_duid, (const uint8_t[]) { 0x00, 0x02, 0x00, 0x00, 0xab, 0x11, 0x61, 0x77, 0x40, 0xde, 0x13, 0x42, 0xc3, 0xa2 }, *ret_len) == 0);
+
+        return 0;
+}
+
+static int dhcp_identifier_set_duid_uuid(struct duid *ret_duid, size_t *ret_len) {
+        sd_id128_t machine_id;
+        int r;
+
+        assert(ret_duid);
+        assert(ret_len);
+
+        r = sd_id128_get_machine_app_specific(APPLICATION_ID, &machine_id);
+        if (r < 0)
+                return r;
+
+        unaligned_write_be16(&ret_duid->type, DUID_TYPE_UUID);
+        memcpy(&ret_duid->uuid.uuid, &machine_id, sizeof(machine_id));
+
+        *ret_len = offsetof(struct duid, uuid.uuid) + sizeof(machine_id);
+
+        return 0;
+}
+
+int dhcp_identifier_set_duid(
+                DUIDType duid_type,
+                const struct hw_addr_data *hw_addr,
+                uint16_t arp_type,
+                usec_t llt_time,
+                bool test_mode,
+                struct duid *ret_duid,
+                size_t *ret_len) {
+
+        switch (duid_type) {
+        case DUID_TYPE_LLT:
+                return dhcp_identifier_set_duid_llt(hw_addr, arp_type, llt_time, ret_duid, ret_len);
+        case DUID_TYPE_EN:
+                return dhcp_identifier_set_duid_en(test_mode, ret_duid, ret_len);
+        case DUID_TYPE_LL:
+                return dhcp_identifier_set_duid_ll(hw_addr, arp_type, ret_duid, ret_len);
+        case DUID_TYPE_UUID:
+                return dhcp_identifier_set_duid_uuid(ret_duid, ret_len);
+        default:
+                return -EINVAL;
+        }
+}
+
+int dhcp_identifier_set_iaid(
+                int ifindex,
+                const struct hw_addr_data *hw_addr,
+                bool legacy_unstable_byteorder,
+                bool use_mac,
+                void *ret) {
+
+        /* name is a pointer to memory in the sd_device struct, so must
+         * have the same scope */
+        _cleanup_(sd_device_unrefp) sd_device *device = NULL;
+        const char *name = NULL;
+        uint32_t id32;
+        uint64_t id;
+        int r;
+
+        assert(ifindex > 0);
+        assert(hw_addr);
+        assert(ret);
+
+        if (udev_available() && !use_mac) {
+                /* udev should be around */
+
+                r = sd_device_new_from_ifindex(&device, ifindex);
+                if (r < 0)
+                        return r;
+
+                r = sd_device_get_is_initialized(device);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        /* not yet ready */
+                        return -EBUSY;
+
+                r = device_is_renaming(device);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        /* device is under renaming */
+                        return -EBUSY;
+
+                name = net_get_persistent_name(device);
+        }
+
+        if (name)
+                id = siphash24(name, strlen(name), HASH_KEY.bytes);
+        else
+                /* fall back to MAC address if no predictable name available */
+                id = siphash24(hw_addr->bytes, hw_addr->length, HASH_KEY.bytes);
+
+        id32 = (id & 0xffffffff) ^ (id >> 32);
+
+        if (legacy_unstable_byteorder)
+                /* for historical reasons (a bug), the bits were swapped and thus
+                 * the result was endianness dependent. Preserve that behavior. */
+                id32 = bswap_32(id32);
+        else
+                /* the fixed behavior returns a stable byte order. Since LE is expected
+                 * to be more common, swap the bytes on LE to give the same as legacy
+                 * behavior. */
+                id32 = be32toh(id32);
+
+        unaligned_write_ne32(ret, id32);
+        return 0;
+}
diff --git a/src/libsystemd-network/dhcp-identifier.h b/src/libsystemd-network/dhcp-identifier.h
new file mode 100644
index 0000000..8acb8c3
--- /dev/null
+++ b/src/libsystemd-network/dhcp-identifier.h
@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-id128.h"
+
+#include "ether-addr-util.h"
+#include "macro.h"
+#include "sparse-endian.h"
+#include "time-util.h"
+#include "unaligned.h"
+
+#define SYSTEMD_PEN    43793
+
+typedef enum DUIDType {
+        DUID_TYPE_LLT       = 1,
+        DUID_TYPE_EN        = 2,
+        DUID_TYPE_LL        = 3,
+        DUID_TYPE_UUID      = 4,
+        _DUID_TYPE_MAX,
+        _DUID_TYPE_INVALID  = -EINVAL,
+} DUIDType;
+
+/* RFC 3315 section 9.1:
+ *      A DUID can be no more than 128 octets long (not including the type code).
+ */
+#define MAX_DUID_LEN 128
+
+/* https://tools.ietf.org/html/rfc3315#section-9.1 */
+struct duid {
+        be16_t type;
+        union {
+                struct {
+                        /* DUID_TYPE_LLT */
+                        be16_t htype;
+                        be32_t time;
+                        uint8_t haddr[0];
+                } _packed_ llt;
+                struct {
+                        /* DUID_TYPE_EN */
+                        be32_t pen;
+                        uint8_t id[8];
+                } _packed_ en;
+                struct {
+                        /* DUID_TYPE_LL */
+                        be16_t htype;
+                        uint8_t haddr[0];
+                } _packed_ ll;
+                struct {
+                        /* DUID_TYPE_UUID */
+                        sd_id128_t uuid;
+                } _packed_ uuid;
+                struct {
+                        uint8_t data[MAX_DUID_LEN];
+                } _packed_ raw;
+        };
+} _packed_;
+
+int dhcp_validate_duid_len(DUIDType duid_type, size_t duid_len, bool strict);
+int dhcp_identifier_set_duid_en(bool test_mode, struct duid *ret_duid, size_t *ret_len);
+int dhcp_identifier_set_duid(
+                DUIDType duid_type,
+                const struct hw_addr_data *hw_addr,
+                uint16_t arp_type,
+                usec_t llt_time,
+                bool test_mode,
+                struct duid *ret_duid,
+                size_t *ret_len);
+int dhcp_identifier_set_iaid(
+                int ifindex,
+                const struct hw_addr_data *hw_addr,
+                bool legacy_unstable_byteorder,
+                bool use_mac,
+                void *ret);
+
+const char *duid_type_to_string(DUIDType t) _const_;
diff --git a/src/libsystemd-network/dhcp-internal.h b/src/libsystemd-network/dhcp-internal.h
new file mode 100644
index 0000000..a311d1d
--- /dev/null
+++ b/src/libsystemd-network/dhcp-internal.h
@@ -0,0 +1,89 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <linux/if_packet.h>
+#include <net/ethernet.h>
+#include <stdint.h>
+
+#include "sd-dhcp-client.h"
+
+#include "dhcp-protocol.h"
+#include "ether-addr-util.h"
+#include "network-common.h"
+#include "socket-util.h"
+
+typedef struct sd_dhcp_option {
+        unsigned n_ref;
+
+        uint8_t option;
+        void *data;
+        size_t length;
+} sd_dhcp_option;
+
+typedef struct DHCPServerData {
+        struct in_addr *addr;
+        size_t size;
+} DHCPServerData;
+
+extern const struct hash_ops dhcp_option_hash_ops;
+
+typedef struct sd_dhcp_client sd_dhcp_client;
+
+int dhcp_network_bind_raw_socket(
+                int ifindex,
+                union sockaddr_union *link,
+                uint32_t xid,
+                const struct hw_addr_data *hw_addr,
+                const struct hw_addr_data *bcast_addr,
+                uint16_t arp_type,
+                uint16_t port);
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type);
+int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link,
+                                 const void *packet, size_t len);
+int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port,
+                                 const void *packet, size_t len);
+
+int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset, uint8_t overload,
+                       uint8_t code, size_t optlen, const void *optval);
+int dhcp_option_find_option(uint8_t *options, size_t length, uint8_t wanted_code, size_t *ret_offset);
+int dhcp_option_remove_option(uint8_t *options, size_t buflen, uint8_t option_code);
+
+typedef int (*dhcp_option_callback_t)(uint8_t code, uint8_t len,
+                                const void *option, void *userdata);
+
+int dhcp_option_parse(DHCPMessage *message, size_t len, dhcp_option_callback_t cb, void *userdata, char **error_message);
+
+int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid,
+                      uint8_t type, uint16_t arp_type, uint8_t hlen, const uint8_t *chaddr,
+                      size_t optlen, size_t *optoffset);
+
+uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len);
+
+void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
+                                   uint16_t source, be32_t destination_addr,
+                                   uint16_t destination, uint16_t len, int ip_service_type);
+
+int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port);
+
+void dhcp_client_set_test_mode(sd_dhcp_client *client, bool test_mode);
+
+/* If we are invoking callbacks of a dhcp-client, ensure unreffing the
+ * client from the callback doesn't destroy the object we are working
+ * on */
+#define DHCP_CLIENT_DONT_DESTROY(client) \
+        _cleanup_(sd_dhcp_client_unrefp) _unused_ sd_dhcp_client *_dont_destroy_##client = sd_dhcp_client_ref(client)
+
+#define log_dhcp_client_errno(client, error, fmt, ...)          \
+        log_interface_prefix_full_errno(                        \
+                "DHCPv4 client: ",                              \
+                sd_dhcp_client, client,                         \
+                error, fmt, ##__VA_ARGS__)
+#define log_dhcp_client(client, fmt, ...)                       \
+        log_interface_prefix_full_errno_zerook(                 \
+                "DHCPv4 client: ",                              \
+                sd_dhcp_client, client,                         \
+                0, fmt, ##__VA_ARGS__)
diff --git a/src/libsystemd-network/dhcp-lease-internal.h b/src/libsystemd-network/dhcp-lease-internal.h
new file mode 100644
index 0000000..c67e951
--- /dev/null
+++ b/src/libsystemd-network/dhcp-lease-internal.h
@@ -0,0 +1,90 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include "sd-dhcp-client.h"
+
+#include "dhcp-internal.h"
+#include "dhcp-protocol.h"
+#include "list.h"
+#include "util.h"
+
+struct sd_dhcp_route {
+        struct in_addr dst_addr;
+        struct in_addr gw_addr;
+        unsigned char dst_prefixlen;
+};
+
+struct sd_dhcp_raw_option {
+        LIST_FIELDS(struct sd_dhcp_raw_option, options);
+
+        uint8_t tag;
+        uint8_t length;
+        void *data;
+};
+
+struct sd_dhcp_lease {
+        unsigned n_ref;
+
+        /* each 0 if unset */
+        uint32_t t1;
+        uint32_t t2;
+        uint32_t lifetime;
+
+        /* each 0 if unset */
+        be32_t address;
+        be32_t server_address;
+        be32_t next_server;
+
+        bool have_subnet_mask;
+        be32_t subnet_mask;
+
+        bool have_broadcast;
+        be32_t broadcast;
+
+        struct in_addr *router;
+        size_t router_size;
+
+        DHCPServerData servers[_SD_DHCP_LEASE_SERVER_TYPE_MAX];
+
+        struct sd_dhcp_route *static_routes;
+        size_t n_static_routes;
+        struct sd_dhcp_route *classless_routes;
+        size_t n_classless_routes;
+
+        uint16_t mtu; /* 0 if unset */
+
+        char *domainname;
+        char **search_domains;
+        char *hostname;
+        char *root_path;
+
+        void *client_id;
+        size_t client_id_len;
+
+        void *vendor_specific;
+        size_t vendor_specific_len;
+
+        char *timezone;
+
+        uint8_t sixrd_ipv4masklen;
+        uint8_t sixrd_prefixlen;
+        struct in6_addr sixrd_prefix;
+        struct in_addr *sixrd_br_addresses;
+        size_t sixrd_n_br_addresses;
+
+        LIST_HEAD(struct sd_dhcp_raw_option, private_options);
+};
+
+int dhcp_lease_new(sd_dhcp_lease **ret);
+
+int dhcp_lease_parse_options(uint8_t code, uint8_t len, const void *option, void *userdata);
+int dhcp_lease_parse_search_domains(const uint8_t *option, size_t len, char ***domains);
+int dhcp_lease_insert_private_option(sd_dhcp_lease *lease, uint8_t tag, const void *data, uint8_t len);
+
+int dhcp_lease_set_default_subnet_mask(sd_dhcp_lease *lease);
+
+int dhcp_lease_set_client_id(sd_dhcp_lease *lease, const void *client_id, size_t client_id_len);
diff --git a/src/libsystemd-network/dhcp-network.c b/src/libsystemd-network/dhcp-network.c
new file mode 100644
index 0000000..0ee977a
--- /dev/null
+++ b/src/libsystemd-network/dhcp-network.c
@@ -0,0 +1,269 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <net/ethernet.h>
+#include <net/if.h>
+#include <net/if_arp.h>
+#include <stdio.h>
+#include <string.h>
+#include <linux/filter.h>
+#include <linux/if_infiniband.h>
+#include <linux/if_packet.h>
+
+#include "dhcp-internal.h"
+#include "fd-util.h"
+#include "socket-util.h"
+#include "unaligned.h"
+
+static int _bind_raw_socket(
+                int ifindex,
+                union sockaddr_union *link,
+                uint32_t xid,
+                const struct hw_addr_data *hw_addr,
+                const struct hw_addr_data *bcast_addr,
+                uint16_t arp_type,
+                uint16_t port) {
+
+        assert(ifindex > 0);
+        assert(link);
+        assert(hw_addr);
+        assert(bcast_addr);
+        assert(IN_SET(arp_type, ARPHRD_ETHER, ARPHRD_INFINIBAND));
+
+        switch (arp_type) {
+        case ARPHRD_ETHER:
+                assert(hw_addr->length == ETH_ALEN);
+                assert(bcast_addr->length == ETH_ALEN);
+                break;
+        case ARPHRD_INFINIBAND:
+                assert(hw_addr->length == 0);
+                assert(bcast_addr->length == INFINIBAND_ALEN);
+                break;
+        default:
+                assert_not_reached();
+        }
+
+        struct sock_filter filter[] = {
+                BPF_STMT(BPF_LD + BPF_W + BPF_LEN, 0),                                 /* A <- packet length */
+                BPF_JUMP(BPF_JMP + BPF_JGE + BPF_K, sizeof(DHCPPacket), 1, 0),         /* packet >= DHCPPacket ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.protocol)), /* A <- IP protocol */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, IPPROTO_UDP, 1, 0),                /* IP protocol == UDP ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags */
+                BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x20),                             /* A <- A & 0x20 (More Fragments bit) */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, ip.frag_off)), /* A <- Flags + Fragment offset */
+                BPF_STMT(BPF_ALU + BPF_AND + BPF_K, 0x1fff),                           /* A <- A & 0x1fff (Fragment offset) */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0, 1, 0),                          /* A == 0 ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, udp.dest)),    /* A <- UDP destination port */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, port, 1, 0),                       /* UDP destination port == DHCP client port ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.op)),     /* A <- DHCP op */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, BOOTREPLY, 1, 0),                  /* op == BOOTREPLY ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.htype)),  /* A <- DHCP header type */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, arp_type, 1, 0),                   /* header type == arp_type ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.xid)),    /* A <- client identifier */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, xid, 1, 0),                        /* client identifier == xid ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_LD + BPF_B + BPF_ABS, offsetof(DHCPPacket, dhcp.hlen)),   /* A <- MAC address length */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, (uint8_t) hw_addr->length, 1, 0),  /* address length == hw_addr->length ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+
+                /* We only support MAC address length to be either 0 or 6 (ETH_ALEN). Optionally
+                 * compare chaddr for ETH_ALEN bytes. */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETH_ALEN, 0, 8),                        /* A (the MAC address length) == ETH_ALEN ? */
+                BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be32(hw_addr->bytes)),           /* X <- 4 bytes of client's MAC */
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr)),      /* A <- 4 bytes of MAC from dhcp.chaddr */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 1, 0),                               /* A == X ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                               /* ignore */
+                BPF_STMT(BPF_LDX + BPF_IMM, unaligned_read_be16(hw_addr->bytes + 4)),       /* X <- remainder of client's MAC */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(DHCPPacket, dhcp.chaddr) + 4),  /* A <- remainder of MAC from dhcp.chaddr */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_X, 0, 1, 0),                               /* A == X ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                               /* ignore */
+
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(DHCPPacket, dhcp.magic)),  /* A <- DHCP magic cookie */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, DHCP_MAGIC_COOKIE, 1, 0),          /* cookie == DHCP magic cookie ? */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                          /* ignore */
+                BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                 /* accept */
+        };
+        struct sock_fprog fprog = {
+                .len = ELEMENTSOF(filter),
+                .filter = filter
+        };
+        _cleanup_close_ int s = -1;
+        int r;
+
+        s = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (s < 0)
+                return -errno;
+
+        r = setsockopt_int(s, SOL_PACKET, PACKET_AUXDATA, true);
+        if (r < 0)
+                return r;
+
+        r = setsockopt(s, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog));
+        if (r < 0)
+                return -errno;
+
+        link->ll = (struct sockaddr_ll) {
+                .sll_family = AF_PACKET,
+                .sll_protocol = htobe16(ETH_P_IP),
+                .sll_ifindex = ifindex,
+                .sll_hatype = htobe16(arp_type),
+                .sll_halen = bcast_addr->length,
+        };
+        /* We may overflow link->ll. link->ll_buffer ensures we have enough space. */
+        memcpy(link->ll.sll_addr, bcast_addr->bytes, bcast_addr->length);
+
+        r = bind(s, &link->sa, SOCKADDR_LL_LEN(link->ll));
+        if (r < 0)
+                return -errno;
+
+        return TAKE_FD(s);
+}
+
+int dhcp_network_bind_raw_socket(
+                int ifindex,
+                union sockaddr_union *link,
+                uint32_t xid,
+                const struct hw_addr_data *hw_addr,
+                const struct hw_addr_data *bcast_addr,
+                uint16_t arp_type,
+                uint16_t port) {
+
+        static struct hw_addr_data default_eth_bcast = {
+                .length = ETH_ALEN,
+                .ether = {{ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }},
+        }, default_ib_bcast = {
+                .length = INFINIBAND_ALEN,
+                .infiniband = {
+                        0x00, 0xff, 0xff, 0xff, 0xff, 0x12, 0x40, 0x1b,
+                        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                        0xff, 0xff, 0xff, 0xff
+                },
+        };
+
+        assert(ifindex > 0);
+        assert(link);
+        assert(hw_addr);
+
+        switch (arp_type) {
+        case ARPHRD_ETHER:
+                return _bind_raw_socket(ifindex, link, xid,
+                                        hw_addr,
+                                        (bcast_addr && !hw_addr_is_null(bcast_addr)) ? bcast_addr : &default_eth_bcast,
+                                        arp_type, port);
+
+        case ARPHRD_INFINIBAND:
+                return _bind_raw_socket(ifindex, link, xid,
+                                        &HW_ADDR_NULL,
+                                        (bcast_addr && !hw_addr_is_null(bcast_addr)) ? bcast_addr : &default_ib_bcast,
+                                        arp_type, port);
+        default:
+                return -EINVAL;
+        }
+}
+
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
+        union sockaddr_union src = {
+                .in.sin_family = AF_INET,
+                .in.sin_port = htobe16(port),
+                .in.sin_addr.s_addr = address,
+        };
+        _cleanup_close_ int s = -1;
+        int r;
+
+        s = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (s < 0)
+                return -errno;
+
+        if (ip_service_type >= 0)
+                r = setsockopt_int(s, IPPROTO_IP, IP_TOS, ip_service_type);
+        else
+                r = setsockopt_int(s, IPPROTO_IP, IP_TOS, IPTOS_CLASS_CS6);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+        if (r < 0)
+                return r;
+
+        if (ifindex > 0) {
+                r = socket_bind_to_ifindex(s, ifindex);
+                if (r < 0)
+                        return r;
+        }
+
+        if (port == DHCP_PORT_SERVER) {
+                r = setsockopt_int(s, SOL_SOCKET, SO_BROADCAST, true);
+                if (r < 0)
+                        return r;
+                if (address == INADDR_ANY) {
+                        /* IP_PKTINFO filter should not be applied when packets are
+                           allowed to enter/leave through the interface other than
+                           DHCP server sits on(BindToInterface option). */
+                        r = setsockopt_int(s, IPPROTO_IP, IP_PKTINFO, true);
+                        if (r < 0)
+                                return r;
+                }
+        } else {
+                r = setsockopt_int(s, IPPROTO_IP, IP_FREEBIND, true);
+                if (r < 0)
+                        return r;
+        }
+
+        if (bind(s, &src.sa, sizeof(src.in)) < 0)
+                return -errno;
+
+        return TAKE_FD(s);
+}
+
+int dhcp_network_send_raw_socket(
+                int s,
+                const union sockaddr_union *link,
+                const void *packet,
+                size_t len) {
+
+        /* Do not add assert(s >= 0) here, as this is called in fuzz-dhcp-server, and in that case this
+         * function should fail with negative errno. */
+
+        assert(link);
+        assert(packet);
+        assert(len > 0);
+
+        if (sendto(s, packet, len, 0, &link->sa, SOCKADDR_LL_LEN(link->ll)) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int dhcp_network_send_udp_socket(
+                int s,
+                be32_t address,
+                uint16_t port,
+                const void *packet,
+                size_t len) {
+
+        union sockaddr_union dest = {
+                .in.sin_family = AF_INET,
+                .in.sin_port = htobe16(port),
+                .in.sin_addr.s_addr = address,
+        };
+
+        assert(s >= 0);
+        assert(packet);
+        assert(len > 0);
+
+        if (sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in)) < 0)
+                return -errno;
+
+        return 0;
+}
diff --git a/src/libsystemd-network/dhcp-option.c b/src/libsystemd-network/dhcp-option.c
new file mode 100644
index 0000000..7f49da7
--- /dev/null
+++ b/src/libsystemd-network/dhcp-option.c
@@ -0,0 +1,438 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+
+#include "alloc-util.h"
+#include "dhcp-internal.h"
+#include "dhcp-server-internal.h"
+#include "memory-util.h"
+#include "strv.h"
+#include "utf8.h"
+
+/* Append type-length value structure to the options buffer */
+static int dhcp_option_append_tlv(uint8_t options[], size_t size, size_t *offset, uint8_t code, size_t optlen, const void *optval) {
+        assert(options);
+        assert(size > 0);
+        assert(offset);
+        assert(optlen <= UINT8_MAX);
+        assert(*offset < size);
+
+        if (*offset + 2 + optlen > size)
+                return -ENOBUFS;
+
+        options[*offset] = code;
+        options[*offset + 1] = optlen;
+
+        memcpy_safe(&options[*offset + 2], optval, optlen);
+        *offset += 2 + optlen;
+        return 0;
+}
+
+static int option_append(uint8_t options[], size_t size, size_t *offset,
+                         uint8_t code, size_t optlen, const void *optval) {
+        assert(options);
+        assert(size > 0);
+        assert(offset);
+
+        int r;
+
+        if (code != SD_DHCP_OPTION_END)
+                /* always make sure there is space for an END option */
+                size--;
+
+        switch (code) {
+
+        case SD_DHCP_OPTION_PAD:
+        case SD_DHCP_OPTION_END:
+                if (*offset + 1 > size)
+                        return -ENOBUFS;
+
+                options[*offset] = code;
+                *offset += 1;
+                break;
+
+        case SD_DHCP_OPTION_USER_CLASS: {
+                size_t total = 0;
+
+                if (strv_isempty((char **) optval))
+                        return -EINVAL;
+
+                STRV_FOREACH(s, (const char* const*) optval) {
+                        size_t len = strlen(*s);
+
+                        if (len > 255 || len == 0)
+                                return -EINVAL;
+
+                        total += 1 + len;
+                }
+
+                if (*offset + 2 + total > size)
+                        return -ENOBUFS;
+
+                options[*offset] = code;
+                options[*offset + 1] = total;
+                *offset += 2;
+
+                STRV_FOREACH(s, (const char* const*) optval) {
+                        size_t len = strlen(*s);
+
+                        options[*offset] = len;
+                        memcpy(&options[*offset + 1], *s, len);
+                        *offset += 1 + len;
+                }
+
+                break;
+        }
+        case SD_DHCP_OPTION_SIP_SERVER:
+                if (*offset + 3 + optlen > size)
+                        return -ENOBUFS;
+
+                options[*offset] = code;
+                options[*offset + 1] = optlen + 1;
+                options[*offset + 2] = 1;
+
+                memcpy_safe(&options[*offset + 3], optval, optlen);
+                *offset += 3 + optlen;
+
+                break;
+        case SD_DHCP_OPTION_VENDOR_SPECIFIC: {
+                OrderedSet *s = (OrderedSet *) optval;
+                struct sd_dhcp_option *p;
+                size_t l = 0;
+
+                ORDERED_SET_FOREACH(p, s)
+                        l += p->length + 2;
+
+                if (*offset + l + 2 > size)
+                        return -ENOBUFS;
+
+                options[*offset] = code;
+                options[*offset + 1] = l;
+                *offset += 2;
+
+                ORDERED_SET_FOREACH(p, s) {
+                        r = dhcp_option_append_tlv(options, size, offset, p->option, p->length, p->data);
+                        if (r < 0)
+                                return r;
+                }
+                break;
+        }
+        case SD_DHCP_OPTION_RELAY_AGENT_INFORMATION: {
+                sd_dhcp_server *server = (sd_dhcp_server *) optval;
+                size_t current_offset = *offset + 2;
+
+                if (server->agent_circuit_id) {
+                        r = dhcp_option_append_tlv(options, size, &current_offset, SD_DHCP_RELAY_AGENT_CIRCUIT_ID,
+                                                   strlen(server->agent_circuit_id), server->agent_circuit_id);
+                        if (r < 0)
+                                return r;
+                }
+                if (server->agent_remote_id) {
+                        r = dhcp_option_append_tlv(options, size, &current_offset, SD_DHCP_RELAY_AGENT_REMOTE_ID,
+                                                   strlen(server->agent_remote_id), server->agent_remote_id);
+                        if (r < 0)
+                                return r;
+                }
+
+                options[*offset] = code;
+                options[*offset + 1] = current_offset - *offset - 2;
+                assert(current_offset - *offset - 2 <= UINT8_MAX);
+                *offset = current_offset;
+                break;
+        }
+        default:
+                return dhcp_option_append_tlv(options, size, offset, code, optlen, optval);
+        }
+        return 0;
+}
+
+static int option_length(uint8_t *options, size_t length, size_t offset) {
+        assert(options);
+        assert(offset < length);
+
+        if (IN_SET(options[offset], SD_DHCP_OPTION_PAD, SD_DHCP_OPTION_END))
+                return 1;
+        if (length < offset + 2)
+                return -ENOBUFS;
+
+        /* validating that buffer is long enough */
+        if (length < offset + 2 + options[offset + 1])
+                return -ENOBUFS;
+
+        return options[offset + 1] + 2;
+}
+
+int dhcp_option_find_option(uint8_t *options, size_t length, uint8_t code, size_t *ret_offset) {
+        int r;
+
+        assert(options);
+        assert(ret_offset);
+
+        for (size_t offset = 0; offset < length; offset += r) {
+                r = option_length(options, length, offset);
+                if (r < 0)
+                        return r;
+
+                if (code == options[offset]) {
+                        *ret_offset = offset;
+                        return r;
+                }
+        }
+        return -ENOENT;
+}
+
+int dhcp_option_remove_option(uint8_t *options, size_t length, uint8_t option_code) {
+        int r;
+        size_t offset;
+
+        assert(options);
+
+        r = dhcp_option_find_option(options, length, option_code, &offset);
+        if (r < 0)
+                return r;
+
+        memmove(options + offset, options + offset + r, length - offset - r);
+        return length - r;
+}
+
+int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset,
+                       uint8_t overload,
+                       uint8_t code, size_t optlen, const void *optval) {
+        const bool use_file = overload & DHCP_OVERLOAD_FILE;
+        const bool use_sname = overload & DHCP_OVERLOAD_SNAME;
+        int r;
+
+        assert(message);
+        assert(offset);
+
+        /* If *offset is in range [0, size), we are writing to ->options,
+         * if *offset is in range [size, size + sizeof(message->file)) and use_file, we are writing to ->file,
+         * if *offset is in range [size + use_file*sizeof(message->file), size + use_file*sizeof(message->file) + sizeof(message->sname))
+         * and use_sname, we are writing to ->sname.
+         */
+
+        if (*offset < size) {
+                /* still space in the options array */
+                r = option_append(message->options, size, offset, code, optlen, optval);
+                if (r >= 0)
+                        return 0;
+                else if (r == -ENOBUFS && (use_file || use_sname)) {
+                        /* did not fit, but we have more buffers to try
+                           close the options array and move the offset to its end */
+                        r = option_append(message->options, size, offset, SD_DHCP_OPTION_END, 0, NULL);
+                        if (r < 0)
+                                return r;
+
+                        *offset = size;
+                } else
+                        return r;
+        }
+
+        if (use_file) {
+                size_t file_offset = *offset - size;
+
+                if (file_offset < sizeof(message->file)) {
+                        /* still space in the 'file' array */
+                        r = option_append(message->file, sizeof(message->file), &file_offset, code, optlen, optval);
+                        if (r >= 0) {
+                                *offset = size + file_offset;
+                                return 0;
+                        } else if (r == -ENOBUFS && use_sname) {
+                                /* did not fit, but we have more buffers to try
+                                   close the file array and move the offset to its end */
+                                r = option_append(message->file, sizeof(message->file), &file_offset, SD_DHCP_OPTION_END, 0, NULL);
+                                if (r < 0)
+                                        return r;
+
+                                *offset = size + sizeof(message->file);
+                        } else
+                                return r;
+                }
+        }
+
+        if (use_sname) {
+                size_t sname_offset = *offset - size - use_file*sizeof(message->file);
+
+                if (sname_offset < sizeof(message->sname)) {
+                        /* still space in the 'sname' array */
+                        r = option_append(message->sname, sizeof(message->sname), &sname_offset, code, optlen, optval);
+                        if (r >= 0) {
+                                *offset = size + use_file*sizeof(message->file) + sname_offset;
+                                return 0;
+                        } else
+                                /* no space, or other error, give up */
+                                return r;
+                }
+        }
+
+        return -ENOBUFS;
+}
+
+static int parse_options(const uint8_t options[], size_t buflen, uint8_t *overload,
+                         uint8_t *message_type, char **error_message, dhcp_option_callback_t cb,
+                         void *userdata) {
+        uint8_t code, len;
+        const uint8_t *option;
+        size_t offset = 0;
+
+        while (offset < buflen) {
+                code = options[offset ++];
+
+                switch (code) {
+                case SD_DHCP_OPTION_PAD:
+                        continue;
+
+                case SD_DHCP_OPTION_END:
+                        return 0;
+                }
+
+                if (buflen < offset + 1)
+                        return -ENOBUFS;
+
+                len = options[offset ++];
+
+                if (buflen < offset + len)
+                        return -EINVAL;
+
+                option = &options[offset];
+
+                switch (code) {
+                case SD_DHCP_OPTION_MESSAGE_TYPE:
+                        if (len != 1)
+                                return -EINVAL;
+
+                        if (message_type)
+                                *message_type = *option;
+
+                        break;
+
+                case SD_DHCP_OPTION_ERROR_MESSAGE:
+                        if (len == 0)
+                                return -EINVAL;
+
+                        if (error_message) {
+                                _cleanup_free_ char *string = NULL;
+
+                                /* Accept a trailing NUL byte */
+                                if (memchr(option, 0, len - 1))
+                                        return -EINVAL;
+
+                                string = memdup_suffix0((const char *) option, len);
+                                if (!string)
+                                        return -ENOMEM;
+
+                                if (!ascii_is_valid(string))
+                                        return -EINVAL;
+
+                                free_and_replace(*error_message, string);
+                        }
+
+                        break;
+                case SD_DHCP_OPTION_OVERLOAD:
+                        if (len != 1)
+                                return -EINVAL;
+
+                        if (overload)
+                                *overload = *option;
+
+                        break;
+
+                default:
+                        if (cb)
+                                cb(code, len, option, userdata);
+
+                        break;
+                }
+
+                offset += len;
+        }
+
+        if (offset < buflen)
+                return -EINVAL;
+
+        return 0;
+}
+
+int dhcp_option_parse(DHCPMessage *message, size_t len, dhcp_option_callback_t cb, void *userdata, char **_error_message) {
+        _cleanup_free_ char *error_message = NULL;
+        uint8_t overload = 0;
+        uint8_t message_type = 0;
+        int r;
+
+        if (!message)
+                return -EINVAL;
+
+        if (len < sizeof(DHCPMessage))
+                return -EINVAL;
+
+        len -= sizeof(DHCPMessage);
+
+        r = parse_options(message->options, len, &overload, &message_type, &error_message, cb, userdata);
+        if (r < 0)
+                return r;
+
+        if (overload & DHCP_OVERLOAD_FILE) {
+                r = parse_options(message->file, sizeof(message->file), NULL, &message_type, &error_message, cb, userdata);
+                if (r < 0)
+                        return r;
+        }
+
+        if (overload & DHCP_OVERLOAD_SNAME) {
+                r = parse_options(message->sname, sizeof(message->sname), NULL, &message_type, &error_message, cb, userdata);
+                if (r < 0)
+                        return r;
+        }
+
+        if (message_type == 0)
+                return -ENOMSG;
+
+        if (_error_message && IN_SET(message_type, DHCP_NAK, DHCP_DECLINE))
+                *_error_message = TAKE_PTR(error_message);
+
+        return message_type;
+}
+
+static sd_dhcp_option* dhcp_option_free(sd_dhcp_option *i) {
+        if (!i)
+                return NULL;
+
+        free(i->data);
+        return mfree(i);
+}
+
+int sd_dhcp_option_new(uint8_t option, const void *data, size_t length, sd_dhcp_option **ret) {
+        assert_return(ret, -EINVAL);
+        assert_return(length == 0 || data, -EINVAL);
+
+        _cleanup_free_ void *q = memdup(data, length);
+        if (!q)
+                return -ENOMEM;
+
+        sd_dhcp_option *p = new(sd_dhcp_option, 1);
+        if (!p)
+                return -ENOMEM;
+
+        *p = (sd_dhcp_option) {
+                .n_ref = 1,
+                .option = option,
+                .length = length,
+                .data = TAKE_PTR(q),
+        };
+
+        *ret = TAKE_PTR(p);
+        return 0;
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp_option, sd_dhcp_option, dhcp_option_free);
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+                dhcp_option_hash_ops,
+                void,
+                trivial_hash_func,
+                trivial_compare_func,
+                sd_dhcp_option,
+                sd_dhcp_option_unref);
diff --git a/src/libsystemd-network/dhcp-packet.c b/src/libsystemd-network/dhcp-packet.c
new file mode 100644
index 0000000..b2efd52
--- /dev/null
+++ b/src/libsystemd-network/dhcp-packet.c
@@ -0,0 +1,191 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <net/ethernet.h>
+#include <net/if_arp.h>
+#include <string.h>
+
+#include "dhcp-internal.h"
+#include "dhcp-protocol.h"
+#include "memory-util.h"
+
+#define DHCP_CLIENT_MIN_OPTIONS_SIZE            312
+
+int dhcp_message_init(
+                DHCPMessage *message,
+                uint8_t op,
+                uint32_t xid,
+                uint8_t type,
+                uint16_t arp_type,
+                uint8_t hlen,
+                const uint8_t *chaddr,
+                size_t optlen,
+                size_t *optoffset) {
+
+        size_t offset = 0;
+        int r;
+
+        assert(IN_SET(op, BOOTREQUEST, BOOTREPLY));
+        assert(chaddr || hlen == 0);
+
+        message->op = op;
+        message->htype = arp_type;
+
+        /* RFC2131 section 4.1.1:
+           The client MUST include its hardware address in the ’chaddr’ field, if
+           necessary for delivery of DHCP reply messages.
+
+           RFC 4390 section 2.1:
+           A DHCP client, when working over an IPoIB interface, MUST follow the
+           following rules:
+           "htype" (hardware address type) MUST be 32 [ARPPARAM].
+           "hlen" (hardware address length) MUST be 0.
+           "chaddr" (client hardware address) field MUST be zeroed.
+         */
+        message->hlen = arp_type == ARPHRD_INFINIBAND ? 0 : hlen;
+        memcpy_safe(message->chaddr, chaddr, message->hlen);
+
+        message->xid = htobe32(xid);
+        message->magic = htobe32(DHCP_MAGIC_COOKIE);
+
+        r = dhcp_option_append(message, optlen, &offset, 0,
+                               SD_DHCP_OPTION_MESSAGE_TYPE, 1, &type);
+        if (r < 0)
+                return r;
+
+        *optoffset = offset;
+
+        return 0;
+}
+
+uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) {
+        uint64_t *buf_64 = (uint64_t*)buf;
+        uint64_t *end_64 = buf_64 + (len / sizeof(uint64_t));
+        uint64_t sum = 0;
+
+        /* See RFC1071 */
+
+        while (buf_64 < end_64) {
+                sum += *buf_64;
+                if (sum < *buf_64)
+                        /* wrap around in one's complement */
+                        sum++;
+
+                buf_64++;
+        }
+
+        if (len % sizeof(uint64_t)) {
+                /* If the buffer is not aligned to 64-bit, we need
+                   to zero-pad the last few bytes and add them in */
+                uint64_t buf_tail = 0;
+
+                memcpy(&buf_tail, buf_64, len % sizeof(uint64_t));
+
+                sum += buf_tail;
+                if (sum < buf_tail)
+                        /* wrap around */
+                        sum++;
+        }
+
+        while (sum >> 16)
+                sum = (sum & 0xffff) + (sum >> 16);
+
+        return ~sum;
+}
+
+void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
+                                   uint16_t source_port, be32_t destination_addr,
+                                   uint16_t destination_port, uint16_t len, int ip_service_type) {
+        packet->ip.version = IPVERSION;
+        packet->ip.ihl = DHCP_IP_SIZE / 4;
+        packet->ip.tot_len = htobe16(len);
+
+        if (ip_service_type >= 0)
+                packet->ip.tos = ip_service_type;
+        else
+                packet->ip.tos = IPTOS_CLASS_CS6;
+
+        packet->ip.protocol = IPPROTO_UDP;
+        packet->ip.saddr = source_addr;
+        packet->ip.daddr = destination_addr;
+
+        packet->udp.source = htobe16(source_port);
+        packet->udp.dest = htobe16(destination_port);
+
+        packet->udp.len = htobe16(len - DHCP_IP_SIZE);
+
+        packet->ip.check = packet->udp.len;
+        packet->udp.check = dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, len - 8);
+
+        packet->ip.ttl = IPDEFTTL;
+        packet->ip.check = 0;
+        packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE);
+}
+
+int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port) {
+        size_t hdrlen;
+
+        assert(packet);
+        assert(len >= sizeof(DHCPPacket));
+
+        /* IP */
+
+        if (packet->ip.version != IPVERSION)
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: not IPv4");
+
+        if (packet->ip.ihl < 5)
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: IPv4 IHL (%i words) invalid",
+                                       packet->ip.ihl);
+
+        hdrlen = packet->ip.ihl * 4;
+        if (hdrlen < 20)
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: IPv4 IHL (%zu bytes) smaller than minimum (20 bytes)",
+                                       hdrlen);
+
+        if (len < hdrlen)
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: packet (%zu bytes) smaller than expected (%zu) by IP header",
+                                       len, hdrlen);
+
+        /* UDP */
+
+        if (packet->ip.protocol != IPPROTO_UDP)
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: not UDP");
+
+        if (len < hdrlen + be16toh(packet->udp.len))
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: packet (%zu bytes) smaller than expected (%zu) by UDP header",
+                                       len, hdrlen + be16toh(packet->udp.len));
+
+        if (be16toh(packet->udp.dest) != port)
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: to port %u, which is not the DHCP client port (%u)",
+                                       be16toh(packet->udp.dest), port);
+
+        /* checksums - computing these is relatively expensive, so only do it
+           if all the other checks have passed
+         */
+
+        if (dhcp_packet_checksum((uint8_t*)&packet->ip, hdrlen))
+                return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "ignoring packet: invalid IP checksum");
+
+        if (checksum && packet->udp.check) {
+                packet->ip.check = packet->udp.len;
+                packet->ip.ttl = 0;
+
+                if (dhcp_packet_checksum((uint8_t*)&packet->ip.ttl,
+                                  be16toh(packet->udp.len) + 12))
+                        return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
+                                               "ignoring packet: invalid UDP checksum");
+        }
+
+        return 0;
+}
diff --git a/src/libsystemd-network/dhcp-protocol.h b/src/libsystemd-network/dhcp-protocol.h
new file mode 100644
index 0000000..c4972d1
--- /dev/null
+++ b/src/libsystemd-network/dhcp-protocol.h
@@ -0,0 +1,109 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <netinet/ip.h>
+#include <netinet/udp.h>
+#include <stdint.h>
+
+#include "macro.h"
+#include "sparse-endian.h"
+
+struct DHCPMessage {
+        uint8_t op;
+        uint8_t htype;
+        uint8_t hlen;
+        uint8_t hops;
+        be32_t xid;
+        be16_t secs;
+        be16_t flags;
+        be32_t ciaddr;
+        be32_t yiaddr;
+        be32_t siaddr;
+        be32_t giaddr;
+        uint8_t chaddr[16];
+        uint8_t sname[64];
+        uint8_t file[128];
+        be32_t magic;
+        uint8_t options[0];
+} _packed_;
+
+typedef struct DHCPMessage DHCPMessage;
+
+struct DHCPPacket {
+        struct iphdr ip;
+        struct udphdr udp;
+        DHCPMessage dhcp;
+} _packed_;
+
+typedef struct DHCPPacket DHCPPacket;
+
+#define DHCP_IP_SIZE            (int32_t)(sizeof(struct iphdr))
+#define DHCP_IP_UDP_SIZE        (int32_t)(sizeof(struct udphdr) + DHCP_IP_SIZE)
+#define DHCP_HEADER_SIZE        (int32_t)(sizeof(DHCPMessage))
+#define DHCP_MIN_MESSAGE_SIZE   576 /* the minimum internet hosts must be able to receive, see RFC 2132 Section 9.10 */
+#define DHCP_MIN_OPTIONS_SIZE   (DHCP_MIN_MESSAGE_SIZE - DHCP_HEADER_SIZE)
+#define DHCP_MIN_PACKET_SIZE    (DHCP_MIN_MESSAGE_SIZE + DHCP_IP_UDP_SIZE)
+#define DHCP_MAGIC_COOKIE       (uint32_t)(0x63825363)
+
+enum {
+        DHCP_PORT_SERVER                        = 67,
+        DHCP_PORT_CLIENT                        = 68,
+};
+
+enum DHCPState {
+        DHCP_STATE_INIT                         = 0,
+        DHCP_STATE_SELECTING                    = 1,
+        DHCP_STATE_INIT_REBOOT                  = 2,
+        DHCP_STATE_REBOOTING                    = 3,
+        DHCP_STATE_REQUESTING                   = 4,
+        DHCP_STATE_BOUND                        = 5,
+        DHCP_STATE_RENEWING                     = 6,
+        DHCP_STATE_REBINDING                    = 7,
+        DHCP_STATE_STOPPED                      = 8,
+};
+
+typedef enum DHCPState DHCPState;
+
+enum {
+        BOOTREQUEST                             = 1,
+        BOOTREPLY                               = 2,
+};
+
+enum {
+        DHCP_DISCOVER                           = 1,  /* [RFC2132] */
+        DHCP_OFFER                              = 2,  /* [RFC2132] */
+        DHCP_REQUEST                            = 3,  /* [RFC2132] */
+        DHCP_DECLINE                            = 4,  /* [RFC2132] */
+        DHCP_ACK                                = 5,  /* [RFC2132] */
+        DHCP_NAK                                = 6,  /* [RFC2132] */
+        DHCP_RELEASE                            = 7,  /* [RFC2132] */
+        DHCP_INFORM                             = 8,  /* [RFC2132] */
+        DHCP_FORCERENEW                         = 9,  /* [RFC3203] */
+        DHCPLEASEQUERY                          = 10, /* [RFC4388] */
+        DHCPLEASEUNASSIGNED                     = 11, /* [RFC4388] */
+        DHCPLEASEUNKNOWN                        = 12, /* [RFC4388] */
+        DHCPLEASEACTIVE                         = 13, /* [RFC4388] */
+        DHCPBULKLEASEQUERY                      = 14, /* [RFC6926] */
+        DHCPLEASEQUERYDONE                      = 15, /* [RFC6926] */
+        DHCPACTIVELEASEQUERY                    = 16, /* [RFC7724] */
+        DHCPLEASEQUERYSTATUS                    = 17, /* [RFC7724] */
+        DHCPTLS                                 = 18, /* [RFC7724] */
+};
+
+enum {
+        DHCP_OVERLOAD_FILE                      = 1,
+        DHCP_OVERLOAD_SNAME                     = 2,
+};
+
+#define DHCP_MAX_FQDN_LENGTH 255
+
+enum {
+        DHCP_FQDN_FLAG_S = (1 << 0),
+        DHCP_FQDN_FLAG_O = (1 << 1),
+        DHCP_FQDN_FLAG_E = (1 << 2),
+        DHCP_FQDN_FLAG_N = (1 << 3),
+};
diff --git a/src/libsystemd-network/dhcp-server-internal.h b/src/libsystemd-network/dhcp-server-internal.h
new file mode 100644
index 0000000..466d454
--- /dev/null
+++ b/src/libsystemd-network/dhcp-server-internal.h
@@ -0,0 +1,130 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include "sd-dhcp-server.h"
+#include "sd-event.h"
+
+#include "dhcp-internal.h"
+#include "network-common.h"
+#include "ordered-set.h"
+#include "time-util.h"
+
+typedef enum DHCPRawOption {
+        DHCP_RAW_OPTION_DATA_UINT8,
+        DHCP_RAW_OPTION_DATA_UINT16,
+        DHCP_RAW_OPTION_DATA_UINT32,
+        DHCP_RAW_OPTION_DATA_STRING,
+        DHCP_RAW_OPTION_DATA_IPV4ADDRESS,
+        DHCP_RAW_OPTION_DATA_IPV6ADDRESS,
+        _DHCP_RAW_OPTION_DATA_MAX,
+        _DHCP_RAW_OPTION_DATA_INVALID,
+} DHCPRawOption;
+
+typedef struct DHCPClientId {
+        size_t length;
+        uint8_t *data;
+} DHCPClientId;
+
+typedef struct DHCPLease {
+        sd_dhcp_server *server;
+
+        DHCPClientId client_id;
+
+        uint8_t htype; /* e.g. ARPHRD_ETHER */
+        uint8_t hlen;  /* e.g. ETH_ALEN */
+        be32_t address;
+        be32_t gateway;
+        uint8_t chaddr[16];
+        usec_t expiration;
+} DHCPLease;
+
+struct sd_dhcp_server {
+        unsigned n_ref;
+
+        sd_event *event;
+        int event_priority;
+        sd_event_source *receive_message;
+        sd_event_source *receive_broadcast;
+        int fd;
+        int fd_raw;
+        int fd_broadcast;
+
+        int ifindex;
+        char *ifname;
+        bool bind_to_interface;
+        be32_t address;
+        be32_t netmask;
+        be32_t subnet;
+        uint32_t pool_offset;
+        uint32_t pool_size;
+
+        char *timezone;
+
+        DHCPServerData servers[_SD_DHCP_LEASE_SERVER_TYPE_MAX];
+        struct in_addr boot_server_address;
+        char *boot_server_name;
+        char *boot_filename;
+
+        OrderedSet *extra_options;
+        OrderedSet *vendor_options;
+
+        bool emit_router;
+        struct in_addr router_address;
+
+        Hashmap *bound_leases_by_client_id;
+        Hashmap *bound_leases_by_address;
+        Hashmap *static_leases_by_client_id;
+        Hashmap *static_leases_by_address;
+
+        uint32_t max_lease_time, default_lease_time;
+
+        sd_dhcp_server_callback_t callback;
+        void *callback_userdata;
+
+        struct in_addr relay_target;
+
+        char *agent_circuit_id;
+        char *agent_remote_id;
+};
+
+typedef struct DHCPRequest {
+        /* received message */
+        DHCPMessage *message;
+
+        /* options */
+        DHCPClientId client_id;
+        size_t max_optlen;
+        be32_t server_id;
+        be32_t requested_ip;
+        uint32_t lifetime;
+        const uint8_t *agent_info_option;
+} DHCPRequest;
+
+extern const struct hash_ops dhcp_lease_hash_ops;
+
+int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message,
+                               size_t length);
+int dhcp_server_send_packet(sd_dhcp_server *server,
+                            DHCPRequest *req, DHCPPacket *packet,
+                            int type, size_t optoffset);
+
+void client_id_hash_func(const DHCPClientId *p, struct siphash *state);
+int client_id_compare_func(const DHCPClientId *a, const DHCPClientId *b);
+
+DHCPLease *dhcp_lease_free(DHCPLease *lease);
+DEFINE_TRIVIAL_CLEANUP_FUNC(DHCPLease*, dhcp_lease_free);
+
+#define log_dhcp_server_errno(server, error, fmt, ...)          \
+        log_interface_prefix_full_errno(                        \
+                "DHCPv4 server: ",                              \
+                sd_dhcp_server, server,                         \
+                error, fmt, ##__VA_ARGS__)
+#define log_dhcp_server(server, fmt, ...)                       \
+        log_interface_prefix_full_errno_zerook(                 \
+                "DHCPv4 server: ",                              \
+                sd_dhcp_server, server,                         \
+                0, fmt, ##__VA_ARGS__)
diff --git a/src/libsystemd-network/dhcp6-internal.h b/src/libsystemd-network/dhcp6-internal.h
new file mode 100644
index 0000000..65f6cb0
--- /dev/null
+++ b/src/libsystemd-network/dhcp6-internal.h
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2014-2015 Intel Corporation. All rights reserved.
+***/
+
+#include <net/ethernet.h>
+#include <netinet/in.h>
+
+#include "sd-event.h"
+#include "sd-dhcp6-client.h"
+
+#include "dhcp-identifier.h"
+#include "dhcp6-option.h"
+#include "dhcp6-protocol.h"
+#include "ether-addr-util.h"
+#include "hashmap.h"
+#include "macro.h"
+#include "network-common.h"
+#include "ordered-set.h"
+#include "sparse-endian.h"
+#include "time-util.h"
+
+/* what to request from the server, addresses (IA_NA) and/or prefixes (IA_PD) */
+typedef enum DHCP6RequestIA {
+        DHCP6_REQUEST_IA_NA = 1 << 0,
+        DHCP6_REQUEST_IA_TA = 1 << 1, /* currently not used */
+        DHCP6_REQUEST_IA_PD = 1 << 2,
+} DHCP6RequestIA;
+
+struct sd_dhcp6_client {
+        unsigned n_ref;
+
+        int ifindex;
+        char *ifname;
+
+        struct in6_addr local_address;
+        struct hw_addr_data hw_addr;
+        uint16_t arp_type;
+
+        sd_event *event;
+        sd_event_source *receive_message;
+        sd_event_source *timeout_resend;
+        sd_event_source *timeout_expire;
+        sd_event_source *timeout_t1;
+        sd_event_source *timeout_t2;
+        int event_priority;
+        int fd;
+
+        DHCP6State state;
+        bool information_request;
+        usec_t information_request_time_usec;
+        usec_t information_refresh_time_usec;
+        be32_t transaction_id;
+        usec_t transaction_start;
+        usec_t retransmit_time;
+        uint8_t retransmit_count;
+
+        bool iaid_set;
+        DHCP6IA ia_na;
+        DHCP6IA ia_pd;
+        DHCP6RequestIA request_ia;
+        struct duid duid;
+        size_t duid_len;
+        be16_t *req_opts;
+        size_t n_req_opts;
+        char *fqdn;
+        char *mudurl;
+        char **user_class;
+        char **vendor_class;
+        OrderedHashmap *extra_options;
+        OrderedSet *vendor_options;
+        bool rapid_commit;
+
+        struct sd_dhcp6_lease *lease;
+
+        sd_dhcp6_client_callback_t callback;
+        void *userdata;
+
+        /* Ignore ifindex when generating iaid. See dhcp_identifier_set_iaid(). */
+        bool test_mode;
+};
+
+int dhcp6_network_bind_udp_socket(int ifindex, struct in6_addr *address);
+int dhcp6_network_send_udp_socket(int s, struct in6_addr *address,
+                                  const void *packet, size_t len);
+
+int dhcp6_client_send_message(sd_dhcp6_client *client);
+void dhcp6_client_set_test_mode(sd_dhcp6_client *client, bool test_mode);
+int dhcp6_client_set_transaction_id(sd_dhcp6_client *client, uint32_t transaction_id);
+
+#define log_dhcp6_client_errno(client, error, fmt, ...)         \
+        log_interface_prefix_full_errno(                        \
+                "DHCPv6 client: ",                              \
+                sd_dhcp6_client, client,                        \
+                error, fmt, ##__VA_ARGS__)
+#define log_dhcp6_client(client, fmt, ...)                      \
+        log_interface_prefix_full_errno_zerook(                 \
+                "DHCPv6 client: ",                              \
+                sd_dhcp6_client, client,                        \
+                0, fmt, ##__VA_ARGS__)
diff --git a/src/libsystemd-network/dhcp6-lease-internal.h b/src/libsystemd-network/dhcp6-lease-internal.h
new file mode 100644
index 0000000..1f10dcc
--- /dev/null
+++ b/src/libsystemd-network/dhcp6-lease-internal.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2014-2015 Intel Corporation. All rights reserved.
+***/
+
+#include <inttypes.h>
+
+#include "sd-dhcp6-lease.h"
+
+#include "dhcp6-option.h"
+#include "macro.h"
+#include "time-util.h"
+
+struct sd_dhcp6_lease {
+        unsigned n_ref;
+
+        uint8_t *clientid;
+        size_t clientid_len;
+        uint8_t *serverid;
+        size_t serverid_len;
+        uint8_t preference;
+        bool rapid_commit;
+        triple_timestamp timestamp;
+        usec_t lifetime_t1;
+        usec_t lifetime_t2;
+        usec_t lifetime_valid;
+        struct in6_addr server_address;
+
+        DHCP6IA *ia_na; /* Identity association non-temporary addresses */
+        DHCP6IA *ia_pd; /* Identity association prefix delegation */
+
+        DHCP6Address *addr_iter;
+        DHCP6Address *prefix_iter;
+
+        struct in6_addr *dns;
+        size_t dns_count;
+        char **domains;
+        struct in6_addr *ntp;
+        size_t ntp_count;
+        char **ntp_fqdn;
+        struct in6_addr *sntp;
+        size_t sntp_count;
+        char *fqdn;
+};
+
+int dhcp6_lease_get_lifetime(sd_dhcp6_lease *lease, usec_t *ret_t1, usec_t *ret_t2, usec_t *ret_valid);
+int dhcp6_lease_set_clientid(sd_dhcp6_lease *lease, const uint8_t *id, size_t len);
+int dhcp6_lease_get_clientid(sd_dhcp6_lease *lease, uint8_t **ret_id, size_t *ret_len);
+int dhcp6_lease_set_serverid(sd_dhcp6_lease *lease, const uint8_t *id, size_t len);
+int dhcp6_lease_get_serverid(sd_dhcp6_lease *lease, uint8_t **ret_id, size_t *ret_len);
+int dhcp6_lease_set_preference(sd_dhcp6_lease *lease, uint8_t preference);
+int dhcp6_lease_get_preference(sd_dhcp6_lease *lease, uint8_t *ret);
+int dhcp6_lease_set_rapid_commit(sd_dhcp6_lease *lease);
+int dhcp6_lease_get_rapid_commit(sd_dhcp6_lease *lease, bool *ret);
+
+int dhcp6_lease_add_dns(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen);
+int dhcp6_lease_add_domains(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen);
+int dhcp6_lease_add_ntp(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen);
+int dhcp6_lease_add_sntp(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen);
+int dhcp6_lease_set_fqdn(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen);
+
+int dhcp6_lease_new(sd_dhcp6_lease **ret);
+int dhcp6_lease_new_from_message(
+                sd_dhcp6_client *client,
+                const DHCP6Message *message,
+                size_t len,
+                const triple_timestamp *timestamp,
+                const struct in6_addr *server_address,
+                sd_dhcp6_lease **ret);
diff --git a/src/libsystemd-network/dhcp6-network.c b/src/libsystemd-network/dhcp6-network.c
new file mode 100644
index 0000000..eedd92d
--- /dev/null
+++ b/src/libsystemd-network/dhcp6-network.c
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <netinet/in.h>
+#include <netinet/ip6.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <linux/if_packet.h>
+
+#include "dhcp6-internal.h"
+#include "dhcp6-protocol.h"
+#include "fd-util.h"
+#include "socket-util.h"
+
+int dhcp6_network_bind_udp_socket(int ifindex, struct in6_addr *local_address) {
+        union sockaddr_union src = {
+                .in6.sin6_family = AF_INET6,
+                .in6.sin6_port = htobe16(DHCP6_PORT_CLIENT),
+                .in6.sin6_scope_id = ifindex,
+        };
+        _cleanup_close_ int s = -1;
+        int r;
+
+        assert(ifindex > 0);
+        assert(local_address);
+
+        src.in6.sin6_addr = *local_address;
+
+        s = socket(AF_INET6, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, IPPROTO_UDP);
+        if (s < 0)
+                return -errno;
+
+        r = setsockopt_int(s, IPPROTO_IPV6, IPV6_V6ONLY, true);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, false);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, SOL_SOCKET, SO_REUSEADDR, true);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, SOL_SOCKET, SO_TIMESTAMP, true);
+        if (r < 0)
+                return r;
+
+        r = bind(s, &src.sa, sizeof(src.in6));
+        if (r < 0)
+                return -errno;
+
+        return TAKE_FD(s);
+}
+
+int dhcp6_network_send_udp_socket(int s, struct in6_addr *server_address,
+                                  const void *packet, size_t len) {
+        union sockaddr_union dest = {
+                .in6.sin6_family = AF_INET6,
+                .in6.sin6_port = htobe16(DHCP6_PORT_SERVER),
+        };
+        int r;
+
+        assert(server_address);
+
+        memcpy(&dest.in6.sin6_addr, server_address, sizeof(dest.in6.sin6_addr));
+
+        r = sendto(s, packet, len, 0, &dest.sa, sizeof(dest.in6));
+        if (r < 0)
+                return -errno;
+
+        return 0;
+}
diff --git a/src/libsystemd-network/dhcp6-option.c b/src/libsystemd-network/dhcp6-option.c
new file mode 100644
index 0000000..62873e0
--- /dev/null
+++ b/src/libsystemd-network/dhcp6-option.c
@@ -0,0 +1,948 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014-2015 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <netinet/in.h>
+
+#include "sd-dhcp6-client.h"
+
+#include "alloc-util.h"
+#include "dhcp6-internal.h"
+#include "dhcp6-option.h"
+#include "dhcp6-protocol.h"
+#include "dns-domain.h"
+#include "escape.h"
+#include "memory-util.h"
+#include "strv.h"
+#include "unaligned.h"
+
+#define DHCP6_OPTION_IA_NA_LEN (sizeof(struct ia_na))
+#define DHCP6_OPTION_IA_PD_LEN (sizeof(struct ia_pd))
+#define DHCP6_OPTION_IA_TA_LEN (sizeof(struct ia_ta))
+
+bool dhcp6_option_can_request(uint16_t option) {
+        /* See Client ORO field in
+         * https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml#dhcpv6-parameters-2 */
+
+        switch (option) {
+        case SD_DHCP6_OPTION_CLIENTID:
+        case SD_DHCP6_OPTION_SERVERID:
+        case SD_DHCP6_OPTION_IA_NA:
+        case SD_DHCP6_OPTION_IA_TA:
+        case SD_DHCP6_OPTION_IAADDR:
+        case SD_DHCP6_OPTION_ORO:
+        case SD_DHCP6_OPTION_PREFERENCE:
+        case SD_DHCP6_OPTION_ELAPSED_TIME:
+        case SD_DHCP6_OPTION_RELAY_MSG:
+        case SD_DHCP6_OPTION_AUTH:
+        case SD_DHCP6_OPTION_UNICAST:
+        case SD_DHCP6_OPTION_STATUS_CODE:
+        case SD_DHCP6_OPTION_RAPID_COMMIT:
+        case SD_DHCP6_OPTION_USER_CLASS:
+        case SD_DHCP6_OPTION_VENDOR_CLASS:
+                return false;
+        case SD_DHCP6_OPTION_VENDOR_OPTS:
+                return true;
+        case SD_DHCP6_OPTION_INTERFACE_ID:
+        case SD_DHCP6_OPTION_RECONF_MSG:
+        case SD_DHCP6_OPTION_RECONF_ACCEPT:
+                return false;
+        case SD_DHCP6_OPTION_SIP_SERVER_DOMAIN_NAME:
+        case SD_DHCP6_OPTION_SIP_SERVER_ADDRESS:
+        case SD_DHCP6_OPTION_DNS_SERVER:
+        case SD_DHCP6_OPTION_DOMAIN:
+                return true;
+        case SD_DHCP6_OPTION_IA_PD:
+        case SD_DHCP6_OPTION_IA_PD_PREFIX:
+                return false;
+        case SD_DHCP6_OPTION_NIS_SERVER:
+        case SD_DHCP6_OPTION_NISP_SERVER:
+        case SD_DHCP6_OPTION_NIS_DOMAIN_NAME:
+        case SD_DHCP6_OPTION_NISP_DOMAIN_NAME:
+        case SD_DHCP6_OPTION_SNTP_SERVER:
+                return true;
+        case SD_DHCP6_OPTION_INFORMATION_REFRESH_TIME:
+                return false; /* This is automatically set when sending INFORMATION_REQUEST message. */
+        case SD_DHCP6_OPTION_BCMCS_SERVER_D:
+        case SD_DHCP6_OPTION_BCMCS_SERVER_A:
+        case SD_DHCP6_OPTION_GEOCONF_CIVIC:
+                return true;
+        case SD_DHCP6_OPTION_REMOTE_ID:
+        case SD_DHCP6_OPTION_SUBSCRIBER_ID:
+                return false;
+        case SD_DHCP6_OPTION_CLIENT_FQDN:
+        case SD_DHCP6_OPTION_PANA_AGENT:
+        case SD_DHCP6_OPTION_POSIX_TIMEZONE:
+        case SD_DHCP6_OPTION_TZDB_TIMEZONE:
+                return true;
+        case SD_DHCP6_OPTION_ERO:
+        case SD_DHCP6_OPTION_LQ_QUERY:
+        case SD_DHCP6_OPTION_CLIENT_DATA:
+        case SD_DHCP6_OPTION_CLT_TIME:
+        case SD_DHCP6_OPTION_LQ_RELAY_DATA:
+        case SD_DHCP6_OPTION_LQ_CLIENT_LINK:
+                return false;
+        case SD_DHCP6_OPTION_MIP6_HNIDF:
+        case SD_DHCP6_OPTION_MIP6_VDINF:
+        case SD_DHCP6_OPTION_V6_LOST:
+        case SD_DHCP6_OPTION_CAPWAP_AC_V6:
+                return true;
+        case SD_DHCP6_OPTION_RELAY_ID:
+                return false;
+        case SD_DHCP6_OPTION_IPV6_ADDRESS_MOS:
+        case SD_DHCP6_OPTION_IPV6_FQDN_MOS:
+        case SD_DHCP6_OPTION_NTP_SERVER:
+        case SD_DHCP6_OPTION_V6_ACCESS_DOMAIN:
+        case SD_DHCP6_OPTION_SIP_UA_CS_LIST:
+        case SD_DHCP6_OPTION_BOOTFILE_URL:
+        case SD_DHCP6_OPTION_BOOTFILE_PARAM:
+                return true;
+        case SD_DHCP6_OPTION_CLIENT_ARCH_TYPE:
+                return false;
+        case SD_DHCP6_OPTION_NII:
+        case SD_DHCP6_OPTION_GEOLOCATION:
+        case SD_DHCP6_OPTION_AFTR_NAME:
+        case SD_DHCP6_OPTION_ERP_LOCAL_DOMAIN_NAME:
+                return true;
+        case SD_DHCP6_OPTION_RSOO:
+                return false;
+        case SD_DHCP6_OPTION_PD_EXCLUDE:
+                return true;
+        case SD_DHCP6_OPTION_VSS:
+                return false;
+        case SD_DHCP6_OPTION_MIP6_IDINF:
+        case SD_DHCP6_OPTION_MIP6_UDINF:
+        case SD_DHCP6_OPTION_MIP6_HNP:
+        case SD_DHCP6_OPTION_MIP6_HAA:
+        case SD_DHCP6_OPTION_MIP6_HAF:
+        case SD_DHCP6_OPTION_RDNSS_SELECTION:
+        case SD_DHCP6_OPTION_KRB_PRINCIPAL_NAME:
+        case SD_DHCP6_OPTION_KRB_REALM_NAME:
+        case SD_DHCP6_OPTION_KRB_DEFAULT_REALM_NAME:
+        case SD_DHCP6_OPTION_KRB_KDC:
+                return true;
+        case SD_DHCP6_OPTION_CLIENT_LINKLAYER_ADDR:
+        case SD_DHCP6_OPTION_LINK_ADDRESS:
+        case SD_DHCP6_OPTION_RADIUS:
+        case SD_DHCP6_OPTION_SOL_MAX_RT: /* Automatically set when sending SOLICIT message. */
+        case SD_DHCP6_OPTION_INF_MAX_RT: /* Automatically set when sending INFORMATION_REQUEST message. */
+                return false;
+        case SD_DHCP6_OPTION_ADDRSEL:
+        case SD_DHCP6_OPTION_ADDRSEL_TABLE:
+        case SD_DHCP6_OPTION_V6_PCP_SERVER:
+                return true;
+        case SD_DHCP6_OPTION_DHCPV4_MSG:
+                return false;
+        case SD_DHCP6_OPTION_DHCP4_O_DHCP6_SERVER:
+                return true;
+        case SD_DHCP6_OPTION_S46_RULE:
+                return false;
+        case SD_DHCP6_OPTION_S46_BR:
+                return true;
+        case SD_DHCP6_OPTION_S46_DMR:
+        case SD_DHCP6_OPTION_S46_V4V6BIND:
+        case SD_DHCP6_OPTION_S46_PORTPARAMS:
+                return false;
+        case SD_DHCP6_OPTION_S46_CONT_MAPE:
+        case SD_DHCP6_OPTION_S46_CONT_MAPT:
+        case SD_DHCP6_OPTION_S46_CONT_LW:
+        case SD_DHCP6_OPTION_4RD:
+        case SD_DHCP6_OPTION_4RD_MAP_RULE:
+        case SD_DHCP6_OPTION_4RD_NON_MAP_RULE:
+                return true;
+        case SD_DHCP6_OPTION_LQ_BASE_TIME:
+        case SD_DHCP6_OPTION_LQ_START_TIME:
+        case SD_DHCP6_OPTION_LQ_END_TIME:
+                return false;
+        case SD_DHCP6_OPTION_CAPTIVE_PORTAL:
+        case SD_DHCP6_OPTION_MPL_PARAMETERS:
+                return true;
+        case SD_DHCP6_OPTION_ANI_ATT:
+        case SD_DHCP6_OPTION_ANI_NETWORK_NAME:
+        case SD_DHCP6_OPTION_ANI_AP_NAME:
+        case SD_DHCP6_OPTION_ANI_AP_BSSID:
+        case SD_DHCP6_OPTION_ANI_OPERATOR_ID:
+        case SD_DHCP6_OPTION_ANI_OPERATOR_REALM:
+                return false;
+        case SD_DHCP6_OPTION_S46_PRIORITY:
+                return true;
+        case SD_DHCP6_OPTION_MUD_URL_V6:
+                return false;
+        case SD_DHCP6_OPTION_V6_PREFIX64:
+                return true;
+        case SD_DHCP6_OPTION_F_BINDING_STATUS:
+        case SD_DHCP6_OPTION_F_CONNECT_FLAGS:
+        case SD_DHCP6_OPTION_F_DNS_REMOVAL_INFO:
+        case SD_DHCP6_OPTION_F_DNS_HOST_NAME:
+        case SD_DHCP6_OPTION_F_DNS_ZONE_NAME:
+        case SD_DHCP6_OPTION_F_DNS_FLAGS:
+        case SD_DHCP6_OPTION_F_EXPIRATION_TIME:
+        case SD_DHCP6_OPTION_F_MAX_UNACKED_BNDUPD:
+        case SD_DHCP6_OPTION_F_MCLT:
+        case SD_DHCP6_OPTION_F_PARTNER_LIFETIME:
+        case SD_DHCP6_OPTION_F_PARTNER_LIFETIME_SENT:
+        case SD_DHCP6_OPTION_F_PARTNER_DOWN_TIME:
+        case SD_DHCP6_OPTION_F_PARTNER_RAW_CLT_TIME:
+        case SD_DHCP6_OPTION_F_PROTOCOL_VERSION:
+        case SD_DHCP6_OPTION_F_KEEPALIVE_TIME:
+        case SD_DHCP6_OPTION_F_RECONFIGURE_DATA:
+        case SD_DHCP6_OPTION_F_RELATIONSHIP_NAME:
+        case SD_DHCP6_OPTION_F_SERVER_FLAGS:
+        case SD_DHCP6_OPTION_F_SERVER_STATE:
+        case SD_DHCP6_OPTION_F_START_TIME_OF_STATE:
+        case SD_DHCP6_OPTION_F_STATE_EXPIRATION_TIME:
+        case SD_DHCP6_OPTION_RELAY_PORT:
+                return false;
+        case SD_DHCP6_OPTION_V6_SZTP_REDIRECT:
+        case SD_DHCP6_OPTION_S46_BIND_IPV6_PREFIX:
+                return true;
+        case SD_DHCP6_OPTION_IA_LL:
+        case SD_DHCP6_OPTION_LLADDR:
+        case SD_DHCP6_OPTION_SLAP_QUAD:
+                return false;
+        case SD_DHCP6_OPTION_V6_DOTS_RI:
+        case SD_DHCP6_OPTION_V6_DOTS_ADDRESS:
+        case SD_DHCP6_OPTION_IPV6_ADDRESS_ANDSF:
+                return true;
+        default:
+                return false;
+        }
+}
+
+static int option_append_hdr(uint8_t **buf, size_t *offset, uint16_t optcode, size_t optlen) {
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        if (optlen > 0xffff)
+                return -ENOBUFS;
+
+        if (optlen + offsetof(DHCP6Option, data) > SIZE_MAX - *offset)
+                return -ENOBUFS;
+
+        if (!GREEDY_REALLOC(*buf, *offset + optlen + offsetof(DHCP6Option, data)))
+                return -ENOMEM;
+
+        unaligned_write_be16(*buf + *offset + offsetof(DHCP6Option, code), optcode);
+        unaligned_write_be16(*buf + *offset + offsetof(DHCP6Option, len), optlen);
+
+        *offset += offsetof(DHCP6Option, data);
+        return 0;
+}
+
+int dhcp6_option_append(
+                uint8_t **buf,
+                size_t *offset,
+                uint16_t code,
+                size_t optlen,
+                const void *optval) {
+
+        int r;
+
+        assert(optval || optlen == 0);
+
+        r = option_append_hdr(buf, offset, code, optlen);
+        if (r < 0)
+                return r;
+
+        memcpy_safe(*buf + *offset, optval, optlen);
+        *offset += optlen;
+
+        return 0;
+}
+
+int dhcp6_option_append_vendor_option(uint8_t **buf, size_t *offset, OrderedSet *vendor_options) {
+        sd_dhcp6_option *options;
+        int r;
+
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        ORDERED_SET_FOREACH(options, vendor_options) {
+                _cleanup_free_ uint8_t *p = NULL;
+                size_t total;
+
+                total = 4 + 2 + 2 + options->length;
+
+                p = malloc(total);
+                if (!p)
+                        return -ENOMEM;
+
+                unaligned_write_be32(p, options->enterprise_identifier);
+                unaligned_write_be16(p + 4, options->option);
+                unaligned_write_be16(p + 6, options->length);
+                memcpy(p + 8, options->data, options->length);
+
+                r = dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_VENDOR_OPTS, total, p);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+static int option_append_ia_address(uint8_t **buf, size_t *offset, const struct iaaddr *address) {
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+        assert(address);
+
+        /* Do not append T1 and T2. */
+        const struct iaaddr a = {
+                .address = address->address,
+        };
+
+        return dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_IAADDR, sizeof(struct iaaddr), &a);
+}
+
+static int option_append_pd_prefix(uint8_t **buf, size_t *offset, const struct iapdprefix *prefix) {
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+        assert(prefix);
+
+        if (prefix->prefixlen == 0)
+                return -EINVAL;
+
+        /* Do not append T1 and T2. */
+        const struct iapdprefix p = {
+                .prefixlen = prefix->prefixlen,
+                .address = prefix->address,
+        };
+
+        return dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_IA_PD_PREFIX, sizeof(struct iapdprefix), &p);
+}
+
+int dhcp6_option_append_ia(uint8_t **buf, size_t *offset, const DHCP6IA *ia) {
+        _cleanup_free_ uint8_t *data = NULL;
+        struct ia_header header;
+        size_t len;
+        int r;
+
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+        assert(ia);
+
+        /* client should not send set T1 and T2. See, RFC 8415, and issue #18090. */
+
+        switch (ia->type) {
+        case SD_DHCP6_OPTION_IA_NA:
+        case SD_DHCP6_OPTION_IA_PD:
+                len = sizeof(struct ia_header);
+                header = (struct ia_header) {
+                        .id = ia->header.id,
+                };
+                break;
+
+        case SD_DHCP6_OPTION_IA_TA:
+                len = sizeof(header.id); /* IA_TA does not have lifetime. */
+                header = (struct ia_header) {
+                        .id = ia->header.id,
+                };
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        if (!GREEDY_REALLOC(data, len))
+                return -ENOMEM;
+
+        memcpy(data, &header, len);
+
+        LIST_FOREACH(addresses, addr, ia->addresses) {
+                if (ia->type == SD_DHCP6_OPTION_IA_PD)
+                        r = option_append_pd_prefix(&data, &len, &addr->iapdprefix);
+                else
+                        r = option_append_ia_address(&data, &len, &addr->iaaddr);
+                if (r < 0)
+                        return r;
+        }
+
+        return dhcp6_option_append(buf, offset, ia->type, len, data);
+}
+
+int dhcp6_option_append_fqdn(uint8_t **buf, size_t *offset, const char *fqdn) {
+        uint8_t buffer[1 + DNS_WIRE_FORMAT_HOSTNAME_MAX];
+        int r;
+
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        if (isempty(fqdn))
+                return 0;
+
+        buffer[0] = DHCP6_FQDN_FLAG_S; /* Request server to perform AAAA RR DNS updates */
+
+        /* Store domain name after flags field */
+        r = dns_name_to_wire_format(fqdn, buffer + 1, sizeof(buffer) - 1, false);
+        if (r <= 0)
+                return r;
+
+        /*
+         * According to RFC 4704, chapter 4.2 only add terminating zero-length
+         * label in case a FQDN is provided. Since dns_name_to_wire_format
+         * always adds terminating zero-length label remove if only a hostname
+         * is provided.
+         */
+        if (dns_name_is_single_label(fqdn))
+                r--;
+
+        return dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_CLIENT_FQDN, 1 + r, buffer);
+}
+
+int dhcp6_option_append_user_class(uint8_t **buf, size_t *offset, char * const *user_class) {
+        _cleanup_free_ uint8_t *p = NULL;
+        size_t n = 0;
+
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        if (strv_isempty(user_class))
+                return 0;
+
+        STRV_FOREACH(s, user_class) {
+                size_t len = strlen(*s);
+
+                if (len > UINT16_MAX || len == 0)
+                        return -EINVAL;
+
+                if (!GREEDY_REALLOC(p, n + len + 2))
+                        return -ENOMEM;
+
+                unaligned_write_be16(p + n, len);
+                memcpy(p + n + 2, *s, len);
+                n += len + 2;
+        }
+
+        return dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_USER_CLASS, n, p);
+}
+
+int dhcp6_option_append_vendor_class(uint8_t **buf, size_t *offset, char * const *vendor_class) {
+        _cleanup_free_ uint8_t *p = NULL;
+        size_t n = 0;
+
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        if (strv_isempty(vendor_class))
+                return 0;
+
+        if (!GREEDY_REALLOC(p, sizeof(be32_t)))
+                return -ENOMEM;
+
+        /* Enterprise Identifier */
+        unaligned_write_be32(p, SYSTEMD_PEN);
+        n += sizeof(be32_t);
+
+        STRV_FOREACH(s, vendor_class) {
+                size_t len = strlen(*s);
+
+                if (len > UINT16_MAX || len == 0)
+                        return -EINVAL;
+
+                if (!GREEDY_REALLOC(p, n + len + 2))
+                        return -ENOMEM;
+
+                unaligned_write_be16(p + n, len);
+                memcpy(p + n + 2, *s, len);
+                n += len + 2;
+        }
+
+        return dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_VENDOR_CLASS, n, p);
+}
+
+int dhcp6_option_parse(
+                const uint8_t *buf,
+                size_t buflen,
+                size_t *offset,
+                uint16_t *ret_option_code,
+                size_t *ret_option_data_len,
+                const uint8_t **ret_option_data) {
+
+        size_t len;
+
+        assert(buf);
+        assert(offset);
+        assert(ret_option_code);
+        assert(ret_option_data_len);
+        assert(ret_option_data);
+
+        if (buflen < offsetof(DHCP6Option, data))
+                return -EBADMSG;
+
+        if (*offset > buflen - offsetof(DHCP6Option, data))
+                return -EBADMSG;
+
+        len = unaligned_read_be16(buf + *offset + offsetof(DHCP6Option, len));
+
+        if (len > buflen - offsetof(DHCP6Option, data) - *offset)
+                return -EBADMSG;
+
+        *ret_option_code = unaligned_read_be16(buf + *offset + offsetof(DHCP6Option, code));
+        *ret_option_data_len = len;
+        *ret_option_data = len == 0 ? NULL : buf + *offset + offsetof(DHCP6Option, data);
+        *offset += offsetof(DHCP6Option, data) + len;
+
+        return 0;
+}
+
+int dhcp6_option_parse_status(const uint8_t *data, size_t data_len, char **ret_status_message) {
+        assert(data || data_len == 0);
+
+        if (data_len < sizeof(uint16_t))
+                return -EBADMSG;
+
+        if (ret_status_message) {
+                char *msg;
+
+                /* The status message MUST NOT be null-terminated. See section 21.13 of RFC8415.
+                 * Let's escape unsafe characters for safety. */
+                msg = cescape_length((const char*) (data + sizeof(uint16_t)), data_len - sizeof(uint16_t));
+                if (!msg)
+                        return -ENOMEM;
+
+                *ret_status_message = msg;
+        }
+
+        return unaligned_read_be16(data);
+}
+
+static int dhcp6_option_parse_ia_options(sd_dhcp6_client *client, const uint8_t *buf, size_t buflen) {
+        int r;
+
+        assert(buf || buflen == 0);
+
+        for (size_t offset = 0; offset < buflen;) {
+                const uint8_t *data;
+                size_t data_len;
+                uint16_t code;
+
+                r = dhcp6_option_parse(buf, buflen, &offset, &code, &data_len, &data);
+                if (r < 0)
+                        return r;
+
+                switch (code) {
+                case SD_DHCP6_OPTION_STATUS_CODE: {
+                        _cleanup_free_ char *msg = NULL;
+
+                        r = dhcp6_option_parse_status(data, data_len, &msg);
+                        if (r == -ENOMEM)
+                                return r;
+                        if (r > 0)
+                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                                              "Received an IA address or PD prefix option with non-zero status: %s%s%s",
+                                                              strempty(msg), isempty(msg) ? "" : ": ",
+                                                              dhcp6_message_status_to_string(r));
+                        if (r < 0)
+                                /* Let's log but ignore the invalid status option. */
+                                log_dhcp6_client_errno(client, r,
+                                                       "Received an IA address or PD prefix option with an invalid status sub option, ignoring: %m");
+                        break;
+                }
+                default:
+                        log_dhcp6_client(client, "Received an unknown sub option %u in IA address or PD prefix, ignoring.", code);
+                }
+        }
+
+        return 0;
+}
+
+static int dhcp6_option_parse_ia_address(sd_dhcp6_client *client, DHCP6IA *ia, const uint8_t *data, size_t len) {
+        _cleanup_free_ DHCP6Address *a = NULL;
+        uint32_t lt_valid, lt_pref;
+        int r;
+
+        assert(ia);
+        assert(data || len == 0);
+
+        if (!IN_SET(ia->type, SD_DHCP6_OPTION_IA_NA, SD_DHCP6_OPTION_IA_TA))
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received an IA address sub-option in an invalid option, ignoring.");
+
+        if (len < sizeof(struct iaaddr))
+                return -EBADMSG;
+
+        a = new(DHCP6Address, 1);
+        if (!a)
+                return -ENOMEM;
+
+        memcpy(&a->iaaddr, data, sizeof(struct iaaddr));
+
+        lt_valid = be32toh(a->iaaddr.lifetime_valid);
+        lt_pref = be32toh(a->iaaddr.lifetime_preferred);
+
+        if (lt_valid == 0)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received an IA address with zero valid lifetime, ignoring.");
+        if (lt_pref > lt_valid)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received an IA address with preferred lifetime %"PRIu32
+                                              " larger than valid lifetime %"PRIu32", ignoring.",
+                                              lt_pref, lt_valid);
+
+        if (len > sizeof(struct iaaddr)) {
+                r = dhcp6_option_parse_ia_options(client, data + sizeof(struct iaaddr), len - sizeof(struct iaaddr));
+                if (r < 0)
+                        return r;
+        }
+
+        LIST_PREPEND(addresses, ia->addresses, TAKE_PTR(a));
+        return 0;
+}
+
+static int dhcp6_option_parse_ia_pdprefix(sd_dhcp6_client *client, DHCP6IA *ia, const uint8_t *data, size_t len) {
+        _cleanup_free_ DHCP6Address *a = NULL;
+        uint32_t lt_valid, lt_pref;
+        int r;
+
+        assert(ia);
+        assert(data || len == 0);
+
+        if (ia->type != SD_DHCP6_OPTION_IA_PD)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received an PD prefix sub-option in an invalid option, ignoring");
+
+        if (len < sizeof(struct iapdprefix))
+                return -EBADMSG;
+
+        a = new(DHCP6Address, 1);
+        if (!a)
+                return -ENOMEM;
+
+        memcpy(&a->iapdprefix, data, sizeof(struct iapdprefix));
+
+        lt_valid = be32toh(a->iapdprefix.lifetime_valid);
+        lt_pref = be32toh(a->iapdprefix.lifetime_preferred);
+
+        if (lt_valid == 0)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received a PD prefix with zero valid lifetime, ignoring.");
+        if (lt_pref > lt_valid)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received a PD prefix with preferred lifetime %"PRIu32
+                                              " larger than valid lifetime %"PRIu32", ignoring.",
+                                              lt_pref, lt_valid);
+
+        if (len > sizeof(struct iapdprefix)) {
+                r = dhcp6_option_parse_ia_options(client, data + sizeof(struct iapdprefix), len - sizeof(struct iapdprefix));
+                if (r < 0)
+                        return r;
+        }
+
+        LIST_PREPEND(addresses, ia->addresses, TAKE_PTR(a));
+        return 0;
+}
+
+int dhcp6_option_parse_ia(
+                sd_dhcp6_client *client,
+                be32_t iaid,
+                uint16_t option_code,
+                size_t option_data_len,
+                const uint8_t *option_data,
+                DHCP6IA **ret) {
+
+        _cleanup_(dhcp6_ia_freep) DHCP6IA *ia = NULL;
+        uint32_t lt_t1, lt_t2;
+        size_t header_len;
+        int r;
+
+        assert(IN_SET(option_code, SD_DHCP6_OPTION_IA_NA, SD_DHCP6_OPTION_IA_TA, SD_DHCP6_OPTION_IA_PD));
+        assert(option_data || option_data_len == 0);
+        assert(ret);
+
+        /* This will return the following:
+         * -ENOMEM: memory allocation error,
+         * -ENOANO: unmatching IAID,
+         * -EINVAL: non-zero status code, or invalid lifetime,
+         * -EBADMSG: invalid message format,
+         * -ENODATA: no valid address or PD prefix,
+         * 0: success. */
+
+        switch (option_code) {
+        case SD_DHCP6_OPTION_IA_NA:
+        case SD_DHCP6_OPTION_IA_PD:
+                header_len = sizeof(struct ia_header);
+                break;
+
+        case SD_DHCP6_OPTION_IA_TA:
+                header_len = sizeof(be32_t); /* IA_TA does not have lifetime. */
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        if (option_data_len < header_len)
+                return -EBADMSG;
+
+        ia = new(DHCP6IA, 1);
+        if (!ia)
+                return -ENOMEM;
+
+        *ia = (DHCP6IA) {
+                .type = option_code,
+        };
+        memcpy(&ia->header, option_data, header_len);
+
+        /* According to RFC8415, IAs which do not match the client's IAID should be ignored,
+         * but not necessary to ignore or refuse the whole message. */
+        if (ia->header.id != iaid)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(ENOANO),
+                                              "Received an IA option with a different IAID "
+                                              "from the one chosen by the client, ignoring.");
+
+        /* It is not necessary to check if the lifetime_t2 is zero here, as in that case it will be updated later. */
+        lt_t1 = be32toh(ia->header.lifetime_t1);
+        lt_t2 = be32toh(ia->header.lifetime_t2);
+
+        if (lt_t1 > lt_t2)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received an IA option with T1 %"PRIu32"sec > T2 %"PRIu32"sec, ignoring.",
+                                              lt_t1, lt_t2);
+        if (lt_t1 == 0 && lt_t2 > 0)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received an IA option with zero T1 and non-zero T2 (%"PRIu32"sec), ignoring.",
+                                              lt_t2);
+
+        for (size_t offset = header_len; offset < option_data_len;) {
+                const uint8_t *subdata;
+                size_t subdata_len;
+                uint16_t subopt;
+
+                r = dhcp6_option_parse(option_data, option_data_len, &offset, &subopt, &subdata_len, &subdata);
+                if (r < 0)
+                        return r;
+
+                switch (subopt) {
+                case SD_DHCP6_OPTION_IAADDR: {
+                        r = dhcp6_option_parse_ia_address(client, ia, subdata, subdata_len);
+                        if (r == -ENOMEM)
+                                return r;
+
+                        /* Ignore non-critical errors in the sub-option. */
+                        break;
+                }
+                case SD_DHCP6_OPTION_IA_PD_PREFIX: {
+                        r = dhcp6_option_parse_ia_pdprefix(client, ia, subdata, subdata_len);
+                        if (r == -ENOMEM)
+                                return r;
+
+                        /* Ignore non-critical errors in the sub-option. */
+                        break;
+                }
+                case SD_DHCP6_OPTION_STATUS_CODE: {
+                        _cleanup_free_ char *msg = NULL;
+
+                        r = dhcp6_option_parse_status(subdata, subdata_len, &msg);
+                        if (r == -ENOMEM)
+                                return r;
+                        if (r > 0)
+                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                                              "Received an IA option with non-zero status: %s%s%s",
+                                                              strempty(msg), isempty(msg) ? "" : ": ",
+                                                              dhcp6_message_status_to_string(r));
+                        if (r < 0)
+                                log_dhcp6_client_errno(client, r,
+                                                       "Received an IA option with an invalid status sub option, ignoring: %m");
+                        break;
+                }
+                default:
+                        log_dhcp6_client(client, "Received an IA option with an unknown sub-option %u, ignoring", subopt);
+                }
+        }
+
+        if (!ia->addresses)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(ENODATA),
+                                              "Received an IA option without valid IA addresses or PD prefixes, ignoring.");
+
+        *ret = TAKE_PTR(ia);
+        return 0;
+}
+
+int dhcp6_option_parse_addresses(
+                const uint8_t *optval,
+                size_t optlen,
+                struct in6_addr **addrs,
+                size_t *count) {
+
+        assert(optval || optlen == 0);
+        assert(addrs);
+        assert(count);
+
+        if (optlen == 0 || optlen % sizeof(struct in6_addr) != 0)
+                return -EBADMSG;
+
+        if (!GREEDY_REALLOC(*addrs, *count + optlen / sizeof(struct in6_addr)))
+                return -ENOMEM;
+
+        memcpy(*addrs + *count, optval, optlen);
+        *count += optlen / sizeof(struct in6_addr);
+
+        return 0;
+}
+
+static int parse_domain(const uint8_t **data, size_t *len, char **ret) {
+        _cleanup_free_ char *domain = NULL;
+        const uint8_t *optval;
+        size_t optlen, n = 0;
+        int r;
+
+        assert(data);
+        assert(len);
+        assert(*data || *len == 0);
+        assert(ret);
+
+        optval = *data;
+        optlen = *len;
+
+        if (optlen <= 1)
+                return -ENODATA;
+
+        for (;;) {
+                const char *label;
+                uint8_t c;
+
+                if (optlen == 0)
+                        break;
+
+                c = *optval;
+                optval++;
+                optlen--;
+
+                if (c == 0)
+                        /* End label */
+                        break;
+                if (c > 63)
+                        return -EBADMSG;
+                if (c > optlen)
+                        return -EMSGSIZE;
+
+                /* Literal label */
+                label = (const char*) optval;
+                optval += c;
+                optlen -= c;
+
+                if (!GREEDY_REALLOC(domain, n + (n != 0) + DNS_LABEL_ESCAPED_MAX))
+                        return -ENOMEM;
+
+                if (n != 0)
+                        domain[n++] = '.';
+
+                r = dns_label_escape(label, c, domain + n, DNS_LABEL_ESCAPED_MAX);
+                if (r < 0)
+                        return r;
+
+                n += r;
+        }
+
+        if (n > 0) {
+                if (!GREEDY_REALLOC(domain, n + 1))
+                        return -ENOMEM;
+
+                domain[n] = '\0';
+        }
+
+        *ret = TAKE_PTR(domain);
+        *data = optval;
+        *len = optlen;
+
+        return n;
+}
+
+int dhcp6_option_parse_domainname(const uint8_t *optval, size_t optlen, char **ret) {
+        _cleanup_free_ char *domain = NULL;
+        int r;
+
+        assert(optval || optlen == 0);
+        assert(ret);
+
+        r = parse_domain(&optval, &optlen, &domain);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENODATA;
+        if (optlen != 0)
+                return -EINVAL;
+
+        *ret = TAKE_PTR(domain);
+        return 0;
+}
+
+int dhcp6_option_parse_domainname_list(const uint8_t *optval, size_t optlen, char ***ret) {
+        _cleanup_strv_free_ char **names = NULL;
+        int r;
+
+        assert(optval || optlen == 0);
+        assert(ret);
+
+        if (optlen <= 1)
+                return -ENODATA;
+        if (optval[optlen - 1] != '\0')
+                return -EINVAL;
+
+        while (optlen > 0) {
+                _cleanup_free_ char *name = NULL;
+
+                r = parse_domain(&optval, &optlen, &name);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                r = strv_consume(&names, TAKE_PTR(name));
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(names);
+        return 0;
+}
+
+static sd_dhcp6_option* dhcp6_option_free(sd_dhcp6_option *i) {
+        if (!i)
+                return NULL;
+
+        free(i->data);
+        return mfree(i);
+}
+
+int sd_dhcp6_option_new(uint16_t option, const void *data, size_t length, uint32_t enterprise_identifier, sd_dhcp6_option **ret) {
+        assert_return(ret, -EINVAL);
+        assert_return(length == 0 || data, -EINVAL);
+
+        _cleanup_free_ void *q = memdup(data, length);
+        if (!q)
+                return -ENOMEM;
+
+        sd_dhcp6_option *p = new(sd_dhcp6_option, 1);
+        if (!p)
+                return -ENOMEM;
+
+        *p = (sd_dhcp6_option) {
+                .n_ref = 1,
+                .option = option,
+                .enterprise_identifier = enterprise_identifier,
+                .length = length,
+                .data = TAKE_PTR(q),
+        };
+
+        *ret = p;
+        return 0;
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp6_option, sd_dhcp6_option, dhcp6_option_free);
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+                dhcp6_option_hash_ops,
+                void,
+                trivial_hash_func,
+                trivial_compare_func,
+                sd_dhcp6_option,
+                sd_dhcp6_option_unref);
diff --git a/src/libsystemd-network/dhcp6-option.h b/src/libsystemd-network/dhcp6-option.h
new file mode 100644
index 0000000..36841dd
--- /dev/null
+++ b/src/libsystemd-network/dhcp6-option.h
@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-dhcp6-client.h"
+
+#include "hash-funcs.h"
+#include "list.h"
+#include "macro.h"
+#include "ordered-set.h"
+#include "sparse-endian.h"
+
+typedef struct sd_dhcp6_option {
+        unsigned n_ref;
+
+        uint32_t enterprise_identifier;
+        uint16_t option;
+        void *data;
+        size_t length;
+} sd_dhcp6_option;
+
+extern const struct hash_ops dhcp6_option_hash_ops;
+
+/* Common option header */
+typedef struct DHCP6Option {
+        be16_t code;
+        be16_t len;
+        uint8_t data[];
+} _packed_ DHCP6Option;
+
+/* Address option */
+struct iaaddr {
+        struct in6_addr address;
+        be32_t lifetime_preferred;
+        be32_t lifetime_valid;
+} _packed_;
+
+/* Prefix Delegation Prefix option */
+struct iapdprefix {
+        be32_t lifetime_preferred;
+        be32_t lifetime_valid;
+        uint8_t prefixlen;
+        struct in6_addr address;
+} _packed_;
+
+typedef struct DHCP6Address DHCP6Address;
+
+struct DHCP6Address {
+        LIST_FIELDS(DHCP6Address, addresses);
+
+        union {
+                struct iaaddr iaaddr;
+                struct iapdprefix iapdprefix;
+        };
+};
+
+struct ia_header {
+        be32_t id;
+        be32_t lifetime_t1;
+        be32_t lifetime_t2;
+} _packed_;
+
+typedef struct DHCP6IA {
+        uint16_t type;
+        struct ia_header header;
+
+        LIST_HEAD(DHCP6Address, addresses);
+} DHCP6IA;
+
+void dhcp6_ia_clear_addresses(DHCP6IA *ia);
+DHCP6IA *dhcp6_ia_free(DHCP6IA *ia);
+DEFINE_TRIVIAL_CLEANUP_FUNC(DHCP6IA*, dhcp6_ia_free);
+
+bool dhcp6_option_can_request(uint16_t option);
+
+int dhcp6_option_append(uint8_t **buf, size_t *offset, uint16_t code,
+                        size_t optlen, const void *optval);
+int dhcp6_option_append_ia(uint8_t **buf, size_t *offset, const DHCP6IA *ia);
+int dhcp6_option_append_fqdn(uint8_t **buf, size_t *offset, const char *fqdn);
+int dhcp6_option_append_user_class(uint8_t **buf, size_t *offset, char * const *user_class);
+int dhcp6_option_append_vendor_class(uint8_t **buf, size_t *offset, char * const *vendor_class);
+int dhcp6_option_append_vendor_option(uint8_t **buf, size_t *offset, OrderedSet *vendor_options);
+
+int dhcp6_option_parse(
+                const uint8_t *buf,
+                size_t buflen,
+                size_t *offset,
+                uint16_t *ret_option_code,
+                size_t *ret_option_data_len,
+                const uint8_t **ret_option_data);
+int dhcp6_option_parse_status(const uint8_t *data, size_t data_len, char **ret_status_message);
+int dhcp6_option_parse_ia(
+                sd_dhcp6_client *client,
+                be32_t iaid,
+                uint16_t option_code,
+                size_t option_data_len,
+                const uint8_t *option_data,
+                DHCP6IA **ret);
+int dhcp6_option_parse_addresses(
+                const uint8_t *optval,
+                size_t optlen,
+                struct in6_addr **addrs,
+                size_t *count);
+int dhcp6_option_parse_domainname_list(const uint8_t *optval, size_t optlen, char ***ret);
+int dhcp6_option_parse_domainname(const uint8_t *optval, size_t optlen, char **ret);
diff --git a/src/libsystemd-network/dhcp6-protocol.c b/src/libsystemd-network/dhcp6-protocol.c
new file mode 100644
index 0000000..f965ea4
--- /dev/null
+++ b/src/libsystemd-network/dhcp6-protocol.c
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "dhcp6-protocol.h"
+#include "string-table.h"
+
+static const char * const dhcp6_state_table[_DHCP6_STATE_MAX] = {
+        [DHCP6_STATE_STOPPED]             = "stopped",
+        [DHCP6_STATE_INFORMATION_REQUEST] = "information-request",
+        [DHCP6_STATE_SOLICITATION]        = "solicitation",
+        [DHCP6_STATE_REQUEST]             = "request",
+        [DHCP6_STATE_BOUND]               = "bound",
+        [DHCP6_STATE_RENEW]               = "renew",
+        [DHCP6_STATE_REBIND]              = "rebind",
+};
+
+DEFINE_STRING_TABLE_LOOKUP_TO_STRING(dhcp6_state, DHCP6State);
+
+static const char * const dhcp6_message_type_table[_DHCP6_MESSAGE_TYPE_MAX] = {
+        [DHCP6_MESSAGE_SOLICIT]             = "Solicit",
+        [DHCP6_MESSAGE_ADVERTISE]           = "Advertise",
+        [DHCP6_MESSAGE_REQUEST]             = "Request",
+        [DHCP6_MESSAGE_CONFIRM]             = "Confirm",
+        [DHCP6_MESSAGE_RENEW]               = "Renew",
+        [DHCP6_MESSAGE_REBIND]              = "Rebind",
+        [DHCP6_MESSAGE_REPLY]               = "Reply",
+        [DHCP6_MESSAGE_RELEASE]             = "Release",
+        [DHCP6_MESSAGE_DECLINE]             = "Decline",
+        [DHCP6_MESSAGE_RECONFIGURE]         = "Reconfigure",
+        [DHCP6_MESSAGE_INFORMATION_REQUEST] = "Information Request",
+        [DHCP6_MESSAGE_RELAY_FORWARD]       = "Relay Forward",
+        [DHCP6_MESSAGE_RELAY_REPLY]         = "Relay Reply",
+        [DHCP6_MESSAGE_LEASE_QUERY]         = "Lease Query",
+        [DHCP6_MESSAGE_LEASE_QUERY_REPLY]   = "Lease Query Reply",
+        [DHCP6_MESSAGE_LEASE_QUERY_DONE]    = "Lease Query Done",
+        [DHCP6_MESSAGE_LEASE_QUERY_DATA]    = "Lease Query Data",
+        [DHCP6_MESSAGE_RECONFIGURE_REQUEST] = "Reconfigure Request",
+        [DHCP6_MESSAGE_RECONFIGURE_REPLY]   = "Reconfigure Reply",
+        [DHCP6_MESSAGE_DHCPV4_QUERY]        = "DHCPv4 Query",
+        [DHCP6_MESSAGE_DHCPV4_RESPONSE]     = "DHCPv4 Response",
+        [DHCP6_MESSAGE_ACTIVE_LEASE_QUERY]  = "Active Lease Query",
+        [DHCP6_MESSAGE_START_TLS]           = "Start TLS",
+        [DHCP6_MESSAGE_BINDING_UPDATE]      = "Binding Update",
+        [DHCP6_MESSAGE_BINDING_REPLY]       = "Binding Reply",
+        [DHCP6_MESSAGE_POOL_REQUEST]        = "Pool Request",
+        [DHCP6_MESSAGE_POOL_RESPONSE]       = "Pool Response",
+        [DHCP6_MESSAGE_UPDATE_REQUEST]      = "Update Request",
+        [DHCP6_MESSAGE_UPDATE_REQUEST_ALL]  = "Update Request All",
+        [DHCP6_MESSAGE_UPDATE_DONE]         = "Update Done",
+        [DHCP6_MESSAGE_CONNECT]             = "Connect",
+        [DHCP6_MESSAGE_CONNECT_REPLY]       = "Connect Reply",
+        [DHCP6_MESSAGE_DISCONNECT]          = "Disconnect",
+        [DHCP6_MESSAGE_STATE]               = "State",
+        [DHCP6_MESSAGE_CONTACT]             = "Contact",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(dhcp6_message_type, DHCP6MessageType);
+
+static const char * const dhcp6_message_status_table[_DHCP6_STATUS_MAX] = {
+        [DHCP6_STATUS_SUCCESS]                      = "Success",
+        [DHCP6_STATUS_UNSPEC_FAIL]                  = "Unspecified failure",
+        [DHCP6_STATUS_NO_ADDRS_AVAIL]               = "No addresses available",
+        [DHCP6_STATUS_NO_BINDING]                   = "Binding unavailable",
+        [DHCP6_STATUS_NOT_ON_LINK]                  = "Not on link",
+        [DHCP6_STATUS_USE_MULTICAST]                = "Use multicast",
+        [DHCP6_STATUS_NO_PREFIX_AVAIL]              = "No prefix available",
+        [DHCP6_STATUS_UNKNOWN_QUERY_TYPE]           = "Unknown query type",
+        [DHCP6_STATUS_MALFORMED_QUERY]              = "Malformed query",
+        [DHCP6_STATUS_NOT_CONFIGURED]               = "Not configured",
+        [DHCP6_STATUS_NOT_ALLOWED]                  = "Not allowed",
+        [DHCP6_STATUS_QUERY_TERMINATED]             = "Query terminated",
+        [DHCP6_STATUS_DATA_MISSING]                 = "Data missing",
+        [DHCP6_STATUS_CATCHUP_COMPLETE]             = "Catch up complete",
+        [DHCP6_STATUS_NOT_SUPPORTED]                = "Not supported",
+        [DHCP6_STATUS_TLS_CONNECTION_REFUSED]       = "TLS connection refused",
+        [DHCP6_STATUS_ADDRESS_IN_USE]               = "Address in use",
+        [DHCP6_STATUS_CONFIGURATION_CONFLICT]       = "Configuration conflict",
+        [DHCP6_STATUS_MISSING_BINDING_INFORMATION]  = "Missing binding information",
+        [DHCP6_STATUS_OUTDATED_BINDING_INFORMATION] = "Outdated binding information",
+        [DHCP6_STATUS_SERVER_SHUTTING_DOWN]         = "Server shutting down",
+        [DHCP6_STATUS_DNS_UPDATE_NOT_SUPPORTED]     = "DNS update not supported",
+        [DHCP6_STATUS_EXCESSIVE_TIME_SKEW]          = "Excessive time skew",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(dhcp6_message_status, DHCP6Status);
+
+int dhcp6_message_status_to_errno(DHCP6Status s) {
+        switch (s) {
+        case DHCP6_STATUS_SUCCESS:
+                return 0;
+        case DHCP6_STATUS_NO_BINDING:
+                return -EADDRNOTAVAIL;
+        default:
+                return -EINVAL;
+        }
+}
diff --git a/src/libsystemd-network/dhcp6-protocol.h b/src/libsystemd-network/dhcp6-protocol.h
new file mode 100644
index 0000000..1821769
--- /dev/null
+++ b/src/libsystemd-network/dhcp6-protocol.h
@@ -0,0 +1,157 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <netinet/ip6.h>
+#include <netinet/udp.h>
+
+#include "macro.h"
+#include "sparse-endian.h"
+
+struct DHCP6Message {
+        union {
+                struct {
+                        uint8_t type;
+                        uint8_t _pad[3];
+                } _packed_;
+                be32_t transaction_id;
+        };
+        uint8_t options[];
+} _packed_;
+
+typedef struct DHCP6Message DHCP6Message;
+
+#define DHCP6_MIN_OPTIONS_SIZE \
+        1280 - sizeof(struct ip6_hdr) - sizeof(struct udphdr)
+
+#define IN6ADDR_ALL_DHCP6_RELAY_AGENTS_AND_SERVERS_INIT                 \
+        { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,           \
+              0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x02 } } }
+
+enum {
+        DHCP6_PORT_SERVER                       = 547,
+        DHCP6_PORT_CLIENT                       = 546,
+};
+
+#define DHCP6_INF_TIMEOUT                       (1 * USEC_PER_SEC)
+#define DHCP6_INF_MAX_RT                        (120 * USEC_PER_SEC)
+#define DHCP6_SOL_MAX_DELAY                     (1 * USEC_PER_SEC)
+#define DHCP6_SOL_TIMEOUT                       (1 * USEC_PER_SEC)
+#define DHCP6_SOL_MAX_RT                        (120 * USEC_PER_SEC)
+#define DHCP6_REQ_TIMEOUT                       (1 * USEC_PER_SEC)
+#define DHCP6_REQ_MAX_RT                        (120 * USEC_PER_SEC)
+#define DHCP6_REQ_MAX_RC                        10
+#define DHCP6_REN_TIMEOUT                       (10 * USEC_PER_SEC)
+#define DHCP6_REN_MAX_RT                        (600 * USEC_PER_SEC)
+#define DHCP6_REB_TIMEOUT                       (10 * USEC_PER_SEC)
+#define DHCP6_REB_MAX_RT                        (600 * USEC_PER_SEC)
+
+typedef enum DHCP6State {
+        DHCP6_STATE_STOPPED,
+        DHCP6_STATE_INFORMATION_REQUEST,
+        DHCP6_STATE_SOLICITATION,
+        DHCP6_STATE_REQUEST,
+        DHCP6_STATE_BOUND,
+        DHCP6_STATE_RENEW,
+        DHCP6_STATE_REBIND,
+        _DHCP6_STATE_MAX,
+        _DHCP6_STATE_INVALID = -EINVAL,
+} DHCP6State;
+
+/* https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml#dhcpv6-parameters-1 */
+typedef enum DHCP6MessageType {
+        DHCP6_MESSAGE_SOLICIT                   = 1,  /* RFC 8415 */
+        DHCP6_MESSAGE_ADVERTISE                 = 2,  /* RFC 8415 */
+        DHCP6_MESSAGE_REQUEST                   = 3,  /* RFC 8415 */
+        DHCP6_MESSAGE_CONFIRM                   = 4,  /* RFC 8415 */
+        DHCP6_MESSAGE_RENEW                     = 5,  /* RFC 8415 */
+        DHCP6_MESSAGE_REBIND                    = 6,  /* RFC 8415 */
+        DHCP6_MESSAGE_REPLY                     = 7,  /* RFC 8415 */
+        DHCP6_MESSAGE_RELEASE                   = 8,  /* RFC 8415 */
+        DHCP6_MESSAGE_DECLINE                   = 9,  /* RFC 8415 */
+        DHCP6_MESSAGE_RECONFIGURE               = 10, /* RFC 8415 */
+        DHCP6_MESSAGE_INFORMATION_REQUEST       = 11, /* RFC 8415 */
+        DHCP6_MESSAGE_RELAY_FORWARD             = 12, /* RFC 8415 */
+        DHCP6_MESSAGE_RELAY_REPLY               = 13, /* RFC 8415 */
+        DHCP6_MESSAGE_LEASE_QUERY               = 14, /* RFC 5007 */
+        DHCP6_MESSAGE_LEASE_QUERY_REPLY         = 15, /* RFC 5007 */
+        DHCP6_MESSAGE_LEASE_QUERY_DONE          = 16, /* RFC 5460 */
+        DHCP6_MESSAGE_LEASE_QUERY_DATA          = 17, /* RFC 5460 */
+        DHCP6_MESSAGE_RECONFIGURE_REQUEST       = 18, /* RFC 6977 */
+        DHCP6_MESSAGE_RECONFIGURE_REPLY         = 19, /* RFC 6977 */
+        DHCP6_MESSAGE_DHCPV4_QUERY              = 20, /* RFC 7341 */
+        DHCP6_MESSAGE_DHCPV4_RESPONSE           = 21, /* RFC 7341 */
+        DHCP6_MESSAGE_ACTIVE_LEASE_QUERY        = 22, /* RFC 7653 */
+        DHCP6_MESSAGE_START_TLS                 = 23, /* RFC 7653 */
+        DHCP6_MESSAGE_BINDING_UPDATE            = 24, /* RFC 8156 */
+        DHCP6_MESSAGE_BINDING_REPLY             = 25, /* RFC 8156 */
+        DHCP6_MESSAGE_POOL_REQUEST              = 26, /* RFC 8156 */
+        DHCP6_MESSAGE_POOL_RESPONSE             = 27, /* RFC 8156 */
+        DHCP6_MESSAGE_UPDATE_REQUEST            = 28, /* RFC 8156 */
+        DHCP6_MESSAGE_UPDATE_REQUEST_ALL        = 29, /* RFC 8156 */
+        DHCP6_MESSAGE_UPDATE_DONE               = 30, /* RFC 8156 */
+        DHCP6_MESSAGE_CONNECT                   = 31, /* RFC 8156 */
+        DHCP6_MESSAGE_CONNECT_REPLY             = 32, /* RFC 8156 */
+        DHCP6_MESSAGE_DISCONNECT                = 33, /* RFC 8156 */
+        DHCP6_MESSAGE_STATE                     = 34, /* RFC 8156 */
+        DHCP6_MESSAGE_CONTACT                   = 35, /* RFC 8156 */
+        _DHCP6_MESSAGE_TYPE_MAX,
+        _DHCP6_MESSAGE_TYPE_INVALID             = -EINVAL,
+} DHCP6MessageType;
+
+typedef enum DHCP6NTPSubOption {
+        DHCP6_NTP_SUBOPTION_SRV_ADDR            = 1,
+        DHCP6_NTP_SUBOPTION_MC_ADDR             = 2,
+        DHCP6_NTP_SUBOPTION_SRV_FQDN            = 3,
+        _DHCP6_NTP_SUBOPTION_MAX,
+        _DHCP6_NTP_SUBOPTION_INVALID            = -EINVAL,
+} DHCP6NTPSubOption;
+
+/*
+ * RFC 8415, RFC 5007 and RFC 7653 status codes:
+ * https://www.iana.org/assignments/dhcpv6-parameters/dhcpv6-parameters.xhtml#dhcpv6-parameters-5
+ */
+typedef enum DHCP6Status {
+        DHCP6_STATUS_SUCCESS                      = 0,
+        DHCP6_STATUS_UNSPEC_FAIL                  = 1,
+        DHCP6_STATUS_NO_ADDRS_AVAIL               = 2,
+        DHCP6_STATUS_NO_BINDING                   = 3,
+        DHCP6_STATUS_NOT_ON_LINK                  = 4,
+        DHCP6_STATUS_USE_MULTICAST                = 5,
+        DHCP6_STATUS_NO_PREFIX_AVAIL              = 6,
+        DHCP6_STATUS_UNKNOWN_QUERY_TYPE           = 7,
+        DHCP6_STATUS_MALFORMED_QUERY              = 8,
+        DHCP6_STATUS_NOT_CONFIGURED               = 9,
+        DHCP6_STATUS_NOT_ALLOWED                  = 10,
+        DHCP6_STATUS_QUERY_TERMINATED             = 11,
+        DHCP6_STATUS_DATA_MISSING                 = 12,
+        DHCP6_STATUS_CATCHUP_COMPLETE             = 13,
+        DHCP6_STATUS_NOT_SUPPORTED                = 14,
+        DHCP6_STATUS_TLS_CONNECTION_REFUSED       = 15,
+        DHCP6_STATUS_ADDRESS_IN_USE               = 16,
+        DHCP6_STATUS_CONFIGURATION_CONFLICT       = 17,
+        DHCP6_STATUS_MISSING_BINDING_INFORMATION  = 18,
+        DHCP6_STATUS_OUTDATED_BINDING_INFORMATION = 19,
+        DHCP6_STATUS_SERVER_SHUTTING_DOWN         = 20,
+        DHCP6_STATUS_DNS_UPDATE_NOT_SUPPORTED     = 21,
+        DHCP6_STATUS_EXCESSIVE_TIME_SKEW          = 22,
+        _DHCP6_STATUS_MAX,
+        _DHCP6_STATUS_INVALID                     = -EINVAL,
+} DHCP6Status;
+
+typedef enum DHCP6FQDNFlag {
+        DHCP6_FQDN_FLAG_S = 1 << 0,
+        DHCP6_FQDN_FLAG_O = 1 << 1,
+        DHCP6_FQDN_FLAG_N = 1 << 2,
+} DHCP6FQDNFlag;
+
+const char *dhcp6_state_to_string(DHCP6State s) _const_;
+const char *dhcp6_message_type_to_string(DHCP6MessageType s) _const_;
+DHCP6MessageType dhcp6_message_type_from_string(const char *s) _pure_;
+const char *dhcp6_message_status_to_string(DHCP6Status s) _const_;
+DHCP6Status dhcp6_message_status_from_string(const char *s) _pure_;
+int dhcp6_message_status_to_errno(DHCP6Status s);
diff --git a/src/libsystemd-network/fuzz-dhcp-client.c b/src/libsystemd-network/fuzz-dhcp-client.c
new file mode 100644
index 0000000..6ca9f51
--- /dev/null
+++ b/src/libsystemd-network/fuzz-dhcp-client.c
@@ -0,0 +1,78 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "sd-dhcp-client.c"
+
+#include "alloc-util.h"
+#include "fuzz.h"
+
+int dhcp_network_bind_raw_socket(
+                int ifindex,
+                union sockaddr_union *link,
+                uint32_t id,
+                const struct hw_addr_data *hw_addr,
+                const struct hw_addr_data *bcast_addr,
+                uint16_t arp_type, uint16_t port) {
+
+        int fd;
+        fd = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (fd < 0)
+                return -errno;
+
+        return fd;
+}
+
+int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link, const void *packet, size_t len) {
+        return len;
+}
+
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
+        int fd;
+
+        fd = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (fd < 0)
+                return -errno;
+
+        return fd;
+}
+
+int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port, const void *packet, size_t len) {
+        return len;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        uint8_t mac_addr[] = {'A', 'B', 'C', '1', '2', '3'};
+        uint8_t bcast_addr[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF };
+        _cleanup_(sd_dhcp_client_unrefp) sd_dhcp_client *client = NULL;
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        int res, r;
+
+        if (!getenv("SYSTEMD_LOG_LEVEL"))
+                log_set_max_level(LOG_CRIT);
+
+        r = sd_dhcp_client_new(&client, false);
+        assert_se(r >= 0);
+        assert_se(client);
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        r = sd_dhcp_client_attach_event(client, e, 0);
+        assert_se(r >= 0);
+
+        assert_se(sd_dhcp_client_set_ifindex(client, 42) >= 0);
+        assert_se(sd_dhcp_client_set_mac(client, mac_addr, bcast_addr, ETH_ALEN, ARPHRD_ETHER) >= 0);
+        dhcp_client_set_test_mode(client, true);
+
+        res = sd_dhcp_client_start(client);
+        assert_se(IN_SET(res, 0, -EINPROGRESS));
+        client->xid = 2;
+
+        (void) client_handle_offer(client, (DHCPMessage*) data, size);
+
+        assert_se(sd_dhcp_client_stop(client) >= 0);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/fuzz-dhcp-server-relay.c b/src/libsystemd-network/fuzz-dhcp-server-relay.c
new file mode 100644
index 0000000..0de73d3
--- /dev/null
+++ b/src/libsystemd-network/fuzz-dhcp-server-relay.c
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "sd-dhcp-server.c"
+
+#include "fuzz.h"
+
+ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen) {
+        return len;
+}
+
+ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags) {
+        return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL;
+        struct in_addr address = {.s_addr = htobe32(UINT32_C(10) << 24 | UINT32_C(1))};
+        union in_addr_union relay_address;
+        _cleanup_free_ uint8_t *message = NULL;
+
+        if (size < sizeof(DHCPMessage))
+                return 0;
+
+        assert_se(sd_dhcp_server_new(&server, 1) >= 0);
+        assert_se(sd_dhcp_server_attach_event(server, NULL, 0) >= 0);
+        assert_se(sd_dhcp_server_configure_pool(server, &address, 24, 0, 0) >= 0);
+        assert_se(in_addr_from_string(AF_INET, "192.168.5.1", &relay_address) >= 0);
+        assert_se(sd_dhcp_server_set_relay_target(server, &relay_address.in) >= 0);
+        assert_se(sd_dhcp_server_set_bind_to_interface(server, false) >= 0);
+        assert_se(sd_dhcp_server_set_relay_agent_information(server, "string:sample_circuit_id", "string:sample_remote_id") >= 0);
+
+        size_t buflen = size;
+        buflen += relay_agent_information_length(server->agent_circuit_id, server->agent_remote_id) + 2;
+        assert_se(message = malloc(buflen));
+        memcpy(message, data, size);
+
+        server->fd = open("/dev/null", O_RDWR|O_CLOEXEC|O_NOCTTY);
+        assert_se(server->fd >= 0);
+
+        (void) dhcp_server_relay_message(server, (DHCPMessage *) message, size - sizeof(DHCPMessage), buflen);
+        return 0;
+}
diff --git a/src/libsystemd-network/fuzz-dhcp-server.c b/src/libsystemd-network/fuzz-dhcp-server.c
new file mode 100644
index 0000000..d260646
--- /dev/null
+++ b/src/libsystemd-network/fuzz-dhcp-server.c
@@ -0,0 +1,102 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include "sd-dhcp-server.c"
+
+#include "fuzz.h"
+
+/* stub out network so that the server doesn't send */
+ssize_t sendto(int sockfd, const void *buf, size_t len, int flags, const struct sockaddr *dest_addr, socklen_t addrlen) {
+        return len;
+}
+
+ssize_t sendmsg(int sockfd, const struct msghdr *msg, int flags) {
+        return 0;
+}
+
+static int add_lease(sd_dhcp_server *server, const struct in_addr *server_address, uint8_t i) {
+        _cleanup_(dhcp_lease_freep) DHCPLease *lease = NULL;
+        static const uint8_t chaddr[] = {3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3};
+        int r;
+
+        assert(server);
+
+        lease = new0(DHCPLease, 1);
+        if (!lease)
+                return -ENOMEM;
+
+        lease->client_id.data = malloc(2);
+        if (!lease->client_id.data)
+                return -ENOMEM;
+
+        lease->client_id.length = 2;
+        lease->client_id.data[0] = 2;
+        lease->client_id.data[1] = i;
+
+        lease->address = htobe32(UINT32_C(10) << 24 | i);
+        lease->gateway = server_address->s_addr;
+        lease->expiration = UINT64_MAX;
+        lease->htype = ARPHRD_ETHER;
+        lease->hlen = ETH_ALEN;
+        memcpy(lease->chaddr, chaddr, ETH_ALEN);
+
+        lease->server = server; /* This must be set just before hashmap_put(). */
+
+        r = hashmap_ensure_put(&server->bound_leases_by_client_id, &dhcp_lease_hash_ops, &lease->client_id, lease);
+        if (r < 0)
+                return r;
+
+        r = hashmap_ensure_put(&server->bound_leases_by_address, NULL, UINT32_TO_PTR(lease->address), lease);
+        if (r < 0)
+                return r;
+
+        TAKE_PTR(lease);
+
+        return 0;
+}
+
+static int add_static_lease(sd_dhcp_server *server, uint8_t i) {
+        uint8_t id[2] = { 2, i };
+        int r;
+
+        assert(server);
+
+        r = sd_dhcp_server_set_static_lease(
+                                server,
+                                &(struct in_addr) { .s_addr = htobe32(UINT32_C(10) << 24 | i)},
+                                id, ELEMENTSOF(id));
+
+        return r;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL;
+        struct in_addr address = { .s_addr = htobe32(UINT32_C(10) << 24 | UINT32_C(1))};
+        _cleanup_free_ uint8_t *duped = NULL;
+
+        if (size < sizeof(DHCPMessage))
+                return 0;
+
+        assert_se(duped = memdup(data, size));
+
+        assert_se(sd_dhcp_server_new(&server, 1) >= 0);
+        assert_se(sd_dhcp_server_attach_event(server, NULL, 0) >= 0);
+        server->fd = open("/dev/null", O_RDWR|O_CLOEXEC|O_NOCTTY);
+        assert_se(server->fd >= 0);
+        assert_se(sd_dhcp_server_configure_pool(server, &address, 24, 0, 0) >= 0);
+
+        /* add leases to the pool to expose additional code paths */
+        assert_se(add_lease(server, &address, 2) >= 0);
+        assert_se(add_lease(server, &address, 3) >= 0);
+
+        /* add static leases */
+        assert_se(add_static_lease(server, 3) >= 0);
+        assert_se(add_static_lease(server, 4) >= 0);
+
+        (void) dhcp_server_handle_message(server, (DHCPMessage*) duped, size);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/fuzz-dhcp6-client.c b/src/libsystemd-network/fuzz-dhcp6-client.c
new file mode 100644
index 0000000..c64fa73
--- /dev/null
+++ b/src/libsystemd-network/fuzz-dhcp6-client.c
@@ -0,0 +1,111 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <unistd.h>
+
+#include "sd-dhcp6-client.h"
+#include "sd-event.h"
+
+#include "dhcp6-internal.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "fuzz.h"
+
+static int test_dhcp_fd[2] = { -1, -1 };
+
+int dhcp6_network_send_udp_socket(int s, struct in6_addr *server_address, const void *packet, size_t len) {
+        return len;
+}
+
+int dhcp6_network_bind_udp_socket(int index, struct in6_addr *local_address) {
+        assert_se(socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_dhcp_fd) >= 0);
+        return TAKE_FD(test_dhcp_fd[0]);
+}
+
+static void fuzz_client(sd_dhcp6_client *client, const uint8_t *data, size_t size, DHCP6State state) {
+        assert_se(sd_dhcp6_client_set_information_request(client, state == DHCP6_STATE_INFORMATION_REQUEST) >= 0);
+        assert_se(sd_dhcp6_client_start(client) >= 0);
+
+        client->state = state;
+
+        if (size >= sizeof(DHCP6Message))
+                assert_se(dhcp6_client_set_transaction_id(client, ((const DHCP6Message *) data)->transaction_id) == 0);
+
+        /* These states does not require lease to send message. */
+        if (IN_SET(client->state, DHCP6_STATE_INFORMATION_REQUEST, DHCP6_STATE_SOLICITATION))
+                assert_se(dhcp6_client_send_message(client) >= 0);
+
+        assert_se(write(test_dhcp_fd[1], data, size) == (ssize_t) size);
+
+        assert_se(sd_event_run(sd_dhcp6_client_get_event(client), UINT64_MAX) > 0);
+
+        /* Check the state transition. */
+        if (client->state != state)
+                switch (state) {
+                case DHCP6_STATE_INFORMATION_REQUEST:
+                        assert_se(client->state == DHCP6_STATE_STOPPED);
+                        break;
+                case DHCP6_STATE_SOLICITATION:
+                        assert_se(IN_SET(client->state, DHCP6_STATE_REQUEST, DHCP6_STATE_BOUND));
+                        break;
+                case DHCP6_STATE_REQUEST:
+                        assert_se(IN_SET(client->state, DHCP6_STATE_BOUND, DHCP6_STATE_SOLICITATION));
+                        break;
+                default:
+                        assert_not_reached();
+                }
+
+        /* Send message if the client has a lease. */
+        if (state != DHCP6_STATE_INFORMATION_REQUEST && sd_dhcp6_client_get_lease(client, NULL) >= 0) {
+                client->state = DHCP6_STATE_REQUEST;
+                dhcp6_client_send_message(client);
+        }
+
+        assert_se(sd_dhcp6_client_stop(client) >= 0);
+
+        test_dhcp_fd[1] = safe_close(test_dhcp_fd[1]);
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_dhcp6_client_unrefp) sd_dhcp6_client *client = NULL;
+        _cleanup_(sd_dhcp6_option_unrefp) sd_dhcp6_option *v1 = NULL, *v2 = NULL;
+        struct in6_addr address = { { { 0xfe, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0x01 } } };
+        struct in6_addr hint = { { { 0x3f, 0xfe, 0x05, 0x01, 0xff, 0xff, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 } } };
+        static const char *v1_data = "hogehoge", *v2_data = "foobar";
+
+        if (!getenv("SYSTEMD_LOG_LEVEL"))
+                log_set_max_level(LOG_CRIT);
+
+        if (outside_size_range(size, 0, 65536))
+                return 0;
+
+        assert_se(sd_event_new(&e) >= 0);
+        assert_se(sd_dhcp6_client_new(&client) >= 0);
+        assert_se(sd_dhcp6_client_attach_event(client, e, 0) >= 0);
+        assert_se(sd_dhcp6_client_set_ifindex(client, 42) >= 0);
+        assert_se(sd_dhcp6_client_set_local_address(client, &address) >= 0);
+        dhcp6_client_set_test_mode(client, true);
+
+        /* Used when sending message. */
+        assert_se(sd_dhcp6_client_set_fqdn(client, "example.com") == 1);
+        assert_se(sd_dhcp6_client_set_request_mud_url(client, "https://www.example.com/mudfile.json") >= 0);
+        assert_se(sd_dhcp6_client_set_request_user_class(client, STRV_MAKE("u1", "u2", "u3")) >= 0);
+        assert_se(sd_dhcp6_client_set_request_vendor_class(client, STRV_MAKE("v1", "v2", "v3")) >= 0);
+        assert_se(sd_dhcp6_client_set_prefix_delegation_hint(client, 48, &hint) >= 0);
+        assert_se(sd_dhcp6_option_new(123, v1_data, strlen(v1_data), 12345, &v1) >= 0);
+        assert_se(sd_dhcp6_option_new(456, v2_data, strlen(v2_data), 45678, &v2) >= 0);
+        assert_se(sd_dhcp6_client_add_vendor_option(client, v1) >= 0);
+        assert_se(sd_dhcp6_client_add_vendor_option(client, v2) >= 0);
+
+        fuzz_client(client, data, size, DHCP6_STATE_INFORMATION_REQUEST);
+        fuzz_client(client, data, size, DHCP6_STATE_SOLICITATION);
+
+        /* If size is zero, then the resend timer will be triggered at first,
+         * but in the REQUEST state the client must have a lease. */
+        if (size == 0)
+                return 0;
+
+        fuzz_client(client, data, size, DHCP6_STATE_REQUEST);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/fuzz-dhcp6-client.options b/src/libsystemd-network/fuzz-dhcp6-client.options
new file mode 100644
index 0000000..678d526
--- /dev/null
+++ b/src/libsystemd-network/fuzz-dhcp6-client.options
@@ -0,0 +1,2 @@
+[libfuzzer]
+max_len = 65536
diff --git a/src/libsystemd-network/fuzz-lldp-rx.c b/src/libsystemd-network/fuzz-lldp-rx.c
new file mode 100644
index 0000000..6419075
--- /dev/null
+++ b/src/libsystemd-network/fuzz-lldp-rx.c
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <unistd.h>
+
+#include "sd-event.h"
+#include "sd-lldp-rx.h"
+
+#include "fd-util.h"
+#include "fuzz.h"
+#include "lldp-network.h"
+
+static int test_fd[2] = { -1, -1 };
+
+int lldp_network_bind_raw_socket(int ifindex) {
+        if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
+                return -errno;
+
+        return test_fd[0];
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_lldp_rx_unrefp) sd_lldp_rx *lldp_rx = NULL;
+
+        if (outside_size_range(size, 0, 2048))
+                return 0;
+
+        assert_se(sd_event_new(&e) == 0);
+        assert_se(sd_lldp_rx_new(&lldp_rx) >= 0);
+        assert_se(sd_lldp_rx_set_ifindex(lldp_rx, 42) >= 0);
+        assert_se(sd_lldp_rx_attach_event(lldp_rx, e, 0) >= 0);
+        assert_se(sd_lldp_rx_start(lldp_rx) >= 0);
+
+        assert_se(write(test_fd[1], data, size) == (ssize_t) size);
+        assert_se(sd_event_run(e, 0) >= 0);
+
+        assert_se(sd_lldp_rx_stop(lldp_rx) >= 0);
+        assert_se(sd_lldp_rx_detach_event(lldp_rx) >= 0);
+        test_fd[1] = safe_close(test_fd[1]);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/fuzz-lldp-rx.options b/src/libsystemd-network/fuzz-lldp-rx.options
new file mode 100644
index 0000000..60bd9b0
--- /dev/null
+++ b/src/libsystemd-network/fuzz-lldp-rx.options
@@ -0,0 +1,2 @@
+[libfuzzer]
+max_len = 2048
diff --git a/src/libsystemd-network/fuzz-ndisc-rs.c b/src/libsystemd-network/fuzz-ndisc-rs.c
new file mode 100644
index 0000000..c8eacc6
--- /dev/null
+++ b/src/libsystemd-network/fuzz-ndisc-rs.c
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <arpa/inet.h>
+#include <netinet/icmp6.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "icmp6-util.h"
+#include "fuzz.h"
+#include "sd-ndisc.h"
+#include "socket-util.h"
+#include "ndisc-internal.h"
+
+static int test_fd[2] = { -1, -1 };
+
+int icmp6_bind_router_solicitation(int index) {
+        assert_se(socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) >= 0);
+        return test_fd[0];
+}
+
+int icmp6_bind_router_advertisement(int index) {
+        return -ENOSYS;
+}
+
+static struct in6_addr dummy_link_local = {
+        .s6_addr = {
+                0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x12, 0x34, 0x56, 0xff, 0xfe, 0x78, 0x9a, 0xbc,
+        },
+};
+
+int icmp6_receive(
+                int fd,
+                void *iov_base,
+                size_t iov_len,
+                struct in6_addr *ret_sender,
+                triple_timestamp *ret_timestamp) {
+
+        assert_se(read(fd, iov_base, iov_len) == (ssize_t) iov_len);
+
+        if (ret_timestamp)
+                triple_timestamp_get(ret_timestamp);
+
+        if (ret_sender)
+                *ret_sender = dummy_link_local;
+
+        return 0;
+}
+
+int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr) {
+        return 0;
+}
+
+int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
+        struct ether_addr mac_addr = {
+                .ether_addr_octet = {'A', 'B', 'C', '1', '2', '3'}
+        };
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_ndisc_unrefp) sd_ndisc *nd = NULL;
+
+        if (outside_size_range(size, 0, 2048))
+                return 0;
+
+        assert_se(sd_event_new(&e) >= 0);
+        assert_se(sd_ndisc_new(&nd) >= 0);
+        assert_se(sd_ndisc_attach_event(nd, e, 0) >= 0);
+        assert_se(sd_ndisc_set_ifindex(nd, 42) >= 0);
+        assert_se(sd_ndisc_set_mac(nd, &mac_addr) >= 0);
+        assert_se(sd_ndisc_start(nd) >= 0);
+        assert_se(write(test_fd[1], data, size) == (ssize_t) size);
+        (void) sd_event_run(e, UINT64_MAX);
+        assert_se(sd_ndisc_stop(nd) >= 0);
+        close(test_fd[1]);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/fuzz-ndisc-rs.options b/src/libsystemd-network/fuzz-ndisc-rs.options
new file mode 100644
index 0000000..60bd9b0
--- /dev/null
+++ b/src/libsystemd-network/fuzz-ndisc-rs.options
@@ -0,0 +1,2 @@
+[libfuzzer]
+max_len = 2048
diff --git a/src/libsystemd-network/icmp6-util.c b/src/libsystemd-network/icmp6-util.c
new file mode 100644
index 0000000..d3ee7c4
--- /dev/null
+++ b/src/libsystemd-network/icmp6-util.c
@@ -0,0 +1,221 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <netinet/icmp6.h>
+#include <netinet/in.h>
+#include <netinet/ip6.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <net/if.h>
+#include <linux/if_packet.h>
+
+#include "fd-util.h"
+#include "icmp6-util.h"
+#include "in-addr-util.h"
+#include "io-util.h"
+#include "socket-util.h"
+
+#define IN6ADDR_ALL_ROUTERS_MULTICAST_INIT \
+        { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02 } } }
+
+#define IN6ADDR_ALL_NODES_MULTICAST_INIT \
+        { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } } }
+
+static int icmp6_bind_router_message(const struct icmp6_filter *filter,
+                                     const struct ipv6_mreq *mreq) {
+        int ifindex = mreq->ipv6mr_interface;
+        _cleanup_close_ int s = -1;
+        int r;
+
+        assert(filter);
+        assert(mreq);
+
+        s = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC | SOCK_NONBLOCK, IPPROTO_ICMPV6);
+        if (s < 0)
+                return -errno;
+
+        if (setsockopt(s, IPPROTO_ICMPV6, ICMP6_FILTER, filter, sizeof(*filter)) < 0)
+                return -errno;
+
+        if (setsockopt(s, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, mreq, sizeof(*mreq)) < 0)
+                return -errno;
+
+        /* RFC 3315, section 6.7, bullet point 2 may indicate that an
+           IPV6_PKTINFO socket option also applies for ICMPv6 multicast.
+           Empirical experiments indicates otherwise and therefore an
+           IPV6_MULTICAST_IF socket option is used here instead */
+        r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_IF, ifindex);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, false);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, 255);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, IPPROTO_IPV6, IPV6_UNICAST_HOPS, 255);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, SOL_IPV6, IPV6_RECVHOPLIMIT, true);
+        if (r < 0)
+                return r;
+
+        r = setsockopt_int(s, SOL_SOCKET, SO_TIMESTAMP, true);
+        if (r < 0)
+                return r;
+
+        r = socket_bind_to_ifindex(s, ifindex);
+        if (r < 0)
+                return r;
+
+        return TAKE_FD(s);
+}
+
+int icmp6_bind_router_solicitation(int ifindex) {
+        struct icmp6_filter filter = {};
+        struct ipv6_mreq mreq = {
+                .ipv6mr_multiaddr = IN6ADDR_ALL_NODES_MULTICAST_INIT,
+                .ipv6mr_interface = ifindex,
+        };
+
+        ICMP6_FILTER_SETBLOCKALL(&filter);
+        ICMP6_FILTER_SETPASS(ND_ROUTER_ADVERT, &filter);
+
+        return icmp6_bind_router_message(&filter, &mreq);
+}
+
+int icmp6_bind_router_advertisement(int ifindex) {
+        struct icmp6_filter filter = {};
+        struct ipv6_mreq mreq = {
+                .ipv6mr_multiaddr = IN6ADDR_ALL_ROUTERS_MULTICAST_INIT,
+                .ipv6mr_interface = ifindex,
+        };
+
+        ICMP6_FILTER_SETBLOCKALL(&filter);
+        ICMP6_FILTER_SETPASS(ND_ROUTER_SOLICIT, &filter);
+
+        return icmp6_bind_router_message(&filter, &mreq);
+}
+
+int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr) {
+        struct sockaddr_in6 dst = {
+                .sin6_family = AF_INET6,
+                .sin6_addr = IN6ADDR_ALL_ROUTERS_MULTICAST_INIT,
+        };
+        struct {
+                struct nd_router_solicit rs;
+                struct nd_opt_hdr rs_opt;
+                struct ether_addr rs_opt_mac;
+        } _packed_ rs = {
+                .rs.nd_rs_type = ND_ROUTER_SOLICIT,
+                .rs_opt.nd_opt_type = ND_OPT_SOURCE_LINKADDR,
+                .rs_opt.nd_opt_len = 1,
+        };
+        struct iovec iov = {
+                .iov_base = &rs,
+                .iov_len = sizeof(rs),
+        };
+        struct msghdr msg = {
+                .msg_name = &dst,
+                .msg_namelen = sizeof(dst),
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+        };
+
+        assert(s >= 0);
+        assert(ether_addr);
+
+        rs.rs_opt_mac = *ether_addr;
+
+        if (sendmsg(s, &msg, 0) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int icmp6_receive(
+                int fd,
+                void *buffer,
+                size_t size,
+                struct in6_addr *ret_sender,
+                triple_timestamp *ret_timestamp) {
+
+        /* This needs to be initialized with zero. See #20741. */
+        CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(int)) + /* ttl */
+                         CMSG_SPACE_TIMEVAL) control = {};
+        struct iovec iov = {};
+        union sockaddr_union sa = {};
+        struct msghdr msg = {
+                .msg_name = &sa.sa,
+                .msg_namelen = sizeof(sa),
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+        };
+        struct cmsghdr *cmsg;
+        struct in6_addr addr = {};
+        triple_timestamp t = {};
+        ssize_t len;
+
+        iov = IOVEC_MAKE(buffer, size);
+
+        len = recvmsg_safe(fd, &msg, MSG_DONTWAIT);
+        if (len < 0)
+                return (int) len;
+
+        if ((size_t) len != size)
+                return -EINVAL;
+
+        if (msg.msg_namelen == sizeof(struct sockaddr_in6) &&
+            sa.in6.sin6_family == AF_INET6)  {
+
+                addr = sa.in6.sin6_addr;
+                if (!in6_addr_is_link_local(&addr) && !in6_addr_is_null(&addr))
+                        return -EADDRNOTAVAIL;
+
+        } else if (msg.msg_namelen > 0)
+                return -EPFNOSUPPORT;
+
+        /* namelen == 0 only happens when running the test-suite over a socketpair */
+
+        assert(!(msg.msg_flags & MSG_TRUNC));
+
+        CMSG_FOREACH(cmsg, &msg) {
+                if (cmsg->cmsg_level == SOL_IPV6 &&
+                    cmsg->cmsg_type == IPV6_HOPLIMIT &&
+                    cmsg->cmsg_len == CMSG_LEN(sizeof(int))) {
+                        int hops = *(int*) CMSG_DATA(cmsg);
+
+                        if (hops != 255)
+                                return -EMULTIHOP;
+                }
+
+                if (cmsg->cmsg_level == SOL_SOCKET &&
+                    cmsg->cmsg_type == SO_TIMESTAMP &&
+                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct timeval)))
+                        triple_timestamp_from_realtime(&t, timeval_load((struct timeval*) CMSG_DATA(cmsg)));
+        }
+
+        if (ret_timestamp) {
+                if (triple_timestamp_is_set(&t))
+                        *ret_timestamp = t;
+                else
+                        triple_timestamp_get(ret_timestamp);
+        }
+
+        if (ret_sender)
+                *ret_sender = addr;
+        return 0;
+}
diff --git a/src/libsystemd-network/icmp6-util.h b/src/libsystemd-network/icmp6-util.h
new file mode 100644
index 0000000..0a9ecb4
--- /dev/null
+++ b/src/libsystemd-network/icmp6-util.h
@@ -0,0 +1,28 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2014-2015 Intel Corporation. All rights reserved.
+***/
+
+#include <net/ethernet.h>
+
+#include "time-util.h"
+
+#define IN6ADDR_ALL_ROUTERS_MULTICAST_INIT \
+        { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02 } } }
+
+#define IN6ADDR_ALL_NODES_MULTICAST_INIT \
+        { { { 0xff, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, \
+              0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } } }
+
+int icmp6_bind_router_solicitation(int ifindex);
+int icmp6_bind_router_advertisement(int ifindex);
+int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr);
+int icmp6_receive(
+                int fd,
+                void *buffer,
+                size_t size,
+                struct in6_addr *ret_sender,
+                triple_timestamp *ret_timestamp);
diff --git a/src/libsystemd-network/lldp-neighbor.c b/src/libsystemd-network/lldp-neighbor.c
new file mode 100644
index 0000000..6672409
--- /dev/null
+++ b/src/libsystemd-network/lldp-neighbor.c
@@ -0,0 +1,796 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "alloc-util.h"
+#include "escape.h"
+#include "ether-addr-util.h"
+#include "hexdecoct.h"
+#include "in-addr-util.h"
+#include "lldp-neighbor.h"
+#include "memory-util.h"
+#include "missing_network.h"
+#include "unaligned.h"
+
+static void lldp_neighbor_id_hash_func(const LLDPNeighborID *id, struct siphash *state) {
+        assert(id);
+        assert(state);
+
+        siphash24_compress(id->chassis_id, id->chassis_id_size, state);
+        siphash24_compress(&id->chassis_id_size, sizeof(id->chassis_id_size), state);
+        siphash24_compress(id->port_id, id->port_id_size, state);
+        siphash24_compress(&id->port_id_size, sizeof(id->port_id_size), state);
+}
+
+int lldp_neighbor_id_compare_func(const LLDPNeighborID *x, const LLDPNeighborID *y) {
+        assert(x);
+        assert(y);
+
+        return memcmp_nn(x->chassis_id, x->chassis_id_size, y->chassis_id, y->chassis_id_size)
+            ?: memcmp_nn(x->port_id, x->port_id_size, y->port_id, y->port_id_size);
+}
+
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+        lldp_neighbor_hash_ops,
+        LLDPNeighborID,
+        lldp_neighbor_id_hash_func,
+        lldp_neighbor_id_compare_func,
+        sd_lldp_neighbor,
+        lldp_neighbor_unlink);
+
+int lldp_neighbor_prioq_compare_func(const void *a, const void *b) {
+        const sd_lldp_neighbor *x = a, *y = b;
+
+        assert(x);
+        assert(y);
+
+        return CMP(x->until, y->until);
+}
+
+sd_lldp_neighbor *sd_lldp_neighbor_ref(sd_lldp_neighbor *n) {
+        if (!n)
+                return NULL;
+
+        assert(n->n_ref > 0 || n->lldp_rx);
+        n->n_ref++;
+
+        return n;
+}
+
+static sd_lldp_neighbor *lldp_neighbor_free(sd_lldp_neighbor *n) {
+        if (!n)
+                return NULL;
+
+        free(n->id.port_id);
+        free(n->id.chassis_id);
+        free(n->port_description);
+        free(n->system_name);
+        free(n->system_description);
+        free(n->mud_url);
+        free(n->chassis_id_as_string);
+        free(n->port_id_as_string);
+        return mfree(n);
+}
+
+sd_lldp_neighbor *sd_lldp_neighbor_unref(sd_lldp_neighbor *n) {
+
+        /* Drops one reference from the neighbor. Note that the object is not freed unless it is already unlinked from
+         * the sd_lldp object. */
+
+        if (!n)
+                return NULL;
+
+        assert(n->n_ref > 0);
+        n->n_ref--;
+
+        if (n->n_ref <= 0 && !n->lldp_rx)
+                lldp_neighbor_free(n);
+
+        return NULL;
+}
+
+sd_lldp_neighbor *lldp_neighbor_unlink(sd_lldp_neighbor *n) {
+
+        /* Removes the neighbor object from the LLDP object, and frees it if it also has no other reference. */
+
+        if (!n)
+                return NULL;
+
+        if (!n->lldp_rx)
+                return NULL;
+
+        /* Only remove the neighbor object from the hash table if it's in there, don't complain if it isn't. This is
+         * because we are used as destructor call for hashmap_clear() and thus sometimes are called to de-register
+         * ourselves from the hashtable and sometimes are called after we already are de-registered. */
+
+        (void) hashmap_remove_value(n->lldp_rx->neighbor_by_id, &n->id, n);
+
+        assert_se(prioq_remove(n->lldp_rx->neighbor_by_expiry, n, &n->prioq_idx) >= 0);
+
+        n->lldp_rx = NULL;
+
+        if (n->n_ref <= 0)
+                lldp_neighbor_free(n);
+
+        return NULL;
+}
+
+sd_lldp_neighbor *lldp_neighbor_new(size_t raw_size) {
+        sd_lldp_neighbor *n;
+
+        if (raw_size > SIZE_MAX - ALIGN(sizeof(sd_lldp_neighbor)))
+                return NULL;
+
+        n = malloc0(ALIGN(sizeof(sd_lldp_neighbor)) + raw_size);
+        if (!n)
+                return NULL;
+
+        n->raw_size = raw_size;
+        n->n_ref = 1;
+
+        return n;
+}
+
+static int parse_string(sd_lldp_rx *lldp_rx, char **s, const void *q, size_t n) {
+        const char *p = q;
+        char *k;
+
+        assert(s);
+        assert(p || n == 0);
+
+        if (*s) {
+                log_lldp_rx(lldp_rx, "Found duplicate string, ignoring field.");
+                return 0;
+        }
+
+        /* Strip trailing NULs, just to be nice */
+        while (n > 0 && p[n-1] == 0)
+                n--;
+
+        if (n <= 0) /* Ignore empty strings */
+                return 0;
+
+        /* Look for inner NULs */
+        if (memchr(p, 0, n)) {
+                log_lldp_rx(lldp_rx, "Found inner NUL in string, ignoring field.");
+                return 0;
+        }
+
+        /* Let's escape weird chars, for security reasons */
+        k = cescape_length(p, n);
+        if (!k)
+                return log_oom_debug();
+
+        free(*s);
+        *s = k;
+
+        return 1;
+}
+
+int lldp_neighbor_parse(sd_lldp_neighbor *n) {
+        struct ether_header h;
+        const uint8_t *p;
+        size_t left;
+        int r;
+
+        assert(n);
+
+        if (n->raw_size < sizeof(struct ether_header))
+                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                         "Received truncated packet, ignoring.");
+
+        memcpy(&h, LLDP_NEIGHBOR_RAW(n), sizeof(h));
+
+        if (h.ether_type != htobe16(ETHERTYPE_LLDP))
+                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                         "Received packet with wrong type, ignoring.");
+
+        if (h.ether_dhost[0] != 0x01 ||
+            h.ether_dhost[1] != 0x80 ||
+            h.ether_dhost[2] != 0xc2 ||
+            h.ether_dhost[3] != 0x00 ||
+            h.ether_dhost[4] != 0x00 ||
+            !IN_SET(h.ether_dhost[5], 0x00, 0x03, 0x0e))
+                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                         "Received packet with wrong destination address, ignoring.");
+
+        memcpy(&n->source_address, h.ether_shost, sizeof(struct ether_addr));
+        memcpy(&n->destination_address, h.ether_dhost, sizeof(struct ether_addr));
+
+        p = (const uint8_t*) LLDP_NEIGHBOR_RAW(n) + sizeof(struct ether_header);
+        left = n->raw_size - sizeof(struct ether_header);
+
+        for (;;) {
+                uint8_t type;
+                uint16_t length;
+
+                if (left < 2)
+                        return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                              "TLV lacks header, ignoring.");
+
+                type = p[0] >> 1;
+                length = p[1] + (((uint16_t) (p[0] & 1)) << 8);
+                p += 2, left -= 2;
+
+                if (left < length)
+                        return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                 "TLV truncated, ignoring datagram.");
+
+                switch (type) {
+
+                case SD_LLDP_TYPE_END:
+                        if (length != 0)
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "End marker TLV not zero-sized, ignoring datagram.");
+
+                        /* Note that after processing the SD_LLDP_TYPE_END left could still be > 0
+                         * as the message may contain padding (see IEEE 802.1AB-2016, sec. 8.5.12) */
+
+                        goto end_marker;
+
+                case SD_LLDP_TYPE_CHASSIS_ID:
+                        if (length < 2 || length > 256)
+                                /* includes the chassis subtype, hence one extra byte */
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "Chassis ID field size out of range, ignoring datagram.");
+
+                        if (n->id.chassis_id)
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "Duplicate chassis ID field, ignoring datagram.");
+
+                        n->id.chassis_id = memdup(p, length);
+                        if (!n->id.chassis_id)
+                                return log_oom_debug();
+
+                        n->id.chassis_id_size = length;
+                        break;
+
+                case SD_LLDP_TYPE_PORT_ID:
+                        if (length < 2 || length > 256)
+                                /* includes the port subtype, hence one extra byte */
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "Port ID field size out of range, ignoring datagram.");
+
+                        if (n->id.port_id)
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "Duplicate port ID field, ignoring datagram.");
+
+                        n->id.port_id = memdup(p, length);
+                        if (!n->id.port_id)
+                                return log_oom_debug();
+
+                        n->id.port_id_size = length;
+                        break;
+
+                case SD_LLDP_TYPE_TTL:
+                        if (length != 2)
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "TTL field has wrong size, ignoring datagram.");
+
+                        if (n->has_ttl)
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "Duplicate TTL field, ignoring datagram.");
+
+                        n->ttl = unaligned_read_be16(p);
+                        n->has_ttl = true;
+                        break;
+
+                case SD_LLDP_TYPE_PORT_DESCRIPTION:
+                        r = parse_string(n->lldp_rx, &n->port_description, p, length);
+                        if (r < 0)
+                                return r;
+                        break;
+
+                case SD_LLDP_TYPE_SYSTEM_NAME:
+                        r = parse_string(n->lldp_rx, &n->system_name, p, length);
+                        if (r < 0)
+                                return r;
+                        break;
+
+                case SD_LLDP_TYPE_SYSTEM_DESCRIPTION:
+                        r = parse_string(n->lldp_rx, &n->system_description, p, length);
+                        if (r < 0)
+                                return r;
+                        break;
+
+                case SD_LLDP_TYPE_SYSTEM_CAPABILITIES:
+                        if (length != 4)
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "System capabilities field has wrong size.");
+
+                        n->system_capabilities = unaligned_read_be16(p);
+                        n->enabled_capabilities = unaligned_read_be16(p + 2);
+                        n->has_capabilities = true;
+                        break;
+
+                case SD_LLDP_TYPE_PRIVATE:
+                        if (length < 4)
+                                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                                         "Found private TLV that is too short, ignoring.");
+
+                        /* RFC 8520: MUD URL */
+                        if (memcmp(p, SD_LLDP_OUI_IANA_MUD, sizeof(SD_LLDP_OUI_IANA_MUD)) == 0) {
+                                r = parse_string(n->lldp_rx, &n->mud_url, p + sizeof(SD_LLDP_OUI_IANA_MUD),
+                                                 length - sizeof(SD_LLDP_OUI_IANA_MUD));
+                                if (r < 0)
+                                        return r;
+                        }
+                        break;
+                }
+
+                p += length, left -= length;
+        }
+
+end_marker:
+        if (!n->id.chassis_id || !n->id.port_id || !n->has_ttl)
+                return log_lldp_rx_errno(n->lldp_rx, SYNTHETIC_ERRNO(EBADMSG),
+                                         "One or more mandatory TLV missing in datagram. Ignoring.");
+
+        n->rindex = sizeof(struct ether_header);
+
+        return 0;
+}
+
+void lldp_neighbor_start_ttl(sd_lldp_neighbor *n) {
+        assert(n);
+
+        if (n->ttl > 0) {
+                usec_t base;
+
+                /* Use the packet's timestamp if there is one known */
+                base = triple_timestamp_by_clock(&n->timestamp, CLOCK_BOOTTIME);
+                if (!timestamp_is_set(base))
+                        base = now(CLOCK_BOOTTIME); /* Otherwise, take the current time */
+
+                n->until = usec_add(base, n->ttl * USEC_PER_SEC);
+        } else
+                n->until = 0;
+
+        if (n->lldp_rx)
+                prioq_reshuffle(n->lldp_rx->neighbor_by_expiry, n, &n->prioq_idx);
+}
+
+bool lldp_neighbor_equal(const sd_lldp_neighbor *a, const sd_lldp_neighbor *b) {
+        if (a == b)
+                return true;
+
+        if (!a || !b)
+                return false;
+
+        if (a->raw_size != b->raw_size)
+                return false;
+
+        return memcmp(LLDP_NEIGHBOR_RAW(a), LLDP_NEIGHBOR_RAW(b), a->raw_size) == 0;
+}
+
+int sd_lldp_neighbor_get_source_address(sd_lldp_neighbor *n, struct ether_addr* address) {
+        assert_return(n, -EINVAL);
+        assert_return(address, -EINVAL);
+
+        *address = n->source_address;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_destination_address(sd_lldp_neighbor *n, struct ether_addr* address) {
+        assert_return(n, -EINVAL);
+        assert_return(address, -EINVAL);
+
+        *address = n->destination_address;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_raw(sd_lldp_neighbor *n, const void **ret, size_t *size) {
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+        assert_return(size, -EINVAL);
+
+        *ret = LLDP_NEIGHBOR_RAW(n);
+        *size = n->raw_size;
+
+        return 0;
+}
+
+int sd_lldp_neighbor_get_chassis_id(sd_lldp_neighbor *n, uint8_t *type, const void **ret, size_t *size) {
+        assert_return(n, -EINVAL);
+        assert_return(type, -EINVAL);
+        assert_return(ret, -EINVAL);
+        assert_return(size, -EINVAL);
+
+        assert(n->id.chassis_id_size > 0);
+
+        *type = *(uint8_t*) n->id.chassis_id;
+        *ret = (uint8_t*) n->id.chassis_id + 1;
+        *size = n->id.chassis_id_size - 1;
+
+        return 0;
+}
+
+static int format_mac_address(const void *data, size_t sz, char **ret) {
+        struct ether_addr a;
+        char *k;
+
+        assert(data || sz <= 0);
+
+        if (sz != 7)
+                return 0;
+
+        memcpy(&a, (uint8_t*) data + 1, sizeof(a));
+
+        k = new(char, ETHER_ADDR_TO_STRING_MAX);
+        if (!k)
+                return -ENOMEM;
+
+        *ret = ether_addr_to_string(&a, k);
+        return 1;
+}
+
+static int format_network_address(const void *data, size_t sz, char **ret) {
+        union in_addr_union a;
+        int family, r;
+
+        if (sz == 6 && ((uint8_t*) data)[1] == 1) {
+                memcpy(&a.in, (uint8_t*) data + 2, sizeof(a.in));
+                family = AF_INET;
+        } else if (sz == 18 && ((uint8_t*) data)[1] == 2) {
+                memcpy(&a.in6, (uint8_t*) data + 2, sizeof(a.in6));
+                family = AF_INET6;
+        } else
+                return 0;
+
+        r = in_addr_to_string(family, &a, ret);
+        if (r < 0)
+                return r;
+        return 1;
+}
+
+int sd_lldp_neighbor_get_chassis_id_as_string(sd_lldp_neighbor *n, const char **ret) {
+        char *k;
+        int r;
+
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (n->chassis_id_as_string) {
+                *ret = n->chassis_id_as_string;
+                return 0;
+        }
+
+        assert(n->id.chassis_id_size > 0);
+
+        switch (*(uint8_t*) n->id.chassis_id) {
+
+        case SD_LLDP_CHASSIS_SUBTYPE_CHASSIS_COMPONENT:
+        case SD_LLDP_CHASSIS_SUBTYPE_INTERFACE_ALIAS:
+        case SD_LLDP_CHASSIS_SUBTYPE_PORT_COMPONENT:
+        case SD_LLDP_CHASSIS_SUBTYPE_INTERFACE_NAME:
+        case SD_LLDP_CHASSIS_SUBTYPE_LOCALLY_ASSIGNED:
+                k = cescape_length((char*) n->id.chassis_id + 1, n->id.chassis_id_size - 1);
+                if (!k)
+                        return -ENOMEM;
+
+                goto done;
+
+        case SD_LLDP_CHASSIS_SUBTYPE_MAC_ADDRESS:
+                r = format_mac_address(n->id.chassis_id, n->id.chassis_id_size, &k);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        goto done;
+
+                break;
+
+        case SD_LLDP_CHASSIS_SUBTYPE_NETWORK_ADDRESS:
+                r = format_network_address(n->id.chassis_id, n->id.chassis_id_size, &k);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        goto done;
+
+                break;
+        }
+
+        /* Generic fallback */
+        k = hexmem(n->id.chassis_id, n->id.chassis_id_size);
+        if (!k)
+                return -ENOMEM;
+
+done:
+        *ret = n->chassis_id_as_string = k;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_port_id(sd_lldp_neighbor *n, uint8_t *type, const void **ret, size_t *size) {
+        assert_return(n, -EINVAL);
+        assert_return(type, -EINVAL);
+        assert_return(ret, -EINVAL);
+        assert_return(size, -EINVAL);
+
+        assert(n->id.port_id_size > 0);
+
+        *type = *(uint8_t*) n->id.port_id;
+        *ret = (uint8_t*) n->id.port_id + 1;
+        *size = n->id.port_id_size - 1;
+
+        return 0;
+}
+
+int sd_lldp_neighbor_get_port_id_as_string(sd_lldp_neighbor *n, const char **ret) {
+        char *k;
+        int r;
+
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (n->port_id_as_string) {
+                *ret = n->port_id_as_string;
+                return 0;
+        }
+
+        assert(n->id.port_id_size > 0);
+
+        switch (*(uint8_t*) n->id.port_id) {
+
+        case SD_LLDP_PORT_SUBTYPE_INTERFACE_ALIAS:
+        case SD_LLDP_PORT_SUBTYPE_PORT_COMPONENT:
+        case SD_LLDP_PORT_SUBTYPE_INTERFACE_NAME:
+        case SD_LLDP_PORT_SUBTYPE_LOCALLY_ASSIGNED:
+                k = cescape_length((char*) n->id.port_id + 1, n->id.port_id_size - 1);
+                if (!k)
+                        return -ENOMEM;
+
+                goto done;
+
+        case SD_LLDP_PORT_SUBTYPE_MAC_ADDRESS:
+                r = format_mac_address(n->id.port_id, n->id.port_id_size, &k);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        goto done;
+
+                break;
+
+        case SD_LLDP_PORT_SUBTYPE_NETWORK_ADDRESS:
+                r = format_network_address(n->id.port_id, n->id.port_id_size, &k);
+                if (r < 0)
+                        return r;
+                if (r > 0)
+                        goto done;
+
+                break;
+        }
+
+        /* Generic fallback */
+        k = hexmem(n->id.port_id, n->id.port_id_size);
+        if (!k)
+                return -ENOMEM;
+
+done:
+        *ret = n->port_id_as_string = k;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_ttl(sd_lldp_neighbor *n, uint16_t *ret_sec) {
+        assert_return(n, -EINVAL);
+        assert_return(ret_sec, -EINVAL);
+
+        *ret_sec = n->ttl;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_system_name(sd_lldp_neighbor *n, const char **ret) {
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!n->system_name)
+                return -ENODATA;
+
+        *ret = n->system_name;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_system_description(sd_lldp_neighbor *n, const char **ret) {
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!n->system_description)
+                return -ENODATA;
+
+        *ret = n->system_description;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_port_description(sd_lldp_neighbor *n, const char **ret) {
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!n->port_description)
+                return -ENODATA;
+
+        *ret = n->port_description;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_mud_url(sd_lldp_neighbor *n, const char **ret) {
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!n->mud_url)
+                return -ENODATA;
+
+        *ret = n->mud_url;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_system_capabilities(sd_lldp_neighbor *n, uint16_t *ret) {
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!n->has_capabilities)
+                return -ENODATA;
+
+        *ret = n->system_capabilities;
+        return 0;
+}
+
+int sd_lldp_neighbor_get_enabled_capabilities(sd_lldp_neighbor *n, uint16_t *ret) {
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!n->has_capabilities)
+                return -ENODATA;
+
+        *ret = n->enabled_capabilities;
+        return 0;
+}
+
+int sd_lldp_neighbor_from_raw(sd_lldp_neighbor **ret, const void *raw, size_t raw_size) {
+        _cleanup_(sd_lldp_neighbor_unrefp) sd_lldp_neighbor *n = NULL;
+        int r;
+
+        assert_return(ret, -EINVAL);
+        assert_return(raw || raw_size <= 0, -EINVAL);
+
+        n = lldp_neighbor_new(raw_size);
+        if (!n)
+                return -ENOMEM;
+
+        memcpy_safe(LLDP_NEIGHBOR_RAW(n), raw, raw_size);
+
+        r = lldp_neighbor_parse(n);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(n);
+
+        return r;
+}
+
+int sd_lldp_neighbor_tlv_rewind(sd_lldp_neighbor *n) {
+        assert_return(n, -EINVAL);
+
+        assert(n->raw_size >= sizeof(struct ether_header));
+        n->rindex = sizeof(struct ether_header);
+
+        return n->rindex < n->raw_size;
+}
+
+int sd_lldp_neighbor_tlv_next(sd_lldp_neighbor *n) {
+        size_t length;
+
+        assert_return(n, -EINVAL);
+
+        if (n->rindex == n->raw_size) /* EOF */
+                return -ESPIPE;
+
+        if (n->rindex + 2 > n->raw_size) /* Truncated message */
+                return -EBADMSG;
+
+        length = LLDP_NEIGHBOR_TLV_LENGTH(n);
+        if (n->rindex + 2 + length > n->raw_size)
+                return -EBADMSG;
+
+        n->rindex += 2 + length;
+        return n->rindex < n->raw_size;
+}
+
+int sd_lldp_neighbor_tlv_get_type(sd_lldp_neighbor *n, uint8_t *type) {
+        assert_return(n, -EINVAL);
+        assert_return(type, -EINVAL);
+
+        if (n->rindex == n->raw_size) /* EOF */
+                return -ESPIPE;
+
+        if (n->rindex + 2 > n->raw_size)
+                return -EBADMSG;
+
+        *type = LLDP_NEIGHBOR_TLV_TYPE(n);
+        return 0;
+}
+
+int sd_lldp_neighbor_tlv_is_type(sd_lldp_neighbor *n, uint8_t type) {
+        uint8_t k;
+        int r;
+
+        assert_return(n, -EINVAL);
+
+        r = sd_lldp_neighbor_tlv_get_type(n, &k);
+        if (r < 0)
+                return r;
+
+        return type == k;
+}
+
+int sd_lldp_neighbor_tlv_get_oui(sd_lldp_neighbor *n, uint8_t oui[_SD_ARRAY_STATIC 3], uint8_t *subtype) {
+        const uint8_t *d;
+        size_t length;
+        int r;
+
+        assert_return(n, -EINVAL);
+        assert_return(oui, -EINVAL);
+        assert_return(subtype, -EINVAL);
+
+        r = sd_lldp_neighbor_tlv_is_type(n, SD_LLDP_TYPE_PRIVATE);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -ENXIO;
+
+        length = LLDP_NEIGHBOR_TLV_LENGTH(n);
+        if (length < 4)
+                return -EBADMSG;
+
+        if (n->rindex + 2 + length > n->raw_size)
+                return -EBADMSG;
+
+        d = LLDP_NEIGHBOR_TLV_DATA(n);
+        memcpy(oui, d, 3);
+        *subtype = d[3];
+
+        return 0;
+}
+
+int sd_lldp_neighbor_tlv_is_oui(sd_lldp_neighbor *n, const uint8_t oui[_SD_ARRAY_STATIC 3], uint8_t subtype) {
+        uint8_t k[3], st;
+        int r;
+
+        r = sd_lldp_neighbor_tlv_get_oui(n, k, &st);
+        if (r == -ENXIO)
+                return 0;
+        if (r < 0)
+                return r;
+
+        return memcmp(k, oui, 3) == 0 && st == subtype;
+}
+
+int sd_lldp_neighbor_tlv_get_raw(sd_lldp_neighbor *n, const void **ret, size_t *size) {
+        size_t length;
+
+        assert_return(n, -EINVAL);
+        assert_return(ret, -EINVAL);
+        assert_return(size, -EINVAL);
+
+        /* Note that this returns the full TLV, including the TLV header */
+
+        if (n->rindex + 2 > n->raw_size)
+                return -EBADMSG;
+
+        length = LLDP_NEIGHBOR_TLV_LENGTH(n);
+        if (n->rindex + 2 + length > n->raw_size)
+                return -EBADMSG;
+
+        *ret = (uint8_t*) LLDP_NEIGHBOR_RAW(n) + n->rindex;
+        *size = length + 2;
+
+        return 0;
+}
+
+int sd_lldp_neighbor_get_timestamp(sd_lldp_neighbor *n, clockid_t clock, uint64_t *ret) {
+        assert_return(n, -EINVAL);
+        assert_return(TRIPLE_TIMESTAMP_HAS_CLOCK(clock), -EOPNOTSUPP);
+        assert_return(clock_supported(clock), -EOPNOTSUPP);
+        assert_return(ret, -EINVAL);
+
+        if (!triple_timestamp_is_set(&n->timestamp))
+                return -ENODATA;
+
+        *ret = triple_timestamp_by_clock(&n->timestamp, clock);
+        return 0;
+}
diff --git a/src/libsystemd-network/lldp-neighbor.h b/src/libsystemd-network/lldp-neighbor.h
new file mode 100644
index 0000000..016286b
--- /dev/null
+++ b/src/libsystemd-network/lldp-neighbor.h
@@ -0,0 +1,92 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <sys/types.h>
+
+#include "sd-lldp-rx.h"
+
+#include "hash-funcs.h"
+#include "lldp-rx-internal.h"
+#include "time-util.h"
+
+typedef struct LLDPNeighborID {
+        /* The spec calls this an "MSAP identifier" */
+        void *chassis_id;
+        size_t chassis_id_size;
+
+        void *port_id;
+        size_t port_id_size;
+} LLDPNeighborID;
+
+struct sd_lldp_neighbor {
+        /* Neighbor objects stay around as long as they are linked into an "sd_lldp_rx" object or n_ref > 0. */
+        sd_lldp_rx *lldp_rx;
+        unsigned n_ref;
+
+        triple_timestamp timestamp;
+
+        usec_t until;
+        unsigned prioq_idx;
+
+        struct ether_addr source_address;
+        struct ether_addr destination_address;
+
+        LLDPNeighborID id;
+
+        /* The raw packet size. The data is appended to the object, accessible via LLDP_NEIGHBOR_RAW() */
+        size_t raw_size;
+
+        /* The current read index for the iterative TLV interface */
+        size_t rindex;
+
+        /* And a couple of fields parsed out. */
+        bool has_ttl:1;
+        bool has_capabilities:1;
+        bool has_port_vlan_id:1;
+
+        uint16_t ttl;
+
+        uint16_t system_capabilities;
+        uint16_t enabled_capabilities;
+
+        char *port_description;
+        char *system_name;
+        char *system_description;
+        char *mud_url;
+
+        uint16_t port_vlan_id;
+
+        char *chassis_id_as_string;
+        char *port_id_as_string;
+};
+
+static inline void *LLDP_NEIGHBOR_RAW(const sd_lldp_neighbor *n) {
+        return (uint8_t*) n + ALIGN(sizeof(sd_lldp_neighbor));
+}
+
+static inline uint8_t LLDP_NEIGHBOR_TLV_TYPE(const sd_lldp_neighbor *n) {
+        return ((uint8_t*) LLDP_NEIGHBOR_RAW(n))[n->rindex] >> 1;
+}
+
+static inline size_t LLDP_NEIGHBOR_TLV_LENGTH(const sd_lldp_neighbor *n) {
+        uint8_t *p;
+
+        p = (uint8_t*) LLDP_NEIGHBOR_RAW(n) + n->rindex;
+        return p[1] + (((size_t) (p[0] & 1)) << 8);
+}
+
+static inline void* LLDP_NEIGHBOR_TLV_DATA(const sd_lldp_neighbor *n) {
+        return ((uint8_t*) LLDP_NEIGHBOR_RAW(n)) + n->rindex + 2;
+}
+
+extern const struct hash_ops lldp_neighbor_hash_ops;
+int lldp_neighbor_id_compare_func(const LLDPNeighborID *x, const LLDPNeighborID *y);
+int lldp_neighbor_prioq_compare_func(const void *a, const void *b);
+
+sd_lldp_neighbor *lldp_neighbor_unlink(sd_lldp_neighbor *n);
+sd_lldp_neighbor *lldp_neighbor_new(size_t raw_size);
+int lldp_neighbor_parse(sd_lldp_neighbor *n);
+void lldp_neighbor_start_ttl(sd_lldp_neighbor *n);
+bool lldp_neighbor_equal(const sd_lldp_neighbor *a, const sd_lldp_neighbor *b);
diff --git a/src/libsystemd-network/lldp-network.c b/src/libsystemd-network/lldp-network.c
new file mode 100644
index 0000000..24edc37
--- /dev/null
+++ b/src/libsystemd-network/lldp-network.c
@@ -0,0 +1,70 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <linux/filter.h>
+#include <netinet/if_ether.h>
+
+#include "fd-util.h"
+#include "lldp-network.h"
+#include "missing_network.h"
+#include "socket-util.h"
+
+int lldp_network_bind_raw_socket(int ifindex) {
+        static const struct sock_filter filter[] = {
+                BPF_STMT(BPF_LD + BPF_W + BPF_ABS, offsetof(struct ethhdr, h_dest)),      /* A <- 4 bytes of destination MAC */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0180c200, 1, 0),                    /* A != 01:80:c2:00 */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_dest) + 4),  /* A <- remaining 2 bytes of destination MAC */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0000, 3, 0),                        /* A != 00:00 */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x0003, 2, 0),                        /* A != 00:03 */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, 0x000e, 1, 0),                        /* A != 00:0e */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
+                BPF_STMT(BPF_LD + BPF_H + BPF_ABS, offsetof(struct ethhdr, h_proto)),     /* A <- protocol */
+                BPF_JUMP(BPF_JMP + BPF_JEQ + BPF_K, ETHERTYPE_LLDP, 1, 0),                /* A != ETHERTYPE_LLDP */
+                BPF_STMT(BPF_RET + BPF_K, 0),                                             /* drop packet */
+                BPF_STMT(BPF_RET + BPF_K, UINT32_MAX),                                    /* accept packet */
+        };
+        static const struct sock_fprog fprog = {
+                .len = ELEMENTSOF(filter),
+                .filter = (struct sock_filter*) filter,
+        };
+        struct packet_mreq mreq = {
+                .mr_ifindex = ifindex,
+                .mr_type = PACKET_MR_MULTICAST,
+                .mr_alen = ETH_ALEN,
+                .mr_address = { 0x01, 0x80, 0xC2, 0x00, 0x00, 0x00 }
+        };
+        union sockaddr_union saddrll = {
+                .ll.sll_family = AF_PACKET,
+                .ll.sll_ifindex = ifindex,
+        };
+        _cleanup_close_ int fd = -1;
+
+        assert(ifindex > 0);
+
+        fd = socket(AF_PACKET, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK,
+                    htobe16(ETHERTYPE_LLDP));
+        if (fd < 0)
+                return -errno;
+
+        if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &fprog, sizeof(fprog)) < 0)
+                return -errno;
+
+        /* customer bridge */
+        if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
+                return -errno;
+
+        /* non TPMR bridge */
+        mreq.mr_address[ETH_ALEN - 1] = 0x03;
+        if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
+                return -errno;
+
+        /* nearest bridge */
+        mreq.mr_address[ETH_ALEN - 1] = 0x0E;
+        if (setsockopt(fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq)) < 0)
+                return -errno;
+
+        if (bind(fd, &saddrll.sa, sizeof(saddrll.ll)) < 0)
+                return -errno;
+
+        return TAKE_FD(fd);
+}
diff --git a/src/libsystemd-network/lldp-network.h b/src/libsystemd-network/lldp-network.h
new file mode 100644
index 0000000..bc69b32
--- /dev/null
+++ b/src/libsystemd-network/lldp-network.h
@@ -0,0 +1,6 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-event.h"
+
+int lldp_network_bind_raw_socket(int ifindex);
diff --git a/src/libsystemd-network/lldp-rx-internal.h b/src/libsystemd-network/lldp-rx-internal.h
new file mode 100644
index 0000000..83d0bc4
--- /dev/null
+++ b/src/libsystemd-network/lldp-rx-internal.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "sd-event.h"
+#include "sd-lldp-rx.h"
+
+#include "hashmap.h"
+#include "network-common.h"
+#include "prioq.h"
+
+struct sd_lldp_rx {
+        unsigned n_ref;
+
+        int ifindex;
+        char *ifname;
+        int fd;
+
+        sd_event *event;
+        int64_t event_priority;
+        sd_event_source *io_event_source;
+        sd_event_source *timer_event_source;
+
+        Prioq *neighbor_by_expiry;
+        Hashmap *neighbor_by_id;
+
+        uint64_t neighbors_max;
+
+        sd_lldp_rx_callback_t callback;
+        void *userdata;
+
+        uint16_t capability_mask;
+
+        struct ether_addr filter_address;
+};
+
+const char* lldp_rx_event_to_string(sd_lldp_rx_event_t e) _const_;
+sd_lldp_rx_event_t lldp_rx_event_from_string(const char *s) _pure_;
+
+#define log_lldp_rx_errno(lldp_rx, error, fmt, ...)     \
+        log_interface_prefix_full_errno(                \
+                "LLDP Rx: ",                            \
+                sd_lldp_rx, lldp_rx,                    \
+                error, fmt, ##__VA_ARGS__)
+#define log_lldp_rx(lldp_rx, fmt, ...)                  \
+        log_interface_prefix_full_errno_zerook(         \
+                "LLDP Rx: ",                            \
+                sd_lldp_rx, lldp_rx,                    \
+                0, fmt, ##__VA_ARGS__)
diff --git a/src/libsystemd-network/meson.build b/src/libsystemd-network/meson.build
new file mode 100644
index 0000000..ff59ec0
--- /dev/null
+++ b/src/libsystemd-network/meson.build
@@ -0,0 +1,133 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+sources = files(
+        'arp-util.c',
+        'arp-util.h',
+        'dhcp-client-internal.h',
+        'dhcp-identifier.c',
+        'dhcp-identifier.h',
+        'dhcp-internal.h',
+        'dhcp-lease-internal.h',
+        'dhcp-network.c',
+        'dhcp-option.c',
+        'dhcp-packet.c',
+        'dhcp-protocol.h',
+        'dhcp-server-internal.h',
+        'dhcp6-internal.h',
+        'dhcp6-lease-internal.h',
+        'dhcp6-network.c',
+        'dhcp6-option.c',
+        'dhcp6-option.h',
+        'dhcp6-protocol.c',
+        'dhcp6-protocol.h',
+        'icmp6-util.c',
+        'icmp6-util.h',
+        'lldp-neighbor.c',
+        'lldp-neighbor.h',
+        'lldp-network.c',
+        'lldp-network.h',
+        'lldp-rx-internal.h',
+        'ndisc-internal.h',
+        'ndisc-router.c',
+        'ndisc-router.h',
+        'network-common.c',
+        'network-common.h',
+        'network-internal.c',
+        'network-internal.h',
+        'radv-internal.h',
+        'sd-dhcp-client.c',
+        'sd-dhcp-lease.c',
+        'sd-dhcp-server.c',
+        'sd-dhcp6-client.c',
+        'sd-dhcp6-lease.c',
+        'sd-ipv4acd.c',
+        'sd-ipv4ll.c',
+        'sd-lldp-rx.c',
+        'sd-lldp-tx.c',
+        'sd-ndisc.c',
+        'sd-radv.c',
+)
+
+libsystemd_network = static_library(
+        'systemd-network',
+        sources,
+        include_directories : includes,
+        build_by_default : false)
+
+libsystemd_network_includes = [includes, include_directories('.')]
+
+############################################################
+
+tests += [
+        [files('test-dhcp-option.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-sd-dhcp-lease.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-dhcp-client.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-dhcp-server.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-ipv4ll.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-ipv4ll-manual.c'),
+         [libshared,
+          libsystemd_network],
+         [], [], '', 'manual'],
+
+        [files('test-acd.c'),
+         [libshared,
+          libsystemd_network],
+         [], [], '', 'manual'],
+
+        [files('test-ndisc-rs.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-ndisc-ra.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-dhcp6-client.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('test-lldp-rx.c'),
+         [libshared,
+          libsystemd_network]],
+]
+
+fuzzers += [
+        [files('fuzz-dhcp-client.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('fuzz-dhcp6-client.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('fuzz-dhcp-server.c'),
+         [libsystemd_network,
+          libshared]],
+
+        [files('fuzz-dhcp-server-relay.c'),
+         [libsystemd_network,
+          libshared]],
+
+        [files('fuzz-lldp-rx.c'),
+         [libshared,
+          libsystemd_network]],
+
+        [files('fuzz-ndisc-rs.c'),
+         [libshared,
+          libsystemd_network]],
+]
diff --git a/src/libsystemd-network/ndisc-internal.h b/src/libsystemd-network/ndisc-internal.h
new file mode 100644
index 0000000..615de0d
--- /dev/null
+++ b/src/libsystemd-network/ndisc-internal.h
@@ -0,0 +1,51 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include "sd-ndisc.h"
+
+#include "network-common.h"
+#include "time-util.h"
+
+#define NDISC_ROUTER_SOLICITATION_INTERVAL (4U * USEC_PER_SEC)
+#define NDISC_MAX_ROUTER_SOLICITATION_INTERVAL (3600U * USEC_PER_SEC)
+#define NDISC_MAX_ROUTER_SOLICITATIONS 3U
+
+struct sd_ndisc {
+        unsigned n_ref;
+
+        int ifindex;
+        char *ifname;
+        int fd;
+
+        sd_event *event;
+        int event_priority;
+
+        struct ether_addr mac_addr;
+
+        sd_event_source *recv_event_source;
+        sd_event_source *timeout_event_source;
+        sd_event_source *timeout_no_ra;
+
+        usec_t retransmit_time;
+
+        sd_ndisc_callback_t callback;
+        void *userdata;
+};
+
+const char* ndisc_event_to_string(sd_ndisc_event_t e) _const_;
+sd_ndisc_event_t ndisc_event_from_string(const char *s) _pure_;
+
+#define log_ndisc_errno(ndisc, error, fmt, ...)         \
+        log_interface_prefix_full_errno(                \
+                "NDISC: ",                              \
+                sd_ndisc, ndisc,                        \
+                error, fmt, ##__VA_ARGS__)
+#define log_ndisc(ndisc, fmt, ...)                      \
+        log_interface_prefix_full_errno_zerook(         \
+                "NDISC: ",                              \
+                sd_ndisc, ndisc,                        \
+                0, fmt, ##__VA_ARGS__)
diff --git a/src/libsystemd-network/ndisc-router.c b/src/libsystemd-network/ndisc-router.c
new file mode 100644
index 0000000..e4cbf71
--- /dev/null
+++ b/src/libsystemd-network/ndisc-router.c
@@ -0,0 +1,717 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include <netinet/icmp6.h>
+
+#include "sd-ndisc.h"
+
+#include "alloc-util.h"
+#include "dns-domain.h"
+#include "hostname-util.h"
+#include "memory-util.h"
+#include "missing_network.h"
+#include "ndisc-internal.h"
+#include "ndisc-router.h"
+#include "strv.h"
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_ndisc_router, sd_ndisc_router, mfree);
+
+sd_ndisc_router *ndisc_router_new(size_t raw_size) {
+        sd_ndisc_router *rt;
+
+        if (raw_size > SIZE_MAX - ALIGN(sizeof(sd_ndisc_router)))
+                return NULL;
+
+        rt = malloc0(ALIGN(sizeof(sd_ndisc_router)) + raw_size);
+        if (!rt)
+                return NULL;
+
+        rt->raw_size = raw_size;
+        rt->n_ref = 1;
+
+        return rt;
+}
+
+int sd_ndisc_router_get_address(sd_ndisc_router *rt, struct in6_addr *ret_addr) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret_addr, -EINVAL);
+
+        if (in6_addr_is_null(&rt->address))
+                return -ENODATA;
+
+        *ret_addr = rt->address;
+        return 0;
+}
+
+int sd_ndisc_router_get_timestamp(sd_ndisc_router *rt, clockid_t clock, uint64_t *ret) {
+        assert_return(rt, -EINVAL);
+        assert_return(TRIPLE_TIMESTAMP_HAS_CLOCK(clock), -EOPNOTSUPP);
+        assert_return(clock_supported(clock), -EOPNOTSUPP);
+        assert_return(ret, -EINVAL);
+
+        if (!triple_timestamp_is_set(&rt->timestamp))
+                return -ENODATA;
+
+        *ret = triple_timestamp_by_clock(&rt->timestamp, clock);
+        return 0;
+}
+
+int sd_ndisc_router_get_raw(sd_ndisc_router *rt, const void **ret, size_t *size) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+        assert_return(size, -EINVAL);
+
+        *ret = NDISC_ROUTER_RAW(rt);
+        *size = rt->raw_size;
+
+        return 0;
+}
+
+int ndisc_router_parse(sd_ndisc *nd, sd_ndisc_router *rt) {
+        struct nd_router_advert *a;
+        const uint8_t *p;
+        bool has_mtu = false, has_flag_extension = false;
+        size_t left;
+
+        assert(rt);
+
+        if (rt->raw_size < sizeof(struct nd_router_advert))
+                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                       "Too small to be a router advertisement, ignoring.");
+
+        /* Router advertisement packets are neatly aligned to 64bit boundaries, hence we can access them directly */
+        a = NDISC_ROUTER_RAW(rt);
+
+        if (a->nd_ra_type != ND_ROUTER_ADVERT)
+                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                       "Received ND packet that is not a router advertisement, ignoring.");
+
+        if (a->nd_ra_code != 0)
+                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                       "Received ND packet with wrong RA code, ignoring.");
+
+        rt->hop_limit = a->nd_ra_curhoplimit;
+        rt->flags = a->nd_ra_flags_reserved; /* the first 8bit */
+        rt->lifetime = be16toh(a->nd_ra_router_lifetime);
+
+        rt->preference = (rt->flags >> 3) & 3;
+        if (!IN_SET(rt->preference, SD_NDISC_PREFERENCE_LOW, SD_NDISC_PREFERENCE_HIGH))
+                rt->preference = SD_NDISC_PREFERENCE_MEDIUM;
+
+        p = (const uint8_t*) NDISC_ROUTER_RAW(rt) + sizeof(struct nd_router_advert);
+        left = rt->raw_size - sizeof(struct nd_router_advert);
+
+        for (;;) {
+                uint8_t type;
+                size_t length;
+
+                if (left == 0)
+                        break;
+
+                if (left < 2)
+                        return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                               "Option lacks header, ignoring datagram.");
+
+                type = p[0];
+                length = p[1] * 8;
+
+                if (length == 0)
+                        return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                               "Zero-length option, ignoring datagram.");
+                if (left < length)
+                        return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                               "Option truncated, ignoring datagram.");
+
+                switch (type) {
+
+                case SD_NDISC_OPTION_PREFIX_INFORMATION:
+
+                        if (length != 4*8)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                                       "Prefix option of invalid size, ignoring datagram.");
+
+                        if (p[2] > 128)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                                       "Bad prefix length, ignoring datagram.");
+
+                        break;
+
+                case SD_NDISC_OPTION_MTU: {
+                        uint32_t m;
+
+                        if (has_mtu) {
+                                log_ndisc(nd, "MTU option specified twice, ignoring.");
+                                break;
+                        }
+
+                        if (length != 8)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                                       "MTU option of invalid size, ignoring datagram.");
+
+                        m = be32toh(*(uint32_t*) (p + 4));
+                        if (m >= IPV6_MIN_MTU) /* ignore invalidly small MTUs */
+                                rt->mtu = m;
+
+                        has_mtu = true;
+                        break;
+                }
+
+                case SD_NDISC_OPTION_ROUTE_INFORMATION:
+                        if (length < 1*8 || length > 3*8)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                                       "Route information option of invalid size, ignoring datagram.");
+
+                        if (p[2] > 128)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                                       "Bad route prefix length, ignoring datagram.");
+
+                        break;
+
+                case SD_NDISC_OPTION_RDNSS:
+                        if (length < 3*8 || (length % (2*8)) != 1*8)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG), "RDNSS option has invalid size.");
+
+                        break;
+
+                case SD_NDISC_OPTION_FLAGS_EXTENSION:
+
+                        if (has_flag_extension) {
+                                log_ndisc(nd, "Flags extension option specified twice, ignoring.");
+                                break;
+                        }
+
+                        if (length < 1*8)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                                       "Flags extension option has invalid size.");
+
+                        /* Add in the additional flags bits */
+                        rt->flags |=
+                                ((uint64_t) p[2] << 8) |
+                                ((uint64_t) p[3] << 16) |
+                                ((uint64_t) p[4] << 24) |
+                                ((uint64_t) p[5] << 32) |
+                                ((uint64_t) p[6] << 40) |
+                                ((uint64_t) p[7] << 48);
+
+                        has_flag_extension = true;
+                        break;
+
+                case SD_NDISC_OPTION_DNSSL:
+                        if (length < 2*8)
+                                return log_ndisc_errno(nd, SYNTHETIC_ERRNO(EBADMSG),
+                                                       "DNSSL option has invalid size.");
+
+                        break;
+                }
+
+                p += length, left -= length;
+        }
+
+        rt->rindex = sizeof(struct nd_router_advert);
+        return 0;
+}
+
+int sd_ndisc_router_get_hop_limit(sd_ndisc_router *rt, uint8_t *ret) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        *ret = rt->hop_limit;
+        return 0;
+}
+
+int sd_ndisc_router_get_flags(sd_ndisc_router *rt, uint64_t *ret_flags) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret_flags, -EINVAL);
+
+        *ret_flags = rt->flags;
+        return 0;
+}
+
+int sd_ndisc_router_get_lifetime(sd_ndisc_router *rt, uint16_t *ret_lifetime) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret_lifetime, -EINVAL);
+
+        *ret_lifetime = rt->lifetime;
+        return 0;
+}
+
+int sd_ndisc_router_get_preference(sd_ndisc_router *rt, unsigned *ret) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        *ret = rt->preference;
+        return 0;
+}
+
+int sd_ndisc_router_get_mtu(sd_ndisc_router *rt, uint32_t *ret) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (rt->mtu <= 0)
+                return -ENODATA;
+
+        *ret = rt->mtu;
+        return 0;
+}
+
+int sd_ndisc_router_option_rewind(sd_ndisc_router *rt) {
+        assert_return(rt, -EINVAL);
+
+        assert(rt->raw_size >= sizeof(struct nd_router_advert));
+        rt->rindex = sizeof(struct nd_router_advert);
+
+        return rt->rindex < rt->raw_size;
+}
+
+int sd_ndisc_router_option_next(sd_ndisc_router *rt) {
+        size_t length;
+
+        assert_return(rt, -EINVAL);
+
+        if (rt->rindex == rt->raw_size) /* EOF */
+                return -ESPIPE;
+
+        if (rt->rindex + 2 > rt->raw_size) /* Truncated message */
+                return -EBADMSG;
+
+        length = NDISC_ROUTER_OPTION_LENGTH(rt);
+        if (rt->rindex + length > rt->raw_size)
+                return -EBADMSG;
+
+        rt->rindex += length;
+        return rt->rindex < rt->raw_size;
+}
+
+int sd_ndisc_router_option_get_type(sd_ndisc_router *rt, uint8_t *ret) {
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (rt->rindex == rt->raw_size) /* EOF */
+                return -ESPIPE;
+
+        if (rt->rindex + 2 > rt->raw_size) /* Truncated message */
+                return -EBADMSG;
+
+        *ret = NDISC_ROUTER_OPTION_TYPE(rt);
+        return 0;
+}
+
+int sd_ndisc_router_option_is_type(sd_ndisc_router *rt, uint8_t type) {
+        uint8_t k;
+        int r;
+
+        assert_return(rt, -EINVAL);
+
+        r = sd_ndisc_router_option_get_type(rt, &k);
+        if (r < 0)
+                return r;
+
+        return type == k;
+}
+
+int sd_ndisc_router_option_get_raw(sd_ndisc_router *rt, const void **ret, size_t *size) {
+        size_t length;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+        assert_return(size, -EINVAL);
+
+        /* Note that this returns the full option, including the option header */
+
+        if (rt->rindex + 2 > rt->raw_size)
+                return -EBADMSG;
+
+        length = NDISC_ROUTER_OPTION_LENGTH(rt);
+        if (rt->rindex + length > rt->raw_size)
+                return -EBADMSG;
+
+        *ret = (uint8_t*) NDISC_ROUTER_RAW(rt) + rt->rindex;
+        *size = length;
+
+        return 0;
+}
+
+static int get_prefix_info(sd_ndisc_router *rt, struct nd_opt_prefix_info **ret) {
+        struct nd_opt_prefix_info *ri;
+        size_t length;
+        int r;
+
+        assert(rt);
+        assert(ret);
+
+        r = sd_ndisc_router_option_is_type(rt, SD_NDISC_OPTION_PREFIX_INFORMATION);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EMEDIUMTYPE;
+
+        length = NDISC_ROUTER_OPTION_LENGTH(rt);
+        if (length != sizeof(struct nd_opt_prefix_info))
+                return -EBADMSG;
+
+        ri = (struct nd_opt_prefix_info*) ((uint8_t*) NDISC_ROUTER_RAW(rt) + rt->rindex);
+        if (ri->nd_opt_pi_prefix_len > 128)
+                return -EBADMSG;
+
+        *ret = ri;
+        return 0;
+}
+
+int sd_ndisc_router_prefix_get_valid_lifetime(sd_ndisc_router *rt, uint32_t *ret) {
+        struct nd_opt_prefix_info *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_prefix_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        *ret = be32toh(ri->nd_opt_pi_valid_time);
+        return 0;
+}
+
+int sd_ndisc_router_prefix_get_preferred_lifetime(sd_ndisc_router *rt, uint32_t *ret) {
+        struct nd_opt_prefix_info *pi;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_prefix_info(rt, &pi);
+        if (r < 0)
+                return r;
+
+        *ret = be32toh(pi->nd_opt_pi_preferred_time);
+        return 0;
+}
+
+int sd_ndisc_router_prefix_get_flags(sd_ndisc_router *rt, uint8_t *ret) {
+        struct nd_opt_prefix_info *pi;
+        uint8_t flags;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_prefix_info(rt, &pi);
+        if (r < 0)
+                return r;
+
+        flags = pi->nd_opt_pi_flags_reserved;
+
+        if ((flags & ND_OPT_PI_FLAG_AUTO) && (pi->nd_opt_pi_prefix_len != 64)) {
+                log_ndisc(NULL, "Invalid prefix length, ignoring prefix for stateless autoconfiguration.");
+                flags &= ~ND_OPT_PI_FLAG_AUTO;
+        }
+
+        *ret = flags;
+        return 0;
+}
+
+int sd_ndisc_router_prefix_get_address(sd_ndisc_router *rt, struct in6_addr *ret_addr) {
+        struct nd_opt_prefix_info *pi;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret_addr, -EINVAL);
+
+        r = get_prefix_info(rt, &pi);
+        if (r < 0)
+                return r;
+
+        *ret_addr = pi->nd_opt_pi_prefix;
+        return 0;
+}
+
+int sd_ndisc_router_prefix_get_prefixlen(sd_ndisc_router *rt, unsigned *ret) {
+        struct nd_opt_prefix_info *pi;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_prefix_info(rt, &pi);
+        if (r < 0)
+                return r;
+
+        if (pi->nd_opt_pi_prefix_len > 128)
+                return -EBADMSG;
+
+        *ret = pi->nd_opt_pi_prefix_len;
+        return 0;
+}
+
+static int get_route_info(sd_ndisc_router *rt, uint8_t **ret) {
+        uint8_t *ri;
+        size_t length;
+        int r;
+
+        assert(rt);
+        assert(ret);
+
+        r = sd_ndisc_router_option_is_type(rt, SD_NDISC_OPTION_ROUTE_INFORMATION);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EMEDIUMTYPE;
+
+        length = NDISC_ROUTER_OPTION_LENGTH(rt);
+        if (length < 1*8 || length > 3*8)
+                return -EBADMSG;
+
+        ri = (uint8_t*) NDISC_ROUTER_RAW(rt) + rt->rindex;
+
+        if (ri[2] > 128)
+                return -EBADMSG;
+
+        *ret = ri;
+        return 0;
+}
+
+int sd_ndisc_router_route_get_lifetime(sd_ndisc_router *rt, uint32_t *ret) {
+        uint8_t *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_route_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        *ret = be32toh(*(uint32_t*) (ri + 4));
+        return 0;
+}
+
+int sd_ndisc_router_route_get_address(sd_ndisc_router *rt, struct in6_addr *ret_addr) {
+        uint8_t *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret_addr, -EINVAL);
+
+        r = get_route_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        zero(*ret_addr);
+        memcpy(ret_addr, ri + 8, NDISC_ROUTER_OPTION_LENGTH(rt) - 8);
+
+        return 0;
+}
+
+int sd_ndisc_router_route_get_prefixlen(sd_ndisc_router *rt, unsigned *ret) {
+        uint8_t *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_route_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        *ret = ri[2];
+        return 0;
+}
+
+int sd_ndisc_router_route_get_preference(sd_ndisc_router *rt, unsigned *ret) {
+        uint8_t *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_route_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        *ret = (ri[3] >> 3) & 3;
+        if (!IN_SET(*ret, SD_NDISC_PREFERENCE_LOW, SD_NDISC_PREFERENCE_HIGH))
+                *ret = SD_NDISC_PREFERENCE_MEDIUM;
+
+        return 0;
+}
+
+static int get_rdnss_info(sd_ndisc_router *rt, uint8_t **ret) {
+        size_t length;
+        int r;
+
+        assert(rt);
+        assert(ret);
+
+        r = sd_ndisc_router_option_is_type(rt, SD_NDISC_OPTION_RDNSS);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EMEDIUMTYPE;
+
+        length = NDISC_ROUTER_OPTION_LENGTH(rt);
+        if (length < 3*8 || (length % (2*8)) != 1*8)
+                return -EBADMSG;
+
+        *ret = (uint8_t*) NDISC_ROUTER_RAW(rt) + rt->rindex;
+        return 0;
+}
+
+int sd_ndisc_router_rdnss_get_addresses(sd_ndisc_router *rt, const struct in6_addr **ret) {
+        uint8_t *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_rdnss_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        *ret = (const struct in6_addr*) (ri + 8);
+        return (NDISC_ROUTER_OPTION_LENGTH(rt) - 8) / 16;
+}
+
+int sd_ndisc_router_rdnss_get_lifetime(sd_ndisc_router *rt, uint32_t *ret) {
+        uint8_t *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_rdnss_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        *ret = be32toh(*(uint32_t*) (ri + 4));
+        return 0;
+}
+
+static int get_dnssl_info(sd_ndisc_router *rt, uint8_t **ret) {
+        size_t length;
+        int r;
+
+        assert(rt);
+        assert(ret);
+
+        r = sd_ndisc_router_option_is_type(rt, SD_NDISC_OPTION_DNSSL);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return -EMEDIUMTYPE;
+
+        length = NDISC_ROUTER_OPTION_LENGTH(rt);
+        if (length < 2*8)
+                return -EBADMSG;
+
+        *ret = (uint8_t*) NDISC_ROUTER_RAW(rt) + rt->rindex;
+        return 0;
+}
+
+int sd_ndisc_router_dnssl_get_domains(sd_ndisc_router *rt, char ***ret) {
+        _cleanup_strv_free_ char **l = NULL;
+        _cleanup_free_ char *e = NULL;
+        size_t n = 0, left;
+        uint8_t *ri, *p;
+        bool first = true;
+        int r;
+        unsigned k = 0;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        r = get_dnssl_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        p = ri + 8;
+        left = NDISC_ROUTER_OPTION_LENGTH(rt) - 8;
+
+        for (;;) {
+                if (left == 0) {
+
+                        if (n > 0) /* Not properly NUL terminated */
+                                return -EBADMSG;
+
+                        break;
+                }
+
+                if (*p == 0) {
+                        /* Found NUL termination */
+
+                        if (n > 0) {
+                                _cleanup_free_ char *normalized = NULL;
+
+                                e[n] = 0;
+                                r = dns_name_normalize(e, 0, &normalized);
+                                if (r < 0)
+                                        return r;
+
+                                /* Ignore the root domain name or "localhost" and friends */
+                                if (!is_localhost(normalized) &&
+                                    !dns_name_is_root(normalized)) {
+
+                                        if (strv_push(&l, normalized) < 0)
+                                                return -ENOMEM;
+
+                                        normalized = NULL;
+                                        k++;
+                                }
+                        }
+
+                        n = 0;
+                        first = true;
+                        p++, left--;
+                        continue;
+                }
+
+                /* Check for compression (which is not allowed) */
+                if (*p > 63)
+                        return -EBADMSG;
+
+                if (1U + *p + 1U > left)
+                        return -EBADMSG;
+
+                if (!GREEDY_REALLOC(e, n + !first + DNS_LABEL_ESCAPED_MAX + 1U))
+                        return -ENOMEM;
+
+                if (first)
+                        first = false;
+                else
+                        e[n++] = '.';
+
+                r = dns_label_escape((char*) p+1, *p, e + n, DNS_LABEL_ESCAPED_MAX);
+                if (r < 0)
+                        return r;
+
+                n += r;
+
+                left -= 1 + *p;
+                p += 1 + *p;
+        }
+
+        if (strv_isempty(l)) {
+                *ret = NULL;
+                return 0;
+        }
+
+        *ret = TAKE_PTR(l);
+
+        return k;
+}
+
+int sd_ndisc_router_dnssl_get_lifetime(sd_ndisc_router *rt, uint32_t *ret_sec) {
+        uint8_t *ri;
+        int r;
+
+        assert_return(rt, -EINVAL);
+        assert_return(ret_sec, -EINVAL);
+
+        r = get_dnssl_info(rt, &ri);
+        if (r < 0)
+                return r;
+
+        *ret_sec = be32toh(*(uint32_t*) (ri + 4));
+        return 0;
+}
diff --git a/src/libsystemd-network/ndisc-router.h b/src/libsystemd-network/ndisc-router.h
new file mode 100644
index 0000000..f5293c9
--- /dev/null
+++ b/src/libsystemd-network/ndisc-router.h
@@ -0,0 +1,48 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include "sd-ndisc.h"
+
+#include "time-util.h"
+
+struct sd_ndisc_router {
+        unsigned n_ref;
+
+        triple_timestamp timestamp;
+        struct in6_addr address;
+
+        /* The raw packet size. The data is appended to the object, accessible via NDIS_ROUTER_RAW() */
+        size_t raw_size;
+
+        /* The current read index for the iterative option interface */
+        size_t rindex;
+
+        uint64_t flags;
+        unsigned preference;
+        uint16_t lifetime;
+
+        uint8_t hop_limit;
+        uint32_t mtu;
+};
+
+static inline void* NDISC_ROUTER_RAW(const sd_ndisc_router *rt) {
+        return (uint8_t*) rt + ALIGN(sizeof(sd_ndisc_router));
+}
+
+static inline void *NDISC_ROUTER_OPTION_DATA(const sd_ndisc_router *rt) {
+        return ((uint8_t*) NDISC_ROUTER_RAW(rt)) + rt->rindex;
+}
+
+static inline uint8_t NDISC_ROUTER_OPTION_TYPE(const sd_ndisc_router *rt) {
+        return ((uint8_t*) NDISC_ROUTER_OPTION_DATA(rt))[0];
+}
+static inline size_t NDISC_ROUTER_OPTION_LENGTH(const sd_ndisc_router *rt) {
+        return ((uint8_t*) NDISC_ROUTER_OPTION_DATA(rt))[1] * 8;
+}
+
+sd_ndisc_router *ndisc_router_new(size_t raw_size);
+int ndisc_router_parse(sd_ndisc *nd, sd_ndisc_router *rt);
diff --git a/src/libsystemd-network/network-common.c b/src/libsystemd-network/network-common.c
new file mode 100644
index 0000000..b8b4ecd
--- /dev/null
+++ b/src/libsystemd-network/network-common.c
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "format-util.h"
+#include "network-common.h"
+
+int get_ifname(int ifindex, char **ifname) {
+        assert(ifname);
+
+        /* This sets ifname only when it is not set yet. */
+
+        if (*ifname)
+                return 0;
+
+        return format_ifname_alloc(ifindex, ifname);
+}
diff --git a/src/libsystemd-network/network-common.h b/src/libsystemd-network/network-common.h
new file mode 100644
index 0000000..2b0e3b5
--- /dev/null
+++ b/src/libsystemd-network/network-common.h
@@ -0,0 +1,30 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include "log-link.h"
+
+#define log_interface_prefix_full_errno_zerook(prefix, type, val, error, fmt, ...) \
+        ({                                                              \
+                int _e = (error);                                       \
+                if (DEBUG_LOGGING) {                                    \
+                        const char *_n = NULL;                          \
+                        type *_v = (val);                               \
+                                                                        \
+                        if (_v)                                         \
+                                (void) type##_get_ifname(_v, &_n);      \
+                        log_interface_full_errno_zerook(                \
+                                _n, LOG_DEBUG, _e, prefix fmt,          \
+                                ##__VA_ARGS__);                         \
+                }                                                       \
+                -ERRNO_VALUE(_e);                                       \
+        })
+
+#define log_interface_prefix_full_errno(prefix, type, val, error, fmt, ...) \
+        ({                                                              \
+                int _error = (error);                                   \
+                ASSERT_NON_ZERO(_error);                                \
+                log_interface_prefix_full_errno_zerook(                 \
+                        prefix, type, val, _error, fmt, ##__VA_ARGS__); \
+        })
+
+int get_ifname(int ifindex, char **ifname);
diff --git a/src/libsystemd-network/network-internal.c b/src/libsystemd-network/network-internal.c
new file mode 100644
index 0000000..cd32a72
--- /dev/null
+++ b/src/libsystemd-network/network-internal.c
@@ -0,0 +1,238 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <arpa/inet.h>
+#include <linux/if.h>
+#include <netinet/ether.h>
+
+#include "sd-ndisc.h"
+
+#include "alloc-util.h"
+#include "dhcp-lease-internal.h"
+#include "extract-word.h"
+#include "hexdecoct.h"
+#include "log.h"
+#include "network-internal.h"
+#include "parse-util.h"
+
+size_t serialize_in_addrs(FILE *f,
+                          const struct in_addr *addresses,
+                          size_t size,
+                          bool *with_leading_space,
+                          bool (*predicate)(const struct in_addr *addr)) {
+        assert(f);
+        assert(addresses);
+
+        size_t count = 0;
+        bool _space = false;
+        if (!with_leading_space)
+                with_leading_space = &_space;
+
+        for (size_t i = 0; i < size; i++) {
+                if (predicate && !predicate(&addresses[i]))
+                        continue;
+
+                if (*with_leading_space)
+                        fputc(' ', f);
+                fputs(IN4_ADDR_TO_STRING(&addresses[i]), f);
+                count++;
+                *with_leading_space = true;
+        }
+
+        return count;
+}
+
+int deserialize_in_addrs(struct in_addr **ret, const char *string) {
+        _cleanup_free_ struct in_addr *addresses = NULL;
+        int size = 0;
+
+        assert(ret);
+        assert(string);
+
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
+                struct in_addr *new_addresses;
+                int r;
+
+                r = extract_first_word(&string, &word, NULL, 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                new_addresses = reallocarray(addresses, size + 1, sizeof(struct in_addr));
+                if (!new_addresses)
+                        return -ENOMEM;
+                else
+                        addresses = new_addresses;
+
+                r = inet_pton(AF_INET, word, &(addresses[size]));
+                if (r <= 0)
+                        continue;
+
+                size++;
+        }
+
+        *ret = size > 0 ? TAKE_PTR(addresses) : NULL;
+
+        return size;
+}
+
+void serialize_in6_addrs(FILE *f, const struct in6_addr *addresses, size_t size, bool *with_leading_space) {
+        assert(f);
+        assert(addresses);
+        assert(size);
+
+        bool _space = false;
+        if (!with_leading_space)
+                with_leading_space = &_space;
+
+        for (size_t i = 0; i < size; i++) {
+                if (*with_leading_space)
+                        fputc(' ', f);
+                fputs(IN6_ADDR_TO_STRING(&addresses[i]), f);
+                *with_leading_space = true;
+        }
+}
+
+int deserialize_in6_addrs(struct in6_addr **ret, const char *string) {
+        _cleanup_free_ struct in6_addr *addresses = NULL;
+        int size = 0;
+
+        assert(ret);
+        assert(string);
+
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
+                struct in6_addr *new_addresses;
+                int r;
+
+                r = extract_first_word(&string, &word, NULL, 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                new_addresses = reallocarray(addresses, size + 1, sizeof(struct in6_addr));
+                if (!new_addresses)
+                        return -ENOMEM;
+                else
+                        addresses = new_addresses;
+
+                r = inet_pton(AF_INET6, word, &(addresses[size]));
+                if (r <= 0)
+                        continue;
+
+                size++;
+        }
+
+        *ret = TAKE_PTR(addresses);
+
+        return size;
+}
+
+void serialize_dhcp_routes(FILE *f, const char *key, sd_dhcp_route **routes, size_t size) {
+        assert(f);
+        assert(key);
+        assert(routes);
+        assert(size);
+
+        fprintf(f, "%s=", key);
+
+        for (size_t i = 0; i < size; i++) {
+                struct in_addr dest, gw;
+                uint8_t length;
+
+                assert_se(sd_dhcp_route_get_destination(routes[i], &dest) >= 0);
+                assert_se(sd_dhcp_route_get_gateway(routes[i], &gw) >= 0);
+                assert_se(sd_dhcp_route_get_destination_prefix_length(routes[i], &length) >= 0);
+
+                fprintf(f, "%s,%s%s",
+                        IN4_ADDR_PREFIX_TO_STRING(&dest, length),
+                        IN4_ADDR_TO_STRING(&gw),
+                        i < size - 1 ? " ": "");
+        }
+
+        fputs("\n", f);
+}
+
+int deserialize_dhcp_routes(struct sd_dhcp_route **ret, size_t *ret_size, const char *string) {
+        _cleanup_free_ struct sd_dhcp_route *routes = NULL;
+        size_t size = 0;
+
+        assert(ret);
+        assert(ret_size);
+        assert(string);
+
+         /* WORD FORMAT: dst_ip/dst_prefixlen,gw_ip */
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
+                char *tok, *tok_end;
+                unsigned n;
+                int r;
+
+                r = extract_first_word(&string, &word, NULL, 0);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        break;
+
+                if (!GREEDY_REALLOC(routes, size + 1))
+                        return -ENOMEM;
+
+                tok = word;
+
+                /* get the subnet */
+                tok_end = strchr(tok, '/');
+                if (!tok_end)
+                        continue;
+                *tok_end = '\0';
+
+                r = inet_aton(tok, &routes[size].dst_addr);
+                if (r == 0)
+                        continue;
+
+                tok = tok_end + 1;
+
+                /* get the prefixlen */
+                tok_end = strchr(tok, ',');
+                if (!tok_end)
+                        continue;
+
+                *tok_end = '\0';
+
+                r = safe_atou(tok, &n);
+                if (r < 0 || n > 32)
+                        continue;
+
+                routes[size].dst_prefixlen = (uint8_t) n;
+                tok = tok_end + 1;
+
+                /* get the gateway */
+                r = inet_aton(tok, &routes[size].gw_addr);
+                if (r == 0)
+                        continue;
+
+                size++;
+        }
+
+        *ret_size = size;
+        *ret = TAKE_PTR(routes);
+
+        return 0;
+}
+
+int serialize_dhcp_option(FILE *f, const char *key, const void *data, size_t size) {
+        _cleanup_free_ char *hex_buf = NULL;
+
+        assert(f);
+        assert(key);
+        assert(data);
+
+        hex_buf = hexmem(data, size);
+        if (!hex_buf)
+                return -ENOMEM;
+
+        fprintf(f, "%s=%s\n", key, hex_buf);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/network-internal.h b/src/libsystemd-network/network-internal.h
new file mode 100644
index 0000000..5aa225e
--- /dev/null
+++ b/src/libsystemd-network/network-internal.h
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "sd-dhcp-lease.h"
+
+size_t serialize_in_addrs(FILE *f,
+                          const struct in_addr *addresses,
+                          size_t size,
+                          bool *with_leading_space,
+                          bool (*predicate)(const struct in_addr *addr));
+int deserialize_in_addrs(struct in_addr **addresses, const char *string);
+void serialize_in6_addrs(FILE *f, const struct in6_addr *addresses,
+                         size_t size,
+                         bool *with_leading_space);
+int deserialize_in6_addrs(struct in6_addr **addresses, const char *string);
+
+/* don't include "dhcp-lease-internal.h" as it causes conflicts between netinet/ip.h and linux/ip.h */
+struct sd_dhcp_route;
+struct sd_dhcp_lease;
+
+void serialize_dhcp_routes(FILE *f, const char *key, struct sd_dhcp_route **routes, size_t size);
+int deserialize_dhcp_routes(struct sd_dhcp_route **ret, size_t *ret_size, const char *string);
+
+/* It is not necessary to add deserialize_dhcp_option(). Use unhexmem() instead. */
+int serialize_dhcp_option(FILE *f, const char *key, const void *data, size_t size);
+
+int dhcp_lease_save(sd_dhcp_lease *lease, const char *lease_file);
+int dhcp_lease_load(sd_dhcp_lease **ret, const char *lease_file);
diff --git a/src/libsystemd-network/radv-internal.h b/src/libsystemd-network/radv-internal.h
new file mode 100644
index 0000000..1a26875
--- /dev/null
+++ b/src/libsystemd-network/radv-internal.h
@@ -0,0 +1,183 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+/***
+  Copyright © 2017 Intel Corporation. All rights reserved.
+***/
+
+#include "sd-radv.h"
+
+#include "list.h"
+#include "network-common.h"
+#include "sparse-endian.h"
+#include "time-util.h"
+
+/* RFC 4861 section 6.2.1.
+ * MaxRtrAdvInterval
+ * The maximum time allowed between sending unsolicited multicast Router Advertisements from the
+ * interface, in seconds. MUST be no less than 4 seconds and no greater than 1800 seconds.
+ * Default: 600 seconds */
+#define RADV_MIN_MAX_TIMEOUT_USEC                 (4 * USEC_PER_SEC)
+#define RADV_MAX_MAX_TIMEOUT_USEC                 (1800 * USEC_PER_SEC)
+#define RADV_DEFAULT_MAX_TIMEOUT_USEC             (600 * USEC_PER_SEC)
+/* RFC 4861 section 6.2.1.
+ * MinRtrAdvInterval
+ * The minimum time allowed between sending unsolicited multicast Router Advertisements from the
+ * interface, in seconds. MUST be no less than 3 seconds and no greater than .75 * MaxRtrAdvInterval.
+ * Default: 0.33 * MaxRtrAdvInterval If MaxRtrAdvInterval >= 9 seconds; otherwise, the Default is
+ * MaxRtrAdvInterval (Note, this should be a typo. We use 0.75 * MaxRtrAdvInterval). */
+#define RADV_MIN_MIN_TIMEOUT_USEC                 (3 * USEC_PER_SEC)
+/* RFC 4861 section 6.2.4.
+ * AdvDefaultLifetime
+ * The value to be placed in the Router Lifetime field of Router Advertisements sent from the interface,
+ * in seconds. MUST be either zero or between MaxRtrAdvInterval and 9000 seconds. A value of zero
+ * indicates that the router is not to be used as a default router. These limits may be overridden by
+ * specific documents that describe how IPv6 operates over different link layers. For instance, in a
+ * point-to-point link the peers may have enough information about the number and status of devices at
+ * the other end so that advertisements are needed less frequently.
+ * Default: 3 * MaxRtrAdvInterval */
+#define RADV_MIN_ROUTER_LIFETIME_USEC             RADV_MIN_MAX_TIMEOUT_USEC
+#define RADV_MAX_ROUTER_LIFETIME_USEC             (9000 * USEC_PER_SEC)
+#define RADV_DEFAULT_ROUTER_LIFETIME_USEC         (3 * RADV_DEFAULT_MAX_TIMEOUT_USEC)
+/* draft-ietf-6man-slaac-renum-02 section 4.1.1.
+ * AdvPreferredLifetime: max(AdvDefaultLifetime, 3 * MaxRtrAdvInterval)
+ * AdvValidLifetime: 2 * AdvPreferredLifetime */
+#define RADV_DEFAULT_PREFERRED_LIFETIME_USEC      CONST_MAX(RADV_DEFAULT_ROUTER_LIFETIME_USEC, 3 * RADV_DEFAULT_MAX_TIMEOUT_USEC)
+#define RADV_DEFAULT_VALID_LIFETIME_USEC          (2 * RADV_DEFAULT_PREFERRED_LIFETIME_USEC)
+/* RFC 4861 section 10.
+ * MAX_INITIAL_RTR_ADVERT_INTERVAL  16 seconds
+ * MAX_INITIAL_RTR_ADVERTISEMENTS    3 transmissions
+ * MAX_FINAL_RTR_ADVERTISEMENTS      3 transmissions
+ * MIN_DELAY_BETWEEN_RAS             3 seconds
+ * MAX_RA_DELAY_TIME                .5 seconds */
+#define RADV_MAX_INITIAL_RTR_ADVERT_INTERVAL_USEC (16 * USEC_PER_SEC)
+#define RADV_MAX_INITIAL_RTR_ADVERTISEMENTS       3
+#define RADV_MAX_FINAL_RTR_ADVERTISEMENTS         3
+#define RADV_MIN_DELAY_BETWEEN_RAS                3
+#define RADV_MAX_RA_DELAY_TIME_USEC               (500 * USEC_PER_MSEC)
+
+#define RADV_OPT_ROUTE_INFORMATION                24
+#define RADV_OPT_RDNSS                            25
+#define RADV_OPT_DNSSL                            31
+
+enum RAdvState {
+        RADV_STATE_IDLE                      = 0,
+        RADV_STATE_ADVERTISING               = 1,
+};
+typedef enum RAdvState RAdvState;
+
+struct sd_radv_opt_dns {
+        uint8_t type;
+        uint8_t length;
+        uint16_t reserved;
+        be32_t lifetime;
+} _packed_;
+
+struct sd_radv {
+        unsigned n_ref;
+        RAdvState state;
+
+        int ifindex;
+        char *ifname;
+
+        sd_event *event;
+        int event_priority;
+
+        struct ether_addr mac_addr;
+        uint8_t hop_limit;
+        uint8_t flags;
+        uint32_t mtu;
+        usec_t lifetime_usec; /* timespan */
+
+        int fd;
+        unsigned ra_sent;
+        sd_event_source *recv_event_source;
+        sd_event_source *timeout_event_source;
+
+        unsigned n_prefixes;
+        LIST_HEAD(sd_radv_prefix, prefixes);
+
+        unsigned n_route_prefixes;
+        LIST_HEAD(sd_radv_route_prefix, route_prefixes);
+
+        size_t n_rdnss;
+        struct sd_radv_opt_dns *rdnss;
+        struct sd_radv_opt_dns *dnssl;
+};
+
+#define radv_prefix_opt__contents {             \
+        uint8_t type;                           \
+        uint8_t length;                         \
+        uint8_t prefixlen;                      \
+        uint8_t flags;                          \
+        be32_t lifetime_valid;                  \
+        be32_t lifetime_preferred;              \
+        uint32_t reserved;                      \
+        struct in6_addr in6_addr;               \
+}
+
+struct radv_prefix_opt radv_prefix_opt__contents;
+
+/* We need the opt substructure to be packed, because we use it in send(). But
+ * if we use _packed_, this means that the structure cannot be used directly in
+ * normal code in general, because the fields might not be properly aligned.
+ * But in this particular case, the structure is defined in a way that gives
+ * proper alignment, even without the explicit _packed_ attribute. To appease
+ * the compiler we use the "unpacked" structure, but we also verify that
+ * structure contains no holes, so offsets are the same when _packed_ is used.
+ */
+struct radv_prefix_opt__packed radv_prefix_opt__contents _packed_;
+assert_cc(sizeof(struct radv_prefix_opt) == sizeof(struct radv_prefix_opt__packed));
+
+struct sd_radv_prefix {
+        unsigned n_ref;
+
+        struct radv_prefix_opt opt;
+
+        LIST_FIELDS(struct sd_radv_prefix, prefix);
+
+        /* These are timespans, NOT points in time. */
+        usec_t lifetime_valid_usec;
+        usec_t lifetime_preferred_usec;
+        /* These are points in time specified with clock_boottime_or_monotonic(), NOT timespans. */
+        usec_t valid_until;
+        usec_t preferred_until;
+};
+
+#define radv_route_prefix_opt__contents {       \
+        uint8_t type;                           \
+        uint8_t length;                         \
+        uint8_t prefixlen;                      \
+        uint8_t flags_reserved;                 \
+        be32_t  lifetime;                       \
+        struct in6_addr in6_addr;               \
+}
+
+struct radv_route_prefix_opt radv_route_prefix_opt__contents;
+
+struct radv_route_prefix_opt__packed radv_route_prefix_opt__contents _packed_;
+assert_cc(sizeof(struct radv_route_prefix_opt) == sizeof(struct radv_route_prefix_opt__packed));
+
+struct sd_radv_route_prefix {
+        unsigned n_ref;
+
+        struct radv_route_prefix_opt opt;
+
+        LIST_FIELDS(struct sd_radv_route_prefix, prefix);
+
+        /* This is a timespan, NOT a point in time. */
+        usec_t lifetime_usec;
+        /* This is a point in time specified with clock_boottime_or_monotonic(), NOT a timespan. */
+        usec_t valid_until;
+};
+
+#define log_radv_errno(radv, error, fmt, ...)           \
+        log_interface_prefix_full_errno(                \
+                "RADV: ",                               \
+                sd_radv, radv,                          \
+                error, fmt, ##__VA_ARGS__)
+#define log_radv(radv, fmt, ...)                        \
+        log_interface_prefix_full_errno_zerook(         \
+                "RADV: ",                               \
+                sd_radv, radv,                          \
+                0, fmt, ##__VA_ARGS__)
diff --git a/src/libsystemd-network/sd-dhcp-client.c b/src/libsystemd-network/sd-dhcp-client.c
new file mode 100644
index 0000000..b755c12
--- /dev/null
+++ b/src/libsystemd-network/sd-dhcp-client.c
@@ -0,0 +1,2222 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <net/ethernet.h>
+#include <net/if_arp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <linux/if_infiniband.h>
+
+#include "sd-dhcp-client.h"
+
+#include "alloc-util.h"
+#include "dhcp-identifier.h"
+#include "dhcp-internal.h"
+#include "dhcp-lease-internal.h"
+#include "dhcp-protocol.h"
+#include "dns-domain.h"
+#include "ether-addr-util.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "hostname-util.h"
+#include "io-util.h"
+#include "memory-util.h"
+#include "network-common.h"
+#include "random-util.h"
+#include "set.h"
+#include "sort-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "time-util.h"
+#include "utf8.h"
+#include "web-util.h"
+
+#define MAX_CLIENT_ID_LEN (sizeof(uint32_t) + MAX_DUID_LEN)  /* Arbitrary limit */
+#define MAX_MAC_ADDR_LEN CONST_MAX(INFINIBAND_ALEN, ETH_ALEN)
+
+#define RESTART_AFTER_NAK_MIN_USEC (1 * USEC_PER_SEC)
+#define RESTART_AFTER_NAK_MAX_USEC (30 * USEC_PER_MINUTE)
+
+#define TRANSIENT_FAILURE_ATTEMPTS 3 /* Arbitrary limit: how many attempts are considered enough to report
+                                      * transient failure. */
+
+typedef struct sd_dhcp_client_id {
+        uint8_t type;
+        union {
+                struct {
+                        /* 0: Generic (non-LL) (RFC 2132) */
+                        uint8_t data[MAX_CLIENT_ID_LEN];
+                } _packed_ gen;
+                struct {
+                        /* 1: Ethernet Link-Layer (RFC 2132) */
+                        uint8_t haddr[ETH_ALEN];
+                } _packed_ eth;
+                struct {
+                        /* 2 - 254: ARP/Link-Layer (RFC 2132) */
+                        uint8_t haddr[0];
+                } _packed_ ll;
+                struct {
+                        /* 255: Node-specific (RFC 4361) */
+                        be32_t iaid;
+                        struct duid duid;
+                } _packed_ ns;
+                struct {
+                        uint8_t data[MAX_CLIENT_ID_LEN];
+                } _packed_ raw;
+        };
+} _packed_ sd_dhcp_client_id;
+
+struct sd_dhcp_client {
+        unsigned n_ref;
+
+        DHCPState state;
+        sd_event *event;
+        int event_priority;
+        sd_event_source *timeout_resend;
+        int ifindex;
+        char *ifname;
+        int fd;
+        uint16_t port;
+        union sockaddr_union link;
+        sd_event_source *receive_message;
+        bool request_broadcast;
+        Set *req_opts;
+        bool anonymize;
+        be32_t last_addr;
+        struct hw_addr_data hw_addr;
+        struct hw_addr_data bcast_addr;
+        uint16_t arp_type;
+        sd_dhcp_client_id client_id;
+        size_t client_id_len;
+        char *hostname;
+        char *vendor_class_identifier;
+        char *mudurl;
+        char **user_class;
+        uint32_t mtu;
+        uint32_t fallback_lease_lifetime;
+        uint32_t xid;
+        usec_t start_time;
+        usec_t t1_time;
+        usec_t t2_time;
+        usec_t expire_time;
+        uint64_t attempt;
+        uint64_t max_attempts;
+        OrderedHashmap *extra_options;
+        OrderedHashmap *vendor_options;
+        usec_t request_sent;
+        sd_event_source *timeout_t1;
+        sd_event_source *timeout_t2;
+        sd_event_source *timeout_expire;
+        sd_dhcp_client_callback_t callback;
+        void *userdata;
+        sd_dhcp_lease *lease;
+        usec_t start_delay;
+        int ip_service_type;
+
+        /* Ignore ifindex when generating iaid. See dhcp_identifier_set_iaid(). */
+        bool test_mode;
+};
+
+static const uint8_t default_req_opts[] = {
+        SD_DHCP_OPTION_SUBNET_MASK,
+        SD_DHCP_OPTION_ROUTER,
+        SD_DHCP_OPTION_HOST_NAME,
+        SD_DHCP_OPTION_DOMAIN_NAME,
+        SD_DHCP_OPTION_DOMAIN_NAME_SERVER,
+};
+
+/* RFC7844 section 3:
+   MAY contain the Parameter Request List option.
+   RFC7844 section 3.6:
+   The client intending to protect its privacy SHOULD only request a
+   minimal number of options in the PRL and SHOULD also randomly shuffle
+   the ordering of option codes in the PRL.  If this random ordering
+   cannot be implemented, the client MAY order the option codes in the
+   PRL by option code number (lowest to highest).
+*/
+/* NOTE: using PRL options that Windows 10 RFC7844 implementation uses */
+static const uint8_t default_req_opts_anonymize[] = {
+        SD_DHCP_OPTION_SUBNET_MASK,                     /* 1 */
+        SD_DHCP_OPTION_ROUTER,                          /* 3 */
+        SD_DHCP_OPTION_DOMAIN_NAME_SERVER,              /* 6 */
+        SD_DHCP_OPTION_DOMAIN_NAME,                     /* 15 */
+        SD_DHCP_OPTION_ROUTER_DISCOVERY,                /* 31 */
+        SD_DHCP_OPTION_STATIC_ROUTE,                    /* 33 */
+        SD_DHCP_OPTION_VENDOR_SPECIFIC,                 /* 43 */
+        SD_DHCP_OPTION_NETBIOS_NAME_SERVER,             /* 44 */
+        SD_DHCP_OPTION_NETBIOS_NODE_TYPE,               /* 46 */
+        SD_DHCP_OPTION_NETBIOS_SCOPE,                   /* 47 */
+        SD_DHCP_OPTION_CLASSLESS_STATIC_ROUTE,          /* 121 */
+        SD_DHCP_OPTION_PRIVATE_CLASSLESS_STATIC_ROUTE,  /* 249 */
+        SD_DHCP_OPTION_PRIVATE_PROXY_AUTODISCOVERY,     /* 252 */
+};
+
+static int client_receive_message_raw(
+                sd_event_source *s,
+                int fd,
+                uint32_t revents,
+                void *userdata);
+static int client_receive_message_udp(
+                sd_event_source *s,
+                int fd,
+                uint32_t revents,
+                void *userdata);
+static void client_stop(sd_dhcp_client *client, int error);
+
+int sd_dhcp_client_id_to_string(const void *data, size_t len, char **ret) {
+        const sd_dhcp_client_id *client_id = data;
+        _cleanup_free_ char *t = NULL;
+        int r = 0;
+
+        assert_return(data, -EINVAL);
+        assert_return(len >= 1, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        len -= 1;
+        if (len > MAX_CLIENT_ID_LEN)
+                return -EINVAL;
+
+        switch (client_id->type) {
+        case 0:
+                if (utf8_is_printable((char *) client_id->gen.data, len))
+                        r = asprintf(&t, "%.*s", (int) len, client_id->gen.data);
+                else
+                        r = asprintf(&t, "DATA");
+                break;
+        case 1:
+                if (len == sizeof_field(sd_dhcp_client_id, eth))
+                        r = asprintf(&t, "%02x:%02x:%02x:%02x:%02x:%02x",
+                                     client_id->eth.haddr[0],
+                                     client_id->eth.haddr[1],
+                                     client_id->eth.haddr[2],
+                                     client_id->eth.haddr[3],
+                                     client_id->eth.haddr[4],
+                                     client_id->eth.haddr[5]);
+                else
+                        r = asprintf(&t, "ETHER");
+                break;
+        case 2 ... 254:
+                r = asprintf(&t, "ARP/LL");
+                break;
+        case 255:
+                if (len < sizeof(uint32_t))
+                        r = asprintf(&t, "IAID/DUID");
+                else {
+                        uint32_t iaid = be32toh(client_id->ns.iaid);
+                        /* TODO: check and stringify DUID */
+                        r = asprintf(&t, "IAID:0x%x/DUID", iaid);
+                }
+                break;
+        }
+        if (r < 0)
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(t);
+        return 0;
+}
+
+int sd_dhcp_client_set_callback(
+                sd_dhcp_client *client,
+                sd_dhcp_client_callback_t cb,
+                void *userdata) {
+
+        assert_return(client, -EINVAL);
+
+        client->callback = cb;
+        client->userdata = userdata;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_request_broadcast(sd_dhcp_client *client, int broadcast) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        client->request_broadcast = broadcast;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_request_option(sd_dhcp_client *client, uint8_t option) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        switch (option) {
+
+        case SD_DHCP_OPTION_PAD:
+        case SD_DHCP_OPTION_OVERLOAD:
+        case SD_DHCP_OPTION_MESSAGE_TYPE:
+        case SD_DHCP_OPTION_PARAMETER_REQUEST_LIST:
+        case SD_DHCP_OPTION_END:
+                return -EINVAL;
+
+        default:
+                break;
+        }
+
+        return set_ensure_put(&client->req_opts, NULL, UINT8_TO_PTR(option));
+}
+
+int sd_dhcp_client_set_request_address(
+                sd_dhcp_client *client,
+                const struct in_addr *last_addr) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        if (last_addr)
+                client->last_addr = last_addr->s_addr;
+        else
+                client->last_addr = INADDR_ANY;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_ifindex(sd_dhcp_client *client, int ifindex) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(ifindex > 0, -EINVAL);
+
+        client->ifindex = ifindex;
+        return 0;
+}
+
+int sd_dhcp_client_set_ifname(sd_dhcp_client *client, const char *ifname) {
+        assert_return(client, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&client->ifname, ifname);
+}
+
+int sd_dhcp_client_get_ifname(sd_dhcp_client *client, const char **ret) {
+        int r;
+
+        assert_return(client, -EINVAL);
+
+        r = get_ifname(client->ifindex, &client->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = client->ifname;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_mac(
+                sd_dhcp_client *client,
+                const uint8_t *hw_addr,
+                const uint8_t *bcast_addr,
+                size_t addr_len,
+                uint16_t arp_type) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(IN_SET(arp_type, ARPHRD_ETHER, ARPHRD_INFINIBAND), -EINVAL);
+        assert_return(hw_addr, -EINVAL);
+        assert_return(addr_len == (arp_type == ARPHRD_ETHER ? ETH_ALEN : INFINIBAND_ALEN), -EINVAL);
+
+        client->arp_type = arp_type;
+        hw_addr_set(&client->hw_addr, hw_addr, addr_len);
+        hw_addr_set(&client->bcast_addr, bcast_addr, bcast_addr ? addr_len : 0);
+
+        return 0;
+}
+
+int sd_dhcp_client_get_client_id(
+                sd_dhcp_client *client,
+                uint8_t *type,
+                const uint8_t **data,
+                size_t *data_len) {
+
+        assert_return(client, -EINVAL);
+        assert_return(type, -EINVAL);
+        assert_return(data, -EINVAL);
+        assert_return(data_len, -EINVAL);
+
+        if (client->client_id_len) {
+                *type = client->client_id.type;
+                *data = client->client_id.raw.data;
+                *data_len = client->client_id_len - sizeof(client->client_id.type);
+        } else {
+                *type = 0;
+                *data = NULL;
+                *data_len = 0;
+        }
+
+        return 0;
+}
+
+int sd_dhcp_client_set_client_id(
+                sd_dhcp_client *client,
+                uint8_t type,
+                const uint8_t *data,
+                size_t data_len) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(data, -EINVAL);
+        assert_return(data_len > 0 && data_len <= MAX_CLIENT_ID_LEN, -EINVAL);
+
+        /* For hardware types, log debug message about unexpected data length.
+         *
+         * Note that infiniband's INFINIBAND_ALEN is 20 bytes long, but only
+         * the last 8 bytes of the address are stable and suitable to put into
+         * the client-id. The caller is advised to account for that. */
+        if ((type == ARPHRD_ETHER && data_len != ETH_ALEN) ||
+            (type == ARPHRD_INFINIBAND && data_len != 8))
+                log_dhcp_client(client, "Changing client ID to hardware type %u with "
+                                "unexpected address length %zu",
+                                type, data_len);
+
+        client->client_id.type = type;
+        memcpy(&client->client_id.raw.data, data, data_len);
+        client->client_id_len = data_len + sizeof (client->client_id.type);
+
+        return 0;
+}
+
+/**
+ * Sets IAID and DUID. If duid is non-null, the DUID is set to duid_type + duid
+ * without further modification. Otherwise, if duid_type is supported, DUID
+ * is set based on that type. Otherwise, an error is returned.
+ */
+static int dhcp_client_set_iaid_duid_internal(
+                sd_dhcp_client *client,
+                bool iaid_append,
+                bool iaid_set,
+                uint32_t iaid,
+                DUIDType duid_type,
+                const void *duid,
+                size_t duid_len,
+                usec_t llt_time) {
+
+        size_t len;
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(duid_len == 0 || duid, -EINVAL);
+
+        if (duid) {
+                r = dhcp_validate_duid_len(duid_type, duid_len, true);
+                if (r < 0)
+                        return log_dhcp_client_errno(client, r, "Failed to validate length of DUID: %m");
+        }
+
+        zero(client->client_id);
+        client->client_id.type = 255;
+
+        if (iaid_append) {
+                if (iaid_set)
+                        client->client_id.ns.iaid = htobe32(iaid);
+                else {
+                        r = dhcp_identifier_set_iaid(client->ifindex, &client->hw_addr,
+                                                     /* legacy_unstable_byteorder = */ true,
+                                                     /* use_mac = */ client->test_mode,
+                                                     &client->client_id.ns.iaid);
+                        if (r < 0)
+                                return log_dhcp_client_errno(client, r, "Failed to set IAID: %m");
+                }
+        }
+
+        if (duid) {
+                client->client_id.ns.duid.type = htobe16(duid_type);
+                memcpy(&client->client_id.ns.duid.raw.data, duid, duid_len);
+                len = sizeof(client->client_id.ns.duid.type) + duid_len;
+
+        } else {
+                r = dhcp_identifier_set_duid(duid_type, &client->hw_addr,
+                                             client->arp_type, llt_time, client->test_mode,
+                                             &client->client_id.ns.duid, &len);
+                if (r == -EOPNOTSUPP)
+                        return log_dhcp_client_errno(client, r,
+                                                     "Failed to set %s. MAC address is not set or "
+                                                     "interface type is not supported.",
+                                                     duid_type_to_string(duid_type));
+                if (r < 0)
+                        return log_dhcp_client_errno(client, r, "Failed to set %s: %m",
+                                                     duid_type_to_string(duid_type));
+        }
+
+        client->client_id_len = sizeof(client->client_id.type) + len +
+                                (iaid_append ? sizeof(client->client_id.ns.iaid) : 0);
+
+        return 0;
+}
+
+int sd_dhcp_client_set_iaid_duid(
+                sd_dhcp_client *client,
+                bool iaid_set,
+                uint32_t iaid,
+                uint16_t duid_type,
+                const void *duid,
+                size_t duid_len) {
+        return dhcp_client_set_iaid_duid_internal(client, true, iaid_set, iaid, duid_type, duid, duid_len, 0);
+}
+
+int sd_dhcp_client_set_iaid_duid_llt(
+                sd_dhcp_client *client,
+                bool iaid_set,
+                uint32_t iaid,
+                usec_t llt_time) {
+        return dhcp_client_set_iaid_duid_internal(client, true, iaid_set, iaid, DUID_TYPE_LLT, NULL, 0, llt_time);
+}
+
+int sd_dhcp_client_set_duid(
+                sd_dhcp_client *client,
+                uint16_t duid_type,
+                const void *duid,
+                size_t duid_len) {
+        return dhcp_client_set_iaid_duid_internal(client, false, false, 0, duid_type, duid, duid_len, 0);
+}
+
+int sd_dhcp_client_set_duid_llt(
+                sd_dhcp_client *client,
+                usec_t llt_time) {
+        return dhcp_client_set_iaid_duid_internal(client, false, false, 0, DUID_TYPE_LLT, NULL, 0, llt_time);
+}
+
+void dhcp_client_set_test_mode(sd_dhcp_client *client, bool test_mode) {
+        assert(client);
+
+        client->test_mode = test_mode;
+}
+
+int sd_dhcp_client_set_hostname(
+                sd_dhcp_client *client,
+                const char *hostname) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        /* Make sure hostnames qualify as DNS and as Linux hostnames */
+        if (hostname &&
+            !(hostname_is_valid(hostname, 0) && dns_name_is_valid(hostname) > 0))
+                return -EINVAL;
+
+        return free_and_strdup(&client->hostname, hostname);
+}
+
+int sd_dhcp_client_set_vendor_class_identifier(
+                sd_dhcp_client *client,
+                const char *vci) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        return free_and_strdup(&client->vendor_class_identifier, vci);
+}
+
+int sd_dhcp_client_set_mud_url(
+                sd_dhcp_client *client,
+                const char *mudurl) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(mudurl, -EINVAL);
+        assert_return(strlen(mudurl) <= 255, -EINVAL);
+        assert_return(http_url_is_valid(mudurl), -EINVAL);
+
+        return free_and_strdup(&client->mudurl, mudurl);
+}
+
+int sd_dhcp_client_set_user_class(
+                sd_dhcp_client *client,
+                char * const *user_class) {
+
+        char **s = NULL;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(!strv_isempty(user_class), -EINVAL);
+
+        STRV_FOREACH(p, user_class) {
+                size_t n = strlen(*p);
+
+                if (n > 255 || n == 0)
+                        return -EINVAL;
+        }
+
+        s = strv_copy(user_class);
+        if (!s)
+                return -ENOMEM;
+
+        return strv_free_and_replace(client->user_class, s);
+}
+
+int sd_dhcp_client_set_client_port(
+                sd_dhcp_client *client,
+                uint16_t port) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        client->port = port;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_mtu(sd_dhcp_client *client, uint32_t mtu) {
+        assert_return(client, -EINVAL);
+        assert_return(mtu >= DHCP_MIN_PACKET_SIZE, -ERANGE);
+
+        /* MTU may be changed by the acquired lease. Hence, we cannot require that the client is stopped here.
+         * Please do not add assertion for !sd_dhcp_client_is_running(client) here. */
+
+        client->mtu = mtu;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_max_attempts(sd_dhcp_client *client, uint64_t max_attempts) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        client->max_attempts = max_attempts;
+
+        return 0;
+}
+
+int sd_dhcp_client_add_option(sd_dhcp_client *client, sd_dhcp_option *v) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(v, -EINVAL);
+
+        r = ordered_hashmap_ensure_put(&client->extra_options, &dhcp_option_hash_ops, UINT_TO_PTR(v->option), v);
+        if (r < 0)
+                return r;
+
+        sd_dhcp_option_ref(v);
+        return 0;
+}
+
+int sd_dhcp_client_add_vendor_option(sd_dhcp_client *client, sd_dhcp_option *v) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(v, -EINVAL);
+
+        r = ordered_hashmap_ensure_allocated(&client->vendor_options, &dhcp_option_hash_ops);
+        if (r < 0)
+                return -ENOMEM;
+
+        r = ordered_hashmap_put(client->vendor_options, v, v);
+        if (r < 0)
+                return r;
+
+        sd_dhcp_option_ref(v);
+
+        return 1;
+}
+
+int sd_dhcp_client_get_lease(sd_dhcp_client *client, sd_dhcp_lease **ret) {
+        assert_return(client, -EINVAL);
+
+        if (!IN_SET(client->state, DHCP_STATE_SELECTING, DHCP_STATE_BOUND, DHCP_STATE_RENEWING, DHCP_STATE_REBINDING))
+                return -EADDRNOTAVAIL;
+
+        if (ret)
+                *ret = client->lease;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_service_type(sd_dhcp_client *client, int type) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        client->ip_service_type = type;
+
+        return 0;
+}
+
+int sd_dhcp_client_set_fallback_lease_lifetime(sd_dhcp_client *client, uint32_t fallback_lease_lifetime) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+        assert_return(fallback_lease_lifetime > 0, -EINVAL);
+
+        client->fallback_lease_lifetime = fallback_lease_lifetime;
+
+        return 0;
+}
+
+static int client_notify(sd_dhcp_client *client, int event) {
+        assert(client);
+
+        if (client->callback)
+                return client->callback(client, event, client->userdata);
+
+        return 0;
+}
+
+static int client_initialize(sd_dhcp_client *client) {
+        assert_return(client, -EINVAL);
+
+        client->receive_message = sd_event_source_disable_unref(client->receive_message);
+
+        client->fd = safe_close(client->fd);
+
+        (void) event_source_disable(client->timeout_resend);
+        (void) event_source_disable(client->timeout_t1);
+        (void) event_source_disable(client->timeout_t2);
+        (void) event_source_disable(client->timeout_expire);
+
+        client->attempt = 0;
+
+        client->state = DHCP_STATE_INIT;
+        client->xid = 0;
+
+        client->lease = sd_dhcp_lease_unref(client->lease);
+
+        return 0;
+}
+
+static void client_stop(sd_dhcp_client *client, int error) {
+        assert(client);
+
+        if (error < 0)
+                log_dhcp_client_errno(client, error, "STOPPED: %m");
+        else if (error == SD_DHCP_CLIENT_EVENT_STOP)
+                log_dhcp_client(client, "STOPPED");
+        else
+                log_dhcp_client(client, "STOPPED: Unknown event");
+
+        client_notify(client, error);
+
+        client_initialize(client);
+}
+
+/* RFC2131 section 4.1:
+ * retransmission delays should include -1 to +1 sec of random 'fuzz'. */
+#define RFC2131_RANDOM_FUZZ \
+        ((int64_t)(random_u64() % (2 * USEC_PER_SEC)) - (int64_t)USEC_PER_SEC)
+
+/* RFC2131 section 4.1:
+ * for retransmission delays, timeout should start at 4s then double
+ * each attempt with max of 64s, with -1 to +1 sec of random 'fuzz' added.
+ * This assumes the first call will be using attempt 1. */
+static usec_t client_compute_request_timeout(usec_t now, uint64_t attempt) {
+        usec_t timeout = (UINT64_C(1) << MIN(attempt + 1, UINT64_C(6))) * USEC_PER_SEC;
+
+        return usec_sub_signed(usec_add(now, timeout), RFC2131_RANDOM_FUZZ);
+}
+
+/* RFC2131 section 4.4.5:
+ * T1 defaults to (0.5 * duration_of_lease).
+ * T2 defaults to (0.875 * duration_of_lease). */
+#define T1_DEFAULT(lifetime) ((lifetime) / 2)
+#define T2_DEFAULT(lifetime) (((lifetime) * 7) / 8)
+
+/* RFC2131 section 4.4.5:
+ * the client SHOULD wait one-half of the remaining time until T2 (in RENEWING state)
+ * and one-half of the remaining lease time (in REBINDING state), down to a minimum
+ * of 60 seconds.
+ * Note that while the default T1/T2 initial times do have random 'fuzz' applied,
+ * the RFC sec 4.4.5 does not mention adding any fuzz to retries. */
+static usec_t client_compute_reacquisition_timeout(usec_t now, usec_t expire) {
+        return now + MAX(usec_sub_unsigned(expire, now) / 2, 60 * USEC_PER_SEC);
+}
+
+static int cmp_uint8(const uint8_t *a, const uint8_t *b) {
+        return CMP(*a, *b);
+}
+
+static int client_message_init(
+                sd_dhcp_client *client,
+                DHCPPacket **ret,
+                uint8_t type,
+                size_t *_optlen,
+                size_t *_optoffset) {
+
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        size_t optlen, optoffset, size;
+        usec_t time_now;
+        uint16_t secs;
+        int r;
+
+        assert(client);
+        assert(client->start_time);
+        assert(ret);
+        assert(_optlen);
+        assert(_optoffset);
+        assert(IN_SET(type, DHCP_DISCOVER, DHCP_REQUEST, DHCP_RELEASE, DHCP_DECLINE));
+
+        optlen = DHCP_MIN_OPTIONS_SIZE;
+        size = sizeof(DHCPPacket) + optlen;
+
+        packet = malloc0(size);
+        if (!packet)
+                return -ENOMEM;
+
+        r = dhcp_message_init(&packet->dhcp, BOOTREQUEST, client->xid, type,
+                              client->arp_type, client->hw_addr.length, client->hw_addr.bytes,
+                              optlen, &optoffset);
+        if (r < 0)
+                return r;
+
+        /* Although 'secs' field is a SHOULD in RFC 2131, certain DHCP servers
+           refuse to issue an DHCP lease if 'secs' is set to zero */
+        r = sd_event_now(client->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                return r;
+        assert(time_now >= client->start_time);
+
+        /* seconds between sending first and last DISCOVER
+         * must always be strictly positive to deal with broken servers */
+        secs = ((time_now - client->start_time) / USEC_PER_SEC) ? : 1;
+        packet->dhcp.secs = htobe16(secs);
+
+        /* RFC2131 section 4.1
+           A client that cannot receive unicast IP datagrams until its protocol
+           software has been configured with an IP address SHOULD set the
+           BROADCAST bit in the 'flags' field to 1 in any DHCPDISCOVER or
+           DHCPREQUEST messages that client sends.  The BROADCAST bit will
+           provide a hint to the DHCP server and BOOTP relay agent to broadcast
+           any messages to the client on the client's subnet.
+
+           Note: some interfaces needs this to be enabled, but some networks
+           needs this to be disabled as broadcasts are filteretd, so this
+           needs to be configurable */
+        if (client->request_broadcast || client->arp_type != ARPHRD_ETHER)
+                packet->dhcp.flags = htobe16(0x8000);
+
+        /* If no client identifier exists, construct an RFC 4361-compliant one */
+        if (client->client_id_len == 0) {
+                size_t duid_len;
+
+                client->client_id.type = 255;
+
+                r = dhcp_identifier_set_iaid(client->ifindex, &client->hw_addr,
+                                             /* legacy_unstable_byteorder = */ true,
+                                             /* use_mac = */ client->test_mode,
+                                             &client->client_id.ns.iaid);
+                if (r < 0)
+                        return r;
+
+                r = dhcp_identifier_set_duid_en(client->test_mode, &client->client_id.ns.duid, &duid_len);
+                if (r < 0)
+                        return r;
+
+                client->client_id_len = sizeof(client->client_id.type) + sizeof(client->client_id.ns.iaid) + duid_len;
+        }
+
+        /* Some DHCP servers will refuse to issue an DHCP lease if the Client
+           Identifier option is not set */
+        if (client->client_id_len) {
+                r = dhcp_option_append(&packet->dhcp, optlen, &optoffset, 0,
+                                       SD_DHCP_OPTION_CLIENT_IDENTIFIER,
+                                       client->client_id_len,
+                                       &client->client_id);
+                if (r < 0)
+                        return r;
+        }
+
+        /* RFC2131 section 3.5:
+           in its initial DHCPDISCOVER or DHCPREQUEST message, a
+           client may provide the server with a list of specific
+           parameters the client is interested in. If the client
+           includes a list of parameters in a DHCPDISCOVER message,
+           it MUST include that list in any subsequent DHCPREQUEST
+           messages.
+         */
+
+        /* RFC7844 section 3:
+           MAY contain the Parameter Request List option. */
+        /* NOTE: in case that there would be an option to do not send
+         * any PRL at all, the size should be checked before sending */
+        if (!set_isempty(client->req_opts) && type != DHCP_RELEASE) {
+                _cleanup_free_ uint8_t *opts = NULL;
+                size_t n_opts, i = 0;
+                void *val;
+
+                n_opts = set_size(client->req_opts);
+                opts = new(uint8_t, n_opts);
+                if (!opts)
+                        return -ENOMEM;
+
+                SET_FOREACH(val, client->req_opts)
+                        opts[i++] = PTR_TO_UINT8(val);
+                assert(i == n_opts);
+
+                /* For anonymizing the request, let's sort the options. */
+                typesafe_qsort(opts, n_opts, cmp_uint8);
+
+                r = dhcp_option_append(&packet->dhcp, optlen, &optoffset, 0,
+                                       SD_DHCP_OPTION_PARAMETER_REQUEST_LIST,
+                                       n_opts, opts);
+                if (r < 0)
+                        return r;
+        }
+
+        /* RFC2131 section 3.5:
+           The client SHOULD include the ’maximum DHCP message size’ option to
+           let the server know how large the server may make its DHCP messages.
+
+           Note (from ConnMan): Some DHCP servers will send bigger DHCP packets
+           than the defined default size unless the Maximum Message Size option
+           is explicitly set
+
+           RFC3442 "Requirements to Avoid Sizing Constraints":
+           Because a full routing table can be quite large, the standard 576
+           octet maximum size for a DHCP message may be too short to contain
+           some legitimate Classless Static Route options.  Because of this,
+           clients implementing the Classless Static Route option SHOULD send a
+           Maximum DHCP Message Size [4] option if the DHCP client's TCP/IP
+           stack is capable of receiving larger IP datagrams.  In this case, the
+           client SHOULD set the value of this option to at least the MTU of the
+           interface that the client is configuring.  The client MAY set the
+           value of this option higher, up to the size of the largest UDP packet
+           it is prepared to accept.  (Note that the value specified in the
+           Maximum DHCP Message Size option is the total maximum packet size,
+           including IP and UDP headers.)
+         */
+        /* RFC7844 section 3:
+           SHOULD NOT contain any other option. */
+        if (!client->anonymize && IN_SET(type, DHCP_DISCOVER, DHCP_REQUEST)) {
+                be16_t max_size = htobe16(MIN(client->mtu - DHCP_IP_UDP_SIZE, (uint32_t) UINT16_MAX));
+                r = dhcp_option_append(&packet->dhcp, optlen, &optoffset, 0,
+                                       SD_DHCP_OPTION_MAXIMUM_MESSAGE_SIZE,
+                                       2, &max_size);
+                if (r < 0)
+                        return r;
+        }
+
+        *_optlen = optlen;
+        *_optoffset = optoffset;
+        *ret = TAKE_PTR(packet);
+
+        return 0;
+}
+
+static int client_append_fqdn_option(
+                DHCPMessage *message,
+                size_t optlen,
+                size_t *optoffset,
+                const char *fqdn) {
+
+        uint8_t buffer[3 + DHCP_MAX_FQDN_LENGTH];
+        int r;
+
+        buffer[0] = DHCP_FQDN_FLAG_S | /* Request server to perform A RR DNS updates */
+                    DHCP_FQDN_FLAG_E;  /* Canonical wire format */
+        buffer[1] = 0;                 /* RCODE1 (deprecated) */
+        buffer[2] = 0;                 /* RCODE2 (deprecated) */
+
+        r = dns_name_to_wire_format(fqdn, buffer + 3, sizeof(buffer) - 3, false);
+        if (r > 0)
+                r = dhcp_option_append(message, optlen, optoffset, 0,
+                                       SD_DHCP_OPTION_FQDN, 3 + r, buffer);
+
+        return r;
+}
+
+static int dhcp_client_send_raw(
+                sd_dhcp_client *client,
+                DHCPPacket *packet,
+                size_t len) {
+
+        dhcp_packet_append_ip_headers(packet, INADDR_ANY, client->port,
+                                      INADDR_BROADCAST, DHCP_PORT_SERVER, len, client->ip_service_type);
+
+        return dhcp_network_send_raw_socket(client->fd, &client->link,
+                                            packet, len);
+}
+
+static int client_append_common_discover_request_options(sd_dhcp_client *client, DHCPPacket *packet, size_t *optoffset, size_t optlen) {
+        sd_dhcp_option *j;
+        int r;
+
+        assert(client);
+
+        if (client->hostname) {
+                /* According to RFC 4702 "clients that send the Client FQDN option in
+                   their messages MUST NOT also send the Host Name option". Just send
+                   one of the two depending on the hostname type.
+                */
+                if (dns_name_is_single_label(client->hostname)) {
+                        /* it is unclear from RFC 2131 if client should send hostname in
+                           DHCPDISCOVER but dhclient does and so we do as well
+                        */
+                        r = dhcp_option_append(&packet->dhcp, optlen, optoffset, 0,
+                                               SD_DHCP_OPTION_HOST_NAME,
+                                               strlen(client->hostname), client->hostname);
+                } else
+                        r = client_append_fqdn_option(&packet->dhcp, optlen, optoffset,
+                                                      client->hostname);
+                if (r < 0)
+                        return r;
+        }
+
+        if (client->vendor_class_identifier) {
+                r = dhcp_option_append(&packet->dhcp, optlen, optoffset, 0,
+                                       SD_DHCP_OPTION_VENDOR_CLASS_IDENTIFIER,
+                                       strlen(client->vendor_class_identifier),
+                                       client->vendor_class_identifier);
+                if (r < 0)
+                        return r;
+        }
+
+        if (client->mudurl) {
+                r = dhcp_option_append(&packet->dhcp, optlen, optoffset, 0,
+                                       SD_DHCP_OPTION_MUD_URL,
+                                       strlen(client->mudurl),
+                                       client->mudurl);
+                if (r < 0)
+                        return r;
+        }
+
+        if (client->user_class) {
+                r = dhcp_option_append(&packet->dhcp, optlen, optoffset, 0,
+                                       SD_DHCP_OPTION_USER_CLASS,
+                                       strv_length(client->user_class),
+                                       client->user_class);
+                if (r < 0)
+                        return r;
+        }
+
+        ORDERED_HASHMAP_FOREACH(j, client->extra_options) {
+                r = dhcp_option_append(&packet->dhcp, optlen, optoffset, 0,
+                                       j->option, j->length, j->data);
+                if (r < 0)
+                        return r;
+        }
+
+        if (!ordered_hashmap_isempty(client->vendor_options)) {
+                r = dhcp_option_append(
+                                &packet->dhcp, optlen, optoffset, 0,
+                                SD_DHCP_OPTION_VENDOR_SPECIFIC,
+                                ordered_hashmap_size(client->vendor_options), client->vendor_options);
+                if (r < 0)
+                        return r;
+        }
+
+
+        return 0;
+}
+
+static int client_send_discover(sd_dhcp_client *client) {
+        _cleanup_free_ DHCPPacket *discover = NULL;
+        size_t optoffset, optlen;
+        int r;
+
+        assert(client);
+        assert(IN_SET(client->state, DHCP_STATE_INIT, DHCP_STATE_SELECTING));
+
+        r = client_message_init(client, &discover, DHCP_DISCOVER,
+                                &optlen, &optoffset);
+        if (r < 0)
+                return r;
+
+        /* the client may suggest values for the network address
+           and lease time in the DHCPDISCOVER message. The client may include
+           the ’requested IP address’ option to suggest that a particular IP
+           address be assigned, and may include the ’IP address lease time’
+           option to suggest the lease time it would like.
+         */
+        /* RFC7844 section 3:
+           SHOULD NOT contain any other option. */
+        if (!client->anonymize && client->last_addr != INADDR_ANY) {
+                r = dhcp_option_append(&discover->dhcp, optlen, &optoffset, 0,
+                                       SD_DHCP_OPTION_REQUESTED_IP_ADDRESS,
+                                       4, &client->last_addr);
+                if (r < 0)
+                        return r;
+        }
+
+        r = client_append_common_discover_request_options(client, discover, &optoffset, optlen);
+        if (r < 0)
+                return r;
+
+        r = dhcp_option_append(&discover->dhcp, optlen, &optoffset, 0,
+                               SD_DHCP_OPTION_END, 0, NULL);
+        if (r < 0)
+                return r;
+
+        /* We currently ignore:
+           The client SHOULD wait a random time between one and ten seconds to
+           desynchronize the use of DHCP at startup.
+         */
+        r = dhcp_client_send_raw(client, discover, sizeof(DHCPPacket) + optoffset);
+        if (r < 0)
+                return r;
+
+        log_dhcp_client(client, "DISCOVER");
+
+        return 0;
+}
+
+static int client_send_request(sd_dhcp_client *client) {
+        _cleanup_free_ DHCPPacket *request = NULL;
+        size_t optoffset, optlen;
+        int r;
+
+        assert(client);
+
+        r = client_message_init(client, &request, DHCP_REQUEST, &optlen, &optoffset);
+        if (r < 0)
+                return r;
+
+        switch (client->state) {
+        /* See RFC2131 section 4.3.2 (note that there is a typo in the RFC,
+           SELECTING should be REQUESTING)
+         */
+
+        case DHCP_STATE_REQUESTING:
+                /* Client inserts the address of the selected server in ’server
+                   identifier’, ’ciaddr’ MUST be zero, ’requested IP address’ MUST be
+                   filled in with the yiaddr value from the chosen DHCPOFFER.
+                 */
+
+                r = dhcp_option_append(&request->dhcp, optlen, &optoffset, 0,
+                                       SD_DHCP_OPTION_SERVER_IDENTIFIER,
+                                       4, &client->lease->server_address);
+                if (r < 0)
+                        return r;
+
+                r = dhcp_option_append(&request->dhcp, optlen, &optoffset, 0,
+                                       SD_DHCP_OPTION_REQUESTED_IP_ADDRESS,
+                                       4, &client->lease->address);
+                if (r < 0)
+                        return r;
+
+                break;
+
+        case DHCP_STATE_INIT_REBOOT:
+                /* ’server identifier’ MUST NOT be filled in, ’requested IP address’
+                   option MUST be filled in with client’s notion of its previously
+                   assigned address. ’ciaddr’ MUST be zero.
+                 */
+                r = dhcp_option_append(&request->dhcp, optlen, &optoffset, 0,
+                                       SD_DHCP_OPTION_REQUESTED_IP_ADDRESS,
+                                       4, &client->last_addr);
+                if (r < 0)
+                        return r;
+                break;
+
+        case DHCP_STATE_RENEWING:
+                /* ’server identifier’ MUST NOT be filled in, ’requested IP address’
+                   option MUST NOT be filled in, ’ciaddr’ MUST be filled in with
+                   client’s IP address.
+                */
+
+        case DHCP_STATE_REBINDING:
+                /* ’server identifier’ MUST NOT be filled in, ’requested IP address’
+                   option MUST NOT be filled in, ’ciaddr’ MUST be filled in with
+                   client’s IP address.
+
+                   This message MUST be broadcast to the 0xffffffff IP broadcast address.
+                 */
+                request->dhcp.ciaddr = client->lease->address;
+
+                break;
+
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_SELECTING:
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_BOUND:
+        case DHCP_STATE_STOPPED:
+                return -EINVAL;
+        }
+
+        r = client_append_common_discover_request_options(client, request, &optoffset, optlen);
+        if (r < 0)
+                return r;
+
+        r = dhcp_option_append(&request->dhcp, optlen, &optoffset, 0,
+                               SD_DHCP_OPTION_END, 0, NULL);
+        if (r < 0)
+                return r;
+
+        if (client->state == DHCP_STATE_RENEWING)
+                r = dhcp_network_send_udp_socket(client->fd,
+                                                 client->lease->server_address,
+                                                 DHCP_PORT_SERVER,
+                                                 &request->dhcp,
+                                                 sizeof(DHCPMessage) + optoffset);
+        else
+                r = dhcp_client_send_raw(client, request, sizeof(DHCPPacket) + optoffset);
+        if (r < 0)
+                return r;
+
+        switch (client->state) {
+
+        case DHCP_STATE_REQUESTING:
+                log_dhcp_client(client, "REQUEST (requesting)");
+                break;
+
+        case DHCP_STATE_INIT_REBOOT:
+                log_dhcp_client(client, "REQUEST (init-reboot)");
+                break;
+
+        case DHCP_STATE_RENEWING:
+                log_dhcp_client(client, "REQUEST (renewing)");
+                break;
+
+        case DHCP_STATE_REBINDING:
+                log_dhcp_client(client, "REQUEST (rebinding)");
+                break;
+
+        default:
+                log_dhcp_client(client, "REQUEST (invalid)");
+                break;
+        }
+
+        return 0;
+}
+
+static int client_start(sd_dhcp_client *client);
+
+static int client_timeout_resend(
+                sd_event_source *s,
+                uint64_t usec,
+                void *userdata) {
+
+        sd_dhcp_client *client = ASSERT_PTR(userdata);
+        DHCP_CLIENT_DONT_DESTROY(client);
+        usec_t next_timeout;
+        uint64_t time_now;
+        int r;
+
+        assert(s);
+        assert(client->event);
+
+        r = sd_event_now(client->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                goto error;
+
+        switch (client->state) {
+
+        case DHCP_STATE_RENEWING:
+                next_timeout = client_compute_reacquisition_timeout(time_now, client->t2_time);
+                break;
+
+        case DHCP_STATE_REBINDING:
+                next_timeout = client_compute_reacquisition_timeout(time_now, client->expire_time);
+                break;
+
+        case DHCP_STATE_REBOOTING:
+                /* start over as we did not receive a timely ack or nak */
+                r = client_initialize(client);
+                if (r < 0)
+                        goto error;
+
+                r = client_start(client);
+                if (r < 0)
+                        goto error;
+
+                log_dhcp_client(client, "REBOOTED");
+                return 0;
+
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_SELECTING:
+        case DHCP_STATE_REQUESTING:
+        case DHCP_STATE_BOUND:
+                if (client->attempt >= client->max_attempts)
+                        goto error;
+
+                client->attempt++;
+                next_timeout = client_compute_request_timeout(time_now, client->attempt);
+                break;
+
+        case DHCP_STATE_STOPPED:
+                r = -EINVAL;
+                goto error;
+
+        default:
+                assert_not_reached();
+        }
+
+        r = event_reset_time(client->event, &client->timeout_resend,
+                             CLOCK_BOOTTIME,
+                             next_timeout, 10 * USEC_PER_MSEC,
+                             client_timeout_resend, client,
+                             client->event_priority, "dhcp4-resend-timer", true);
+        if (r < 0)
+                goto error;
+
+        switch (client->state) {
+        case DHCP_STATE_INIT:
+                r = client_send_discover(client);
+                if (r >= 0) {
+                        client->state = DHCP_STATE_SELECTING;
+                        client->attempt = 0;
+                } else if (client->attempt >= client->max_attempts)
+                        goto error;
+
+                break;
+
+        case DHCP_STATE_SELECTING:
+                r = client_send_discover(client);
+                if (r < 0 && client->attempt >= client->max_attempts)
+                        goto error;
+
+                break;
+
+        case DHCP_STATE_INIT_REBOOT:
+        case DHCP_STATE_REQUESTING:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+                r = client_send_request(client);
+                if (r < 0 && client->attempt >= client->max_attempts)
+                         goto error;
+
+                if (client->state == DHCP_STATE_INIT_REBOOT)
+                        client->state = DHCP_STATE_REBOOTING;
+
+                client->request_sent = time_now;
+                break;
+
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_BOUND:
+                break;
+
+        case DHCP_STATE_STOPPED:
+                r = -EINVAL;
+                goto error;
+        }
+
+        if (client->attempt >= TRANSIENT_FAILURE_ATTEMPTS)
+                client_notify(client, SD_DHCP_CLIENT_EVENT_TRANSIENT_FAILURE);
+
+        return 0;
+
+error:
+        client_stop(client, r);
+
+        /* Errors were dealt with when stopping the client, don't spill
+           errors into the event loop handler */
+        return 0;
+}
+
+static int client_initialize_io_events(
+                sd_dhcp_client *client,
+                sd_event_io_handler_t io_callback) {
+
+        int r;
+
+        assert(client);
+        assert(client->event);
+
+        r = sd_event_add_io(client->event, &client->receive_message,
+                            client->fd, EPOLLIN, io_callback,
+                            client);
+        if (r < 0)
+                goto error;
+
+        r = sd_event_source_set_priority(client->receive_message,
+                                         client->event_priority);
+        if (r < 0)
+                goto error;
+
+        r = sd_event_source_set_description(client->receive_message, "dhcp4-receive-message");
+        if (r < 0)
+                goto error;
+
+error:
+        if (r < 0)
+                client_stop(client, r);
+
+        return 0;
+}
+
+static int client_initialize_time_events(sd_dhcp_client *client) {
+        uint64_t usec = 0;
+        int r;
+
+        assert(client);
+        assert(client->event);
+
+        if (client->start_delay > 0) {
+                assert_se(sd_event_now(client->event, CLOCK_BOOTTIME, &usec) >= 0);
+                usec += client->start_delay;
+        }
+
+        r = event_reset_time(client->event, &client->timeout_resend,
+                             CLOCK_BOOTTIME,
+                             usec, 0,
+                             client_timeout_resend, client,
+                             client->event_priority, "dhcp4-resend-timer", true);
+        if (r < 0)
+                client_stop(client, r);
+
+        return 0;
+
+}
+
+static int client_initialize_events(sd_dhcp_client *client, sd_event_io_handler_t io_callback) {
+        client_initialize_io_events(client, io_callback);
+        client_initialize_time_events(client);
+
+        return 0;
+}
+
+static int client_start_delayed(sd_dhcp_client *client) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(client->event, -EINVAL);
+        assert_return(client->ifindex > 0, -EINVAL);
+        assert_return(client->fd < 0, -EBUSY);
+        assert_return(client->xid == 0, -EINVAL);
+        assert_return(IN_SET(client->state, DHCP_STATE_INIT, DHCP_STATE_INIT_REBOOT), -EBUSY);
+
+        client->xid = random_u32();
+
+        r = dhcp_network_bind_raw_socket(client->ifindex, &client->link, client->xid,
+                                         &client->hw_addr, &client->bcast_addr,
+                                         client->arp_type, client->port);
+        if (r < 0) {
+                client_stop(client, r);
+                return r;
+        }
+        client->fd = r;
+
+        if (IN_SET(client->state, DHCP_STATE_INIT, DHCP_STATE_INIT_REBOOT))
+                client->start_time = now(CLOCK_BOOTTIME);
+
+        return client_initialize_events(client, client_receive_message_raw);
+}
+
+static int client_start(sd_dhcp_client *client) {
+        client->start_delay = 0;
+        return client_start_delayed(client);
+}
+
+static int client_timeout_expire(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp_client *client = userdata;
+        DHCP_CLIENT_DONT_DESTROY(client);
+
+        log_dhcp_client(client, "EXPIRED");
+
+        client_notify(client, SD_DHCP_CLIENT_EVENT_EXPIRED);
+
+        /* lease was lost, start over if not freed or stopped in callback */
+        if (client->state != DHCP_STATE_STOPPED) {
+                client_initialize(client);
+                client_start(client);
+        }
+
+        return 0;
+}
+
+static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp_client *client = ASSERT_PTR(userdata);
+        DHCP_CLIENT_DONT_DESTROY(client);
+        int r;
+
+        client->receive_message = sd_event_source_disable_unref(client->receive_message);
+        client->fd = safe_close(client->fd);
+
+        client->state = DHCP_STATE_REBINDING;
+        client->attempt = 0;
+
+        r = dhcp_network_bind_raw_socket(client->ifindex, &client->link, client->xid,
+                                         &client->hw_addr, &client->bcast_addr,
+                                         client->arp_type, client->port);
+        if (r < 0) {
+                client_stop(client, r);
+                return 0;
+        }
+        client->fd = r;
+
+        return client_initialize_events(client, client_receive_message_raw);
+}
+
+static int client_timeout_t1(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp_client *client = userdata;
+        DHCP_CLIENT_DONT_DESTROY(client);
+
+        if (client->lease)
+                client->state = DHCP_STATE_RENEWING;
+        else if (client->state != DHCP_STATE_INIT)
+                client->state = DHCP_STATE_INIT_REBOOT;
+        client->attempt = 0;
+
+        return client_initialize_time_events(client);
+}
+
+static int client_handle_offer(sd_dhcp_client *client, DHCPMessage *offer, size_t len) {
+        _cleanup_(sd_dhcp_lease_unrefp) sd_dhcp_lease *lease = NULL;
+        int r;
+
+        r = dhcp_lease_new(&lease);
+        if (r < 0)
+                return r;
+
+        if (client->client_id_len) {
+                r = dhcp_lease_set_client_id(lease,
+                                             (uint8_t *) &client->client_id,
+                                             client->client_id_len);
+                if (r < 0)
+                        return r;
+        }
+
+        r = dhcp_option_parse(offer, len, dhcp_lease_parse_options, lease, NULL);
+        if (r != DHCP_OFFER) {
+                log_dhcp_client(client, "received message was not an OFFER, ignoring");
+                return -ENOMSG;
+        }
+
+        lease->next_server = offer->siaddr;
+        lease->address = offer->yiaddr;
+
+        if (lease->lifetime == 0 && client->fallback_lease_lifetime > 0)
+                lease->lifetime = client->fallback_lease_lifetime;
+
+        if (lease->address == 0 ||
+            lease->server_address == 0 ||
+            lease->lifetime == 0) {
+                log_dhcp_client(client, "received lease lacks address, server address or lease lifetime, ignoring");
+                return -ENOMSG;
+        }
+
+        if (!lease->have_subnet_mask) {
+                r = dhcp_lease_set_default_subnet_mask(lease);
+                if (r < 0) {
+                        log_dhcp_client(client,
+                                        "received lease lacks subnet mask, "
+                                        "and a fallback one cannot be generated, ignoring");
+                        return -ENOMSG;
+                }
+        }
+
+        sd_dhcp_lease_unref(client->lease);
+        client->lease = TAKE_PTR(lease);
+
+        if (client_notify(client, SD_DHCP_CLIENT_EVENT_SELECTING) < 0)
+                return -ENOMSG;
+
+        log_dhcp_client(client, "OFFER");
+
+        return 0;
+}
+
+static int client_handle_forcerenew(sd_dhcp_client *client, DHCPMessage *force, size_t len) {
+        int r;
+
+        r = dhcp_option_parse(force, len, NULL, NULL, NULL);
+        if (r != DHCP_FORCERENEW)
+                return -ENOMSG;
+
+#if 0
+        log_dhcp_client(client, "FORCERENEW");
+
+        return 0;
+#else
+        /* FIXME: Ignore FORCERENEW requests until we implement RFC3118 (Authentication for DHCP
+         * Messages) and/or RFC6704 (Forcerenew Nonce Authentication), as unauthenticated FORCERENEW
+         * requests causes a security issue (TALOS-2020-1142, CVE-2020-13529). */
+        log_dhcp_client(client, "Received FORCERENEW, ignoring.");
+        return -ENOMSG;
+#endif
+}
+
+static bool lease_equal(const sd_dhcp_lease *a, const sd_dhcp_lease *b) {
+        if (a->address != b->address)
+                return false;
+
+        if (a->subnet_mask != b->subnet_mask)
+                return false;
+
+        if (a->router_size != b->router_size)
+                return false;
+
+        for (size_t i = 0; i < a->router_size; i++)
+                if (a->router[i].s_addr != b->router[i].s_addr)
+                        return false;
+
+        return true;
+}
+
+static int client_handle_ack(sd_dhcp_client *client, DHCPMessage *ack, size_t len) {
+        _cleanup_(sd_dhcp_lease_unrefp) sd_dhcp_lease *lease = NULL;
+        _cleanup_free_ char *error_message = NULL;
+        int r;
+
+        r = dhcp_lease_new(&lease);
+        if (r < 0)
+                return r;
+
+        if (client->client_id_len) {
+                r = dhcp_lease_set_client_id(lease,
+                                             (uint8_t *) &client->client_id,
+                                             client->client_id_len);
+                if (r < 0)
+                        return r;
+        }
+
+        r = dhcp_option_parse(ack, len, dhcp_lease_parse_options, lease, &error_message);
+        if (r == DHCP_NAK) {
+                log_dhcp_client(client, "NAK: %s", strna(error_message));
+                return -EADDRNOTAVAIL;
+        }
+
+        if (r != DHCP_ACK) {
+                log_dhcp_client(client, "received message was not an ACK, ignoring");
+                return -ENOMSG;
+        }
+
+        lease->next_server = ack->siaddr;
+
+        lease->address = ack->yiaddr;
+
+        if (lease->address == INADDR_ANY ||
+            lease->server_address == INADDR_ANY ||
+            lease->lifetime == 0) {
+                log_dhcp_client(client, "received lease lacks address, server "
+                                "address or lease lifetime, ignoring");
+                return -ENOMSG;
+        }
+
+        if (lease->subnet_mask == INADDR_ANY) {
+                r = dhcp_lease_set_default_subnet_mask(lease);
+                if (r < 0) {
+                        log_dhcp_client(client,
+                                        "received lease lacks subnet mask, "
+                                        "and a fallback one cannot be generated, ignoring");
+                        return -ENOMSG;
+                }
+        }
+
+        r = SD_DHCP_CLIENT_EVENT_IP_ACQUIRE;
+        if (client->lease) {
+                if (lease_equal(client->lease, lease))
+                        r = SD_DHCP_CLIENT_EVENT_RENEW;
+                else
+                        r = SD_DHCP_CLIENT_EVENT_IP_CHANGE;
+
+                client->lease = sd_dhcp_lease_unref(client->lease);
+        }
+
+        client->lease = TAKE_PTR(lease);
+
+        log_dhcp_client(client, "ACK");
+
+        return r;
+}
+
+static int client_set_lease_timeouts(sd_dhcp_client *client) {
+        usec_t time_now;
+        int r;
+
+        assert(client);
+        assert(client->event);
+        assert(client->lease);
+        assert(client->lease->lifetime);
+
+        /* don't set timers for infinite leases */
+        if (client->lease->lifetime == 0xffffffff) {
+                (void) event_source_disable(client->timeout_t1);
+                (void) event_source_disable(client->timeout_t2);
+                (void) event_source_disable(client->timeout_expire);
+
+                return 0;
+        }
+
+        r = sd_event_now(client->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                return r;
+        assert(client->request_sent <= time_now);
+
+        /* verify that 0 < t2 < lifetime */
+        if (client->lease->t2 == 0 || client->lease->t2 >= client->lease->lifetime)
+                client->lease->t2 = T2_DEFAULT(client->lease->lifetime);
+        /* verify that 0 < t1 < lifetime */
+        if (client->lease->t1 == 0 || client->lease->t1 >= client->lease->t2)
+                client->lease->t1 = T1_DEFAULT(client->lease->lifetime);
+        /* now, if t1 >= t2, t1 *must* be T1_DEFAULT, since the previous check
+         * could not evalate to false if t1 >= t2; so setting t2 to T2_DEFAULT
+         * guarantees t1 < t2. */
+        if (client->lease->t1 >= client->lease->t2)
+                client->lease->t2 = T2_DEFAULT(client->lease->lifetime);
+
+        client->expire_time = client->request_sent + client->lease->lifetime * USEC_PER_SEC;
+        client->t1_time = client->request_sent + client->lease->t1 * USEC_PER_SEC;
+        client->t2_time = client->request_sent + client->lease->t2 * USEC_PER_SEC;
+
+        /* RFC2131 section 4.4.5:
+         * Times T1 and T2 SHOULD be chosen with some random "fuzz".
+         * Since the RFC doesn't specify here the exact 'fuzz' to use,
+         * we use the range from section 4.1: -1 to +1 sec. */
+        client->t1_time = usec_sub_signed(client->t1_time, RFC2131_RANDOM_FUZZ);
+        client->t2_time = usec_sub_signed(client->t2_time, RFC2131_RANDOM_FUZZ);
+
+        /* after fuzzing, ensure t2 is still >= t1 */
+        client->t2_time = MAX(client->t1_time, client->t2_time);
+
+        /* arm lifetime timeout */
+        r = event_reset_time(client->event, &client->timeout_expire,
+                             CLOCK_BOOTTIME,
+                             client->expire_time, 10 * USEC_PER_MSEC,
+                             client_timeout_expire, client,
+                             client->event_priority, "dhcp4-lifetime", true);
+        if (r < 0)
+                return r;
+
+        /* don't arm earlier timeouts if this has already expired */
+        if (client->expire_time <= time_now)
+                return 0;
+
+        log_dhcp_client(client, "lease expires in %s",
+                        FORMAT_TIMESPAN(client->expire_time - time_now, USEC_PER_SEC));
+
+        /* arm T2 timeout */
+        r = event_reset_time(client->event, &client->timeout_t2,
+                             CLOCK_BOOTTIME,
+                             client->t2_time, 10 * USEC_PER_MSEC,
+                             client_timeout_t2, client,
+                             client->event_priority, "dhcp4-t2-timeout", true);
+        if (r < 0)
+                return r;
+
+        /* don't arm earlier timeout if this has already expired */
+        if (client->t2_time <= time_now)
+                return 0;
+
+        log_dhcp_client(client, "T2 expires in %s",
+                        FORMAT_TIMESPAN(client->t2_time - time_now, USEC_PER_SEC));
+
+        /* arm T1 timeout */
+        r = event_reset_time(client->event, &client->timeout_t1,
+                             CLOCK_BOOTTIME,
+                             client->t1_time, 10 * USEC_PER_MSEC,
+                             client_timeout_t1, client,
+                             client->event_priority, "dhcp4-t1-timer", true);
+        if (r < 0)
+                return r;
+
+        if (client->t1_time > time_now)
+                log_dhcp_client(client, "T1 expires in %s",
+                                FORMAT_TIMESPAN(client->t1_time - time_now, USEC_PER_SEC));
+
+        return 0;
+}
+
+static int client_handle_message(sd_dhcp_client *client, DHCPMessage *message, int len) {
+        DHCP_CLIENT_DONT_DESTROY(client);
+        int r, notify_event;
+
+        assert(client);
+        assert(client->event);
+        assert(message);
+
+        switch (client->state) {
+        case DHCP_STATE_SELECTING:
+
+                r = client_handle_offer(client, message, len);
+                if (r == -ENOMSG)
+                        return 0; /* invalid message, let's ignore it */
+                if (r < 0)
+                        goto error;
+
+                client->state = DHCP_STATE_REQUESTING;
+                client->attempt = 0;
+
+                r = event_reset_time(client->event, &client->timeout_resend,
+                                     CLOCK_BOOTTIME,
+                                     0, 0,
+                                     client_timeout_resend, client,
+                                     client->event_priority, "dhcp4-resend-timer", true);
+                break;
+
+        case DHCP_STATE_REBOOTING:
+        case DHCP_STATE_REQUESTING:
+        case DHCP_STATE_RENEWING:
+        case DHCP_STATE_REBINDING:
+
+                r = client_handle_ack(client, message, len);
+                if (r == -ENOMSG)
+                        return 0; /* invalid message, let's ignore it */
+                if (r == -EADDRNOTAVAIL) {
+                        /* got a NAK, let's restart the client */
+                        client_notify(client, SD_DHCP_CLIENT_EVENT_EXPIRED);
+
+                        r = client_initialize(client);
+                        if (r < 0)
+                                goto error;
+
+                        r = client_start_delayed(client);
+                        if (r < 0)
+                                goto error;
+
+                        log_dhcp_client(client, "REBOOT in %s", FORMAT_TIMESPAN(client->start_delay, USEC_PER_SEC));
+
+                        client->start_delay = CLAMP(client->start_delay * 2,
+                                                    RESTART_AFTER_NAK_MIN_USEC, RESTART_AFTER_NAK_MAX_USEC);
+                        return 0;
+                }
+                if (r < 0)
+                        goto error;
+
+                if (IN_SET(client->state, DHCP_STATE_REQUESTING, DHCP_STATE_REBOOTING))
+                        notify_event = SD_DHCP_CLIENT_EVENT_IP_ACQUIRE;
+                else
+                        notify_event = r;
+
+                client->start_delay = 0;
+                (void) event_source_disable(client->timeout_resend);
+                client->receive_message = sd_event_source_disable_unref(client->receive_message);
+                client->fd = safe_close(client->fd);
+
+                client->state = DHCP_STATE_BOUND;
+                client->attempt = 0;
+
+                client->last_addr = client->lease->address;
+
+                r = client_set_lease_timeouts(client);
+                if (r < 0) {
+                        log_dhcp_client(client, "could not set lease timeouts");
+                        goto error;
+                }
+
+                r = dhcp_network_bind_udp_socket(client->ifindex, client->lease->address, client->port, client->ip_service_type);
+                if (r < 0) {
+                        log_dhcp_client(client, "could not bind UDP socket");
+                        goto error;
+                }
+
+                client->fd = r;
+
+                client_initialize_io_events(client, client_receive_message_udp);
+
+                if (IN_SET(client->state, DHCP_STATE_RENEWING, DHCP_STATE_REBINDING) &&
+                    notify_event == SD_DHCP_CLIENT_EVENT_IP_ACQUIRE)
+                        /* FIXME: hmm, maybe this is a bug... */
+                        log_dhcp_client(client, "client_handle_ack() returned SD_DHCP_CLIENT_EVENT_IP_ACQUIRE while DHCP client is %s the address, skipping callback.",
+                                        client->state == DHCP_STATE_RENEWING ? "renewing" : "rebinding");
+                else
+                        client_notify(client, notify_event);
+                break;
+
+        case DHCP_STATE_BOUND:
+                r = client_handle_forcerenew(client, message, len);
+                if (r == -ENOMSG)
+                        return 0; /* invalid message, let's ignore it */
+                if (r < 0)
+                        goto error;
+
+                r = client_timeout_t1(NULL, 0, client);
+                break;
+
+        case DHCP_STATE_INIT:
+        case DHCP_STATE_INIT_REBOOT:
+                r = 0;
+                break;
+
+        case DHCP_STATE_STOPPED:
+                r = -EINVAL;
+                goto error;
+        default:
+                assert_not_reached();
+        }
+
+error:
+        if (r < 0)
+                client_stop(client, r);
+
+        return r;
+}
+
+static int client_receive_message_udp(
+                sd_event_source *s,
+                int fd,
+                uint32_t revents,
+                void *userdata) {
+
+        sd_dhcp_client *client = ASSERT_PTR(userdata);
+        _cleanup_free_ DHCPMessage *message = NULL;
+        const uint8_t *expected_chaddr = NULL;
+        uint8_t expected_hlen = 0;
+        ssize_t len, buflen;
+
+        assert(s);
+
+        buflen = next_datagram_size_fd(fd);
+        if (buflen < 0) {
+                if (ERRNO_IS_TRANSIENT(buflen) || ERRNO_IS_DISCONNECT(buflen))
+                        return 0;
+
+                log_dhcp_client_errno(client, buflen, "Failed to determine datagram size to read, ignoring: %m");
+                return 0;
+        }
+
+        message = malloc0(buflen);
+        if (!message)
+                return -ENOMEM;
+
+        len = recv(fd, message, buflen, 0);
+        if (len < 0) {
+                if (ERRNO_IS_TRANSIENT(errno) || ERRNO_IS_DISCONNECT(errno))
+                        return 0;
+
+                log_dhcp_client_errno(client, errno, "Could not receive message from UDP socket, ignoring: %m");
+                return 0;
+        }
+        if ((size_t) len < sizeof(DHCPMessage)) {
+                log_dhcp_client(client, "Too small to be a DHCP message: ignoring");
+                return 0;
+        }
+
+        if (be32toh(message->magic) != DHCP_MAGIC_COOKIE) {
+                log_dhcp_client(client, "Not a DHCP message: ignoring");
+                return 0;
+        }
+
+        if (message->op != BOOTREPLY) {
+                log_dhcp_client(client, "Not a BOOTREPLY message: ignoring");
+                return 0;
+        }
+
+        if (message->htype != client->arp_type) {
+                log_dhcp_client(client, "Packet type does not match client type");
+                return 0;
+        }
+
+        if (client->arp_type == ARPHRD_ETHER) {
+                expected_hlen = ETH_ALEN;
+                expected_chaddr = client->hw_addr.bytes;
+        }
+
+        if (message->hlen != expected_hlen) {
+                log_dhcp_client(client, "Unexpected packet hlen %d", message->hlen);
+                return 0;
+        }
+
+        if (expected_hlen > 0 && memcmp(&message->chaddr[0], expected_chaddr, expected_hlen)) {
+                log_dhcp_client(client, "Received chaddr does not match expected: ignoring");
+                return 0;
+        }
+
+        if (client->state != DHCP_STATE_BOUND &&
+            be32toh(message->xid) != client->xid) {
+                /* in BOUND state, we may receive FORCERENEW with xid set by server,
+                   so ignore the xid in this case */
+                log_dhcp_client(client, "Received xid (%u) does not match expected (%u): ignoring",
+                                be32toh(message->xid), client->xid);
+                return 0;
+        }
+
+        log_dhcp_client(client, "Received message from UDP socket, processing.");
+        (void) client_handle_message(client, message, len);
+        return 0;
+}
+
+static int client_receive_message_raw(
+                sd_event_source *s,
+                int fd,
+                uint32_t revents,
+                void *userdata) {
+
+        sd_dhcp_client *client = ASSERT_PTR(userdata);
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct tpacket_auxdata))) control;
+        struct iovec iov = {};
+        struct msghdr msg = {
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+        };
+        struct cmsghdr *cmsg;
+        bool checksum = true;
+        ssize_t buflen, len;
+        int r;
+
+        assert(s);
+
+        buflen = next_datagram_size_fd(fd);
+        if (buflen < 0) {
+                if (ERRNO_IS_TRANSIENT(buflen) || ERRNO_IS_DISCONNECT(buflen))
+                        return 0;
+
+                log_dhcp_client_errno(client, buflen, "Failed to determine datagram size to read, ignoring: %m");
+                return 0;
+        }
+
+        packet = malloc0(buflen);
+        if (!packet)
+                return -ENOMEM;
+
+        iov = IOVEC_MAKE(packet, buflen);
+
+        len = recvmsg_safe(fd, &msg, 0);
+        if (len < 0) {
+                if (ERRNO_IS_TRANSIENT(len) || ERRNO_IS_DISCONNECT(len))
+                        return 0;
+
+                log_dhcp_client_errno(client, len, "Could not receive message from raw socket, ignoring: %m");
+                return 0;
+        }
+        if ((size_t) len < sizeof(DHCPPacket))
+                return 0;
+
+        cmsg = cmsg_find(&msg, SOL_PACKET, PACKET_AUXDATA, CMSG_LEN(sizeof(struct tpacket_auxdata)));
+        if (cmsg) {
+                struct tpacket_auxdata *aux = (struct tpacket_auxdata*) CMSG_DATA(cmsg);
+                checksum = !(aux->tp_status & TP_STATUS_CSUMNOTREADY);
+        }
+
+        r = dhcp_packet_verify_headers(packet, len, checksum, client->port);
+        if (r < 0)
+                return 0;
+
+        len -= DHCP_IP_UDP_SIZE;
+
+        log_dhcp_client(client, "Received message from RAW socket, processing.");
+        (void) client_handle_message(client, &packet->dhcp, len);
+        return 0;
+}
+
+int sd_dhcp_client_send_renew(sd_dhcp_client *client) {
+        assert_return(client, -EINVAL);
+        assert_return(sd_dhcp_client_is_running(client), -ESTALE);
+        assert_return(client->fd >= 0, -EINVAL);
+
+        if (!client->lease)
+                return 0;
+
+        client->start_delay = 0;
+        client->attempt = 1;
+        client->state = DHCP_STATE_RENEWING;
+
+        return client_initialize_time_events(client);
+}
+
+int sd_dhcp_client_is_running(sd_dhcp_client *client) {
+        if (!client)
+                return 0;
+
+        return !IN_SET(client->state, DHCP_STATE_INIT, DHCP_STATE_STOPPED);
+}
+
+int sd_dhcp_client_start(sd_dhcp_client *client) {
+        int r;
+
+        assert_return(client, -EINVAL);
+
+        r = client_initialize(client);
+        if (r < 0)
+                return r;
+
+        /* RFC7844 section 3.3:
+           SHOULD perform a complete four-way handshake, starting with a
+           DHCPDISCOVER, to obtain a new address lease.  If the client can
+           ascertain that this is exactly the same network to which it was
+           previously connected, and if the link-layer address did not change,
+           the client MAY issue a DHCPREQUEST to try to reclaim the current
+           address. */
+        if (client->last_addr && !client->anonymize)
+                client->state = DHCP_STATE_INIT_REBOOT;
+
+        r = client_start(client);
+        if (r >= 0)
+                log_dhcp_client(client, "STARTED on ifindex %i", client->ifindex);
+
+        return r;
+}
+
+int sd_dhcp_client_send_release(sd_dhcp_client *client) {
+        assert_return(client, -EINVAL);
+        assert_return(sd_dhcp_client_is_running(client), -ESTALE);
+        assert_return(client->lease, -EUNATCH);
+
+        _cleanup_free_ DHCPPacket *release = NULL;
+        size_t optoffset, optlen;
+        int r;
+
+        r = client_message_init(client, &release, DHCP_RELEASE, &optlen, &optoffset);
+        if (r < 0)
+                return r;
+
+        /* Fill up release IP and MAC */
+        release->dhcp.ciaddr = client->lease->address;
+        memcpy(&release->dhcp.chaddr, client->hw_addr.bytes, client->hw_addr.length);
+
+        r = dhcp_option_append(&release->dhcp, optlen, &optoffset, 0,
+                               SD_DHCP_OPTION_END, 0, NULL);
+        if (r < 0)
+                return r;
+
+        r = dhcp_network_send_udp_socket(client->fd,
+                                         client->lease->server_address,
+                                         DHCP_PORT_SERVER,
+                                         &release->dhcp,
+                                         sizeof(DHCPMessage) + optoffset);
+        if (r < 0)
+                return r;
+
+        log_dhcp_client(client, "RELEASE");
+
+        return 0;
+}
+
+int sd_dhcp_client_send_decline(sd_dhcp_client *client) {
+        assert_return(client, -EINVAL);
+        assert_return(sd_dhcp_client_is_running(client), -ESTALE);
+        assert_return(client->lease, -EUNATCH);
+
+        _cleanup_free_ DHCPPacket *release = NULL;
+        size_t optoffset, optlen;
+        int r;
+
+        r = client_message_init(client, &release, DHCP_DECLINE, &optlen, &optoffset);
+        if (r < 0)
+                return r;
+
+        release->dhcp.ciaddr = client->lease->address;
+        memcpy(&release->dhcp.chaddr, client->hw_addr.bytes, client->hw_addr.length);
+
+        r = dhcp_option_append(&release->dhcp, optlen, &optoffset, 0,
+                               SD_DHCP_OPTION_END, 0, NULL);
+        if (r < 0)
+                return r;
+
+        r = dhcp_network_send_udp_socket(client->fd,
+                                         client->lease->server_address,
+                                         DHCP_PORT_SERVER,
+                                         &release->dhcp,
+                                         sizeof(DHCPMessage) + optoffset);
+        if (r < 0)
+                return r;
+
+        log_dhcp_client(client, "DECLINE");
+
+        client_stop(client, SD_DHCP_CLIENT_EVENT_STOP);
+
+        if (client->state != DHCP_STATE_STOPPED) {
+                r = sd_dhcp_client_start(client);
+                if (r < 0)
+                        return r;
+        }
+
+        return 0;
+}
+
+int sd_dhcp_client_stop(sd_dhcp_client *client) {
+        if (!client)
+                return 0;
+
+        DHCP_CLIENT_DONT_DESTROY(client);
+
+        client_stop(client, SD_DHCP_CLIENT_EVENT_STOP);
+        client->state = DHCP_STATE_STOPPED;
+
+        return 0;
+}
+
+int sd_dhcp_client_attach_event(sd_dhcp_client *client, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!client->event, -EBUSY);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        if (event)
+                client->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&client->event);
+                if (r < 0)
+                        return 0;
+        }
+
+        client->event_priority = priority;
+
+        return 0;
+}
+
+int sd_dhcp_client_detach_event(sd_dhcp_client *client) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp_client_is_running(client), -EBUSY);
+
+        client->event = sd_event_unref(client->event);
+
+        return 0;
+}
+
+sd_event *sd_dhcp_client_get_event(sd_dhcp_client *client) {
+        assert_return(client, NULL);
+
+        return client->event;
+}
+
+static sd_dhcp_client *dhcp_client_free(sd_dhcp_client *client) {
+        if (!client)
+                return NULL;
+
+        log_dhcp_client(client, "FREE");
+
+        client_initialize(client);
+
+        client->timeout_resend = sd_event_source_unref(client->timeout_resend);
+        client->timeout_t1 = sd_event_source_unref(client->timeout_t1);
+        client->timeout_t2 = sd_event_source_unref(client->timeout_t2);
+        client->timeout_expire = sd_event_source_unref(client->timeout_expire);
+
+        sd_dhcp_client_detach_event(client);
+
+        set_free(client->req_opts);
+        free(client->hostname);
+        free(client->vendor_class_identifier);
+        free(client->mudurl);
+        client->user_class = strv_free(client->user_class);
+        ordered_hashmap_free(client->extra_options);
+        ordered_hashmap_free(client->vendor_options);
+        free(client->ifname);
+        return mfree(client);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp_client, sd_dhcp_client, dhcp_client_free);
+
+int sd_dhcp_client_new(sd_dhcp_client **ret, int anonymize) {
+        const uint8_t *opts;
+        size_t n_opts;
+        int r;
+
+        assert_return(ret, -EINVAL);
+
+        _cleanup_(sd_dhcp_client_unrefp) sd_dhcp_client *client = new(sd_dhcp_client, 1);
+        if (!client)
+                return -ENOMEM;
+
+        *client = (sd_dhcp_client) {
+                .n_ref = 1,
+                .state = DHCP_STATE_INIT,
+                .ifindex = -1,
+                .fd = -1,
+                .mtu = DHCP_MIN_PACKET_SIZE,
+                .port = DHCP_PORT_CLIENT,
+                .anonymize = !!anonymize,
+                .max_attempts = UINT64_MAX,
+                .ip_service_type = -1,
+        };
+        /* NOTE: this could be moved to a function. */
+        if (anonymize) {
+                n_opts = ELEMENTSOF(default_req_opts_anonymize);
+                opts = default_req_opts_anonymize;
+        } else {
+                n_opts = ELEMENTSOF(default_req_opts);
+                opts = default_req_opts;
+        }
+
+        for (size_t i = 0; i < n_opts; i++) {
+                r = sd_dhcp_client_set_request_option(client, opts[i]);
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(client);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-dhcp-lease.c b/src/libsystemd-network/sd-dhcp-lease.c
new file mode 100644
index 0000000..c6515b4
--- /dev/null
+++ b/src/libsystemd-network/sd-dhcp-lease.c
@@ -0,0 +1,1506 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "sd-dhcp-lease.h"
+
+#include "alloc-util.h"
+#include "dhcp-lease-internal.h"
+#include "dhcp-protocol.h"
+#include "dns-domain.h"
+#include "env-file.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "hexdecoct.h"
+#include "hostname-util.h"
+#include "in-addr-util.h"
+#include "network-internal.h"
+#include "parse-util.h"
+#include "stdio-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "tmpfile-util.h"
+#include "unaligned.h"
+
+int sd_dhcp_lease_get_address(sd_dhcp_lease *lease, struct in_addr *addr) {
+        assert_return(lease, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        if (lease->address == 0)
+                return -ENODATA;
+
+        addr->s_addr = lease->address;
+        return 0;
+}
+
+int sd_dhcp_lease_get_broadcast(sd_dhcp_lease *lease, struct in_addr *addr) {
+        assert_return(lease, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        if (!lease->have_broadcast)
+                return -ENODATA;
+
+        addr->s_addr = lease->broadcast;
+        return 0;
+}
+
+int sd_dhcp_lease_get_lifetime(sd_dhcp_lease *lease, uint32_t *lifetime) {
+        assert_return(lease, -EINVAL);
+        assert_return(lifetime, -EINVAL);
+
+        if (lease->lifetime <= 0)
+                return -ENODATA;
+
+        *lifetime = lease->lifetime;
+        return 0;
+}
+
+int sd_dhcp_lease_get_t1(sd_dhcp_lease *lease, uint32_t *t1) {
+        assert_return(lease, -EINVAL);
+        assert_return(t1, -EINVAL);
+
+        if (lease->t1 <= 0)
+                return -ENODATA;
+
+        *t1 = lease->t1;
+        return 0;
+}
+
+int sd_dhcp_lease_get_t2(sd_dhcp_lease *lease, uint32_t *t2) {
+        assert_return(lease, -EINVAL);
+        assert_return(t2, -EINVAL);
+
+        if (lease->t2 <= 0)
+                return -ENODATA;
+
+        *t2 = lease->t2;
+        return 0;
+}
+
+int sd_dhcp_lease_get_mtu(sd_dhcp_lease *lease, uint16_t *mtu) {
+        assert_return(lease, -EINVAL);
+        assert_return(mtu, -EINVAL);
+
+        if (lease->mtu <= 0)
+                return -ENODATA;
+
+        *mtu = lease->mtu;
+        return 0;
+}
+
+int sd_dhcp_lease_get_servers(
+                sd_dhcp_lease *lease,
+                sd_dhcp_lease_server_type_t what,
+                const struct in_addr **addr) {
+
+        assert_return(lease, -EINVAL);
+        assert_return(what >= 0, -EINVAL);
+        assert_return(what < _SD_DHCP_LEASE_SERVER_TYPE_MAX, -EINVAL);
+
+        if (lease->servers[what].size <= 0)
+                return -ENODATA;
+
+        if (addr)
+                *addr = lease->servers[what].addr;
+
+        return (int) lease->servers[what].size;
+}
+
+int sd_dhcp_lease_get_dns(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        return sd_dhcp_lease_get_servers(lease, SD_DHCP_LEASE_DNS, addr);
+}
+int sd_dhcp_lease_get_ntp(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        return sd_dhcp_lease_get_servers(lease, SD_DHCP_LEASE_NTP, addr);
+}
+int sd_dhcp_lease_get_sip(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        return sd_dhcp_lease_get_servers(lease, SD_DHCP_LEASE_SIP, addr);
+}
+int sd_dhcp_lease_get_pop3(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        return sd_dhcp_lease_get_servers(lease, SD_DHCP_LEASE_POP3, addr);
+}
+int sd_dhcp_lease_get_smtp(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        return sd_dhcp_lease_get_servers(lease, SD_DHCP_LEASE_SMTP, addr);
+}
+int sd_dhcp_lease_get_lpr(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        return sd_dhcp_lease_get_servers(lease, SD_DHCP_LEASE_LPR, addr);
+}
+
+int sd_dhcp_lease_get_domainname(sd_dhcp_lease *lease, const char **domainname) {
+        assert_return(lease, -EINVAL);
+        assert_return(domainname, -EINVAL);
+
+        if (!lease->domainname)
+                return -ENODATA;
+
+        *domainname = lease->domainname;
+        return 0;
+}
+
+int sd_dhcp_lease_get_hostname(sd_dhcp_lease *lease, const char **hostname) {
+        assert_return(lease, -EINVAL);
+        assert_return(hostname, -EINVAL);
+
+        if (!lease->hostname)
+                return -ENODATA;
+
+        *hostname = lease->hostname;
+        return 0;
+}
+
+int sd_dhcp_lease_get_root_path(sd_dhcp_lease *lease, const char **root_path) {
+        assert_return(lease, -EINVAL);
+        assert_return(root_path, -EINVAL);
+
+        if (!lease->root_path)
+                return -ENODATA;
+
+        *root_path = lease->root_path;
+        return 0;
+}
+
+int sd_dhcp_lease_get_router(sd_dhcp_lease *lease, const struct in_addr **addr) {
+        assert_return(lease, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        if (lease->router_size <= 0)
+                return -ENODATA;
+
+        *addr = lease->router;
+        return (int) lease->router_size;
+}
+
+int sd_dhcp_lease_get_netmask(sd_dhcp_lease *lease, struct in_addr *addr) {
+        assert_return(lease, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        if (!lease->have_subnet_mask)
+                return -ENODATA;
+
+        addr->s_addr = lease->subnet_mask;
+        return 0;
+}
+
+int sd_dhcp_lease_get_server_identifier(sd_dhcp_lease *lease, struct in_addr *addr) {
+        assert_return(lease, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        if (lease->server_address == 0)
+                return -ENODATA;
+
+        addr->s_addr = lease->server_address;
+        return 0;
+}
+
+int sd_dhcp_lease_get_next_server(sd_dhcp_lease *lease, struct in_addr *addr) {
+        assert_return(lease, -EINVAL);
+        assert_return(addr, -EINVAL);
+
+        if (lease->next_server == 0)
+                return -ENODATA;
+
+        addr->s_addr = lease->next_server;
+        return 0;
+}
+
+/*
+ * The returned routes array must be freed by the caller.
+ * Route objects have the same lifetime of the lease and must not be freed.
+ */
+static int dhcp_lease_get_routes(sd_dhcp_route *routes, size_t n_routes, sd_dhcp_route ***ret) {
+        assert(routes || n_routes == 0);
+
+        if (n_routes <= 0)
+                return -ENODATA;
+
+        if (ret) {
+                sd_dhcp_route **buf;
+
+                buf = new(sd_dhcp_route*, n_routes);
+                if (!buf)
+                        return -ENOMEM;
+
+                for (size_t i = 0; i < n_routes; i++)
+                        buf[i] = &routes[i];
+
+                *ret = buf;
+        }
+
+        return (int) n_routes;
+}
+
+int sd_dhcp_lease_get_static_routes(sd_dhcp_lease *lease, sd_dhcp_route ***ret) {
+        assert_return(lease, -EINVAL);
+
+        return dhcp_lease_get_routes(lease->static_routes, lease->n_static_routes, ret);
+}
+
+int sd_dhcp_lease_get_classless_routes(sd_dhcp_lease *lease, sd_dhcp_route ***ret) {
+        assert_return(lease, -EINVAL);
+
+        return dhcp_lease_get_routes(lease->classless_routes, lease->n_classless_routes, ret);
+}
+
+int sd_dhcp_lease_get_search_domains(sd_dhcp_lease *lease, char ***domains) {
+        size_t r;
+
+        assert_return(lease, -EINVAL);
+        assert_return(domains, -EINVAL);
+
+        r = strv_length(lease->search_domains);
+        if (r > 0) {
+                *domains = lease->search_domains;
+                return (int) r;
+        }
+
+        return -ENODATA;
+}
+
+int sd_dhcp_lease_get_6rd(
+                sd_dhcp_lease *lease,
+                uint8_t *ret_ipv4masklen,
+                uint8_t *ret_prefixlen,
+                struct in6_addr *ret_prefix,
+                const struct in_addr **ret_br_addresses,
+                size_t *ret_n_br_addresses) {
+
+        assert_return(lease, -EINVAL);
+
+        if (lease->sixrd_n_br_addresses <= 0)
+                return -ENODATA;
+
+        if (ret_ipv4masklen)
+                *ret_ipv4masklen = lease->sixrd_ipv4masklen;
+        if (ret_prefixlen)
+                *ret_prefixlen = lease->sixrd_prefixlen;
+        if (ret_prefix)
+                *ret_prefix = lease->sixrd_prefix;
+        if (ret_br_addresses)
+                *ret_br_addresses = lease->sixrd_br_addresses;
+        if (ret_n_br_addresses)
+                *ret_n_br_addresses = lease->sixrd_n_br_addresses;
+
+        return 0;
+}
+
+int sd_dhcp_lease_get_vendor_specific(sd_dhcp_lease *lease, const void **data, size_t *data_len) {
+        assert_return(lease, -EINVAL);
+        assert_return(data, -EINVAL);
+        assert_return(data_len, -EINVAL);
+
+        if (lease->vendor_specific_len <= 0)
+                return -ENODATA;
+
+        *data = lease->vendor_specific;
+        *data_len = lease->vendor_specific_len;
+        return 0;
+}
+
+static sd_dhcp_lease *dhcp_lease_free(sd_dhcp_lease *lease) {
+        assert(lease);
+
+        while (lease->private_options) {
+                struct sd_dhcp_raw_option *option = lease->private_options;
+
+                LIST_REMOVE(options, lease->private_options, option);
+
+                free(option->data);
+                free(option);
+        }
+
+        free(lease->root_path);
+        free(lease->router);
+        free(lease->timezone);
+        free(lease->hostname);
+        free(lease->domainname);
+
+        for (sd_dhcp_lease_server_type_t i = 0; i < _SD_DHCP_LEASE_SERVER_TYPE_MAX; i++)
+                free(lease->servers[i].addr);
+
+        free(lease->static_routes);
+        free(lease->classless_routes);
+        free(lease->client_id);
+        free(lease->vendor_specific);
+        strv_free(lease->search_domains);
+        free(lease->sixrd_br_addresses);
+        return mfree(lease);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp_lease, sd_dhcp_lease, dhcp_lease_free);
+
+static int lease_parse_u32(const uint8_t *option, size_t len, uint32_t *ret, uint32_t min) {
+        assert(option);
+        assert(ret);
+
+        if (len != 4)
+                return -EINVAL;
+
+        *ret = unaligned_read_be32((be32_t*) option);
+        if (*ret < min)
+                *ret = min;
+
+        return 0;
+}
+
+static int lease_parse_u16(const uint8_t *option, size_t len, uint16_t *ret, uint16_t min) {
+        assert(option);
+        assert(ret);
+
+        if (len != 2)
+                return -EINVAL;
+
+        *ret = unaligned_read_be16((be16_t*) option);
+        if (*ret < min)
+                *ret = min;
+
+        return 0;
+}
+
+static int lease_parse_be32(const uint8_t *option, size_t len, be32_t *ret) {
+        assert(option);
+        assert(ret);
+
+        if (len != 4)
+                return -EINVAL;
+
+        memcpy(ret, option, 4);
+        return 0;
+}
+
+static int lease_parse_string(const uint8_t *option, size_t len, char **ret) {
+        assert(option);
+        assert(ret);
+
+        if (len <= 0)
+                *ret = mfree(*ret);
+        else {
+                char *string;
+
+                /*
+                 * One trailing NUL byte is OK, we don't mind. See:
+                 * https://github.com/systemd/systemd/issues/1337
+                 */
+                if (memchr(option, 0, len - 1))
+                        return -EINVAL;
+
+                string = memdup_suffix0((const char *) option, len);
+                if (!string)
+                        return -ENOMEM;
+
+                free_and_replace(*ret, string);
+        }
+
+        return 0;
+}
+
+static int lease_parse_domain(const uint8_t *option, size_t len, char **ret) {
+        _cleanup_free_ char *name = NULL, *normalized = NULL;
+        int r;
+
+        assert(option);
+        assert(ret);
+
+        r = lease_parse_string(option, len, &name);
+        if (r < 0)
+                return r;
+        if (!name) {
+                *ret = mfree(*ret);
+                return 0;
+        }
+
+        r = dns_name_normalize(name, 0, &normalized);
+        if (r < 0)
+                return r;
+
+        if (is_localhost(normalized))
+                return -EINVAL;
+
+        if (dns_name_is_root(normalized))
+                return -EINVAL;
+
+        free_and_replace(*ret, normalized);
+
+        return 0;
+}
+
+static int lease_parse_in_addrs(const uint8_t *option, size_t len, struct in_addr **ret, size_t *n_ret) {
+        assert(option || len == 0);
+        assert(ret);
+        assert(n_ret);
+
+        if (len <= 0) {
+                *ret = mfree(*ret);
+                *n_ret = 0;
+        } else {
+                size_t n_addresses;
+                struct in_addr *addresses;
+
+                if (len % 4 != 0)
+                        return -EINVAL;
+
+                n_addresses = len / 4;
+
+                addresses = newdup(struct in_addr, option, n_addresses);
+                if (!addresses)
+                        return -ENOMEM;
+
+                free(*ret);
+                *ret = addresses;
+                *n_ret = n_addresses;
+        }
+
+        return 0;
+}
+
+static int lease_parse_sip_server(const uint8_t *option, size_t len, struct in_addr **ret, size_t *n_ret) {
+        assert(option || len == 0);
+        assert(ret);
+        assert(n_ret);
+
+        if (len <= 0)
+                return -EINVAL;
+
+        /* The SIP record is like the other, regular server records, but prefixed with a single "encoding"
+         * byte that is either 0 or 1. We only support it to be 1 for now. Let's drop it and parse it like
+         * the other fields */
+
+        if (option[0] != 1) { /* We only support IP address encoding for now */
+                *ret = mfree(*ret);
+                *n_ret = 0;
+                return 0;
+        }
+
+        return lease_parse_in_addrs(option + 1, len - 1, ret, n_ret);
+}
+
+static int lease_parse_static_routes(sd_dhcp_lease *lease, const uint8_t *option, size_t len) {
+        int r;
+
+        assert(lease);
+        assert(option || len <= 0);
+
+        if (len % 8 != 0)
+                return -EINVAL;
+
+        while (len >= 8) {
+                struct in_addr dst, gw;
+                uint8_t prefixlen;
+
+                assert_se(lease_parse_be32(option, 4, &dst.s_addr) >= 0);
+                option += 4;
+
+                assert_se(lease_parse_be32(option, 4, &gw.s_addr) >= 0);
+                option += 4;
+
+                len -= 8;
+
+                r = in4_addr_default_prefixlen(&dst, &prefixlen);
+                if (r < 0) {
+                        log_debug("sd-dhcp-lease: cannot determine class of received static route, ignoring.");
+                        continue;
+                }
+
+                (void) in4_addr_mask(&dst, prefixlen);
+
+                if (!GREEDY_REALLOC(lease->static_routes, lease->n_static_routes + 1))
+                        return -ENOMEM;
+
+                lease->static_routes[lease->n_static_routes++] = (struct sd_dhcp_route) {
+                        .dst_addr = dst,
+                        .gw_addr = gw,
+                        .dst_prefixlen = prefixlen,
+                };
+        }
+
+        return 0;
+}
+
+/* parses RFC3442 Classless Static Route Option */
+static int lease_parse_classless_routes(sd_dhcp_lease *lease, const uint8_t *option, size_t len) {
+        assert(lease);
+        assert(option || len <= 0);
+
+        /* option format: (subnet-mask-width significant-subnet-octets gateway-ip) */
+
+        while (len > 0) {
+                uint8_t prefixlen, dst_octets;
+                struct in_addr dst = {}, gw;
+
+                prefixlen = *option;
+                option++;
+                len--;
+
+                dst_octets = DIV_ROUND_UP(prefixlen, 8);
+
+                /* can't have more than 4 octets in IPv4 */
+                if (dst_octets > 4 || len < dst_octets)
+                        return -EINVAL;
+
+                memcpy(&dst, option, dst_octets);
+                option += dst_octets;
+                len -= dst_octets;
+
+                if (len < 4)
+                        return -EINVAL;
+
+                assert_se(lease_parse_be32(option, 4, &gw.s_addr) >= 0);
+                option += 4;
+                len -= 4;
+
+                if (!GREEDY_REALLOC(lease->classless_routes, lease->n_classless_routes + 1))
+                        return -ENOMEM;
+
+                lease->classless_routes[lease->n_classless_routes++] = (struct sd_dhcp_route) {
+                        .dst_addr = dst,
+                        .gw_addr = gw,
+                        .dst_prefixlen = prefixlen,
+                };
+        }
+
+        return 0;
+}
+
+static int lease_parse_6rd(sd_dhcp_lease *lease, const uint8_t *option, size_t len) {
+        uint8_t ipv4masklen, prefixlen;
+        struct in6_addr prefix;
+        _cleanup_free_ struct in_addr *br_addresses = NULL;
+        size_t n_br_addresses;
+
+        assert(lease);
+        assert(option);
+
+        /* See RFC 5969 Section 7.1.1 */
+
+        if (lease->sixrd_n_br_addresses > 0)
+                /* Multiple 6rd option?? */
+                return -EINVAL;
+
+        /* option-length: The length of the DHCP option in octets (22 octets with one BR IPv4 address). */
+        if (len < 2 + sizeof(struct in6_addr) + sizeof(struct in_addr) ||
+            (len - 2 - sizeof(struct in6_addr)) % sizeof(struct in_addr) != 0)
+                return -EINVAL;
+
+        /* IPv4MaskLen: The number of high-order bits that are identical across all CE IPv4 addresses
+         *              within a given 6rd domain. This may be any value between 0 and 32. Any value
+         *              greater than 32 is invalid. */
+        ipv4masklen = option[0];
+        if (ipv4masklen > 32)
+                return -EINVAL;
+
+        /* 6rdPrefixLen: The IPv6 prefix length of the SP's 6rd IPv6 prefix in number of bits. For the
+         *               purpose of bounds checking by DHCP option processing, the sum of
+         *               (32 - IPv4MaskLen) + 6rdPrefixLen MUST be less than or equal to 128. */
+        prefixlen = option[1];
+        if (32 - ipv4masklen + prefixlen > 128)
+                return -EINVAL;
+
+        /* 6rdPrefix: The service provider's 6rd IPv6 prefix represented as a 16-octet IPv6 address.
+         *            The bits in the prefix after the 6rdPrefixlen number of bits are reserved and
+         *            MUST be initialized to zero by the sender and ignored by the receiver. */
+        memcpy(&prefix, option + 2, sizeof(struct in6_addr));
+        (void) in6_addr_mask(&prefix, prefixlen);
+
+        /* 6rdBRIPv4Address: One or more IPv4 addresses of the 6rd Border Relays for a given 6rd domain. */
+        n_br_addresses = (len - 2 - sizeof(struct in6_addr)) / sizeof(struct in_addr);
+        br_addresses = newdup(struct in_addr, option + 2 + sizeof(struct in6_addr), n_br_addresses);
+        if (!br_addresses)
+                return -ENOMEM;
+
+        lease->sixrd_ipv4masklen = ipv4masklen;
+        lease->sixrd_prefixlen = prefixlen;
+        lease->sixrd_prefix = prefix;
+        lease->sixrd_br_addresses = TAKE_PTR(br_addresses);
+        lease->sixrd_n_br_addresses = n_br_addresses;
+
+        return 0;
+}
+
+int dhcp_lease_parse_options(uint8_t code, uint8_t len, const void *option, void *userdata) {
+        sd_dhcp_lease *lease = ASSERT_PTR(userdata);
+        int r;
+
+        switch (code) {
+
+        case SD_DHCP_OPTION_IP_ADDRESS_LEASE_TIME:
+                r = lease_parse_u32(option, len, &lease->lifetime, 1);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse lease time, ignoring: %m");
+
+                break;
+
+        case SD_DHCP_OPTION_SERVER_IDENTIFIER:
+                r = lease_parse_be32(option, len, &lease->server_address);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse server identifier, ignoring: %m");
+
+                break;
+
+        case SD_DHCP_OPTION_SUBNET_MASK:
+                r = lease_parse_be32(option, len, &lease->subnet_mask);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse subnet mask, ignoring: %m");
+                else
+                        lease->have_subnet_mask = true;
+                break;
+
+        case SD_DHCP_OPTION_BROADCAST:
+                r = lease_parse_be32(option, len, &lease->broadcast);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse broadcast address, ignoring: %m");
+                else
+                        lease->have_broadcast = true;
+                break;
+
+        case SD_DHCP_OPTION_ROUTER:
+                r = lease_parse_in_addrs(option, len, &lease->router, &lease->router_size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse router addresses, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_DOMAIN_NAME_SERVER:
+                r = lease_parse_in_addrs(option, len, &lease->servers[SD_DHCP_LEASE_DNS].addr, &lease->servers[SD_DHCP_LEASE_DNS].size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse DNS server, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_NTP_SERVER:
+                r = lease_parse_in_addrs(option, len, &lease->servers[SD_DHCP_LEASE_NTP].addr, &lease->servers[SD_DHCP_LEASE_NTP].size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse NTP server, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_SIP_SERVER:
+                r = lease_parse_sip_server(option, len, &lease->servers[SD_DHCP_LEASE_SIP].addr, &lease->servers[SD_DHCP_LEASE_SIP].size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse SIP server, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_POP3_SERVER:
+                r = lease_parse_in_addrs(option, len, &lease->servers[SD_DHCP_LEASE_POP3].addr, &lease->servers[SD_DHCP_LEASE_POP3].size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse POP3 server, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_SMTP_SERVER:
+                r = lease_parse_in_addrs(option, len, &lease->servers[SD_DHCP_LEASE_SMTP].addr, &lease->servers[SD_DHCP_LEASE_SMTP].size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse SMTP server, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_LPR_SERVER:
+                r = lease_parse_in_addrs(option, len, &lease->servers[SD_DHCP_LEASE_LPR].addr, &lease->servers[SD_DHCP_LEASE_LPR].size);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse LPR server, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_STATIC_ROUTE:
+                r = lease_parse_static_routes(lease, option, len);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse static routes, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_MTU_INTERFACE:
+                r = lease_parse_u16(option, len, &lease->mtu, 68);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse MTU, ignoring: %m");
+                if (lease->mtu < DHCP_MIN_PACKET_SIZE) {
+                        log_debug("MTU value of %" PRIu16 " too small. Using default MTU value of %d instead.", lease->mtu, DHCP_MIN_PACKET_SIZE);
+                        lease->mtu = DHCP_MIN_PACKET_SIZE;
+                }
+
+                break;
+
+        case SD_DHCP_OPTION_DOMAIN_NAME:
+                r = lease_parse_domain(option, len, &lease->domainname);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to parse domain name, ignoring: %m");
+                        return 0;
+                }
+
+                break;
+
+        case SD_DHCP_OPTION_DOMAIN_SEARCH:
+                r = dhcp_lease_parse_search_domains(option, len, &lease->search_domains);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse Domain Search List, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_HOST_NAME:
+                r = lease_parse_domain(option, len, &lease->hostname);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to parse hostname, ignoring: %m");
+                        return 0;
+                }
+
+                break;
+
+        case SD_DHCP_OPTION_ROOT_PATH:
+                r = lease_parse_string(option, len, &lease->root_path);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse root path, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_RENEWAL_TIME:
+                r = lease_parse_u32(option, len, &lease->t1, 1);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse T1 time, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_REBINDING_TIME:
+                r = lease_parse_u32(option, len, &lease->t2, 1);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse T2 time, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_CLASSLESS_STATIC_ROUTE:
+                r = lease_parse_classless_routes(lease, option, len);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse classless routes, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_TZDB_TIMEZONE: {
+                _cleanup_free_ char *tz = NULL;
+
+                r = lease_parse_string(option, len, &tz);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to parse timezone option, ignoring: %m");
+                        return 0;
+                }
+
+                if (!timezone_is_valid(tz, LOG_DEBUG)) {
+                        log_debug("Timezone is not valid, ignoring.");
+                        return 0;
+                }
+
+                free_and_replace(lease->timezone, tz);
+
+                break;
+        }
+
+        case SD_DHCP_OPTION_VENDOR_SPECIFIC:
+
+                if (len <= 0)
+                        lease->vendor_specific = mfree(lease->vendor_specific);
+                else {
+                        void *p;
+
+                        p = memdup(option, len);
+                        if (!p)
+                                return -ENOMEM;
+
+                        free(lease->vendor_specific);
+                        lease->vendor_specific = p;
+                }
+
+                lease->vendor_specific_len = len;
+                break;
+
+        case SD_DHCP_OPTION_6RD:
+                r = lease_parse_6rd(lease, option, len);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse 6rd option, ignoring: %m");
+                break;
+
+        case SD_DHCP_OPTION_PRIVATE_BASE ... SD_DHCP_OPTION_PRIVATE_LAST:
+                r = dhcp_lease_insert_private_option(lease, code, option, len);
+                if (r < 0)
+                        return r;
+
+                break;
+
+        default:
+                log_debug("Ignoring DHCP option %"PRIu8" while parsing.", code);
+                break;
+        }
+
+        return 0;
+}
+
+/* Parses compressed domain names. */
+int dhcp_lease_parse_search_domains(const uint8_t *option, size_t len, char ***domains) {
+        _cleanup_strv_free_ char **names = NULL;
+        size_t pos = 0, cnt = 0;
+        int r;
+
+        assert(domains);
+        assert(option || len == 0);
+
+        if (len == 0)
+                return -EBADMSG;
+
+        while (pos < len) {
+                _cleanup_free_ char *name = NULL;
+                size_t n = 0;
+                size_t jump_barrier = pos, next_chunk = 0;
+                bool first = true;
+
+                for (;;) {
+                        uint8_t c;
+                        c = option[pos++];
+
+                        if (c == 0) {
+                                /* End of name */
+                                break;
+                        } else if (c <= 63) {
+                                const char *label;
+
+                                /* Literal label */
+                                label = (const char*) (option + pos);
+                                pos += c;
+                                if (pos >= len)
+                                        return -EBADMSG;
+
+                                if (!GREEDY_REALLOC(name, n + !first + DNS_LABEL_ESCAPED_MAX))
+                                        return -ENOMEM;
+
+                                if (first)
+                                        first = false;
+                                else
+                                        name[n++] = '.';
+
+                                r = dns_label_escape(label, c, name + n, DNS_LABEL_ESCAPED_MAX);
+                                if (r < 0)
+                                        return r;
+
+                                n += r;
+                        } else if (FLAGS_SET(c, 0xc0)) {
+                                /* Pointer */
+
+                                uint8_t d;
+                                uint16_t ptr;
+
+                                if (pos >= len)
+                                        return -EBADMSG;
+
+                                d = option[pos++];
+                                ptr = (uint16_t) (c & ~0xc0) << 8 | (uint16_t) d;
+
+                                /* Jumps are limited to a "prior occurrence" (RFC-1035 4.1.4) */
+                                if (ptr >= jump_barrier)
+                                        return -EBADMSG;
+                                jump_barrier = ptr;
+
+                                /* Save current location so we don't end up re-parsing what's parsed so far. */
+                                if (next_chunk == 0)
+                                        next_chunk = pos;
+
+                                pos = ptr;
+                        } else
+                                return -EBADMSG;
+                }
+
+                if (!GREEDY_REALLOC(name, n + 1))
+                        return -ENOMEM;
+                name[n] = 0;
+
+                r = strv_extend(&names, name);
+                if (r < 0)
+                        return r;
+
+                cnt++;
+
+                if (next_chunk != 0)
+                      pos = next_chunk;
+        }
+
+        strv_free_and_replace(*domains, names);
+
+        return cnt;
+}
+
+int dhcp_lease_insert_private_option(sd_dhcp_lease *lease, uint8_t tag, const void *data, uint8_t len) {
+        struct sd_dhcp_raw_option *option, *before = NULL;
+
+        assert(lease);
+
+        LIST_FOREACH(options, cur, lease->private_options) {
+                if (tag < cur->tag) {
+                        before = cur;
+                        break;
+                }
+                if (tag == cur->tag) {
+                        log_debug("Ignoring duplicate option, tagged %i.", tag);
+                        return 0;
+                }
+        }
+
+        option = new(struct sd_dhcp_raw_option, 1);
+        if (!option)
+                return -ENOMEM;
+
+        option->tag = tag;
+        option->length = len;
+        option->data = memdup(data, len);
+        if (!option->data) {
+                free(option);
+                return -ENOMEM;
+        }
+
+        LIST_INSERT_BEFORE(options, lease->private_options, before, option);
+        return 0;
+}
+
+int dhcp_lease_new(sd_dhcp_lease **ret) {
+        sd_dhcp_lease *lease;
+
+        lease = new0(sd_dhcp_lease, 1);
+        if (!lease)
+                return -ENOMEM;
+
+        lease->n_ref = 1;
+
+        *ret = lease;
+        return 0;
+}
+
+int dhcp_lease_save(sd_dhcp_lease *lease, const char *lease_file) {
+        _cleanup_(unlink_and_freep) char *temp_path = NULL;
+        _cleanup_fclose_ FILE *f = NULL;
+        struct in_addr address;
+        const struct in_addr *addresses;
+        const void *client_id, *data;
+        size_t client_id_len, data_len;
+        const char *string;
+        uint16_t mtu;
+        _cleanup_free_ sd_dhcp_route **routes = NULL;
+        char **search_domains;
+        uint32_t t1, t2, lifetime;
+        int r;
+
+        assert(lease);
+        assert(lease_file);
+
+        r = fopen_temporary(lease_file, &f, &temp_path);
+        if (r < 0)
+                return r;
+
+        (void) fchmod(fileno(f), 0644);
+
+        fprintf(f,
+                "# This is private data. Do not parse.\n");
+
+        r = sd_dhcp_lease_get_address(lease, &address);
+        if (r >= 0)
+                fprintf(f, "ADDRESS=%s\n", IN4_ADDR_TO_STRING(&address));
+
+        r = sd_dhcp_lease_get_netmask(lease, &address);
+        if (r >= 0)
+                fprintf(f, "NETMASK=%s\n", IN4_ADDR_TO_STRING(&address));
+
+        r = sd_dhcp_lease_get_router(lease, &addresses);
+        if (r > 0) {
+                fputs("ROUTER=", f);
+                serialize_in_addrs(f, addresses, r, NULL, NULL);
+                fputc('\n', f);
+        }
+
+        r = sd_dhcp_lease_get_server_identifier(lease, &address);
+        if (r >= 0)
+                fprintf(f, "SERVER_ADDRESS=%s\n", IN4_ADDR_TO_STRING(&address));
+
+        r = sd_dhcp_lease_get_next_server(lease, &address);
+        if (r >= 0)
+                fprintf(f, "NEXT_SERVER=%s\n", IN4_ADDR_TO_STRING(&address));
+
+        r = sd_dhcp_lease_get_broadcast(lease, &address);
+        if (r >= 0)
+                fprintf(f, "BROADCAST=%s\n", IN4_ADDR_TO_STRING(&address));
+
+        r = sd_dhcp_lease_get_mtu(lease, &mtu);
+        if (r >= 0)
+                fprintf(f, "MTU=%" PRIu16 "\n", mtu);
+
+        r = sd_dhcp_lease_get_t1(lease, &t1);
+        if (r >= 0)
+                fprintf(f, "T1=%" PRIu32 "\n", t1);
+
+        r = sd_dhcp_lease_get_t2(lease, &t2);
+        if (r >= 0)
+                fprintf(f, "T2=%" PRIu32 "\n", t2);
+
+        r = sd_dhcp_lease_get_lifetime(lease, &lifetime);
+        if (r >= 0)
+                fprintf(f, "LIFETIME=%" PRIu32 "\n", lifetime);
+
+        r = sd_dhcp_lease_get_dns(lease, &addresses);
+        if (r > 0) {
+                fputs("DNS=", f);
+                serialize_in_addrs(f, addresses, r, NULL, NULL);
+                fputc('\n', f);
+        }
+
+        r = sd_dhcp_lease_get_ntp(lease, &addresses);
+        if (r > 0) {
+                fputs("NTP=", f);
+                serialize_in_addrs(f, addresses, r, NULL, NULL);
+                fputc('\n', f);
+        }
+
+        r = sd_dhcp_lease_get_sip(lease, &addresses);
+        if (r > 0) {
+                fputs("SIP=", f);
+                serialize_in_addrs(f, addresses, r, NULL, NULL);
+                fputc('\n', f);
+        }
+
+        r = sd_dhcp_lease_get_domainname(lease, &string);
+        if (r >= 0)
+                fprintf(f, "DOMAINNAME=%s\n", string);
+
+        r = sd_dhcp_lease_get_search_domains(lease, &search_domains);
+        if (r > 0) {
+                fputs("DOMAIN_SEARCH_LIST=", f);
+                fputstrv(f, search_domains, NULL, NULL);
+                fputc('\n', f);
+        }
+
+        r = sd_dhcp_lease_get_hostname(lease, &string);
+        if (r >= 0)
+                fprintf(f, "HOSTNAME=%s\n", string);
+
+        r = sd_dhcp_lease_get_root_path(lease, &string);
+        if (r >= 0)
+                fprintf(f, "ROOT_PATH=%s\n", string);
+
+        r = sd_dhcp_lease_get_static_routes(lease, &routes);
+        if (r > 0)
+                serialize_dhcp_routes(f, "STATIC_ROUTES", routes, r);
+
+        routes = mfree(routes);
+        r = sd_dhcp_lease_get_classless_routes(lease, &routes);
+        if (r > 0)
+                serialize_dhcp_routes(f, "CLASSLESS_ROUTES", routes, r);
+
+        r = sd_dhcp_lease_get_timezone(lease, &string);
+        if (r >= 0)
+                fprintf(f, "TIMEZONE=%s\n", string);
+
+        r = sd_dhcp_lease_get_client_id(lease, &client_id, &client_id_len);
+        if (r >= 0) {
+                _cleanup_free_ char *client_id_hex = NULL;
+
+                client_id_hex = hexmem(client_id, client_id_len);
+                if (!client_id_hex)
+                        return -ENOMEM;
+                fprintf(f, "CLIENTID=%s\n", client_id_hex);
+        }
+
+        r = sd_dhcp_lease_get_vendor_specific(lease, &data, &data_len);
+        if (r >= 0) {
+                _cleanup_free_ char *option_hex = NULL;
+
+                option_hex = hexmem(data, data_len);
+                if (!option_hex)
+                        return -ENOMEM;
+                fprintf(f, "VENDOR_SPECIFIC=%s\n", option_hex);
+        }
+
+        LIST_FOREACH(options, option, lease->private_options) {
+                char key[STRLEN("OPTION_000")+1];
+
+                xsprintf(key, "OPTION_%" PRIu8, option->tag);
+                r = serialize_dhcp_option(f, key, option->data, option->length);
+                if (r < 0)
+                        return r;
+        }
+
+        r = fflush_and_check(f);
+        if (r < 0)
+                return r;
+
+        r = conservative_rename(temp_path, lease_file);
+        if (r < 0)
+                return r;
+
+        temp_path = mfree(temp_path);
+
+        return 0;
+}
+
+static char **private_options_free(char **options) {
+        if (!options)
+                return NULL;
+
+        for (unsigned i = 0; i < SD_DHCP_OPTION_PRIVATE_LAST - SD_DHCP_OPTION_PRIVATE_BASE + 1; i++)
+                free(options[i]);
+
+        return mfree(options);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(char**, private_options_free);
+
+int dhcp_lease_load(sd_dhcp_lease **ret, const char *lease_file) {
+        _cleanup_(sd_dhcp_lease_unrefp) sd_dhcp_lease *lease = NULL;
+        _cleanup_free_ char
+                *address = NULL,
+                *router = NULL,
+                *netmask = NULL,
+                *server_address = NULL,
+                *next_server = NULL,
+                *broadcast = NULL,
+                *dns = NULL,
+                *ntp = NULL,
+                *sip = NULL,
+                *pop3 = NULL,
+                *smtp = NULL,
+                *lpr = NULL,
+                *mtu = NULL,
+                *static_routes = NULL,
+                *classless_routes = NULL,
+                *domains = NULL,
+                *client_id_hex = NULL,
+                *vendor_specific_hex = NULL,
+                *lifetime = NULL,
+                *t1 = NULL,
+                *t2 = NULL;
+        _cleanup_(private_options_freep) char **options = NULL;
+
+        int r, i;
+
+        assert(lease_file);
+        assert(ret);
+
+        r = dhcp_lease_new(&lease);
+        if (r < 0)
+                return r;
+
+        options = new0(char*, SD_DHCP_OPTION_PRIVATE_LAST - SD_DHCP_OPTION_PRIVATE_BASE + 1);
+        if (!options)
+                return -ENOMEM;
+
+        r = parse_env_file(NULL, lease_file,
+                           "ADDRESS", &address,
+                           "ROUTER", &router,
+                           "NETMASK", &netmask,
+                           "SERVER_ADDRESS", &server_address,
+                           "NEXT_SERVER", &next_server,
+                           "BROADCAST", &broadcast,
+                           "DNS", &dns,
+                           "NTP", &ntp,
+                           "SIP", &sip,
+                           "POP3", &pop3,
+                           "SMTP", &smtp,
+                           "LPR", &lpr,
+                           "MTU", &mtu,
+                           "DOMAINNAME", &lease->domainname,
+                           "HOSTNAME", &lease->hostname,
+                           "DOMAIN_SEARCH_LIST", &domains,
+                           "ROOT_PATH", &lease->root_path,
+                           "STATIC_ROUTES", &static_routes,
+                           "CLASSLESS_ROUTES", &classless_routes,
+                           "CLIENTID", &client_id_hex,
+                           "TIMEZONE", &lease->timezone,
+                           "VENDOR_SPECIFIC", &vendor_specific_hex,
+                           "LIFETIME", &lifetime,
+                           "T1", &t1,
+                           "T2", &t2,
+                           "OPTION_224", &options[0],
+                           "OPTION_225", &options[1],
+                           "OPTION_226", &options[2],
+                           "OPTION_227", &options[3],
+                           "OPTION_228", &options[4],
+                           "OPTION_229", &options[5],
+                           "OPTION_230", &options[6],
+                           "OPTION_231", &options[7],
+                           "OPTION_232", &options[8],
+                           "OPTION_233", &options[9],
+                           "OPTION_234", &options[10],
+                           "OPTION_235", &options[11],
+                           "OPTION_236", &options[12],
+                           "OPTION_237", &options[13],
+                           "OPTION_238", &options[14],
+                           "OPTION_239", &options[15],
+                           "OPTION_240", &options[16],
+                           "OPTION_241", &options[17],
+                           "OPTION_242", &options[18],
+                           "OPTION_243", &options[19],
+                           "OPTION_244", &options[20],
+                           "OPTION_245", &options[21],
+                           "OPTION_246", &options[22],
+                           "OPTION_247", &options[23],
+                           "OPTION_248", &options[24],
+                           "OPTION_249", &options[25],
+                           "OPTION_250", &options[26],
+                           "OPTION_251", &options[27],
+                           "OPTION_252", &options[28],
+                           "OPTION_253", &options[29],
+                           "OPTION_254", &options[30]);
+        if (r < 0)
+                return r;
+
+        if (address) {
+                r = inet_pton(AF_INET, address, &lease->address);
+                if (r <= 0)
+                        log_debug("Failed to parse address %s, ignoring.", address);
+        }
+
+        if (router) {
+                r = deserialize_in_addrs(&lease->router, router);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize router addresses %s, ignoring: %m", router);
+                else
+                        lease->router_size = r;
+        }
+
+        if (netmask) {
+                r = inet_pton(AF_INET, netmask, &lease->subnet_mask);
+                if (r <= 0)
+                        log_debug("Failed to parse netmask %s, ignoring.", netmask);
+                else
+                        lease->have_subnet_mask = true;
+        }
+
+        if (server_address) {
+                r = inet_pton(AF_INET, server_address, &lease->server_address);
+                if (r <= 0)
+                        log_debug("Failed to parse server address %s, ignoring.", server_address);
+        }
+
+        if (next_server) {
+                r = inet_pton(AF_INET, next_server, &lease->next_server);
+                if (r <= 0)
+                        log_debug("Failed to parse next server %s, ignoring.", next_server);
+        }
+
+        if (broadcast) {
+                r = inet_pton(AF_INET, broadcast, &lease->broadcast);
+                if (r <= 0)
+                        log_debug("Failed to parse broadcast address %s, ignoring.", broadcast);
+                else
+                        lease->have_broadcast = true;
+        }
+
+        if (dns) {
+                r = deserialize_in_addrs(&lease->servers[SD_DHCP_LEASE_DNS].addr, dns);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize DNS servers %s, ignoring: %m", dns);
+                else
+                        lease->servers[SD_DHCP_LEASE_DNS].size = r;
+        }
+
+        if (ntp) {
+                r = deserialize_in_addrs(&lease->servers[SD_DHCP_LEASE_NTP].addr, ntp);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize NTP servers %s, ignoring: %m", ntp);
+                else
+                        lease->servers[SD_DHCP_LEASE_NTP].size = r;
+        }
+
+        if (sip) {
+                r = deserialize_in_addrs(&lease->servers[SD_DHCP_LEASE_SIP].addr, sip);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize SIP servers %s, ignoring: %m", sip);
+                else
+                        lease->servers[SD_DHCP_LEASE_SIP].size = r;
+        }
+
+        if (pop3) {
+                r = deserialize_in_addrs(&lease->servers[SD_DHCP_LEASE_POP3].addr, pop3);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize POP3 server %s, ignoring: %m", pop3);
+                else
+                        lease->servers[SD_DHCP_LEASE_POP3].size = r;
+        }
+
+        if (smtp) {
+                r = deserialize_in_addrs(&lease->servers[SD_DHCP_LEASE_SMTP].addr, smtp);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize SMTP server %s, ignoring: %m", smtp);
+                else
+                        lease->servers[SD_DHCP_LEASE_SMTP].size = r;
+        }
+
+        if (lpr) {
+                r = deserialize_in_addrs(&lease->servers[SD_DHCP_LEASE_LPR].addr, lpr);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to deserialize LPR server %s, ignoring: %m", lpr);
+                else
+                        lease->servers[SD_DHCP_LEASE_LPR].size = r;
+        }
+
+        if (mtu) {
+                r = safe_atou16(mtu, &lease->mtu);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse MTU %s, ignoring: %m", mtu);
+        }
+
+        if (domains) {
+                _cleanup_strv_free_ char **a = NULL;
+                a = strv_split(domains, " ");
+                if (!a)
+                        return -ENOMEM;
+
+                if (!strv_isempty(a))
+                        lease->search_domains = TAKE_PTR(a);
+        }
+
+        if (static_routes) {
+                r = deserialize_dhcp_routes(
+                                &lease->static_routes,
+                                &lease->n_static_routes,
+                                static_routes);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse DHCP static routes %s, ignoring: %m", static_routes);
+        }
+
+        if (classless_routes) {
+                r = deserialize_dhcp_routes(
+                                &lease->classless_routes,
+                                &lease->n_classless_routes,
+                                classless_routes);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse DHCP classless routes %s, ignoring: %m", classless_routes);
+        }
+
+        if (lifetime) {
+                r = safe_atou32(lifetime, &lease->lifetime);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse lifetime %s, ignoring: %m", lifetime);
+        }
+
+        if (t1) {
+                r = safe_atou32(t1, &lease->t1);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse T1 %s, ignoring: %m", t1);
+        }
+
+        if (t2) {
+                r = safe_atou32(t2, &lease->t2);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse T2 %s, ignoring: %m", t2);
+        }
+
+        if (client_id_hex) {
+                r = unhexmem(client_id_hex, SIZE_MAX, &lease->client_id, &lease->client_id_len);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse client ID %s, ignoring: %m", client_id_hex);
+        }
+
+        if (vendor_specific_hex) {
+                r = unhexmem(vendor_specific_hex, SIZE_MAX, &lease->vendor_specific, &lease->vendor_specific_len);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse vendor specific data %s, ignoring: %m", vendor_specific_hex);
+        }
+
+        for (i = 0; i <= SD_DHCP_OPTION_PRIVATE_LAST - SD_DHCP_OPTION_PRIVATE_BASE; i++) {
+                _cleanup_free_ void *data = NULL;
+                size_t len;
+
+                if (!options[i])
+                        continue;
+
+                r = unhexmem(options[i], SIZE_MAX, &data, &len);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to parse private DHCP option %s, ignoring: %m", options[i]);
+                        continue;
+                }
+
+                r = dhcp_lease_insert_private_option(lease, SD_DHCP_OPTION_PRIVATE_BASE + i, data, len);
+                if (r < 0)
+                        return r;
+        }
+
+        *ret = TAKE_PTR(lease);
+
+        return 0;
+}
+
+int dhcp_lease_set_default_subnet_mask(sd_dhcp_lease *lease) {
+        struct in_addr address, mask;
+        int r;
+
+        assert(lease);
+
+        if (lease->address == 0)
+                return -ENODATA;
+
+        address.s_addr = lease->address;
+
+        /* fall back to the default subnet masks based on address class */
+        r = in4_addr_default_subnet_mask(&address, &mask);
+        if (r < 0)
+                return r;
+
+        lease->subnet_mask = mask.s_addr;
+        lease->have_subnet_mask = true;
+
+        return 0;
+}
+
+int sd_dhcp_lease_get_client_id(sd_dhcp_lease *lease, const void **client_id, size_t *client_id_len) {
+        assert_return(lease, -EINVAL);
+        assert_return(client_id, -EINVAL);
+        assert_return(client_id_len, -EINVAL);
+
+        if (!lease->client_id)
+                return -ENODATA;
+
+        *client_id = lease->client_id;
+        *client_id_len = lease->client_id_len;
+
+        return 0;
+}
+
+int dhcp_lease_set_client_id(sd_dhcp_lease *lease, const void *client_id, size_t client_id_len) {
+        assert_return(lease, -EINVAL);
+        assert_return(client_id || client_id_len <= 0, -EINVAL);
+
+        if (client_id_len <= 0)
+                lease->client_id = mfree(lease->client_id);
+        else {
+                void *p;
+
+                p = memdup(client_id, client_id_len);
+                if (!p)
+                        return -ENOMEM;
+
+                free(lease->client_id);
+                lease->client_id = p;
+                lease->client_id_len = client_id_len;
+        }
+
+        return 0;
+}
+
+int sd_dhcp_lease_get_timezone(sd_dhcp_lease *lease, const char **tz) {
+        assert_return(lease, -EINVAL);
+        assert_return(tz, -EINVAL);
+
+        if (!lease->timezone)
+                return -ENODATA;
+
+        *tz = lease->timezone;
+        return 0;
+}
+
+int sd_dhcp_route_get_destination(sd_dhcp_route *route, struct in_addr *destination) {
+        assert_return(route, -EINVAL);
+        assert_return(destination, -EINVAL);
+
+        *destination = route->dst_addr;
+        return 0;
+}
+
+int sd_dhcp_route_get_destination_prefix_length(sd_dhcp_route *route, uint8_t *length) {
+        assert_return(route, -EINVAL);
+        assert_return(length, -EINVAL);
+
+        *length = route->dst_prefixlen;
+        return 0;
+}
+
+int sd_dhcp_route_get_gateway(sd_dhcp_route *route, struct in_addr *gateway) {
+        assert_return(route, -EINVAL);
+        assert_return(gateway, -EINVAL);
+
+        *gateway = route->gw_addr;
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
new file mode 100644
index 0000000..ae509c8
--- /dev/null
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -0,0 +1,1672 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <net/if_arp.h>
+#include <sys/ioctl.h>
+
+#include "sd-dhcp-server.h"
+#include "sd-id128.h"
+
+#include "alloc-util.h"
+#include "dhcp-internal.h"
+#include "dhcp-server-internal.h"
+#include "dns-domain.h"
+#include "fd-util.h"
+#include "in-addr-util.h"
+#include "io-util.h"
+#include "memory-util.h"
+#include "network-common.h"
+#include "ordered-set.h"
+#include "siphash24.h"
+#include "string-util.h"
+#include "unaligned.h"
+#include "utf8.h"
+
+#define DHCP_DEFAULT_LEASE_TIME_USEC USEC_PER_HOUR
+#define DHCP_MAX_LEASE_TIME_USEC (USEC_PER_HOUR*12)
+
+DHCPLease *dhcp_lease_free(DHCPLease *lease) {
+        if (!lease)
+                return NULL;
+
+        if (lease->server) {
+                hashmap_remove_value(lease->server->bound_leases_by_address, UINT32_TO_PTR(lease->address), lease);
+                hashmap_remove_value(lease->server->bound_leases_by_client_id, &lease->client_id, lease);
+                hashmap_remove_value(lease->server->static_leases_by_address, UINT32_TO_PTR(lease->address), lease);
+                hashmap_remove_value(lease->server->static_leases_by_client_id, &lease->client_id, lease);
+        }
+
+        free(lease->client_id.data);
+        return mfree(lease);
+}
+
+/* configures the server's address and subnet, and optionally the pool's size and offset into the subnet
+ * the whole pool must fit into the subnet, and may not contain the first (any) nor last (broadcast) address
+ * moreover, the server's own address may be in the pool, and is in that case reserved in order not to
+ * accidentally hand it out */
+int sd_dhcp_server_configure_pool(
+                sd_dhcp_server *server,
+                const struct in_addr *address,
+                unsigned char prefixlen,
+                uint32_t offset,
+                uint32_t size) {
+
+        struct in_addr netmask_addr;
+        be32_t netmask;
+        uint32_t server_off, broadcast_off, size_max;
+
+        assert_return(server, -EINVAL);
+        assert_return(address, -EINVAL);
+        assert_return(address->s_addr != INADDR_ANY, -EINVAL);
+        assert_return(prefixlen <= 32, -ERANGE);
+
+        assert_se(in4_addr_prefixlen_to_netmask(&netmask_addr, prefixlen));
+        netmask = netmask_addr.s_addr;
+
+        server_off = be32toh(address->s_addr & ~netmask);
+        broadcast_off = be32toh(~netmask);
+
+        /* the server address cannot be the subnet address */
+        assert_return(server_off != 0, -ERANGE);
+
+        /* nor the broadcast address */
+        assert_return(server_off != broadcast_off, -ERANGE);
+
+        /* 0 offset means we should set a default, we skip the first (subnet) address
+           and take the next one */
+        if (offset == 0)
+                offset = 1;
+
+        size_max = (broadcast_off + 1) /* the number of addresses in the subnet */
+                   - offset /* exclude the addresses before the offset */
+                   - 1; /* exclude the last (broadcast) address */
+
+        /* The pool must contain at least one address */
+        assert_return(size_max >= 1, -ERANGE);
+
+        if (size != 0)
+                assert_return(size <= size_max, -ERANGE);
+        else
+                size = size_max;
+
+        if (server->address != address->s_addr || server->netmask != netmask || server->pool_size != size || server->pool_offset != offset) {
+
+                server->pool_offset = offset;
+                server->pool_size = size;
+
+                server->address = address->s_addr;
+                server->netmask = netmask;
+                server->subnet = address->s_addr & netmask;
+
+                /* Drop any leases associated with the old address range */
+                hashmap_clear(server->bound_leases_by_address);
+                hashmap_clear(server->bound_leases_by_client_id);
+
+                if (server->callback)
+                        server->callback(server, SD_DHCP_SERVER_EVENT_LEASE_CHANGED, server->callback_userdata);
+        }
+
+        return 0;
+}
+
+int sd_dhcp_server_is_running(sd_dhcp_server *server) {
+        if (!server)
+                return false;
+
+        return !!server->receive_message;
+}
+
+int sd_dhcp_server_is_in_relay_mode(sd_dhcp_server *server) {
+        assert_return(server, -EINVAL);
+
+        return in4_addr_is_set(&server->relay_target);
+}
+
+void client_id_hash_func(const DHCPClientId *id, struct siphash *state) {
+        assert(id);
+        assert(id->length > 0);
+        assert(id->data);
+
+        siphash24_compress(&id->length, sizeof(id->length), state);
+        siphash24_compress(id->data, id->length, state);
+}
+
+int client_id_compare_func(const DHCPClientId *a, const DHCPClientId *b) {
+        int r;
+
+        assert(a->length > 0);
+        assert(a->data);
+        assert(b->length > 0);
+        assert(b->data);
+
+        r = CMP(a->length, b->length);
+        if (r != 0)
+                return r;
+
+        return memcmp(a->data, b->data, a->length);
+}
+
+DEFINE_HASH_OPS_WITH_VALUE_DESTRUCTOR(
+        dhcp_lease_hash_ops,
+        DHCPClientId,
+        client_id_hash_func,
+        client_id_compare_func,
+        DHCPLease,
+        dhcp_lease_free);
+
+static sd_dhcp_server *dhcp_server_free(sd_dhcp_server *server) {
+        assert(server);
+
+        sd_dhcp_server_stop(server);
+
+        sd_event_unref(server->event);
+
+        free(server->boot_server_name);
+        free(server->boot_filename);
+        free(server->timezone);
+
+        for (sd_dhcp_lease_server_type_t i = 0; i < _SD_DHCP_LEASE_SERVER_TYPE_MAX; i++)
+                free(server->servers[i].addr);
+
+        server->bound_leases_by_address = hashmap_free(server->bound_leases_by_address);
+        server->bound_leases_by_client_id = hashmap_free(server->bound_leases_by_client_id);
+        server->static_leases_by_address = hashmap_free(server->static_leases_by_address);
+        server->static_leases_by_client_id = hashmap_free(server->static_leases_by_client_id);
+
+        ordered_set_free(server->extra_options);
+        ordered_set_free(server->vendor_options);
+
+        free(server->agent_circuit_id);
+        free(server->agent_remote_id);
+
+        free(server->ifname);
+        return mfree(server);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp_server, sd_dhcp_server, dhcp_server_free);
+
+int sd_dhcp_server_new(sd_dhcp_server **ret, int ifindex) {
+        _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL;
+
+        assert_return(ret, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+
+        server = new(sd_dhcp_server, 1);
+        if (!server)
+                return -ENOMEM;
+
+        *server = (sd_dhcp_server) {
+                .n_ref = 1,
+                .fd_raw = -1,
+                .fd = -1,
+                .fd_broadcast = -1,
+                .address = htobe32(INADDR_ANY),
+                .netmask = htobe32(INADDR_ANY),
+                .ifindex = ifindex,
+                .bind_to_interface = true,
+                .default_lease_time = DIV_ROUND_UP(DHCP_DEFAULT_LEASE_TIME_USEC, USEC_PER_SEC),
+                .max_lease_time = DIV_ROUND_UP(DHCP_MAX_LEASE_TIME_USEC, USEC_PER_SEC),
+        };
+
+        *ret = TAKE_PTR(server);
+
+        return 0;
+}
+
+int sd_dhcp_server_set_ifname(sd_dhcp_server *server, const char *ifname) {
+        assert_return(server, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&server->ifname, ifname);
+}
+
+int sd_dhcp_server_get_ifname(sd_dhcp_server *server, const char **ret) {
+        int r;
+
+        assert_return(server, -EINVAL);
+
+        r = get_ifname(server->ifindex, &server->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = server->ifname;
+
+        return 0;
+}
+
+int sd_dhcp_server_attach_event(sd_dhcp_server *server, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(server, -EINVAL);
+        assert_return(!server->event, -EBUSY);
+
+        if (event)
+                server->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&server->event);
+                if (r < 0)
+                        return r;
+        }
+
+        server->event_priority = priority;
+
+        return 0;
+}
+
+int sd_dhcp_server_detach_event(sd_dhcp_server *server) {
+        assert_return(server, -EINVAL);
+
+        server->event = sd_event_unref(server->event);
+
+        return 0;
+}
+
+sd_event *sd_dhcp_server_get_event(sd_dhcp_server *server) {
+        assert_return(server, NULL);
+
+        return server->event;
+}
+
+int sd_dhcp_server_set_boot_server_address(sd_dhcp_server *server, const struct in_addr *address) {
+        assert_return(server, -EINVAL);
+
+        if (address)
+                server->boot_server_address = *address;
+        else
+                server->boot_server_address = (struct in_addr) {};
+
+        return 0;
+}
+
+int sd_dhcp_server_set_boot_server_name(sd_dhcp_server *server, const char *name) {
+        int r;
+
+        assert_return(server, -EINVAL);
+
+        if (name) {
+                r = dns_name_is_valid(name);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return -EINVAL;
+        }
+
+        return free_and_strdup(&server->boot_server_name, name);
+}
+
+int sd_dhcp_server_set_boot_filename(sd_dhcp_server *server, const char *filename) {
+        assert_return(server, -EINVAL);
+
+        if (filename && (!string_is_safe(filename) || !ascii_is_valid(filename)))
+                return -EINVAL;
+
+        return free_and_strdup(&server->boot_filename, filename);
+}
+
+int sd_dhcp_server_stop(sd_dhcp_server *server) {
+        bool running;
+
+        if (!server)
+                return 0;
+
+        running = sd_dhcp_server_is_running(server);
+
+        server->receive_message = sd_event_source_disable_unref(server->receive_message);
+        server->receive_broadcast = sd_event_source_disable_unref(server->receive_broadcast);
+
+        server->fd_raw = safe_close(server->fd_raw);
+        server->fd = safe_close(server->fd);
+        server->fd_broadcast = safe_close(server->fd_broadcast);
+
+        if (running)
+                log_dhcp_server(server, "STOPPED");
+
+        return 0;
+}
+
+static int dhcp_server_send_unicast_raw(
+                sd_dhcp_server *server,
+                uint8_t hlen,
+                const uint8_t *chaddr,
+                DHCPPacket *packet,
+                size_t len) {
+
+        union sockaddr_union link = {
+                .ll.sll_family = AF_PACKET,
+                .ll.sll_protocol = htobe16(ETH_P_IP),
+                .ll.sll_ifindex = server->ifindex,
+                .ll.sll_halen = hlen,
+        };
+
+        assert(server);
+        assert(server->ifindex > 0);
+        assert(server->address != 0);
+        assert(hlen > 0);
+        assert(chaddr);
+        assert(packet);
+        assert(len > sizeof(DHCPPacket));
+
+        memcpy(link.ll.sll_addr, chaddr, hlen);
+
+        if (len > UINT16_MAX)
+                return -EOVERFLOW;
+
+        dhcp_packet_append_ip_headers(packet, server->address, DHCP_PORT_SERVER,
+                                      packet->dhcp.yiaddr,
+                                      DHCP_PORT_CLIENT, len, -1);
+
+        return dhcp_network_send_raw_socket(server->fd_raw, &link, packet, len);
+}
+
+static int dhcp_server_send_udp(sd_dhcp_server *server, be32_t destination,
+                                uint16_t destination_port,
+                                DHCPMessage *message, size_t len) {
+        union sockaddr_union dest = {
+                .in.sin_family = AF_INET,
+                .in.sin_port = htobe16(destination_port),
+                .in.sin_addr.s_addr = destination,
+        };
+        struct iovec iov = {
+                .iov_base = message,
+                .iov_len = len,
+        };
+        CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct in_pktinfo))) control = {};
+        struct msghdr msg = {
+                .msg_name = &dest,
+                .msg_namelen = sizeof(dest.in),
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+        };
+        struct cmsghdr *cmsg;
+        struct in_pktinfo *pktinfo;
+
+        assert(server);
+        assert(server->fd >= 0);
+        assert(message);
+        assert(len >= sizeof(DHCPMessage));
+
+        if (server->bind_to_interface) {
+                msg.msg_control = &control;
+                msg.msg_controllen = sizeof(control);
+
+                cmsg = CMSG_FIRSTHDR(&msg);
+                assert(cmsg);
+
+                cmsg->cmsg_level = IPPROTO_IP;
+                cmsg->cmsg_type = IP_PKTINFO;
+                cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
+
+                /* we attach source interface and address info to the message
+                   rather than binding the socket. This will be mostly useful
+                   when we gain support for arbitrary number of server addresses
+                 */
+                pktinfo = (struct in_pktinfo*) CMSG_DATA(cmsg);
+                assert(pktinfo);
+
+                pktinfo->ipi_ifindex = server->ifindex;
+                pktinfo->ipi_spec_dst.s_addr = server->address;
+        }
+
+        if (sendmsg(server->fd, &msg, 0) < 0)
+                return -errno;
+
+        return 0;
+}
+
+static bool requested_broadcast(DHCPMessage *message) {
+        assert(message);
+        return message->flags & htobe16(0x8000);
+}
+
+static int dhcp_server_send(
+                sd_dhcp_server *server,
+                uint8_t hlen,
+                const uint8_t *chaddr,
+                be32_t destination,
+                uint16_t destination_port,
+                DHCPPacket *packet,
+                size_t optoffset,
+                bool l2_broadcast) {
+
+        if (destination != INADDR_ANY)
+                return dhcp_server_send_udp(server, destination,
+                                            destination_port, &packet->dhcp,
+                                            sizeof(DHCPMessage) + optoffset);
+        else if (l2_broadcast)
+                return dhcp_server_send_udp(server, INADDR_BROADCAST,
+                                            destination_port, &packet->dhcp,
+                                            sizeof(DHCPMessage) + optoffset);
+        else
+                /* we cannot send UDP packet to specific MAC address when the
+                   address is not yet configured, so must fall back to raw
+                   packets */
+                return dhcp_server_send_unicast_raw(server, hlen, chaddr, packet,
+                                                    sizeof(DHCPPacket) + optoffset);
+}
+
+int dhcp_server_send_packet(sd_dhcp_server *server,
+                            DHCPRequest *req, DHCPPacket *packet,
+                            int type, size_t optoffset) {
+        be32_t destination = INADDR_ANY;
+        uint16_t destination_port = DHCP_PORT_CLIENT;
+        int r;
+
+        assert(server);
+        assert(req);
+        assert(req->max_optlen > 0);
+        assert(req->message);
+        assert(optoffset <= req->max_optlen);
+        assert(packet);
+
+        r = dhcp_option_append(&packet->dhcp, req->max_optlen, &optoffset, 0,
+                               SD_DHCP_OPTION_SERVER_IDENTIFIER,
+                               4, &server->address);
+        if (r < 0)
+                return r;
+
+        if (req->agent_info_option) {
+                size_t opt_full_length = *(req->agent_info_option + 1) + 2;
+                /* there must be space left for SD_DHCP_OPTION_END */
+                if (optoffset + opt_full_length < req->max_optlen) {
+                        memcpy(packet->dhcp.options + optoffset, req->agent_info_option, opt_full_length);
+                        optoffset += opt_full_length;
+                }
+        }
+
+        r = dhcp_option_append(&packet->dhcp, req->max_optlen, &optoffset, 0,
+                               SD_DHCP_OPTION_END, 0, NULL);
+        if (r < 0)
+                return r;
+
+        /* RFC 2131 Section 4.1
+
+           If the ’giaddr’ field in a DHCP message from a client is non-zero,
+           the server sends any return messages to the ’DHCP server’ port on the
+           BOOTP relay agent whose address appears in ’giaddr’. If the ’giaddr’
+           field is zero and the ’ciaddr’ field is nonzero, then the server
+           unicasts DHCPOFFER and DHCPACK messages to the address in ’ciaddr’.
+           If ’giaddr’ is zero and ’ciaddr’ is zero, and the broadcast bit is
+           set, then the server broadcasts DHCPOFFER and DHCPACK messages to
+           0xffffffff. If the broadcast bit is not set and ’giaddr’ is zero and
+           ’ciaddr’ is zero, then the server unicasts DHCPOFFER and DHCPACK
+           messages to the client’s hardware address and ’yiaddr’ address. In
+           all cases, when ’giaddr’ is zero, the server broadcasts any DHCPNAK
+           messages to 0xffffffff.
+
+           Section 4.3.2
+
+           If ’giaddr’ is set in the DHCPREQUEST message, the client is on a
+           different subnet. The server MUST set the broadcast bit in the
+           DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the
+           client, because the client may not have a correct network address
+           or subnet mask, and the client may not be answering ARP requests.
+         */
+        if (req->message->giaddr != 0) {
+                destination = req->message->giaddr;
+                destination_port = DHCP_PORT_SERVER;
+                if (type == DHCP_NAK)
+                        packet->dhcp.flags = htobe16(0x8000);
+        } else if (req->message->ciaddr != 0 && type != DHCP_NAK)
+                destination = req->message->ciaddr;
+
+        bool l2_broadcast = requested_broadcast(req->message) || type == DHCP_NAK;
+        return dhcp_server_send(server, req->message->hlen, req->message->chaddr,
+                                destination, destination_port, packet, optoffset, l2_broadcast);
+}
+
+static int server_message_init(
+                sd_dhcp_server *server,
+                DHCPPacket **ret,
+                uint8_t type,
+                size_t *ret_optoffset,
+                DHCPRequest *req) {
+
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        size_t optoffset = 0;
+        int r;
+
+        assert(server);
+        assert(ret);
+        assert(ret_optoffset);
+        assert(IN_SET(type, DHCP_OFFER, DHCP_ACK, DHCP_NAK));
+        assert(req);
+
+        packet = malloc0(sizeof(DHCPPacket) + req->max_optlen);
+        if (!packet)
+                return -ENOMEM;
+
+        r = dhcp_message_init(&packet->dhcp, BOOTREPLY,
+                              be32toh(req->message->xid), type,
+                              req->message->htype, req->message->hlen, req->message->chaddr,
+                              req->max_optlen, &optoffset);
+        if (r < 0)
+                return r;
+
+        packet->dhcp.flags = req->message->flags;
+        packet->dhcp.giaddr = req->message->giaddr;
+
+        *ret_optoffset = optoffset;
+        *ret = TAKE_PTR(packet);
+
+        return 0;
+}
+
+static int server_send_offer_or_ack(
+                sd_dhcp_server *server,
+                DHCPRequest *req,
+                be32_t address,
+                uint8_t type) {
+
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        sd_dhcp_option *j;
+        be32_t lease_time;
+        size_t offset;
+        int r;
+
+        assert(server);
+        assert(req);
+        assert(IN_SET(type, DHCP_OFFER, DHCP_ACK));
+
+        r = server_message_init(server, &packet, type, &offset, req);
+        if (r < 0)
+                return r;
+
+        packet->dhcp.yiaddr = address;
+        packet->dhcp.siaddr = server->boot_server_address.s_addr;
+
+        lease_time = htobe32(req->lifetime);
+        r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0,
+                               SD_DHCP_OPTION_IP_ADDRESS_LEASE_TIME, 4,
+                               &lease_time);
+        if (r < 0)
+                return r;
+
+        r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0,
+                               SD_DHCP_OPTION_SUBNET_MASK, 4, &server->netmask);
+        if (r < 0)
+                return r;
+
+        if (server->emit_router) {
+                r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0,
+                                       SD_DHCP_OPTION_ROUTER, 4,
+                                       in4_addr_is_set(&server->router_address) ?
+                                       &server->router_address.s_addr :
+                                       &server->address);
+                if (r < 0)
+                        return r;
+        }
+
+        if (server->boot_server_name) {
+                r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0,
+                                       SD_DHCP_OPTION_BOOT_SERVER_NAME,
+                                       strlen(server->boot_server_name), server->boot_server_name);
+                if (r < 0)
+                        return r;
+        }
+
+        if (server->boot_filename) {
+                r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0,
+                                       SD_DHCP_OPTION_BOOT_FILENAME,
+                                       strlen(server->boot_filename), server->boot_filename);
+                if (r < 0)
+                        return r;
+        }
+
+        if (type == DHCP_ACK) {
+                static const uint8_t option_map[_SD_DHCP_LEASE_SERVER_TYPE_MAX] = {
+                        [SD_DHCP_LEASE_DNS] = SD_DHCP_OPTION_DOMAIN_NAME_SERVER,
+                        [SD_DHCP_LEASE_NTP] = SD_DHCP_OPTION_NTP_SERVER,
+                        [SD_DHCP_LEASE_SIP] = SD_DHCP_OPTION_SIP_SERVER,
+                        [SD_DHCP_LEASE_POP3] = SD_DHCP_OPTION_POP3_SERVER,
+                        [SD_DHCP_LEASE_SMTP] = SD_DHCP_OPTION_SMTP_SERVER,
+                        [SD_DHCP_LEASE_LPR] = SD_DHCP_OPTION_LPR_SERVER,
+                };
+
+                for (sd_dhcp_lease_server_type_t k = 0; k < _SD_DHCP_LEASE_SERVER_TYPE_MAX; k++) {
+                        if (server->servers[k].size <= 0)
+                                continue;
+
+                        r = dhcp_option_append(
+                                        &packet->dhcp, req->max_optlen, &offset, 0,
+                                        option_map[k],
+                                        sizeof(struct in_addr) * server->servers[k].size,
+                                        server->servers[k].addr);
+                        if (r < 0)
+                                return r;
+                }
+
+
+                if (server->timezone) {
+                        r = dhcp_option_append(
+                                        &packet->dhcp, req->max_optlen, &offset, 0,
+                                        SD_DHCP_OPTION_TZDB_TIMEZONE,
+                                        strlen(server->timezone), server->timezone);
+                        if (r < 0)
+                                return r;
+                }
+        }
+
+        ORDERED_SET_FOREACH(j, server->extra_options) {
+                r = dhcp_option_append(&packet->dhcp, req->max_optlen, &offset, 0,
+                                       j->option, j->length, j->data);
+                if (r < 0)
+                        return r;
+        }
+
+        if (!ordered_set_isempty(server->vendor_options)) {
+                r = dhcp_option_append(
+                                &packet->dhcp, req->max_optlen, &offset, 0,
+                                SD_DHCP_OPTION_VENDOR_SPECIFIC,
+                                ordered_set_size(server->vendor_options), server->vendor_options);
+                if (r < 0)
+                        return r;
+        }
+
+        return dhcp_server_send_packet(server, req, packet, type, offset);
+}
+
+static int server_send_nak_or_ignore(sd_dhcp_server *server, bool init_reboot, DHCPRequest *req) {
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        size_t offset;
+        int r;
+
+        /* When a request is refused, RFC 2131, section 4.3.2 mentioned we should send NAK when the
+         * client is in INITREBOOT. If the client is in other state, there is nothing mentioned in the
+         * RFC whether we should send NAK or not. Hence, let's silently ignore the request. */
+
+        if (!init_reboot)
+                return 0;
+
+        r = server_message_init(server, &packet, DHCP_NAK, &offset, req);
+        if (r < 0)
+                return log_dhcp_server_errno(server, r, "Failed to create NAK message: %m");
+
+        r = dhcp_server_send_packet(server, req, packet, DHCP_NAK, offset);
+        if (r < 0)
+                return log_dhcp_server_errno(server, r, "Could not send NAK message: %m");
+
+        log_dhcp_server(server, "NAK (0x%x)", be32toh(req->message->xid));
+        return DHCP_NAK;
+}
+
+static int server_send_forcerenew(
+                sd_dhcp_server *server,
+                be32_t address,
+                be32_t gateway,
+                uint8_t htype,
+                uint8_t hlen,
+                const uint8_t *chaddr) {
+
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        size_t optoffset = 0;
+        int r;
+
+        assert(server);
+        assert(address != INADDR_ANY);
+        assert(chaddr);
+
+        packet = malloc0(sizeof(DHCPPacket) + DHCP_MIN_OPTIONS_SIZE);
+        if (!packet)
+                return -ENOMEM;
+
+        r = dhcp_message_init(&packet->dhcp, BOOTREPLY, 0,
+                              DHCP_FORCERENEW, htype, hlen, chaddr,
+                              DHCP_MIN_OPTIONS_SIZE, &optoffset);
+        if (r < 0)
+                return r;
+
+        r = dhcp_option_append(&packet->dhcp, DHCP_MIN_OPTIONS_SIZE,
+                               &optoffset, 0, SD_DHCP_OPTION_END, 0, NULL);
+        if (r < 0)
+                return r;
+
+        return dhcp_server_send_udp(server, address, DHCP_PORT_CLIENT,
+                                    &packet->dhcp,
+                                    sizeof(DHCPMessage) + optoffset);
+}
+
+static int parse_request(uint8_t code, uint8_t len, const void *option, void *userdata) {
+        DHCPRequest *req = ASSERT_PTR(userdata);
+
+        switch (code) {
+        case SD_DHCP_OPTION_IP_ADDRESS_LEASE_TIME:
+                if (len == 4)
+                        req->lifetime = unaligned_read_be32(option);
+
+                break;
+        case SD_DHCP_OPTION_REQUESTED_IP_ADDRESS:
+                if (len == 4)
+                        memcpy(&req->requested_ip, option, sizeof(be32_t));
+
+                break;
+        case SD_DHCP_OPTION_SERVER_IDENTIFIER:
+                if (len == 4)
+                        memcpy(&req->server_id, option, sizeof(be32_t));
+
+                break;
+        case SD_DHCP_OPTION_CLIENT_IDENTIFIER:
+                if (len >= 2) {
+                        uint8_t *data;
+
+                        data = memdup(option, len);
+                        if (!data)
+                                return -ENOMEM;
+
+                        free_and_replace(req->client_id.data, data);
+                        req->client_id.length = len;
+                }
+
+                break;
+        case SD_DHCP_OPTION_MAXIMUM_MESSAGE_SIZE:
+
+                if (len == 2 && unaligned_read_be16(option) >= sizeof(DHCPPacket))
+                        req->max_optlen = unaligned_read_be16(option) - sizeof(DHCPPacket);
+
+                break;
+        case SD_DHCP_OPTION_RELAY_AGENT_INFORMATION:
+                req->agent_info_option = (uint8_t*)option - 2;
+
+                break;
+        }
+
+        return 0;
+}
+
+static DHCPRequest* dhcp_request_free(DHCPRequest *req) {
+        if (!req)
+                return NULL;
+
+        free(req->client_id.data);
+        return mfree(req);
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(DHCPRequest*, dhcp_request_free);
+
+static int ensure_sane_request(sd_dhcp_server *server, DHCPRequest *req, DHCPMessage *message) {
+        assert(req);
+        assert(message);
+
+        req->message = message;
+
+        if (message->hlen > sizeof(message->chaddr))
+                return -EBADMSG;
+
+        /* set client id based on MAC address if client did not send an explicit one */
+        if (!req->client_id.data) {
+                uint8_t *data;
+
+                if (message->hlen == 0)
+                        return -EBADMSG;
+
+                data = new0(uint8_t, message->hlen + 1);
+                if (!data)
+                        return -ENOMEM;
+
+                data[0] = 0x01;
+                memcpy(data + 1, message->chaddr, message->hlen);
+
+                req->client_id.length = message->hlen + 1;
+                req->client_id.data = data;
+        }
+
+        if (message->hlen == 0 || memeqzero(message->chaddr, message->hlen)) {
+                /* See RFC2131 section 4.1.1.
+                 * hlen and chaddr may not be set for non-ethernet interface.
+                 * Let's try to retrieve it from the client ID. */
+
+                if (!req->client_id.data)
+                        return -EBADMSG;
+
+                if (req->client_id.length <= 1 || req->client_id.length > sizeof(message->chaddr) + 1)
+                        return -EBADMSG;
+
+                if (req->client_id.data[0] != 0x01)
+                        return -EBADMSG;
+
+                message->hlen = req->client_id.length - 1;
+                memcpy(message->chaddr, req->client_id.data + 1, message->hlen);
+        }
+
+        if (req->max_optlen < DHCP_MIN_OPTIONS_SIZE)
+                req->max_optlen = DHCP_MIN_OPTIONS_SIZE;
+
+        if (req->lifetime <= 0)
+                req->lifetime = MAX(1ULL, server->default_lease_time);
+
+        if (server->max_lease_time > 0 && req->lifetime > server->max_lease_time)
+                req->lifetime = server->max_lease_time;
+
+        return 0;
+}
+
+static bool address_is_in_pool(sd_dhcp_server *server, be32_t address) {
+        assert(server);
+
+        if (server->pool_size == 0)
+                return false;
+
+        if (address == server->address)
+                return false;
+
+        if (be32toh(address) < (be32toh(server->subnet) | server->pool_offset) ||
+            be32toh(address) >= (be32toh(server->subnet) | (server->pool_offset + server->pool_size)))
+                return false;
+
+        if (hashmap_contains(server->static_leases_by_address, UINT32_TO_PTR(address)))
+                return false;
+
+        return true;
+}
+
+static int append_agent_information_option(sd_dhcp_server *server, DHCPMessage *message, size_t opt_length, size_t size) {
+        int r;
+        size_t offset;
+
+        assert(server);
+        assert(message);
+
+        r = dhcp_option_find_option(message->options, opt_length, SD_DHCP_OPTION_END, &offset);
+        if (r < 0)
+                return r;
+
+        r = dhcp_option_append(message, size, &offset, 0, SD_DHCP_OPTION_RELAY_AGENT_INFORMATION, 0, server);
+        if (r < 0)
+                return r;
+
+        r = dhcp_option_append(message, size, &offset, 0, SD_DHCP_OPTION_END, 0, NULL);
+        if (r < 0)
+                return r;
+        return offset;
+}
+
+static int dhcp_server_relay_message(sd_dhcp_server *server, DHCPMessage *message, size_t opt_length, size_t buflen) {
+        _cleanup_free_ DHCPPacket *packet = NULL;
+        int r;
+
+        assert(server);
+        assert(message);
+        assert(sd_dhcp_server_is_in_relay_mode(server));
+
+        if (message->hlen == 0 || message->hlen > sizeof(message->chaddr) || memeqzero(message->chaddr, message->hlen))
+                return log_dhcp_server_errno(server, SYNTHETIC_ERRNO(EBADMSG),
+                                             "(relay agent) received message without/invalid hardware address, discarding.");
+
+        if (message->op == BOOTREQUEST) {
+                log_dhcp_server(server, "(relay agent) BOOTREQUEST (0x%x)", be32toh(message->xid));
+                if (message->hops >= 16)
+                        return -ETIME;
+                message->hops++;
+
+                /* https://tools.ietf.org/html/rfc1542#section-4.1.1 */
+                if (message->giaddr == 0)
+                        message->giaddr = server->address;
+
+                if (server->agent_circuit_id || server->agent_remote_id) {
+                        r = append_agent_information_option(server, message, opt_length, buflen - sizeof(DHCPMessage));
+                        if (r < 0)
+                                return log_dhcp_server_errno(server, r, "could not append relay option: %m");
+                        opt_length = r;
+                }
+
+                return dhcp_server_send_udp(server, server->relay_target.s_addr, DHCP_PORT_SERVER, message, sizeof(DHCPMessage) + opt_length);
+        } else if (message->op == BOOTREPLY) {
+                log_dhcp_server(server, "(relay agent) BOOTREPLY (0x%x)", be32toh(message->xid));
+                if (message->giaddr != server->address)
+                        return log_dhcp_server_errno(server, SYNTHETIC_ERRNO(EBADMSG),
+                                                     "(relay agent) BOOTREPLY giaddr mismatch, discarding");
+
+                int message_type = dhcp_option_parse(message, sizeof(DHCPMessage) + opt_length, NULL, NULL, NULL);
+                if (message_type < 0)
+                        return message_type;
+
+                packet = malloc0(sizeof(DHCPPacket) + opt_length);
+                if (!packet)
+                        return -ENOMEM;
+                memcpy(&packet->dhcp, message, sizeof(DHCPMessage) + opt_length);
+
+                r = dhcp_option_remove_option(packet->dhcp.options, opt_length, SD_DHCP_OPTION_RELAY_AGENT_INFORMATION);
+                if (r > 0)
+                        opt_length = r;
+
+                bool l2_broadcast = requested_broadcast(message) || message_type == DHCP_NAK;
+                const be32_t destination = message_type == DHCP_NAK ? INADDR_ANY : message->ciaddr;
+                return dhcp_server_send(server, message->hlen, message->chaddr, destination, DHCP_PORT_CLIENT, packet, opt_length, l2_broadcast);
+        }
+        return -EBADMSG;
+}
+
+static int prepare_new_lease(
+                DHCPLease **ret_lease,
+                be32_t address,
+                const DHCPClientId *client_id,
+                uint8_t htype,
+                uint8_t hlen,
+                const uint8_t *chaddr,
+                be32_t gateway,
+                usec_t expiration) {
+
+        _cleanup_(dhcp_lease_freep) DHCPLease *lease = NULL;
+
+        lease = new(DHCPLease, 1);
+        if (!lease)
+                return -ENOMEM;
+
+        *lease = (DHCPLease) {
+                .address = address,
+                .client_id.length = client_id->length,
+                .htype = htype,
+                .hlen = hlen,
+                .gateway = gateway,
+                .expiration = expiration,
+        };
+        lease->client_id.data = memdup(client_id->data, client_id->length);
+        if (!lease->client_id.data)
+                return -ENOMEM;
+
+        memcpy(lease->chaddr, chaddr, hlen);
+
+        *ret_lease = TAKE_PTR(lease);
+
+        return 0;
+}
+
+static int server_ack_request(sd_dhcp_server *server, DHCPRequest *req, DHCPLease *existing_lease, be32_t address) {
+        usec_t time_now, expiration;
+        int r;
+
+        assert(server);
+        assert(req);
+        assert(address != 0);
+
+        r = sd_event_now(server->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                return r;
+
+        expiration = usec_add(req->lifetime * USEC_PER_SEC, time_now);
+
+        if (existing_lease) {
+                assert(existing_lease->server);
+                assert(existing_lease->address == address);
+                existing_lease->expiration = expiration;
+
+        } else {
+                _cleanup_(dhcp_lease_freep) DHCPLease *lease = NULL;
+
+                r = prepare_new_lease(&lease, address, &req->client_id,
+                                      req->message->htype, req->message->hlen,
+                                      req->message->chaddr, req->message->giaddr, expiration);
+                if (r < 0)
+                        return log_dhcp_server_errno(server, r, "Failed to create new lease: %m");
+
+                lease->server = server; /* This must be set just before hashmap_put(). */
+
+                r = hashmap_ensure_put(&server->bound_leases_by_client_id, &dhcp_lease_hash_ops, &lease->client_id, lease);
+                if (r < 0)
+                        return log_dhcp_server_errno(server, r, "Could not save lease: %m");
+
+                r = hashmap_ensure_put(&server->bound_leases_by_address, NULL, UINT32_TO_PTR(lease->address), lease);
+                if (r < 0)
+                        return log_dhcp_server_errno(server, r, "Could not save lease: %m");
+
+                TAKE_PTR(lease);
+        }
+
+        r = server_send_offer_or_ack(server, req, address, DHCP_ACK);
+        if (r < 0)
+                return log_dhcp_server_errno(server, r, "Could not send ACK: %m");
+
+        log_dhcp_server(server, "ACK (0x%x)", be32toh(req->message->xid));
+
+        if (server->callback)
+                server->callback(server, SD_DHCP_SERVER_EVENT_LEASE_CHANGED, server->callback_userdata);
+
+        return DHCP_ACK;
+}
+
+static int dhcp_server_cleanup_expired_leases(sd_dhcp_server *server) {
+        DHCPLease *lease;
+        usec_t time_now;
+        int r;
+
+        assert(server);
+
+        r = sd_event_now(server->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                return r;
+
+        HASHMAP_FOREACH(lease, server->bound_leases_by_client_id)
+                if (lease->expiration < time_now) {
+                        log_dhcp_server(server, "CLEAN (0x%x)", be32toh(lease->address));
+                        dhcp_lease_free(lease);
+                }
+
+        return 0;
+}
+
+static bool address_available(sd_dhcp_server *server, be32_t address) {
+        assert(server);
+
+        if (hashmap_contains(server->bound_leases_by_address, UINT32_TO_PTR(address)) ||
+            hashmap_contains(server->static_leases_by_address, UINT32_TO_PTR(address)) ||
+            address == server->address)
+                return false;
+
+        return true;
+}
+
+#define HASH_KEY SD_ID128_MAKE(0d,1d,fe,bd,f1,24,bd,b3,47,f1,dd,6e,73,21,93,30)
+
+int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message, size_t length) {
+        _cleanup_(dhcp_request_freep) DHCPRequest *req = NULL;
+        _cleanup_free_ char *error_message = NULL;
+        DHCPLease *existing_lease, *static_lease;
+        int type, r;
+
+        assert(server);
+        assert(message);
+
+        if (message->op != BOOTREQUEST)
+                return 0;
+
+        req = new0(DHCPRequest, 1);
+        if (!req)
+                return -ENOMEM;
+
+        type = dhcp_option_parse(message, length, parse_request, req, &error_message);
+        if (type < 0)
+                return type;
+
+        r = ensure_sane_request(server, req, message);
+        if (r < 0)
+                return r;
+
+        r = dhcp_server_cleanup_expired_leases(server);
+        if (r < 0)
+                return r;
+
+        existing_lease = hashmap_get(server->bound_leases_by_client_id, &req->client_id);
+        static_lease = hashmap_get(server->static_leases_by_client_id, &req->client_id);
+
+        switch (type) {
+
+        case DHCP_DISCOVER: {
+                be32_t address = INADDR_ANY;
+
+                log_dhcp_server(server, "DISCOVER (0x%x)", be32toh(req->message->xid));
+
+                if (server->pool_size == 0)
+                        /* no pool allocated */
+                        return 0;
+
+                /* for now pick a random free address from the pool */
+                if (static_lease)
+                        address = static_lease->address;
+                else if (existing_lease)
+                        address = existing_lease->address;
+                else {
+                        struct siphash state;
+                        uint64_t hash;
+
+                        /* even with no persistence of leases, we try to offer the same client
+                           the same IP address. we do this by using the hash of the client id
+                           as the offset into the pool of leases when finding the next free one */
+
+                        siphash24_init(&state, HASH_KEY.bytes);
+                        client_id_hash_func(&req->client_id, &state);
+                        hash = htole64(siphash24_finalize(&state));
+
+                        for (unsigned i = 0; i < server->pool_size; i++) {
+                                be32_t tmp_address;
+
+                                tmp_address = server->subnet | htobe32(server->pool_offset + (hash + i) % server->pool_size);
+                                if (address_available(server, tmp_address)) {
+                                        address = tmp_address;
+                                        break;
+                                }
+                        }
+                }
+
+                if (address == INADDR_ANY)
+                        /* no free addresses left */
+                        return 0;
+
+                r = server_send_offer_or_ack(server, req, address, DHCP_OFFER);
+                if (r < 0)
+                        /* this only fails on critical errors */
+                        return log_dhcp_server_errno(server, r, "Could not send offer: %m");
+
+                log_dhcp_server(server, "OFFER (0x%x)", be32toh(req->message->xid));
+                return DHCP_OFFER;
+        }
+        case DHCP_DECLINE:
+                log_dhcp_server(server, "DECLINE (0x%x): %s", be32toh(req->message->xid), strna(error_message));
+
+                /* TODO: make sure we don't offer this address again */
+
+                return 1;
+
+        case DHCP_REQUEST: {
+                be32_t address;
+                bool init_reboot = false;
+
+                /* see RFC 2131, section 4.3.2 */
+
+                if (req->server_id != 0) {
+                        log_dhcp_server(server, "REQUEST (selecting) (0x%x)",
+                                        be32toh(req->message->xid));
+
+                        /* SELECTING */
+                        if (req->server_id != server->address)
+                                /* client did not pick us */
+                                return 0;
+
+                        if (req->message->ciaddr != 0)
+                                /* this MUST be zero */
+                                return 0;
+
+                        if (req->requested_ip == 0)
+                                /* this must be filled in with the yiaddr
+                                   from the chosen OFFER */
+                                return 0;
+
+                        address = req->requested_ip;
+                } else if (req->requested_ip != 0) {
+                        log_dhcp_server(server, "REQUEST (init-reboot) (0x%x)",
+                                        be32toh(req->message->xid));
+
+                        /* INIT-REBOOT */
+                        if (req->message->ciaddr != 0)
+                                /* this MUST be zero */
+                                return 0;
+
+                        /* TODO: check more carefully if IP is correct */
+                        address = req->requested_ip;
+                        init_reboot = true;
+                } else {
+                        log_dhcp_server(server, "REQUEST (rebinding/renewing) (0x%x)",
+                                        be32toh(req->message->xid));
+
+                        /* REBINDING / RENEWING */
+                        if (req->message->ciaddr == 0)
+                                /* this MUST be filled in with clients IP address */
+                                return 0;
+
+                        address = req->message->ciaddr;
+                }
+
+                /* disallow our own address */
+                if (address == server->address)
+                        return 0;
+
+                if (static_lease) {
+                        /* Found a static lease for the client ID. */
+
+                        if (static_lease->address != address)
+                                /* The client requested an address which is different from the static lease. Refuse. */
+                                return server_send_nak_or_ignore(server, init_reboot, req);
+
+                        return server_ack_request(server, req, existing_lease, address);
+                }
+
+                if (address_is_in_pool(server, address)) {
+                        /* The requested address is in the pool. */
+
+                        if (existing_lease && existing_lease->address != address)
+                                /* We previously assigned an address, but the client requested another one. Refuse. */
+                                return server_send_nak_or_ignore(server, init_reboot, req);
+
+                        return server_ack_request(server, req, existing_lease, address);
+                }
+
+                return server_send_nak_or_ignore(server, init_reboot, req);
+        }
+
+        case DHCP_RELEASE: {
+                log_dhcp_server(server, "RELEASE (0x%x)",
+                                be32toh(req->message->xid));
+
+                if (!existing_lease)
+                        return 0;
+
+                if (existing_lease->address != req->message->ciaddr)
+                        return 0;
+
+                dhcp_lease_free(existing_lease);
+
+                if (server->callback)
+                        server->callback(server, SD_DHCP_SERVER_EVENT_LEASE_CHANGED, server->callback_userdata);
+
+                return 0;
+        }}
+
+        return 0;
+}
+
+static size_t relay_agent_information_length(const char* agent_circuit_id, const char* agent_remote_id) {
+        size_t sum = 0;
+        if (agent_circuit_id)
+                sum += 2 + strlen(agent_circuit_id);
+        if (agent_remote_id)
+                sum += 2 + strlen(agent_remote_id);
+        return sum;
+}
+
+static int server_receive_message(sd_event_source *s, int fd,
+                                  uint32_t revents, void *userdata) {
+        _cleanup_free_ DHCPMessage *message = NULL;
+        CMSG_BUFFER_TYPE(CMSG_SPACE(sizeof(struct in_pktinfo))) control;
+        sd_dhcp_server *server = ASSERT_PTR(userdata);
+        struct iovec iov = {};
+        struct msghdr msg = {
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+        };
+        struct cmsghdr *cmsg;
+        ssize_t datagram_size, len;
+        int r;
+
+        datagram_size = next_datagram_size_fd(fd);
+        if (datagram_size < 0) {
+                if (ERRNO_IS_TRANSIENT(datagram_size) || ERRNO_IS_DISCONNECT(datagram_size))
+                        return 0;
+
+                log_dhcp_server_errno(server, datagram_size, "Failed to determine datagram size to read, ignoring: %m");
+                return 0;
+        }
+
+        size_t buflen = datagram_size;
+        if (sd_dhcp_server_is_in_relay_mode(server))
+                /* Preallocate the additional size for DHCP Relay Agent Information Option if needed */
+                buflen += relay_agent_information_length(server->agent_circuit_id, server->agent_remote_id) + 2;
+
+        message = malloc(buflen);
+        if (!message)
+                return -ENOMEM;
+
+        iov = IOVEC_MAKE(message, datagram_size);
+
+        len = recvmsg_safe(fd, &msg, 0);
+        if (len < 0) {
+                if (ERRNO_IS_TRANSIENT(len) || ERRNO_IS_DISCONNECT(len))
+                        return 0;
+
+                log_dhcp_server_errno(server, len, "Could not receive message, ignoring: %m");
+                return 0;
+        }
+
+        if ((size_t) len < sizeof(DHCPMessage))
+                return 0;
+
+        CMSG_FOREACH(cmsg, &msg)
+                if (cmsg->cmsg_level == IPPROTO_IP &&
+                    cmsg->cmsg_type == IP_PKTINFO &&
+                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct in_pktinfo))) {
+                        struct in_pktinfo *info = (struct in_pktinfo*)CMSG_DATA(cmsg);
+
+                        /* TODO figure out if this can be done as a filter on
+                         * the socket, like for IPv6 */
+                        if (server->ifindex != info->ipi_ifindex)
+                                return 0;
+
+                        break;
+                }
+
+        if (sd_dhcp_server_is_in_relay_mode(server)) {
+                r = dhcp_server_relay_message(server, message, len - sizeof(DHCPMessage), buflen);
+                if (r < 0)
+                        log_dhcp_server_errno(server, r, "Couldn't relay message, ignoring: %m");
+        } else {
+                r = dhcp_server_handle_message(server, message, (size_t) len);
+                if (r < 0)
+                        log_dhcp_server_errno(server, r, "Couldn't process incoming message, ignoring: %m");
+        }
+        return 0;
+}
+
+static void dhcp_server_update_lease_servers(sd_dhcp_server *server) {
+        assert(server);
+        assert(server->address != 0);
+
+        /* Convert null address -> server address */
+
+        for (sd_dhcp_lease_server_type_t k = 0; k < _SD_DHCP_LEASE_SERVER_TYPE_MAX; k++)
+                for (size_t i = 0; i < server->servers[k].size; i++)
+                        if (in4_addr_is_null(&server->servers[k].addr[i]))
+                                server->servers[k].addr[i].s_addr = server->address;
+}
+
+int sd_dhcp_server_start(sd_dhcp_server *server) {
+        int r;
+
+        assert_return(server, -EINVAL);
+        assert_return(server->event, -EINVAL);
+
+        if (sd_dhcp_server_is_running(server))
+                return 0;
+
+        assert_return(!server->receive_message, -EBUSY);
+        assert_return(server->fd_raw < 0, -EBUSY);
+        assert_return(server->fd < 0, -EBUSY);
+        assert_return(server->address != htobe32(INADDR_ANY), -EUNATCH);
+
+        dhcp_server_update_lease_servers(server);
+
+        r = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (r < 0) {
+                r = -errno;
+                goto on_error;
+        }
+        server->fd_raw = r;
+
+        if (server->bind_to_interface)
+                r = dhcp_network_bind_udp_socket(server->ifindex, INADDR_ANY, DHCP_PORT_SERVER, -1);
+        else
+                r = dhcp_network_bind_udp_socket(0, server->address, DHCP_PORT_SERVER, -1);
+        if (r < 0)
+                goto on_error;
+        server->fd = r;
+
+        r = sd_event_add_io(server->event, &server->receive_message,
+                            server->fd, EPOLLIN,
+                            server_receive_message, server);
+        if (r < 0)
+                goto on_error;
+
+        r = sd_event_source_set_priority(server->receive_message,
+                                         server->event_priority);
+        if (r < 0)
+                goto on_error;
+
+        if (!server->bind_to_interface) {
+                r = dhcp_network_bind_udp_socket(server->ifindex, INADDR_BROADCAST, DHCP_PORT_SERVER, -1);
+                if (r < 0)
+                        goto on_error;
+
+                server->fd_broadcast = r;
+
+                r = sd_event_add_io(server->event, &server->receive_broadcast,
+                                    server->fd_broadcast, EPOLLIN,
+                                    server_receive_message, server);
+                if (r < 0)
+                        goto on_error;
+
+                r = sd_event_source_set_priority(server->receive_broadcast,
+                                                 server->event_priority);
+                if (r < 0)
+                        goto on_error;
+        }
+
+        log_dhcp_server(server, "STARTED");
+
+        return 0;
+
+on_error:
+        sd_dhcp_server_stop(server);
+        return r;
+}
+
+int sd_dhcp_server_forcerenew(sd_dhcp_server *server) {
+        DHCPLease *lease;
+        int k, r = 0;
+
+        assert_return(server, -EINVAL);
+
+        log_dhcp_server(server, "FORCERENEW");
+
+        HASHMAP_FOREACH(lease, server->bound_leases_by_client_id) {
+                k = server_send_forcerenew(server, lease->address, lease->gateway,
+                                           lease->htype, lease->hlen, lease->chaddr);
+                if (k < 0)
+                        r = k;
+        }
+
+        return r;
+}
+
+int sd_dhcp_server_set_bind_to_interface(sd_dhcp_server *server, int enabled) {
+        assert_return(server, -EINVAL);
+        assert_return(!sd_dhcp_server_is_running(server), -EBUSY);
+
+        if (!!enabled == server->bind_to_interface)
+                return 0;
+
+        server->bind_to_interface = enabled;
+
+        return 1;
+}
+
+int sd_dhcp_server_set_timezone(sd_dhcp_server *server, const char *tz) {
+        int r;
+
+        assert_return(server, -EINVAL);
+        assert_return(timezone_is_valid(tz, LOG_DEBUG), -EINVAL);
+
+        if (streq_ptr(tz, server->timezone))
+                return 0;
+
+        r = free_and_strdup(&server->timezone, tz);
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+int sd_dhcp_server_set_max_lease_time(sd_dhcp_server *server, uint32_t t) {
+        assert_return(server, -EINVAL);
+
+        if (t == server->max_lease_time)
+                return 0;
+
+        server->max_lease_time = t;
+        return 1;
+}
+
+int sd_dhcp_server_set_default_lease_time(sd_dhcp_server *server, uint32_t t) {
+        assert_return(server, -EINVAL);
+
+        if (t == server->default_lease_time)
+                return 0;
+
+        server->default_lease_time = t;
+        return 1;
+}
+
+int sd_dhcp_server_set_servers(
+                sd_dhcp_server *server,
+                sd_dhcp_lease_server_type_t what,
+                const struct in_addr addresses[],
+                size_t n_addresses) {
+
+        struct in_addr *c = NULL;
+
+        assert_return(server, -EINVAL);
+        assert_return(!sd_dhcp_server_is_running(server), -EBUSY);
+        assert_return(addresses || n_addresses == 0, -EINVAL);
+        assert_return(what >= 0, -EINVAL);
+        assert_return(what < _SD_DHCP_LEASE_SERVER_TYPE_MAX, -EINVAL);
+
+        if (server->servers[what].size == n_addresses &&
+            memcmp(server->servers[what].addr, addresses, sizeof(struct in_addr) * n_addresses) == 0)
+                return 0;
+
+        if (n_addresses > 0) {
+                c = newdup(struct in_addr, addresses, n_addresses);
+                if (!c)
+                        return -ENOMEM;
+        }
+
+        free_and_replace(server->servers[what].addr, c);
+        server->servers[what].size = n_addresses;
+        return 1;
+}
+
+int sd_dhcp_server_set_dns(sd_dhcp_server *server, const struct in_addr dns[], size_t n) {
+        return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_DNS, dns, n);
+}
+int sd_dhcp_server_set_ntp(sd_dhcp_server *server, const struct in_addr ntp[], size_t n) {
+        return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_NTP, ntp, n);
+}
+int sd_dhcp_server_set_sip(sd_dhcp_server *server, const struct in_addr sip[], size_t n) {
+        return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_SIP, sip, n);
+}
+int sd_dhcp_server_set_pop3(sd_dhcp_server *server, const struct in_addr pop3[], size_t n) {
+        return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_POP3, pop3, n);
+}
+int sd_dhcp_server_set_smtp(sd_dhcp_server *server, const struct in_addr smtp[], size_t n) {
+        return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_SMTP, smtp, n);
+}
+int sd_dhcp_server_set_lpr(sd_dhcp_server *server, const struct in_addr lpr[], size_t n) {
+        return sd_dhcp_server_set_servers(server, SD_DHCP_LEASE_LPR, lpr, n);
+}
+
+int sd_dhcp_server_set_router(sd_dhcp_server *server, const struct in_addr *router) {
+        assert_return(server, -EINVAL);
+
+        /* router is NULL: router option will not be appended.
+         * router is null address (0.0.0.0): the server address will be used as the router address.
+         * otherwise: the specified address will be used as the router address.*/
+
+        server->emit_router = router;
+        if (router)
+                server->router_address = *router;
+
+        return 0;
+}
+
+int sd_dhcp_server_add_option(sd_dhcp_server *server, sd_dhcp_option *v) {
+        int r;
+
+        assert_return(server, -EINVAL);
+        assert_return(v, -EINVAL);
+
+        r = ordered_set_ensure_put(&server->extra_options, &dhcp_option_hash_ops, v);
+        if (r < 0)
+                return r;
+
+        sd_dhcp_option_ref(v);
+        return 0;
+}
+
+int sd_dhcp_server_add_vendor_option(sd_dhcp_server *server, sd_dhcp_option *v) {
+        int r;
+
+        assert_return(server, -EINVAL);
+        assert_return(v, -EINVAL);
+
+        r = ordered_set_ensure_put(&server->vendor_options, &dhcp_option_hash_ops, v);
+        if (r < 0)
+                return r;
+
+        sd_dhcp_option_ref(v);
+
+        return 1;
+}
+
+int sd_dhcp_server_set_callback(sd_dhcp_server *server, sd_dhcp_server_callback_t cb, void *userdata) {
+        assert_return(server, -EINVAL);
+
+        server->callback = cb;
+        server->callback_userdata = userdata;
+
+        return 0;
+}
+
+int sd_dhcp_server_set_relay_target(sd_dhcp_server *server, const struct in_addr *address) {
+        assert_return(server, -EINVAL);
+        assert_return(!sd_dhcp_server_is_running(server), -EBUSY);
+
+        if (memcmp(address, &server->relay_target, sizeof(struct in_addr)) == 0)
+                return 0;
+
+        server->relay_target = *address;
+        return 1;
+}
+
+int sd_dhcp_server_set_relay_agent_information(
+                sd_dhcp_server *server,
+                const char *agent_circuit_id,
+                const char *agent_remote_id) {
+        _cleanup_free_ char *circuit_id_dup = NULL, *remote_id_dup = NULL;
+
+        assert_return(server, -EINVAL);
+
+        if (relay_agent_information_length(agent_circuit_id, agent_remote_id) > UINT8_MAX)
+                return -ENOBUFS;
+
+        if (agent_circuit_id) {
+                circuit_id_dup = strdup(agent_circuit_id);
+                if (!circuit_id_dup)
+                        return -ENOMEM;
+        }
+
+        if (agent_remote_id) {
+                remote_id_dup = strdup(agent_remote_id);
+                if (!remote_id_dup)
+                        return -ENOMEM;
+        }
+
+        free_and_replace(server->agent_circuit_id, circuit_id_dup);
+        free_and_replace(server->agent_remote_id, remote_id_dup);
+        return 0;
+}
+
+int sd_dhcp_server_set_static_lease(
+                sd_dhcp_server *server,
+                const struct in_addr *address,
+                uint8_t *client_id,
+                size_t client_id_size) {
+
+        _cleanup_(dhcp_lease_freep) DHCPLease *lease = NULL;
+        int r;
+
+        assert_return(server, -EINVAL);
+        assert_return(client_id, -EINVAL);
+        assert_return(client_id_size > 0, -EINVAL);
+        assert_return(!sd_dhcp_server_is_running(server), -EBUSY);
+
+        /* Static lease with an empty or omitted address is a valid entry,
+         * the server removes any static lease with the specified mac address. */
+        if (!address || address->s_addr == 0) {
+                DHCPClientId c;
+
+                c = (DHCPClientId) {
+                        .length = client_id_size,
+                        .data = client_id,
+                };
+
+                dhcp_lease_free(hashmap_get(server->static_leases_by_client_id, &c));
+                return 0;
+        }
+
+        lease = new(DHCPLease, 1);
+        if (!lease)
+                return -ENOMEM;
+
+        *lease = (DHCPLease) {
+                .address = address->s_addr,
+                .client_id.length = client_id_size,
+        };
+        lease->client_id.data = memdup(client_id, client_id_size);
+        if (!lease->client_id.data)
+                return -ENOMEM;
+
+        lease->server = server; /* This must be set just before hashmap_put(). */
+
+        r = hashmap_ensure_put(&server->static_leases_by_client_id, &dhcp_lease_hash_ops, &lease->client_id, lease);
+        if (r < 0)
+                return r;
+        r = hashmap_ensure_put(&server->static_leases_by_address, NULL, UINT32_TO_PTR(lease->address), lease);
+        if (r < 0)
+                return r;
+
+        TAKE_PTR(lease);
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-dhcp6-client.c b/src/libsystemd-network/sd-dhcp6-client.c
new file mode 100644
index 0000000..57260c2
--- /dev/null
+++ b/src/libsystemd-network/sd-dhcp6-client.c
@@ -0,0 +1,1501 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014-2015 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <sys/ioctl.h>
+#include <linux/if_arp.h>
+#include <linux/if_infiniband.h>
+
+#include "sd-dhcp6-client.h"
+
+#include "alloc-util.h"
+#include "dhcp-identifier.h"
+#include "dhcp6-internal.h"
+#include "dhcp6-lease-internal.h"
+#include "dns-domain.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "hexdecoct.h"
+#include "hostname-util.h"
+#include "in-addr-util.h"
+#include "io-util.h"
+#include "random-util.h"
+#include "socket-util.h"
+#include "sort-util.h"
+#include "strv.h"
+#include "web-util.h"
+
+#define DHCP6_CLIENT_DONT_DESTROY(client) \
+        _cleanup_(sd_dhcp6_client_unrefp) _unused_ sd_dhcp6_client *_dont_destroy_##client = sd_dhcp6_client_ref(client)
+
+static int client_start_transaction(sd_dhcp6_client *client, DHCP6State state);
+
+int sd_dhcp6_client_set_callback(
+                sd_dhcp6_client *client,
+                sd_dhcp6_client_callback_t cb,
+                void *userdata) {
+
+        assert_return(client, -EINVAL);
+
+        client->callback = cb;
+        client->userdata = userdata;
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_ifindex(sd_dhcp6_client *client, int ifindex) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(ifindex > 0, -EINVAL);
+
+        client->ifindex = ifindex;
+        return 0;
+}
+
+int sd_dhcp6_client_set_ifname(sd_dhcp6_client *client, const char *ifname) {
+        assert_return(client, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&client->ifname, ifname);
+}
+
+int sd_dhcp6_client_get_ifname(sd_dhcp6_client *client, const char **ret) {
+        int r;
+
+        assert_return(client, -EINVAL);
+
+        r = get_ifname(client->ifindex, &client->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = client->ifname;
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_local_address(
+                sd_dhcp6_client *client,
+                const struct in6_addr *local_address) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(local_address, -EINVAL);
+        assert_return(in6_addr_is_link_local(local_address) > 0, -EINVAL);
+
+        client->local_address = *local_address;
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_mac(
+                sd_dhcp6_client *client,
+                const uint8_t *addr,
+                size_t addr_len,
+                uint16_t arp_type) {
+
+        assert_return(client, -EINVAL);
+        assert_return(addr, -EINVAL);
+        assert_return(addr_len <= sizeof(client->hw_addr.bytes), -EINVAL);
+
+        /* Unlike the other setters, it is OK to set a new MAC address while the client is running,
+         * as the MAC address is used only when setting DUID or IAID. */
+
+        if (arp_type == ARPHRD_ETHER)
+                assert_return(addr_len == ETH_ALEN, -EINVAL);
+        else if (arp_type == ARPHRD_INFINIBAND)
+                assert_return(addr_len == INFINIBAND_ALEN, -EINVAL);
+        else {
+                client->arp_type = ARPHRD_NONE;
+                client->hw_addr.length = 0;
+                return 0;
+        }
+
+        client->arp_type = arp_type;
+        hw_addr_set(&client->hw_addr, addr, addr_len);
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_prefix_delegation_hint(
+                sd_dhcp6_client *client,
+                uint8_t prefixlen,
+                const struct in6_addr *pd_prefix) {
+
+        _cleanup_free_ DHCP6Address *prefix = NULL;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        if (!pd_prefix) {
+                /* clear previous assignments. */
+                dhcp6_ia_clear_addresses(&client->ia_pd);
+                return 0;
+        }
+
+        assert_return(prefixlen > 0 && prefixlen <= 128, -EINVAL);
+
+        prefix = new(DHCP6Address, 1);
+        if (!prefix)
+                return -ENOMEM;
+
+        *prefix = (DHCP6Address) {
+                .iapdprefix.address = *pd_prefix,
+                .iapdprefix.prefixlen = prefixlen,
+        };
+
+        LIST_PREPEND(addresses, client->ia_pd.addresses, TAKE_PTR(prefix));
+        return 1;
+}
+
+int sd_dhcp6_client_add_vendor_option(sd_dhcp6_client *client, sd_dhcp6_option *v) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        if (!v) {
+                /* Clear the previous assignments. */
+                ordered_set_clear(client->vendor_options);
+                return 0;
+        }
+
+        r = ordered_set_ensure_put(&client->vendor_options, &dhcp6_option_hash_ops, v);
+        if (r < 0)
+                return r;
+
+        sd_dhcp6_option_ref(v);
+
+        return 1;
+}
+
+static int client_ensure_duid(sd_dhcp6_client *client) {
+        assert(client);
+
+        if (client->duid_len != 0)
+                return 0;
+
+        return dhcp_identifier_set_duid_en(client->test_mode, &client->duid, &client->duid_len);
+}
+
+/**
+ * Sets DUID. If duid is non-null, the DUID is set to duid_type + duid
+ * without further modification. Otherwise, if duid_type is supported, DUID
+ * is set based on that type. Otherwise, an error is returned.
+ */
+static int dhcp6_client_set_duid_internal(
+                sd_dhcp6_client *client,
+                DUIDType duid_type,
+                const void *duid,
+                size_t duid_len,
+                usec_t llt_time) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(duid_len == 0 || duid, -EINVAL);
+
+        if (duid) {
+                r = dhcp_validate_duid_len(duid_type, duid_len, true);
+                if (r < 0) {
+                        r = dhcp_validate_duid_len(duid_type, duid_len, false);
+                        if (r < 0)
+                                return log_dhcp6_client_errno(client, r, "Failed to validate length of DUID: %m");
+
+                        log_dhcp6_client(client, "Using DUID of type %i of incorrect length, proceeding.", duid_type);
+                }
+
+                client->duid.type = htobe16(duid_type);
+                memcpy(&client->duid.raw.data, duid, duid_len);
+                client->duid_len = sizeof(client->duid.type) + duid_len;
+
+        } else {
+                r = dhcp_identifier_set_duid(duid_type, &client->hw_addr, client->arp_type, llt_time,
+                                             client->test_mode, &client->duid, &client->duid_len);
+                if (r == -EOPNOTSUPP)
+                        return log_dhcp6_client_errno(client, r,
+                                                      "Failed to set %s. MAC address is not set or "
+                                                      "interface type is not supported.",
+                                                      duid_type_to_string(duid_type));
+                if (r < 0)
+                        return log_dhcp6_client_errno(client, r, "Failed to set %s: %m",
+                                                      duid_type_to_string(duid_type));
+        }
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_duid(
+                sd_dhcp6_client *client,
+                uint16_t duid_type,
+                const void *duid,
+                size_t duid_len) {
+        return dhcp6_client_set_duid_internal(client, duid_type, duid, duid_len, 0);
+}
+
+int sd_dhcp6_client_set_duid_llt(
+                sd_dhcp6_client *client,
+                usec_t llt_time) {
+        return dhcp6_client_set_duid_internal(client, DUID_TYPE_LLT, NULL, 0, llt_time);
+}
+
+int sd_dhcp6_client_duid_as_string(
+                sd_dhcp6_client *client,
+                char **duid) {
+        _cleanup_free_ char *p = NULL, *s = NULL, *t = NULL;
+        const char *v;
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(client->duid_len > offsetof(struct duid, raw.data), -ENODATA);
+        assert_return(duid, -EINVAL);
+
+        v = duid_type_to_string(be16toh(client->duid.type));
+        if (v) {
+                s = strdup(v);
+                if (!s)
+                        return -ENOMEM;
+        } else {
+                r = asprintf(&s, "%0x", client->duid.type);
+                if (r < 0)
+                        return -ENOMEM;
+        }
+
+        t = hexmem(client->duid.raw.data, client->duid_len - offsetof(struct duid, raw.data));
+        if (!t)
+                return -ENOMEM;
+
+        p = strjoin(s, ":", t);
+        if (!p)
+                return -ENOMEM;
+
+        *duid = TAKE_PTR(p);
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_iaid(sd_dhcp6_client *client, uint32_t iaid) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        client->ia_na.header.id = htobe32(iaid);
+        client->ia_pd.header.id = htobe32(iaid);
+        client->iaid_set = true;
+
+        return 0;
+}
+
+static int client_ensure_iaid(sd_dhcp6_client *client) {
+        int r;
+        uint32_t iaid;
+
+        assert(client);
+
+        if (client->iaid_set)
+                return 0;
+
+        r = dhcp_identifier_set_iaid(client->ifindex, &client->hw_addr,
+                                     /* legacy_unstable_byteorder = */ true,
+                                     /* use_mac = */ client->test_mode,
+                                     &iaid);
+        if (r < 0)
+                return r;
+
+        client->ia_na.header.id = iaid;
+        client->ia_pd.header.id = iaid;
+        client->iaid_set = true;
+
+        return 0;
+}
+
+int sd_dhcp6_client_get_iaid(sd_dhcp6_client *client, uint32_t *iaid) {
+        assert_return(client, -EINVAL);
+        assert_return(iaid, -EINVAL);
+
+        if (!client->iaid_set)
+                return -ENODATA;
+
+        *iaid = be32toh(client->ia_na.header.id);
+
+        return 0;
+}
+
+void dhcp6_client_set_test_mode(sd_dhcp6_client *client, bool test_mode) {
+        assert(client);
+
+        client->test_mode = test_mode;
+}
+
+int sd_dhcp6_client_set_fqdn(
+                sd_dhcp6_client *client,
+                const char *fqdn) {
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        /* Make sure FQDN qualifies as DNS and as Linux hostname */
+        if (fqdn &&
+            !(hostname_is_valid(fqdn, 0) && dns_name_is_valid(fqdn) > 0))
+                return -EINVAL;
+
+        return free_and_strdup(&client->fqdn, fqdn);
+}
+
+int sd_dhcp6_client_set_information_request(sd_dhcp6_client *client, int enabled) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        client->information_request = enabled;
+
+        return 0;
+}
+
+int sd_dhcp6_client_get_information_request(sd_dhcp6_client *client, int *enabled) {
+        assert_return(client, -EINVAL);
+        assert_return(enabled, -EINVAL);
+
+        *enabled = client->information_request;
+
+        return 0;
+}
+
+static int be16_compare_func(const be16_t *a, const be16_t *b) {
+        return CMP(be16toh(*a), be16toh(*b));
+}
+
+int sd_dhcp6_client_set_request_option(sd_dhcp6_client *client, uint16_t option) {
+        be16_t opt;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        if (!dhcp6_option_can_request(option))
+                return -EINVAL;
+
+        opt = htobe16(option);
+        if (typesafe_bsearch(&opt, client->req_opts, client->n_req_opts, be16_compare_func))
+                return -EEXIST;
+
+        if (!GREEDY_REALLOC(client->req_opts, client->n_req_opts + 1))
+                return -ENOMEM;
+
+        client->req_opts[client->n_req_opts++] = opt;
+
+        /* Sort immediately to make the above binary search will work for the next time. */
+        typesafe_qsort(client->req_opts, client->n_req_opts, be16_compare_func);
+        return 0;
+}
+
+int sd_dhcp6_client_set_request_mud_url(sd_dhcp6_client *client, const char *mudurl) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(mudurl, -EINVAL);
+        assert_return(strlen(mudurl) <= UINT8_MAX, -EINVAL);
+        assert_return(http_url_is_valid(mudurl), -EINVAL);
+
+        return free_and_strdup(&client->mudurl, mudurl);
+}
+
+int sd_dhcp6_client_set_request_user_class(sd_dhcp6_client *client, char * const *user_class) {
+        char **s;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(!strv_isempty(user_class), -EINVAL);
+
+        STRV_FOREACH(p, user_class) {
+                size_t len = strlen(*p);
+
+                if (len > UINT16_MAX || len == 0)
+                        return -EINVAL;
+        }
+
+        s = strv_copy(user_class);
+        if (!s)
+                return -ENOMEM;
+
+        return strv_free_and_replace(client->user_class, s);
+}
+
+int sd_dhcp6_client_set_request_vendor_class(sd_dhcp6_client *client, char * const *vendor_class) {
+        char **s;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(!strv_isempty(vendor_class), -EINVAL);
+
+        STRV_FOREACH(p, vendor_class) {
+                size_t len = strlen(*p);
+
+                if (len > UINT16_MAX || len == 0)
+                        return -EINVAL;
+        }
+
+        s = strv_copy(vendor_class);
+        if (!s)
+                return -ENOMEM;
+
+        return strv_free_and_replace(client->vendor_class, s);
+}
+
+int sd_dhcp6_client_get_prefix_delegation(sd_dhcp6_client *client, int *delegation) {
+        assert_return(client, -EINVAL);
+        assert_return(delegation, -EINVAL);
+
+        *delegation = FLAGS_SET(client->request_ia, DHCP6_REQUEST_IA_PD);
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_prefix_delegation(sd_dhcp6_client *client, int delegation) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        SET_FLAG(client->request_ia, DHCP6_REQUEST_IA_PD, delegation);
+
+        return 0;
+}
+
+int sd_dhcp6_client_get_address_request(sd_dhcp6_client *client, int *request) {
+        assert_return(client, -EINVAL);
+        assert_return(request, -EINVAL);
+
+        *request = FLAGS_SET(client->request_ia, DHCP6_REQUEST_IA_NA);
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_address_request(sd_dhcp6_client *client, int request) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        SET_FLAG(client->request_ia, DHCP6_REQUEST_IA_NA, request);
+
+        return 0;
+}
+
+int dhcp6_client_set_transaction_id(sd_dhcp6_client *client, uint32_t transaction_id) {
+        assert(client);
+        assert(client->test_mode);
+
+        /* This is for tests or fuzzers. */
+
+        client->transaction_id = transaction_id & htobe32(0x00ffffff);
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_rapid_commit(sd_dhcp6_client *client, int enable) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        client->rapid_commit = enable;
+        return 0;
+}
+
+int sd_dhcp6_client_get_lease(sd_dhcp6_client *client, sd_dhcp6_lease **ret) {
+        assert_return(client, -EINVAL);
+
+        if (!client->lease)
+                return -ENOMSG;
+
+        if (ret)
+                *ret = client->lease;
+
+        return 0;
+}
+
+int sd_dhcp6_client_add_option(sd_dhcp6_client *client, sd_dhcp6_option *v) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(v, -EINVAL);
+
+        r = ordered_hashmap_ensure_put(&client->extra_options, &dhcp6_option_hash_ops, UINT_TO_PTR(v->option), v);
+        if (r < 0)
+                return r;
+
+        sd_dhcp6_option_ref(v);
+        return 0;
+}
+
+static void client_set_state(sd_dhcp6_client *client, DHCP6State state) {
+        assert(client);
+
+        if (client->state == state)
+                return;
+
+        log_dhcp6_client(client, "State changed: %s -> %s",
+                         dhcp6_state_to_string(client->state), dhcp6_state_to_string(state));
+
+        client->state = state;
+}
+
+static void client_notify(sd_dhcp6_client *client, int event) {
+        assert(client);
+
+        if (client->callback)
+                client->callback(client, event, client->userdata);
+}
+
+static void client_cleanup(sd_dhcp6_client *client) {
+        assert(client);
+
+        client->lease = sd_dhcp6_lease_unref(client->lease);
+
+        /* Reset IRT here. Otherwise, we cannot restart the client in the information requesting mode,
+         * even though the lease is freed below. */
+        client->information_request_time_usec = 0;
+        client->information_refresh_time_usec = 0;
+
+        (void) event_source_disable(client->receive_message);
+        (void) event_source_disable(client->timeout_resend);
+        (void) event_source_disable(client->timeout_expire);
+        (void) event_source_disable(client->timeout_t1);
+        (void) event_source_disable(client->timeout_t2);
+
+        client_set_state(client, DHCP6_STATE_STOPPED);
+}
+
+static void client_stop(sd_dhcp6_client *client, int error) {
+        DHCP6_CLIENT_DONT_DESTROY(client);
+
+        assert(client);
+
+        client_notify(client, error);
+
+        client_cleanup(client);
+}
+
+static int client_append_common_options_in_managed_mode(
+                sd_dhcp6_client *client,
+                uint8_t **buf,
+                size_t *offset,
+                const DHCP6IA *ia_na,
+                const DHCP6IA *ia_pd) {
+
+        int r;
+
+        assert(client);
+        assert(IN_SET(client->state,
+                      DHCP6_STATE_SOLICITATION,
+                      DHCP6_STATE_REQUEST,
+                      DHCP6_STATE_RENEW,
+                      DHCP6_STATE_REBIND));
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        if (FLAGS_SET(client->request_ia, DHCP6_REQUEST_IA_NA) && ia_na) {
+                r = dhcp6_option_append_ia(buf, offset, ia_na);
+                if (r < 0)
+                        return r;
+        }
+
+        if (FLAGS_SET(client->request_ia, DHCP6_REQUEST_IA_PD) && ia_pd) {
+                r = dhcp6_option_append_ia(buf, offset, ia_pd);
+                if (r < 0)
+                        return r;
+        }
+
+        r = dhcp6_option_append_fqdn(buf, offset, client->fqdn);
+        if (r < 0)
+                return r;
+
+        r = dhcp6_option_append_user_class(buf, offset, client->user_class);
+        if (r < 0)
+                return r;
+
+        r = dhcp6_option_append_vendor_class(buf, offset, client->vendor_class);
+        if (r < 0)
+                return r;
+
+        r = dhcp6_option_append_vendor_option(buf, offset, client->vendor_options);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static DHCP6MessageType client_message_type_from_state(sd_dhcp6_client *client) {
+        assert(client);
+
+        switch (client->state) {
+        case DHCP6_STATE_INFORMATION_REQUEST:
+                return DHCP6_MESSAGE_INFORMATION_REQUEST;
+        case DHCP6_STATE_SOLICITATION:
+                return DHCP6_MESSAGE_SOLICIT;
+        case DHCP6_STATE_REQUEST:
+                return DHCP6_MESSAGE_REQUEST;
+        case DHCP6_STATE_RENEW:
+                return DHCP6_MESSAGE_RENEW;
+        case DHCP6_STATE_REBIND:
+                return DHCP6_MESSAGE_REBIND;
+        default:
+                assert_not_reached();
+        }
+}
+
+static int client_append_oro(sd_dhcp6_client *client, uint8_t **buf, size_t *offset) {
+        _cleanup_free_ be16_t *p = NULL;
+        be16_t *req_opts;
+        size_t n;
+
+        assert(client);
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        switch (client->state) {
+        case DHCP6_STATE_INFORMATION_REQUEST:
+                n = client->n_req_opts;
+                p = new(be16_t, n + 2);
+                if (!p)
+                        return -ENOMEM;
+
+                memcpy_safe(p, client->req_opts, n * sizeof(be16_t));
+                p[n++] = htobe16(SD_DHCP6_OPTION_INFORMATION_REFRESH_TIME); /* RFC 8415 section 21.23 */
+                p[n++] = htobe16(SD_DHCP6_OPTION_INF_MAX_RT); /* RFC 8415 section 21.25 */
+
+                typesafe_qsort(p, n, be16_compare_func);
+                req_opts = p;
+                break;
+
+        case DHCP6_STATE_SOLICITATION:
+                n = client->n_req_opts;
+                p = new(be16_t, n + 1);
+                if (!p)
+                        return -ENOMEM;
+
+                memcpy_safe(p, client->req_opts, n * sizeof(be16_t));
+                p[n++] = htobe16(SD_DHCP6_OPTION_SOL_MAX_RT); /* RFC 8415 section 21.24 */
+
+                typesafe_qsort(p, n, be16_compare_func);
+                req_opts = p;
+                break;
+
+        default:
+                n = client->n_req_opts;
+                req_opts = client->req_opts;
+        }
+
+        if (n == 0)
+                return 0;
+
+        return dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_ORO, n * sizeof(be16_t), req_opts);
+}
+
+int dhcp6_client_send_message(sd_dhcp6_client *client) {
+        _cleanup_free_ uint8_t *buf = NULL;
+        struct in6_addr all_servers =
+                IN6ADDR_ALL_DHCP6_RELAY_AGENTS_AND_SERVERS_INIT;
+        struct sd_dhcp6_option *j;
+        usec_t elapsed_usec, time_now;
+        be16_t elapsed_time;
+        DHCP6Message *message;
+        size_t offset;
+        int r;
+
+        assert(client);
+        assert(client->event);
+
+        r = sd_event_now(client->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                return r;
+
+        if (!GREEDY_REALLOC0(buf, offsetof(DHCP6Message, options)))
+                return -ENOMEM;
+
+        message = (DHCP6Message*) buf;
+        message->transaction_id = client->transaction_id;
+        message->type = client_message_type_from_state(client);
+        offset = offsetof(DHCP6Message, options);
+
+        switch (client->state) {
+        case DHCP6_STATE_INFORMATION_REQUEST:
+                break;
+
+        case DHCP6_STATE_SOLICITATION:
+                if (client->rapid_commit) {
+                        r = dhcp6_option_append(&buf, &offset, SD_DHCP6_OPTION_RAPID_COMMIT, 0, NULL);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = client_append_common_options_in_managed_mode(client, &buf, &offset,
+                                                                 &client->ia_na, &client->ia_pd);
+                if (r < 0)
+                        return r;
+                break;
+
+        case DHCP6_STATE_REQUEST:
+        case DHCP6_STATE_RENEW:
+
+                r = dhcp6_option_append(&buf, &offset, SD_DHCP6_OPTION_SERVERID,
+                                        client->lease->serverid_len,
+                                        client->lease->serverid);
+                if (r < 0)
+                        return r;
+
+                _fallthrough_;
+        case DHCP6_STATE_REBIND:
+
+                assert(client->lease);
+
+                r = client_append_common_options_in_managed_mode(client, &buf, &offset,
+                                                                 client->lease->ia_na, client->lease->ia_pd);
+                if (r < 0)
+                        return r;
+                break;
+
+        case DHCP6_STATE_STOPPED:
+        case DHCP6_STATE_BOUND:
+        default:
+                assert_not_reached();
+        }
+
+        if (client->mudurl) {
+                r = dhcp6_option_append(&buf, &offset, SD_DHCP6_OPTION_MUD_URL_V6,
+                                        strlen(client->mudurl), client->mudurl);
+                if (r < 0)
+                        return r;
+        }
+
+        r = client_append_oro(client, &buf, &offset);
+        if (r < 0)
+                return r;
+
+        assert(client->duid_len > 0);
+        r = dhcp6_option_append(&buf, &offset, SD_DHCP6_OPTION_CLIENTID,
+                                client->duid_len, &client->duid);
+        if (r < 0)
+                return r;
+
+        ORDERED_HASHMAP_FOREACH(j, client->extra_options) {
+                r = dhcp6_option_append(&buf, &offset, j->option, j->length, j->data);
+                if (r < 0)
+                        return r;
+        }
+
+        /* RFC 8415 Section 21.9.
+         * A client MUST include an Elapsed Time option in messages to indicate how long the client has
+         * been trying to complete a DHCP message exchange. */
+        elapsed_usec = MIN(usec_sub_unsigned(time_now, client->transaction_start) / USEC_PER_MSEC / 10, (usec_t) UINT16_MAX);
+        elapsed_time = htobe16(elapsed_usec);
+        r = dhcp6_option_append(&buf, &offset, SD_DHCP6_OPTION_ELAPSED_TIME, sizeof(elapsed_time), &elapsed_time);
+        if (r < 0)
+                return r;
+
+        r = dhcp6_network_send_udp_socket(client->fd, &all_servers, buf, offset);
+        if (r < 0)
+                return r;
+
+        log_dhcp6_client(client, "Sent %s",
+                         dhcp6_message_type_to_string(client_message_type_from_state(client)));
+        return 0;
+}
+
+static usec_t client_timeout_compute_random(usec_t val) {
+        return usec_sub_unsigned(val, random_u64_range(val / 10));
+}
+
+static int client_timeout_resend(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp6_client *client = ASSERT_PTR(userdata);
+        usec_t init_retransmit_time, max_retransmit_time;
+        int r;
+
+        assert(client->event);
+
+        switch (client->state) {
+        case DHCP6_STATE_INFORMATION_REQUEST:
+                init_retransmit_time = DHCP6_INF_TIMEOUT;
+                max_retransmit_time = DHCP6_INF_MAX_RT;
+                break;
+
+        case DHCP6_STATE_SOLICITATION:
+
+                if (client->retransmit_count > 0 && client->lease) {
+                        (void) client_start_transaction(client, DHCP6_STATE_REQUEST);
+                        return 0;
+                }
+
+                init_retransmit_time = DHCP6_SOL_TIMEOUT;
+                max_retransmit_time = DHCP6_SOL_MAX_RT;
+                break;
+
+        case DHCP6_STATE_REQUEST:
+
+                if (client->retransmit_count >= DHCP6_REQ_MAX_RC) {
+                        client_stop(client, SD_DHCP6_CLIENT_EVENT_RETRANS_MAX);
+                        return 0;
+                }
+
+                init_retransmit_time = DHCP6_REQ_TIMEOUT;
+                max_retransmit_time = DHCP6_REQ_MAX_RT;
+                break;
+
+        case DHCP6_STATE_RENEW:
+                init_retransmit_time = DHCP6_REN_TIMEOUT;
+                max_retransmit_time = DHCP6_REN_MAX_RT;
+
+                /* RFC 3315, section 18.1.3. says max retransmit duration will
+                   be the remaining time until T2. Instead of setting MRD,
+                   wait for T2 to trigger with the same end result */
+                break;
+
+        case DHCP6_STATE_REBIND:
+                init_retransmit_time = DHCP6_REB_TIMEOUT;
+                max_retransmit_time = DHCP6_REB_MAX_RT;
+
+                /* Also, instead of setting MRD, the expire timer is already set in client_enter_bound_state(). */
+                break;
+
+        case DHCP6_STATE_STOPPED:
+        case DHCP6_STATE_BOUND:
+        default:
+                assert_not_reached();
+        }
+
+        r = dhcp6_client_send_message(client);
+        if (r >= 0)
+                client->retransmit_count++;
+
+        if (client->retransmit_time == 0) {
+                client->retransmit_time = client_timeout_compute_random(init_retransmit_time);
+
+                if (client->state == DHCP6_STATE_SOLICITATION)
+                        client->retransmit_time += init_retransmit_time / 10;
+
+        } else if (client->retransmit_time > max_retransmit_time / 2)
+                client->retransmit_time = client_timeout_compute_random(max_retransmit_time);
+        else
+                client->retransmit_time += client_timeout_compute_random(client->retransmit_time);
+
+        log_dhcp6_client(client, "Next retransmission in %s",
+                         FORMAT_TIMESPAN(client->retransmit_time, USEC_PER_SEC));
+
+        r = event_reset_time_relative(client->event, &client->timeout_resend,
+                                      CLOCK_BOOTTIME,
+                                      client->retransmit_time, 10 * USEC_PER_MSEC,
+                                      client_timeout_resend, client,
+                                      client->event_priority, "dhcp6-resend-timer", true);
+        if (r < 0)
+                client_stop(client, r);
+
+        return 0;
+}
+
+static int client_start_transaction(sd_dhcp6_client *client, DHCP6State state) {
+        int r;
+
+        assert(client);
+        assert(client->event);
+
+        switch (state) {
+        case DHCP6_STATE_INFORMATION_REQUEST:
+        case DHCP6_STATE_SOLICITATION:
+                assert(client->state == DHCP6_STATE_STOPPED);
+                break;
+        case DHCP6_STATE_REQUEST:
+                assert(client->state == DHCP6_STATE_SOLICITATION);
+                break;
+        case DHCP6_STATE_RENEW:
+                assert(client->state == DHCP6_STATE_BOUND);
+                break;
+        case DHCP6_STATE_REBIND:
+                assert(IN_SET(client->state, DHCP6_STATE_BOUND, DHCP6_STATE_RENEW));
+                break;
+        case DHCP6_STATE_STOPPED:
+        case DHCP6_STATE_BOUND:
+        default:
+                assert_not_reached();
+        }
+
+        client_set_state(client, state);
+
+        client->retransmit_time = 0;
+        client->retransmit_count = 0;
+        client->transaction_id = random_u32() & htobe32(0x00ffffff);
+
+        r = sd_event_now(client->event, CLOCK_BOOTTIME, &client->transaction_start);
+        if (r < 0)
+                goto error;
+
+        r = event_reset_time(client->event, &client->timeout_resend,
+                             CLOCK_BOOTTIME,
+                             0, 0,
+                             client_timeout_resend, client,
+                             client->event_priority, "dhcp6-resend-timeout", true);
+        if (r < 0)
+                goto error;
+
+        r = sd_event_source_set_enabled(client->receive_message, SD_EVENT_ON);
+        if (r < 0)
+                goto error;
+
+        return 0;
+
+error:
+        client_stop(client, r);
+        return r;
+}
+
+static int client_timeout_expire(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp6_client *client = ASSERT_PTR(userdata);
+        DHCP6_CLIENT_DONT_DESTROY(client);
+        DHCP6State state;
+
+        (void) event_source_disable(client->timeout_expire);
+        (void) event_source_disable(client->timeout_t2);
+        (void) event_source_disable(client->timeout_t1);
+
+        state = client->state;
+
+        client_stop(client, SD_DHCP6_CLIENT_EVENT_RESEND_EXPIRE);
+
+        /* RFC 3315, section 18.1.4., says that "...the client may choose to
+           use a Solicit message to locate a new DHCP server..." */
+        if (state == DHCP6_STATE_REBIND)
+                (void) client_start_transaction(client, DHCP6_STATE_SOLICITATION);
+
+        return 0;
+}
+
+static int client_timeout_t2(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp6_client *client = ASSERT_PTR(userdata);
+
+        (void) event_source_disable(client->timeout_t2);
+        (void) event_source_disable(client->timeout_t1);
+
+        log_dhcp6_client(client, "Timeout T2");
+
+        (void) client_start_transaction(client, DHCP6_STATE_REBIND);
+
+        return 0;
+}
+
+static int client_timeout_t1(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_dhcp6_client *client = ASSERT_PTR(userdata);
+
+        (void) event_source_disable(client->timeout_t1);
+
+        log_dhcp6_client(client, "Timeout T1");
+
+        (void) client_start_transaction(client, DHCP6_STATE_RENEW);
+
+        return 0;
+}
+
+static int client_enter_bound_state(sd_dhcp6_client *client) {
+        usec_t lifetime_t1, lifetime_t2, lifetime_valid;
+        int r;
+
+        assert(client);
+        assert(client->lease);
+        assert(IN_SET(client->state,
+                      DHCP6_STATE_SOLICITATION,
+                      DHCP6_STATE_REQUEST,
+                      DHCP6_STATE_RENEW,
+                      DHCP6_STATE_REBIND));
+
+        (void) event_source_disable(client->receive_message);
+        (void) event_source_disable(client->timeout_resend);
+
+        r = dhcp6_lease_get_lifetime(client->lease, &lifetime_t1, &lifetime_t2, &lifetime_valid);
+        if (r < 0)
+                goto error;
+
+        lifetime_t2 = client_timeout_compute_random(lifetime_t2);
+        lifetime_t1 = client_timeout_compute_random(MIN(lifetime_t1, lifetime_t2));
+
+        if (lifetime_t1 == USEC_INFINITY) {
+                log_dhcp6_client(client, "Infinite T1");
+                event_source_disable(client->timeout_t1);
+        } else {
+                log_dhcp6_client(client, "T1 expires in %s", FORMAT_TIMESPAN(lifetime_t1, USEC_PER_SEC));
+                r = event_reset_time_relative(client->event, &client->timeout_t1,
+                                              CLOCK_BOOTTIME,
+                                              lifetime_t1, 10 * USEC_PER_SEC,
+                                              client_timeout_t1, client,
+                                              client->event_priority, "dhcp6-t1-timeout", true);
+                if (r < 0)
+                        goto error;
+        }
+
+        if (lifetime_t2 == USEC_INFINITY) {
+                log_dhcp6_client(client, "Infinite T2");
+                event_source_disable(client->timeout_t2);
+        } else {
+                log_dhcp6_client(client, "T2 expires in %s", FORMAT_TIMESPAN(lifetime_t2, USEC_PER_SEC));
+                r = event_reset_time_relative(client->event, &client->timeout_t2,
+                                              CLOCK_BOOTTIME,
+                                              lifetime_t2, 10 * USEC_PER_SEC,
+                                              client_timeout_t2, client,
+                                              client->event_priority, "dhcp6-t2-timeout", true);
+                if (r < 0)
+                        goto error;
+        }
+
+        if (lifetime_valid == USEC_INFINITY) {
+                log_dhcp6_client(client, "Infinite valid lifetime");
+                event_source_disable(client->timeout_expire);
+        } else {
+                log_dhcp6_client(client, "Valid lifetime expires in %s", FORMAT_TIMESPAN(lifetime_valid, USEC_PER_SEC));
+
+                r = event_reset_time_relative(client->event, &client->timeout_expire,
+                                              CLOCK_BOOTTIME,
+                                              lifetime_valid, USEC_PER_SEC,
+                                              client_timeout_expire, client,
+                                              client->event_priority, "dhcp6-lease-expire", true);
+                if (r < 0)
+                        goto error;
+        }
+
+        client_set_state(client, DHCP6_STATE_BOUND);
+        client_notify(client, SD_DHCP6_CLIENT_EVENT_IP_ACQUIRE);
+        return 0;
+
+error:
+        client_stop(client, r);
+        return r;
+}
+
+static int log_invalid_message_type(sd_dhcp6_client *client, const DHCP6Message *message) {
+        const char *type_str;
+
+        assert(client);
+        assert(message);
+
+        type_str = dhcp6_message_type_to_string(message->type);
+        if (type_str)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received unexpected %s message, ignoring.", type_str);
+        else
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "Received unsupported message type %u, ignoring.", message->type);
+}
+
+static int client_process_information(
+                sd_dhcp6_client *client,
+                DHCP6Message *message,
+                size_t len,
+                const triple_timestamp *timestamp,
+                const struct in6_addr *server_address) {
+
+        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
+        int r;
+
+        assert(client);
+        assert(message);
+
+        if (message->type != DHCP6_MESSAGE_REPLY)
+                return log_invalid_message_type(client, message);
+
+        r = dhcp6_lease_new_from_message(client, message, len, timestamp, server_address, &lease);
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to process received reply message, ignoring: %m");
+
+        log_dhcp6_client(client, "Processed %s message", dhcp6_message_type_to_string(message->type));
+
+        sd_dhcp6_lease_unref(client->lease);
+        client->lease = TAKE_PTR(lease);
+
+        /* Do not call client_stop() here, as it frees the acquired lease. */
+        (void) event_source_disable(client->receive_message);
+        (void) event_source_disable(client->timeout_resend);
+        client_set_state(client, DHCP6_STATE_STOPPED);
+
+        client_notify(client, SD_DHCP6_CLIENT_EVENT_INFORMATION_REQUEST);
+        return 0;
+}
+
+static int client_process_reply(
+                sd_dhcp6_client *client,
+                DHCP6Message *message,
+                size_t len,
+                const triple_timestamp *timestamp,
+                const struct in6_addr *server_address) {
+
+        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
+        int r;
+
+        assert(client);
+        assert(message);
+
+        if (message->type != DHCP6_MESSAGE_REPLY)
+                return log_invalid_message_type(client, message);
+
+        r = dhcp6_lease_new_from_message(client, message, len, timestamp, server_address, &lease);
+        if (r == -EADDRNOTAVAIL) {
+
+                /* If NoBinding status code is received, we cannot request the address anymore.
+                 * Let's restart transaction from the beginning. */
+
+                if (client->state == DHCP6_STATE_REQUEST)
+                        /* The lease is not acquired yet, hence it is not necessary to notify the restart. */
+                        client_cleanup(client);
+                else
+                        /* We need to notify the previous lease was expired. */
+                        client_stop(client, SD_DHCP6_CLIENT_EVENT_RESEND_EXPIRE);
+
+                return client_start_transaction(client, DHCP6_STATE_SOLICITATION);
+        }
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to process received reply message, ignoring: %m");
+
+        log_dhcp6_client(client, "Processed %s message", dhcp6_message_type_to_string(message->type));
+
+        sd_dhcp6_lease_unref(client->lease);
+        client->lease = TAKE_PTR(lease);
+
+        return client_enter_bound_state(client);
+}
+
+static int client_process_advertise_or_rapid_commit_reply(
+                sd_dhcp6_client *client,
+                DHCP6Message *message,
+                size_t len,
+                const triple_timestamp *timestamp,
+                const struct in6_addr *server_address) {
+
+        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
+        uint8_t pref_advertise, pref_lease = 0;
+        int r;
+
+        assert(client);
+        assert(message);
+
+        if (!IN_SET(message->type, DHCP6_MESSAGE_ADVERTISE, DHCP6_MESSAGE_REPLY))
+                return log_invalid_message_type(client, message);
+
+        r = dhcp6_lease_new_from_message(client, message, len, timestamp, server_address, &lease);
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to process received %s message, ignoring: %m",
+                                              dhcp6_message_type_to_string(message->type));
+
+        if (message->type == DHCP6_MESSAGE_REPLY) {
+                bool rapid_commit;
+
+                if (!client->rapid_commit)
+                        return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                                      "Received unexpected reply message, even we sent a solicit message without the rapid commit option, ignoring.");
+
+                r = dhcp6_lease_get_rapid_commit(lease, &rapid_commit);
+                if (r < 0)
+                        return r;
+
+                if (!rapid_commit)
+                        return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                                      "Received reply message without rapid commit flag, ignoring.");
+
+                log_dhcp6_client(client, "Processed %s message", dhcp6_message_type_to_string(message->type));
+
+                sd_dhcp6_lease_unref(client->lease);
+                client->lease = TAKE_PTR(lease);
+
+                return client_enter_bound_state(client);
+        }
+
+        r = dhcp6_lease_get_preference(lease, &pref_advertise);
+        if (r < 0)
+                return r;
+
+        if (client->lease) {
+                r = dhcp6_lease_get_preference(client->lease, &pref_lease);
+                if (r < 0)
+                        return r;
+        }
+
+        log_dhcp6_client(client, "Processed %s message", dhcp6_message_type_to_string(message->type));
+
+        if (!client->lease || pref_advertise > pref_lease) {
+                /* If this is the first advertise message or has higher preference, then save the lease. */
+                sd_dhcp6_lease_unref(client->lease);
+                client->lease = TAKE_PTR(lease);
+        }
+
+        if (pref_advertise == 255 || client->retransmit_count > 1)
+                (void) client_start_transaction(client, DHCP6_STATE_REQUEST);
+
+        return 0;
+}
+
+static int client_receive_message(
+                sd_event_source *s,
+                int fd, uint32_t
+                revents,
+                void *userdata) {
+
+        sd_dhcp6_client *client = ASSERT_PTR(userdata);
+        DHCP6_CLIENT_DONT_DESTROY(client);
+        /* This needs to be initialized with zero. See #20741. */
+        CMSG_BUFFER_TYPE(CMSG_SPACE_TIMEVAL) control = {};
+        struct iovec iov;
+        union sockaddr_union sa = {};
+        struct msghdr msg = {
+                .msg_name = &sa.sa,
+                .msg_namelen = sizeof(sa),
+                .msg_iov = &iov,
+                .msg_iovlen = 1,
+                .msg_control = &control,
+                .msg_controllen = sizeof(control),
+        };
+        struct cmsghdr *cmsg;
+        triple_timestamp t = {};
+        _cleanup_free_ DHCP6Message *message = NULL;
+        struct in6_addr *server_address = NULL;
+        ssize_t buflen, len;
+
+        buflen = next_datagram_size_fd(fd);
+        if (buflen < 0) {
+                if (ERRNO_IS_TRANSIENT(buflen) || ERRNO_IS_DISCONNECT(buflen))
+                        return 0;
+
+                log_dhcp6_client_errno(client, buflen, "Failed to determine datagram size to read, ignoring: %m");
+                return 0;
+        }
+
+        message = malloc(buflen);
+        if (!message)
+                return -ENOMEM;
+
+        iov = IOVEC_MAKE(message, buflen);
+
+        len = recvmsg_safe(fd, &msg, MSG_DONTWAIT);
+        if (len < 0) {
+                if (ERRNO_IS_TRANSIENT(len) || ERRNO_IS_DISCONNECT(len))
+                        return 0;
+
+                log_dhcp6_client_errno(client, len, "Could not receive message from UDP socket, ignoring: %m");
+                return 0;
+        }
+        if ((size_t) len < sizeof(DHCP6Message)) {
+                log_dhcp6_client(client, "Too small to be DHCP6 message: ignoring");
+                return 0;
+        }
+
+        /* msg_namelen == 0 happens when running the test-suite over a socketpair */
+        if (msg.msg_namelen > 0) {
+                if (msg.msg_namelen != sizeof(struct sockaddr_in6) || sa.in6.sin6_family != AF_INET6) {
+                        log_dhcp6_client(client, "Received message from invalid source, ignoring.");
+                        return 0;
+                }
+
+                server_address = &sa.in6.sin6_addr;
+        }
+
+        CMSG_FOREACH(cmsg, &msg) {
+                if (cmsg->cmsg_level == SOL_SOCKET &&
+                    cmsg->cmsg_type == SO_TIMESTAMP &&
+                    cmsg->cmsg_len == CMSG_LEN(sizeof(struct timeval)))
+                        triple_timestamp_from_realtime(&t, timeval_load((struct timeval*) CMSG_DATA(cmsg)));
+        }
+
+        if (client->transaction_id != (message->transaction_id & htobe32(0x00ffffff)))
+                return 0;
+
+        switch (client->state) {
+        case DHCP6_STATE_INFORMATION_REQUEST:
+                if (client_process_information(client, message, len, &t, server_address) < 0)
+                        return 0;
+                break;
+
+        case DHCP6_STATE_SOLICITATION:
+                if (client_process_advertise_or_rapid_commit_reply(client, message, len, &t, server_address) < 0)
+                        return 0;
+                break;
+
+        case DHCP6_STATE_REQUEST:
+        case DHCP6_STATE_RENEW:
+        case DHCP6_STATE_REBIND:
+                if (client_process_reply(client, message, len, &t, server_address) < 0)
+                        return 0;
+                break;
+
+        case DHCP6_STATE_BOUND:
+        case DHCP6_STATE_STOPPED:
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+}
+
+int sd_dhcp6_client_stop(sd_dhcp6_client *client) {
+        if (!client)
+                return 0;
+
+        client_stop(client, SD_DHCP6_CLIENT_EVENT_STOP);
+
+        client->receive_message = sd_event_source_unref(client->receive_message);
+        client->fd = safe_close(client->fd);
+
+        return 0;
+}
+
+int sd_dhcp6_client_is_running(sd_dhcp6_client *client) {
+        assert_return(client, -EINVAL);
+
+        return client->state != DHCP6_STATE_STOPPED;
+}
+
+int sd_dhcp6_client_start(sd_dhcp6_client *client) {
+        DHCP6State state = DHCP6_STATE_SOLICITATION;
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(client->event, -EINVAL);
+        assert_return(client->ifindex > 0, -EINVAL);
+        assert_return(in6_addr_is_link_local(&client->local_address) > 0, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(client->information_request || client->request_ia != 0, -EINVAL);
+
+        /* Even if the client is in the STOPPED state, the lease acquired in the previous information
+         * request may be stored. */
+        client->lease = sd_dhcp6_lease_unref(client->lease);
+
+        r = client_ensure_iaid(client);
+        if (r < 0)
+                return r;
+
+        r = client_ensure_duid(client);
+        if (r < 0)
+                return r;
+
+        if (client->fd < 0) {
+                r = dhcp6_network_bind_udp_socket(client->ifindex, &client->local_address);
+                if (r < 0)
+                        return log_dhcp6_client_errno(client, r,
+                                                      "Failed to bind to UDP socket at address %s: %m",
+                                                      IN6_ADDR_TO_STRING(&client->local_address));
+
+                client->fd = r;
+        }
+
+        if (!client->receive_message) {
+                _cleanup_(sd_event_source_disable_unrefp) sd_event_source *s = NULL;
+
+                r = sd_event_add_io(client->event, &s, client->fd, EPOLLIN, client_receive_message, client);
+                if (r < 0)
+                        return r;
+
+                r = sd_event_source_set_priority(s, client->event_priority);
+                if (r < 0)
+                        return r;
+
+                r = sd_event_source_set_description(s, "dhcp6-receive-message");
+                if (r < 0)
+                        return r;
+
+                client->receive_message = TAKE_PTR(s);
+        }
+
+        if (client->information_request) {
+                usec_t t = now(CLOCK_MONOTONIC);
+
+                if (t < usec_add(client->information_request_time_usec, client->information_refresh_time_usec))
+                        return 0;
+
+                client->information_request_time_usec = t;
+                state = DHCP6_STATE_INFORMATION_REQUEST;
+        }
+
+        log_dhcp6_client(client, "Starting in %s mode",
+                         client->information_request ? "Information request" : "Solicit");
+
+        return client_start_transaction(client, state);
+}
+
+int sd_dhcp6_client_attach_event(sd_dhcp6_client *client, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!client->event, -EBUSY);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        if (event)
+                client->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&client->event);
+                if (r < 0)
+                        return 0;
+        }
+
+        client->event_priority = priority;
+
+        return 0;
+}
+
+int sd_dhcp6_client_detach_event(sd_dhcp6_client *client) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        client->event = sd_event_unref(client->event);
+
+        return 0;
+}
+
+sd_event *sd_dhcp6_client_get_event(sd_dhcp6_client *client) {
+        assert_return(client, NULL);
+
+        return client->event;
+}
+
+static sd_dhcp6_client *dhcp6_client_free(sd_dhcp6_client *client) {
+        if (!client)
+                return NULL;
+
+        sd_dhcp6_lease_unref(client->lease);
+
+        sd_event_source_disable_unref(client->receive_message);
+        sd_event_source_disable_unref(client->timeout_resend);
+        sd_event_source_disable_unref(client->timeout_expire);
+        sd_event_source_disable_unref(client->timeout_t1);
+        sd_event_source_disable_unref(client->timeout_t2);
+        sd_event_unref(client->event);
+
+        client->fd = safe_close(client->fd);
+
+        free(client->req_opts);
+        free(client->fqdn);
+        free(client->mudurl);
+        dhcp6_ia_clear_addresses(&client->ia_pd);
+        ordered_hashmap_free(client->extra_options);
+        ordered_set_free(client->vendor_options);
+        strv_free(client->user_class);
+        strv_free(client->vendor_class);
+        free(client->ifname);
+
+        return mfree(client);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp6_client, sd_dhcp6_client, dhcp6_client_free);
+
+int sd_dhcp6_client_new(sd_dhcp6_client **ret) {
+        _cleanup_(sd_dhcp6_client_unrefp) sd_dhcp6_client *client = NULL;
+
+        assert_return(ret, -EINVAL);
+
+        client = new(sd_dhcp6_client, 1);
+        if (!client)
+                return -ENOMEM;
+
+        *client = (sd_dhcp6_client) {
+                .n_ref = 1,
+                .ia_na.type = SD_DHCP6_OPTION_IA_NA,
+                .ia_pd.type = SD_DHCP6_OPTION_IA_PD,
+                .ifindex = -1,
+                .request_ia = DHCP6_REQUEST_IA_NA | DHCP6_REQUEST_IA_PD,
+                .fd = -1,
+                .rapid_commit = true,
+        };
+
+        *ret = TAKE_PTR(client);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-dhcp6-lease.c b/src/libsystemd-network/sd-dhcp6-lease.c
new file mode 100644
index 0000000..973af10
--- /dev/null
+++ b/src/libsystemd-network/sd-dhcp6-lease.c
@@ -0,0 +1,731 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014-2015 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+
+#include "alloc-util.h"
+#include "dhcp6-internal.h"
+#include "dhcp6-lease-internal.h"
+#include "strv.h"
+
+#define IRT_DEFAULT (1 * USEC_PER_DAY)
+#define IRT_MINIMUM (600 * USEC_PER_SEC)
+
+static void dhcp6_lease_set_timestamp(sd_dhcp6_lease *lease, const triple_timestamp *timestamp) {
+        assert(lease);
+
+        if (timestamp && triple_timestamp_is_set(timestamp))
+                lease->timestamp = *timestamp;
+        else
+                triple_timestamp_get(&lease->timestamp);
+}
+
+int sd_dhcp6_lease_get_timestamp(sd_dhcp6_lease *lease, clockid_t clock, uint64_t *ret) {
+        assert_return(lease, -EINVAL);
+        assert_return(TRIPLE_TIMESTAMP_HAS_CLOCK(clock), -EOPNOTSUPP);
+        assert_return(clock_supported(clock), -EOPNOTSUPP);
+        assert_return(ret, -EINVAL);
+
+        if (!triple_timestamp_is_set(&lease->timestamp))
+                return -ENODATA;
+
+        *ret = triple_timestamp_by_clock(&lease->timestamp, clock);
+        return 0;
+}
+
+static usec_t sec2usec(uint32_t sec) {
+        return sec == UINT32_MAX ? USEC_INFINITY : sec * USEC_PER_SEC;
+}
+
+static void dhcp6_lease_set_lifetime(sd_dhcp6_lease *lease) {
+        uint32_t t1 = UINT32_MAX, t2 = UINT32_MAX, min_valid_lt = UINT32_MAX;
+
+        assert(lease);
+        assert(lease->ia_na || lease->ia_pd);
+
+        if (lease->ia_na) {
+                t1 = MIN(t1, be32toh(lease->ia_na->header.lifetime_t1));
+                t2 = MIN(t2, be32toh(lease->ia_na->header.lifetime_t2));
+
+                LIST_FOREACH(addresses, a, lease->ia_na->addresses)
+                        min_valid_lt = MIN(min_valid_lt, be32toh(a->iaaddr.lifetime_valid));
+        }
+
+        if (lease->ia_pd) {
+                t1 = MIN(t1, be32toh(lease->ia_pd->header.lifetime_t1));
+                t2 = MIN(t2, be32toh(lease->ia_pd->header.lifetime_t2));
+
+                LIST_FOREACH(addresses, a, lease->ia_pd->addresses)
+                        min_valid_lt = MIN(min_valid_lt, be32toh(a->iapdprefix.lifetime_valid));
+        }
+
+        if (t2 == 0 || t2 > min_valid_lt) {
+                /* If T2 is zero or longer than the minimum valid lifetime of the addresses or prefixes,
+                 * then adjust lifetime with it. */
+                t1 = min_valid_lt / 2;
+                t2 = min_valid_lt / 10 * 8;
+        }
+
+        lease->lifetime_valid = sec2usec(min_valid_lt);
+        lease->lifetime_t1 = sec2usec(t1);
+        lease->lifetime_t2 = sec2usec(t2);
+}
+
+int dhcp6_lease_get_lifetime(sd_dhcp6_lease *lease, usec_t *ret_t1, usec_t *ret_t2, usec_t *ret_valid) {
+        assert(lease);
+
+        if (!lease->ia_na && !lease->ia_pd)
+                return -ENODATA;
+
+        if (ret_t1)
+                *ret_t1 = lease->lifetime_t1;
+        if (ret_t2)
+                *ret_t2 = lease->lifetime_t2;
+        if (ret_valid)
+                *ret_valid = lease->lifetime_valid;
+        return 0;
+}
+
+static void dhcp6_lease_set_server_address(sd_dhcp6_lease *lease, const struct in6_addr *server_address) {
+        assert(lease);
+
+        if (server_address)
+                lease->server_address = *server_address;
+        else
+                lease->server_address = (struct in6_addr) {};
+}
+
+int sd_dhcp6_lease_get_server_address(sd_dhcp6_lease *lease, struct in6_addr *ret) {
+        assert_return(lease, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        *ret = lease->server_address;
+        return 0;
+}
+
+void dhcp6_ia_clear_addresses(DHCP6IA *ia) {
+        assert(ia);
+
+        LIST_FOREACH(addresses, a, ia->addresses)
+                free(a);
+
+        ia->addresses = NULL;
+}
+
+DHCP6IA *dhcp6_ia_free(DHCP6IA *ia) {
+        if (!ia)
+                return NULL;
+
+        dhcp6_ia_clear_addresses(ia);
+
+        return mfree(ia);
+}
+
+int dhcp6_lease_set_clientid(sd_dhcp6_lease *lease, const uint8_t *id, size_t len) {
+        uint8_t *clientid = NULL;
+
+        assert(lease);
+        assert(id || len == 0);
+
+        if (len > 0) {
+                clientid = memdup(id, len);
+                if (!clientid)
+                        return -ENOMEM;
+        }
+
+        free_and_replace(lease->clientid, clientid);
+        lease->clientid_len = len;
+
+        return 0;
+}
+
+int dhcp6_lease_get_clientid(sd_dhcp6_lease *lease, uint8_t **ret_id, size_t *ret_len) {
+        assert(lease);
+
+        if (!lease->clientid)
+                return -ENODATA;
+
+        if (ret_id)
+                *ret_id = lease->clientid;
+        if (ret_len)
+                *ret_len = lease->clientid_len;
+
+        return 0;
+}
+
+int dhcp6_lease_set_serverid(sd_dhcp6_lease *lease, const uint8_t *id, size_t len) {
+        uint8_t *serverid = NULL;
+
+        assert(lease);
+        assert(id || len == 0);
+
+        if (len > 0) {
+                serverid = memdup(id, len);
+                if (!serverid)
+                        return -ENOMEM;
+        }
+
+        free_and_replace(lease->serverid, serverid);
+        lease->serverid_len = len;
+
+        return 0;
+}
+
+int dhcp6_lease_get_serverid(sd_dhcp6_lease *lease, uint8_t **ret_id, size_t *ret_len) {
+        assert(lease);
+
+        if (!lease->serverid)
+                return -ENODATA;
+
+        if (ret_id)
+                *ret_id = lease->serverid;
+        if (ret_len)
+                *ret_len = lease->serverid_len;
+        return 0;
+}
+
+int dhcp6_lease_set_preference(sd_dhcp6_lease *lease, uint8_t preference) {
+        assert(lease);
+
+        lease->preference = preference;
+        return 0;
+}
+
+int dhcp6_lease_get_preference(sd_dhcp6_lease *lease, uint8_t *ret) {
+        assert(lease);
+        assert(ret);
+
+        *ret = lease->preference;
+        return 0;
+}
+
+int dhcp6_lease_set_rapid_commit(sd_dhcp6_lease *lease) {
+        assert(lease);
+
+        lease->rapid_commit = true;
+        return 0;
+}
+
+int dhcp6_lease_get_rapid_commit(sd_dhcp6_lease *lease, bool *ret) {
+        assert(lease);
+        assert(ret);
+
+        *ret = lease->rapid_commit;
+        return 0;
+}
+
+int sd_dhcp6_lease_get_address(
+                sd_dhcp6_lease *lease,
+                struct in6_addr *ret_addr,
+                uint32_t *ret_lifetime_preferred,
+                uint32_t *ret_lifetime_valid) {
+
+        assert_return(lease, -EINVAL);
+
+        if (!lease->addr_iter)
+                return -ENODATA;
+
+        if (ret_addr)
+                *ret_addr = lease->addr_iter->iaaddr.address;
+        if (ret_lifetime_preferred)
+                *ret_lifetime_preferred = be32toh(lease->addr_iter->iaaddr.lifetime_preferred);
+        if (ret_lifetime_valid)
+                *ret_lifetime_valid = be32toh(lease->addr_iter->iaaddr.lifetime_valid);
+
+        lease->addr_iter = lease->addr_iter->addresses_next;
+        return 0;
+}
+
+void sd_dhcp6_lease_reset_address_iter(sd_dhcp6_lease *lease) {
+        if (lease)
+                lease->addr_iter = lease->ia_na ? lease->ia_na->addresses : NULL;
+}
+
+int sd_dhcp6_lease_get_pd(
+                sd_dhcp6_lease *lease,
+                struct in6_addr *ret_prefix,
+                uint8_t *ret_prefix_len,
+                uint32_t *ret_lifetime_preferred,
+                uint32_t *ret_lifetime_valid) {
+
+        assert_return(lease, -EINVAL);
+
+        if (!lease->prefix_iter)
+                return -ENODATA;
+
+        if (ret_prefix)
+                *ret_prefix = lease->prefix_iter->iapdprefix.address;
+        if (ret_prefix_len)
+                *ret_prefix_len = lease->prefix_iter->iapdprefix.prefixlen;
+        if (ret_lifetime_preferred)
+                *ret_lifetime_preferred = be32toh(lease->prefix_iter->iapdprefix.lifetime_preferred);
+        if (ret_lifetime_valid)
+                *ret_lifetime_valid = be32toh(lease->prefix_iter->iapdprefix.lifetime_valid);
+
+        lease->prefix_iter = lease->prefix_iter->addresses_next;
+        return 0;
+}
+
+void sd_dhcp6_lease_reset_pd_prefix_iter(sd_dhcp6_lease *lease) {
+        if (lease)
+                lease->prefix_iter = lease->ia_pd ? lease->ia_pd->addresses : NULL;
+}
+
+int dhcp6_lease_add_dns(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen) {
+        assert(lease);
+        assert(optval || optlen == 0);
+
+        if (optlen == 0)
+                return 0;
+
+        return dhcp6_option_parse_addresses(optval, optlen, &lease->dns, &lease->dns_count);
+}
+
+int sd_dhcp6_lease_get_dns(sd_dhcp6_lease *lease, const struct in6_addr **ret) {
+        assert_return(lease, -EINVAL);
+
+        if (!lease->dns)
+                return -ENODATA;
+
+        if (ret)
+                *ret = lease->dns;
+
+        return lease->dns_count;
+}
+
+int dhcp6_lease_add_domains(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen) {
+        _cleanup_strv_free_ char **domains = NULL;
+        int r;
+
+        assert(lease);
+        assert(optval || optlen == 0);
+
+        if (optlen == 0)
+                return 0;
+
+        r = dhcp6_option_parse_domainname_list(optval, optlen, &domains);
+        if (r < 0)
+                return r;
+
+        return strv_extend_strv(&lease->domains, domains, true);
+}
+
+int sd_dhcp6_lease_get_domains(sd_dhcp6_lease *lease, char ***ret) {
+        assert_return(lease, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!lease->domains)
+                return -ENODATA;
+
+        *ret = lease->domains;
+        return strv_length(lease->domains);
+}
+
+int dhcp6_lease_add_ntp(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen) {
+        int r;
+
+        assert(lease);
+        assert(optval || optlen == 0);
+
+        for (size_t offset = 0; offset < optlen;) {
+                const uint8_t *subval;
+                size_t sublen;
+                uint16_t subopt;
+
+                r = dhcp6_option_parse(optval, optlen, &offset, &subopt, &sublen, &subval);
+                if (r < 0)
+                        return r;
+
+                switch (subopt) {
+                case DHCP6_NTP_SUBOPTION_SRV_ADDR:
+                case DHCP6_NTP_SUBOPTION_MC_ADDR:
+                        if (sublen != 16)
+                                return -EINVAL;
+
+                        r = dhcp6_option_parse_addresses(subval, sublen, &lease->ntp, &lease->ntp_count);
+                        if (r < 0)
+                                return r;
+
+                        break;
+
+                case DHCP6_NTP_SUBOPTION_SRV_FQDN: {
+                        _cleanup_free_ char *server = NULL;
+
+                        r = dhcp6_option_parse_domainname(subval, sublen, &server);
+                        if (r < 0)
+                                return r;
+
+                        if (strv_contains(lease->ntp_fqdn, server))
+                                continue;
+
+                        r = strv_consume(&lease->ntp_fqdn, TAKE_PTR(server));
+                        if (r < 0)
+                                return r;
+
+                        break;
+                }}
+        }
+
+        return 0;
+}
+
+int dhcp6_lease_add_sntp(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen) {
+        assert(lease);
+        assert(optval || optlen == 0);
+
+        if (optlen == 0)
+                return 0;
+
+        /* SNTP option is defined in RFC4075, and deprecated by RFC5908. */
+        return dhcp6_option_parse_addresses(optval, optlen, &lease->sntp, &lease->sntp_count);
+}
+
+int sd_dhcp6_lease_get_ntp_addrs(sd_dhcp6_lease *lease, const struct in6_addr **ret) {
+        assert_return(lease, -EINVAL);
+
+        if (lease->ntp) {
+                if (ret)
+                        *ret = lease->ntp;
+                return lease->ntp_count;
+        }
+
+        if (lease->sntp && !lease->ntp_fqdn) {
+                /* Fallback to the deprecated SNTP option. */
+                if (ret)
+                        *ret = lease->sntp;
+                return lease->sntp_count;
+        }
+
+        return -ENODATA;
+}
+
+int sd_dhcp6_lease_get_ntp_fqdn(sd_dhcp6_lease *lease, char ***ret) {
+        assert_return(lease, -EINVAL);
+
+        if (!lease->ntp_fqdn)
+                return -ENODATA;
+
+        if (ret)
+                *ret = lease->ntp_fqdn;
+        return strv_length(lease->ntp_fqdn);
+}
+
+int dhcp6_lease_set_fqdn(sd_dhcp6_lease *lease, const uint8_t *optval, size_t optlen) {
+        char *fqdn;
+        int r;
+
+        assert(lease);
+        assert(optval || optlen == 0);
+
+        if (optlen == 0)
+                return 0;
+
+        if (optlen < 2)
+                return -ENODATA;
+
+        /* Ignore the flags field, it doesn't carry any useful
+           information for clients. */
+        r = dhcp6_option_parse_domainname(optval + 1, optlen - 1, &fqdn);
+        if (r < 0)
+                return r;
+
+        return free_and_replace(lease->fqdn, fqdn);
+}
+
+int sd_dhcp6_lease_get_fqdn(sd_dhcp6_lease *lease, const char **ret) {
+        assert_return(lease, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (!lease->fqdn)
+                return -ENODATA;
+
+        *ret = lease->fqdn;
+        return 0;
+}
+
+static int dhcp6_lease_parse_message(
+                sd_dhcp6_client *client,
+                sd_dhcp6_lease *lease,
+                const DHCP6Message *message,
+                size_t len) {
+
+        usec_t irt = IRT_DEFAULT;
+        int r;
+
+        assert(client);
+        assert(lease);
+        assert(message);
+        assert(len >= sizeof(DHCP6Message));
+
+        len -= sizeof(DHCP6Message);
+        for (size_t offset = 0; offset < len;) {
+                uint16_t optcode;
+                size_t optlen;
+                const uint8_t *optval;
+
+                if (len - offset < offsetof(DHCP6Option, data)) {
+                        log_dhcp6_client(client, "Ignoring %zu invalid byte(s) at the end of the packet", len - offset);
+                        break;
+                }
+
+                r = dhcp6_option_parse(message->options, len, &offset, &optcode, &optlen, &optval);
+                if (r < 0)
+                        return log_dhcp6_client_errno(client, r,
+                                                      "Failed to parse option header at offset %zu of total length %zu: %m",
+                                                      offset, len);
+
+                switch (optcode) {
+                case SD_DHCP6_OPTION_CLIENTID:
+                        if (dhcp6_lease_get_clientid(lease, NULL, NULL) >= 0)
+                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL), "%s contains multiple client IDs",
+                                                              dhcp6_message_type_to_string(message->type));
+
+                        r = dhcp6_lease_set_clientid(lease, optval, optlen);
+                        if (r < 0)
+                                return log_dhcp6_client_errno(client, r, "Failed to set client ID: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_SERVERID:
+                        if (dhcp6_lease_get_serverid(lease, NULL, NULL) >= 0)
+                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL), "%s contains multiple server IDs",
+                                                              dhcp6_message_type_to_string(message->type));
+
+                        r = dhcp6_lease_set_serverid(lease, optval, optlen);
+                        if (r < 0)
+                                return log_dhcp6_client_errno(client, r, "Failed to set server ID: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_PREFERENCE:
+                        if (optlen != 1)
+                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL), "Received invalid length for preference.");
+
+                        r = dhcp6_lease_set_preference(lease, optval[0]);
+                        if (r < 0)
+                                return log_dhcp6_client_errno(client, r, "Failed to set preference: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_STATUS_CODE: {
+                        _cleanup_free_ char *msg = NULL;
+
+                        r = dhcp6_option_parse_status(optval, optlen, &msg);
+                        if (r < 0)
+                                return log_dhcp6_client_errno(client, r, "Failed to parse status code: %m");
+
+                        if (r > 0)
+                                return log_dhcp6_client_errno(client, dhcp6_message_status_to_errno(r),
+                                                              "Received %s message with non-zero status: %s%s%s",
+                                                              dhcp6_message_type_to_string(message->type),
+                                                              strempty(msg), isempty(msg) ? "" : ": ",
+                                                              dhcp6_message_status_to_string(r));
+                        break;
+                }
+                case SD_DHCP6_OPTION_IA_NA: {
+                        _cleanup_(dhcp6_ia_freep) DHCP6IA *ia = NULL;
+
+                        if (client->state == DHCP6_STATE_INFORMATION_REQUEST) {
+                                log_dhcp6_client(client, "Ignoring IA NA option in information requesting mode.");
+                                break;
+                        }
+
+                        r = dhcp6_option_parse_ia(client, client->ia_na.header.id, optcode, optlen, optval, &ia);
+                        if (r == -ENOMEM)
+                                return log_oom_debug();
+                        if (r < 0) {
+                                log_dhcp6_client_errno(client, r, "Failed to parse IA_NA option, ignoring: %m");
+                                continue;
+                        }
+
+                        if (lease->ia_na) {
+                                log_dhcp6_client(client, "Received duplicate matching IA_NA option, ignoring.");
+                                continue;
+                        }
+
+                        dhcp6_ia_free(lease->ia_na);
+                        lease->ia_na = TAKE_PTR(ia);
+                        break;
+                }
+                case SD_DHCP6_OPTION_IA_PD: {
+                        _cleanup_(dhcp6_ia_freep) DHCP6IA *ia = NULL;
+
+                        if (client->state == DHCP6_STATE_INFORMATION_REQUEST) {
+                                log_dhcp6_client(client, "Ignoring IA PD option in information requesting mode.");
+                                break;
+                        }
+
+                        r = dhcp6_option_parse_ia(client, client->ia_pd.header.id, optcode, optlen, optval, &ia);
+                        if (r == -ENOMEM)
+                                return log_oom_debug();
+                        if (r < 0) {
+                                log_dhcp6_client_errno(client, r, "Failed to parse IA_PD option, ignoring: %m");
+                                continue;
+                        }
+
+                        if (lease->ia_pd) {
+                                log_dhcp6_client(client, "Received duplicate matching IA_PD option, ignoring.");
+                                continue;
+                        }
+
+                        dhcp6_ia_free(lease->ia_pd);
+                        lease->ia_pd = TAKE_PTR(ia);
+                        break;
+                }
+                case SD_DHCP6_OPTION_RAPID_COMMIT:
+                        if (optlen != 0)
+                                log_dhcp6_client(client, "Received rapid commit option with an invalid length (%zu), ignoring.", optlen);
+
+                        r = dhcp6_lease_set_rapid_commit(lease);
+                        if (r < 0)
+                                return log_dhcp6_client_errno(client, r, "Failed to set rapid commit flag: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_DNS_SERVER:
+                        r = dhcp6_lease_add_dns(lease, optval, optlen);
+                        if (r < 0)
+                                log_dhcp6_client_errno(client, r, "Failed to parse DNS server option, ignoring: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_DOMAIN:
+                        r = dhcp6_lease_add_domains(lease, optval, optlen);
+                        if (r < 0)
+                                log_dhcp6_client_errno(client, r, "Failed to parse domain list option, ignoring: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_NTP_SERVER:
+                        r = dhcp6_lease_add_ntp(lease, optval, optlen);
+                        if (r < 0)
+                                log_dhcp6_client_errno(client, r, "Failed to parse NTP server option, ignoring: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_SNTP_SERVER:
+                        r = dhcp6_lease_add_sntp(lease, optval, optlen);
+                        if (r < 0)
+                                log_dhcp6_client_errno(client, r, "Failed to parse SNTP server option, ignoring: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_CLIENT_FQDN:
+                        r = dhcp6_lease_set_fqdn(lease, optval, optlen);
+                        if (r < 0)
+                                log_dhcp6_client_errno(client, r, "Failed to parse FQDN option, ignoring: %m");
+
+                        break;
+
+                case SD_DHCP6_OPTION_INFORMATION_REFRESH_TIME:
+                        if (optlen != 4)
+                                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                                              "Received information refresh time option with an invalid length (%zu).", optlen);
+
+                        irt = unaligned_read_be32((be32_t *) optval) * USEC_PER_SEC;
+                        break;
+                }
+        }
+
+        uint8_t *clientid;
+        size_t clientid_len;
+        if (dhcp6_lease_get_clientid(lease, &clientid, &clientid_len) < 0)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "%s message does not contain client ID. Ignoring.",
+                                              dhcp6_message_type_to_string(message->type));
+
+        if (memcmp_nn(clientid, clientid_len, &client->duid, client->duid_len) != 0)
+                return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                              "The client ID in %s message does not match. Ignoring.",
+                                              dhcp6_message_type_to_string(message->type));
+
+        if (client->state == DHCP6_STATE_INFORMATION_REQUEST) {
+                client->information_refresh_time_usec = MAX(irt, IRT_MINIMUM);
+                log_dhcp6_client(client, "New information request will be refused in %s.",
+                                 FORMAT_TIMESPAN(client->information_refresh_time_usec, USEC_PER_SEC));
+
+        } else {
+                r = dhcp6_lease_get_serverid(lease, NULL, NULL);
+                if (r < 0)
+                        return log_dhcp6_client_errno(client, r, "%s has no server id",
+                                                      dhcp6_message_type_to_string(message->type));
+
+                if (!lease->ia_na && !lease->ia_pd)
+                        return log_dhcp6_client_errno(client, SYNTHETIC_ERRNO(EINVAL),
+                                                      "No IA_PD prefix or IA_NA address received. Ignoring.");
+
+                dhcp6_lease_set_lifetime(lease);
+        }
+
+        return 0;
+}
+
+static sd_dhcp6_lease *dhcp6_lease_free(sd_dhcp6_lease *lease) {
+        if (!lease)
+                return NULL;
+
+        free(lease->clientid);
+        free(lease->serverid);
+        dhcp6_ia_free(lease->ia_na);
+        dhcp6_ia_free(lease->ia_pd);
+        free(lease->dns);
+        free(lease->fqdn);
+        strv_free(lease->domains);
+        free(lease->ntp);
+        strv_free(lease->ntp_fqdn);
+        free(lease->sntp);
+
+        return mfree(lease);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_dhcp6_lease, sd_dhcp6_lease, dhcp6_lease_free);
+
+int dhcp6_lease_new(sd_dhcp6_lease **ret) {
+        sd_dhcp6_lease *lease;
+
+        assert(ret);
+
+        lease = new(sd_dhcp6_lease, 1);
+        if (!lease)
+                return -ENOMEM;
+
+        *lease = (sd_dhcp6_lease) {
+                .n_ref = 1,
+        };
+
+        *ret = lease;
+        return 0;
+}
+
+int dhcp6_lease_new_from_message(
+                sd_dhcp6_client *client,
+                const DHCP6Message *message,
+                size_t len,
+                const triple_timestamp *timestamp,
+                const struct in6_addr *server_address,
+                sd_dhcp6_lease **ret) {
+
+        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
+        int r;
+
+        assert(client);
+        assert(message);
+        assert(len >= sizeof(DHCP6Message));
+        assert(ret);
+
+        r = dhcp6_lease_new(&lease);
+        if (r < 0)
+                return r;
+
+        dhcp6_lease_set_timestamp(lease, timestamp);
+        dhcp6_lease_set_server_address(lease, server_address);
+
+        r = dhcp6_lease_parse_message(client, lease, message, len);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(lease);
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-ipv4acd.c b/src/libsystemd-network/sd-ipv4acd.c
new file mode 100644
index 0000000..9b11b2f
--- /dev/null
+++ b/src/libsystemd-network/sd-ipv4acd.c
@@ -0,0 +1,611 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Axis Communications AB. All rights reserved.
+***/
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <netinet/if_ether.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "sd-ipv4acd.h"
+
+#include "alloc-util.h"
+#include "arp-util.h"
+#include "ether-addr-util.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "in-addr-util.h"
+#include "memory-util.h"
+#include "network-common.h"
+#include "random-util.h"
+#include "siphash24.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "time-util.h"
+
+/* Constants from the RFC */
+#define PROBE_WAIT_USEC (1U * USEC_PER_SEC)
+#define PROBE_NUM 3U
+#define PROBE_MIN_USEC (1U * USEC_PER_SEC)
+#define PROBE_MAX_USEC (2U * USEC_PER_SEC)
+#define ANNOUNCE_WAIT_USEC (2U * USEC_PER_SEC)
+#define ANNOUNCE_NUM 2U
+#define ANNOUNCE_INTERVAL_USEC (2U * USEC_PER_SEC)
+#define MAX_CONFLICTS 10U
+#define RATE_LIMIT_INTERVAL_USEC (60U * USEC_PER_SEC)
+#define DEFEND_INTERVAL_USEC (10U * USEC_PER_SEC)
+
+typedef enum IPv4ACDState {
+        IPV4ACD_STATE_INIT,
+        IPV4ACD_STATE_STARTED,
+        IPV4ACD_STATE_WAITING_PROBE,
+        IPV4ACD_STATE_PROBING,
+        IPV4ACD_STATE_WAITING_ANNOUNCE,
+        IPV4ACD_STATE_ANNOUNCING,
+        IPV4ACD_STATE_RUNNING,
+        _IPV4ACD_STATE_MAX,
+        _IPV4ACD_STATE_INVALID = -EINVAL,
+} IPv4ACDState;
+
+struct sd_ipv4acd {
+        unsigned n_ref;
+
+        IPv4ACDState state;
+        int ifindex;
+        int fd;
+
+        char *ifname;
+        unsigned n_iteration;
+        unsigned n_conflict;
+
+        sd_event_source *receive_message_event_source;
+        sd_event_source *timer_event_source;
+
+        usec_t defend_window;
+        struct in_addr address;
+
+        /* External */
+        struct ether_addr mac_addr;
+
+        sd_event *event;
+        int event_priority;
+        sd_ipv4acd_callback_t callback;
+        void *userdata;
+        sd_ipv4acd_check_mac_callback_t check_mac_callback;
+        void *check_mac_userdata;
+};
+
+#define log_ipv4acd_errno(acd, error, fmt, ...)         \
+        log_interface_prefix_full_errno(                \
+                "IPv4ACD: ",                            \
+                sd_ipv4acd, acd,                        \
+                error, fmt, ##__VA_ARGS__)
+#define log_ipv4acd(acd, fmt, ...)                      \
+        log_interface_prefix_full_errno_zerook(         \
+                "IPv4ACD: ",                            \
+                sd_ipv4acd, acd,                        \
+                0, fmt, ##__VA_ARGS__)
+
+static const char * const ipv4acd_state_table[_IPV4ACD_STATE_MAX] = {
+        [IPV4ACD_STATE_INIT]             = "init",
+        [IPV4ACD_STATE_STARTED]          = "started",
+        [IPV4ACD_STATE_WAITING_PROBE]    = "waiting-probe",
+        [IPV4ACD_STATE_PROBING]          = "probing",
+        [IPV4ACD_STATE_WAITING_ANNOUNCE] = "waiting-announce",
+        [IPV4ACD_STATE_ANNOUNCING]       = "announcing",
+        [IPV4ACD_STATE_RUNNING]          = "running",
+};
+
+DEFINE_PRIVATE_STRING_TABLE_LOOKUP_TO_STRING(ipv4acd_state, IPv4ACDState);
+
+static void ipv4acd_set_state(sd_ipv4acd *acd, IPv4ACDState st, bool reset_counter) {
+        assert(acd);
+        assert(st < _IPV4ACD_STATE_MAX);
+
+        if (st != acd->state)
+                log_ipv4acd(acd, "%s -> %s", ipv4acd_state_to_string(acd->state), ipv4acd_state_to_string(st));
+
+        if (st == acd->state && !reset_counter)
+                acd->n_iteration++;
+        else {
+                acd->state = st;
+                acd->n_iteration = 0;
+        }
+}
+
+static void ipv4acd_reset(sd_ipv4acd *acd) {
+        assert(acd);
+
+        (void) event_source_disable(acd->timer_event_source);
+        acd->receive_message_event_source = sd_event_source_disable_unref(acd->receive_message_event_source);
+
+        acd->fd = safe_close(acd->fd);
+
+        ipv4acd_set_state(acd, IPV4ACD_STATE_INIT, true);
+}
+
+static sd_ipv4acd *ipv4acd_free(sd_ipv4acd *acd) {
+        assert(acd);
+
+        ipv4acd_reset(acd);
+        sd_event_source_unref(acd->timer_event_source);
+        sd_ipv4acd_detach_event(acd);
+        free(acd->ifname);
+        return mfree(acd);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_ipv4acd, sd_ipv4acd, ipv4acd_free);
+
+int sd_ipv4acd_new(sd_ipv4acd **ret) {
+        _cleanup_(sd_ipv4acd_unrefp) sd_ipv4acd *acd = NULL;
+
+        assert_return(ret, -EINVAL);
+
+        acd = new(sd_ipv4acd, 1);
+        if (!acd)
+                return -ENOMEM;
+
+        *acd = (sd_ipv4acd) {
+                .n_ref = 1,
+                .state = IPV4ACD_STATE_INIT,
+                .ifindex = -1,
+                .fd = -1,
+        };
+
+        *ret = TAKE_PTR(acd);
+
+        return 0;
+}
+
+static void ipv4acd_client_notify(sd_ipv4acd *acd, int event) {
+        assert(acd);
+
+        if (!acd->callback)
+                return;
+
+        acd->callback(acd, event, acd->userdata);
+}
+
+int sd_ipv4acd_stop(sd_ipv4acd *acd) {
+        IPv4ACDState old_state;
+
+        if (!acd)
+                return 0;
+
+        old_state = acd->state;
+
+        ipv4acd_reset(acd);
+
+        if (old_state == IPV4ACD_STATE_INIT)
+                return 0;
+
+        log_ipv4acd(acd, "STOPPED");
+
+        ipv4acd_client_notify(acd, SD_IPV4ACD_EVENT_STOP);
+
+        return 0;
+}
+
+static int ipv4acd_on_timeout(sd_event_source *s, uint64_t usec, void *userdata);
+
+static int ipv4acd_set_next_wakeup(sd_ipv4acd *acd, usec_t usec, usec_t random_usec) {
+        usec_t next_timeout, time_now;
+
+        assert(acd);
+
+        next_timeout = usec;
+
+        if (random_usec > 0)
+                next_timeout += (usec_t) random_u64() % random_usec;
+
+        assert_se(sd_event_now(acd->event, CLOCK_BOOTTIME, &time_now) >= 0);
+
+        return event_reset_time(acd->event, &acd->timer_event_source,
+                                CLOCK_BOOTTIME,
+                                time_now + next_timeout, 0,
+                                ipv4acd_on_timeout, acd,
+                                acd->event_priority, "ipv4acd-timer", true);
+}
+
+static int ipv4acd_on_timeout(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_ipv4acd *acd = ASSERT_PTR(userdata);
+        int r = 0;
+
+        switch (acd->state) {
+
+        case IPV4ACD_STATE_STARTED:
+                acd->defend_window = 0;
+
+                ipv4acd_set_state(acd, IPV4ACD_STATE_WAITING_PROBE, true);
+
+                if (acd->n_conflict >= MAX_CONFLICTS) {
+                        log_ipv4acd(acd, "Max conflicts reached, delaying by %s",
+                                    FORMAT_TIMESPAN(RATE_LIMIT_INTERVAL_USEC, 0));
+                        r = ipv4acd_set_next_wakeup(acd, RATE_LIMIT_INTERVAL_USEC, PROBE_WAIT_USEC);
+                } else
+                        r = ipv4acd_set_next_wakeup(acd, 0, PROBE_WAIT_USEC);
+                if (r < 0)
+                        goto fail;
+
+                break;
+
+        case IPV4ACD_STATE_WAITING_PROBE:
+        case IPV4ACD_STATE_PROBING:
+                /* Send a probe */
+                r = arp_send_probe(acd->fd, acd->ifindex, &acd->address, &acd->mac_addr);
+                if (r < 0) {
+                        log_ipv4acd_errno(acd, r, "Failed to send ARP probe: %m");
+                        goto fail;
+                }
+
+                log_ipv4acd(acd, "Probing "IPV4_ADDRESS_FMT_STR, IPV4_ADDRESS_FMT_VAL(acd->address));
+
+                if (acd->n_iteration < PROBE_NUM - 2) {
+                        ipv4acd_set_state(acd, IPV4ACD_STATE_PROBING, false);
+
+                        r = ipv4acd_set_next_wakeup(acd, PROBE_MIN_USEC, (PROBE_MAX_USEC-PROBE_MIN_USEC));
+                        if (r < 0)
+                                goto fail;
+                } else {
+                        ipv4acd_set_state(acd, IPV4ACD_STATE_WAITING_ANNOUNCE, true);
+
+                        r = ipv4acd_set_next_wakeup(acd, ANNOUNCE_WAIT_USEC, 0);
+                        if (r < 0)
+                                goto fail;
+                }
+
+                break;
+
+        case IPV4ACD_STATE_ANNOUNCING:
+                if (acd->n_iteration >= ANNOUNCE_NUM - 1) {
+                        ipv4acd_set_state(acd, IPV4ACD_STATE_RUNNING, false);
+                        break;
+                }
+
+                _fallthrough_;
+        case IPV4ACD_STATE_WAITING_ANNOUNCE:
+                /* Send announcement packet */
+                r = arp_send_announcement(acd->fd, acd->ifindex, &acd->address, &acd->mac_addr);
+                if (r < 0) {
+                        log_ipv4acd_errno(acd, r, "Failed to send ARP announcement: %m");
+                        goto fail;
+                }
+
+                log_ipv4acd(acd, "Announcing "IPV4_ADDRESS_FMT_STR, IPV4_ADDRESS_FMT_VAL(acd->address));
+
+                ipv4acd_set_state(acd, IPV4ACD_STATE_ANNOUNCING, false);
+
+                r = ipv4acd_set_next_wakeup(acd, ANNOUNCE_INTERVAL_USEC, 0);
+                if (r < 0)
+                        goto fail;
+
+                if (acd->n_iteration == 0) {
+                        acd->n_conflict = 0;
+                        ipv4acd_client_notify(acd, SD_IPV4ACD_EVENT_BIND);
+                }
+
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+
+fail:
+        sd_ipv4acd_stop(acd);
+        return 0;
+}
+
+static bool ipv4acd_arp_conflict(sd_ipv4acd *acd, const struct ether_arp *arp, bool announced) {
+        assert(acd);
+        assert(arp);
+
+        /* RFC 5227 section 2.1.1.
+         * "the host receives any ARP packet (Request *or* Reply) on the interface where the probe is
+         * being performed, where the packet's 'sender IP address' is the address being probed for,
+         * then the host MUST treat this address as being in use by some other host" */
+        if (memcmp(arp->arp_spa, &acd->address, sizeof(struct in_addr)) == 0)
+                return true;
+
+        if (announced)
+                /* the TPA matched instead of SPA, this is not a conflict */
+                return false;
+
+        /* "any ARP Probe where the packet's 'target IP address' is the address being probed for, and
+         * the packet's 'sender hardware address' is not the hardware address of any of the host's
+         * interfaces, then the host SHOULD similarly treat this as an address conflict" */
+        if (arp->ea_hdr.ar_op != htobe16(ARPOP_REQUEST))
+                return false; /* not ARP Request, ignoring. */
+        if (memeqzero(arp->arp_spa, sizeof(struct in_addr)) == 0)
+                return false; /* not ARP Probe, ignoring. */
+        if (memcmp(arp->arp_tpa, &acd->address, sizeof(struct in_addr)) != 0)
+                return false; /* target IP address does not match, BPF code is broken? */
+
+        if (acd->check_mac_callback &&
+            acd->check_mac_callback(acd, (const struct ether_addr*) arp->arp_sha, acd->check_mac_userdata) > 0)
+                /* sender hardware is one of the host's interfaces, ignoring. */
+                return false;
+
+        return true; /* conflict! */
+}
+
+static void ipv4acd_on_conflict(sd_ipv4acd *acd) {
+        assert(acd);
+
+        acd->n_conflict++;
+
+        log_ipv4acd(acd, "Conflict on "IPV4_ADDRESS_FMT_STR" (%u)", IPV4_ADDRESS_FMT_VAL(acd->address), acd->n_conflict);
+
+        ipv4acd_reset(acd);
+        ipv4acd_client_notify(acd, SD_IPV4ACD_EVENT_CONFLICT);
+}
+
+static int ipv4acd_on_packet(
+                sd_event_source *s,
+                int fd,
+                uint32_t revents,
+                void *userdata) {
+
+        sd_ipv4acd *acd = ASSERT_PTR(userdata);
+        struct ether_arp packet;
+        ssize_t n;
+        int r;
+
+        assert(s);
+        assert(fd >= 0);
+
+        n = recv(fd, &packet, sizeof(struct ether_arp), 0);
+        if (n < 0) {
+                if (ERRNO_IS_TRANSIENT(errno) || ERRNO_IS_DISCONNECT(errno))
+                        return 0;
+
+                log_ipv4acd_errno(acd, errno, "Failed to read ARP packet: %m");
+                goto fail;
+        }
+        if ((size_t) n != sizeof(struct ether_arp)) {
+                log_ipv4acd(acd, "Ignoring too short ARP packet.");
+                return 0;
+        }
+
+        switch (acd->state) {
+
+        case IPV4ACD_STATE_ANNOUNCING:
+        case IPV4ACD_STATE_RUNNING:
+
+                if (ipv4acd_arp_conflict(acd, &packet, true)) {
+                        usec_t ts;
+
+                        assert_se(sd_event_now(acd->event, CLOCK_BOOTTIME, &ts) >= 0);
+
+                        /* Defend address */
+                        if (ts > acd->defend_window) {
+                                acd->defend_window = ts + DEFEND_INTERVAL_USEC;
+                                r = arp_send_announcement(acd->fd, acd->ifindex, &acd->address, &acd->mac_addr);
+                                if (r < 0) {
+                                        log_ipv4acd_errno(acd, r, "Failed to send ARP announcement: %m");
+                                        goto fail;
+                                }
+
+                                log_ipv4acd(acd, "Defending "IPV4_ADDRESS_FMT_STR, IPV4_ADDRESS_FMT_VAL(acd->address));
+
+                        } else
+                                ipv4acd_on_conflict(acd);
+                }
+                break;
+
+        case IPV4ACD_STATE_WAITING_PROBE:
+        case IPV4ACD_STATE_PROBING:
+        case IPV4ACD_STATE_WAITING_ANNOUNCE:
+                if (ipv4acd_arp_conflict(acd, &packet, false))
+                        ipv4acd_on_conflict(acd);
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+
+fail:
+        sd_ipv4acd_stop(acd);
+        return 0;
+}
+
+int sd_ipv4acd_set_ifindex(sd_ipv4acd *acd, int ifindex) {
+        assert_return(acd, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+        assert_return(acd->state == IPV4ACD_STATE_INIT, -EBUSY);
+
+        acd->ifindex = ifindex;
+
+        return 0;
+}
+
+int sd_ipv4acd_get_ifindex(sd_ipv4acd *acd) {
+        if (!acd)
+                return -EINVAL;
+
+        return acd->ifindex;
+}
+
+int sd_ipv4acd_set_ifname(sd_ipv4acd *acd, const char *ifname) {
+        assert_return(acd, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&acd->ifname, ifname);
+}
+
+int sd_ipv4acd_get_ifname(sd_ipv4acd *acd, const char **ret) {
+        int r;
+
+        assert_return(acd, -EINVAL);
+
+        r = get_ifname(acd->ifindex, &acd->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = acd->ifname;
+
+        return 0;
+}
+
+int sd_ipv4acd_set_mac(sd_ipv4acd *acd, const struct ether_addr *addr) {
+        int r;
+
+        assert_return(acd, -EINVAL);
+        assert_return(addr, -EINVAL);
+        assert_return(!ether_addr_is_null(addr), -EINVAL);
+
+        acd->mac_addr = *addr;
+
+        if (!sd_ipv4acd_is_running(acd))
+                return 0;
+
+        assert(acd->fd >= 0);
+        r = arp_update_filter(acd->fd, &acd->address, &acd->mac_addr);
+        if (r < 0) {
+                ipv4acd_reset(acd);
+                return r;
+        }
+
+        return 0;
+}
+
+int sd_ipv4acd_detach_event(sd_ipv4acd *acd) {
+        assert_return(acd, -EINVAL);
+
+        acd->event = sd_event_unref(acd->event);
+
+        return 0;
+}
+
+int sd_ipv4acd_attach_event(sd_ipv4acd *acd, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(acd, -EINVAL);
+        assert_return(!acd->event, -EBUSY);
+
+        if (event)
+                acd->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&acd->event);
+                if (r < 0)
+                        return r;
+        }
+
+        acd->event_priority = priority;
+
+        return 0;
+}
+
+int sd_ipv4acd_set_callback(sd_ipv4acd *acd, sd_ipv4acd_callback_t cb, void *userdata) {
+        assert_return(acd, -EINVAL);
+
+        acd->callback = cb;
+        acd->userdata = userdata;
+
+        return 0;
+}
+
+int sd_ipv4acd_set_check_mac_callback(sd_ipv4acd *acd, sd_ipv4acd_check_mac_callback_t cb, void *userdata) {
+        assert_return(acd, -EINVAL);
+
+        acd->check_mac_callback = cb;
+        acd->check_mac_userdata = userdata;
+        return 0;
+}
+
+int sd_ipv4acd_set_address(sd_ipv4acd *acd, const struct in_addr *address) {
+        int r;
+
+        assert_return(acd, -EINVAL);
+        assert_return(address, -EINVAL);
+        assert_return(in4_addr_is_set(address), -EINVAL);
+
+        if (in4_addr_equal(&acd->address, address))
+                return 0;
+
+        acd->address = *address;
+
+        if (!sd_ipv4acd_is_running(acd))
+                return 0;
+
+        assert(acd->fd >= 0);
+        r = arp_update_filter(acd->fd, &acd->address, &acd->mac_addr);
+        if (r < 0)
+                goto fail;
+
+        r = ipv4acd_set_next_wakeup(acd, 0, 0);
+        if (r < 0)
+                goto fail;
+
+        ipv4acd_set_state(acd, IPV4ACD_STATE_STARTED, true);
+        return 0;
+
+fail:
+        ipv4acd_reset(acd);
+        return r;
+}
+
+int sd_ipv4acd_get_address(sd_ipv4acd *acd, struct in_addr *address) {
+        assert_return(acd, -EINVAL);
+        assert_return(address, -EINVAL);
+
+        *address = acd->address;
+
+        return 0;
+}
+
+int sd_ipv4acd_is_running(sd_ipv4acd *acd) {
+        assert_return(acd, false);
+
+        return acd->state != IPV4ACD_STATE_INIT;
+}
+
+int sd_ipv4acd_start(sd_ipv4acd *acd, bool reset_conflicts) {
+        int r;
+
+        assert_return(acd, -EINVAL);
+        assert_return(acd->event, -EINVAL);
+        assert_return(acd->ifindex > 0, -EINVAL);
+        assert_return(in4_addr_is_set(&acd->address), -EINVAL);
+        assert_return(!ether_addr_is_null(&acd->mac_addr), -EINVAL);
+        assert_return(acd->state == IPV4ACD_STATE_INIT, -EBUSY);
+
+        r = arp_network_bind_raw_socket(acd->ifindex, &acd->address, &acd->mac_addr);
+        if (r < 0)
+                return r;
+
+        close_and_replace(acd->fd, r);
+
+        if (reset_conflicts)
+                acd->n_conflict = 0;
+
+        r = sd_event_add_io(acd->event, &acd->receive_message_event_source, acd->fd, EPOLLIN, ipv4acd_on_packet, acd);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_priority(acd->receive_message_event_source, acd->event_priority);
+        if (r < 0)
+                goto fail;
+
+        (void) sd_event_source_set_description(acd->receive_message_event_source, "ipv4acd-receive-message");
+
+        r = ipv4acd_set_next_wakeup(acd, 0, 0);
+        if (r < 0)
+                goto fail;
+
+        ipv4acd_set_state(acd, IPV4ACD_STATE_STARTED, true);
+        return 0;
+
+fail:
+        ipv4acd_reset(acd);
+        return r;
+}
diff --git a/src/libsystemd-network/sd-ipv4ll.c b/src/libsystemd-network/sd-ipv4ll.c
new file mode 100644
index 0000000..4b0fac3
--- /dev/null
+++ b/src/libsystemd-network/sd-ipv4ll.c
@@ -0,0 +1,366 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Axis Communications AB. All rights reserved.
+***/
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "sd-id128.h"
+#include "sd-ipv4acd.h"
+#include "sd-ipv4ll.h"
+
+#include "alloc-util.h"
+#include "ether-addr-util.h"
+#include "in-addr-util.h"
+#include "network-common.h"
+#include "random-util.h"
+#include "siphash24.h"
+#include "sparse-endian.h"
+#include "string-util.h"
+#include "util.h"
+
+#define IPV4LL_NETWORK UINT32_C(0xA9FE0000)
+#define IPV4LL_NETMASK UINT32_C(0xFFFF0000)
+
+#define IPV4LL_DONT_DESTROY(ll) \
+        _cleanup_(sd_ipv4ll_unrefp) _unused_ sd_ipv4ll *_dont_destroy_##ll = sd_ipv4ll_ref(ll)
+
+struct sd_ipv4ll {
+        unsigned n_ref;
+
+        sd_ipv4acd *acd;
+
+        be32_t address; /* the address pushed to ACD */
+        struct ether_addr mac;
+
+        struct {
+                le64_t value;
+                le64_t generation;
+        } seed;
+        bool seed_set;
+
+        /* External */
+        be32_t claimed_address;
+
+        sd_ipv4ll_callback_t callback;
+        void *userdata;
+
+        sd_ipv4ll_check_mac_callback_t check_mac_callback;
+        void *check_mac_userdata;
+};
+
+#define log_ipv4ll_errno(ll, error, fmt, ...)           \
+        log_interface_prefix_full_errno(                \
+                "IPv4LL: ",                             \
+                sd_ipv4ll, ll,                          \
+                error, fmt, ##__VA_ARGS__)
+#define log_ipv4ll(ll, fmt, ...)                        \
+        log_interface_prefix_full_errno_zerook(         \
+                "IPv4LL: ",                             \
+                sd_ipv4ll, ll,                          \
+                0, fmt, ##__VA_ARGS__)
+
+static void ipv4ll_on_acd(sd_ipv4acd *acd, int event, void *userdata);
+static int ipv4ll_check_mac(sd_ipv4acd *acd, const struct ether_addr *mac, void *userdata);
+
+static sd_ipv4ll *ipv4ll_free(sd_ipv4ll *ll) {
+        assert(ll);
+
+        sd_ipv4acd_unref(ll->acd);
+        return mfree(ll);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(sd_ipv4ll, sd_ipv4ll, ipv4ll_free);
+
+int sd_ipv4ll_new(sd_ipv4ll **ret) {
+        _cleanup_(sd_ipv4ll_unrefp) sd_ipv4ll *ll = NULL;
+        int r;
+
+        assert_return(ret, -EINVAL);
+
+        ll = new0(sd_ipv4ll, 1);
+        if (!ll)
+                return -ENOMEM;
+
+        ll->n_ref = 1;
+
+        r = sd_ipv4acd_new(&ll->acd);
+        if (r < 0)
+                return r;
+
+        r = sd_ipv4acd_set_callback(ll->acd, ipv4ll_on_acd, ll);
+        if (r < 0)
+                return r;
+
+        r = sd_ipv4acd_set_check_mac_callback(ll->acd, ipv4ll_check_mac, ll);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(ll);
+
+        return 0;
+}
+
+int sd_ipv4ll_stop(sd_ipv4ll *ll) {
+        if (!ll)
+                return 0;
+
+        return sd_ipv4acd_stop(ll->acd);
+}
+
+int sd_ipv4ll_set_ifindex(sd_ipv4ll *ll, int ifindex) {
+        assert_return(ll, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+        assert_return(sd_ipv4ll_is_running(ll) == 0, -EBUSY);
+
+        return sd_ipv4acd_set_ifindex(ll->acd, ifindex);
+}
+
+int sd_ipv4ll_get_ifindex(sd_ipv4ll *ll) {
+        if (!ll)
+                return -EINVAL;
+
+        return sd_ipv4acd_get_ifindex(ll->acd);
+}
+
+int sd_ipv4ll_set_ifname(sd_ipv4ll *ll, const char *ifname) {
+        assert_return(ll, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        return sd_ipv4acd_set_ifname(ll->acd, ifname);
+}
+
+int sd_ipv4ll_get_ifname(sd_ipv4ll *ll, const char **ret) {
+        assert_return(ll, -EINVAL);
+
+        return sd_ipv4acd_get_ifname(ll->acd, ret);
+}
+
+int sd_ipv4ll_set_mac(sd_ipv4ll *ll, const struct ether_addr *addr) {
+        int r;
+
+        assert_return(ll, -EINVAL);
+        assert_return(addr, -EINVAL);
+        assert_return(!ether_addr_is_null(addr), -EINVAL);
+
+        r = sd_ipv4acd_set_mac(ll->acd, addr);
+        if (r < 0)
+                return r;
+
+        ll->mac = *addr;
+        return 0;
+}
+
+int sd_ipv4ll_detach_event(sd_ipv4ll *ll) {
+        assert_return(ll, -EINVAL);
+
+        return sd_ipv4acd_detach_event(ll->acd);
+}
+
+int sd_ipv4ll_attach_event(sd_ipv4ll *ll, sd_event *event, int64_t priority) {
+        assert_return(ll, -EINVAL);
+
+        return sd_ipv4acd_attach_event(ll->acd, event, priority);
+}
+
+int sd_ipv4ll_set_callback(sd_ipv4ll *ll, sd_ipv4ll_callback_t cb, void *userdata) {
+        assert_return(ll, -EINVAL);
+
+        ll->callback = cb;
+        ll->userdata = userdata;
+
+        return 0;
+}
+
+int sd_ipv4ll_set_check_mac_callback(sd_ipv4ll *ll, sd_ipv4ll_check_mac_callback_t cb, void *userdata) {
+        assert_return(ll, -EINVAL);
+
+        ll->check_mac_callback = cb;
+        ll->check_mac_userdata = userdata;
+
+        return 0;
+}
+
+int sd_ipv4ll_get_address(sd_ipv4ll *ll, struct in_addr *address) {
+        assert_return(ll, -EINVAL);
+        assert_return(address, -EINVAL);
+
+        if (ll->claimed_address == 0)
+                return -ENOENT;
+
+        address->s_addr = ll->claimed_address;
+
+        return 0;
+}
+
+int sd_ipv4ll_set_address_seed(sd_ipv4ll *ll, uint64_t seed) {
+        assert_return(ll, -EINVAL);
+        assert_return(sd_ipv4ll_is_running(ll) == 0, -EBUSY);
+
+        ll->seed.value = htole64(seed);
+        ll->seed_set = true;
+
+        return 0;
+}
+
+int sd_ipv4ll_is_running(sd_ipv4ll *ll) {
+        assert_return(ll, false);
+
+        return sd_ipv4acd_is_running(ll->acd);
+}
+
+int sd_ipv4ll_set_address(sd_ipv4ll *ll, const struct in_addr *address) {
+        int r;
+
+        assert_return(ll, -EINVAL);
+        assert_return(address, -EINVAL);
+        assert_return(in4_addr_is_link_local_dynamic(address), -EINVAL);
+
+        r = sd_ipv4acd_set_address(ll->acd, address);
+        if (r < 0)
+                return r;
+
+        ll->address = address->s_addr;
+
+        return 0;
+}
+
+#define PICK_HASH_KEY SD_ID128_MAKE(15,ac,82,a6,d6,3f,49,78,98,77,5d,0c,69,02,94,0b)
+
+static int ipv4ll_pick_address(sd_ipv4ll *ll) {
+        be32_t addr;
+
+        assert(ll);
+
+        do {
+                uint64_t h;
+
+                h = siphash24(&ll->seed, sizeof(ll->seed), PICK_HASH_KEY.bytes);
+
+                /* Increase the generation counter by one */
+                ll->seed.generation = htole64(le64toh(ll->seed.generation) + 1);
+
+                addr = htobe32((h & UINT32_C(0x0000FFFF)) | IPV4LL_NETWORK);
+        } while (addr == ll->address ||
+                 IN_SET(be32toh(addr) & 0x0000FF00U, 0x0000U, 0xFF00U));
+
+        log_ipv4ll(ll, "Picked new IP address %s.", IN4_ADDR_TO_STRING((const struct in_addr*) &addr));
+
+        return sd_ipv4ll_set_address(ll, &(struct in_addr) { addr });
+}
+
+#define MAC_HASH_KEY SD_ID128_MAKE(df,04,22,98,3f,ad,14,52,f9,87,2e,d1,9c,70,e2,f2)
+
+static int ipv4ll_start_internal(sd_ipv4ll *ll, bool reset_generation) {
+        int r;
+        bool picked_address = false;
+
+        assert_return(ll, -EINVAL);
+        assert_return(!ether_addr_is_null(&ll->mac), -EINVAL);
+
+        /* If no random seed is set, generate some from the MAC address */
+        if (!ll->seed_set)
+                ll->seed.value = htole64(siphash24(ll->mac.ether_addr_octet, ETH_ALEN, MAC_HASH_KEY.bytes));
+
+        if (reset_generation)
+                ll->seed.generation = 0;
+
+        if (ll->address == 0) {
+                r = ipv4ll_pick_address(ll);
+                if (r < 0)
+                        return r;
+
+                picked_address = true;
+        }
+
+        r = sd_ipv4acd_start(ll->acd, reset_generation);
+        if (r < 0) {
+
+                /* We couldn't start? If so, let's forget the picked address again, the user might make a change and
+                 * retry, and we want the new data to take effect when picking an address. */
+                if (picked_address)
+                        ll->address = 0;
+
+                return r;
+        }
+
+        return 1;
+}
+
+int sd_ipv4ll_start(sd_ipv4ll *ll) {
+        assert_return(ll, -EINVAL);
+
+        if (sd_ipv4ll_is_running(ll))
+                return 0;
+
+        return ipv4ll_start_internal(ll, true);
+}
+
+int sd_ipv4ll_restart(sd_ipv4ll *ll) {
+        ll->address = 0;
+
+        return ipv4ll_start_internal(ll, false);
+}
+
+static void ipv4ll_client_notify(sd_ipv4ll *ll, int event) {
+        assert(ll);
+
+        if (ll->callback)
+                ll->callback(ll, event, ll->userdata);
+}
+
+void ipv4ll_on_acd(sd_ipv4acd *acd, int event, void *userdata) {
+        sd_ipv4ll *ll = ASSERT_PTR(userdata);
+        IPV4LL_DONT_DESTROY(ll);
+        int r;
+
+        assert(acd);
+
+        switch (event) {
+
+        case SD_IPV4ACD_EVENT_STOP:
+                ipv4ll_client_notify(ll, SD_IPV4LL_EVENT_STOP);
+                ll->claimed_address = 0;
+                break;
+
+        case SD_IPV4ACD_EVENT_BIND:
+                ll->claimed_address = ll->address;
+                ipv4ll_client_notify(ll, SD_IPV4LL_EVENT_BIND);
+                break;
+
+        case SD_IPV4ACD_EVENT_CONFLICT:
+                /* if an address was already bound we must call up to the
+                   user to handle this, otherwise we just try again */
+                if (ll->claimed_address != 0) {
+                        ipv4ll_client_notify(ll, SD_IPV4LL_EVENT_CONFLICT);
+
+                        ll->claimed_address = 0;
+                } else {
+                        r = sd_ipv4ll_restart(ll);
+                        if (r < 0)
+                                goto error;
+                }
+
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        return;
+
+error:
+        ipv4ll_client_notify(ll, SD_IPV4LL_EVENT_STOP);
+}
+
+static int ipv4ll_check_mac(sd_ipv4acd *acd, const struct ether_addr *mac, void *userdata) {
+        sd_ipv4ll *ll = ASSERT_PTR(userdata);
+
+        if (ll->check_mac_callback)
+                return ll->check_mac_callback(ll, mac, ll->check_mac_userdata);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-lldp-rx.c b/src/libsystemd-network/sd-lldp-rx.c
new file mode 100644
index 0000000..0479cff
--- /dev/null
+++ b/src/libsystemd-network/sd-lldp-rx.c
@@ -0,0 +1,525 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <arpa/inet.h>
+#include <linux/sockios.h>
+#include <sys/ioctl.h>
+
+#include "sd-lldp-rx.h"
+
+#include "alloc-util.h"
+#include "ether-addr-util.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "lldp-neighbor.h"
+#include "lldp-network.h"
+#include "lldp-rx-internal.h"
+#include "memory-util.h"
+#include "network-common.h"
+#include "socket-util.h"
+#include "sort-util.h"
+#include "string-table.h"
+
+#define LLDP_DEFAULT_NEIGHBORS_MAX 128U
+
+static const char * const lldp_rx_event_table[_SD_LLDP_RX_EVENT_MAX] = {
+        [SD_LLDP_RX_EVENT_ADDED]     = "added",
+        [SD_LLDP_RX_EVENT_REMOVED]   = "removed",
+        [SD_LLDP_RX_EVENT_UPDATED]   = "updated",
+        [SD_LLDP_RX_EVENT_REFRESHED] = "refreshed",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(lldp_rx_event, sd_lldp_rx_event_t);
+
+static void lldp_rx_flush_neighbors(sd_lldp_rx *lldp_rx) {
+        assert(lldp_rx);
+
+        hashmap_clear(lldp_rx->neighbor_by_id);
+}
+
+static void lldp_rx_callback(sd_lldp_rx *lldp_rx, sd_lldp_rx_event_t event, sd_lldp_neighbor *n) {
+        assert(lldp_rx);
+        assert(event >= 0 && event < _SD_LLDP_RX_EVENT_MAX);
+
+        if (!lldp_rx->callback)
+                return (void) log_lldp_rx(lldp_rx, "Received '%s' event.", lldp_rx_event_to_string(event));
+
+        log_lldp_rx(lldp_rx, "Invoking callback for '%s' event.", lldp_rx_event_to_string(event));
+        lldp_rx->callback(lldp_rx, event, n, lldp_rx->userdata);
+}
+
+static int lldp_rx_make_space(sd_lldp_rx *lldp_rx, size_t extra) {
+        usec_t t = USEC_INFINITY;
+        bool changed = false;
+
+        assert(lldp_rx);
+
+        /* Remove all entries that are past their TTL, and more until at least the specified number of extra entries
+         * are free. */
+
+        for (;;) {
+                _cleanup_(sd_lldp_neighbor_unrefp) sd_lldp_neighbor *n = NULL;
+
+                n = prioq_peek(lldp_rx->neighbor_by_expiry);
+                if (!n)
+                        break;
+
+                sd_lldp_neighbor_ref(n);
+
+                if (hashmap_size(lldp_rx->neighbor_by_id) > LESS_BY(lldp_rx->neighbors_max, extra))
+                        goto remove_one;
+
+                if (t == USEC_INFINITY)
+                        t = now(CLOCK_BOOTTIME);
+
+                if (n->until > t)
+                        break;
+
+        remove_one:
+                lldp_neighbor_unlink(n);
+                lldp_rx_callback(lldp_rx, SD_LLDP_RX_EVENT_REMOVED, n);
+                changed = true;
+        }
+
+        return changed;
+}
+
+static bool lldp_rx_keep_neighbor(sd_lldp_rx *lldp_rx, sd_lldp_neighbor *n) {
+        assert(lldp_rx);
+        assert(n);
+
+        /* Don't keep data with a zero TTL */
+        if (n->ttl <= 0)
+                return false;
+
+        /* Filter out data from the filter address */
+        if (!ether_addr_is_null(&lldp_rx->filter_address) &&
+            ether_addr_equal(&lldp_rx->filter_address, &n->source_address))
+                return false;
+
+        /* Only add if the neighbor has a capability we are interested in. Note that we also store all neighbors with
+         * no caps field set. */
+        if (n->has_capabilities &&
+            (n->enabled_capabilities & lldp_rx->capability_mask) == 0)
+                return false;
+
+        /* Keep everything else */
+        return true;
+}
+
+static int lldp_rx_start_timer(sd_lldp_rx *lldp_rx, sd_lldp_neighbor *neighbor);
+
+static int lldp_rx_add_neighbor(sd_lldp_rx *lldp_rx, sd_lldp_neighbor *n) {
+        _cleanup_(sd_lldp_neighbor_unrefp) sd_lldp_neighbor *old = NULL;
+        bool keep;
+        int r;
+
+        assert(lldp_rx);
+        assert(n);
+        assert(!n->lldp_rx);
+
+        keep = lldp_rx_keep_neighbor(lldp_rx, n);
+
+        /* First retrieve the old entry for this MSAP */
+        old = hashmap_get(lldp_rx->neighbor_by_id, &n->id);
+        if (old) {
+                sd_lldp_neighbor_ref(old);
+
+                if (!keep) {
+                        lldp_neighbor_unlink(old);
+                        lldp_rx_callback(lldp_rx, SD_LLDP_RX_EVENT_REMOVED, old);
+                        return 0;
+                }
+
+                if (lldp_neighbor_equal(n, old)) {
+                        /* Is this equal, then restart the TTL counter, but don't do anything else. */
+                        old->timestamp = n->timestamp;
+                        lldp_rx_start_timer(lldp_rx, old);
+                        lldp_rx_callback(lldp_rx, SD_LLDP_RX_EVENT_REFRESHED, old);
+                        return 0;
+                }
+
+                /* Data changed, remove the old entry, and add a new one */
+                lldp_neighbor_unlink(old);
+
+        } else if (!keep)
+                return 0;
+
+        /* Then, make room for at least one new neighbor */
+        lldp_rx_make_space(lldp_rx, 1);
+
+        r = hashmap_ensure_put(&lldp_rx->neighbor_by_id, &lldp_neighbor_hash_ops, &n->id, n);
+        if (r < 0)
+                goto finish;
+
+        r = prioq_ensure_put(&lldp_rx->neighbor_by_expiry, lldp_neighbor_prioq_compare_func, n, &n->prioq_idx);
+        if (r < 0) {
+                assert_se(hashmap_remove(lldp_rx->neighbor_by_id, &n->id) == n);
+                goto finish;
+        }
+
+        n->lldp_rx = lldp_rx;
+
+        lldp_rx_start_timer(lldp_rx, n);
+        lldp_rx_callback(lldp_rx, old ? SD_LLDP_RX_EVENT_UPDATED : SD_LLDP_RX_EVENT_ADDED, n);
+
+        return 1;
+
+finish:
+        if (old)
+                lldp_rx_callback(lldp_rx, SD_LLDP_RX_EVENT_REMOVED, old);
+
+        return r;
+}
+
+static int lldp_rx_handle_datagram(sd_lldp_rx *lldp_rx, sd_lldp_neighbor *n) {
+        int r;
+
+        assert(lldp_rx);
+        assert(n);
+
+        r = lldp_neighbor_parse(n);
+        if (r < 0)
+                return r;
+
+        r = lldp_rx_add_neighbor(lldp_rx, n);
+        if (r < 0)
+                return log_lldp_rx_errno(lldp_rx, r, "Failed to add datagram. Ignoring.");
+
+        log_lldp_rx(lldp_rx, "Successfully processed LLDP datagram.");
+        return 0;
+}
+
+static int lldp_rx_receive_datagram(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        _cleanup_(sd_lldp_neighbor_unrefp) sd_lldp_neighbor *n = NULL;
+        ssize_t space, length;
+        sd_lldp_rx *lldp_rx = ASSERT_PTR(userdata);
+        struct timespec ts;
+
+        assert(fd >= 0);
+
+        space = next_datagram_size_fd(fd);
+        if (space < 0) {
+                if (ERRNO_IS_TRANSIENT(space) || ERRNO_IS_DISCONNECT(space))
+                        return 0;
+
+                log_lldp_rx_errno(lldp_rx, space, "Failed to determine datagram size to read, ignoring: %m");
+                return 0;
+        }
+
+        n = lldp_neighbor_new(space);
+        if (!n) {
+                log_oom_debug();
+                return 0;
+        }
+
+        length = recv(fd, LLDP_NEIGHBOR_RAW(n), n->raw_size, MSG_DONTWAIT);
+        if (length < 0) {
+                if (ERRNO_IS_TRANSIENT(errno) || ERRNO_IS_DISCONNECT(errno))
+                        return 0;
+
+                log_lldp_rx_errno(lldp_rx, errno, "Failed to read LLDP datagram, ignoring: %m");
+                return 0;
+        }
+
+        if ((size_t) length != n->raw_size) {
+                log_lldp_rx(lldp_rx, "Packet size mismatch, ignoring");
+                return 0;
+        }
+
+        /* Try to get the timestamp of this packet if it is known */
+        if (ioctl(fd, SIOCGSTAMPNS, &ts) >= 0)
+                triple_timestamp_from_realtime(&n->timestamp, timespec_load(&ts));
+        else
+                triple_timestamp_get(&n->timestamp);
+
+        (void) lldp_rx_handle_datagram(lldp_rx, n);
+        return 0;
+}
+
+static void lldp_rx_reset(sd_lldp_rx *lldp_rx) {
+        assert(lldp_rx);
+
+        (void) event_source_disable(lldp_rx->timer_event_source);
+        lldp_rx->io_event_source = sd_event_source_disable_unref(lldp_rx->io_event_source);
+        lldp_rx->fd = safe_close(lldp_rx->fd);
+}
+
+int sd_lldp_rx_is_running(sd_lldp_rx *lldp_rx) {
+        if (!lldp_rx)
+                return false;
+
+        return lldp_rx->fd >= 0;
+}
+
+int sd_lldp_rx_start(sd_lldp_rx *lldp_rx) {
+        int r;
+
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(lldp_rx->event, -EINVAL);
+        assert_return(lldp_rx->ifindex > 0, -EINVAL);
+
+        if (sd_lldp_rx_is_running(lldp_rx))
+                return 0;
+
+        assert(!lldp_rx->io_event_source);
+
+        lldp_rx->fd = lldp_network_bind_raw_socket(lldp_rx->ifindex);
+        if (lldp_rx->fd < 0)
+                return lldp_rx->fd;
+
+        r = sd_event_add_io(lldp_rx->event, &lldp_rx->io_event_source, lldp_rx->fd, EPOLLIN, lldp_rx_receive_datagram, lldp_rx);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_priority(lldp_rx->io_event_source, lldp_rx->event_priority);
+        if (r < 0)
+                goto fail;
+
+        (void) sd_event_source_set_description(lldp_rx->io_event_source, "lldp-rx-io");
+
+        log_lldp_rx(lldp_rx, "Started LLDP client");
+        return 1;
+
+fail:
+        lldp_rx_reset(lldp_rx);
+        return r;
+}
+
+int sd_lldp_rx_stop(sd_lldp_rx *lldp_rx) {
+        if (!sd_lldp_rx_is_running(lldp_rx))
+                return 0;
+
+        log_lldp_rx(lldp_rx, "Stopping LLDP client");
+
+        lldp_rx_reset(lldp_rx);
+        lldp_rx_flush_neighbors(lldp_rx);
+
+        return 1;
+}
+
+int sd_lldp_rx_attach_event(sd_lldp_rx *lldp_rx, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(!sd_lldp_rx_is_running(lldp_rx), -EBUSY);
+        assert_return(!lldp_rx->event, -EBUSY);
+
+        if (event)
+                lldp_rx->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&lldp_rx->event);
+                if (r < 0)
+                        return r;
+        }
+
+        lldp_rx->event_priority = priority;
+
+        return 0;
+}
+
+int sd_lldp_rx_detach_event(sd_lldp_rx *lldp_rx) {
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(!sd_lldp_rx_is_running(lldp_rx), -EBUSY);
+
+        lldp_rx->io_event_source = sd_event_source_disable_unref(lldp_rx->io_event_source);
+        lldp_rx->timer_event_source = sd_event_source_disable_unref(lldp_rx->timer_event_source);
+        lldp_rx->event = sd_event_unref(lldp_rx->event);
+        return 0;
+}
+
+sd_event* sd_lldp_rx_get_event(sd_lldp_rx *lldp_rx) {
+        assert_return(lldp_rx, NULL);
+
+        return lldp_rx->event;
+}
+
+int sd_lldp_rx_set_callback(sd_lldp_rx *lldp_rx, sd_lldp_rx_callback_t cb, void *userdata) {
+        assert_return(lldp_rx, -EINVAL);
+
+        lldp_rx->callback = cb;
+        lldp_rx->userdata = userdata;
+
+        return 0;
+}
+
+int sd_lldp_rx_set_ifindex(sd_lldp_rx *lldp_rx, int ifindex) {
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+        assert_return(!sd_lldp_rx_is_running(lldp_rx), -EBUSY);
+
+        lldp_rx->ifindex = ifindex;
+        return 0;
+}
+
+int sd_lldp_rx_set_ifname(sd_lldp_rx *lldp_rx, const char *ifname) {
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&lldp_rx->ifname, ifname);
+}
+
+int sd_lldp_rx_get_ifname(sd_lldp_rx *lldp_rx, const char **ret) {
+        int r;
+
+        assert_return(lldp_rx, -EINVAL);
+
+        r = get_ifname(lldp_rx->ifindex, &lldp_rx->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = lldp_rx->ifname;
+
+        return 0;
+}
+
+static sd_lldp_rx *lldp_rx_free(sd_lldp_rx *lldp_rx) {
+        if (!lldp_rx)
+                return NULL;
+
+        lldp_rx_reset(lldp_rx);
+
+        sd_lldp_rx_detach_event(lldp_rx);
+
+        lldp_rx_flush_neighbors(lldp_rx);
+
+        hashmap_free(lldp_rx->neighbor_by_id);
+        prioq_free(lldp_rx->neighbor_by_expiry);
+        free(lldp_rx->ifname);
+        return mfree(lldp_rx);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_lldp_rx, sd_lldp_rx, lldp_rx_free);
+
+int sd_lldp_rx_new(sd_lldp_rx **ret) {
+        _cleanup_(sd_lldp_rx_unrefp) sd_lldp_rx *lldp_rx = NULL;
+
+        assert_return(ret, -EINVAL);
+
+        lldp_rx = new(sd_lldp_rx, 1);
+        if (!lldp_rx)
+                return -ENOMEM;
+
+        *lldp_rx = (sd_lldp_rx) {
+                .n_ref = 1,
+                .fd = -1,
+                .neighbors_max = LLDP_DEFAULT_NEIGHBORS_MAX,
+                .capability_mask = UINT16_MAX,
+        };
+
+        *ret = TAKE_PTR(lldp_rx);
+        return 0;
+}
+
+static int on_timer_event(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_lldp_rx *lldp_rx = userdata;
+        int r;
+
+        r = lldp_rx_make_space(lldp_rx, 0);
+        if (r < 0) {
+                log_lldp_rx_errno(lldp_rx, r, "Failed to make space, ignoring: %m");
+                return 0;
+        }
+
+        r = lldp_rx_start_timer(lldp_rx, NULL);
+        if (r < 0) {
+                log_lldp_rx_errno(lldp_rx, r, "Failed to restart timer, ignoring: %m");
+                return 0;
+        }
+
+        return 0;
+}
+
+static int lldp_rx_start_timer(sd_lldp_rx *lldp_rx, sd_lldp_neighbor *neighbor) {
+        sd_lldp_neighbor *n;
+
+        assert(lldp_rx);
+        assert(lldp_rx->event);
+
+        if (neighbor)
+                lldp_neighbor_start_ttl(neighbor);
+
+        n = prioq_peek(lldp_rx->neighbor_by_expiry);
+        if (!n)
+                return event_source_disable(lldp_rx->timer_event_source);
+
+        return event_reset_time(lldp_rx->event, &lldp_rx->timer_event_source,
+                                CLOCK_BOOTTIME,
+                                n->until, 0,
+                                on_timer_event, lldp_rx,
+                                lldp_rx->event_priority, "lldp-rx-timer", true);
+}
+
+static inline int neighbor_compare_func(sd_lldp_neighbor * const *a, sd_lldp_neighbor * const *b) {
+        assert(a);
+        assert(b);
+        assert(*a);
+        assert(*b);
+
+        return lldp_neighbor_id_compare_func(&(*a)->id, &(*b)->id);
+}
+
+int sd_lldp_rx_get_neighbors(sd_lldp_rx *lldp_rx, sd_lldp_neighbor ***ret) {
+        _cleanup_free_ sd_lldp_neighbor **l = NULL;
+        sd_lldp_neighbor *n;
+        int k = 0;
+
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(ret, -EINVAL);
+
+        if (hashmap_isempty(lldp_rx->neighbor_by_id)) { /* Special shortcut */
+                *ret = NULL;
+                return 0;
+        }
+
+        l = new0(sd_lldp_neighbor*, hashmap_size(lldp_rx->neighbor_by_id));
+        if (!l)
+                return -ENOMEM;
+
+        HASHMAP_FOREACH(n, lldp_rx->neighbor_by_id)
+                l[k++] = sd_lldp_neighbor_ref(n);
+
+        assert((size_t) k == hashmap_size(lldp_rx->neighbor_by_id));
+
+        /* Return things in a stable order */
+        typesafe_qsort(l, k, neighbor_compare_func);
+        *ret = TAKE_PTR(l);
+
+        return k;
+}
+
+int sd_lldp_rx_set_neighbors_max(sd_lldp_rx *lldp_rx, uint64_t m) {
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(m > 0, -EINVAL);
+
+        lldp_rx->neighbors_max = m;
+        lldp_rx_make_space(lldp_rx, 0);
+
+        return 0;
+}
+
+int sd_lldp_rx_match_capabilities(sd_lldp_rx *lldp_rx, uint16_t mask) {
+        assert_return(lldp_rx, -EINVAL);
+        assert_return(mask != 0, -EINVAL);
+
+        lldp_rx->capability_mask = mask;
+
+        return 0;
+}
+
+int sd_lldp_rx_set_filter_address(sd_lldp_rx *lldp_rx, const struct ether_addr *addr) {
+        assert_return(lldp_rx, -EINVAL);
+
+        /* In order to deal nicely with bridges that send back our own packets, allow one address to be filtered, so
+         * that our own can be filtered out here. */
+
+        if (addr)
+                lldp_rx->filter_address = *addr;
+        else
+                zero(lldp_rx->filter_address);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-lldp-tx.c b/src/libsystemd-network/sd-lldp-tx.c
new file mode 100644
index 0000000..d2d24be
--- /dev/null
+++ b/src/libsystemd-network/sd-lldp-tx.c
@@ -0,0 +1,628 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <arpa/inet.h>
+#include <linux/sockios.h>
+#include <sys/ioctl.h>
+
+#include "sd-event.h"
+#include "sd-id128.h"
+#include "sd-lldp-tx.h"
+
+#include "alloc-util.h"
+#include "ether-addr-util.h"
+#include "fd-util.h"
+#include "hostname-util.h"
+#include "network-common.h"
+#include "random-util.h"
+#include "socket-util.h"
+#include "string-util.h"
+#include "time-util.h"
+#include "unaligned.h"
+#include "web-util.h"
+
+/* The LLDP spec calls this "txFastInit", see 9.2.5.19 */
+#define LLDP_FAST_TX_INIT 4U
+
+/* The LLDP spec calls this "msgTxHold", see 9.2.5.6 */
+#define LLDP_TX_HOLD 4U
+
+/* The jitter range to add, see 9.2.2. */
+#define LLDP_TX_JITTER_USEC (400U * USEC_PER_MSEC)
+
+/* The LLDP spec calls this msgTxInterval, but we subtract half the jitter off it. */
+#define LLDP_TX_INTERVAL_USEC (30U * USEC_PER_SEC - LLDP_TX_JITTER_USEC / 2)
+
+/* The LLDP spec calls this msgFastTx, but we subtract half the jitter off it. */
+#define LLDP_FAST_TX_INTERVAL_USEC (1U * USEC_PER_SEC - LLDP_TX_JITTER_USEC / 2)
+
+#define LLDP_TX_TTL ((uint16_t) DIV_ROUND_UP(LLDP_TX_INTERVAL_USEC * LLDP_TX_HOLD + 1, USEC_PER_SEC))
+
+static const struct ether_addr lldp_multicast_addr[_SD_LLDP_MULTICAST_MODE_MAX] = {
+        [SD_LLDP_MULTICAST_MODE_NEAREST_BRIDGE]  = {{ 0x01, 0x80, 0xc2, 0x00, 0x00, 0x0e }},
+        [SD_LLDP_MULTICAST_MODE_NON_TPMR_BRIDGE] = {{ 0x01, 0x80, 0xc2, 0x00, 0x00, 0x03 }},
+        [SD_LLDP_MULTICAST_MODE_CUSTOMER_BRIDGE] = {{ 0x01, 0x80, 0xc2, 0x00, 0x00, 0x00 }},
+};
+
+struct sd_lldp_tx {
+        unsigned n_ref;
+
+        int ifindex;
+        char *ifname;
+
+        sd_event *event;
+        int64_t event_priority;
+        sd_event_source *timer_event_source;
+
+        unsigned fast_tx;
+
+        sd_lldp_multicast_mode_t mode;
+        struct ether_addr hwaddr;
+
+        char *port_description;
+        char *hostname;
+        char *pretty_hostname;
+        char *mud_url;
+        uint16_t supported_capabilities;
+        uint16_t enabled_capabilities;
+};
+
+#define log_lldp_tx_errno(lldp_tx, error, fmt, ...)     \
+        log_interface_prefix_full_errno(                \
+                "LLDP Tx: ",                            \
+                sd_lldp_tx, lldp_tx,                    \
+                error, fmt, ##__VA_ARGS__)
+#define log_lldp_tx(lldp_tx, fmt, ...)                  \
+        log_interface_prefix_full_errno_zerook(         \
+                "LLDP Tx: ",                            \
+                sd_lldp_tx, lldp_tx,                    \
+                0, fmt, ##__VA_ARGS__)
+
+static sd_lldp_tx *lldp_tx_free(sd_lldp_tx *lldp_tx) {
+        if (!lldp_tx)
+                return NULL;
+
+        sd_lldp_tx_detach_event(lldp_tx);
+
+        free(lldp_tx->port_description);
+        free(lldp_tx->hostname);
+        free(lldp_tx->pretty_hostname);
+        free(lldp_tx->mud_url);
+
+        free(lldp_tx->ifname);
+        return mfree(lldp_tx);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_lldp_tx, sd_lldp_tx, lldp_tx_free);
+
+int sd_lldp_tx_new(sd_lldp_tx **ret) {
+        _cleanup_(sd_lldp_tx_unrefp) sd_lldp_tx *lldp_tx = NULL;
+
+        assert_return(ret, -EINVAL);
+
+        lldp_tx = new(sd_lldp_tx, 1);
+        if (!lldp_tx)
+                return -ENOMEM;
+
+        *lldp_tx = (sd_lldp_tx) {
+                .n_ref = 1,
+                .mode = _SD_LLDP_MULTICAST_MODE_INVALID,
+        };
+
+        *ret = TAKE_PTR(lldp_tx);
+        return 0;
+}
+
+int sd_lldp_tx_set_ifindex(sd_lldp_tx *lldp_tx, int ifindex) {
+        assert_return(lldp_tx, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+
+        lldp_tx->ifindex = ifindex;
+        return 0;
+}
+
+int sd_lldp_tx_set_ifname(sd_lldp_tx *lldp_tx, const char *ifname) {
+        assert_return(lldp_tx, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&lldp_tx->ifname, ifname);
+}
+
+int sd_lldp_tx_get_ifname(sd_lldp_tx *lldp_tx, const char **ret) {
+        int r;
+
+        assert_return(lldp_tx, -EINVAL);
+
+        r = get_ifname(lldp_tx->ifindex, &lldp_tx->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = lldp_tx->ifname;
+
+        return 0;
+}
+
+int sd_lldp_tx_set_multicast_mode(sd_lldp_tx *lldp_tx, sd_lldp_multicast_mode_t mode) {
+        assert_return(lldp_tx, -EINVAL);
+        assert_return(mode >= 0 && mode < _SD_LLDP_MULTICAST_MODE_MAX, -EINVAL);
+
+        lldp_tx->mode = mode;
+        return 0;
+}
+
+int sd_lldp_tx_set_hwaddr(sd_lldp_tx *lldp_tx, const struct ether_addr *hwaddr) {
+        assert_return(lldp_tx, -EINVAL);
+        assert_return(!ether_addr_is_null(hwaddr), -EINVAL);
+
+        lldp_tx->hwaddr = *hwaddr;
+        return 0;
+}
+
+int sd_lldp_tx_set_capabilities(sd_lldp_tx *lldp_tx, uint16_t supported, uint16_t enabled) {
+        assert_return(lldp_tx, -EINVAL);
+        assert_return((enabled & ~supported) == 0, -EINVAL);
+
+        lldp_tx->supported_capabilities = supported;
+        lldp_tx->enabled_capabilities = enabled;
+        return 0;
+}
+
+int sd_lldp_tx_set_port_description(sd_lldp_tx *lldp_tx, const char *port_description) {
+        assert_return(lldp_tx, -EINVAL);
+
+        /* An empty string unset the previously set hostname. */
+        if (strlen_ptr(port_description) >= 512)
+                return -EINVAL;
+
+        return free_and_strdup(&lldp_tx->port_description, empty_to_null(port_description));
+}
+
+int sd_lldp_tx_set_hostname(sd_lldp_tx *lldp_tx, const char *hostname) {
+        assert_return(lldp_tx, -EINVAL);
+
+        /* An empty string unset the previously set hostname. */
+        if (!isempty(hostname)) {
+                assert_cc(HOST_NAME_MAX < 512);
+
+                if (!hostname_is_valid(hostname, 0))
+                        return -EINVAL;
+        }
+
+        return free_and_strdup(&lldp_tx->hostname, empty_to_null(hostname));
+}
+
+int sd_lldp_tx_set_pretty_hostname(sd_lldp_tx *lldp_tx, const char *pretty_hostname) {
+        assert_return(lldp_tx, -EINVAL);
+
+        /* An empty string unset the previously set hostname. */
+        if (strlen_ptr(pretty_hostname) >= 512)
+                return -EINVAL;
+
+        return free_and_strdup(&lldp_tx->pretty_hostname, empty_to_null(pretty_hostname));
+}
+
+int sd_lldp_tx_set_mud_url(sd_lldp_tx *lldp_tx, const char *mud_url) {
+        assert_return(lldp_tx, -EINVAL);
+
+        /* An empty string unset the previously set hostname. */
+        if (!isempty(mud_url)) {
+                /* Unless the maximum length of each value is 511, the MUD url must be smaller than 256.
+                 * See RFC 8520. */
+                if (strlen(mud_url) >= 256)
+                        return -EINVAL;
+
+                if (!http_url_is_valid(mud_url))
+                        return -EINVAL;
+        }
+
+        return free_and_strdup(&lldp_tx->mud_url, empty_to_null(mud_url));
+}
+
+static size_t lldp_tx_calculate_maximum_packet_size(sd_lldp_tx *lldp_tx, const char *hostname, const char *pretty_hostname) {
+        assert(lldp_tx);
+        assert(lldp_tx->ifindex > 0);
+
+        return sizeof(struct ether_header) +
+                /* Chassis ID */
+                2 + 1 + (SD_ID128_STRING_MAX - 1) +
+                /* Port ID */
+                2 + 1 + strlen_ptr(lldp_tx->ifname) +
+                /* TTL */
+                2 + 2 +
+                /* Port description */
+                2 + strlen_ptr(lldp_tx->port_description) +
+                /* System name */
+                2 + strlen_ptr(hostname) +
+                /* System description */
+                2 + strlen_ptr(pretty_hostname) +
+                /* MUD URL */
+                2 + sizeof(SD_LLDP_OUI_IANA_MUD) + strlen_ptr(lldp_tx->mud_url) +
+                /* System Capabilities */
+                2 + 4 +
+                /* End */
+                2;
+}
+
+static int packet_append_tlv_header(uint8_t *packet, size_t packet_size, size_t *offset, uint8_t type, size_t data_len) {
+        assert(packet);
+        assert(offset);
+
+        /*
+         * +--------+--------+--------------
+         * |TLV Type|  len   |   value
+         * |(7 bits)|(9 bits)|(0-511 octets)
+         * +--------+--------+--------------
+         * where:
+         *
+         * len = indicates the length of value
+         */
+
+        /* The type field is 7-bits. */
+        if (type >= 128)
+                return -EINVAL;
+
+        /* The data length field is 9-bits. */
+        if (data_len >= 512)
+                return -EINVAL;
+
+        if (packet_size < 2 + data_len)
+                return -ENOBUFS;
+
+        if (*offset > packet_size - 2 - data_len)
+                return -ENOBUFS;
+
+        packet[(*offset)++] = (type << 1) | !!(data_len >> 8);
+        packet[(*offset)++] = data_len & (size_t) UINT8_MAX;
+
+        return 0;
+}
+
+static int packet_append_prefixed_string(
+                uint8_t *packet,
+                size_t packet_size,
+                size_t *offset,
+                uint8_t type,
+                size_t prefix_len,
+                const void *prefix,
+                const char *str) {
+
+        size_t len;
+        int r;
+
+        assert(packet);
+        assert(offset);
+        assert(prefix_len == 0 || prefix);
+
+        if (isempty(str))
+                return 0;
+
+        len = strlen(str);
+
+        /* Check for overflow */
+        if (len > SIZE_MAX - prefix_len)
+                return -ENOBUFS;
+
+        r = packet_append_tlv_header(packet, packet_size, offset, type, prefix_len + len);
+        if (r < 0)
+                return r;
+
+        memcpy_safe(packet + *offset, prefix, prefix_len);
+        *offset += prefix_len;
+
+        memcpy(packet + *offset, str, len);
+        *offset += len;
+
+        return 0;
+}
+
+static int packet_append_string(
+                uint8_t *packet,
+                size_t packet_size,
+                size_t *offset,
+                uint8_t type,
+                const char *str) {
+
+        return packet_append_prefixed_string(packet, packet_size, offset, type, 0, NULL, str);
+}
+
+static int lldp_tx_create_packet(sd_lldp_tx *lldp_tx, size_t *ret_packet_size, uint8_t **ret_packet) {
+        _cleanup_free_ char *hostname = NULL, *pretty_hostname = NULL;
+        _cleanup_free_ uint8_t *packet = NULL;
+        struct ether_header *header;
+        size_t packet_size, offset;
+        sd_id128_t machine_id;
+        int r;
+
+        assert(lldp_tx);
+        assert(lldp_tx->ifindex > 0);
+        assert(ret_packet_size);
+        assert(ret_packet);
+
+        /* If ifname is not set yet, set ifname from ifindex. */
+        r = sd_lldp_tx_get_ifname(lldp_tx, NULL);
+        if (r < 0)
+                return r;
+
+        r = sd_id128_get_machine(&machine_id);
+        if (r < 0)
+                return r;
+
+        if (!lldp_tx->hostname)
+                (void) gethostname_strict(&hostname);
+        if (!lldp_tx->pretty_hostname)
+                (void) get_pretty_hostname(&pretty_hostname);
+
+        packet_size = lldp_tx_calculate_maximum_packet_size(lldp_tx,
+                                                            lldp_tx->hostname ?: hostname,
+                                                            lldp_tx->pretty_hostname ?: pretty_hostname);
+
+        packet = new(uint8_t, packet_size);
+        if (!packet)
+                return -ENOMEM;
+
+        header = (struct ether_header*) packet;
+        header->ether_type = htobe16(ETHERTYPE_LLDP);
+        memcpy(header->ether_dhost, lldp_multicast_addr + lldp_tx->mode, ETH_ALEN);
+        memcpy(header->ether_shost, &lldp_tx->hwaddr, ETH_ALEN);
+
+        offset = sizeof(struct ether_header);
+
+        /* The three mandatory TLVs must appear first, in this specific order:
+         *   1. Chassis ID
+         *   2. Port ID
+         *   3. Time To Live
+         */
+
+        r = packet_append_prefixed_string(packet, packet_size, &offset, SD_LLDP_TYPE_CHASSIS_ID,
+                                          1, (const uint8_t[]) { SD_LLDP_CHASSIS_SUBTYPE_LOCALLY_ASSIGNED },
+                                          SD_ID128_TO_STRING(machine_id));
+        if (r < 0)
+                return r;
+
+        r = packet_append_prefixed_string(packet, packet_size, &offset, SD_LLDP_TYPE_PORT_ID,
+                                          1, (const uint8_t[]) { SD_LLDP_PORT_SUBTYPE_INTERFACE_NAME },
+                                          lldp_tx->ifname);
+        if (r < 0)
+                return r;
+
+        r = packet_append_tlv_header(packet, packet_size, &offset, SD_LLDP_TYPE_TTL, 2);
+        if (r < 0)
+                return r;
+
+        unaligned_write_be16(packet + offset, LLDP_TX_TTL);
+        offset += 2;
+
+        /* Optional TLVs follow, in no specific order: */
+
+        r = packet_append_string(packet, packet_size, &offset, SD_LLDP_TYPE_PORT_DESCRIPTION,
+                                 lldp_tx->port_description);
+        if (r < 0)
+                return r;
+
+        r = packet_append_string(packet, packet_size, &offset, SD_LLDP_TYPE_SYSTEM_NAME,
+                                 lldp_tx->hostname ?: hostname);
+        if (r < 0)
+                return r;
+
+        r = packet_append_string(packet, packet_size, &offset, SD_LLDP_TYPE_SYSTEM_DESCRIPTION,
+                                 lldp_tx->pretty_hostname ?: pretty_hostname);
+        if (r < 0)
+                return r;
+
+        /* See section 12 of RFC 8520.
+         * +--------+--------+----------+---------+--------------
+         * |TLV Type|  len   |   OUI    |subtype  | MUDString
+         * |  =127  |        |= 00 00 5E|  = 1    |
+         * |(7 bits)|(9 bits)|(3 octets)|(1 octet)|(1-255 octets)
+         * +--------+--------+----------+---------+--------------
+         * where:
+         *
+         * o  TLV Type = 127 indicates a vendor-specific TLV
+         * o  len = indicates the TLV string length
+         * o  OUI = 00 00 5E is the organizationally unique identifier of IANA
+         * o  subtype = 1 (as assigned by IANA for the MUDstring)
+         * o  MUDstring = the length MUST NOT exceed 255 octets
+         */
+        r = packet_append_prefixed_string(packet, packet_size, &offset, SD_LLDP_TYPE_PRIVATE,
+                                          sizeof(SD_LLDP_OUI_IANA_MUD), SD_LLDP_OUI_IANA_MUD,
+                                          lldp_tx->mud_url);
+        if (r < 0)
+                return r;
+
+        r = packet_append_tlv_header(packet, packet_size, &offset, SD_LLDP_TYPE_SYSTEM_CAPABILITIES, 4);
+        if (r < 0)
+                return r;
+
+        unaligned_write_be16(packet + offset, lldp_tx->supported_capabilities);
+        offset += 2;
+        unaligned_write_be16(packet + offset, lldp_tx->enabled_capabilities);
+        offset += 2;
+
+        r = packet_append_tlv_header(packet, packet_size, &offset, SD_LLDP_TYPE_END, 0);
+        if (r < 0)
+                return r;
+
+        *ret_packet_size = offset;
+        *ret_packet = TAKE_PTR(packet);
+        return 0;
+}
+
+static int lldp_tx_send_packet(sd_lldp_tx *lldp_tx, size_t packet_size, const uint8_t *packet) {
+        _cleanup_close_ int fd = -1;
+        union sockaddr_union sa;
+        ssize_t l;
+
+        assert(lldp_tx);
+        assert(lldp_tx->ifindex > 0);
+        assert(packet_size > sizeof(struct ether_header));
+        assert(packet);
+
+        sa = (union sockaddr_union) {
+                .ll.sll_family = AF_PACKET,
+                .ll.sll_protocol = htobe16(ETHERTYPE_LLDP),
+                .ll.sll_ifindex = lldp_tx->ifindex,
+                .ll.sll_halen = ETH_ALEN,
+        };
+        memcpy(sa.ll.sll_addr, lldp_multicast_addr + lldp_tx->mode, ETH_ALEN);
+
+        fd = socket(AF_PACKET, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_RAW);
+        if (fd < 0)
+                return -errno;
+
+        l = sendto(fd, packet, packet_size, MSG_NOSIGNAL, &sa.sa, sizeof(sa.ll));
+        if (l < 0)
+                return -errno;
+
+        if ((size_t) l != packet_size)
+                return -EIO;
+
+        return 0;
+}
+
+static int lldp_tx_send(sd_lldp_tx *lldp_tx) {
+        _cleanup_free_ uint8_t *packet = NULL;
+        size_t packet_size = 0;  /* avoid false maybe-uninitialized warning */
+        int r;
+
+        assert(lldp_tx);
+
+        r = lldp_tx_create_packet(lldp_tx, &packet_size, &packet);
+        if (r < 0)
+                return r;
+
+        return lldp_tx_send_packet(lldp_tx, packet_size, packet);
+}
+
+int sd_lldp_tx_attach_event(sd_lldp_tx *lldp_tx, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(lldp_tx, -EINVAL);
+        assert_return(!lldp_tx->event, -EBUSY);
+
+        if (event)
+                lldp_tx->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&lldp_tx->event);
+                if (r < 0)
+                        return r;
+        }
+
+        lldp_tx->event_priority = priority;
+
+        return 0;
+}
+
+int sd_lldp_tx_detach_event(sd_lldp_tx *lldp_tx) {
+        assert_return(lldp_tx, -EINVAL);
+
+        lldp_tx->timer_event_source = sd_event_source_disable_unref(lldp_tx->timer_event_source);
+        lldp_tx->event = sd_event_unref(lldp_tx->event);
+        return 0;
+}
+
+static usec_t lldp_tx_get_delay(sd_lldp_tx *lldp_tx) {
+        assert(lldp_tx);
+
+        return usec_add(lldp_tx->fast_tx > 0 ? LLDP_FAST_TX_INTERVAL_USEC : LLDP_TX_INTERVAL_USEC,
+                        (usec_t) random_u64() % LLDP_TX_JITTER_USEC);
+}
+
+static int lldp_tx_reset_timer(sd_lldp_tx *lldp_tx) {
+        usec_t delay;
+        int r;
+
+        assert(lldp_tx);
+        assert(lldp_tx->timer_event_source);
+
+        delay = lldp_tx_get_delay(lldp_tx);
+
+        r = sd_event_source_set_time_relative(lldp_tx->timer_event_source, delay);
+        if (r < 0)
+                return r;
+
+        return sd_event_source_set_enabled(lldp_tx->timer_event_source, SD_EVENT_ONESHOT);
+}
+
+static int on_timer_event(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_lldp_tx *lldp_tx = ASSERT_PTR(userdata);
+        int r;
+
+        r = lldp_tx_send(lldp_tx);
+        if (r < 0)
+                log_lldp_tx_errno(lldp_tx, r, "Failed to send packet, ignoring: %m");
+
+        if (lldp_tx->fast_tx > 0)
+                lldp_tx->fast_tx--;
+
+        r = lldp_tx_reset_timer(lldp_tx);
+        if (r < 0)
+                log_lldp_tx_errno(lldp_tx, r, "Failed to reset timer: %m");
+
+        return 0;
+}
+
+int sd_lldp_tx_is_running(sd_lldp_tx *lldp_tx) {
+        int enabled;
+
+        if (!lldp_tx)
+                return 0;
+
+        if (!lldp_tx->timer_event_source)
+                return 0;
+
+        if (sd_event_source_get_enabled(lldp_tx->timer_event_source, &enabled) < 0)
+                return 0;
+
+        return enabled == SD_EVENT_ONESHOT;
+}
+
+int sd_lldp_tx_stop(sd_lldp_tx *lldp_tx) {
+        if (!lldp_tx)
+                return 0;
+
+        if (!lldp_tx->timer_event_source)
+                return 0;
+
+        (void) sd_event_source_set_enabled(lldp_tx->timer_event_source, SD_EVENT_OFF);
+
+        return 1;
+}
+int sd_lldp_tx_start(sd_lldp_tx *lldp_tx) {
+        usec_t delay;
+        int r;
+
+        assert_return(lldp_tx, -EINVAL);
+        assert_return(lldp_tx->event, -EINVAL);
+        assert_return(lldp_tx->ifindex > 0, -EINVAL);
+        assert_return(lldp_tx->mode >= 0 && lldp_tx->mode < _SD_LLDP_MULTICAST_MODE_MAX, -EINVAL);
+        assert_return(!ether_addr_is_null(&lldp_tx->hwaddr), -EINVAL);
+
+        if (sd_lldp_tx_is_running(lldp_tx))
+                return 0;
+
+        lldp_tx->fast_tx = LLDP_FAST_TX_INIT;
+
+        if (lldp_tx->timer_event_source) {
+                r = lldp_tx_reset_timer(lldp_tx);
+                if (r < 0)
+                        return log_lldp_tx_errno(lldp_tx, r, "Failed to re-enable timer: %m");
+
+                return 0;
+        }
+
+        delay = lldp_tx_get_delay(lldp_tx);
+
+        r = sd_event_add_time_relative(lldp_tx->event, &lldp_tx->timer_event_source,
+                                       CLOCK_BOOTTIME, delay, 0,
+                                       on_timer_event, lldp_tx);
+        if (r < 0)
+                return r;
+
+        (void) sd_event_source_set_description(lldp_tx->timer_event_source, "lldp-tx-timer");
+        (void) sd_event_source_set_priority(lldp_tx->timer_event_source, lldp_tx->event_priority);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/sd-ndisc.c b/src/libsystemd-network/sd-ndisc.c
new file mode 100644
index 0000000..111fcac
--- /dev/null
+++ b/src/libsystemd-network/sd-ndisc.c
@@ -0,0 +1,386 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include <netinet/icmp6.h>
+#include <netinet/in.h>
+
+#include "sd-ndisc.h"
+
+#include "alloc-util.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "icmp6-util.h"
+#include "in-addr-util.h"
+#include "memory-util.h"
+#include "ndisc-internal.h"
+#include "ndisc-router.h"
+#include "network-common.h"
+#include "random-util.h"
+#include "socket-util.h"
+#include "string-table.h"
+#include "string-util.h"
+
+#define NDISC_TIMEOUT_NO_RA_USEC (NDISC_ROUTER_SOLICITATION_INTERVAL * NDISC_MAX_ROUTER_SOLICITATIONS)
+
+static const char * const ndisc_event_table[_SD_NDISC_EVENT_MAX] = {
+        [SD_NDISC_EVENT_TIMEOUT] = "timeout",
+        [SD_NDISC_EVENT_ROUTER] = "router",
+};
+
+DEFINE_STRING_TABLE_LOOKUP(ndisc_event, sd_ndisc_event_t);
+
+static void ndisc_callback(sd_ndisc *ndisc, sd_ndisc_event_t event, sd_ndisc_router *rt) {
+        assert(ndisc);
+        assert(event >= 0 && event < _SD_NDISC_EVENT_MAX);
+
+        if (!ndisc->callback)
+                return (void) log_ndisc(ndisc, "Received '%s' event.", ndisc_event_to_string(event));
+
+        log_ndisc(ndisc, "Invoking callback for '%s' event.", ndisc_event_to_string(event));
+        ndisc->callback(ndisc, event, rt, ndisc->userdata);
+}
+
+int sd_ndisc_set_callback(
+                sd_ndisc *nd,
+                sd_ndisc_callback_t callback,
+                void *userdata) {
+
+        assert_return(nd, -EINVAL);
+
+        nd->callback = callback;
+        nd->userdata = userdata;
+
+        return 0;
+}
+
+int sd_ndisc_set_ifindex(sd_ndisc *nd, int ifindex) {
+        assert_return(nd, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+        assert_return(nd->fd < 0, -EBUSY);
+
+        nd->ifindex = ifindex;
+        return 0;
+}
+
+int sd_ndisc_set_ifname(sd_ndisc *nd, const char *ifname) {
+        assert_return(nd, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&nd->ifname, ifname);
+}
+
+int sd_ndisc_get_ifname(sd_ndisc *nd, const char **ret) {
+        int r;
+
+        assert_return(nd, -EINVAL);
+
+        r = get_ifname(nd->ifindex, &nd->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = nd->ifname;
+
+        return 0;
+}
+
+int sd_ndisc_set_mac(sd_ndisc *nd, const struct ether_addr *mac_addr) {
+        assert_return(nd, -EINVAL);
+
+        if (mac_addr)
+                nd->mac_addr = *mac_addr;
+        else
+                zero(nd->mac_addr);
+
+        return 0;
+}
+
+int sd_ndisc_attach_event(sd_ndisc *nd, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(nd, -EINVAL);
+        assert_return(nd->fd < 0, -EBUSY);
+        assert_return(!nd->event, -EBUSY);
+
+        if (event)
+                nd->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&nd->event);
+                if (r < 0)
+                        return 0;
+        }
+
+        nd->event_priority = priority;
+
+        return 0;
+}
+
+int sd_ndisc_detach_event(sd_ndisc *nd) {
+
+        assert_return(nd, -EINVAL);
+        assert_return(nd->fd < 0, -EBUSY);
+
+        nd->event = sd_event_unref(nd->event);
+        return 0;
+}
+
+sd_event *sd_ndisc_get_event(sd_ndisc *nd) {
+        assert_return(nd, NULL);
+
+        return nd->event;
+}
+
+static void ndisc_reset(sd_ndisc *nd) {
+        assert(nd);
+
+        (void) event_source_disable(nd->timeout_event_source);
+        (void) event_source_disable(nd->timeout_no_ra);
+        nd->retransmit_time = 0;
+        nd->recv_event_source = sd_event_source_disable_unref(nd->recv_event_source);
+        nd->fd = safe_close(nd->fd);
+}
+
+static sd_ndisc *ndisc_free(sd_ndisc *nd) {
+        assert(nd);
+
+        ndisc_reset(nd);
+
+        sd_event_source_unref(nd->timeout_event_source);
+        sd_event_source_unref(nd->timeout_no_ra);
+        sd_ndisc_detach_event(nd);
+
+        free(nd->ifname);
+        return mfree(nd);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_ndisc, sd_ndisc, ndisc_free);
+
+int sd_ndisc_new(sd_ndisc **ret) {
+        _cleanup_(sd_ndisc_unrefp) sd_ndisc *nd = NULL;
+
+        assert_return(ret, -EINVAL);
+
+        nd = new(sd_ndisc, 1);
+        if (!nd)
+                return -ENOMEM;
+
+        *nd = (sd_ndisc) {
+                .n_ref = 1,
+                .fd = -1,
+        };
+
+        *ret = TAKE_PTR(nd);
+
+        return 0;
+}
+
+static int ndisc_handle_datagram(sd_ndisc *nd, sd_ndisc_router *rt) {
+        int r;
+
+        assert(nd);
+        assert(rt);
+
+        r = ndisc_router_parse(nd, rt);
+        if (r < 0)
+                return r;
+
+        log_ndisc(nd, "Received Router Advertisement: flags %s preference %s lifetime %" PRIu16 " sec",
+                  rt->flags & ND_RA_FLAG_MANAGED ? "MANAGED" : rt->flags & ND_RA_FLAG_OTHER ? "OTHER" : "none",
+                  rt->preference == SD_NDISC_PREFERENCE_HIGH ? "high" : rt->preference == SD_NDISC_PREFERENCE_LOW ? "low" : "medium",
+                  rt->lifetime);
+
+        ndisc_callback(nd, SD_NDISC_EVENT_ROUTER, rt);
+        return 0;
+}
+
+static int ndisc_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        _cleanup_(sd_ndisc_router_unrefp) sd_ndisc_router *rt = NULL;
+        sd_ndisc *nd = ASSERT_PTR(userdata);
+        ssize_t buflen;
+        int r;
+
+        assert(s);
+        assert(nd->event);
+
+        buflen = next_datagram_size_fd(fd);
+        if (buflen < 0) {
+                if (ERRNO_IS_TRANSIENT(buflen) || ERRNO_IS_DISCONNECT(buflen))
+                        return 0;
+
+                log_ndisc_errno(nd, buflen, "Failed to determine datagram size to read, ignoring: %m");
+                return 0;
+        }
+
+        rt = ndisc_router_new(buflen);
+        if (!rt)
+                return -ENOMEM;
+
+        r = icmp6_receive(fd, NDISC_ROUTER_RAW(rt), rt->raw_size, &rt->address, &rt->timestamp);
+        if (r < 0) {
+                if (ERRNO_IS_TRANSIENT(r) || ERRNO_IS_DISCONNECT(r))
+                        return 0;
+
+                switch (r) {
+                case -EADDRNOTAVAIL:
+                        log_ndisc(nd, "Received RA from neither link-local nor null address. Ignoring.");
+                        break;
+
+                case -EMULTIHOP:
+                        log_ndisc(nd, "Received RA with invalid hop limit. Ignoring.");
+                        break;
+
+                case -EPFNOSUPPORT:
+                        log_ndisc(nd, "Received invalid source address from ICMPv6 socket. Ignoring.");
+                        break;
+
+                default:
+                        log_ndisc_errno(nd, r, "Unexpected error while reading from ICMPv6, ignoring: %m");
+                        break;
+                }
+
+                return 0;
+        }
+
+        /* The function icmp6_receive() accepts the null source address, but RFC 4861 Section 6.1.2 states
+         * that hosts MUST discard messages with the null source address. */
+        if (in6_addr_is_null(&rt->address))
+                log_ndisc(nd, "Received RA from null address. Ignoring.");
+
+        (void) event_source_disable(nd->timeout_event_source);
+        (void) ndisc_handle_datagram(nd, rt);
+        return 0;
+}
+
+static usec_t ndisc_timeout_compute_random(usec_t val) {
+        /* compute a time that is random within ±10% of the given value */
+        return val - val / 10 +
+                (random_u64() % (2 * USEC_PER_SEC)) * val / 10 / USEC_PER_SEC;
+}
+
+static int ndisc_timeout(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_ndisc *nd = ASSERT_PTR(userdata);
+        usec_t time_now;
+        int r;
+
+        assert(s);
+        assert(nd->event);
+
+        assert_se(sd_event_now(nd->event, CLOCK_BOOTTIME, &time_now) >= 0);
+
+        if (!nd->retransmit_time)
+                nd->retransmit_time = ndisc_timeout_compute_random(NDISC_ROUTER_SOLICITATION_INTERVAL);
+        else {
+                if (nd->retransmit_time > NDISC_MAX_ROUTER_SOLICITATION_INTERVAL / 2)
+                        nd->retransmit_time = ndisc_timeout_compute_random(NDISC_MAX_ROUTER_SOLICITATION_INTERVAL);
+                else
+                        nd->retransmit_time += ndisc_timeout_compute_random(nd->retransmit_time);
+        }
+
+        r = event_reset_time(nd->event, &nd->timeout_event_source,
+                             CLOCK_BOOTTIME,
+                             time_now + nd->retransmit_time, 10 * USEC_PER_MSEC,
+                             ndisc_timeout, nd,
+                             nd->event_priority, "ndisc-timeout-no-ra", true);
+        if (r < 0)
+                goto fail;
+
+        r = icmp6_send_router_solicitation(nd->fd, &nd->mac_addr);
+        if (r < 0)
+                log_ndisc_errno(nd, r, "Failed to send Router Solicitation, next solicitation in %s, ignoring: %m",
+                                FORMAT_TIMESPAN(nd->retransmit_time, USEC_PER_SEC));
+        else
+                log_ndisc(nd, "Sent Router Solicitation, next solicitation in %s",
+                          FORMAT_TIMESPAN(nd->retransmit_time, USEC_PER_SEC));
+
+        return 0;
+
+fail:
+        (void) sd_ndisc_stop(nd);
+        return 0;
+}
+
+static int ndisc_timeout_no_ra(sd_event_source *s, uint64_t usec, void *userdata) {
+        sd_ndisc *nd = ASSERT_PTR(userdata);
+
+        assert(s);
+
+        log_ndisc(nd, "No RA received before link confirmation timeout");
+
+        (void) event_source_disable(nd->timeout_no_ra);
+        ndisc_callback(nd, SD_NDISC_EVENT_TIMEOUT, NULL);
+
+        return 0;
+}
+
+int sd_ndisc_stop(sd_ndisc *nd) {
+        if (!nd)
+                return 0;
+
+        if (nd->fd < 0)
+                return 0;
+
+        log_ndisc(nd, "Stopping IPv6 Router Solicitation client");
+
+        ndisc_reset(nd);
+        return 1;
+}
+
+int sd_ndisc_start(sd_ndisc *nd) {
+        int r;
+        usec_t time_now;
+
+        assert_return(nd, -EINVAL);
+        assert_return(nd->event, -EINVAL);
+        assert_return(nd->ifindex > 0, -EINVAL);
+
+        if (nd->fd >= 0)
+                return 0;
+
+        assert(!nd->recv_event_source);
+
+        r = sd_event_now(nd->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                goto fail;
+
+        nd->fd = icmp6_bind_router_solicitation(nd->ifindex);
+        if (nd->fd < 0)
+                return nd->fd;
+
+        r = sd_event_add_io(nd->event, &nd->recv_event_source, nd->fd, EPOLLIN, ndisc_recv, nd);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_priority(nd->recv_event_source, nd->event_priority);
+        if (r < 0)
+                goto fail;
+
+        (void) sd_event_source_set_description(nd->recv_event_source, "ndisc-receive-message");
+
+        r = event_reset_time(nd->event, &nd->timeout_event_source,
+                             CLOCK_BOOTTIME,
+                             time_now + USEC_PER_SEC / 2, 1 * USEC_PER_SEC, /* See RFC 8415 sec. 18.2.1 */
+                             ndisc_timeout, nd,
+                             nd->event_priority, "ndisc-timeout", true);
+        if (r < 0)
+                goto fail;
+
+        r = event_reset_time(nd->event, &nd->timeout_no_ra,
+                             CLOCK_BOOTTIME,
+                             time_now + NDISC_TIMEOUT_NO_RA_USEC, 10 * USEC_PER_MSEC,
+                             ndisc_timeout_no_ra, nd,
+                             nd->event_priority, "ndisc-timeout-no-ra", true);
+        if (r < 0)
+                goto fail;
+
+        log_ndisc(nd, "Started IPv6 Router Solicitation client");
+        return 1;
+
+fail:
+        ndisc_reset(nd);
+        return r;
+}
diff --git a/src/libsystemd-network/sd-radv.c b/src/libsystemd-network/sd-radv.c
new file mode 100644
index 0000000..61f52d5
--- /dev/null
+++ b/src/libsystemd-network/sd-radv.c
@@ -0,0 +1,991 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2017 Intel Corporation. All rights reserved.
+***/
+
+#include <netinet/icmp6.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+#include "sd-radv.h"
+
+#include "alloc-util.h"
+#include "dns-domain.h"
+#include "ether-addr-util.h"
+#include "event-util.h"
+#include "fd-util.h"
+#include "icmp6-util.h"
+#include "in-addr-util.h"
+#include "io-util.h"
+#include "macro.h"
+#include "memory-util.h"
+#include "network-common.h"
+#include "radv-internal.h"
+#include "random-util.h"
+#include "socket-util.h"
+#include "string-util.h"
+#include "strv.h"
+
+int sd_radv_new(sd_radv **ret) {
+        _cleanup_(sd_radv_unrefp) sd_radv *ra = NULL;
+
+        assert_return(ret, -EINVAL);
+
+        ra = new(sd_radv, 1);
+        if (!ra)
+                return -ENOMEM;
+
+        *ra = (sd_radv) {
+                .n_ref = 1,
+                .fd = -1,
+                .lifetime_usec = RADV_DEFAULT_ROUTER_LIFETIME_USEC,
+        };
+
+        *ret = TAKE_PTR(ra);
+
+        return 0;
+}
+
+int sd_radv_attach_event(sd_radv *ra, sd_event *event, int64_t priority) {
+        int r;
+
+        assert_return(ra, -EINVAL);
+        assert_return(!ra->event, -EBUSY);
+
+        if (event)
+                ra->event = sd_event_ref(event);
+        else {
+                r = sd_event_default(&ra->event);
+                if (r < 0)
+                        return 0;
+        }
+
+        ra->event_priority = priority;
+
+        return 0;
+}
+
+int sd_radv_detach_event(sd_radv *ra) {
+
+        assert_return(ra, -EINVAL);
+
+        ra->event = sd_event_unref(ra->event);
+        return 0;
+}
+
+sd_event *sd_radv_get_event(sd_radv *ra) {
+        assert_return(ra, NULL);
+
+        return ra->event;
+}
+
+int sd_radv_is_running(sd_radv *ra) {
+        assert_return(ra, false);
+
+        return ra->state != RADV_STATE_IDLE;
+}
+
+static void radv_reset(sd_radv *ra) {
+        assert(ra);
+
+        (void) event_source_disable(ra->timeout_event_source);
+
+        ra->recv_event_source = sd_event_source_disable_unref(ra->recv_event_source);
+
+        ra->ra_sent = 0;
+}
+
+static sd_radv *radv_free(sd_radv *ra) {
+        if (!ra)
+                return NULL;
+
+        while (ra->prefixes) {
+                sd_radv_prefix *p = ra->prefixes;
+
+                LIST_REMOVE(prefix, ra->prefixes, p);
+                sd_radv_prefix_unref(p);
+        }
+
+        while (ra->route_prefixes) {
+                sd_radv_route_prefix *p = ra->route_prefixes;
+
+                LIST_REMOVE(prefix, ra->route_prefixes, p);
+                sd_radv_route_prefix_unref(p);
+        }
+
+        free(ra->rdnss);
+        free(ra->dnssl);
+
+        radv_reset(ra);
+
+        sd_event_source_unref(ra->timeout_event_source);
+        sd_radv_detach_event(ra);
+
+        ra->fd = safe_close(ra->fd);
+        free(ra->ifname);
+
+        return mfree(ra);
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_radv, sd_radv, radv_free);
+
+static bool router_lifetime_is_valid(usec_t lifetime_usec) {
+        return lifetime_usec == 0 ||
+                (lifetime_usec >= RADV_MIN_ROUTER_LIFETIME_USEC &&
+                 lifetime_usec <= RADV_MAX_ROUTER_LIFETIME_USEC);
+}
+
+static be32_t usec_to_be32_sec(usec_t usec) {
+        if (usec == USEC_INFINITY)
+                /* UINT32_MAX is handled as infinity. */
+                return htobe32(UINT32_MAX);
+
+        if (usec >= UINT32_MAX * USEC_PER_SEC)
+                /* Finite but too large. Let's use the largest finite value. */
+                return htobe32(UINT32_MAX - 1);
+
+        return htobe32(usec / USEC_PER_SEC);
+}
+
+static int radv_send(sd_radv *ra, const struct in6_addr *dst, usec_t lifetime_usec) {
+        struct sockaddr_in6 dst_addr = {
+                .sin6_family = AF_INET6,
+                .sin6_addr = IN6ADDR_ALL_NODES_MULTICAST_INIT,
+        };
+        struct nd_router_advert adv = {};
+        struct {
+                struct nd_opt_hdr opthdr;
+                struct ether_addr slladdr;
+        } _packed_ opt_mac = {
+                .opthdr = {
+                        .nd_opt_type = ND_OPT_SOURCE_LINKADDR,
+                        .nd_opt_len = (sizeof(struct nd_opt_hdr) +
+                                       sizeof(struct ether_addr) - 1) /8 + 1,
+                },
+        };
+        struct nd_opt_mtu opt_mtu =  {
+                .nd_opt_mtu_type = ND_OPT_MTU,
+                .nd_opt_mtu_len = 1,
+        };
+        /* Reserve iov space for RA header, linkaddr, MTU, N prefixes, N routes, RDNSS
+           and DNSSL */
+        struct iovec iov[5 + ra->n_prefixes + ra->n_route_prefixes];
+        struct msghdr msg = {
+                .msg_name = &dst_addr,
+                .msg_namelen = sizeof(dst_addr),
+                .msg_iov = iov,
+        };
+        usec_t time_now;
+        int r;
+
+        assert(ra);
+        assert(router_lifetime_is_valid(lifetime_usec));
+
+        r = sd_event_now(ra->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                return r;
+
+        if (dst && in6_addr_is_set(dst))
+                dst_addr.sin6_addr = *dst;
+
+        adv.nd_ra_type = ND_ROUTER_ADVERT;
+        adv.nd_ra_curhoplimit = ra->hop_limit;
+        adv.nd_ra_flags_reserved = ra->flags;
+        assert_cc(RADV_MAX_ROUTER_LIFETIME_USEC <= UINT16_MAX * USEC_PER_SEC);
+        adv.nd_ra_router_lifetime = htobe16(DIV_ROUND_UP(lifetime_usec, USEC_PER_SEC));
+        iov[msg.msg_iovlen++] = IOVEC_MAKE(&adv, sizeof(adv));
+
+        /* MAC address is optional, either because the link does not use L2
+           addresses or load sharing is desired. See RFC 4861, Section 4.2 */
+        if (!ether_addr_is_null(&ra->mac_addr)) {
+                opt_mac.slladdr = ra->mac_addr;
+                iov[msg.msg_iovlen++] = IOVEC_MAKE(&opt_mac, sizeof(opt_mac));
+        }
+
+        if (ra->mtu > 0) {
+                opt_mtu.nd_opt_mtu_mtu = htobe32(ra->mtu);
+                iov[msg.msg_iovlen++] = IOVEC_MAKE(&opt_mtu, sizeof(opt_mtu));
+        }
+
+        LIST_FOREACH(prefix, p, ra->prefixes) {
+                usec_t lifetime_valid_usec, lifetime_preferred_usec;
+
+                lifetime_valid_usec = MIN(usec_sub_unsigned(p->valid_until, time_now),
+                                          p->lifetime_valid_usec);
+
+                lifetime_preferred_usec = MIN3(usec_sub_unsigned(p->preferred_until, time_now),
+                                               p->lifetime_preferred_usec,
+                                               lifetime_valid_usec);
+
+                p->opt.lifetime_valid = usec_to_be32_sec(lifetime_valid_usec);
+                p->opt.lifetime_preferred = usec_to_be32_sec(lifetime_preferred_usec);
+
+                iov[msg.msg_iovlen++] = IOVEC_MAKE(&p->opt, sizeof(p->opt));
+        }
+
+        LIST_FOREACH(prefix, rt, ra->route_prefixes) {
+                rt->opt.lifetime = usec_to_be32_sec(MIN(usec_sub_unsigned(rt->valid_until, time_now),
+                                                        rt->lifetime_usec));
+
+                iov[msg.msg_iovlen++] = IOVEC_MAKE(&rt->opt, sizeof(rt->opt));
+        }
+
+        if (ra->rdnss)
+                iov[msg.msg_iovlen++] = IOVEC_MAKE(ra->rdnss, ra->rdnss->length * 8);
+
+        if (ra->dnssl)
+                iov[msg.msg_iovlen++] = IOVEC_MAKE(ra->dnssl, ra->dnssl->length * 8);
+
+        if (sendmsg(ra->fd, &msg, 0) < 0)
+                return -errno;
+
+        return 0;
+}
+
+static int radv_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        sd_radv *ra = ASSERT_PTR(userdata);
+        struct in6_addr src;
+        triple_timestamp timestamp;
+        int r;
+
+        assert(s);
+        assert(ra->event);
+
+        ssize_t buflen = next_datagram_size_fd(fd);
+        if (buflen < 0) {
+                if (ERRNO_IS_TRANSIENT(buflen) || ERRNO_IS_DISCONNECT(buflen))
+                        return 0;
+
+                log_radv_errno(ra, buflen, "Failed to determine datagram size to read, ignoring: %m");
+                return 0;
+        }
+
+        _cleanup_free_ char *buf = new0(char, buflen);
+        if (!buf)
+                return -ENOMEM;
+
+        r = icmp6_receive(fd, buf, buflen, &src, &timestamp);
+        if (r < 0) {
+                if (ERRNO_IS_TRANSIENT(r) || ERRNO_IS_DISCONNECT(r))
+                        return 0;
+
+                switch (r) {
+                case -EADDRNOTAVAIL:
+                        log_radv(ra, "Received RS from neither link-local nor null address. Ignoring");
+                        break;
+
+                case -EMULTIHOP:
+                        log_radv(ra, "Received RS with invalid hop limit. Ignoring.");
+                        break;
+
+                case -EPFNOSUPPORT:
+                        log_radv(ra, "Received invalid source address from ICMPv6 socket. Ignoring.");
+                        break;
+
+                default:
+                        log_radv_errno(ra, r, "Unexpected error receiving from ICMPv6 socket, ignoring: %m");
+                        break;
+                }
+
+                return 0;
+        }
+
+        if ((size_t) buflen < sizeof(struct nd_router_solicit)) {
+                log_radv(ra, "Too short packet received, ignoring");
+                return 0;
+        }
+
+        /* TODO: if the sender address is null, check that the message does not have the source link-layer
+         * address option. See RFC 4861 Section 6.1.1. */
+
+        const char *addr = IN6_ADDR_TO_STRING(&src);
+
+        r = radv_send(ra, &src, ra->lifetime_usec);
+        if (r < 0)
+                log_radv_errno(ra, r, "Unable to send solicited Router Advertisement to %s, ignoring: %m", addr);
+        else
+                log_radv(ra, "Sent solicited Router Advertisement to %s", addr);
+
+        return 0;
+}
+
+static int radv_timeout(sd_event_source *s, uint64_t usec, void *userdata) {
+        usec_t min_timeout, max_timeout, time_now, timeout;
+        sd_radv *ra = ASSERT_PTR(userdata);
+        int r;
+
+        assert(s);
+        assert(ra->event);
+        assert(router_lifetime_is_valid(ra->lifetime_usec));
+
+        r = sd_event_now(ra->event, CLOCK_BOOTTIME, &time_now);
+        if (r < 0)
+                goto fail;
+
+        r = radv_send(ra, NULL, ra->lifetime_usec);
+        if (r < 0)
+                log_radv_errno(ra, r, "Unable to send Router Advertisement, ignoring: %m");
+
+        /* RFC 4861, Section 6.2.4, sending initial Router Advertisements */
+        if (ra->ra_sent < RADV_MAX_INITIAL_RTR_ADVERTISEMENTS)
+                max_timeout = RADV_MAX_INITIAL_RTR_ADVERT_INTERVAL_USEC;
+        else
+                max_timeout = RADV_DEFAULT_MAX_TIMEOUT_USEC;
+
+        /* RFC 4861, Section 6.2.1, lifetime must be at least MaxRtrAdvInterval,
+         * so lower the interval here */
+        if (ra->lifetime_usec > 0)
+                max_timeout = MIN(max_timeout, ra->lifetime_usec);
+
+        if (max_timeout >= 9 * USEC_PER_SEC)
+                min_timeout = max_timeout / 3;
+        else
+                min_timeout = max_timeout * 3 / 4;
+
+        /* RFC 4861, Section 6.2.1.
+         * MaxRtrAdvInterval MUST be no less than 4 seconds and no greater than 1800 seconds.
+         * MinRtrAdvInterval MUST be no less than 3 seconds and no greater than .75 * MaxRtrAdvInterval. */
+        assert(max_timeout >= RADV_MIN_MAX_TIMEOUT_USEC);
+        assert(max_timeout <= RADV_MAX_MAX_TIMEOUT_USEC);
+        assert(min_timeout >= RADV_MIN_MIN_TIMEOUT_USEC);
+        assert(min_timeout <= max_timeout * 3 / 4);
+
+        timeout = min_timeout + random_u64_range(max_timeout - min_timeout);
+        log_radv(ra, "Next Router Advertisement in %s", FORMAT_TIMESPAN(timeout, USEC_PER_SEC));
+
+        r = event_reset_time(ra->event, &ra->timeout_event_source,
+                             CLOCK_BOOTTIME,
+                             usec_add(time_now, timeout), MSEC_PER_SEC,
+                             radv_timeout, ra,
+                             ra->event_priority, "radv-timeout", true);
+        if (r < 0)
+                goto fail;
+
+        ra->ra_sent++;
+
+        return 0;
+
+fail:
+        sd_radv_stop(ra);
+
+        return 0;
+}
+
+int sd_radv_stop(sd_radv *ra) {
+        int r;
+
+        if (!ra)
+                return 0;
+
+        if (ra->state == RADV_STATE_IDLE)
+                return 0;
+
+        log_radv(ra, "Stopping IPv6 Router Advertisement daemon");
+
+        /* RFC 4861, Section 6.2.5, send at least one Router Advertisement
+           with zero lifetime  */
+        r = radv_send(ra, NULL, 0);
+        if (r < 0)
+                log_radv_errno(ra, r, "Unable to send last Router Advertisement with router lifetime set to zero, ignoring: %m");
+
+        radv_reset(ra);
+        ra->fd = safe_close(ra->fd);
+        ra->state = RADV_STATE_IDLE;
+
+        return 0;
+}
+
+int sd_radv_start(sd_radv *ra) {
+        int r;
+
+        assert_return(ra, -EINVAL);
+        assert_return(ra->event, -EINVAL);
+        assert_return(ra->ifindex > 0, -EINVAL);
+
+        if (ra->state != RADV_STATE_IDLE)
+                return 0;
+
+        r = event_reset_time(ra->event, &ra->timeout_event_source,
+                             CLOCK_BOOTTIME,
+                             0, 0,
+                             radv_timeout, ra,
+                             ra->event_priority, "radv-timeout", true);
+        if (r < 0)
+                goto fail;
+
+        r = icmp6_bind_router_advertisement(ra->ifindex);
+        if (r < 0)
+                goto fail;
+
+        ra->fd = r;
+
+        r = sd_event_add_io(ra->event, &ra->recv_event_source, ra->fd, EPOLLIN, radv_recv, ra);
+        if (r < 0)
+                goto fail;
+
+        r = sd_event_source_set_priority(ra->recv_event_source, ra->event_priority);
+        if (r < 0)
+                goto fail;
+
+        (void) sd_event_source_set_description(ra->recv_event_source, "radv-receive-message");
+
+        ra->state = RADV_STATE_ADVERTISING;
+
+        log_radv(ra, "Started IPv6 Router Advertisement daemon");
+
+        return 0;
+
+ fail:
+        radv_reset(ra);
+
+        return r;
+}
+
+int sd_radv_set_ifindex(sd_radv *ra, int ifindex) {
+        assert_return(ra, -EINVAL);
+        assert_return(ifindex > 0, -EINVAL);
+
+        if (ra->state != RADV_STATE_IDLE)
+                return -EBUSY;
+
+        ra->ifindex = ifindex;
+
+        return 0;
+}
+
+int sd_radv_set_ifname(sd_radv *ra, const char *ifname) {
+        assert_return(ra, -EINVAL);
+        assert_return(ifname, -EINVAL);
+
+        if (!ifname_valid_full(ifname, IFNAME_VALID_ALTERNATIVE))
+                return -EINVAL;
+
+        return free_and_strdup(&ra->ifname, ifname);
+}
+
+int sd_radv_get_ifname(sd_radv *ra, const char **ret) {
+        int r;
+
+        assert_return(ra, -EINVAL);
+
+        r = get_ifname(ra->ifindex, &ra->ifname);
+        if (r < 0)
+                return r;
+
+        if (ret)
+                *ret = ra->ifname;
+
+        return 0;
+}
+
+int sd_radv_set_mac(sd_radv *ra, const struct ether_addr *mac_addr) {
+        assert_return(ra, -EINVAL);
+
+        if (ra->state != RADV_STATE_IDLE)
+                return -EBUSY;
+
+        if (mac_addr)
+                ra->mac_addr = *mac_addr;
+        else
+                zero(ra->mac_addr);
+
+        return 0;
+}
+
+int sd_radv_set_mtu(sd_radv *ra, uint32_t mtu) {
+        assert_return(ra, -EINVAL);
+        assert_return(mtu >= 1280, -EINVAL);
+
+        ra->mtu = mtu;
+
+        return 0;
+}
+
+int sd_radv_set_hop_limit(sd_radv *ra, uint8_t hop_limit) {
+        assert_return(ra, -EINVAL);
+
+        if (ra->state != RADV_STATE_IDLE)
+                return -EBUSY;
+
+        ra->hop_limit = hop_limit;
+
+        return 0;
+}
+
+int sd_radv_set_router_lifetime(sd_radv *ra, uint64_t lifetime_usec) {
+        assert_return(ra, -EINVAL);
+
+        if (ra->state != RADV_STATE_IDLE)
+                return -EBUSY;
+
+        if (!router_lifetime_is_valid(lifetime_usec))
+                return -EINVAL;
+
+        /* RFC 4191, Section 2.2, "...If the Router Lifetime is zero, the preference value MUST be set
+         * to (00) by the sender..." */
+        if (lifetime_usec == 0 &&
+            (ra->flags & (0x3 << 3)) != (SD_NDISC_PREFERENCE_MEDIUM << 3))
+                return -EINVAL;
+
+        ra->lifetime_usec = lifetime_usec;
+
+        return 0;
+}
+
+int sd_radv_set_managed_information(sd_radv *ra, int managed) {
+        assert_return(ra, -EINVAL);
+
+        if (ra->state != RADV_STATE_IDLE)
+                return -EBUSY;
+
+        SET_FLAG(ra->flags, ND_RA_FLAG_MANAGED, managed);
+
+        return 0;
+}
+
+int sd_radv_set_other_information(sd_radv *ra, int other) {
+        assert_return(ra, -EINVAL);
+
+        if (ra->state != RADV_STATE_IDLE)
+                return -EBUSY;
+
+        SET_FLAG(ra->flags, ND_RA_FLAG_OTHER, other);
+
+        return 0;
+}
+
+int sd_radv_set_preference(sd_radv *ra, unsigned preference) {
+        assert_return(ra, -EINVAL);
+        assert_return(IN_SET(preference,
+                             SD_NDISC_PREFERENCE_LOW,
+                             SD_NDISC_PREFERENCE_MEDIUM,
+                             SD_NDISC_PREFERENCE_HIGH), -EINVAL);
+
+        /* RFC 4191, Section 2.2, "...If the Router Lifetime is zero, the preference value MUST be set
+         * to (00) by the sender..." */
+        if (ra->lifetime_usec == 0 && preference != SD_NDISC_PREFERENCE_MEDIUM)
+                return -EINVAL;
+
+        ra->flags = (ra->flags & ~(0x3 << 3)) | (preference << 3);
+
+        return 0;
+}
+
+int sd_radv_add_prefix(sd_radv *ra, sd_radv_prefix *p) {
+        sd_radv_prefix *found = NULL;
+        int r;
+
+        assert_return(ra, -EINVAL);
+        assert_return(p, -EINVAL);
+
+        /* Refuse prefixes that don't have a prefix set */
+        if (in6_addr_is_null(&p->opt.in6_addr))
+                return -ENOEXEC;
+
+        const char *addr_p = IN6_ADDR_PREFIX_TO_STRING(&p->opt.in6_addr, p->opt.prefixlen);
+
+        LIST_FOREACH(prefix, cur, ra->prefixes) {
+                r = in_addr_prefix_intersect(AF_INET6,
+                                             (const union in_addr_union*) &cur->opt.in6_addr,
+                                             cur->opt.prefixlen,
+                                             (const union in_addr_union*) &p->opt.in6_addr,
+                                             p->opt.prefixlen);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                if (cur->opt.prefixlen == p->opt.prefixlen) {
+                        found = cur;
+                        break;
+                }
+
+                return log_radv_errno(ra, SYNTHETIC_ERRNO(EEXIST),
+                                      "IPv6 prefix %s conflicts with %s, ignoring.",
+                                      addr_p,
+                                      IN6_ADDR_PREFIX_TO_STRING(&cur->opt.in6_addr, cur->opt.prefixlen));
+        }
+
+        if (found) {
+                /* p and cur may be equivalent. First increment the reference counter. */
+                sd_radv_prefix_ref(p);
+
+                /* Then, remove the old entry. */
+                LIST_REMOVE(prefix, ra->prefixes, found);
+                sd_radv_prefix_unref(found);
+
+                /* Finally, add the new entry. */
+                LIST_APPEND(prefix, ra->prefixes, p);
+
+                log_radv(ra, "Updated/replaced IPv6 prefix %s (preferred: %s, valid: %s)",
+                         addr_p,
+                         FORMAT_TIMESPAN(p->lifetime_preferred_usec, USEC_PER_SEC),
+                         FORMAT_TIMESPAN(p->lifetime_valid_usec, USEC_PER_SEC));
+        } else {
+                /* The prefix is new. Let's simply add it. */
+
+                sd_radv_prefix_ref(p);
+                LIST_APPEND(prefix, ra->prefixes, p);
+                ra->n_prefixes++;
+
+                log_radv(ra, "Added prefix %s", addr_p);
+        }
+
+        if (ra->state == RADV_STATE_IDLE)
+                return 0;
+
+        if (ra->ra_sent == 0)
+                return 0;
+
+        /* If RAs have already been sent, send an RA immediately to announce the newly-added prefix */
+        r = radv_send(ra, NULL, ra->lifetime_usec);
+        if (r < 0)
+                log_radv_errno(ra, r, "Unable to send Router Advertisement for added prefix %s, ignoring: %m", addr_p);
+        else
+                log_radv(ra, "Sent Router Advertisement for added/updated prefix %s.", addr_p);
+
+        return 0;
+}
+
+void sd_radv_remove_prefix(
+                sd_radv *ra,
+                const struct in6_addr *prefix,
+                unsigned char prefixlen) {
+
+        if (!ra)
+                return;
+
+        if (!prefix)
+                return;
+
+        LIST_FOREACH(prefix, cur, ra->prefixes) {
+                if (prefixlen != cur->opt.prefixlen)
+                        continue;
+
+                if (!in6_addr_equal(prefix, &cur->opt.in6_addr))
+                        continue;
+
+                LIST_REMOVE(prefix, ra->prefixes, cur);
+                ra->n_prefixes--;
+                sd_radv_prefix_unref(cur);
+                return;
+        }
+}
+
+int sd_radv_add_route_prefix(sd_radv *ra, sd_radv_route_prefix *p) {
+        sd_radv_route_prefix *found = NULL;
+        int r;
+
+        assert_return(ra, -EINVAL);
+        assert_return(p, -EINVAL);
+
+        const char *addr_p = IN6_ADDR_PREFIX_TO_STRING(&p->opt.in6_addr, p->opt.prefixlen);
+
+        LIST_FOREACH(prefix, cur, ra->route_prefixes) {
+                r = in_addr_prefix_intersect(AF_INET6,
+                                             (const union in_addr_union*) &cur->opt.in6_addr,
+                                             cur->opt.prefixlen,
+                                             (const union in_addr_union*) &p->opt.in6_addr,
+                                             p->opt.prefixlen);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                if (cur->opt.prefixlen == p->opt.prefixlen) {
+                        found = cur;
+                        break;
+                }
+
+                return log_radv_errno(ra, SYNTHETIC_ERRNO(EEXIST),
+                                      "IPv6 route prefix %s conflicts with %s, ignoring.",
+                                      addr_p,
+                                      IN6_ADDR_PREFIX_TO_STRING(&cur->opt.in6_addr, cur->opt.prefixlen));
+        }
+
+        if (found) {
+                /* p and cur may be equivalent. First increment the reference counter. */
+                sd_radv_route_prefix_ref(p);
+
+                /* Then, remove the old entry. */
+                LIST_REMOVE(prefix, ra->route_prefixes, found);
+                sd_radv_route_prefix_unref(found);
+
+                /* Finally, add the new entry. */
+                LIST_APPEND(prefix, ra->route_prefixes, p);
+
+                log_radv(ra, "Updated/replaced IPv6 route prefix %s (lifetime: %s)",
+                         strna(addr_p),
+                         FORMAT_TIMESPAN(p->lifetime_usec, USEC_PER_SEC));
+        } else {
+                /* The route prefix is new. Let's simply add it. */
+
+                sd_radv_route_prefix_ref(p);
+                LIST_APPEND(prefix, ra->route_prefixes, p);
+                ra->n_route_prefixes++;
+
+                log_radv(ra, "Added route prefix %s", strna(addr_p));
+        }
+
+        if (ra->state == RADV_STATE_IDLE)
+                return 0;
+
+        if (ra->ra_sent == 0)
+                return 0;
+
+        /* If RAs have already been sent, send an RA immediately to announce the newly-added route prefix */
+        r = radv_send(ra, NULL, ra->lifetime_usec);
+        if (r < 0)
+                log_radv_errno(ra, r, "Unable to send Router Advertisement for added route prefix %s, ignoring: %m",
+                               strna(addr_p));
+        else
+                log_radv(ra, "Sent Router Advertisement for added route prefix %s.", strna(addr_p));
+
+        return 0;
+}
+
+int sd_radv_set_rdnss(
+                sd_radv *ra,
+                uint32_t lifetime,
+                const struct in6_addr *dns,
+                size_t n_dns) {
+
+        _cleanup_free_ struct sd_radv_opt_dns *opt_rdnss = NULL;
+        size_t len;
+
+        assert_return(ra, -EINVAL);
+        assert_return(n_dns < 128, -EINVAL);
+
+        if (!dns || n_dns == 0) {
+                ra->rdnss = mfree(ra->rdnss);
+                ra->n_rdnss = 0;
+
+                return 0;
+        }
+
+        len = sizeof(struct sd_radv_opt_dns) + sizeof(struct in6_addr) * n_dns;
+
+        opt_rdnss = malloc0(len);
+        if (!opt_rdnss)
+                return -ENOMEM;
+
+        opt_rdnss->type = RADV_OPT_RDNSS;
+        opt_rdnss->length = len / 8;
+        opt_rdnss->lifetime = htobe32(lifetime);
+
+        memcpy(opt_rdnss + 1, dns, n_dns * sizeof(struct in6_addr));
+
+        free_and_replace(ra->rdnss, opt_rdnss);
+
+        ra->n_rdnss = n_dns;
+
+        return 0;
+}
+
+int sd_radv_set_dnssl(
+                sd_radv *ra,
+                uint32_t lifetime,
+                char **search_list) {
+
+        _cleanup_free_ struct sd_radv_opt_dns *opt_dnssl = NULL;
+        size_t len = 0;
+        uint8_t *p;
+
+        assert_return(ra, -EINVAL);
+
+        if (strv_isempty(search_list)) {
+                ra->dnssl = mfree(ra->dnssl);
+                return 0;
+        }
+
+        STRV_FOREACH(s, search_list)
+                len += strlen(*s) + 2;
+
+        len = (sizeof(struct sd_radv_opt_dns) + len + 7) & ~0x7;
+
+        opt_dnssl = malloc0(len);
+        if (!opt_dnssl)
+                return -ENOMEM;
+
+        opt_dnssl->type = RADV_OPT_DNSSL;
+        opt_dnssl->length = len / 8;
+        opt_dnssl->lifetime = htobe32(lifetime);
+
+        p = (uint8_t *)(opt_dnssl + 1);
+        len -= sizeof(struct sd_radv_opt_dns);
+
+        STRV_FOREACH(s, search_list) {
+                int r;
+
+                r = dns_name_to_wire_format(*s, p, len, false);
+                if (r < 0)
+                        return r;
+
+                if (len < (size_t)r)
+                        return -ENOBUFS;
+
+                p += r;
+                len -= r;
+        }
+
+        free_and_replace(ra->dnssl, opt_dnssl);
+
+        return 0;
+}
+
+int sd_radv_prefix_new(sd_radv_prefix **ret) {
+        sd_radv_prefix *p;
+
+        assert_return(ret, -EINVAL);
+
+        p = new(sd_radv_prefix, 1);
+        if (!p)
+                return -ENOMEM;
+
+        *p = (sd_radv_prefix) {
+                .n_ref = 1,
+
+                .opt.type = ND_OPT_PREFIX_INFORMATION,
+                .opt.length = (sizeof(p->opt) - 1)/8 + 1,
+                .opt.prefixlen = 64,
+
+                /* RFC 4861, Section 6.2.1 */
+                .opt.flags = ND_OPT_PI_FLAG_ONLINK|ND_OPT_PI_FLAG_AUTO,
+
+                .lifetime_valid_usec = RADV_DEFAULT_VALID_LIFETIME_USEC,
+                .lifetime_preferred_usec = RADV_DEFAULT_PREFERRED_LIFETIME_USEC,
+                .valid_until = USEC_INFINITY,
+                .preferred_until = USEC_INFINITY,
+        };
+
+        *ret = p;
+        return 0;
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_radv_prefix, sd_radv_prefix, mfree);
+
+int sd_radv_prefix_set_prefix(
+                sd_radv_prefix *p,
+                const struct in6_addr *in6_addr,
+                unsigned char prefixlen) {
+
+        assert_return(p, -EINVAL);
+        assert_return(in6_addr, -EINVAL);
+
+        if (prefixlen < 3 || prefixlen > 128)
+                return -EINVAL;
+
+        if (prefixlen > 64)
+                /* unusual but allowed, log it */
+                log_radv(NULL, "Unusual prefix length %d greater than 64", prefixlen);
+
+        p->opt.in6_addr = *in6_addr;
+        p->opt.prefixlen = prefixlen;
+
+        return 0;
+}
+
+int sd_radv_prefix_get_prefix(
+                sd_radv_prefix *p,
+                struct in6_addr *ret_in6_addr,
+                unsigned char *ret_prefixlen) {
+
+        assert_return(p, -EINVAL);
+        assert_return(ret_in6_addr, -EINVAL);
+        assert_return(ret_prefixlen, -EINVAL);
+
+        *ret_in6_addr = p->opt.in6_addr;
+        *ret_prefixlen = p->opt.prefixlen;
+
+        return 0;
+}
+
+int sd_radv_prefix_set_onlink(sd_radv_prefix *p, int onlink) {
+        assert_return(p, -EINVAL);
+
+        SET_FLAG(p->opt.flags, ND_OPT_PI_FLAG_ONLINK, onlink);
+
+        return 0;
+}
+
+int sd_radv_prefix_set_address_autoconfiguration(sd_radv_prefix *p, int address_autoconfiguration) {
+        assert_return(p, -EINVAL);
+
+        SET_FLAG(p->opt.flags, ND_OPT_PI_FLAG_AUTO, address_autoconfiguration);
+
+        return 0;
+}
+
+int sd_radv_prefix_set_valid_lifetime(sd_radv_prefix *p, uint64_t lifetime_usec, uint64_t valid_until) {
+        assert_return(p, -EINVAL);
+
+        p->lifetime_valid_usec = lifetime_usec;
+        p->valid_until = valid_until;
+
+        return 0;
+}
+
+int sd_radv_prefix_set_preferred_lifetime(sd_radv_prefix *p, uint64_t lifetime_usec, uint64_t valid_until) {
+        assert_return(p, -EINVAL);
+
+        p->lifetime_preferred_usec = lifetime_usec;
+        p->preferred_until = valid_until;
+
+        return 0;
+}
+
+int sd_radv_route_prefix_new(sd_radv_route_prefix **ret) {
+        sd_radv_route_prefix *p;
+
+        assert_return(ret, -EINVAL);
+
+        p = new(sd_radv_route_prefix, 1);
+        if (!p)
+                return -ENOMEM;
+
+        *p = (sd_radv_route_prefix) {
+                .n_ref = 1,
+
+                .opt.type = RADV_OPT_ROUTE_INFORMATION,
+                .opt.length = DIV_ROUND_UP(sizeof(p->opt), 8),
+                .opt.prefixlen = 64,
+
+                .lifetime_usec = RADV_DEFAULT_VALID_LIFETIME_USEC,
+                .valid_until = USEC_INFINITY,
+        };
+
+        *ret = p;
+        return 0;
+}
+
+DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_radv_route_prefix, sd_radv_route_prefix, mfree);
+
+int sd_radv_route_prefix_set_prefix(
+                sd_radv_route_prefix *p,
+                const struct in6_addr *in6_addr,
+                unsigned char prefixlen) {
+
+        assert_return(p, -EINVAL);
+        assert_return(in6_addr, -EINVAL);
+
+        if (prefixlen > 128)
+                return -EINVAL;
+
+        if (prefixlen > 64)
+                /* unusual but allowed, log it */
+                log_radv(NULL, "Unusual prefix length %u greater than 64", prefixlen);
+
+        p->opt.in6_addr = *in6_addr;
+        p->opt.prefixlen = prefixlen;
+
+        return 0;
+}
+
+int sd_radv_route_prefix_set_lifetime(sd_radv_route_prefix *p, uint64_t lifetime_usec, uint64_t valid_until) {
+        assert_return(p, -EINVAL);
+
+        p->lifetime_usec = lifetime_usec;
+        p->valid_until = valid_until;
+
+        return 0;
+}
diff --git a/src/libsystemd-network/test-acd.c b/src/libsystemd-network/test-acd.c
new file mode 100644
index 0000000..73105f5
--- /dev/null
+++ b/src/libsystemd-network/test-acd.c
@@ -0,0 +1,95 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <linux/veth.h>
+#include <net/if.h>
+
+#include "sd-event.h"
+#include "sd-ipv4acd.h"
+#include "sd-netlink.h"
+
+#include "in-addr-util.h"
+#include "tests.h"
+#include "util.h"
+
+static void acd_handler(sd_ipv4acd *acd, int event, void *userdata) {
+        assert_se(acd);
+
+        switch (event) {
+        case SD_IPV4ACD_EVENT_BIND:
+                log_info("bound");
+                break;
+        case SD_IPV4ACD_EVENT_CONFLICT:
+                log_info("conflict");
+                break;
+        case SD_IPV4ACD_EVENT_STOP:
+                log_error("the client was stopped");
+                break;
+        default:
+                assert_not_reached();
+        }
+}
+
+static int client_run(int ifindex, const struct in_addr *pa, const struct ether_addr *ha, sd_event *e) {
+        sd_ipv4acd *acd;
+
+        assert_se(sd_ipv4acd_new(&acd) >= 0);
+        assert_se(sd_ipv4acd_attach_event(acd, e, 0) >= 0);
+
+        assert_se(sd_ipv4acd_set_ifindex(acd, ifindex) >= 0);
+        assert_se(sd_ipv4acd_set_mac(acd, ha) >= 0);
+        assert_se(sd_ipv4acd_set_address(acd, pa) >= 0);
+        assert_se(sd_ipv4acd_set_callback(acd, acd_handler, NULL) >= 0);
+
+        log_info("starting IPv4ACD client");
+
+        assert_se(sd_ipv4acd_start(acd, true) >= 0);
+
+        assert_se(sd_event_loop(e) >= 0);
+
+        assert_se(!sd_ipv4acd_unref(acd));
+
+        return EXIT_SUCCESS;
+}
+
+static int test_acd(const char *ifname, const char *address) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
+        _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL, *reply = NULL;
+        union in_addr_union pa;
+        struct ether_addr ha;
+        int ifindex;
+
+        assert_se(in_addr_from_string(AF_INET, address, &pa) >= 0);
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        assert_se(sd_netlink_open(&rtnl) >= 0);
+        assert_se(sd_netlink_attach_event(rtnl, e, 0) >= 0);
+
+        assert_se(sd_rtnl_message_new_link(rtnl, &m, RTM_GETLINK, 0) >= 0);
+        assert_se(sd_netlink_message_append_string(m, IFLA_IFNAME, ifname) >= 0);
+        assert_se(sd_netlink_call(rtnl, m, 0, &reply) >= 0);
+
+        assert_se(sd_rtnl_message_link_get_ifindex(reply, &ifindex) >= 0);
+        assert_se(sd_netlink_message_read_ether_addr(reply, IFLA_ADDRESS, &ha) >= 0);
+
+        client_run(ifindex, &pa.in, &ha, e);
+
+        return EXIT_SUCCESS;
+}
+
+int main(int argc, char *argv[]) {
+        test_setup_logging(LOG_DEBUG);
+
+        if (argc == 3)
+                return test_acd(argv[1], argv[2]);
+        else {
+                log_error("This program takes two arguments.\n"
+                          "\t %s <ifname> <IPv4 address>", program_invocation_short_name);
+                return EXIT_FAILURE;
+        }
+}
diff --git a/src/libsystemd-network/test-dhcp-client.c b/src/libsystemd-network/test-dhcp-client.c
new file mode 100644
index 0000000..787dcf1
--- /dev/null
+++ b/src/libsystemd-network/test-dhcp-client.c
@@ -0,0 +1,557 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <net/if.h>
+#include <net/if_arp.h>
+#include <stdio.h>
+#include <sys/socket.h>
+#include <unistd.h>
+
+#include "sd-dhcp-client.h"
+#include "sd-event.h"
+
+#include "alloc-util.h"
+#include "dhcp-identifier.h"
+#include "dhcp-internal.h"
+#include "dhcp-protocol.h"
+#include "ether-addr-util.h"
+#include "fd-util.h"
+#include "random-util.h"
+#include "tests.h"
+#include "util.h"
+
+static struct hw_addr_data hw_addr = {
+        .length = ETH_ALEN,
+        .ether = {{ 'A', 'B', 'C', '1', '2', '3' }},
+}, bcast_addr = {
+        .length = ETH_ALEN,
+        .ether = {{ 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF }},
+};
+typedef int (*test_callback_recv_t)(size_t size, DHCPMessage *dhcp);
+
+static bool verbose = true;
+static int test_fd[2];
+static test_callback_recv_t callback_recv;
+static be32_t xid;
+
+static void test_request_basic(sd_event *e) {
+        int r;
+
+        sd_dhcp_client *client;
+
+        if (verbose)
+                printf("* %s\n", __func__);
+
+        /* Initialize client without Anonymize settings. */
+        r = sd_dhcp_client_new(&client, false);
+
+        assert_se(r >= 0);
+        assert_se(client);
+
+        r = sd_dhcp_client_attach_event(client, e, 0);
+        assert_se(r >= 0);
+
+        assert_se(sd_dhcp_client_set_request_option(NULL, 0) == -EINVAL);
+        assert_se(sd_dhcp_client_set_request_address(NULL, NULL) == -EINVAL);
+        assert_se(sd_dhcp_client_set_ifindex(NULL, 0) == -EINVAL);
+
+        assert_se(sd_dhcp_client_set_ifindex(client, 15) == 0);
+        assert_se(sd_dhcp_client_set_ifindex(client, -42) == -EINVAL);
+        assert_se(sd_dhcp_client_set_ifindex(client, -1) == -EINVAL);
+        assert_se(sd_dhcp_client_set_ifindex(client, 0) == -EINVAL);
+        assert_se(sd_dhcp_client_set_ifindex(client, 1) == 0);
+
+        assert_se(sd_dhcp_client_set_hostname(client, "host") == 1);
+        assert_se(sd_dhcp_client_set_hostname(client, "host.domain") == 1);
+        assert_se(sd_dhcp_client_set_hostname(client, NULL) == 1);
+        assert_se(sd_dhcp_client_set_hostname(client, "~host") == -EINVAL);
+        assert_se(sd_dhcp_client_set_hostname(client, "~host.domain") == -EINVAL);
+
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_SUBNET_MASK) == 0);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_ROUTER) == 0);
+        /* This PRL option is not set when using Anonymize, but in this test
+         * Anonymize settings are not being used. */
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_HOST_NAME) == 0);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_DOMAIN_NAME) == 0);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_DOMAIN_NAME_SERVER) == 0);
+
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_PAD) == -EINVAL);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_END) == -EINVAL);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_MESSAGE_TYPE) == -EINVAL);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_OVERLOAD) == -EINVAL);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_PARAMETER_REQUEST_LIST) == -EINVAL);
+
+        /* RFC7844: option 33 (SD_DHCP_OPTION_STATIC_ROUTE) is set in the
+         * default PRL when using Anonymize, so it is changed to other option
+         * that is not set by default, to check that it was set successfully.
+         * Options not set by default (using or not anonymize) are option 17
+         * (SD_DHCP_OPTION_ROOT_PATH) and 42 (SD_DHCP_OPTION_NTP_SERVER) */
+        assert_se(sd_dhcp_client_set_request_option(client, 17) == 1);
+        assert_se(sd_dhcp_client_set_request_option(client, 17) == 0);
+        assert_se(sd_dhcp_client_set_request_option(client, 42) == 1);
+        assert_se(sd_dhcp_client_set_request_option(client, 17) == 0);
+
+        sd_dhcp_client_unref(client);
+}
+
+static void test_request_anonymize(sd_event *e) {
+        int r;
+
+        sd_dhcp_client *client;
+
+        if (verbose)
+                printf("* %s\n", __func__);
+
+        /* Initialize client with Anonymize settings. */
+        r = sd_dhcp_client_new(&client, true);
+
+        assert_se(r >= 0);
+        assert_se(client);
+
+        r = sd_dhcp_client_attach_event(client, e, 0);
+        assert_se(r >= 0);
+
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_NETBIOS_NAME_SERVER) == 0);
+        /* This PRL option is not set when using Anonymize */
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_HOST_NAME) == 1);
+        assert_se(sd_dhcp_client_set_request_option(client, SD_DHCP_OPTION_PARAMETER_REQUEST_LIST) == -EINVAL);
+
+        /* RFC7844: option 101 (SD_DHCP_OPTION_NEW_TZDB_TIMEZONE) is not set in the
+         * default PRL when using Anonymize, */
+        assert_se(sd_dhcp_client_set_request_option(client, 101) == 1);
+        assert_se(sd_dhcp_client_set_request_option(client, 101) == 0);
+
+        sd_dhcp_client_unref(client);
+}
+
+static void test_checksum(void) {
+        uint8_t buf[20] = {
+                0x45, 0x00, 0x02, 0x40, 0x00, 0x00, 0x00, 0x00,
+                0x40, 0x11, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0xff, 0xff, 0xff, 0xff
+        };
+
+        if (verbose)
+                printf("* %s\n", __func__);
+
+        assert_se(dhcp_packet_checksum((uint8_t*)&buf, 20) == be16toh(0x78ae));
+}
+
+static void test_dhcp_identifier_set_iaid(void) {
+        uint32_t iaid_legacy;
+        be32_t iaid;
+
+        assert_se(dhcp_identifier_set_iaid(42, &hw_addr, /* legacy = */ true,
+                                           /* use_mac = */ true, &iaid_legacy) >= 0);
+        assert_se(dhcp_identifier_set_iaid(42, &hw_addr, /* legacy = */ false,
+                                           /* use_mac = */ true, &iaid) >= 0);
+
+        /* we expect, that the MAC address was hashed. The legacy value is in native
+         * endianness. */
+        assert_se(iaid_legacy == 0x8dde4ba8u);
+        assert_se(iaid  == htole32(0x8dde4ba8u));
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+        assert_se(iaid == iaid_legacy);
+#else
+        assert_se(iaid == bswap_32(iaid_legacy));
+#endif
+}
+
+static int check_options(uint8_t code, uint8_t len, const void *option, void *userdata) {
+        switch (code) {
+        case SD_DHCP_OPTION_CLIENT_IDENTIFIER:
+        {
+                uint32_t iaid;
+                struct duid duid;
+                size_t duid_len;
+
+                assert_se(dhcp_identifier_set_duid_en(/* test_mode = */ true, &duid, &duid_len) >= 0);
+                assert_se(dhcp_identifier_set_iaid(42, &hw_addr, /* legacy = */ true, /* use_mac = */ true, &iaid) >= 0);
+
+                assert_se(len == sizeof(uint8_t) + sizeof(uint32_t) + duid_len);
+                assert_se(len == 19);
+                assert_se(((uint8_t*) option)[0] == 0xff);
+
+                assert_se(memcmp((uint8_t*) option + 1, &iaid, sizeof(iaid)) == 0);
+                assert_se(memcmp((uint8_t*) option + 5, &duid, duid_len) == 0);
+                break;
+        }
+
+        default:
+                break;
+        }
+
+        return 0;
+}
+
+int dhcp_network_send_raw_socket(int s, const union sockaddr_union *link, const void *packet, size_t len) {
+        size_t size;
+        _cleanup_free_ DHCPPacket *discover = NULL;
+        uint16_t ip_check, udp_check;
+
+        assert_se(s >= 0);
+        assert_se(packet);
+
+        size = sizeof(DHCPPacket);
+        assert_se(len > size);
+
+        discover = memdup(packet, len);
+
+        assert_se(discover->ip.ttl == IPDEFTTL);
+        assert_se(discover->ip.protocol == IPPROTO_UDP);
+        assert_se(discover->ip.saddr == INADDR_ANY);
+        assert_se(discover->ip.daddr == INADDR_BROADCAST);
+        assert_se(discover->udp.source == be16toh(DHCP_PORT_CLIENT));
+        assert_se(discover->udp.dest == be16toh(DHCP_PORT_SERVER));
+
+        ip_check = discover->ip.check;
+
+        discover->ip.ttl = 0;
+        discover->ip.check = discover->udp.len;
+
+        udp_check = ~dhcp_packet_checksum((uint8_t*)&discover->ip.ttl, len - 8);
+        assert_se(udp_check == 0xffff);
+
+        discover->ip.ttl = IPDEFTTL;
+        discover->ip.check = ip_check;
+
+        ip_check = ~dhcp_packet_checksum((uint8_t*)&discover->ip, sizeof(discover->ip));
+        assert_se(ip_check == 0xffff);
+
+        assert_se(discover->dhcp.xid);
+        assert_se(memcmp(discover->dhcp.chaddr, hw_addr.bytes, hw_addr.length) == 0);
+
+        size = len - sizeof(struct iphdr) - sizeof(struct udphdr);
+
+        assert_se(callback_recv);
+        callback_recv(size, &discover->dhcp);
+
+        return 575;
+}
+
+int dhcp_network_bind_raw_socket(
+                int ifindex,
+                union sockaddr_union *link,
+                uint32_t id,
+                const struct hw_addr_data *_hw_addr,
+                const struct hw_addr_data *_bcast_addr,
+                uint16_t arp_type, uint16_t port) {
+
+        if (socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
+                return -errno;
+
+        return test_fd[0];
+}
+
+int dhcp_network_bind_udp_socket(int ifindex, be32_t address, uint16_t port, int ip_service_type) {
+        int fd;
+
+        fd = socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0);
+        if (fd < 0)
+                return -errno;
+
+        return fd;
+}
+
+int dhcp_network_send_udp_socket(int s, be32_t address, uint16_t port, const void *packet, size_t len) {
+        return 0;
+}
+
+static int test_discover_message_verify(size_t size, struct DHCPMessage *dhcp) {
+        int res;
+
+        res = dhcp_option_parse(dhcp, size, check_options, NULL, NULL);
+        assert_se(res == DHCP_DISCOVER);
+
+        if (verbose)
+                printf("  recv DHCP Discover 0x%08x\n", be32toh(dhcp->xid));
+
+        return 0;
+}
+
+static void test_discover_message(sd_event *e) {
+        sd_dhcp_client *client;
+        int res, r;
+
+        if (verbose)
+                printf("* %s\n", __func__);
+
+        r = sd_dhcp_client_new(&client, false);
+        assert_se(r >= 0);
+        assert_se(client);
+
+        r = sd_dhcp_client_attach_event(client, e, 0);
+        assert_se(r >= 0);
+
+        assert_se(sd_dhcp_client_set_ifindex(client, 42) >= 0);
+        assert_se(sd_dhcp_client_set_mac(client, hw_addr.bytes, bcast_addr.bytes, hw_addr.length, ARPHRD_ETHER) >= 0);
+        dhcp_client_set_test_mode(client, true);
+
+        assert_se(sd_dhcp_client_set_request_option(client, 248) >= 0);
+
+        callback_recv = test_discover_message_verify;
+
+        res = sd_dhcp_client_start(client);
+
+        assert_se(IN_SET(res, 0, -EINPROGRESS));
+
+        sd_event_run(e, UINT64_MAX);
+
+        sd_dhcp_client_stop(client);
+        sd_dhcp_client_unref(client);
+
+        test_fd[1] = safe_close(test_fd[1]);
+
+        callback_recv = NULL;
+}
+
+static uint8_t test_addr_acq_offer[] = {
+        0x45, 0x10, 0x01, 0x48, 0x00, 0x00, 0x00, 0x00,
+        0x80, 0x11, 0xb3, 0x84, 0xc0, 0xa8, 0x02, 0x01,
+        0xc0, 0xa8, 0x02, 0xbf, 0x00, 0x43, 0x00, 0x44,
+        0x01, 0x34, 0x00, 0x00, 0x02, 0x01, 0x06, 0x00,
+        0x6f, 0x95, 0x2f, 0x30, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0xc0, 0xa8, 0x02, 0xbf,
+        0xc0, 0xa8, 0x02, 0x01, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x63, 0x82, 0x53, 0x63, 0x35, 0x01, 0x02, 0x36,
+        0x04, 0xc0, 0xa8, 0x02, 0x01, 0x33, 0x04, 0x00,
+        0x00, 0x02, 0x58, 0x01, 0x04, 0xff, 0xff, 0xff,
+        0x00, 0x2a, 0x04, 0xc0, 0xa8, 0x02, 0x01, 0x0f,
+        0x09, 0x6c, 0x61, 0x62, 0x2e, 0x69, 0x6e, 0x74,
+        0x72, 0x61, 0x03, 0x04, 0xc0, 0xa8, 0x02, 0x01,
+        0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+};
+
+static uint8_t test_addr_acq_ack[] = {
+        0x45, 0x10, 0x01, 0x48, 0x00, 0x00, 0x00, 0x00,
+        0x80, 0x11, 0xb3, 0x84, 0xc0, 0xa8, 0x02, 0x01,
+        0xc0, 0xa8, 0x02, 0xbf, 0x00, 0x43, 0x00, 0x44,
+        0x01, 0x34, 0x00, 0x00, 0x02, 0x01, 0x06, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0xc0, 0xa8, 0x02, 0xbf,
+        0xc0, 0xa8, 0x02, 0x01, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x63, 0x82, 0x53, 0x63, 0x35, 0x01, 0x05, 0x36,
+        0x04, 0xc0, 0xa8, 0x02, 0x01, 0x33, 0x04, 0x00,
+        0x00, 0x02, 0x58, 0x01, 0x04, 0xff, 0xff, 0xff,
+        0x00, 0x2a, 0x04, 0xc0, 0xa8, 0x02, 0x01, 0x0f,
+        0x09, 0x6c, 0x61, 0x62, 0x2e, 0x69, 0x6e, 0x74,
+        0x72, 0x61, 0x03, 0x04, 0xc0, 0xa8, 0x02, 0x01,
+        0xff, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+};
+
+static int test_addr_acq_acquired(sd_dhcp_client *client, int event,
+                                   void *userdata) {
+        sd_event *e = userdata;
+        sd_dhcp_lease *lease;
+        struct in_addr addr;
+        const struct in_addr *addrs;
+
+        assert_se(client);
+        assert_se(IN_SET(event, SD_DHCP_CLIENT_EVENT_IP_ACQUIRE, SD_DHCP_CLIENT_EVENT_SELECTING));
+
+        assert_se(sd_dhcp_client_get_lease(client, &lease) >= 0);
+        assert_se(lease);
+
+        assert_se(sd_dhcp_lease_get_address(lease, &addr) >= 0);
+        assert_se(memcmp(&addr.s_addr, &test_addr_acq_ack[44],
+                      sizeof(addr.s_addr)) == 0);
+
+        assert_se(sd_dhcp_lease_get_netmask(lease, &addr) >= 0);
+        assert_se(memcmp(&addr.s_addr, &test_addr_acq_ack[285],
+                      sizeof(addr.s_addr)) == 0);
+
+        assert_se(sd_dhcp_lease_get_router(lease, &addrs) == 1);
+        assert_se(memcmp(&addrs[0].s_addr, &test_addr_acq_ack[308],
+                         sizeof(addrs[0].s_addr)) == 0);
+
+        if (verbose)
+                printf("  DHCP address acquired\n");
+
+        sd_event_exit(e, 0);
+
+        return 0;
+}
+
+static int test_addr_acq_recv_request(size_t size, DHCPMessage *request) {
+        uint16_t udp_check = 0;
+        uint8_t *msg_bytes = (uint8_t *)request;
+        int res;
+
+        res = dhcp_option_parse(request, size, check_options, NULL, NULL);
+        assert_se(res == DHCP_REQUEST);
+        assert_se(xid == request->xid);
+
+        assert_se(msg_bytes[size - 1] == SD_DHCP_OPTION_END);
+
+        if (verbose)
+                printf("  recv DHCP Request  0x%08x\n", be32toh(xid));
+
+        memcpy(&test_addr_acq_ack[26], &udp_check, sizeof(udp_check));
+        memcpy(&test_addr_acq_ack[32], &xid, sizeof(xid));
+        memcpy(&test_addr_acq_ack[56], hw_addr.bytes, hw_addr.length);
+
+        callback_recv = NULL;
+
+        res = write(test_fd[1], test_addr_acq_ack,
+                    sizeof(test_addr_acq_ack));
+        assert_se(res == sizeof(test_addr_acq_ack));
+
+        if (verbose)
+                printf("  send DHCP Ack\n");
+
+        return 0;
+};
+
+static int test_addr_acq_recv_discover(size_t size, DHCPMessage *discover) {
+        uint16_t udp_check = 0;
+        uint8_t *msg_bytes = (uint8_t *)discover;
+        int res;
+
+        res = dhcp_option_parse(discover, size, check_options, NULL, NULL);
+        assert_se(res == DHCP_DISCOVER);
+
+        assert_se(msg_bytes[size - 1] == SD_DHCP_OPTION_END);
+
+        xid = discover->xid;
+
+        if (verbose)
+                printf("  recv DHCP Discover 0x%08x\n", be32toh(xid));
+
+        memcpy(&test_addr_acq_offer[26], &udp_check, sizeof(udp_check));
+        memcpy(&test_addr_acq_offer[32], &xid, sizeof(xid));
+        memcpy(&test_addr_acq_offer[56], hw_addr.bytes, hw_addr.length);
+
+        callback_recv = test_addr_acq_recv_request;
+
+        res = write(test_fd[1], test_addr_acq_offer,
+                    sizeof(test_addr_acq_offer));
+        assert_se(res == sizeof(test_addr_acq_offer));
+
+        if (verbose)
+                printf("  sent DHCP Offer\n");
+
+        return 0;
+}
+
+static void test_addr_acq(sd_event *e) {
+        sd_dhcp_client *client;
+        int res, r;
+
+        if (verbose)
+                printf("* %s\n", __func__);
+
+        r = sd_dhcp_client_new(&client, false);
+        assert_se(r >= 0);
+        assert_se(client);
+
+        r = sd_dhcp_client_attach_event(client, e, 0);
+        assert_se(r >= 0);
+
+        assert_se(sd_dhcp_client_set_ifindex(client, 42) >= 0);
+        assert_se(sd_dhcp_client_set_mac(client, hw_addr.bytes, bcast_addr.bytes, hw_addr.length, ARPHRD_ETHER) >= 0);
+        dhcp_client_set_test_mode(client, true);
+
+        assert_se(sd_dhcp_client_set_callback(client, test_addr_acq_acquired, e) >= 0);
+
+        callback_recv = test_addr_acq_recv_discover;
+
+        assert_se(sd_event_add_time_relative(e, NULL, CLOCK_BOOTTIME,
+                                             2 * USEC_PER_SEC, 0,
+                                             NULL, INT_TO_PTR(-ETIMEDOUT)) >= 0);
+
+        res = sd_dhcp_client_start(client);
+        assert_se(IN_SET(res, 0, -EINPROGRESS));
+
+        assert_se(sd_event_loop(e) >= 0);
+
+        assert_se(sd_dhcp_client_set_callback(client, NULL, NULL) >= 0);
+        assert_se(sd_dhcp_client_stop(client) >= 0);
+        sd_dhcp_client_unref(client);
+
+        test_fd[1] = safe_close(test_fd[1]);
+
+        callback_recv = NULL;
+        xid = 0;
+}
+
+int main(int argc, char *argv[]) {
+        _cleanup_(sd_event_unrefp) sd_event *e;
+
+        test_setup_logging(LOG_DEBUG);
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        test_request_basic(e);
+        test_request_anonymize(e);
+        test_checksum();
+        test_dhcp_identifier_set_iaid();
+
+        test_discover_message(e);
+        test_addr_acq(e);
+
+#if VALGRIND
+        /* Make sure the async_close thread has finished.
+         * valgrind would report some of the phread_* structures
+         * as not cleaned up properly. */
+        sleep(1);
+#endif
+
+        return 0;
+}
diff --git a/src/libsystemd-network/test-dhcp-option.c b/src/libsystemd-network/test-dhcp-option.c
new file mode 100644
index 0000000..82c5cdb
--- /dev/null
+++ b/src/libsystemd-network/test-dhcp-option.c
@@ -0,0 +1,382 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <net/if_arp.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "alloc-util.h"
+#include "dhcp-internal.h"
+#include "dhcp-protocol.h"
+#include "macro.h"
+#include "memory-util.h"
+
+struct option_desc {
+        uint8_t sname[64];
+        int snamelen;
+        uint8_t file[128];
+        int filelen;
+        uint8_t options[128];
+        int len;
+        bool success;
+        int filepos;
+        int snamepos;
+        int pos;
+};
+
+static bool verbose = false;
+
+static struct option_desc option_tests[] = {
+        { {}, 0, {}, 0, { 42, 5, 65, 66, 67, 68, 69 }, 7, false, },
+        { {}, 0, {}, 0, { 42, 5, 65, 66, 67, 68, 69, 0, 0,
+                          SD_DHCP_OPTION_MESSAGE_TYPE, 1, DHCP_ACK }, 12, true, },
+        { {}, 0, {}, 0, { 8, 255, 70, 71, 72 }, 5, false, },
+        { {}, 0, {}, 0, { 0x35, 0x01, 0x05, 0x36, 0x04, 0x01, 0x00, 0xa8,
+                          0xc0, 0x33, 0x04, 0x00, 0x01, 0x51, 0x80, 0x01,
+                          0x04, 0xff, 0xff, 0xff, 0x00, 0x03, 0x04, 0xc0,
+                          0xa8, 0x00, 0x01, 0x06, 0x04, 0xc0, 0xa8, 0x00,
+                          0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, },
+          40, true, },
+        { {}, 0, {}, 0, { SD_DHCP_OPTION_MESSAGE_TYPE, 1, DHCP_OFFER,
+                          42, 3, 0, 0, 0 }, 8, true, },
+        { {}, 0, {}, 0, { 42, 2, 1, 2, 44 }, 5, false, },
+
+        { {}, 0,
+          { 222, 3, 1, 2, 3, SD_DHCP_OPTION_MESSAGE_TYPE, 1, DHCP_NAK }, 8,
+          { SD_DHCP_OPTION_OVERLOAD, 1, DHCP_OVERLOAD_FILE }, 3, true, },
+
+        { { 1, 4, 1, 2, 3, 4, SD_DHCP_OPTION_MESSAGE_TYPE, 1, DHCP_ACK }, 9,
+          { 222, 3, 1, 2, 3 }, 5,
+          { SD_DHCP_OPTION_OVERLOAD, 1,
+            DHCP_OVERLOAD_FILE|DHCP_OVERLOAD_SNAME }, 3, true, },
+};
+
+static const char *dhcp_type(int type) {
+        switch (type) {
+        case DHCP_DISCOVER:
+                return "DHCPDISCOVER";
+        case DHCP_OFFER:
+                return "DHCPOFFER";
+        case DHCP_REQUEST:
+                return "DHCPREQUEST";
+        case DHCP_DECLINE:
+                return "DHCPDECLINE";
+        case DHCP_ACK:
+                return "DHCPACK";
+        case DHCP_NAK:
+                return "DHCPNAK";
+        case DHCP_RELEASE:
+                return "DHCPRELEASE";
+        default:
+                return "unknown";
+        }
+}
+
+static void test_invalid_buffer_length(void) {
+        DHCPMessage message;
+
+        assert_se(dhcp_option_parse(&message, 0, NULL, NULL, NULL) == -EINVAL);
+        assert_se(dhcp_option_parse(&message, sizeof(DHCPMessage) - 1, NULL, NULL, NULL) == -EINVAL);
+}
+
+static void test_message_init(void) {
+        _cleanup_free_ DHCPMessage *message = NULL;
+        size_t optlen = 4, optoffset;
+        size_t len = sizeof(DHCPMessage) + optlen;
+        uint8_t *magic;
+
+        message = malloc0(len);
+
+        assert_se(dhcp_message_init(message, BOOTREQUEST, 0x12345678,
+                                    DHCP_DISCOVER, ARPHRD_ETHER, ETH_ALEN, (uint8_t[16]){},
+                                    optlen, &optoffset) >= 0);
+
+        assert_se(message->xid == htobe32(0x12345678));
+        assert_se(message->op == BOOTREQUEST);
+
+        magic = (uint8_t*)&message->magic;
+
+        assert_se(magic[0] == 99);
+        assert_se(magic[1] == 130);
+        assert_se(magic[2] == 83);
+        assert_se(magic[3] == 99);
+
+        assert_se(dhcp_option_parse(message, len, NULL, NULL, NULL) >= 0);
+}
+
+static DHCPMessage *create_message(uint8_t *options, uint16_t optlen,
+                uint8_t *file, uint8_t filelen,
+                uint8_t *sname, uint8_t snamelen) {
+        DHCPMessage *message;
+        size_t len = sizeof(DHCPMessage) + optlen;
+
+        message = malloc0(len);
+        assert_se(message);
+
+        memcpy_safe(&message->options, options, optlen);
+        memcpy_safe(&message->file, file, filelen);
+        memcpy_safe(&message->sname, sname, snamelen);
+
+        return message;
+}
+
+static void test_ignore_opts(uint8_t *descoption, int *descpos, int *desclen) {
+        assert_se(*descpos >= 0);
+
+        while (*descpos < *desclen) {
+                switch (descoption[*descpos]) {
+                case SD_DHCP_OPTION_PAD:
+                        *descpos += 1;
+                        break;
+
+                case SD_DHCP_OPTION_MESSAGE_TYPE:
+                case SD_DHCP_OPTION_OVERLOAD:
+                        *descpos += 3;
+                        break;
+
+                default:
+                        return;
+                }
+        }
+}
+
+static int test_options_cb(uint8_t code, uint8_t len, const void *option, void *userdata) {
+        struct option_desc *desc = userdata;
+        uint8_t *descoption = NULL;
+        int *desclen = NULL, *descpos = NULL;
+        uint8_t optcode = 0;
+        uint8_t optlen = 0;
+
+        assert_se((!desc && !code && !len) || desc);
+
+        if (!desc)
+                return -EINVAL;
+
+        assert_se(code != SD_DHCP_OPTION_PAD);
+        assert_se(code != SD_DHCP_OPTION_END);
+        assert_se(code != SD_DHCP_OPTION_MESSAGE_TYPE);
+        assert_se(code != SD_DHCP_OPTION_OVERLOAD);
+
+        while (desc->pos >= 0 || desc->filepos >= 0 || desc->snamepos >= 0) {
+
+                if (desc->pos >= 0) {
+                        descoption = &desc->options[0];
+                        desclen = &desc->len;
+                        descpos = &desc->pos;
+                } else if (desc->filepos >= 0) {
+                        descoption = &desc->file[0];
+                        desclen = &desc->filelen;
+                        descpos = &desc->filepos;
+                } else if (desc->snamepos >= 0) {
+                        descoption = &desc->sname[0];
+                        desclen = &desc->snamelen;
+                        descpos = &desc->snamepos;
+                }
+
+                assert_se(descoption && desclen && descpos);
+
+                if (*desclen)
+                        test_ignore_opts(descoption, descpos, desclen);
+
+                if (*descpos < *desclen)
+                        break;
+
+                if (*descpos == *desclen)
+                        *descpos = -1;
+        }
+
+        assert_se(descpos);
+        assert_se(*descpos != -1);
+
+        optcode = descoption[*descpos];
+        optlen = descoption[*descpos + 1];
+
+        if (verbose)
+                printf("DHCP code %2d(%2d) len %2d(%2d) ", code, optcode,
+                                len, optlen);
+
+        assert_se(code == optcode);
+        assert_se(len == optlen);
+
+        for (unsigned i = 0; i < len; i++) {
+                if (verbose)
+                        printf("0x%02x(0x%02x) ",
+                               ((uint8_t*) option)[i],
+                               descoption[*descpos + 2 + i]);
+
+                assert_se(((uint8_t*) option)[i] == descoption[*descpos + 2 + i]);
+        }
+
+        if (verbose)
+                printf("\n");
+
+        *descpos += optlen + 2;
+
+        test_ignore_opts(descoption, descpos, desclen);
+
+        if (desc->pos != -1 && desc->pos == desc->len)
+                desc->pos = -1;
+
+        if (desc->filepos != -1 && desc->filepos == desc->filelen)
+                desc->filepos = -1;
+
+        if (desc->snamepos != -1 && desc->snamepos == desc->snamelen)
+                desc->snamepos = -1;
+
+        return 0;
+}
+
+static void test_options(struct option_desc *desc) {
+        uint8_t *options = NULL;
+        uint8_t *file = NULL;
+        uint8_t *sname = NULL;
+        int optlen = 0;
+        int filelen = 0;
+        int snamelen = 0;
+        int buflen = 0;
+        _cleanup_free_ DHCPMessage *message = NULL;
+        int res;
+
+        if (desc) {
+                file = &desc->file[0];
+                filelen = desc->filelen;
+                if (!filelen)
+                        desc->filepos = -1;
+
+                sname = &desc->sname[0];
+                snamelen = desc->snamelen;
+                if (!snamelen)
+                        desc->snamepos = -1;
+
+                options = &desc->options[0];
+                optlen = desc->len;
+                desc->pos = 0;
+        }
+        message = create_message(options, optlen, file, filelen,
+                                 sname, snamelen);
+
+        buflen = sizeof(DHCPMessage) + optlen;
+
+        if (!desc) {
+                assert_se((res = dhcp_option_parse(message, buflen, test_options_cb, NULL, NULL)) == -ENOMSG);
+        } else if (desc->success) {
+                assert_se((res = dhcp_option_parse(message, buflen, test_options_cb, desc, NULL)) >= 0);
+                assert_se(desc->pos == -1 && desc->filepos == -1 && desc->snamepos == -1);
+        } else
+                assert_se((res = dhcp_option_parse(message, buflen, test_options_cb, desc, NULL)) < 0);
+
+        if (verbose)
+                printf("DHCP type %s\n", dhcp_type(res));
+}
+
+static void test_option_removal(struct option_desc *desc) {
+        _cleanup_free_ DHCPMessage *message = create_message(&desc->options[0], desc->len, NULL, 0, NULL, 0);
+
+        assert_se(dhcp_option_parse(message, sizeof(DHCPMessage) + desc->len, NULL, NULL, NULL) >= 0);
+        assert_se((desc->len = dhcp_option_remove_option(message->options, desc->len, SD_DHCP_OPTION_MESSAGE_TYPE)) >= 0);
+        assert_se(dhcp_option_parse(message, sizeof(DHCPMessage) + desc->len, NULL, NULL, NULL) < 0);
+}
+
+static uint8_t the_options[64] = {
+        'A', 'B', 'C', 'D',
+        160, 2, 0x11, 0x12,
+        0,
+        31, 8, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+        0,
+        55, 3, 0x51, 0x52, 0x53,
+        17, 7, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
+        255
+};
+
+static void test_option_set(void) {
+        _cleanup_free_ DHCPMessage *result = NULL;
+        size_t offset = 0, len, pos;
+
+        result = malloc0(sizeof(DHCPMessage) + 11);
+        assert_se(result);
+
+        result->options[0] = 'A';
+        result->options[1] = 'B';
+        result->options[2] = 'C';
+        result->options[3] = 'D';
+
+        assert_se(dhcp_option_append(result, 0, &offset, 0, SD_DHCP_OPTION_PAD,
+                                     0, NULL) == -ENOBUFS);
+        assert_se(offset == 0);
+
+        offset = 4;
+        assert_se(dhcp_option_append(result, 5, &offset, 0, SD_DHCP_OPTION_PAD,
+                                     0, NULL) == -ENOBUFS);
+        assert_se(offset == 4);
+        assert_se(dhcp_option_append(result, 6, &offset, 0, SD_DHCP_OPTION_PAD,
+                                     0, NULL) >= 0);
+        assert_se(offset == 5);
+
+        offset = pos = 4;
+        len = 11;
+        while (pos < len && the_options[pos] != SD_DHCP_OPTION_END) {
+                assert_se(dhcp_option_append(result, len, &offset, DHCP_OVERLOAD_SNAME,
+                                             the_options[pos],
+                                             the_options[pos + 1],
+                                             &the_options[pos + 2]) >= 0);
+
+                if (the_options[pos] == SD_DHCP_OPTION_PAD)
+                        pos++;
+                else
+                        pos += 2 + the_options[pos + 1];
+
+                if (pos < len)
+                        assert_se(offset == pos);
+        }
+
+        for (unsigned i = 0; i < 9; i++) {
+                if (verbose)
+                        printf("%2u: 0x%02x(0x%02x) (options)\n", i, result->options[i],
+                               the_options[i]);
+                assert_se(result->options[i] == the_options[i]);
+        }
+
+        if (verbose)
+                printf("%2d: 0x%02x(0x%02x) (options)\n", 9, result->options[9],
+                       (unsigned) SD_DHCP_OPTION_END);
+
+        assert_se(result->options[9] == SD_DHCP_OPTION_END);
+
+        if (verbose)
+                printf("%2d: 0x%02x(0x%02x) (options)\n", 10, result->options[10],
+                       (unsigned) SD_DHCP_OPTION_PAD);
+
+        assert_se(result->options[10] == SD_DHCP_OPTION_PAD);
+
+        for (unsigned i = 0; i < pos - 8; i++) {
+                if (verbose)
+                        printf("%2u: 0x%02x(0x%02x) (sname)\n", i, result->sname[i],
+                               the_options[i + 9]);
+                assert_se(result->sname[i] == the_options[i + 9]);
+        }
+
+        if (verbose)
+                printf ("\n");
+}
+
+int main(int argc, char *argv[]) {
+        test_invalid_buffer_length();
+        test_message_init();
+
+        test_options(NULL);
+
+        for (unsigned i = 0; i < ELEMENTSOF(option_tests); i++)
+                test_options(&option_tests[i]);
+
+        test_option_set();
+
+        for (unsigned i = 0; i < ELEMENTSOF(option_tests); i++) {
+                struct option_desc *desc = &option_tests[i];
+                if (!desc->success || desc->snamelen > 0 || desc->filelen > 0)
+                        continue;
+                test_option_removal(desc);
+        }
+
+        return 0;
+}
diff --git a/src/libsystemd-network/test-dhcp-server.c b/src/libsystemd-network/test-dhcp-server.c
new file mode 100644
index 0000000..f8a4c2c
--- /dev/null
+++ b/src/libsystemd-network/test-dhcp-server.c
@@ -0,0 +1,322 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2013 Intel Corporation. All rights reserved.
+***/
+
+#include <errno.h>
+#include <net/if_arp.h>
+
+#include "sd-dhcp-server.h"
+#include "sd-event.h"
+
+#include "dhcp-server-internal.h"
+#include "tests.h"
+
+static void test_pool(struct in_addr *address, unsigned size, int ret) {
+        _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL;
+
+        assert_se(sd_dhcp_server_new(&server, 1) >= 0);
+
+        assert_se(sd_dhcp_server_configure_pool(server, address, 8, 0, size) == ret);
+}
+
+static int test_basic(bool bind_to_interface) {
+        _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL;
+        _cleanup_(sd_event_unrefp) sd_event *event = NULL;
+        struct in_addr address_lo = {
+                .s_addr = htobe32(INADDR_LOOPBACK),
+        };
+        struct in_addr address_any = {
+                .s_addr = htobe32(INADDR_ANY),
+        };
+        int r;
+
+        log_debug("/* %s(bind_to_interface=%s) */", __func__, yes_no(bind_to_interface));
+
+        assert_se(sd_event_new(&event) >= 0);
+
+        /* attach to loopback interface */
+        assert_se(sd_dhcp_server_new(&server, 1) >= 0);
+        assert_se(server);
+        server->bind_to_interface = bind_to_interface;
+
+        assert_se(sd_dhcp_server_attach_event(server, event, 0) >= 0);
+        assert_se(sd_dhcp_server_attach_event(server, event, 0) == -EBUSY);
+        assert_se(sd_dhcp_server_get_event(server) == event);
+        assert_se(sd_dhcp_server_detach_event(server) >= 0);
+        assert_se(!sd_dhcp_server_get_event(server));
+        assert_se(sd_dhcp_server_attach_event(server, NULL, 0) >= 0);
+        assert_se(sd_dhcp_server_attach_event(server, NULL, 0) == -EBUSY);
+
+        assert_se(sd_dhcp_server_ref(server) == server);
+        assert_se(!sd_dhcp_server_unref(server));
+
+        assert_se(sd_dhcp_server_start(server) == -EUNATCH);
+
+        assert_se(sd_dhcp_server_configure_pool(server, &address_any, 28, 0, 0) == -EINVAL);
+        assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 38, 0, 0) == -ERANGE);
+        assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 8, 0, 0) >= 0);
+        assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 8, 0, 0) >= 0);
+
+        test_pool(&address_any, 1, -EINVAL);
+        test_pool(&address_lo, 1, 0);
+
+        r = sd_dhcp_server_start(server);
+        if (r == -EPERM)
+                return r;
+        assert_se(r >= 0);
+
+        assert_se(sd_dhcp_server_start(server) >= 0);
+        assert_se(sd_dhcp_server_stop(server) >= 0);
+        assert_se(sd_dhcp_server_stop(server) >= 0);
+        assert_se(sd_dhcp_server_start(server) >= 0);
+
+        return 0;
+}
+
+static void test_message_handler(void) {
+        _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL;
+        struct {
+                DHCPMessage message;
+                struct {
+                        uint8_t code;
+                        uint8_t length;
+                        uint8_t type;
+                } _packed_ option_type;
+                struct {
+                        uint8_t code;
+                        uint8_t length;
+                        be32_t address;
+                } _packed_ option_requested_ip;
+                struct {
+                        uint8_t code;
+                        uint8_t length;
+                        be32_t address;
+                } _packed_ option_server_id;
+                struct {
+                        uint8_t code;
+                        uint8_t length;
+                        uint8_t id[7];
+                } _packed_ option_client_id;
+                uint8_t end;
+        } _packed_ test = {
+                .message.op = BOOTREQUEST,
+                .message.htype = ARPHRD_ETHER,
+                .message.hlen = ETHER_ADDR_LEN,
+                .message.xid = htobe32(0x12345678),
+                .message.chaddr = { 'A', 'B', 'C', 'D', 'E', 'F' },
+                .option_type.code = SD_DHCP_OPTION_MESSAGE_TYPE,
+                .option_type.length = 1,
+                .option_type.type = DHCP_DISCOVER,
+                .end = SD_DHCP_OPTION_END,
+        };
+        struct in_addr address_lo = {
+                .s_addr = htobe32(INADDR_LOOPBACK),
+        };
+        struct in_addr static_lease_address = {
+                .s_addr = htobe32(INADDR_LOOPBACK + 42),
+        };
+        static uint8_t static_lease_client_id[7] = {0x01, 'A', 'B', 'C', 'D', 'E', 'G' };
+
+        log_debug("/* %s */", __func__);
+
+        assert_se(sd_dhcp_server_new(&server, 1) >= 0);
+        assert_se(sd_dhcp_server_configure_pool(server, &address_lo, 8, 0, 0) >= 0);
+        assert_se(sd_dhcp_server_set_static_lease(server, &static_lease_address, static_lease_client_id,
+                                                  ELEMENTSOF(static_lease_client_id)) >= 0);
+        assert_se(sd_dhcp_server_attach_event(server, NULL, 0) >= 0);
+        assert_se(sd_dhcp_server_start(server) >= 0);
+
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+
+        test.end = 0;
+        /* TODO, shouldn't this fail? */
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+        test.end = SD_DHCP_OPTION_END;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+
+        test.option_type.code = 0;
+        test.option_type.length = 0;
+        test.option_type.type = 0;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == -ENOMSG);
+        test.option_type.code = SD_DHCP_OPTION_MESSAGE_TYPE;
+        test.option_type.length = 1;
+        test.option_type.type = DHCP_DISCOVER;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+
+        test.message.op = 0;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == 0);
+        test.message.op = BOOTREQUEST;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+
+        test.message.htype = 0;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+        test.message.htype = ARPHRD_ETHER;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+
+        test.message.hlen = 0;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == -EBADMSG);
+        test.message.hlen = ETHER_ADDR_LEN;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_OFFER);
+
+        test.option_type.type = DHCP_REQUEST;
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == 0);
+        test.option_requested_ip.code = SD_DHCP_OPTION_REQUESTED_IP_ADDRESS;
+        test.option_requested_ip.length = 4;
+        test.option_requested_ip.address = htobe32(0x12345678);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_NAK);
+        test.option_server_id.code = SD_DHCP_OPTION_SERVER_IDENTIFIER;
+        test.option_server_id.length = 4;
+        test.option_server_id.address = htobe32(INADDR_LOOPBACK);
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 3);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_ACK);
+
+        test.option_server_id.address = htobe32(0x12345678);
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 3);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == 0);
+        test.option_server_id.address = htobe32(INADDR_LOOPBACK);
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 4);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == 0);
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 3);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_ACK);
+
+        test.option_client_id.code = SD_DHCP_OPTION_CLIENT_IDENTIFIER;
+        test.option_client_id.length = 7;
+        test.option_client_id.id[0] = 0x01;
+        test.option_client_id.id[1] = 'A';
+        test.option_client_id.id[2] = 'B';
+        test.option_client_id.id[3] = 'C';
+        test.option_client_id.id[4] = 'D';
+        test.option_client_id.id[5] = 'E';
+        test.option_client_id.id[6] = 'F';
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_ACK);
+
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 30);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == 0);
+
+        /* request address reserved for static lease (unmatching client ID) */
+        test.option_client_id.id[6] = 'H';
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 42);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == 0);
+
+        /* request unmatching address */
+        test.option_client_id.id[6] = 'G';
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 41);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == 0);
+
+        /* request matching address */
+        test.option_client_id.id[6] = 'G';
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 42);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_ACK);
+
+        /* try again */
+        test.option_client_id.id[6] = 'G';
+        test.option_requested_ip.address = htobe32(INADDR_LOOPBACK + 42);
+        assert_se(dhcp_server_handle_message(server, (DHCPMessage*)&test, sizeof(test)) == DHCP_ACK);
+}
+
+static uint64_t client_id_hash_helper(DHCPClientId *id, uint8_t key[HASH_KEY_SIZE]) {
+        struct siphash state;
+
+        siphash24_init(&state, key);
+        client_id_hash_func(id, &state);
+
+        return htole64(siphash24_finalize(&state));
+}
+
+static void test_client_id_hash(void) {
+        DHCPClientId a = {
+                .length = 4,
+        }, b = {
+                .length = 4,
+        };
+        uint8_t hash_key[HASH_KEY_SIZE] = {
+                '0', '1', '2', '3', '4', '5', '6', '7',
+                '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
+        };
+
+        log_debug("/* %s */", __func__);
+
+        a.data = (uint8_t*)strdup("abcd");
+        b.data = (uint8_t*)strdup("abcd");
+
+        assert_se(client_id_compare_func(&a, &b) == 0);
+        assert_se(client_id_hash_helper(&a, hash_key) == client_id_hash_helper(&b, hash_key));
+        a.length = 3;
+        assert_se(client_id_compare_func(&a, &b) != 0);
+        a.length = 4;
+        assert_se(client_id_compare_func(&a, &b) == 0);
+        assert_se(client_id_hash_helper(&a, hash_key) == client_id_hash_helper(&b, hash_key));
+
+        b.length = 3;
+        assert_se(client_id_compare_func(&a, &b) != 0);
+        b.length = 4;
+        assert_se(client_id_compare_func(&a, &b) == 0);
+        assert_se(client_id_hash_helper(&a, hash_key) == client_id_hash_helper(&b, hash_key));
+
+        free(b.data);
+        b.data = (uint8_t*)strdup("abce");
+        assert_se(client_id_compare_func(&a, &b) != 0);
+
+        free(a.data);
+        free(b.data);
+}
+
+static void test_static_lease(void) {
+        _cleanup_(sd_dhcp_server_unrefp) sd_dhcp_server *server = NULL;
+
+        log_debug("/* %s */", __func__);
+
+        assert_se(sd_dhcp_server_new(&server, 1) >= 0);
+
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x01020304 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020304 }, sizeof(uint32_t)) >= 0);
+        /* Duplicated entry. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x01020304 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020304 }, sizeof(uint32_t)) == -EEXIST);
+        /* Address is conflicted. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x01020304 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020305 }, sizeof(uint32_t)) == -EEXIST);
+        /* Client ID is conflicted. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x01020305 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020304 }, sizeof(uint32_t)) == -EEXIST);
+
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x01020305 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020305 }, sizeof(uint32_t)) >= 0);
+        /* Remove the previous entry. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x00000000 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020305 }, sizeof(uint32_t)) >= 0);
+        /* Then, set a different address. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x01020306 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020305 }, sizeof(uint32_t)) >= 0);
+        /* Remove again. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x00000000 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020305 }, sizeof(uint32_t)) >= 0);
+        /* Try to remove non-existent entry. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x00000000 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020305 }, sizeof(uint32_t)) >= 0);
+        /* Try to remove non-existent entry. */
+        assert_se(sd_dhcp_server_set_static_lease(server, &(struct in_addr) { .s_addr = 0x00000000 },
+                                                  (uint8_t*) &(uint32_t) { 0x01020306 }, sizeof(uint32_t)) >= 0);
+}
+
+int main(int argc, char *argv[]) {
+        int r;
+
+        test_setup_logging(LOG_DEBUG);
+
+        test_client_id_hash();
+        test_static_lease();
+
+        r = test_basic(true);
+        if (r < 0)
+                return log_tests_skipped_errno(r, "cannot start dhcp server(bound to interface)");
+
+        r = test_basic(false);
+        if (r < 0)
+                return log_tests_skipped_errno(r, "cannot start dhcp server(non-bound to interface)");
+
+        test_message_handler();
+
+        return 0;
+}
diff --git a/src/libsystemd-network/test-dhcp6-client.c b/src/libsystemd-network/test-dhcp6-client.c
new file mode 100644
index 0000000..10233f5
--- /dev/null
+++ b/src/libsystemd-network/test-dhcp6-client.c
@@ -0,0 +1,1039 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include <net/ethernet.h>
+#include <net/if_arp.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "sd-dhcp6-client.h"
+#include "sd-event.h"
+
+#include "dhcp-identifier.h"
+#include "dhcp6-internal.h"
+#include "dhcp6-lease-internal.h"
+#include "dhcp6-protocol.h"
+#include "fd-util.h"
+#include "macro.h"
+#include "memory-util.h"
+#include "socket-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "tests.h"
+#include "time-util.h"
+
+#define DHCP6_CLIENT_EVENT_TEST_ADVERTISED 77
+#define IA_ID_BYTES                                                     \
+        0x0e, 0xcf, 0xa3, 0x7d
+#define IA_NA_ADDRESS1_BYTES                                            \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x78, 0xee, 0x1c, 0xf3, 0x09, 0x3c, 0x55, 0xad
+#define IA_NA_ADDRESS2_BYTES                                            \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x78, 0xee, 0x1c, 0xf3, 0x09, 0x3c, 0x55, 0xae
+#define IA_PD_PREFIX1_BYTES                                             \
+        0x2a, 0x02, 0x81, 0x0d, 0x98, 0x80, 0x37, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+#define IA_PD_PREFIX2_BYTES                                             \
+        0x2a, 0x02, 0x81, 0x0d, 0x98, 0x80, 0x37, 0xc1, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+#define DNS1_BYTES                                                      \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01
+#define DNS2_BYTES                                                      \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x02
+#define SNTP1_BYTES                                                     \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x03
+#define SNTP2_BYTES                                                     \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04
+#define NTP1_BYTES                                                      \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x05
+#define NTP2_BYTES                                                      \
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x06
+#define CLIENT_ID_BYTES                                                 \
+        0x00, 0x02, 0x00, 0x00, 0xab, 0x11, 0x61, 0x77, 0x40, 0xde, 0x13, 0x42, 0xc3, 0xa2
+#define SERVER_ID_BYTES                                                 \
+        0x00, 0x01, 0x00, 0x01, 0x19, 0x40, 0x5c, 0x53, 0x78, 0x2b, 0xcb, 0xb3, 0x6d, 0x53
+
+static const struct in6_addr local_address =
+        { { { 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, } } };
+static const struct in6_addr mcast_address =
+        IN6ADDR_ALL_DHCP6_RELAY_AGENTS_AND_SERVERS_INIT;
+static const struct in6_addr ia_na_address1 = { { { IA_NA_ADDRESS1_BYTES } } };
+static const struct in6_addr ia_na_address2 = { { { IA_NA_ADDRESS2_BYTES } } };
+static const struct in6_addr ia_pd_prefix1 = { { { IA_PD_PREFIX1_BYTES } } };
+static const struct in6_addr ia_pd_prefix2 = { { { IA_PD_PREFIX2_BYTES } } };
+static const struct in6_addr dns1 = { { { DNS1_BYTES } } };
+static const struct in6_addr dns2 = { { { DNS2_BYTES } } };
+static const struct in6_addr sntp1 = { { { SNTP1_BYTES } } };
+static const struct in6_addr sntp2 = { { { SNTP2_BYTES } } };
+static const struct in6_addr ntp1 = { { { NTP1_BYTES } } };
+static const struct in6_addr ntp2 = { { { NTP2_BYTES } } };
+static const uint8_t client_id[] = { CLIENT_ID_BYTES };
+static const uint8_t server_id[] = { SERVER_ID_BYTES };
+static const struct ether_addr mac = {
+        .ether_addr_octet = { 'A', 'B', 'C', '1', '2', '3' },
+};
+static int test_fd[2] = { -1, -1, };
+static int test_ifindex = 42;
+static unsigned test_client_sent_message_count = 0;
+static sd_dhcp6_client *client_ref = NULL;
+
+TEST(client_basic) {
+        _cleanup_(sd_dhcp6_client_unrefp) sd_dhcp6_client *client = NULL;
+        int v;
+
+        assert_se(sd_dhcp6_client_new(&client) >= 0);
+        assert_se(client);
+
+        assert_se(sd_dhcp6_client_set_ifindex(client, 15) == 0);
+        assert_se(sd_dhcp6_client_set_ifindex(client, 42) >= 0);
+
+        assert_se(sd_dhcp6_client_set_mac(client, mac.ether_addr_octet, sizeof(mac), ARPHRD_ETHER) >= 0);
+
+        assert_se(sd_dhcp6_client_set_fqdn(client, "host") == 1);
+        assert_se(sd_dhcp6_client_set_fqdn(client, "host.domain") == 1);
+        assert_se(sd_dhcp6_client_set_fqdn(client, NULL) == 1);
+        assert_se(sd_dhcp6_client_set_fqdn(client, "~host") == -EINVAL);
+        assert_se(sd_dhcp6_client_set_fqdn(client, "~host.domain") == -EINVAL);
+
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_CLIENTID) == -EINVAL);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_DNS_SERVER) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_NTP_SERVER) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_SNTP_SERVER) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_DOMAIN) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, 10) == -EINVAL);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_NIS_SERVER) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_NISP_SERVER) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_NIS_SERVER) == -EEXIST);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_NISP_SERVER) == -EEXIST);
+
+        assert_se(sd_dhcp6_client_set_information_request(client, 1) >= 0);
+        v = 0;
+        assert_se(sd_dhcp6_client_get_information_request(client, &v) >= 0);
+        assert_se(v);
+        assert_se(sd_dhcp6_client_set_information_request(client, 0) >= 0);
+        v = 42;
+        assert_se(sd_dhcp6_client_get_information_request(client, &v) >= 0);
+        assert_se(v == 0);
+
+        v = 0;
+        assert_se(sd_dhcp6_client_get_address_request(client, &v) >= 0);
+        assert_se(v);
+        v = 0;
+        assert_se(sd_dhcp6_client_set_address_request(client, 1) >= 0);
+        assert_se(sd_dhcp6_client_get_address_request(client, &v) >= 0);
+        assert_se(v);
+        v = 42;
+        assert_se(sd_dhcp6_client_set_address_request(client, 1) >= 0);
+        assert_se(sd_dhcp6_client_get_address_request(client, &v) >= 0);
+        assert_se(v);
+
+        assert_se(sd_dhcp6_client_set_address_request(client, 1) >= 0);
+        assert_se(sd_dhcp6_client_set_prefix_delegation(client, 1) >= 0);
+        v = 0;
+        assert_se(sd_dhcp6_client_get_address_request(client, &v) >= 0);
+        assert_se(v);
+        v = 0;
+        assert_se(sd_dhcp6_client_get_prefix_delegation(client, &v) >= 0);
+        assert_se(v);
+
+        assert_se(sd_dhcp6_client_set_callback(client, NULL, NULL) >= 0);
+
+        assert_se(sd_dhcp6_client_detach_event(client) >= 0);
+}
+
+TEST(parse_domain) {
+        _cleanup_free_ char *domain = NULL;
+        _cleanup_strv_free_ char **list = NULL;
+        uint8_t *data;
+
+        data = (uint8_t []) { 7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'c', 'o', 'm', 0 };
+        assert_se(dhcp6_option_parse_domainname(data, 13, &domain) >= 0);
+        assert_se(domain);
+        assert_se(streq(domain, "example.com"));
+        domain = mfree(domain);
+
+        data = (uint8_t []) { 4, 't', 'e', 's', 't' };
+        assert_se(dhcp6_option_parse_domainname(data, 5, &domain) >= 0);
+        assert_se(domain);
+        assert_se(streq(domain, "test"));
+        domain = mfree(domain);
+
+        data = (uint8_t []) { 0 };
+        assert_se(dhcp6_option_parse_domainname(data, 1, &domain) < 0);
+
+        data = (uint8_t []) { 7, 'e', 'x', 'a', 'm', 'p', 'l', 'e', 3, 'c', 'o', 'm', 0,
+                              6, 'f', 'o', 'o', 'b', 'a', 'r', 0 };
+        assert_se(dhcp6_option_parse_domainname_list(data, 21, &list) >= 0);
+        assert_se(list);
+        assert_se(streq(list[0], "example.com"));
+        assert_se(streq(list[1], "foobar"));
+        assert_se(!list[2]);
+        list = strv_free(list);
+
+        data = (uint8_t []) { 1, 'a', 0, 20, 'b', 'c' };
+        assert_se(dhcp6_option_parse_domainname_list(data, 6, &list) < 0);
+
+        data = (uint8_t []) { 0 , 0 };
+        assert_se(dhcp6_option_parse_domainname_list(data, 2, &list) < 0);
+}
+
+TEST(option) {
+        static const uint8_t packet[] = {
+                'F', 'O', 'O', 'H', 'O', 'G', 'E',
+                0x00, SD_DHCP6_OPTION_ORO, 0x00, 0x07,
+                'A', 'B', 'C', 'D', 'E', 'F', 'G',
+                0x00, SD_DHCP6_OPTION_VENDOR_CLASS, 0x00, 0x09,
+                '1', '2', '3', '4', '5', '6', '7', '8', '9',
+                'B', 'A', 'R',
+        };
+        static const uint8_t result[] = {
+                'F', 'O', 'O', 'H', 'O', 'G', 'E',
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                'B', 'A', 'R',
+        };
+        _cleanup_free_ uint8_t *buf = NULL;
+        size_t offset, pos, optlen;
+        const uint8_t *optval;
+        uint16_t optcode;
+
+        assert_se(sizeof(packet) == sizeof(result));
+
+        offset = 0;
+        assert_se(dhcp6_option_parse(packet, 0, &offset, &optcode, &optlen, &optval) == -EBADMSG);
+
+        offset = 3;
+        assert_se(dhcp6_option_parse(packet, 0, &offset, &optcode, &optlen, &optval) == -EBADMSG);
+
+        /* Tests for reading unaligned data. */
+        assert_se(buf = new(uint8_t, sizeof(packet)));
+        for (size_t i = 0; i <= 7; i++) {
+                memcpy(buf, packet + i, sizeof(packet) - i);
+                offset = 7 - i;
+                assert_se(dhcp6_option_parse(buf, sizeof(packet), &offset, &optcode, &optlen, &optval) >= 0);
+
+                assert_se(optcode == SD_DHCP6_OPTION_ORO);
+                assert_se(optlen == 7);
+                assert_se(optval == buf + 11 - i);
+        }
+
+        offset = 7;
+        assert_se(dhcp6_option_parse(packet, sizeof(packet), &offset, &optcode, &optlen, &optval) >= 0);
+
+        assert_se(optcode == SD_DHCP6_OPTION_ORO);
+        assert_se(optlen == 7);
+        assert_se(optval == packet + 11);
+
+        free(buf);
+        assert_se(buf = memdup(result, sizeof(result)));
+        pos = 7;
+        assert_se(dhcp6_option_append(&buf, &pos, optcode, optlen, optval) >= 0);
+
+        assert_se(dhcp6_option_parse(packet, sizeof(packet), &offset, &optcode, &optlen, &optval) >= 0);
+
+        assert_se(optcode == SD_DHCP6_OPTION_VENDOR_CLASS);
+        assert_se(optlen == 9);
+        assert_se(optval == packet + 22);
+
+        assert_se(dhcp6_option_append(&buf, &pos, optcode, optlen, optval) >= 0);
+
+        assert_se(memcmp(packet, buf, sizeof(packet)) == 0);
+}
+
+TEST(option_status) {
+        uint8_t option1[] = {
+                /* IA NA */
+                0x00, 0x03, 0x00, 0x12, 0x1a, 0x1d, 0x1a, 0x1d,
+                0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x02,
+                /* status option */
+                0x00, 0x0d, 0x00, 0x02, 0x00, 0x01,
+        };
+        static const uint8_t option2[] = {
+                /* IA NA */
+                0x00, 0x03, 0x00, 0x2e, 0x1a, 0x1d, 0x1a, 0x1d,
+                0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x02,
+                /* IA Addr */
+                0x00, 0x05, 0x00, 0x1e,
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+                0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10,
+                0x01, 0x02, 0x03, 0x04, 0x0a, 0x0b, 0x0c, 0x0d,
+                /* IA address status option */
+                0x00, 0x0d, 0x00, 0x02, 0x00, 0x01,
+        };
+        static const uint8_t option3[] = {
+                /* IA NA */
+                0x00, 0x03, 0x00, 0x34, 0x1a, 0x1d, 0x1a, 0x1d,
+                0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x02,
+                /* IA Addr */
+                0x00, 0x05, 0x00, 0x24,
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+                0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10,
+                0x01, 0x02, 0x03, 0x04, 0x0a, 0x0b, 0x0c, 0x0d,
+                /* IA address status option */
+                0x00, 0x0d, 0x00, 0x08, 0x00, 0x00, 'f',  'o',
+                'o',  'b',  'a',  'r',
+        };
+        static const uint8_t option4[] = {
+                /* IA PD */
+                0x00, 0x19, 0x00, 0x2f, 0x1a, 0x1d, 0x1a, 0x1d,
+                0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x02,
+                /* IA PD Prefix */
+                0x00, 0x1a, 0x00, 0x1f,
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+                0x80, 0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe,
+                0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x00,
+                /* PD prefix status option */
+                0x00, 0x0d, 0x00, 0x02, 0x00, 0x00,
+        };
+        static const uint8_t option5[] = {
+                /* IA PD */
+                0x00, 0x19, 0x00, 0x52, 0x1a, 0x1d, 0x1a, 0x1d,
+                0x00, 0x01, 0x00, 0x01, 0x00, 0x02, 0x00, 0x02,
+                /* IA PD Prefix #1 */
+                0x00, 0x1a, 0x00, 0x1f,
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+                0x80, 0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe,
+                0xef, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x00,
+                /* PD prefix status option */
+                0x00, 0x0d, 0x00, 0x02, 0x00, 0x00,
+                /* IA PD Prefix #2 */
+                0x00, 0x1a, 0x00, 0x1f,
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+                0x80, 0x20, 0x01, 0x0d, 0xb8, 0xc0, 0x0l, 0xd0,
+                0x0d, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x00,
+                /* PD prefix status option */
+                0x00, 0x0d, 0x00, 0x02, 0x00, 0x00,
+        };
+        _cleanup_(dhcp6_ia_freep) DHCP6IA *ia = NULL;
+        DHCP6Option *option;
+        be32_t iaid;
+        int r;
+
+        memcpy(&iaid, option1 + 4, sizeof(iaid));
+
+        option = (DHCP6Option*) option1;
+        assert_se(sizeof(option1) == sizeof(DHCP6Option) + be16toh(option->len));
+
+        r = dhcp6_option_parse_ia(NULL, 0, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r == -ENOANO);
+
+        r = dhcp6_option_parse_ia(NULL, iaid, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r == -EINVAL);
+
+        option->len = htobe16(17);
+        r = dhcp6_option_parse_ia(NULL, iaid, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r == -EBADMSG);
+
+        option->len = htobe16(sizeof(DHCP6Option));
+        r = dhcp6_option_parse_ia(NULL, iaid, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r == -EBADMSG);
+
+        option = (DHCP6Option*) option2;
+        assert_se(sizeof(option2) == sizeof(DHCP6Option) + be16toh(option->len));
+        r = dhcp6_option_parse_ia(NULL, iaid, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r == -ENODATA);
+
+        option = (DHCP6Option*) option3;
+        assert_se(sizeof(option3) == sizeof(DHCP6Option) + be16toh(option->len));
+        r = dhcp6_option_parse_ia(NULL, iaid, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r >= 0);
+        assert_se(ia);
+        assert_se(ia->addresses);
+        ia = dhcp6_ia_free(ia);
+
+        option = (DHCP6Option*) option4;
+        assert_se(sizeof(option4) == sizeof(DHCP6Option) + be16toh(option->len));
+        r = dhcp6_option_parse_ia(NULL, iaid, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r >= 0);
+        assert_se(ia);
+        assert_se(ia->addresses);
+        assert_se(memcmp(&ia->header.id, &option4[4], 4) == 0);
+        assert_se(memcmp(&ia->header.lifetime_t1, &option4[8], 4) == 0);
+        assert_se(memcmp(&ia->header.lifetime_t2, &option4[12], 4) == 0);
+        ia = dhcp6_ia_free(ia);
+
+        option = (DHCP6Option*) option5;
+        assert_se(sizeof(option5) == sizeof(DHCP6Option) + be16toh(option->len));
+        r = dhcp6_option_parse_ia(NULL, iaid, be16toh(option->code), be16toh(option->len), option->data, &ia);
+        assert_se(r >= 0);
+        assert_se(ia);
+        assert_se(ia->addresses);
+        ia = dhcp6_ia_free(ia);
+}
+
+TEST(client_parse_message_issue_22099) {
+        static const uint8_t msg[] = {
+                /* Message type */
+                DHCP6_MESSAGE_REPLY,
+                /* Transaction ID */
+                0x7c, 0x4c, 0x16,
+                /* Rapid commit */
+                0x00, SD_DHCP6_OPTION_RAPID_COMMIT, 0x00, 0x00,
+                /* NTP servers */
+                0x00, SD_DHCP6_OPTION_NTP_SERVER, 0x00, 0x14,
+                /* NTP server (broken sub option and sub option length) */
+                0x01, 0x00, 0x10, 0x00,
+                0xfd, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xde, 0x15, 0xc8, 0xff, 0xfe, 0xef, 0x1e, 0x4e,
+                /* Client ID */
+                0x00, SD_DHCP6_OPTION_CLIENTID, 0x00, 0x0e,
+                0x00, 0x02, /* DUID-EN */
+                0x00, 0x00, 0xab, 0x11, /* pen */
+                0x5c, 0x6b, 0x90, 0xec, 0xda, 0x95, 0x15, 0x45, /* id */
+                /* Server ID */
+                0x00, SD_DHCP6_OPTION_SERVERID, 0x00, 0x0a,
+                0x00, 0x03, /* DUID-LL */
+                0x00, 0x01, /* htype */
+                0xdc, 0x15, 0xc8, 0xef, 0x1e, 0x4e, /* haddr */
+                /* preference */
+                0x00, SD_DHCP6_OPTION_PREFERENCE, 0x00, 0x01,
+                0x00,
+                /* DNS servers */
+                0x00, SD_DHCP6_OPTION_DNS_SERVER, 0x00, 0x10,
+                0xfd, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xde, 0x15, 0xc8, 0xff, 0xfe, 0xef, 0x1e, 0x4e,
+                /* v6 pcp server */
+                0x00, SD_DHCP6_OPTION_V6_PCP_SERVER, 0x00, 0x10,
+                0x2a, 0x02, 0x81, 0x0d, 0x98, 0x80, 0x37, 0x00, 0xde, 0x15, 0xc8, 0xff, 0xfe, 0xef, 0x1e, 0x4e,
+                /* IA_NA */
+                0x00, SD_DHCP6_OPTION_IA_NA, 0x00, 0x28,
+                0xcc, 0x59, 0x11, 0x7b, /* iaid */
+                0x00, 0x00, 0x07, 0x08, /* lifetime T1 */
+                0x00, 0x00, 0x0b, 0x40, /* lifetime T2 */
+                /* IA_NA (iaaddr suboption) */
+                0x00, SD_DHCP6_OPTION_IAADDR, 0x00, 0x18,
+                0x2a, 0x02, 0x81, 0x0d, 0x98, 0x80, 0x37, 0x00, 0x6a, 0x05, 0xca, 0xff, 0xfe, 0xf1, 0x51, 0x53, /* address */
+                0x00, 0x00, 0x0e, 0x10, /* preferred lifetime */
+                0x00, 0x00, 0x1c, 0x20, /* valid lifetime */
+                /* IA_PD */
+                0x00, SD_DHCP6_OPTION_IA_PD, 0x00, 0x29,
+                0xcc, 0x59, 0x11, 0x7b, /* iaid */
+                0x00, 0x00, 0x07, 0x08, /* lifetime T1 */
+                0x00, 0x00, 0x0b, 0x40, /* lifetime T2 */
+                /* IA_PD (iaprefix suboption) */
+                0x00, SD_DHCP6_OPTION_IA_PD_PREFIX, 0x00, 0x19,
+                0x00, 0x00, 0x0e, 0x10, /* preferred lifetime */
+                0x00, 0x00, 0x1c, 0x20, /* valid lifetime */
+                0x3a, /* prefixlen */
+                0x2a, 0x02, 0x81, 0x0d, 0x98, 0x80, 0x37, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* prefix */
+        };
+        static const uint8_t duid[] = {
+                0x00, 0x00, 0xab, 0x11, 0x5c, 0x6b, 0x90, 0xec, 0xda, 0x95, 0x15, 0x45,
+        };
+        _cleanup_(sd_dhcp6_client_unrefp) sd_dhcp6_client *client = NULL;
+        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
+
+        assert_se(sd_dhcp6_client_new(&client) >= 0);
+        assert_se(sd_dhcp6_client_set_iaid(client, 0xcc59117b) >= 0);
+        assert_se(sd_dhcp6_client_set_duid(client, 2, duid, sizeof(duid)) >= 0);
+
+        assert_se(dhcp6_lease_new_from_message(client, (const DHCP6Message*) msg, sizeof(msg), NULL, NULL, &lease) >= 0);
+}
+
+TEST(client_parse_message_issue_24002) {
+        static const uint8_t msg[] = {
+                /* Message Type */
+                0x07,
+                /* Transaction ID */
+                0x0e, 0xa5, 0x7c,
+                /* Client ID */
+                0x00, SD_DHCP6_OPTION_CLIENTID, 0x00, 0x0e,
+                0x00, 0x02, /* DUID-EN */
+                0x00, 0x00, 0xab, 0x11, /* pen */
+                0x5c, 0x6b, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff, /* id */
+                /* Server ID */
+                0x00, 0x02, 0x00, 0x1a,
+                0x00, 0x02, 0x00, 0x00, 0x05, 0x83, 0x30, 0x63, 0x3a, 0x38, 0x00, 0x11, 0x22, 0x33, 0x44, 0x55,
+                0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff,
+                /* IA_PD */
+                0x00, 0x19, 0x00, 0x29,
+                0xaa, 0xbb, 0xcc, 0xdd, /* iaid */
+                0x00, 0x00, 0x03, 0x84, /* lifetime (T1) */
+                0x00, 0x00, 0x05, 0xa0, /* lifetime (T2) */
+                /* IA_PD (iaprefix suboption) */
+                0x00, 0x1a, 0x00, 0x19,
+                0x00, 0x00, 0x07, 0x08, /* preferred lifetime */
+                0x00, 0x00, 0x38, 0x40, /* valid lifetime */
+                0x38, /* prefixlen */
+                0x20, 0x03, 0x00, 0xff, 0xaa, 0xbb, 0xcc, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, /* prefix */
+                /* Rapid commit */
+                0x00, 0x0e, 0x00, 0x00,
+                /* Trailing invalid byte at the end. See issue #28183. */
+                00,
+        };
+        static const uint8_t duid[] = {
+                0x00, 0x00, 0xab, 0x11, 0x5c, 0x6b, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff,
+        };
+        _cleanup_(sd_dhcp6_client_unrefp) sd_dhcp6_client *client = NULL;
+        _cleanup_(sd_dhcp6_lease_unrefp) sd_dhcp6_lease *lease = NULL;
+
+        assert_se(sd_dhcp6_client_new(&client) >= 0);
+        assert_se(sd_dhcp6_client_set_iaid(client, 0xaabbccdd) >= 0);
+        assert_se(sd_dhcp6_client_set_duid(client, 2, duid, sizeof(duid)) >= 0);
+
+        assert_se(dhcp6_lease_new_from_message(client, (const DHCP6Message*) msg, sizeof(msg), NULL, NULL, &lease) >= 0);
+}
+
+static const uint8_t msg_information_request[] = {
+        /* Message type */
+        DHCP6_MESSAGE_INFORMATION_REQUEST,
+        /* Transaction ID */
+        0x0f, 0xb4, 0xe5,
+        /* MUD URL */
+        /* ORO */
+        0x00, SD_DHCP6_OPTION_ORO, 0x00, 0x0c,
+        0x00, SD_DHCP6_OPTION_DNS_SERVER,
+        0x00, SD_DHCP6_OPTION_DOMAIN,
+        0x00, SD_DHCP6_OPTION_SNTP_SERVER,
+        0x00, SD_DHCP6_OPTION_INFORMATION_REFRESH_TIME,
+        0x00, SD_DHCP6_OPTION_NTP_SERVER,
+        0x00, SD_DHCP6_OPTION_INF_MAX_RT,
+        /* Client ID */
+        0x00, SD_DHCP6_OPTION_CLIENTID, 0x00, 0x0e,
+        CLIENT_ID_BYTES,
+        /* Extra options */
+        /* Elapsed time */
+        0x00, SD_DHCP6_OPTION_ELAPSED_TIME, 0x00, 0x02,
+        0x00, 0x00,
+};
+
+static const uint8_t msg_solicit[] = {
+        /* Message type */
+        DHCP6_MESSAGE_SOLICIT,
+        /* Transaction ID */
+        0x0f, 0xb4, 0xe5,
+        /* Rapid commit */
+        0x00, SD_DHCP6_OPTION_RAPID_COMMIT, 0x00, 0x00,
+        /* IA_NA */
+        0x00, SD_DHCP6_OPTION_IA_NA, 0x00, 0x0c,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x00, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x00, /* lifetime T2 */
+        /* IA_PD */
+        0x00, SD_DHCP6_OPTION_IA_PD, 0x00, 0x0c,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x00, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x00, /* lifetime T2 */
+        /* Client FQDN */
+        0x00, SD_DHCP6_OPTION_CLIENT_FQDN, 0x00, 0x11,
+        DHCP6_FQDN_FLAG_S,
+        0x04, 'h', 'o', 's', 't', 0x03, 'l', 'a', 'b', 0x05, 'i', 'n', 't', 'r', 'a', 0x00,
+        /* User Class */
+        /* Vendor Class */
+        /* Vendor Options */
+        /* MUD URL */
+        /* ORO */
+        0x00, SD_DHCP6_OPTION_ORO, 0x00, 0x0a,
+        0x00, SD_DHCP6_OPTION_DNS_SERVER,
+        0x00, SD_DHCP6_OPTION_DOMAIN,
+        0x00, SD_DHCP6_OPTION_SNTP_SERVER,
+        0x00, SD_DHCP6_OPTION_NTP_SERVER,
+        0x00, SD_DHCP6_OPTION_SOL_MAX_RT,
+        /* Client ID */
+        0x00, SD_DHCP6_OPTION_CLIENTID, 0x00, 0x0e,
+        CLIENT_ID_BYTES,
+        /* Extra options */
+        /* Elapsed time */
+        0x00, SD_DHCP6_OPTION_ELAPSED_TIME, 0x00, 0x02,
+        0x00, 0x00,
+};
+
+static const uint8_t msg_request[] = {
+        /* Message type */
+        DHCP6_MESSAGE_REQUEST,
+        /* Transaction ID */
+        0x00, 0x00, 0x00,
+        /* Server ID */
+        0x00, SD_DHCP6_OPTION_SERVERID, 0x00, 0x0e,
+        SERVER_ID_BYTES,
+        /* IA_NA */
+        0x00, SD_DHCP6_OPTION_IA_NA, 0x00, 0x44,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x00, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x00, /* lifetime T2 */
+        /* IA_NA (IAADDR suboption) */
+        0x00, SD_DHCP6_OPTION_IAADDR, 0x00, 0x18,
+        IA_NA_ADDRESS1_BYTES,
+        0x00, 0x00, 0x00, 0x00, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0x00, /* valid lifetime */
+        /* IA_NA (IAADDR suboption) */
+        0x00, SD_DHCP6_OPTION_IAADDR, 0x00, 0x18,
+        IA_NA_ADDRESS2_BYTES,
+        0x00, 0x00, 0x00, 0x00, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0x00, /* valid lifetime */
+        /* IA_PD */
+        0x00, SD_DHCP6_OPTION_IA_PD, 0x00, 0x46,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x00, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x00, /* lifetime T2 */
+        /* IA_PD (IA_PD_PREFIX suboption) */
+        0x00, SD_DHCP6_OPTION_IA_PD_PREFIX, 0x00, 0x19,
+        0x00, 0x00, 0x00, 0x00, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0x00, /* valid lifetime */
+        0x40, /* prefixlen */
+        IA_PD_PREFIX1_BYTES,
+        /* IA_PD (IA_PD_PREFIX suboption) */
+        0x00, SD_DHCP6_OPTION_IA_PD_PREFIX, 0x00, 0x19,
+        0x00, 0x00, 0x00, 0x00, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0x00, /* valid lifetime */
+        0x40, /* prefixlen */
+        IA_PD_PREFIX2_BYTES,
+        /* Client FQDN */
+        0x00, SD_DHCP6_OPTION_CLIENT_FQDN, 0x00, 0x11,
+        DHCP6_FQDN_FLAG_S,
+        0x04, 'h', 'o', 's', 't', 0x03, 'l', 'a', 'b', 0x05, 'i', 'n', 't', 'r', 'a', 0x00,
+        /* User Class */
+        /* Vendor Class */
+        /* Vendor Options */
+        /* MUD URL */
+        /* ORO */
+        0x00, SD_DHCP6_OPTION_ORO, 0x00, 0x08,
+        0x00, SD_DHCP6_OPTION_DNS_SERVER,
+        0x00, SD_DHCP6_OPTION_DOMAIN,
+        0x00, SD_DHCP6_OPTION_SNTP_SERVER,
+        0x00, SD_DHCP6_OPTION_NTP_SERVER,
+        /* Client ID */
+        0x00, SD_DHCP6_OPTION_CLIENTID, 0x00, 0x0e,
+        CLIENT_ID_BYTES,
+        /* Extra options */
+        /* Elapsed time */
+        0x00, SD_DHCP6_OPTION_ELAPSED_TIME, 0x00, 0x02,
+        0x00, 0x00,
+};
+
+static const uint8_t msg_reply[] = {
+        /* Message type */
+        DHCP6_MESSAGE_REPLY,
+        /* Transaction ID */
+        0x0f, 0xb4, 0xe5,
+        /* Client ID */
+        0x00, SD_DHCP6_OPTION_CLIENTID, 0x00, 0x0e,
+        CLIENT_ID_BYTES,
+        /* Server ID */
+        0x00, SD_DHCP6_OPTION_SERVERID, 0x00, 0x0e,
+        SERVER_ID_BYTES,
+        /* Rapid commit */
+        0x00, SD_DHCP6_OPTION_RAPID_COMMIT, 0x00, 0x01,
+        0x00,
+        /* IA_NA */
+        0x00, SD_DHCP6_OPTION_IA_NA, 0x00, 0x66,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x50, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x78, /* lifetime T2 */
+        /* IA_NA (IAADDR suboption) */
+        0x00, SD_DHCP6_OPTION_IAADDR, 0x00, 0x18,
+        IA_NA_ADDRESS2_BYTES,
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        /* IA_NA (IAADDR suboption) */
+        0x00, SD_DHCP6_OPTION_IAADDR, 0x00, 0x18,
+        IA_NA_ADDRESS1_BYTES,
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        /* IA_NA (status code suboption) */
+        0x00, SD_DHCP6_OPTION_STATUS_CODE, 0x00, 0x1e,
+        0x00, 0x00, /* status code */
+        0x41, 0x6c, 0x6c, 0x20, 0x61, 0x64, 0x64, 0x72, 0x65, 0x73, 0x73, 0x65, 0x73, 0x20, 0x77, 0x65,
+        0x72, 0x65, 0x20, 0x61, 0x73, 0x73, 0x69, 0x67, 0x6e, 0x65, 0x64, 0x2e, /* status message */
+        /* IA_PD */
+        0x00, SD_DHCP6_OPTION_IA_PD, 0x00, 0x46,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x50, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x78, /* lifetime T2 */
+        /* IA_PD (IA_PD_PREFIX suboption) */
+        0x00, SD_DHCP6_OPTION_IA_PD_PREFIX, 0x00, 0x19,
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        0x40, /* prefixlen */
+        IA_PD_PREFIX2_BYTES,
+        /* IA_PD (IA_PD_PREFIX suboption) */
+        0x00, SD_DHCP6_OPTION_IA_PD_PREFIX, 0x00, 0x19,
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        0x40, /* prefixlen */
+        IA_PD_PREFIX1_BYTES,
+        /* DNS servers */
+        0x00, SD_DHCP6_OPTION_DNS_SERVER, 0x00, 0x20,
+        DNS1_BYTES,
+        DNS2_BYTES,
+        /* SNTP servers */
+        0x00, SD_DHCP6_OPTION_SNTP_SERVER, 0x00, 0x20,
+        SNTP1_BYTES,
+        SNTP2_BYTES,
+        /* NTP servers */
+        0x00, SD_DHCP6_OPTION_NTP_SERVER, 0x00, 0x37,
+        /* NTP server (address suboption) */
+        0x00, DHCP6_NTP_SUBOPTION_SRV_ADDR, 0x00, 0x10,
+        NTP1_BYTES,
+        /* NTP server (address suboption) */
+        0x00, DHCP6_NTP_SUBOPTION_SRV_ADDR, 0x00, 0x10,
+        NTP2_BYTES,
+        /* NTP server (fqdn suboption) */
+        0x00, DHCP6_NTP_SUBOPTION_SRV_FQDN, 0x00, 0x0b,
+        0x03, 'n', 't', 'p', 0x05, 'i', 'n', 't', 'r', 'a', 0x00,
+        /* Domain list */
+        0x00, SD_DHCP6_OPTION_DOMAIN, 0x00, 0x0b,
+        0x03, 'l', 'a', 'b', 0x05, 'i', 'n', 't', 'r', 'a', 0x00,
+        /* Client FQDN */
+        0x00, SD_DHCP6_OPTION_CLIENT_FQDN, 0x00, 0x12,
+        0x01, 0x06, 'c', 'l', 'i', 'e', 'n', 't', 0x03, 'l', 'a', 'b', 0x05, 'i', 'n', 't', 'r', 'a',
+};
+
+static const uint8_t msg_advertise[] = {
+        /* Message type */
+        DHCP6_MESSAGE_ADVERTISE,
+        /* Transaction ID */
+        0x0f, 0xb4, 0xe5,
+        /* Client ID */
+        0x00, SD_DHCP6_OPTION_CLIENTID, 0x00, 0x0e,
+        CLIENT_ID_BYTES,
+        /* Server ID */
+        0x00, SD_DHCP6_OPTION_SERVERID, 0x00, 0x0e,
+        SERVER_ID_BYTES,
+        /* Preference */
+        0x00, SD_DHCP6_OPTION_PREFERENCE, 0x00, 0x01,
+        0xff,
+        /* IA_NA */
+        0x00, SD_DHCP6_OPTION_IA_NA, 0x00, 0x7a,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x50, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x78, /* lifetime T2 */
+        /* IA_NA (IAADDR suboption) */
+        0x00, SD_DHCP6_OPTION_IAADDR, 0x00, 0x18,
+        IA_NA_ADDRESS2_BYTES, /* address */
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        /* IA_NA (IAADDR suboption) */
+        0x00, SD_DHCP6_OPTION_IAADDR, 0x00, 0x18,
+        IA_NA_ADDRESS1_BYTES, /* address */
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        /* IA_NA (status code suboption) */
+        0x00, SD_DHCP6_OPTION_STATUS_CODE, 0x00, 0x32,
+        0x00, 0x00, /* status code */
+        0x41, 0x64, 0x64, 0x72, 0x65, 0x73, 0x73, 0x28, 0x65, 0x73, 0x29, 0x20, 0x72, 0x65, 0x6e, 0x65,
+        0x77, 0x65, 0x64, 0x2e, 0x20, 0x47, 0x72, 0x65, 0x65, 0x74, 0x69, 0x6e, 0x67, 0x73, 0x20, 0x66,
+        0x72, 0x6f, 0x6d, 0x20, 0x70, 0x6c, 0x61, 0x6e, 0x65, 0x74, 0x20, 0x45, 0x61, 0x72, 0x74, 0x68, /* status message */
+        /* IA_PD */
+        0x00, SD_DHCP6_OPTION_IA_PD, 0x00, 0x46,
+        IA_ID_BYTES,
+        0x00, 0x00, 0x00, 0x50, /* lifetime T1 */
+        0x00, 0x00, 0x00, 0x78, /* lifetime T2 */
+        /* IA_PD (IA_PD_PREFIX suboption) */
+        0x00, SD_DHCP6_OPTION_IA_PD_PREFIX, 0x00, 0x19,
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        0x40, /* prefixlen */
+        IA_PD_PREFIX2_BYTES,
+        /* IA_PD (IA_PD_PREFIX suboption) */
+        0x00, SD_DHCP6_OPTION_IA_PD_PREFIX, 0x00, 0x19,
+        0x00, 0x00, 0x00, 0x96, /* preferred lifetime */
+        0x00, 0x00, 0x00, 0xb4, /* valid lifetime */
+        0x40, /* prefixlen */
+        IA_PD_PREFIX1_BYTES,
+        /* DNS servers */
+        0x00, SD_DHCP6_OPTION_DNS_SERVER, 0x00, 0x20,
+        DNS1_BYTES,
+        DNS2_BYTES,
+        /* SNTP servers */
+        0x00, SD_DHCP6_OPTION_SNTP_SERVER, 0x00, 0x20,
+        SNTP1_BYTES,
+        SNTP2_BYTES,
+        /* NTP servers */
+        0x00, SD_DHCP6_OPTION_NTP_SERVER, 0x00, 0x37,
+        /* NTP server (address suboption) */
+        0x00, DHCP6_NTP_SUBOPTION_SRV_ADDR, 0x00, 0x10,
+        NTP1_BYTES,
+        /* NTP server (address suboption) */
+        0x00, DHCP6_NTP_SUBOPTION_SRV_ADDR, 0x00, 0x10,
+        NTP2_BYTES,
+        /* NTP server (fqdn suboption) */
+        0x00, DHCP6_NTP_SUBOPTION_SRV_FQDN, 0x00, 0x0b,
+        0x03, 'n', 't', 'p', 0x05, 'i', 'n', 't', 'r', 'a', 0x00,
+        /* Domain list */
+        0x00, SD_DHCP6_OPTION_DOMAIN, 0x00, 0x0b,
+        0x03, 'l', 'a', 'b', 0x05, 'i', 'n', 't', 'r', 'a', 0x00,
+        /* Client FQDN */
+        0x00, SD_DHCP6_OPTION_CLIENT_FQDN, 0x00, 0x12,
+        0x01, 0x06, 'c', 'l', 'i', 'e', 'n', 't', 0x03, 'l', 'a', 'b', 0x05, 'i', 'n', 't', 'r', 'a',
+};
+
+static void test_client_verify_information_request(const DHCP6Message *msg, size_t len) {
+        log_debug("/* %s */", __func__);
+
+        assert_se(len == sizeof(msg_information_request));
+        /* The elapsed time value is not deterministic. Skip it. */
+        assert_se(memcmp(msg, msg_information_request, len - sizeof(be16_t)) == 0);
+}
+
+static void test_client_verify_solicit(const DHCP6Message *msg, size_t len) {
+        log_debug("/* %s */", __func__);
+
+        assert_se(len == sizeof(msg_solicit));
+        /* The elapsed time value is not deterministic. Skip it. */
+        assert_se(memcmp(msg, msg_solicit, len - sizeof(be16_t)) == 0);
+}
+
+static void test_client_verify_request(const DHCP6Message *msg, size_t len) {
+        log_debug("/* %s */", __func__);
+
+        assert_se(len == sizeof(msg_request));
+        assert_se(msg->type == DHCP6_MESSAGE_REQUEST);
+        /* The transaction ID and elapsed time value are not deterministic. Skip them. */
+        assert_se(memcmp(msg->options, msg_request + offsetof(DHCP6Message, options), len - offsetof(DHCP6Message, options) - sizeof(be16_t)) == 0);
+}
+
+static void test_lease_common(sd_dhcp6_client *client) {
+        sd_dhcp6_lease *lease;
+        const struct in6_addr *addrs;
+        const char *str;
+        char **strv;
+        uint8_t *id;
+        size_t len;
+
+        assert_se(sd_dhcp6_client_get_lease(client, &lease) >= 0);
+
+        assert_se(dhcp6_lease_get_clientid(lease, &id, &len) >= 0);
+        assert_se(memcmp_nn(id, len, client_id, sizeof(client_id)) == 0);
+
+        assert_se(sd_dhcp6_lease_get_domains(lease, &strv) == 1);
+        assert_se(streq(strv[0], "lab.intra"));
+        assert_se(!strv[1]);
+
+        assert_se(sd_dhcp6_lease_get_fqdn(lease, &str) >= 0);
+        assert_se(streq(str, "client.lab.intra"));
+
+        assert_se(sd_dhcp6_lease_get_dns(lease, &addrs) == 2);
+        assert_se(in6_addr_equal(&addrs[0], &dns1));
+        assert_se(in6_addr_equal(&addrs[1], &dns2));
+
+        assert_se(sd_dhcp6_lease_get_ntp_addrs(lease, &addrs) == 2);
+        assert_se(in6_addr_equal(&addrs[0], &ntp1));
+        assert_se(in6_addr_equal(&addrs[1], &ntp2));
+
+        assert_se(sd_dhcp6_lease_get_ntp_fqdn(lease, &strv) == 1);
+        assert_se(streq(strv[0], "ntp.intra"));
+        assert_se(!strv[1]);
+
+        assert_se(lease->sntp_count == 2);
+        assert_se(in6_addr_equal(&lease->sntp[0], &sntp1));
+        assert_se(in6_addr_equal(&lease->sntp[1], &sntp2));
+}
+
+static void test_lease_managed(sd_dhcp6_client *client) {
+        sd_dhcp6_lease *lease;
+        struct in6_addr addr;
+        uint32_t lt_pref, lt_valid;
+        uint8_t *id, prefixlen;
+        size_t len;
+
+        assert_se(sd_dhcp6_client_get_lease(client, &lease) >= 0);
+
+        assert_se(dhcp6_lease_get_serverid(lease, &id, &len) >= 0);
+        assert_se(memcmp_nn(id, len, server_id, sizeof(server_id)) == 0);
+
+        sd_dhcp6_lease_reset_address_iter(lease);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_na_address1));
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_na_address2));
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) == -ENODATA);
+
+        sd_dhcp6_lease_reset_address_iter(lease);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_na_address1));
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_na_address2));
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) == -ENODATA);
+
+        sd_dhcp6_lease_reset_pd_prefix_iter(lease);
+        assert_se(sd_dhcp6_lease_get_pd(lease, &addr, &prefixlen, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_pd_prefix1));
+        assert_se(prefixlen == 64);
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_pd(lease, &addr, &prefixlen, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_pd_prefix2));
+        assert_se(prefixlen == 64);
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) == -ENODATA);
+
+        sd_dhcp6_lease_reset_pd_prefix_iter(lease);
+        assert_se(sd_dhcp6_lease_get_pd(lease, &addr, &prefixlen, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_pd_prefix1));
+        assert_se(prefixlen == 64);
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_pd(lease, &addr, &prefixlen, &lt_pref, &lt_valid) >= 0);
+        assert_se(in6_addr_equal(&addr, &ia_pd_prefix2));
+        assert_se(prefixlen == 64);
+        assert_se(lt_pref == 150);
+        assert_se(lt_valid == 180);
+        assert_se(sd_dhcp6_lease_get_address(lease, &addr, &lt_pref, &lt_valid) == -ENODATA);
+
+        test_lease_common(client);
+}
+
+static void test_client_callback(sd_dhcp6_client *client, int event, void *userdata) {
+        switch (event) {
+        case SD_DHCP6_CLIENT_EVENT_STOP:
+                log_debug("/* %s (event=stop) */", __func__);
+                return;
+
+        case SD_DHCP6_CLIENT_EVENT_INFORMATION_REQUEST:
+                log_debug("/* %s (event=information-request) */", __func__);
+
+                assert_se(test_client_sent_message_count == 1);
+
+                test_lease_common(client);
+
+                assert_se(sd_dhcp6_client_set_information_request(client, false) >= 0);
+                assert_se(sd_dhcp6_client_start(client) >= 0);
+                assert_se(dhcp6_client_set_transaction_id(client, ((const DHCP6Message*) msg_advertise)->transaction_id) >= 0);
+                break;
+
+        case SD_DHCP6_CLIENT_EVENT_IP_ACQUIRE:
+                log_debug("/* %s (event=ip-acquire) */", __func__);
+
+                assert_se(IN_SET(test_client_sent_message_count, 3, 4));
+
+                test_lease_managed(client);
+
+                switch (test_client_sent_message_count) {
+                case 3:
+                        assert_se(sd_dhcp6_client_stop(client) >= 0);
+                        assert_se(sd_dhcp6_client_start(client) >= 0);
+                        assert_se(dhcp6_client_set_transaction_id(client, ((const DHCP6Message*) msg_reply)->transaction_id) >= 0);
+                        break;
+
+                case 4:
+                        assert_se(sd_event_exit(sd_dhcp6_client_get_event(client), 0) >= 0);
+                        break;
+
+                default:
+                        assert_not_reached();
+                }
+
+                break;
+
+        case DHCP6_CLIENT_EVENT_TEST_ADVERTISED: {
+                sd_dhcp6_lease *lease;
+                uint8_t preference;
+
+                log_debug("/* %s (event=test-advertised) */", __func__);
+
+                assert_se(test_client_sent_message_count == 2);
+
+                test_lease_managed(client);
+
+                assert_se(sd_dhcp6_client_get_lease(client, &lease) >= 0);
+                assert_se(dhcp6_lease_get_preference(lease, &preference) >= 0);
+                assert_se(preference == 0xff);
+
+                assert_se(dhcp6_client_set_transaction_id(client, ((const DHCP6Message*) msg_reply)->transaction_id) >= 0);
+                break;
+        }
+        default:
+                assert_not_reached();
+        }
+}
+
+int dhcp6_network_send_udp_socket(int s, struct in6_addr *a, const void *packet, size_t len) {
+        log_debug("/* %s(count=%u) */", __func__, test_client_sent_message_count);
+
+        assert_se(a);
+        assert_se(in6_addr_equal(a, &mcast_address));
+        assert_se(packet);
+        assert_se(len >= sizeof(DHCP6Message));
+
+        switch (test_client_sent_message_count) {
+        case 0:
+                test_client_verify_information_request(packet, len);
+                assert_se(write(test_fd[1], msg_reply, sizeof(msg_reply)) == sizeof(msg_reply));
+                break;
+
+        case 1:
+                test_client_verify_solicit(packet, len);
+                assert_se(write(test_fd[1], msg_advertise, sizeof(msg_advertise)) == sizeof(msg_advertise));
+                break;
+
+        case 2:
+                test_client_callback(client_ref, DHCP6_CLIENT_EVENT_TEST_ADVERTISED, NULL);
+                test_client_verify_request(packet, len);
+                assert_se(write(test_fd[1], msg_reply, sizeof(msg_reply)) == sizeof(msg_reply));
+                break;
+
+        case 3:
+                test_client_verify_solicit(packet, len);
+                assert_se(write(test_fd[1], msg_reply, sizeof(msg_reply)) == sizeof(msg_reply));
+                break;
+
+        default:
+                assert_not_reached();
+        }
+
+        test_client_sent_message_count++;
+        return len;
+}
+
+int dhcp6_network_bind_udp_socket(int ifindex, struct in6_addr *a) {
+        assert_se(ifindex == test_ifindex);
+        assert_se(a);
+        assert_se(in6_addr_equal(a, &local_address));
+
+        assert_se(socketpair(AF_UNIX, SOCK_STREAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) >= 0);
+        return TAKE_FD(test_fd[0]);
+}
+
+TEST(dhcp6_client) {
+        _cleanup_(sd_dhcp6_client_unrefp) sd_dhcp6_client *client = NULL;
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+
+        assert_se(sd_event_new(&e) >= 0);
+        assert_se(sd_event_add_time_relative(e, NULL, CLOCK_BOOTTIME,
+                                             2 * USEC_PER_SEC, 0,
+                                             NULL, INT_TO_PTR(-ETIMEDOUT)) >= 0);
+
+        assert_se(sd_dhcp6_client_new(&client) >= 0);
+        assert_se(sd_dhcp6_client_attach_event(client, e, 0) >= 0);
+        assert_se(sd_dhcp6_client_set_ifindex(client, test_ifindex) == 0);
+        assert_se(sd_dhcp6_client_set_local_address(client, &local_address) >= 0);
+        assert_se(sd_dhcp6_client_set_fqdn(client, "host.lab.intra") >= 0);
+        assert_se(sd_dhcp6_client_set_iaid(client, unaligned_read_be32((uint8_t[]) { IA_ID_BYTES })) >= 0);
+        dhcp6_client_set_test_mode(client, true);
+
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_DNS_SERVER) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_DOMAIN) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_NTP_SERVER) >= 0);
+        assert_se(sd_dhcp6_client_set_request_option(client, SD_DHCP6_OPTION_SNTP_SERVER) >= 0);
+
+        assert_se(sd_dhcp6_client_set_information_request(client, true) >= 0);
+        assert_se(sd_dhcp6_client_set_callback(client, test_client_callback, NULL) >= 0);
+
+        assert_se(sd_dhcp6_client_start(client) >= 0);
+
+        assert_se(dhcp6_client_set_transaction_id(client, ((const DHCP6Message*) msg_reply)->transaction_id) >= 0);
+
+        assert_se(client_ref = sd_dhcp6_client_ref(client));
+
+        assert_se(sd_event_loop(e) >= 0);
+
+        assert_se(test_client_sent_message_count == 4);
+
+        assert_se(!sd_dhcp6_client_unref(client_ref));
+        test_fd[1] = safe_close(test_fd[1]);
+}
+
+DEFINE_TEST_MAIN(LOG_DEBUG);
diff --git a/src/libsystemd-network/test-ipv4ll-manual.c b/src/libsystemd-network/test-ipv4ll-manual.c
new file mode 100644
index 0000000..5453ef9
--- /dev/null
+++ b/src/libsystemd-network/test-ipv4ll-manual.c
@@ -0,0 +1,116 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <net/if.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <linux/veth.h>
+
+#include "sd-event.h"
+#include "sd-ipv4ll.h"
+#include "sd-netlink.h"
+
+#include "alloc-util.h"
+#include "in-addr-util.h"
+#include "parse-util.h"
+#include "string-util.h"
+#include "tests.h"
+#include "util.h"
+
+static void ll_handler(sd_ipv4ll *ll, int event, void *userdata) {
+        assert_se(ll);
+
+        struct in_addr addr;
+        const char *pretty = sd_ipv4ll_get_address(ll, &addr) >= 0 ? IN4_ADDR_TO_STRING(&addr) : NULL;
+
+        switch (event) {
+        case SD_IPV4LL_EVENT_BIND:
+                log_info("bound %s", strna(pretty));
+                break;
+        case SD_IPV4LL_EVENT_CONFLICT:
+                log_info("conflict on %s", strna(pretty));
+                break;
+        case SD_IPV4LL_EVENT_STOP:
+                log_error("the client was stopped with address %s", strna(pretty));
+                break;
+        default:
+                assert_not_reached();
+        }
+}
+
+static int client_run(int ifindex, const char *seed_str, const struct in_addr *start_address, const struct ether_addr *ha, sd_event *e) {
+        sd_ipv4ll *ll;
+
+        assert_se(sd_ipv4ll_new(&ll) >= 0);
+        assert_se(sd_ipv4ll_attach_event(ll, e, 0) >= 0);
+
+        assert_se(sd_ipv4ll_set_ifindex(ll, ifindex) >= 0);
+        assert_se(sd_ipv4ll_set_mac(ll, ha) >= 0);
+        assert_se(sd_ipv4ll_set_callback(ll, ll_handler, NULL) >= 0);
+
+        if (seed_str) {
+                unsigned seed;
+
+                assert_se(safe_atou(seed_str, &seed) >= 0);
+
+                assert_se(sd_ipv4ll_set_address_seed(ll, seed) >= 0);
+        }
+
+        if (start_address && in4_addr_is_set(start_address))
+                assert_se(sd_ipv4ll_set_address(ll, start_address) >= 0);
+
+        log_info("starting IPv4LL client");
+
+        assert_se(sd_ipv4ll_start(ll) >= 0);
+
+        assert_se(sd_event_loop(e) >= 0);
+
+        assert_se(!sd_ipv4ll_unref(ll));
+
+        return EXIT_SUCCESS;
+}
+
+static int test_ll(const char *ifname, const char *seed, const struct in_addr *start_address) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL;
+        _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL, *reply = NULL;
+        struct ether_addr ha;
+        int ifindex;
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        assert_se(sd_netlink_open(&rtnl) >= 0);
+        assert_se(sd_netlink_attach_event(rtnl, e, 0) >= 0);
+
+        assert_se(sd_rtnl_message_new_link(rtnl, &m, RTM_GETLINK, 0) >= 0);
+        assert_se(sd_netlink_message_append_string(m, IFLA_IFNAME, ifname) >= 0);
+        assert_se(sd_netlink_call(rtnl, m, 0, &reply) >= 0);
+
+        assert_se(sd_rtnl_message_link_get_ifindex(reply, &ifindex) >= 0);
+        assert_se(sd_netlink_message_read_ether_addr(reply, IFLA_ADDRESS, &ha) >= 0);
+
+        client_run(ifindex, seed, start_address, &ha, e);
+
+        return EXIT_SUCCESS;
+}
+
+int main(int argc, char *argv[]) {
+        test_setup_logging(LOG_DEBUG);
+
+        if (argc == 2)
+                return test_ll(argv[1], NULL, NULL);
+        else if (argc == 3) {
+                int r;
+                union in_addr_union a;
+
+                r = in_addr_from_string(AF_INET, argv[2], &a);
+                if (r < 0)
+                        return test_ll(argv[1], argv[2], NULL);
+                else
+                        return test_ll(argv[1], NULL, &a.in);
+        } else {
+                log_error("This program takes one or two arguments.\n"
+                          "\t %s <ifname> [<seed>|<start_address>]", program_invocation_short_name);
+                return EXIT_FAILURE;
+        }
+}
diff --git a/src/libsystemd-network/test-ipv4ll.c b/src/libsystemd-network/test-ipv4ll.c
new file mode 100644
index 0000000..2a078a5
--- /dev/null
+++ b/src/libsystemd-network/test-ipv4ll.c
@@ -0,0 +1,207 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Axis Communications AB. All rights reserved.
+***/
+
+#include <errno.h>
+#include <netinet/if_ether.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "sd-ipv4ll.h"
+
+#include "arp-util.h"
+#include "fd-util.h"
+#include "socket-util.h"
+#include "tests.h"
+#include "util.h"
+
+static bool verbose = false;
+static bool extended = false;
+static int test_fd[2];
+
+static int basic_request_handler_bind = 0;
+static int basic_request_handler_stop = 0;
+static void* basic_request_handler_userdata = (void*) 0xCABCAB;
+
+static void basic_request_handler(sd_ipv4ll *ll, int event, void *userdata) {
+        assert_se(userdata == basic_request_handler_userdata);
+
+        switch (event) {
+                case SD_IPV4LL_EVENT_STOP:
+                        basic_request_handler_stop = 1;
+                        break;
+                case SD_IPV4LL_EVENT_BIND:
+                        basic_request_handler_bind = 1;
+                        break;
+                default:
+                        assert_se(0);
+                        break;
+        }
+}
+
+int arp_send_packet(
+                int fd,
+                int ifindex,
+                const struct in_addr *pa,
+                const struct ether_addr *ha,
+                bool announce) {
+
+        struct ether_arp ea = {};
+
+        assert_se(fd >= 0);
+        assert_se(ifindex > 0);
+        assert_se(pa);
+        assert_se(ha);
+
+        if (send(fd, &ea, sizeof(struct ether_arp), 0) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int arp_update_filter(int fd, const struct in_addr *a, const struct ether_addr *eth_mac) {
+        return 0;
+}
+
+int arp_network_bind_raw_socket(int ifindex, const struct in_addr *a, const struct ether_addr *eth_mac) {
+        if (socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
+                return -errno;
+
+        return test_fd[0];
+}
+
+static void test_public_api_setters(sd_event *e) {
+        struct in_addr address = {};
+        uint64_t seed = 0;
+        sd_ipv4ll *ll;
+        struct ether_addr mac_addr = {
+                .ether_addr_octet = {'A', 'B', 'C', '1', '2', '3'}};
+
+        if (verbose)
+                printf("* %s\n", __func__);
+
+        assert_se(sd_ipv4ll_new(&ll) == 0);
+        assert_se(ll);
+
+        assert_se(sd_ipv4ll_attach_event(NULL, NULL, 0) == -EINVAL);
+        assert_se(sd_ipv4ll_attach_event(ll, e, 0) == 0);
+        assert_se(sd_ipv4ll_attach_event(ll, e, 0) == -EBUSY);
+
+        assert_se(sd_ipv4ll_set_callback(NULL, NULL, NULL) == -EINVAL);
+        assert_se(sd_ipv4ll_set_callback(ll, NULL, NULL) == 0);
+
+        assert_se(sd_ipv4ll_set_address(ll, &address) == -EINVAL);
+        address.s_addr |= htobe32(169U << 24 | 254U << 16);
+        assert_se(sd_ipv4ll_set_address(ll, &address) == -EINVAL);
+        address.s_addr |= htobe32(0x00FF);
+        assert_se(sd_ipv4ll_set_address(ll, &address) == -EINVAL);
+        address.s_addr |= htobe32(0xF000);
+        assert_se(sd_ipv4ll_set_address(ll, &address) == 0);
+        address.s_addr |= htobe32(0x0F00);
+        assert_se(sd_ipv4ll_set_address(ll, &address) == -EINVAL);
+
+        assert_se(sd_ipv4ll_set_address_seed(NULL, seed) == -EINVAL);
+        assert_se(sd_ipv4ll_set_address_seed(ll, seed) == 0);
+
+        assert_se(sd_ipv4ll_set_mac(NULL, NULL) == -EINVAL);
+        assert_se(sd_ipv4ll_set_mac(ll, NULL) == -EINVAL);
+        assert_se(sd_ipv4ll_set_mac(ll, &mac_addr) == 0);
+
+        assert_se(sd_ipv4ll_set_ifindex(NULL, -1) == -EINVAL);
+        assert_se(sd_ipv4ll_set_ifindex(ll, -1) == -EINVAL);
+        assert_se(sd_ipv4ll_set_ifindex(ll, -99) == -EINVAL);
+        assert_se(sd_ipv4ll_set_ifindex(ll, 1) == 0);
+
+        assert_se(sd_ipv4ll_ref(ll) == ll);
+        assert_se(sd_ipv4ll_unref(ll) == NULL);
+
+        /* Cleanup */
+        assert_se(sd_ipv4ll_unref(ll) == NULL);
+}
+
+static void test_basic_request(sd_event *e, const struct in_addr *start_address) {
+
+        sd_ipv4ll *ll;
+        struct ether_arp arp;
+        struct ether_addr mac_addr = {
+                .ether_addr_octet = {'A', 'B', 'C', '1', '2', '3'}};
+
+        if (verbose)
+                printf("* %s\n", __func__);
+
+        assert_se(sd_ipv4ll_new(&ll) == 0);
+        if (in4_addr_is_set(start_address))
+                assert_se(sd_ipv4ll_set_address(ll, start_address) >= 0);
+        assert_se(sd_ipv4ll_start(ll) == -EINVAL);
+
+        assert_se(sd_ipv4ll_attach_event(ll, e, 0) == 0);
+        assert_se(sd_ipv4ll_start(ll) == -EINVAL);
+
+        assert_se(sd_ipv4ll_set_mac(ll, &mac_addr) == 0);
+        assert_se(sd_ipv4ll_start(ll) == -EINVAL);
+
+        assert_se(sd_ipv4ll_set_callback(ll, basic_request_handler,
+                                         basic_request_handler_userdata) == 0);
+        assert_se(sd_ipv4ll_start(ll) == -EINVAL);
+
+        assert_se(sd_ipv4ll_set_ifindex(ll, 1) == 0);
+        assert_se(sd_ipv4ll_start(ll) == 1);
+
+        sd_event_run(e, UINT64_MAX);
+        assert_se(sd_ipv4ll_start(ll) == 0);
+
+        assert_se(sd_ipv4ll_is_running(ll));
+
+        /* PROBE */
+        sd_event_run(e, UINT64_MAX);
+        assert_se(recv(test_fd[1], &arp, sizeof(struct ether_arp), 0) == sizeof(struct ether_arp));
+
+        if (extended) {
+                /* PROBE */
+                sd_event_run(e, UINT64_MAX);
+                assert_se(recv(test_fd[1], &arp, sizeof(struct ether_arp), 0) == sizeof(struct ether_arp));
+
+                /* PROBE */
+                sd_event_run(e, UINT64_MAX);
+                assert_se(recv(test_fd[1], &arp, sizeof(struct ether_arp), 0) == sizeof(struct ether_arp));
+
+                sd_event_run(e, UINT64_MAX);
+                assert_se(basic_request_handler_bind == 1);
+
+                if (in4_addr_is_set(start_address)) {
+                        struct in_addr address;
+
+                        assert_se(sd_ipv4ll_get_address(ll, &address) >= 0);
+                        assert_se(start_address->s_addr == address.s_addr);
+                }
+        }
+
+        sd_ipv4ll_stop(ll);
+        assert_se(basic_request_handler_stop == 1);
+
+        /* Cleanup */
+        assert_se(sd_ipv4ll_unref(ll) == NULL);
+        safe_close(test_fd[1]);
+}
+
+int main(int argc, char *argv[]) {
+        struct in_addr start_address = {};
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+
+        test_setup_logging(LOG_DEBUG);
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        test_public_api_setters(e);
+        test_basic_request(e, &start_address);
+
+        basic_request_handler_bind = 0;
+        basic_request_handler_stop = 0;
+        start_address.s_addr = htobe32(169U << 24 | 254U << 16 | 1U << 8 | 2U);
+        test_basic_request(e, &start_address);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/test-lldp-rx.c b/src/libsystemd-network/test-lldp-rx.c
new file mode 100644
index 0000000..11049a8
--- /dev/null
+++ b/src/libsystemd-network/test-lldp-rx.c
@@ -0,0 +1,378 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <net/ethernet.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "sd-event.h"
+#include "sd-lldp-rx.h"
+
+#include "alloc-util.h"
+#include "fd-util.h"
+#include "lldp-network.h"
+#include "macro.h"
+#include "string-util.h"
+#include "tests.h"
+
+#define TEST_LLDP_PORT "em1"
+#define TEST_LLDP_TYPE_SYSTEM_NAME "systemd-lldp"
+#define TEST_LLDP_TYPE_SYSTEM_DESC "systemd-lldp-desc"
+
+static int test_fd[2] = { -1, -1 };
+static int lldp_rx_handler_calls;
+
+int lldp_network_bind_raw_socket(int ifindex) {
+        if (socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
+                return -errno;
+
+        return test_fd[0];
+}
+
+static void lldp_rx_handler(sd_lldp_rx *lldp_rx, sd_lldp_rx_event_t event, sd_lldp_neighbor *n, void *userdata) {
+        lldp_rx_handler_calls++;
+}
+
+static int start_lldp_rx(sd_lldp_rx **lldp_rx, sd_event *e, sd_lldp_rx_callback_t cb, void *cb_data) {
+        int r;
+
+        r = sd_lldp_rx_new(lldp_rx);
+        if (r < 0)
+                return r;
+
+        r = sd_lldp_rx_set_ifindex(*lldp_rx, 42);
+        if (r < 0)
+                return r;
+
+        r = sd_lldp_rx_set_callback(*lldp_rx, cb, cb_data);
+        if (r < 0)
+                return r;
+
+        r = sd_lldp_rx_attach_event(*lldp_rx, e, 0);
+        if (r < 0)
+                return r;
+
+        r = sd_lldp_rx_start(*lldp_rx);
+        if (r < 0)
+                return r;
+
+        return 0;
+}
+
+static int stop_lldp_rx(sd_lldp_rx *lldp_rx) {
+        int r;
+
+        r = sd_lldp_rx_stop(lldp_rx);
+        if (r < 0)
+                return r;
+
+        r = sd_lldp_rx_detach_event(lldp_rx);
+        if (r < 0)
+                return r;
+
+        sd_lldp_rx_unref(lldp_rx);
+        safe_close(test_fd[1]);
+
+        return 0;
+}
+
+static void test_receive_basic_packet(sd_event *e) {
+
+        static const uint8_t frame[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x07, 0x04, 0x00, 0x01, 0x02,     /* Chassis: MAC, 00:01:02:03:04:05 */
+                0x03, 0x04, 0x05,
+                0x04, 0x04, 0x05, 0x31, 0x2f, 0x33,     /* Port: interface name, "1/3" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                /* LLDP optional TLVs */
+                0x08, 0x04, 0x50, 0x6f, 0x72, 0x74,     /* Port Description: "Port" */
+                0x0a, 0x03, 0x53, 0x59, 0x53,           /* System Name: "SYS" */
+                0x0c, 0x04, 0x66, 0x6f, 0x6f, 0x00,     /* System Description: "foo" (NULL-terminated) */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+
+        sd_lldp_rx *lldp_rx;
+        sd_lldp_neighbor **neighbors;
+        uint8_t type;
+        const void *data;
+        uint16_t ttl;
+        size_t length;
+        const char *str;
+
+        lldp_rx_handler_calls = 0;
+        assert_se(start_lldp_rx(&lldp_rx, e, lldp_rx_handler, NULL) == 0);
+
+        assert_se(write(test_fd[1], frame, sizeof(frame)) == sizeof(frame));
+        sd_event_run(e, 0);
+        assert_se(lldp_rx_handler_calls == 1);
+        assert_se(sd_lldp_rx_get_neighbors(lldp_rx, &neighbors) == 1);
+
+        assert_se(sd_lldp_neighbor_get_chassis_id(neighbors[0], &type, &data, &length) == 0);
+        assert_se(type == SD_LLDP_CHASSIS_SUBTYPE_MAC_ADDRESS);
+        assert_se(length == ETH_ALEN);
+        assert_se(!memcmp(data, "\x00\x01\x02\x03\x04\x05", ETH_ALEN));
+
+        assert_se(sd_lldp_neighbor_get_port_id(neighbors[0], &type, &data, &length) == 0);
+        assert_se(type == SD_LLDP_PORT_SUBTYPE_INTERFACE_NAME);
+        assert_se(length == 3);
+        assert_se(!memcmp(data, "1/3", 3));
+
+        assert_se(sd_lldp_neighbor_get_port_description(neighbors[0], &str) == 0);
+        assert_se(streq(str, "Port"));
+
+        assert_se(sd_lldp_neighbor_get_system_name(neighbors[0], &str) == 0);
+        assert_se(streq(str, "SYS"));
+
+        assert_se(sd_lldp_neighbor_get_system_description(neighbors[0], &str) == 0);
+        assert_se(streq(str, "foo"));
+
+        assert_se(sd_lldp_neighbor_get_ttl(neighbors[0], &ttl) == 0);
+        assert_se(ttl == 120);
+
+        sd_lldp_neighbor_unref(neighbors[0]);
+        free(neighbors);
+
+        assert_se(stop_lldp_rx(lldp_rx) == 0);
+}
+
+static void test_receive_incomplete_packet(sd_event *e) {
+        sd_lldp_rx *lldp_rx;
+        sd_lldp_neighbor **neighbors;
+        uint8_t frame[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x07, 0x04, 0x00, 0x01, 0x02,     /* Chassis: MAC, 00:01:02:03:04:05 */
+                0x03, 0x04, 0x05,
+                0x04, 0x04, 0x05, 0x31, 0x2f, 0x33,     /* Port: interface name, "1/3" */
+                                                        /* Missing TTL */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+
+        lldp_rx_handler_calls = 0;
+        assert_se(start_lldp_rx(&lldp_rx, e, lldp_rx_handler, NULL) == 0);
+
+        assert_se(write(test_fd[1], frame, sizeof(frame)) == sizeof(frame));
+        sd_event_run(e, 0);
+        assert_se(lldp_rx_handler_calls == 0);
+        assert_se(sd_lldp_rx_get_neighbors(lldp_rx, &neighbors) == 0);
+
+        assert_se(stop_lldp_rx(lldp_rx) == 0);
+}
+
+static void test_receive_oui_packet(sd_event *e) {
+        sd_lldp_rx *lldp_rx;
+        sd_lldp_neighbor **neighbors;
+        uint8_t frame[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x07, 0x04, 0x00, 0x01, 0x02,     /* Chassis: MAC, 00:01:02:03:04:05 */
+                0x03, 0x04, 0x05,
+                0x04, 0x04, 0x05, 0x31, 0x2f, 0x33,     /* Port TLV: interface name, "1/3" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                /* LLDP optional TLVs */
+                0xfe, 0x06, 0x00, 0x80, 0xc2, 0x01,     /* Port VLAN ID: 0x1234 */
+                0x12, 0x34,
+                0xfe, 0x07, 0x00, 0x80, 0xc2, 0x02,     /* Port and protocol: flag 1, PPVID 0x7788 */
+                0x01, 0x77, 0x88,
+                0xfe, 0x0d, 0x00, 0x80, 0xc2, 0x03,     /* VLAN Name: ID 0x1234, name "Vlan51" */
+                0x12, 0x34, 0x06, 0x56, 0x6c, 0x61,
+                0x6e, 0x35, 0x31,
+                0xfe, 0x06, 0x00, 0x80, 0xc2, 0x06,     /* Management VID: 0x0102 */
+                0x01, 0x02,
+                0xfe, 0x09, 0x00, 0x80, 0xc2, 0x07,     /* Link aggregation: status 1, ID 0x00140012 */
+                0x01, 0x00, 0x14, 0x00, 0x12,
+                0xfe, 0x07, 0x00, 0x12, 0x0f, 0x02,     /* 802.3 Power via MDI: PSE, MDI enabled */
+                0x07, 0x01, 0x00,
+                0x00, 0x00                              /* End of LLDPDU */
+        };
+
+        lldp_rx_handler_calls = 0;
+        assert_se(start_lldp_rx(&lldp_rx, e, lldp_rx_handler, NULL) == 0);
+
+        assert_se(write(test_fd[1], frame, sizeof(frame)) == sizeof(frame));
+        sd_event_run(e, 0);
+        assert_se(lldp_rx_handler_calls == 1);
+        assert_se(sd_lldp_rx_get_neighbors(lldp_rx, &neighbors) == 1);
+
+        assert_se(sd_lldp_neighbor_tlv_rewind(neighbors[0]) >= 0);
+        assert_se(sd_lldp_neighbor_tlv_is_type(neighbors[0], SD_LLDP_TYPE_CHASSIS_ID) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_type(neighbors[0], SD_LLDP_TYPE_PORT_ID) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_type(neighbors[0], SD_LLDP_TYPE_TTL) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_oui(neighbors[0], SD_LLDP_OUI_802_1, SD_LLDP_OUI_802_1_SUBTYPE_PORT_VLAN_ID) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_oui(neighbors[0], SD_LLDP_OUI_802_1, SD_LLDP_OUI_802_1_SUBTYPE_PORT_PROTOCOL_VLAN_ID) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_oui(neighbors[0], SD_LLDP_OUI_802_1, SD_LLDP_OUI_802_1_SUBTYPE_VLAN_NAME) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_oui(neighbors[0], SD_LLDP_OUI_802_1, SD_LLDP_OUI_802_1_SUBTYPE_MANAGEMENT_VID) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_oui(neighbors[0], SD_LLDP_OUI_802_1, SD_LLDP_OUI_802_1_SUBTYPE_LINK_AGGREGATION) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_oui(neighbors[0], SD_LLDP_OUI_802_3, SD_LLDP_OUI_802_3_SUBTYPE_POWER_VIA_MDI) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) > 0);
+        assert_se(sd_lldp_neighbor_tlv_is_type(neighbors[0], SD_LLDP_TYPE_END) > 0);
+        assert_se(sd_lldp_neighbor_tlv_next(neighbors[0]) == 0);
+
+        sd_lldp_neighbor_unref(neighbors[0]);
+        free(neighbors);
+
+        assert_se(stop_lldp_rx(lldp_rx) == 0);
+}
+
+static void test_multiple_neighbors_sorted(sd_event *e) {
+
+        static const uint8_t frame1[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x04, 0x01, '1', '/', '2',        /* Chassis component: "1/2" */
+                0x04, 0x04, 0x02, '2', '/', '3',        /* Port component: "2/3" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+        static const uint8_t frame2[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x04, 0x01, '2', '/', '1',        /* Chassis component: "2/1" */
+                0x04, 0x04, 0x02, '1', '/', '3',        /* Port component: "1/3" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+        static const uint8_t frame3[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x05, 0x01, '2', '/', '1', '0',   /* Chassis component: "2/10" */
+                0x04, 0x04, 0x02, '1', '/', '0',        /* Port component: "1/0" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+        static const uint8_t frame4[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x05, 0x01, '2', '/', '1', '9',   /* Chassis component: "2/19" */
+                0x04, 0x04, 0x02, '1', '/', '0',        /* Port component: "1/0" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+        static const uint8_t frame5[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x04, 0x01, '1', '/', '2',        /* Chassis component: "1/2" */
+                0x04, 0x05, 0x02, '2', '/', '1', '0',   /* Port component: "2/10" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+        static const uint8_t frame6[] = {
+                /* Ethernet header */
+                0x01, 0x80, 0xc2, 0x00, 0x00, 0x03,     /* Destination MAC */
+                0x01, 0x02, 0x03, 0x04, 0x05, 0x06,     /* Source MAC */
+                0x88, 0xcc,                             /* Ethertype */
+                /* LLDP mandatory TLVs */
+                0x02, 0x04, 0x01, '1', '/', '2',        /* Chassis component: "1/2" */
+                0x04, 0x05, 0x02, '2', '/', '3', '9',   /* Port component: "2/10" */
+                0x06, 0x02, 0x00, 0x78,                 /* TTL: 120 seconds */
+                0x00, 0x00                              /* End Of LLDPDU */
+        };
+        static const char* expected[] = {
+                /* ordered pairs of Chassis+Port */
+                "1/2", "2/10",
+                "1/2", "2/3",
+                "1/2", "2/39",
+                "2/1", "1/3",
+                "2/10", "1/0",
+                "2/19", "1/0",
+        };
+
+        sd_lldp_rx *lldp_rx;
+        sd_lldp_neighbor **neighbors;
+        int i;
+        uint8_t type;
+        const void *data;
+        size_t length, expected_length;
+        uint16_t ttl;
+
+        lldp_rx_handler_calls = 0;
+        assert_se(start_lldp_rx(&lldp_rx, e, lldp_rx_handler, NULL) == 0);
+
+        assert_se(write(test_fd[1], frame1, sizeof(frame1)) == sizeof(frame1));
+        sd_event_run(e, 0);
+        assert_se(write(test_fd[1], frame2, sizeof(frame2)) == sizeof(frame2));
+        sd_event_run(e, 0);
+        assert_se(write(test_fd[1], frame3, sizeof(frame3)) == sizeof(frame3));
+        sd_event_run(e, 0);
+        assert_se(write(test_fd[1], frame4, sizeof(frame4)) == sizeof(frame4));
+        sd_event_run(e, 0);
+        assert_se(write(test_fd[1], frame5, sizeof(frame5)) == sizeof(frame5));
+        sd_event_run(e, 0);
+        assert_se(write(test_fd[1], frame6, sizeof(frame6)) == sizeof(frame6));
+        sd_event_run(e, 0);
+        assert_se(lldp_rx_handler_calls == 6);
+
+        assert_se(sd_lldp_rx_get_neighbors(lldp_rx, &neighbors) == 6);
+
+        for (i = 0; i < 6; i++) {
+                assert_se(sd_lldp_neighbor_get_chassis_id(neighbors[i], &type, &data, &length) == 0);
+                assert_se(type == SD_LLDP_CHASSIS_SUBTYPE_CHASSIS_COMPONENT);
+                expected_length = strlen(expected[2 * i]);
+                assert_se(length == expected_length);
+                assert_se(memcmp(data, expected[2 * i], expected_length) == 0);
+
+                assert_se(sd_lldp_neighbor_get_port_id(neighbors[i], &type, &data, &length) == 0);
+                assert_se(type == SD_LLDP_PORT_SUBTYPE_PORT_COMPONENT);
+                expected_length = strlen(expected[2 * i + 1]);
+                assert_se(length == expected_length);
+                assert_se(memcmp(data, expected[2 * i + 1], expected_length) == 0);
+
+                assert_se(sd_lldp_neighbor_get_ttl(neighbors[i], &ttl) == 0);
+                assert_se(ttl == 120);
+        }
+
+        for (i = 0; i < 6; i++)
+                sd_lldp_neighbor_unref(neighbors[i]);
+        free(neighbors);
+
+        assert_se(stop_lldp_rx(lldp_rx) == 0);
+}
+
+int main(int argc, char *argv[]) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+
+        test_setup_logging(LOG_DEBUG);
+
+        /* LLDP reception tests */
+        assert_se(sd_event_new(&e) == 0);
+        test_receive_basic_packet(e);
+        test_receive_incomplete_packet(e);
+        test_receive_oui_packet(e);
+        test_multiple_neighbors_sorted(e);
+
+        return 0;
+}
diff --git a/src/libsystemd-network/test-ndisc-ra.c b/src/libsystemd-network/test-ndisc-ra.c
new file mode 100644
index 0000000..d3d96e7
--- /dev/null
+++ b/src/libsystemd-network/test-ndisc-ra.c
@@ -0,0 +1,343 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2017 Intel Corporation. All rights reserved.
+***/
+
+#include <netinet/icmp6.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+
+#include "sd-radv.h"
+
+#include "alloc-util.h"
+#include "hexdecoct.h"
+#include "icmp6-util.h"
+#include "socket-util.h"
+#include "strv.h"
+#include "tests.h"
+
+static struct ether_addr mac_addr = {
+        .ether_addr_octet = { 0x78, 0x2b, 0xcb, 0xb3, 0x6d, 0x53 }
+};
+
+static uint8_t advertisement[] = {
+        /* ICMPv6 Router Advertisement, no checksum */
+        0x86, 0x00, 0x00, 0x00,  0x40, 0xc0, 0x00, 0xb4,
+        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
+        /* Source Link Layer Address Option */
+        0x01, 0x01, 0x78, 0x2b,  0xcb, 0xb3, 0x6d, 0x53,
+        /* Prefix Information Option */
+        0x03, 0x04, 0x40, 0xc0,  0x00, 0x00, 0x01, 0xf4,
+        0x00, 0x00, 0x01, 0xb8,  0x00, 0x00, 0x00, 0x00,
+        0x20, 0x01, 0x0d, 0xb8,  0xde, 0xad, 0xbe, 0xef,
+        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
+        /* Prefix Information Option */
+        0x03, 0x04, 0x40, 0xc0,  0x00, 0x00, 0x0e, 0x10,
+        0x00, 0x00, 0x07, 0x08,  0x00, 0x00, 0x00, 0x00,
+        0x20, 0x01, 0x0d, 0xb8,  0x0b, 0x16, 0xd0, 0x0d,
+        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
+        /* Prefix Information Option */
+        0x03, 0x04, 0x30, 0xc0,  0x00, 0x00, 0x0e, 0x10,
+        0x00, 0x00, 0x07, 0x08,  0x00, 0x00, 0x00, 0x00,
+        0x20, 0x01, 0x0d, 0xb8,  0xc0, 0x01, 0x0d, 0xad,
+        0x00, 0x00, 0x00, 0x00,  0x00, 0x00, 0x00, 0x00,
+        /* Recursive DNS Server Option */
+        0x19, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
+        0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
+        /* DNS Search List Option */
+        0x1f, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
+        0x03, 0x6c, 0x61, 0x62, 0x05, 0x69, 0x6e, 0x74,
+        0x72, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+};
+
+static bool test_stopped;
+static int test_fd[2];
+static struct {
+        struct in6_addr address;
+        unsigned char prefixlen;
+        uint32_t valid;
+        uint32_t preferred;
+        bool successful;
+} prefix[] = {
+        { { { { 0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } } }, 64,
+          500, 440, true },
+        { { { { 0x20, 0x01, 0x0d, 0xb8, 0x0b, 0x16, 0xd0, 0x0d,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } } }, 64,
+          /* indicate default valid and preferred lifetimes for the test code */
+          0, 0, true },
+        { { { { 0x20, 0x01, 0x0d, 0xb8, 0x0b, 0x16, 0xd0, 0x0d,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } } }, 58,
+          0, 0,
+          /* indicate that this prefix already exists */
+          false },
+        { { { { 0x20, 0x01, 0x0d, 0xb8, 0x0b, 0x16, 0xd0, 0x0d,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } } }, 120,
+          0, 0,
+          /* indicate that this prefix already exists */
+          false },
+        { { { { 0x20, 0x01, 0x0d, 0xb8, 0x0b, 0x16, 0xd0, 0x0d,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } } }, 12,
+          0, 0,
+          /* indicate that this prefix already exists */
+          false },
+        { { { { 0x20, 0x01, 0x0d, 0xb8, 0xc0, 0x01, 0x0d, 0xad,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } } }, 48,
+          0, 0, true },
+        { { { { 0x20, 0x01, 0x0d, 0xb8, 0xc0, 0x01, 0x0d, 0xad,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } } }, 60,
+          0, 0,
+          /* indicate that this prefix already exists */
+          false },
+};
+
+static const struct in6_addr test_rdnss = { { { 0x20, 0x01, 0x0d, 0xb8,
+                                                0xde, 0xad, 0xbe, 0xef,
+                                                0x00, 0x00, 0x00, 0x00,
+                                                0x00, 0x00, 0x00, 0x01 } } };
+static const char *test_dnssl[] = { "lab.intra",
+                                    NULL };
+
+TEST(radv_prefix) {
+        sd_radv_prefix *p;
+
+        assert_se(sd_radv_prefix_new(&p) >= 0);
+
+        assert_se(sd_radv_prefix_set_onlink(NULL, true) < 0);
+        assert_se(sd_radv_prefix_set_onlink(p, true) >= 0);
+        assert_se(sd_radv_prefix_set_onlink(p, false) >= 0);
+
+        assert_se(sd_radv_prefix_set_address_autoconfiguration(NULL, true) < 0);
+        assert_se(sd_radv_prefix_set_address_autoconfiguration(p, true) >= 0);
+        assert_se(sd_radv_prefix_set_address_autoconfiguration(p, false) >= 0);
+
+        assert_se(sd_radv_prefix_set_valid_lifetime(NULL, 1, 1) < 0);
+        assert_se(sd_radv_prefix_set_valid_lifetime(p, 0, 0) >= 0);
+        assert_se(sd_radv_prefix_set_valid_lifetime(p, 300 * USEC_PER_SEC, USEC_INFINITY) >= 0);
+        assert_se(sd_radv_prefix_set_valid_lifetime(p, 300 * USEC_PER_SEC, USEC_PER_YEAR) >= 0);
+
+        assert_se(sd_radv_prefix_set_preferred_lifetime(NULL, 1, 1) < 0);
+        assert_se(sd_radv_prefix_set_preferred_lifetime(p, 0, 0) >= 0);
+        assert_se(sd_radv_prefix_set_preferred_lifetime(p, 300 * USEC_PER_SEC, USEC_INFINITY) >= 0);
+        assert_se(sd_radv_prefix_set_preferred_lifetime(p, 300 * USEC_PER_SEC, USEC_PER_YEAR) >= 0);
+
+        assert_se(sd_radv_prefix_set_prefix(NULL, NULL, 0) < 0);
+        assert_se(sd_radv_prefix_set_prefix(p, NULL, 0) < 0);
+
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 64) >= 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 0) < 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 1) < 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 2) < 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 3) >= 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 125) >= 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 128) >= 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 129) < 0);
+        assert_se(sd_radv_prefix_set_prefix(p, &prefix[0].address, 255) < 0);
+
+        p = sd_radv_prefix_unref(p);
+        assert_se(!p);
+}
+
+TEST(radv) {
+        sd_radv *ra;
+
+        assert_se(sd_radv_new(&ra) >= 0);
+        assert_se(ra);
+
+        assert_se(sd_radv_set_ifindex(NULL, 0) < 0);
+        assert_se(sd_radv_set_ifindex(ra, 0) < 0);
+        assert_se(sd_radv_set_ifindex(ra, -1) < 0);
+        assert_se(sd_radv_set_ifindex(ra, -2) < 0);
+        assert_se(sd_radv_set_ifindex(ra, 42) >= 0);
+
+        assert_se(sd_radv_set_mac(NULL, NULL) < 0);
+        assert_se(sd_radv_set_mac(ra, NULL) >= 0);
+        assert_se(sd_radv_set_mac(ra, &mac_addr) >= 0);
+
+        assert_se(sd_radv_set_mtu(NULL, 0) < 0);
+        assert_se(sd_radv_set_mtu(ra, 0) < 0);
+        assert_se(sd_radv_set_mtu(ra, 1279) < 0);
+        assert_se(sd_radv_set_mtu(ra, 1280) >= 0);
+        assert_se(sd_radv_set_mtu(ra, ~0) >= 0);
+
+        assert_se(sd_radv_set_hop_limit(NULL, 0) < 0);
+        assert_se(sd_radv_set_hop_limit(ra, 0) >= 0);
+        assert_se(sd_radv_set_hop_limit(ra, ~0) >= 0);
+
+        assert_se(sd_radv_set_router_lifetime(NULL, 0) < 0);
+        assert_se(sd_radv_set_router_lifetime(ra, 0) >= 0);
+        assert_se(sd_radv_set_router_lifetime(ra, USEC_INFINITY) < 0);
+        assert_se(sd_radv_set_router_lifetime(ra, USEC_PER_YEAR) < 0);
+        assert_se(sd_radv_set_router_lifetime(ra, 300 * USEC_PER_SEC) >= 0);
+
+        assert_se(sd_radv_set_preference(NULL, 0) < 0);
+        assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_LOW) >= 0);
+        assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_MEDIUM) >= 0);
+        assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_HIGH) >= 0);
+        assert_se(sd_radv_set_preference(ra, ~0) < 0);
+
+        assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_HIGH) >= 0);
+        assert_se(sd_radv_set_router_lifetime(ra, 300 * USEC_PER_SEC) >= 0);
+        assert_se(sd_radv_set_router_lifetime(ra, 0) < 0);
+        assert_se(sd_radv_set_preference(ra, SD_NDISC_PREFERENCE_MEDIUM) >= 0);
+        assert_se(sd_radv_set_router_lifetime(ra, 0) >= 0);
+
+        assert_se(sd_radv_set_managed_information(NULL, true) < 0);
+        assert_se(sd_radv_set_managed_information(ra, true) >= 0);
+        assert_se(sd_radv_set_managed_information(ra, false) >= 0);
+
+        assert_se(sd_radv_set_other_information(NULL, true) < 0);
+        assert_se(sd_radv_set_other_information(ra, true) >= 0);
+        assert_se(sd_radv_set_other_information(ra, false) >= 0);
+
+        assert_se(sd_radv_set_rdnss(NULL, 0, NULL, 0) < 0);
+        assert_se(sd_radv_set_rdnss(ra, 0, NULL, 0) >= 0);
+        assert_se(sd_radv_set_rdnss(ra, 0, NULL, 128) < 0);
+        assert_se(sd_radv_set_rdnss(ra, 600, &test_rdnss, 0) >= 0);
+        assert_se(sd_radv_set_rdnss(ra, 600, &test_rdnss, 1) >= 0);
+        assert_se(sd_radv_set_rdnss(ra, 0, &test_rdnss, 1) >= 0);
+        assert_se(sd_radv_set_rdnss(ra, 0, NULL, 0) >= 0);
+
+        assert_se(sd_radv_set_dnssl(ra, 0, NULL) >= 0);
+        assert_se(sd_radv_set_dnssl(ra, 600, NULL) >= 0);
+        assert_se(sd_radv_set_dnssl(ra, 0, (char **)test_dnssl) >= 0);
+        assert_se(sd_radv_set_dnssl(ra, 600, (char **)test_dnssl) >= 0);
+
+        ra = sd_radv_unref(ra);
+        assert_se(!ra);
+}
+
+int icmp6_bind_router_solicitation(int ifindex) {
+        return -ENOSYS;
+}
+
+int icmp6_bind_router_advertisement(int ifindex) {
+        assert_se(ifindex == 42);
+
+        return test_fd[1];
+}
+
+int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr) {
+
+        return 0;
+}
+
+int icmp6_receive(
+                int fd,
+                void *iov_base,
+                size_t iov_len,
+                struct in6_addr *ret_sender,
+                triple_timestamp *ret_timestamp) {
+
+        assert_se(read (fd, iov_base, iov_len) == (ssize_t)iov_len);
+
+        if (ret_timestamp)
+                triple_timestamp_get(ret_timestamp);
+
+        return 0;
+}
+
+static int radv_recv(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
+        sd_radv *ra = userdata;
+        unsigned char buf[168];
+        size_t i;
+
+        assert_se(read(test_fd[0], &buf, sizeof(buf)) == sizeof(buf));
+
+        /* router lifetime must be zero when test is stopped */
+        if (test_stopped) {
+                advertisement[6] = 0x00;
+                advertisement[7] = 0x00;
+        }
+
+        printf ("Received Router Advertisement with lifetime %i\n",
+                (advertisement[6] << 8) + advertisement[7]);
+
+        /* test only up to buf size, rest is not yet implemented */
+        for (i = 0; i < sizeof(buf); i++) {
+                if (!(i % 8))
+                        printf("%3zu: ", i);
+
+                printf("0x%02x", buf[i]);
+
+                assert_se(buf[i] == advertisement[i]);
+
+                if ((i + 1) % 8)
+                        printf(", ");
+                else
+                        printf("\n");
+        }
+
+        if (test_stopped) {
+                sd_event *e;
+
+                e = sd_radv_get_event(ra);
+                sd_event_exit(e, 0);
+
+                return 0;
+        }
+
+        assert_se(sd_radv_stop(ra) >= 0);
+        test_stopped = true;
+
+        return 0;
+}
+
+TEST(ra) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_event_source_unrefp) sd_event_source *recv_router_advertisement = NULL;
+        _cleanup_(sd_radv_unrefp) sd_radv *ra = NULL;
+
+        assert_se(socketpair(AF_UNIX, SOCK_SEQPACKET | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) >= 0);
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        assert_se(sd_radv_new(&ra) >= 0);
+        assert_se(ra);
+
+        assert_se(sd_radv_attach_event(ra, e, 0) >= 0);
+
+        assert_se(sd_radv_set_ifindex(ra, 42) >= 0);
+        assert_se(sd_radv_set_mac(ra, &mac_addr) >= 0);
+        assert_se(sd_radv_set_router_lifetime(ra, 180 * USEC_PER_SEC) >= 0);
+        assert_se(sd_radv_set_hop_limit(ra, 64) >= 0);
+        assert_se(sd_radv_set_managed_information(ra, true) >= 0);
+        assert_se(sd_radv_set_other_information(ra, true) >= 0);
+        assert_se(sd_radv_set_rdnss(ra, 60, &test_rdnss, 1) >= 0);
+        assert_se(sd_radv_set_dnssl(ra, 60, (char **)test_dnssl) >= 0);
+
+        for (unsigned i = 0; i < ELEMENTSOF(prefix); i++) {
+                sd_radv_prefix *p;
+
+                printf("Test prefix %u\n", i);
+                assert_se(sd_radv_prefix_new(&p) >= 0);
+
+                assert_se(sd_radv_prefix_set_prefix(p, &prefix[i].address,
+                                                    prefix[i].prefixlen) >= 0);
+                if (prefix[i].valid > 0)
+                        assert_se(sd_radv_prefix_set_valid_lifetime(p, prefix[i].valid * USEC_PER_SEC, USEC_INFINITY) >= 0);
+                if (prefix[i].preferred > 0)
+                        assert_se(sd_radv_prefix_set_preferred_lifetime(p, prefix[i].preferred * USEC_PER_SEC, USEC_INFINITY) >= 0);
+
+                assert_se((sd_radv_add_prefix(ra, p) >= 0) == prefix[i].successful);
+                /* If the previous sd_radv_add_prefix() succeeds, then also the second call should also succeed. */
+                assert_se((sd_radv_add_prefix(ra, p) >= 0) == prefix[i].successful);
+
+                p = sd_radv_prefix_unref(p);
+                assert_se(!p);
+        }
+
+        assert_se(sd_event_add_io(e, &recv_router_advertisement, test_fd[0], EPOLLIN, radv_recv, ra) >= 0);
+        assert_se(sd_event_source_set_io_fd_own(recv_router_advertisement, true) >= 0);
+
+        assert_se(sd_event_add_time_relative(e, NULL, CLOCK_BOOTTIME,
+                                             2 * USEC_PER_SEC, 0,
+                                             NULL, INT_TO_PTR(-ETIMEDOUT)) >= 0);
+
+        assert_se(sd_radv_start(ra) >= 0);
+
+        assert_se(sd_event_loop(e) >= 0);
+}
+
+DEFINE_TEST_MAIN(LOG_DEBUG);
diff --git a/src/libsystemd-network/test-ndisc-rs.c b/src/libsystemd-network/test-ndisc-rs.c
new file mode 100644
index 0000000..baa9cb2
--- /dev/null
+++ b/src/libsystemd-network/test-ndisc-rs.c
@@ -0,0 +1,386 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/***
+  Copyright © 2014 Intel Corporation. All rights reserved.
+***/
+
+#include <netinet/icmp6.h>
+#include <arpa/inet.h>
+#include <unistd.h>
+
+#include "sd-ndisc.h"
+
+#include "alloc-util.h"
+#include "fd-util.h"
+#include "hexdecoct.h"
+#include "icmp6-util.h"
+#include "socket-util.h"
+#include "strv.h"
+#include "ndisc-internal.h"
+#include "tests.h"
+
+static struct ether_addr mac_addr = {
+        .ether_addr_octet = {'A', 'B', 'C', '1', '2', '3'}
+};
+
+static bool verbose = false;
+static int test_fd[2];
+static sd_ndisc *test_timeout_nd;
+
+typedef int (*send_ra_t)(uint8_t flags);
+static send_ra_t send_ra_function;
+
+static void router_dump(sd_ndisc_router *rt) {
+        struct in6_addr addr;
+        uint8_t hop_limit;
+        uint64_t t, flags;
+        uint32_t mtu;
+        uint16_t lifetime;
+        unsigned preference;
+        int r;
+
+        assert_se(rt);
+
+        log_info("--");
+        assert_se(sd_ndisc_router_get_address(rt, &addr) >= 0);
+        log_info("Sender: %s", IN6_ADDR_TO_STRING(&addr));
+
+        assert_se(sd_ndisc_router_get_timestamp(rt, CLOCK_REALTIME, &t) >= 0);
+        log_info("Timestamp: %s", FORMAT_TIMESTAMP(t));
+
+        assert_se(sd_ndisc_router_get_timestamp(rt, CLOCK_MONOTONIC, &t) >= 0);
+        log_info("Monotonic: %" PRIu64, t);
+
+        if (sd_ndisc_router_get_hop_limit(rt, &hop_limit) < 0)
+                log_info("No hop limit set");
+        else
+                log_info("Hop limit: %u", hop_limit);
+
+        assert_se(sd_ndisc_router_get_flags(rt, &flags) >= 0);
+        log_info("Flags: <%s|%s>",
+                 flags & ND_RA_FLAG_OTHER ? "OTHER" : "",
+                 flags & ND_RA_FLAG_MANAGED ? "MANAGED" : "");
+
+        assert_se(sd_ndisc_router_get_preference(rt, &preference) >= 0);
+        log_info("Preference: %s",
+                 preference == SD_NDISC_PREFERENCE_LOW ? "low" :
+                 preference == SD_NDISC_PREFERENCE_HIGH ? "high" : "medium");
+
+        assert_se(sd_ndisc_router_get_lifetime(rt, &lifetime) >= 0);
+        log_info("Lifetime: %" PRIu16, lifetime);
+
+        if (sd_ndisc_router_get_mtu(rt, &mtu) < 0)
+                log_info("No MTU set");
+        else
+                log_info("MTU: %" PRIu32, mtu);
+
+        r = sd_ndisc_router_option_rewind(rt);
+        for (;;) {
+                uint8_t type;
+
+                assert_se(r >= 0);
+
+                if (r == 0)
+                        break;
+
+                assert_se(sd_ndisc_router_option_get_type(rt, &type) >= 0);
+
+                log_info(">> Option %u", type);
+
+                switch (type) {
+
+                case SD_NDISC_OPTION_SOURCE_LL_ADDRESS:
+                case SD_NDISC_OPTION_TARGET_LL_ADDRESS: {
+                        _cleanup_free_ char *c = NULL;
+                        const void *p;
+                        size_t n;
+
+                        assert_se(sd_ndisc_router_option_get_raw(rt, &p, &n) >= 0);
+                        assert_se(n > 2);
+                        assert_se(c = hexmem((uint8_t*) p + 2, n - 2));
+
+                        log_info("Address: %s", c);
+                        break;
+                }
+
+                case SD_NDISC_OPTION_PREFIX_INFORMATION: {
+                        uint32_t lifetime_valid, lifetime_preferred;
+                        unsigned prefix_len;
+                        uint8_t pfl;
+                        struct in6_addr a;
+
+                        assert_se(sd_ndisc_router_prefix_get_valid_lifetime(rt, &lifetime_valid) >= 0);
+                        log_info("Valid Lifetime: %" PRIu32, lifetime_valid);
+
+                        assert_se(sd_ndisc_router_prefix_get_preferred_lifetime(rt, &lifetime_preferred) >= 0);
+                        log_info("Preferred Lifetime: %" PRIu32, lifetime_preferred);
+
+                        assert_se(sd_ndisc_router_prefix_get_flags(rt, &pfl) >= 0);
+                        log_info("Flags: <%s|%s>",
+                                 pfl & ND_OPT_PI_FLAG_ONLINK ? "ONLINK" : "",
+                                 pfl & ND_OPT_PI_FLAG_AUTO ? "AUTO" : "");
+
+                        assert_se(sd_ndisc_router_prefix_get_prefixlen(rt, &prefix_len) >= 0);
+                        log_info("Prefix Length: %u", prefix_len);
+
+                        assert_se(sd_ndisc_router_prefix_get_address(rt, &a) >= 0);
+                        log_info("Prefix: %s", IN6_ADDR_TO_STRING(&a));
+
+                        break;
+                }
+
+                case SD_NDISC_OPTION_RDNSS: {
+                        const struct in6_addr *a;
+                        uint32_t lt;
+                        int n, i;
+
+                        n = sd_ndisc_router_rdnss_get_addresses(rt, &a);
+                        assert_se(n > 0);
+
+                        for (i = 0; i < n; i++)
+                                log_info("DNS: %s", IN6_ADDR_TO_STRING(a + i));
+
+                        assert_se(sd_ndisc_router_rdnss_get_lifetime(rt, &lt) >= 0);
+                        log_info("Lifetime: %" PRIu32, lt);
+                        break;
+                }
+
+                case SD_NDISC_OPTION_DNSSL: {
+                        _cleanup_strv_free_ char **l = NULL;
+                        uint32_t lt;
+                        int n, i;
+
+                        n = sd_ndisc_router_dnssl_get_domains(rt, &l);
+                        assert_se(n > 0);
+
+                        for (i = 0; i < n; i++)
+                                log_info("Domain: %s", l[i]);
+
+                        assert_se(sd_ndisc_router_dnssl_get_lifetime(rt, &lt) >= 0);
+                        log_info("Lifetime: %" PRIu32, lt);
+                        break;
+                }}
+
+                r = sd_ndisc_router_option_next(rt);
+        }
+}
+
+int icmp6_bind_router_solicitation(int ifindex) {
+        assert_se(ifindex == 42);
+
+        if (socketpair(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK, 0, test_fd) < 0)
+                return -errno;
+
+        return test_fd[0];
+}
+
+int icmp6_bind_router_advertisement(int ifindex) {
+        return -ENOSYS;
+}
+
+static struct in6_addr dummy_link_local = {
+        .s6_addr = {
+                0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x12, 0x34, 0x56, 0xff, 0xfe, 0x78, 0x9a, 0xbc,
+        },
+};
+
+int icmp6_receive(
+                int fd,
+                void *iov_base,
+                size_t iov_len,
+                struct in6_addr *ret_sender,
+                triple_timestamp *ret_timestamp) {
+
+        assert_se(read (fd, iov_base, iov_len) == (ssize_t)iov_len);
+
+        if (ret_timestamp)
+                triple_timestamp_get(ret_timestamp);
+
+        if (ret_sender)
+                *ret_sender = dummy_link_local;
+
+        return 0;
+}
+
+static int send_ra(uint8_t flags) {
+        uint8_t advertisement[] = {
+                0x86, 0x00, 0xde, 0x83, 0x40, 0xc0, 0x00, 0xb4,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x03, 0x04, 0x40, 0xc0, 0x00, 0x00, 0x01, 0xf4,
+                0x00, 0x00, 0x01, 0xb8, 0x00, 0x00, 0x00, 0x00,
+                0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x19, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
+                0x20, 0x01, 0x0d, 0xb8, 0xde, 0xad, 0xbe, 0xef,
+                0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01,
+                0x1f, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c,
+                0x03, 0x6c, 0x61, 0x62, 0x05, 0x69, 0x6e, 0x74,
+                0x72, 0x61, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                0x01, 0x01, 0x78, 0x2b, 0xcb, 0xb3, 0x6d, 0x53,
+        };
+
+        advertisement[5] = flags;
+
+        assert_se(write(test_fd[1], advertisement, sizeof(advertisement)) ==
+                  sizeof(advertisement));
+
+        if (verbose)
+                printf("  sent RA with flag 0x%02x\n", flags);
+
+        return 0;
+}
+
+int icmp6_send_router_solicitation(int s, const struct ether_addr *ether_addr) {
+        if (!send_ra_function)
+                return 0;
+
+        return send_ra_function(0);
+}
+
+static void test_callback(sd_ndisc *nd, sd_ndisc_event_t event, sd_ndisc_router *rt, void *userdata) {
+        sd_event *e = userdata;
+        static unsigned idx = 0;
+        uint64_t flags_array[] = {
+                0,
+                0,
+                0,
+                ND_RA_FLAG_OTHER,
+                ND_RA_FLAG_MANAGED
+        };
+        uint64_t flags;
+
+        assert_se(nd);
+
+        if (event != SD_NDISC_EVENT_ROUTER)
+                return;
+
+        router_dump(rt);
+
+        assert_se(sd_ndisc_router_get_flags(rt, &flags) >= 0);
+        assert_se(flags == flags_array[idx]);
+        idx++;
+
+        if (verbose)
+                printf("  got event 0x%02" PRIx64 "\n", flags);
+
+        if (idx < ELEMENTSOF(flags_array)) {
+                send_ra(flags_array[idx]);
+                return;
+        }
+
+        sd_event_exit(e, 0);
+}
+
+TEST(rs) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_ndisc_unrefp) sd_ndisc *nd = NULL;
+
+        send_ra_function = send_ra;
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        assert_se(sd_ndisc_new(&nd) >= 0);
+        assert_se(nd);
+
+        assert_se(sd_ndisc_attach_event(nd, e, 0) >= 0);
+
+        assert_se(sd_ndisc_set_ifindex(nd, 42) >= 0);
+        assert_se(sd_ndisc_set_mac(nd, &mac_addr) >= 0);
+        assert_se(sd_ndisc_set_callback(nd, test_callback, e) >= 0);
+
+        assert_se(sd_event_add_time_relative(e, NULL, CLOCK_BOOTTIME,
+                                             30 * USEC_PER_SEC, 0,
+                                             NULL, INT_TO_PTR(-ETIMEDOUT)) >= 0);
+
+        assert_se(sd_ndisc_stop(nd) >= 0);
+        assert_se(sd_ndisc_start(nd) >= 0);
+        assert_se(sd_ndisc_start(nd) >= 0);
+        assert_se(sd_ndisc_stop(nd) >= 0);
+        test_fd[1] = safe_close(test_fd[1]);
+
+        assert_se(sd_ndisc_start(nd) >= 0);
+
+        assert_se(sd_event_loop(e) >= 0);
+
+        test_fd[1] = safe_close(test_fd[1]);
+}
+
+static int test_timeout_value(uint8_t flags) {
+        static int count = 0;
+        static usec_t last = 0;
+        sd_ndisc *nd = test_timeout_nd;
+        usec_t min, max;
+
+        assert_se(nd);
+        assert_se(nd->event);
+
+        if (++count >= 20)
+                sd_event_exit(nd->event, 0);
+
+        if (last == 0) {
+                /* initial RT = IRT + RAND*IRT  */
+                min = NDISC_ROUTER_SOLICITATION_INTERVAL -
+                        NDISC_ROUTER_SOLICITATION_INTERVAL / 10;
+                max = NDISC_ROUTER_SOLICITATION_INTERVAL +
+                        NDISC_ROUTER_SOLICITATION_INTERVAL / 10;
+        } else {
+                /* next RT = 2*RTprev + RAND*RTprev */
+                min = 2 * last - last / 10;
+                max = 2 * last + last / 10;
+        }
+
+        /* final RT > MRT */
+        if (last * 2 > NDISC_MAX_ROUTER_SOLICITATION_INTERVAL) {
+                min = NDISC_MAX_ROUTER_SOLICITATION_INTERVAL -
+                        NDISC_MAX_ROUTER_SOLICITATION_INTERVAL / 10;
+                max = NDISC_MAX_ROUTER_SOLICITATION_INTERVAL +
+                        NDISC_MAX_ROUTER_SOLICITATION_INTERVAL / 10;
+        }
+
+        log_info("backoff timeout interval %2d %s%s <= %s <= %s",
+                 count,
+                 last * 2 > NDISC_MAX_ROUTER_SOLICITATION_INTERVAL ? "(max) ": "",
+                 FORMAT_TIMESPAN(min, USEC_PER_MSEC),
+                 FORMAT_TIMESPAN(nd->retransmit_time, USEC_PER_MSEC),
+                 FORMAT_TIMESPAN(max, USEC_PER_MSEC));
+
+        assert_se(min <= nd->retransmit_time);
+        assert_se(max >= nd->retransmit_time);
+
+        last = nd->retransmit_time;
+
+        assert_se(sd_event_source_set_time(nd->timeout_event_source, 0) >= 0);
+
+        return 0;
+}
+
+TEST(timeout) {
+        _cleanup_(sd_event_unrefp) sd_event *e = NULL;
+        _cleanup_(sd_ndisc_unrefp) sd_ndisc *nd = NULL;
+
+        send_ra_function = test_timeout_value;
+
+        assert_se(sd_event_new(&e) >= 0);
+
+        assert_se(sd_ndisc_new(&nd) >= 0);
+        assert_se(nd);
+
+        test_timeout_nd = nd;
+
+        assert_se(sd_ndisc_attach_event(nd, e, 0) >= 0);
+
+        assert_se(sd_ndisc_set_ifindex(nd, 42) >= 0);
+        assert_se(sd_ndisc_set_mac(nd, &mac_addr) >= 0);
+
+        assert_se(sd_event_add_time_relative(e, NULL, CLOCK_BOOTTIME,
+                                             30 * USEC_PER_SEC, 0,
+                                             NULL, INT_TO_PTR(-ETIMEDOUT)) >= 0);
+
+        assert_se(sd_ndisc_start(nd) >= 0);
+
+        assert_se(sd_event_loop(e) >= 0);
+
+        test_fd[1] = safe_close(test_fd[1]);
+}
+
+DEFINE_TEST_MAIN(LOG_DEBUG);
diff --git a/src/libsystemd-network/test-sd-dhcp-lease.c b/src/libsystemd-network/test-sd-dhcp-lease.c
new file mode 100644
index 0000000..910b622
--- /dev/null
+++ b/src/libsystemd-network/test-sd-dhcp-lease.c
@@ -0,0 +1,86 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+
+#include "dhcp-lease-internal.h"
+#include "macro.h"
+#include "string-util.h"
+#include "strv.h"
+#include "tests.h"
+
+/* According to RFC1035 section 4.1.4, a domain name in a message can be either:
+ *      - a sequence of labels ending in a zero octet
+ *      - a pointer
+ *      - a sequence of labels ending with a pointer
+ */
+TEST(dhcp_lease_parse_search_domains_basic) {
+        int r;
+        _cleanup_strv_free_ char **domains = NULL;
+        static const uint8_t optionbuf[] = {
+                0x03, 'F', 'O', 'O', 0x03, 'B', 'A', 'R', 0x00,
+                0x04, 'A', 'B', 'C', 'D', 0x03, 'E', 'F', 'G', 0x00,
+        };
+
+        r = dhcp_lease_parse_search_domains(optionbuf, sizeof(optionbuf), &domains);
+        assert_se(r == 2);
+        assert_se(streq(domains[0], "FOO.BAR"));
+        assert_se(streq(domains[1], "ABCD.EFG"));
+}
+
+TEST(dhcp_lease_parse_search_domains_ptr) {
+        int r;
+        _cleanup_strv_free_ char **domains = NULL;
+        static const uint8_t optionbuf[] = {
+                0x03, 'F', 'O', 'O', 0x00, 0xC0, 0x00,
+        };
+
+        r = dhcp_lease_parse_search_domains(optionbuf, sizeof(optionbuf), &domains);
+        assert_se(r == 2);
+        assert_se(streq(domains[0], "FOO"));
+        assert_se(streq(domains[1], "FOO"));
+}
+
+TEST(dhcp_lease_parse_search_domains_labels_and_ptr) {
+        int r;
+        _cleanup_strv_free_ char **domains = NULL;
+        static const uint8_t optionbuf[] = {
+                0x03, 'F', 'O', 'O', 0x03, 'B', 'A', 'R', 0x00,
+                0x03, 'A', 'B', 'C', 0xC0, 0x04,
+        };
+
+        r = dhcp_lease_parse_search_domains(optionbuf, sizeof(optionbuf), &domains);
+        assert_se(r == 2);
+        assert_se(streq(domains[0], "FOO.BAR"));
+        assert_se(streq(domains[1], "ABC.BAR"));
+}
+
+/* Tests for exceptions. */
+
+TEST(dhcp_lease_parse_search_domains_no_data) {
+        _cleanup_strv_free_ char **domains = NULL;
+        static const uint8_t optionbuf[3] = {0, 0, 0};
+
+        assert_se(dhcp_lease_parse_search_domains(NULL, 0, &domains) == -EBADMSG);
+        assert_se(dhcp_lease_parse_search_domains(optionbuf, 0, &domains) == -EBADMSG);
+}
+
+TEST(dhcp_lease_parse_search_domains_loops) {
+        _cleanup_strv_free_ char **domains = NULL;
+        static const uint8_t optionbuf[] = {
+                0x03, 'F', 'O', 'O', 0x00, 0x03, 'B', 'A', 'R', 0xC0, 0x06,
+        };
+
+        assert_se(dhcp_lease_parse_search_domains(optionbuf, sizeof(optionbuf), &domains) == -EBADMSG);
+}
+
+TEST(dhcp_lease_parse_search_domains_wrong_len) {
+        _cleanup_strv_free_ char **domains = NULL;
+        static const uint8_t optionbuf[] = {
+                0x03, 'F', 'O', 'O', 0x03, 'B', 'A', 'R', 0x00,
+                0x04, 'A', 'B', 'C', 'D', 0x03, 'E', 'F', 'G', 0x00,
+        };
+
+        assert_se(dhcp_lease_parse_search_domains(optionbuf, sizeof(optionbuf) - 5, &domains) == -EBADMSG);
+}
+
+DEFINE_TEST_MAIN(LOG_INFO);