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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:35:18 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:35:18 +0000
commitb750101eb236130cf056c675997decbac904cc49 (patch)
treea5df1a06754bdd014cb975c051c83b01c9a97532 /src/shared/firewall-util-nft.c
parentInitial commit. (diff)
downloadsystemd-b750101eb236130cf056c675997decbac904cc49.tar.xz
systemd-b750101eb236130cf056c675997decbac904cc49.zip
Adding upstream version 252.22.upstream/252.22
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--src/shared/firewall-util-nft.c1089
1 files changed, 1089 insertions, 0 deletions
diff --git a/src/shared/firewall-util-nft.c b/src/shared/firewall-util-nft.c
new file mode 100644
index 0000000..b5f0d1b
--- /dev/null
+++ b/src/shared/firewall-util-nft.c
@@ -0,0 +1,1089 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <arpa/inet.h>
+#include <endian.h>
+#include <errno.h>
+#include <stddef.h>
+#include <string.h>
+#include <linux/netfilter/nf_tables.h>
+#include <linux/netfilter/nf_nat.h>
+#include <linux/netfilter_ipv4.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+
+#include "sd-netlink.h"
+
+#include "alloc-util.h"
+#include "firewall-util.h"
+#include "firewall-util-private.h"
+#include "in-addr-util.h"
+#include "macro.h"
+#include "netlink-internal.h"
+#include "netlink-util.h"
+#include "socket-util.h"
+#include "time-util.h"
+
+#define NFT_SYSTEMD_DNAT_MAP_NAME "map_port_ipport"
+#define NFT_SYSTEMD_TABLE_NAME "io.systemd.nat"
+#define NFT_SYSTEMD_MASQ_SET_NAME "masq_saddr"
+
+#define NFNL_DEFAULT_TIMEOUT_USECS (1ULL * USEC_PER_SEC)
+
+#define UDP_DPORT_OFFSET 2
+
+static sd_netlink_message **netlink_message_unref_many(sd_netlink_message **m) {
+ if (!m)
+ return NULL;
+
+ /* This does not free array. The end of the array must be NULL. */
+
+ for (sd_netlink_message **p = m; *p; p++)
+ *p = sd_netlink_message_unref(*p);
+
+ return m;
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(sd_netlink_message**, netlink_message_unref_many);
+
+static int nfnl_open_expr_container(sd_netlink_message *m, const char *name) {
+ int r;
+
+ assert(m);
+ assert(name);
+
+ r = sd_netlink_message_open_array(m, NFTA_LIST_ELEM);
+ if (r < 0)
+ return r;
+
+ return sd_netlink_message_open_container_union(m, NFTA_EXPR_DATA, name);
+}
+
+static int nfnl_close_expr_container(sd_netlink_message *m) {
+ int r;
+
+ assert(m);
+
+ r = sd_netlink_message_close_container(m); /* NFTA_EXPR_DATA */
+ if (r < 0)
+ return r;
+
+ return sd_netlink_message_close_container(m); /* NFTA_LIST_ELEM */
+}
+
+static int nfnl_add_expr_fib(
+ sd_netlink_message *m,
+ uint32_t nft_fib_flags,
+ enum nft_fib_result result,
+ enum nft_registers dreg) {
+
+ int r;
+
+ assert(m);
+
+ r = nfnl_open_expr_container(m, "fib");
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_FIB_FLAGS, htobe32(nft_fib_flags));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_FIB_RESULT, htobe32(result));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_FIB_DREG, htobe32(dreg));
+ if (r < 0)
+ return r;
+
+ return nfnl_close_expr_container(m);
+}
+
+static int nfnl_add_expr_meta(
+ sd_netlink_message *m,
+ enum nft_meta_keys key,
+ enum nft_registers dreg) {
+
+ int r;
+
+ assert(m);
+
+ r = nfnl_open_expr_container(m, "meta");
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_META_KEY, htobe32(key));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_META_DREG, htobe32(dreg));
+ if (r < 0)
+ return r;
+
+ return nfnl_close_expr_container(m);
+}
+
+static int nfnl_add_expr_payload(
+ sd_netlink_message *m,
+ enum nft_payload_bases pb,
+ uint32_t offset,
+ uint32_t len,
+ enum nft_registers dreg) {
+
+ int r;
+
+ assert(m);
+
+ r = nfnl_open_expr_container(m, "payload");
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_DREG, htobe32(dreg));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_BASE, htobe32(pb));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_OFFSET, htobe32(offset));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_PAYLOAD_LEN, htobe32(len));
+ if (r < 0)
+ return r;
+
+ return nfnl_close_expr_container(m);
+}
+
+static int nfnl_add_expr_lookup(
+ sd_netlink_message *m,
+ const char *set_name,
+ enum nft_registers sreg,
+ enum nft_registers dreg) {
+
+ int r;
+
+ assert(m);
+ assert(set_name);
+
+ r = nfnl_open_expr_container(m, "lookup");
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_string(m, NFTA_LOOKUP_SET, set_name);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_LOOKUP_SREG, htobe32(sreg));
+ if (r < 0)
+ return r;
+
+ if (dreg != 0) {
+ r = sd_netlink_message_append_u32(m, NFTA_LOOKUP_DREG, htobe32(dreg));
+ if (r < 0)
+ return r;
+ }
+
+ return nfnl_close_expr_container(m);
+}
+
+static int nfnl_add_expr_cmp(
+ sd_netlink_message *m,
+ enum nft_cmp_ops cmp_op,
+ enum nft_registers sreg,
+ const void *data,
+ size_t dlen) {
+
+ int r;
+
+ assert(m);
+ assert(data);
+
+ r = nfnl_open_expr_container(m, "cmp");
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_CMP_OP, htobe32(cmp_op));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_CMP_SREG, htobe32(sreg));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_container_data(m, NFTA_CMP_DATA, NFTA_DATA_VALUE, data, dlen);
+ if (r < 0)
+ return r;
+
+ return nfnl_close_expr_container(m);
+}
+
+static int nfnl_add_expr_bitwise(
+ sd_netlink_message *m,
+ enum nft_registers sreg,
+ enum nft_registers dreg,
+ const void *and,
+ const void *xor,
+ uint32_t len) {
+
+ int r;
+
+ assert(m);
+ assert(and);
+ assert(xor);
+
+ r = nfnl_open_expr_container(m, "bitwise");
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_BITWISE_SREG, htobe32(sreg));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_BITWISE_DREG, htobe32(dreg));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_BITWISE_LEN, htobe32(len));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_container_data(m, NFTA_BITWISE_MASK, NFTA_DATA_VALUE, and, len);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_container_data(m, NFTA_BITWISE_XOR, NFTA_DATA_VALUE, xor, len);
+ if (r < 0)
+ return r;
+
+ return nfnl_close_expr_container(m);
+}
+
+static int nfnl_add_expr_dnat(
+ sd_netlink_message *m,
+ int family,
+ enum nft_registers areg,
+ enum nft_registers preg) {
+
+ int r;
+
+ assert(m);
+
+ r = nfnl_open_expr_container(m, "nat");
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_NAT_TYPE, htobe32(NFT_NAT_DNAT));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_NAT_FAMILY, htobe32(family));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_NAT_REG_ADDR_MIN, htobe32(areg));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_NAT_REG_PROTO_MIN, htobe32(preg));
+ if (r < 0)
+ return r;
+
+ return nfnl_close_expr_container(m);
+}
+
+static int nfnl_add_expr_masq(sd_netlink_message *m) {
+ int r;
+
+ r = sd_netlink_message_open_array(m, NFTA_LIST_ELEM);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_string(m, NFTA_EXPR_NAME, "masq");
+ if (r < 0)
+ return r;
+
+ return sd_netlink_message_close_container(m); /* NFTA_LIST_ELEM */
+}
+
+static int sd_nfnl_message_new_masq_rule(
+ sd_netlink *nfnl,
+ sd_netlink_message **ret,
+ int family,
+ const char *chain) {
+
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ int r;
+
+ /* -t nat -A POSTROUTING -p protocol -s source/pflen -o out_interface -d destination/pflen -j MASQUERADE */
+
+ assert(nfnl);
+ assert(ret);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+ assert(chain);
+
+ r = sd_nfnl_nft_message_new_rule(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, chain);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_open_container(m, NFTA_RULE_EXPRESSIONS);
+ if (r < 0)
+ return r;
+
+ /* 1st statement: ip saddr @masq_saddr. Place iph->saddr in reg1, resp. ipv6 in reg1..reg4. */
+ if (family == AF_INET)
+ r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct iphdr, saddr),
+ sizeof(uint32_t), NFT_REG32_01);
+ else
+ r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct ip6_hdr, ip6_src.s6_addr),
+ sizeof(struct in6_addr), NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ /* 1st statement: use reg1 content to make lookup in @masq_saddr set. */
+ r = nfnl_add_expr_lookup(m, NFT_SYSTEMD_MASQ_SET_NAME, NFT_REG32_01, 0);
+ if (r < 0)
+ return r;
+
+ /* 2nd statement: masq. Only executed by kernel if the previous lookup was successful. */
+ r = nfnl_add_expr_masq(m);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_close_container(m); /* NFTA_RULE_EXPRESSIONS */
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(m);
+ return 0;
+}
+
+static int sd_nfnl_message_new_dnat_rule_pre(
+ sd_netlink *nfnl,
+ sd_netlink_message **ret,
+ int family,
+ const char *chain) {
+
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ enum nft_registers proto_reg;
+ uint32_t local = RTN_LOCAL;
+ int r;
+
+ /* -t nat -A PREROUTING -p protocol --dport local_port -i in_interface -s source/pflen
+ * -d destination/pflen -j DNAT --to-destination remote_addr:remote_port */
+
+ assert(nfnl);
+ assert(ret);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+ assert(chain);
+
+ r = sd_nfnl_nft_message_new_rule(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, chain);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_open_container(m, NFTA_RULE_EXPRESSIONS);
+ if (r < 0)
+ return r;
+
+ /* 1st statement: fib daddr type local */
+ r = nfnl_add_expr_fib(m, NFTA_FIB_F_DADDR, NFT_FIB_RESULT_ADDRTYPE, NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ /* 1st statement (cont.): compare RTN_LOCAL */
+ r = nfnl_add_expr_cmp(m, NFT_CMP_EQ, NFT_REG32_01, &local, sizeof(local));
+ if (r < 0)
+ return r;
+
+ /* 2nd statement: lookup local port in map, fetch address:dport to map to */
+ r = nfnl_add_expr_meta(m, NFT_META_L4PROTO, NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ r = nfnl_add_expr_payload(m, NFT_PAYLOAD_TRANSPORT_HEADER, UDP_DPORT_OFFSET,
+ sizeof(uint16_t), NFT_REG32_02);
+ if (r < 0)
+ return r;
+
+ /* 3rd statement: lookup 'l4proto . dport', e.g. 'tcp . 22' as key and
+ * store address and port for the dnat mapping in REG1/REG2. */
+ r = nfnl_add_expr_lookup(m, NFT_SYSTEMD_DNAT_MAP_NAME, NFT_REG32_01, NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ proto_reg = family == AF_INET ? NFT_REG32_02 : NFT_REG32_05;
+ r = nfnl_add_expr_dnat(m, family, NFT_REG32_01, proto_reg);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_close_container(m); /* NFTA_RULE_EXPRESSIONS */
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(m);
+ return 0;
+}
+
+static int sd_nfnl_message_new_dnat_rule_out(
+ sd_netlink *nfnl,
+ sd_netlink_message **ret,
+ int family,
+ const char *chain) {
+
+ static const uint32_t zero = 0, one = 1;
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ enum nft_registers proto_reg;
+ int r;
+
+ assert(nfnl);
+ assert(ret);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+ assert(chain);
+
+ r = sd_nfnl_nft_message_new_rule(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, chain);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_open_container(m, NFTA_RULE_EXPRESSIONS);
+ if (r < 0)
+ return r;
+
+ /* 1st statement: exclude 127.0.0.1/8: ip daddr != 127.0.0.1/8, resp. avoid ::1 */
+ if (family == AF_INET) {
+ uint32_t lonet = htobe32(UINT32_C(0x7F000000)), lomask = htobe32(UINT32_C(0xff000000));
+
+ r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct iphdr, daddr),
+ sizeof(lonet), NFT_REG32_01);
+ if (r < 0)
+ return r;
+ /* 1st statement (cont.): bitops/prefix */
+ r = nfnl_add_expr_bitwise(m, NFT_REG32_01, NFT_REG32_01, &lomask, &zero, sizeof(lomask));
+ if (r < 0)
+ return r;
+
+ /* 1st statement (cont.): compare reg1 with 127/8 */
+ r = nfnl_add_expr_cmp(m, NFT_CMP_NEQ, NFT_REG32_01, &lonet, sizeof(lonet));
+ } else {
+ struct in6_addr loaddr = IN6ADDR_LOOPBACK_INIT;
+
+ r = nfnl_add_expr_payload(m, NFT_PAYLOAD_NETWORK_HEADER, offsetof(struct ip6_hdr, ip6_dst.s6_addr),
+ sizeof(loaddr), NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ r = nfnl_add_expr_cmp(m, NFT_CMP_NEQ, NFT_REG32_01, &loaddr, sizeof(loaddr));
+ }
+ if (r < 0)
+ return r;
+
+ /* 2nd statement: meta oif lo */
+ r = nfnl_add_expr_meta(m, NFT_META_OIF, NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ /* 2nd statement (cont.): compare to lo ifindex (1) */
+ r = nfnl_add_expr_cmp(m, NFT_CMP_EQ, NFT_REG32_01, &one, sizeof(one));
+ if (r < 0)
+ return r;
+
+ /* 3rd statement: meta l4proto . th dport dnat ip . port to map @map_port_ipport */
+ r = nfnl_add_expr_meta(m, NFT_META_L4PROTO, NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ /* 3rd statement (cont): store the port number in reg2 */
+ r = nfnl_add_expr_payload(m, NFT_PAYLOAD_TRANSPORT_HEADER, UDP_DPORT_OFFSET,
+ sizeof(uint16_t), NFT_REG32_02);
+ if (r < 0)
+ return r;
+
+ /* 3rd statement (cont): use reg1 and reg2 and retrieve
+ * the new destination ip and port number.
+ *
+ * reg1 and reg2 are clobbered and will then contain the new
+ * address/port number. */
+ r = nfnl_add_expr_lookup(m, NFT_SYSTEMD_DNAT_MAP_NAME, NFT_REG32_01, NFT_REG32_01);
+ if (r < 0)
+ return r;
+
+ /* 4th statement: dnat connection to address/port retrieved by the
+ * preceding expression. */
+ proto_reg = family == AF_INET ? NFT_REG32_02 : NFT_REG32_05;
+ r = nfnl_add_expr_dnat(m, family, NFT_REG32_01, proto_reg);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_close_container(m); /* NFTA_RULE_EXPRESSIONS */
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(m);
+ return 0;
+}
+
+static int nft_new_set(
+ struct sd_netlink *nfnl,
+ sd_netlink_message **ret,
+ int family,
+ const char *set_name,
+ uint32_t set_id,
+ uint32_t flags,
+ uint32_t type,
+ uint32_t klen) {
+
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ int r;
+
+ assert(nfnl);
+ assert(ret);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+ assert(set_name);
+
+ r = sd_nfnl_nft_message_new_set(nfnl, &m, family, NFT_SYSTEMD_TABLE_NAME, set_name, set_id, klen);
+ if (r < 0)
+ return r;
+
+ if (flags != 0) {
+ r = sd_netlink_message_append_u32(m, NFTA_SET_FLAGS, htobe32(flags));
+ if (r < 0)
+ return r;
+ }
+
+ r = sd_netlink_message_append_u32(m, NFTA_SET_KEY_TYPE, htobe32(type));
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(m);
+ return r;
+}
+
+static int nft_new_map(
+ struct sd_netlink *nfnl,
+ sd_netlink_message **ret,
+ int family,
+ const char *set_name,
+ uint32_t set_id,
+ uint32_t flags,
+ uint32_t type,
+ uint32_t klen,
+ uint32_t dtype,
+ uint32_t dlen) {
+
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ int r;
+
+ assert(nfnl);
+ assert(ret);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+ assert(set_name);
+
+ r = nft_new_set(nfnl, &m, family, set_name, set_id, flags | NFT_SET_MAP, type, klen);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_SET_DATA_TYPE, htobe32(dtype));
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_append_u32(m, NFTA_SET_DATA_LEN, htobe32(dlen));
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(m);
+ return 0;
+}
+
+static int nft_add_element(
+ sd_netlink *nfnl,
+ sd_netlink_message **ret,
+ int family,
+ const char *set_name,
+ const void *key,
+ uint32_t klen,
+ const void *data,
+ uint32_t dlen) {
+
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ int r;
+
+ assert(nfnl);
+ assert(ret);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+ assert(set_name);
+ assert(key);
+ assert(data);
+
+ /*
+ * Ideally there would be an API that provides:
+ *
+ * 1) an init function to add the main ruleset skeleton
+ * 2) a function that populates the sets with all known address/port pairs to s/dnat for
+ * 3) a function that can remove address/port pairs again.
+ *
+ * At this time, the existing API is used which is built on a
+ * 'add/delete a rule' paradigm.
+ *
+ * This replicated here and each element gets added to the set
+ * one-by-one.
+ */
+ r = sd_nfnl_nft_message_new_setelems(nfnl, &m, /* add = */ true, family, NFT_SYSTEMD_TABLE_NAME, set_name);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_append_setelem(m, 0, key, klen, data, dlen, 0);
+ if (r < 0)
+ return r;
+
+ /* could theoretically append more set elements to add here */
+
+ r = sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(m);
+ return 0;
+}
+
+static int nft_del_element(
+ sd_netlink *nfnl,
+ sd_netlink_message **ret,
+ int family,
+ const char *set_name,
+ const void *key,
+ uint32_t klen,
+ const void *data,
+ uint32_t dlen) {
+
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ int r;
+
+ assert(nfnl);
+ assert(ret);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+ assert(set_name);
+ assert(key);
+ assert(data);
+
+ r = sd_nfnl_nft_message_new_setelems(nfnl, &m, /* add = */ false, family, NFT_SYSTEMD_TABLE_NAME, set_name);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_append_setelem(m, 0, key, klen, data, dlen, 0);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */
+ if (r < 0)
+ return r;
+
+ *ret = TAKE_PTR(m);
+ return 0;
+}
+
+/* This is needed so 'nft' userspace tool can properly format the contents
+ * of the set/map when someone uses 'nft' to inspect their content.
+ *
+ * The values cannot be changed, they are part of the nft tool type identifier ABI. */
+#define TYPE_BITS 6
+
+enum nft_key_types {
+ TYPE_IPADDR = 7,
+ TYPE_IP6ADDR = 8,
+ TYPE_INET_PROTOCOL = 12,
+ TYPE_INET_SERVICE = 13,
+};
+
+static uint32_t concat_types2(enum nft_key_types a, enum nft_key_types b) {
+ uint32_t type = (uint32_t)a;
+
+ type <<= TYPE_BITS;
+ type |= (uint32_t)b;
+
+ return type;
+}
+
+static int fw_nftables_init_family(sd_netlink *nfnl, int family) {
+ sd_netlink_message *messages[10] = {};
+ _unused_ _cleanup_(netlink_message_unref_manyp) sd_netlink_message **unref = messages;
+ size_t msgcnt = 0, ip_type_size;
+ uint32_t set_id = 0;
+ int ip_type, r;
+
+ assert(nfnl);
+ assert(IN_SET(family, AF_INET, AF_INET6));
+
+ /* Set F_EXCL so table add fails if the table already exists. */
+ r = sd_nfnl_nft_message_new_table(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_new_basechain(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME,
+ "prerouting", "nat",
+ NF_INET_PRE_ROUTING, NF_IP_PRI_NAT_DST + 1);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_new_basechain(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME,
+ "output", "nat",
+ NF_INET_LOCAL_OUT, NF_IP_PRI_NAT_DST + 1);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_new_basechain(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_TABLE_NAME,
+ "postrouting", "nat",
+ NF_INET_POST_ROUTING, NF_IP_PRI_NAT_SRC + 1);
+ if (r < 0)
+ return r;
+
+ if (family == AF_INET) {
+ ip_type_size = sizeof(uint32_t);
+ ip_type = TYPE_IPADDR;
+ } else {
+ assert(family == AF_INET6);
+ ip_type_size = sizeof(struct in6_addr);
+ ip_type = TYPE_IP6ADDR;
+ }
+ /* set to store ip address ranges we should masquerade for */
+ r = nft_new_set(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_MASQ_SET_NAME, ++set_id, NFT_SET_INTERVAL, ip_type, ip_type_size);
+ if (r < 0)
+ return r;
+
+ /*
+ * map to store ip address:port pair to dnat to. elements in concatenation
+ * are rounded up to 4 bytes.
+ *
+ * Example: ip protocol . tcp daddr is sizeof(uint32_t) + sizeof(uint32_t), not
+ * sizeof(uint8_t) + sizeof(uint16_t).
+ */
+ r = nft_new_map(nfnl, &messages[msgcnt++], family, NFT_SYSTEMD_DNAT_MAP_NAME, ++set_id, 0,
+ concat_types2(TYPE_INET_PROTOCOL, TYPE_INET_SERVICE), sizeof(uint32_t) * 2,
+ concat_types2(ip_type, TYPE_INET_SERVICE), ip_type_size + sizeof(uint32_t));
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_message_new_dnat_rule_pre(nfnl, &messages[msgcnt++], family, "prerouting");
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_message_new_dnat_rule_out(nfnl, &messages[msgcnt++], family, "output");
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_message_new_masq_rule(nfnl, &messages[msgcnt++], family, "postrouting");
+ if (r < 0)
+ return r;
+
+ assert(msgcnt < ELEMENTSOF(messages));
+ r = sd_nfnl_call_batch(nfnl, messages, msgcnt, NFNL_DEFAULT_TIMEOUT_USECS, NULL);
+ if (r < 0 && r != -EEXIST)
+ return r;
+
+ return 0;
+}
+
+int fw_nftables_init(FirewallContext *ctx) {
+ _cleanup_(sd_netlink_unrefp) sd_netlink *nfnl = NULL;
+ int r;
+
+ assert(ctx);
+ assert(!ctx->nfnl);
+
+ r = sd_nfnl_socket_open(&nfnl);
+ if (r < 0)
+ return r;
+
+ r = fw_nftables_init_family(nfnl, AF_INET);
+ if (r < 0)
+ return r;
+
+ if (socket_ipv6_is_supported()) {
+ r = fw_nftables_init_family(nfnl, AF_INET6);
+ if (r < 0)
+ log_debug_errno(r, "Failed to init ipv6 NAT: %m");
+ }
+
+ ctx->nfnl = TAKE_PTR(nfnl);
+ return 0;
+}
+
+void fw_nftables_exit(FirewallContext *ctx) {
+ assert(ctx);
+
+ ctx->nfnl = sd_netlink_unref(ctx->nfnl);
+}
+
+static int nft_message_append_setelem_iprange(
+ sd_netlink_message *m,
+ const union in_addr_union *source,
+ unsigned int prefixlen) {
+
+ uint32_t mask, start, end;
+ unsigned int nplen;
+ int r;
+
+ assert(m);
+ assert(source);
+ assert(prefixlen <= 32);
+
+ nplen = 32 - prefixlen;
+
+ mask = (1U << nplen) - 1U;
+ mask = htobe32(~mask);
+ start = source->in.s_addr & mask;
+
+ r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_append_setelem(m, 0, &start, sizeof(start), NULL, 0, 0);
+ if (r < 0)
+ return r;
+
+ end = be32toh(start) + (1U << nplen);
+ if (end < be32toh(start))
+ end = 0U;
+ end = htobe32(end);
+
+ r = sd_nfnl_nft_message_append_setelem(m, 1, &end, sizeof(end), NULL, 0, NFT_SET_ELEM_INTERVAL_END);
+ if (r < 0)
+ return r;
+
+ return sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */
+}
+
+static int nft_message_append_setelem_ip6range(
+ sd_netlink_message *m,
+ const union in_addr_union *source,
+ unsigned int prefixlen) {
+
+ union in_addr_union start, end;
+ int r;
+
+ assert(m);
+ assert(source);
+
+ r = in_addr_prefix_range(AF_INET6, source, prefixlen, &start, &end);
+ if (r < 0)
+ return r;
+
+ r = sd_netlink_message_open_container(m, NFTA_SET_ELEM_LIST_ELEMENTS);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_append_setelem(m, 0, &start.in6, sizeof(start.in6), NULL, 0, 0);
+ if (r < 0)
+ return r;
+
+ r = sd_nfnl_nft_message_append_setelem(m, 1, &end.in6, sizeof(end.in6), NULL, 0, NFT_SET_ELEM_INTERVAL_END);
+ if (r < 0)
+ return r;
+
+ return sd_netlink_message_close_container(m); /* NFTA_SET_ELEM_LIST_ELEMENTS */
+}
+
+static int fw_nftables_add_masquerade_internal(
+ sd_netlink *nfnl,
+ bool add,
+ int af,
+ const union in_addr_union *source,
+ unsigned int source_prefixlen) {
+
+ _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *m = NULL;
+ int r;
+
+ assert(nfnl);
+ assert(IN_SET(af, AF_INET, AF_INET6));
+
+ if (!source || source_prefixlen == 0)
+ return -EINVAL;
+
+ if (af == AF_INET6 && source_prefixlen < 8)
+ return -EINVAL;
+
+ r = sd_nfnl_nft_message_new_setelems(nfnl, &m, add, af, NFT_SYSTEMD_TABLE_NAME, NFT_SYSTEMD_MASQ_SET_NAME);
+ if (r < 0)
+ return r;
+
+ if (af == AF_INET)
+ r = nft_message_append_setelem_iprange(m, source, source_prefixlen);
+ else
+ r = nft_message_append_setelem_ip6range(m, source, source_prefixlen);
+ if (r < 0)
+ return r;
+
+ return sd_nfnl_call_batch(nfnl, &m, 1, NFNL_DEFAULT_TIMEOUT_USECS, NULL);
+}
+
+int fw_nftables_add_masquerade(
+ FirewallContext *ctx,
+ bool add,
+ int af,
+ const union in_addr_union *source,
+ unsigned int source_prefixlen) {
+
+ int r;
+
+ assert(ctx);
+ assert(ctx->nfnl);
+ assert(IN_SET(af, AF_INET, AF_INET6));
+
+ if (!socket_ipv6_is_supported() && af == AF_INET6)
+ return -EOPNOTSUPP;
+
+ r = fw_nftables_add_masquerade_internal(ctx->nfnl, add, af, source, source_prefixlen);
+ if (r != -ENOENT)
+ return r;
+
+ /* When someone runs 'nft flush ruleset' in the same net namespace this will also tear down the
+ * systemd nat table.
+ *
+ * Unlike iptables -t nat -F (which will remove all rules added by the systemd iptables
+ * backend, iptables has builtin chains that cannot be deleted -- the next add operation will
+ * 'just work'.
+ *
+ * In the nftables case, everything gets removed. The next add operation will yield -ENOENT.
+ *
+ * If we see -ENOENT on add, replay the initial table setup. If that works, re-do the add
+ * operation.
+ *
+ * Note that this doesn't protect against external sabotage such as a
+ * 'while true; nft flush ruleset; done'. There is nothing that could be done about that short
+ * of extending the kernel to allow tables to be owned by stystemd-networkd and making them
+ * non-deleteable except by the 'owning process'. */
+
+ r = fw_nftables_init_family(ctx->nfnl, af);
+ if (r < 0)
+ return r;
+
+ return fw_nftables_add_masquerade_internal(ctx->nfnl, add, af, source, source_prefixlen);
+}
+
+static int fw_nftables_add_local_dnat_internal(
+ sd_netlink *nfnl,
+ bool add,
+ int af,
+ int protocol,
+ uint16_t local_port,
+ const union in_addr_union *remote,
+ uint16_t remote_port,
+ const union in_addr_union *previous_remote) {
+
+ sd_netlink_message *messages[3] = {};
+ _unused_ _cleanup_(netlink_message_unref_manyp) sd_netlink_message **unref = messages;
+ static bool ipv6_supported = true;
+ uint32_t data[5], key[2], dlen;
+ size_t msgcnt = 0;
+ int r;
+
+ assert(nfnl);
+ assert(add || !previous_remote);
+ assert(IN_SET(af, AF_INET, AF_INET6));
+
+ if (!ipv6_supported && af == AF_INET6)
+ return -EOPNOTSUPP;
+
+ if (!IN_SET(protocol, IPPROTO_TCP, IPPROTO_UDP))
+ return -EPROTONOSUPPORT;
+
+ if (local_port <= 0)
+ return -EINVAL;
+
+ key[0] = protocol;
+ key[1] = htobe16(local_port);
+
+ if (!remote)
+ return -EOPNOTSUPP;
+
+ if (remote_port <= 0)
+ return -EINVAL;
+
+ if (af == AF_INET) {
+ dlen = 8;
+ data[1] = htobe16(remote_port);
+ } else {
+ assert(af == AF_INET6);
+ dlen = sizeof(data);
+ data[4] = htobe16(remote_port);
+ }
+
+ /* If a previous remote is set, remove its entry */
+ if (add && previous_remote && !in_addr_equal(af, previous_remote, remote)) {
+ if (af == AF_INET)
+ data[0] = previous_remote->in.s_addr;
+ else
+ memcpy(data, &previous_remote->in6, sizeof(previous_remote->in6));
+
+ r = nft_del_element(nfnl, &messages[msgcnt++], af, NFT_SYSTEMD_DNAT_MAP_NAME, key, sizeof(key), data, dlen);
+ if (r < 0)
+ return r;
+ }
+
+ if (af == AF_INET)
+ data[0] = remote->in.s_addr;
+ else
+ memcpy(data, &remote->in6, sizeof(remote->in6));
+
+ if (add)
+ r = nft_add_element(nfnl, &messages[msgcnt++], af, NFT_SYSTEMD_DNAT_MAP_NAME, key, sizeof(key), data, dlen);
+ else
+ r = nft_del_element(nfnl, &messages[msgcnt++], af, NFT_SYSTEMD_DNAT_MAP_NAME, key, sizeof(key), data, dlen);
+ if (r < 0)
+ return r;
+
+ assert(msgcnt < ELEMENTSOF(messages));
+ r = sd_nfnl_call_batch(nfnl, messages, msgcnt, NFNL_DEFAULT_TIMEOUT_USECS, NULL);
+ if (r == -EOVERFLOW && af == AF_INET6) {
+ /* The current implementation of DNAT in systemd requires kernel's
+ * fdb9c405e35bdc6e305b9b4e20ebc141ed14fc81 (v5.8), and the older kernel returns
+ * -EOVERFLOW. Let's treat the error as -EOPNOTSUPP. */
+ log_debug_errno(r, "The current implementation of IPv6 DNAT in systemd requires kernel 5.8 or newer, ignoring: %m");
+ ipv6_supported = false;
+ return -EOPNOTSUPP;
+ }
+ if (r < 0)
+ return r;
+
+ return 0;
+}
+
+int fw_nftables_add_local_dnat(
+ FirewallContext *ctx,
+ bool add,
+ int af,
+ int protocol,
+ uint16_t local_port,
+ const union in_addr_union *remote,
+ uint16_t remote_port,
+ const union in_addr_union *previous_remote) {
+
+ int r;
+
+ assert(ctx);
+ assert(ctx->nfnl);
+ assert(IN_SET(af, AF_INET, AF_INET6));
+
+ if (!socket_ipv6_is_supported() && af == AF_INET6)
+ return -EOPNOTSUPP;
+
+ r = fw_nftables_add_local_dnat_internal(ctx->nfnl, add, af, protocol, local_port, remote, remote_port, previous_remote);
+ if (r != -ENOENT)
+ return r;
+
+ /* See comment in fw_nftables_add_masquerade(). */
+ r = fw_nftables_init_family(ctx->nfnl, af);
+ if (r < 0)
+ return r;
+
+ /* table created anew; previous address already gone */
+ return fw_nftables_add_local_dnat_internal(ctx->nfnl, add, af, protocol, local_port, remote, remote_port, NULL);
+}