Adding upstream version 255.4.upstream/255.4

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

1 files changed, 1594 insertions, 0 deletions

diff --git a/src/libsystemd-network/sd-dhcp6-client.c b/src/libsystemd-network/sd-dhcp6-client.c
new file mode 100644
index 0000000..c20367d
--- /dev/null
+++ b/src/libsystemd-network/sd-dhcp6-client.c
@@ -0,0 +1,1594 @@
+/* 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 "device-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 "iovec-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 dhcp6_client_set_state_callback(
+                sd_dhcp6_client *client,
+                sd_dhcp6_client_callback_t cb,
+                void *userdata) {
+
+        assert_return(client, -EINVAL);
+
+        client->state_callback = cb;
+        client->state_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->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.
+ */
+int sd_dhcp6_client_set_duid_llt(sd_dhcp6_client *client, uint64_t llt_time) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        r = dhcp_identifier_set_duid_llt(&client->hw_addr, client->arp_type, llt_time, &client->duid, &client->duid_len);
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to set DUID-LLT: %m");
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_duid_ll(sd_dhcp6_client *client) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        r = dhcp_identifier_set_duid_ll(&client->hw_addr, client->arp_type, &client->duid, &client->duid_len);
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to set DUID-LL: %m");
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_duid_en(sd_dhcp6_client *client) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        r = dhcp_identifier_set_duid_en(&client->duid, &client->duid_len);
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to set DUID-EN: %m");
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_duid_uuid(sd_dhcp6_client *client) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        r = dhcp_identifier_set_duid_uuid(&client->duid, &client->duid_len);
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to set DUID-UUID: %m");
+
+        return 0;
+}
+
+int sd_dhcp6_client_set_duid_raw(sd_dhcp6_client *client, uint16_t duid_type, const uint8_t *duid, size_t duid_len) {
+        int r;
+
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+        assert_return(duid || duid_len == 0, -EINVAL);
+
+        r = dhcp_identifier_set_duid_raw(duid_type, duid, duid_len, &client->duid, &client->duid_len);
+        if (r < 0)
+                return log_dhcp6_client_errno(client, r, "Failed to set DUID: %m");
+
+        return 0;
+}
+
+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->dev, &client->hw_addr,
+                                     /* legacy_unstable_byteorder = */ true,
+                                     &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;
+}
+
+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_se(network_test_mode_enabled());
+
+        /* 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_set_send_release(sd_dhcp6_client *client, int enable) {
+        assert_return(client, -EINVAL);
+        assert_return(!sd_dhcp6_client_is_running(client), -EBUSY);
+
+        client->send_release = 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;
+
+        if (client->state_callback)
+                client->state_callback(client, state, client->state_userdata);
+}
+
+int dhcp6_client_get_state(sd_dhcp6_client *client) {
+        assert_return(client, -EINVAL);
+
+        return client->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,
+                      DHCP6_STATE_STOPPING));
+        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;
+        }
+
+        if (client->state != DHCP6_STATE_STOPPING) {
+                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;
+        case DHCP6_STATE_STOPPING:
+                return DHCP6_MESSAGE_RELEASE;
+        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;
+
+        case DHCP6_STATE_STOPPING:
+                return 0;
+
+        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);
+}
+
+static int client_append_mudurl(sd_dhcp6_client *client, uint8_t **buf, size_t *offset) {
+        assert(client);
+        assert(buf);
+        assert(*buf);
+        assert(offset);
+
+        if (!client->mudurl)
+                return 0;
+
+        if (client->state == DHCP6_STATE_STOPPING)
+                return 0;
+
+        return dhcp6_option_append(buf, offset, SD_DHCP6_OPTION_MUD_URL_V6,
+                                   strlen(client->mudurl), client->mudurl);
+}
+
+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:
+        case DHCP6_STATE_STOPPING:
+                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_BOUND:
+        case DHCP6_STATE_STOPPED:
+        default:
+                assert_not_reached();
+        }
+
+        r = client_append_mudurl(client, &buf, &offset);
+        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_STOPPING:
+        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_STOPPING:
+        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 = sd_dhcp6_lease_get_t1(client->lease, &lifetime_t1);
+        if (r < 0)
+                goto error;
+
+        r = sd_dhcp6_lease_get_t2(client->lease, &lifetime_t2);
+        if (r < 0)
+                goto error;
+
+        r = sd_dhcp6_lease_get_valid_lifetime(client->lease, &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),
+        };
+        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 (ERRNO_IS_NEG_TRANSIENT(buflen) || ERRNO_IS_NEG_DISCONNECT(buflen))
+                return 0;
+        if (buflen < 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 (ERRNO_IS_NEG_TRANSIENT(len) || ERRNO_IS_NEG_DISCONNECT(len))
+                return 0;
+        if (len < 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;
+        }
+
+        triple_timestamp_from_cmsg(&t, &msg);
+
+        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:
+        case DHCP6_STATE_STOPPING:
+        default:
+                assert_not_reached();
+        }
+
+        return 0;
+}
+
+static int client_send_release(sd_dhcp6_client *client) {
+        sd_dhcp6_lease *lease;
+
+        assert(client);
+
+        if (!client->send_release)
+                return 0;
+
+        if (sd_dhcp6_client_get_lease(client, &lease) < 0)
+                return 0;
+
+        if (!lease->ia_na && !lease->ia_pd)
+                return 0;
+
+        client_set_state(client, DHCP6_STATE_STOPPING);
+        return dhcp6_client_send_message(client);
+}
+
+int sd_dhcp6_client_stop(sd_dhcp6_client *client) {
+        int r;
+
+        if (!client)
+                return 0;
+
+        /* Intentionally ignoring failure to send DHCP6 release. The DHCPv6 client
+         * engine is about to release its UDP socket unconditionally. */
+        r = client_send_release(client);
+        if (r < 0)
+                log_dhcp6_client_errno(client, r,
+                                       "Failed to send DHCP6 release message, ignoring: %m");
+
+        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;
+}
+
+int sd_dhcp6_client_attach_device(sd_dhcp6_client *client, sd_device *dev) {
+        assert_return(client, -EINVAL);
+
+        return device_unref_and_replace(client->dev, dev);
+}
+
+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);
+
+        sd_device_unref(client->dev);
+
+        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 = -EBADF,
+                .rapid_commit = true,
+        };
+
+        *ret = TAKE_PTR(client);
+
+        return 0;
+}