selftests/bpf: Selftest for sys_sendmsg hooks

Add selftest for BPF_CGROUP_UDP4_SENDMSG and BPF_CGROUP_UDP6_SENDMSG
attach types.

Try to sendmsg(2) to specific IP:port and test that:
* source IP is overridden as expected.
* remote IP:port pair is overridden as expected;

Both UDPv4 and UDPv6 are tested.

Output:
  # test_sock_addr.sh 2>/dev/null
  Wait for testing IPv4/IPv6 to become available ... OK
  ... pre-existing test-cases skipped ...
  Test case: sendmsg4: load prog with wrong expected attach type .. [PASS]
  Test case: sendmsg4: attach prog with wrong attach type .. [PASS]
  Test case: sendmsg4: rewrite IP & port (asm) .. [PASS]
  Test case: sendmsg4: rewrite IP & port (C) .. [PASS]
  Test case: sendmsg4: deny call .. [PASS]
  Test case: sendmsg6: load prog with wrong expected attach type .. [PASS]
  Test case: sendmsg6: attach prog with wrong attach type .. [PASS]
  Test case: sendmsg6: rewrite IP & port (asm) .. [PASS]
  Test case: sendmsg6: rewrite IP & port (C) .. [PASS]
  Test case: sendmsg6: IPv4-mapped IPv6 .. [PASS]
  Test case: sendmsg6: deny call .. [PASS]
  Summary: 27 PASSED, 0 FAILED
Signed-off-by: Andrey Ignatov <rdna@fb.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/Makefile

@@ -34,7 +34,7 @@ TEST_GEN_FILES = test_pkt_access.o test_xdp.o test_l4lb.o test_tcp_estats.o test
 	sockmap_tcp_msg_prog.o connect4_prog.o connect6_prog.o test_adjust_tail.o \
 	test_btf_haskv.o test_btf_nokv.o test_sockmap_kern.o test_tunnel_kern.o \
 	test_get_stack_rawtp.o test_sockmap_kern.o test_sockhash_kern.o \
-	test_lwt_seg6local.o
+	test_lwt_seg6local.o sendmsg4_prog.o sendmsg6_prog.o
 
 # Order correspond to 'make run_tests' order
 TEST_PROGS := test_kmod.sh \

tools/testing/selftests/bpf/sendmsg4_prog.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <sys/socket.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define SRC1_IP4		0xAC100001U /* 172.16.0.1 */
+#define SRC2_IP4		0x00000000U
+#define SRC_REWRITE_IP4		0x7f000004U
+#define DST_IP4			0xC0A801FEU /* 192.168.1.254 */
+#define DST_REWRITE_IP4		0x7f000001U
+#define DST_PORT		4040
+#define DST_REWRITE_PORT4	4444
+
+int _version SEC("version") = 1;
+
+SEC("cgroup/sendmsg4")
+int sendmsg_v4_prog(struct bpf_sock_addr *ctx)
+{
+	if (ctx->type != SOCK_DGRAM)
+		return 0;
+
+	/* Rewrite source. */
+	if (ctx->msg_src_ip4 == bpf_htonl(SRC1_IP4) ||
+	    ctx->msg_src_ip4 == bpf_htonl(SRC2_IP4)) {
+		ctx->msg_src_ip4 = bpf_htonl(SRC_REWRITE_IP4);
+	} else {
+		/* Unexpected source. Reject sendmsg. */
+		return 0;
+	}
+
+	/* Rewrite destination. */
+	if ((ctx->user_ip4 >> 24) == (bpf_htonl(DST_IP4) >> 24) &&
+	     ctx->user_port == bpf_htons(DST_PORT)) {
+		ctx->user_ip4 = bpf_htonl(DST_REWRITE_IP4);
+		ctx->user_port = bpf_htons(DST_REWRITE_PORT4);
+	} else {
+		/* Unexpected source. Reject sendmsg. */
+		return 0;
+	}
+
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/sendmsg6_prog.c

+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Facebook
+
+#include <linux/stddef.h>
+#include <linux/bpf.h>
+#include <sys/socket.h>
+
+#include "bpf_helpers.h"
+#include "bpf_endian.h"
+
+#define SRC_REWRITE_IP6_0	0
+#define SRC_REWRITE_IP6_1	0
+#define SRC_REWRITE_IP6_2	0
+#define SRC_REWRITE_IP6_3	6
+
+#define DST_REWRITE_IP6_0	0
+#define DST_REWRITE_IP6_1	0
+#define DST_REWRITE_IP6_2	0
+#define DST_REWRITE_IP6_3	1
+
+#define DST_REWRITE_PORT6	6666
+
+int _version SEC("version") = 1;
+
+SEC("cgroup/sendmsg6")
+int sendmsg_v6_prog(struct bpf_sock_addr *ctx)
+{
+	if (ctx->type != SOCK_DGRAM)
+		return 0;
+
+	/* Rewrite source. */
+	if (ctx->msg_src_ip6[3] == bpf_htonl(1) ||
+	    ctx->msg_src_ip6[3] == bpf_htonl(0)) {
+		ctx->msg_src_ip6[0] = bpf_htonl(SRC_REWRITE_IP6_0);
+		ctx->msg_src_ip6[1] = bpf_htonl(SRC_REWRITE_IP6_1);
+		ctx->msg_src_ip6[2] = bpf_htonl(SRC_REWRITE_IP6_2);
+		ctx->msg_src_ip6[3] = bpf_htonl(SRC_REWRITE_IP6_3);
+	} else {
+		/* Unexpected source. Reject sendmsg. */
+		return 0;
+	}
+
+	/* Rewrite destination. */
+	if ((ctx->user_ip6[0] & 0xFFFF) == bpf_htons(0xFACE) &&
+	     ctx->user_ip6[0] >> 16 == bpf_htons(0xB00C)) {
+		ctx->user_ip6[0] = bpf_htonl(DST_REWRITE_IP6_0);
+		ctx->user_ip6[1] = bpf_htonl(DST_REWRITE_IP6_1);
+		ctx->user_ip6[2] = bpf_htonl(DST_REWRITE_IP6_2);
+		ctx->user_ip6[3] = bpf_htonl(DST_REWRITE_IP6_3);
+
+		ctx->user_port = bpf_htons(DST_REWRITE_PORT6);
+	} else {
+		/* Unexpected destination. Reject sendmsg. */
+		return 0;
+	}
+
+	return 1;
+}
+
+char _license[] SEC("license") = "GPL";

tools/testing/selftests/bpf/test_sock_addr.c

 // SPDX-License-Identifier: GPL-2.0
 // Copyright (c) 2018 Facebook
 
+#define _GNU_SOURCE
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
 
 #include <arpa/inet.h>
+#include <netinet/in.h>
 #include <sys/types.h>
+#include <sys/select.h>
 #include <sys/socket.h>
 
 #include <linux/filter.h>
@@ -17,6 +21,10 @@
 #include "cgroup_helpers.h"
 #include "bpf_rlimit.h"
 
+#ifndef ENOTSUPP
+# define ENOTSUPP 524
+#endif
+
 #ifndef ARRAY_SIZE
 # define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
 #endif
@@ -24,15 +32,20 @@
 #define CG_PATH	"/foo"
 #define CONNECT4_PROG_PATH	"./connect4_prog.o"
 #define CONNECT6_PROG_PATH	"./connect6_prog.o"
+#define SENDMSG4_PROG_PATH	"./sendmsg4_prog.o"
+#define SENDMSG6_PROG_PATH	"./sendmsg6_prog.o"
 
 #define SERV4_IP		"192.168.1.254"
 #define SERV4_REWRITE_IP	"127.0.0.1"
+#define SRC4_IP			"172.16.0.1"
 #define SRC4_REWRITE_IP		"127.0.0.4"
 #define SERV4_PORT		4040
 #define SERV4_REWRITE_PORT	4444
 
 #define SERV6_IP		"face:b00c:1234:5678::abcd"
 #define SERV6_REWRITE_IP	"::1"
+#define SERV6_V4MAPPED_IP	"::ffff:192.168.0.4"
+#define SRC6_IP			"::1"
 #define SRC6_REWRITE_IP		"::6"
 #define SERV6_PORT		6060
 #define SERV6_REWRITE_PORT	6666
@@ -65,6 +78,8 @@ struct sock_addr_test {
 	enum {
 		LOAD_REJECT,
 		ATTACH_REJECT,
+		SYSCALL_EPERM,
+		SYSCALL_ENOTSUPP,
 		SUCCESS,
 	} expected_result;
 };
@@ -73,6 +88,12 @@ static int bind4_prog_load(const struct sock_addr_test *test);
 static int bind6_prog_load(const struct sock_addr_test *test);
 static int connect4_prog_load(const struct sock_addr_test *test);
 static int connect6_prog_load(const struct sock_addr_test *test);
+static int sendmsg_deny_prog_load(const struct sock_addr_test *test);
+static int sendmsg4_rw_asm_prog_load(const struct sock_addr_test *test);
+static int sendmsg4_rw_c_prog_load(const struct sock_addr_test *test);
+static int sendmsg6_rw_asm_prog_load(const struct sock_addr_test *test);
+static int sendmsg6_rw_c_prog_load(const struct sock_addr_test *test);
+static int sendmsg6_rw_v4mapped_prog_load(const struct sock_addr_test *test);
 
 static struct sock_addr_test tests[] = {
 	/* bind */
@@ -302,6 +323,162 @@ static struct sock_addr_test tests[] = {
 		SRC6_REWRITE_IP,
 		SUCCESS,
 	},
+
+	/* sendmsg */
+	{
+		"sendmsg4: load prog with wrong expected attach type",
+		sendmsg4_rw_asm_prog_load,
+		BPF_CGROUP_UDP6_SENDMSG,
+		BPF_CGROUP_UDP4_SENDMSG,
+		AF_INET,
+		SOCK_DGRAM,
+		NULL,
+		0,
+		NULL,
+		0,
+		NULL,
+		LOAD_REJECT,
+	},
+	{
+		"sendmsg4: attach prog with wrong attach type",
+		sendmsg4_rw_asm_prog_load,
+		BPF_CGROUP_UDP4_SENDMSG,
+		BPF_CGROUP_UDP6_SENDMSG,
+		AF_INET,
+		SOCK_DGRAM,
+		NULL,
+		0,
+		NULL,
+		0,
+		NULL,
+		ATTACH_REJECT,
+	},
+	{
+		"sendmsg4: rewrite IP & port (asm)",
+		sendmsg4_rw_asm_prog_load,
+		BPF_CGROUP_UDP4_SENDMSG,
+		BPF_CGROUP_UDP4_SENDMSG,
+		AF_INET,
+		SOCK_DGRAM,
+		SERV4_IP,
+		SERV4_PORT,
+		SERV4_REWRITE_IP,
+		SERV4_REWRITE_PORT,
+		SRC4_REWRITE_IP,
+		SUCCESS,
+	},
+	{
+		"sendmsg4: rewrite IP & port (C)",
+		sendmsg4_rw_c_prog_load,
+		BPF_CGROUP_UDP4_SENDMSG,
+		BPF_CGROUP_UDP4_SENDMSG,
+		AF_INET,
+		SOCK_DGRAM,
+		SERV4_IP,
+		SERV4_PORT,
+		SERV4_REWRITE_IP,
+		SERV4_REWRITE_PORT,
+		SRC4_REWRITE_IP,
+		SUCCESS,
+	},
+	{
+		"sendmsg4: deny call",
+		sendmsg_deny_prog_load,
+		BPF_CGROUP_UDP4_SENDMSG,
+		BPF_CGROUP_UDP4_SENDMSG,
+		AF_INET,
+		SOCK_DGRAM,
+		SERV4_IP,
+		SERV4_PORT,
+		SERV4_REWRITE_IP,
+		SERV4_REWRITE_PORT,
+		SRC4_REWRITE_IP,
+		SYSCALL_EPERM,
+	},
+	{
+		"sendmsg6: load prog with wrong expected attach type",
+		sendmsg6_rw_asm_prog_load,
+		BPF_CGROUP_UDP4_SENDMSG,
+		BPF_CGROUP_UDP6_SENDMSG,
+		AF_INET6,
+		SOCK_DGRAM,
+		NULL,
+		0,
+		NULL,
+		0,
+		NULL,
+		LOAD_REJECT,
+	},
+	{
+		"sendmsg6: attach prog with wrong attach type",
+		sendmsg6_rw_asm_prog_load,
+		BPF_CGROUP_UDP6_SENDMSG,
+		BPF_CGROUP_UDP4_SENDMSG,
+		AF_INET6,
+		SOCK_DGRAM,
+		NULL,
+		0,
+		NULL,
+		0,
+		NULL,
+		ATTACH_REJECT,
+	},
+	{
+		"sendmsg6: rewrite IP & port (asm)",
+		sendmsg6_rw_asm_prog_load,
+		BPF_CGROUP_UDP6_SENDMSG,
+		BPF_CGROUP_UDP6_SENDMSG,
+		AF_INET6,
+		SOCK_DGRAM,
+		SERV6_IP,
+		SERV6_PORT,
+		SERV6_REWRITE_IP,
+		SERV6_REWRITE_PORT,
+		SRC6_REWRITE_IP,
+		SUCCESS,
+	},
+	{
+		"sendmsg6: rewrite IP & port (C)",
+		sendmsg6_rw_c_prog_load,
+		BPF_CGROUP_UDP6_SENDMSG,
+		BPF_CGROUP_UDP6_SENDMSG,
+		AF_INET6,
+		SOCK_DGRAM,
+		SERV6_IP,
+		SERV6_PORT,
+		SERV6_REWRITE_IP,
+		SERV6_REWRITE_PORT,
+		SRC6_REWRITE_IP,
+		SUCCESS,
+	},
+	{
+		"sendmsg6: IPv4-mapped IPv6",
+		sendmsg6_rw_v4mapped_prog_load,
+		BPF_CGROUP_UDP6_SENDMSG,
+		BPF_CGROUP_UDP6_SENDMSG,
+		AF_INET6,
+		SOCK_DGRAM,
+		SERV6_IP,
+		SERV6_PORT,
+		SERV6_REWRITE_IP,
+		SERV6_REWRITE_PORT,
+		SRC6_REWRITE_IP,
+		SYSCALL_ENOTSUPP,
+	},
+	{
+		"sendmsg6: deny call",
+		sendmsg_deny_prog_load,
+		BPF_CGROUP_UDP6_SENDMSG,
+		BPF_CGROUP_UDP6_SENDMSG,
+		AF_INET6,
+		SOCK_DGRAM,
+		SERV6_IP,
+		SERV6_PORT,
+		SERV6_REWRITE_IP,
+		SERV6_REWRITE_PORT,
+		SRC6_REWRITE_IP,
+		SYSCALL_EPERM,
+	},
 };
 
 static int mk_sockaddr(int domain, const char *ip, unsigned short port,
@@ -540,6 +717,141 @@ static int connect6_prog_load(const struct sock_addr_test *test)
 	return load_path(test, CONNECT6_PROG_PATH);
 }
 
+static int sendmsg_deny_prog_load(const struct sock_addr_test *test)
+{
+	struct bpf_insn insns[] = {
+		/* return 0 */
+		BPF_MOV64_IMM(BPF_REG_0, 0),
+		BPF_EXIT_INSN(),
+	};
+	return load_insns(test, insns, sizeof(insns) / sizeof(struct bpf_insn));
+}
+
+static int sendmsg4_rw_asm_prog_load(const struct sock_addr_test *test)
+{
+	struct sockaddr_in dst4_rw_addr;
+	struct in_addr src4_rw_ip;
+
+	if (inet_pton(AF_INET, SRC4_REWRITE_IP, (void *)&src4_rw_ip) != 1) {
+		log_err("Invalid IPv4: %s", SRC4_REWRITE_IP);
+		return -1;
+	}
+
+	if (mk_sockaddr(AF_INET, SERV4_REWRITE_IP, SERV4_REWRITE_PORT,
+			(struct sockaddr *)&dst4_rw_addr,
+			sizeof(dst4_rw_addr)) == -1)
+		return -1;
+
+	struct bpf_insn insns[] = {
+		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+
+		/* if (sk.family == AF_INET && */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, family)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, AF_INET, 8),
+
+		/*     sk.type == SOCK_DGRAM)  { */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, type)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, SOCK_DGRAM, 6),
+
+		/*      msg_src_ip4 = src4_rw_ip */
+		BPF_MOV32_IMM(BPF_REG_7, src4_rw_ip.s_addr),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,
+			    offsetof(struct bpf_sock_addr, msg_src_ip4)),
+
+		/*      user_ip4 = dst4_rw_addr.sin_addr */
+		BPF_MOV32_IMM(BPF_REG_7, dst4_rw_addr.sin_addr.s_addr),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,
+			    offsetof(struct bpf_sock_addr, user_ip4)),
+
+		/*      user_port = dst4_rw_addr.sin_port */
+		BPF_MOV32_IMM(BPF_REG_7, dst4_rw_addr.sin_port),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,
+			    offsetof(struct bpf_sock_addr, user_port)),
+		/* } */
+
+		/* return 1 */
+		BPF_MOV64_IMM(BPF_REG_0, 1),
+		BPF_EXIT_INSN(),
+	};
+
+	return load_insns(test, insns, sizeof(insns) / sizeof(struct bpf_insn));
+}
+
+static int sendmsg4_rw_c_prog_load(const struct sock_addr_test *test)
+{
+	return load_path(test, SENDMSG4_PROG_PATH);
+}
+
+static int sendmsg6_rw_dst_asm_prog_load(const struct sock_addr_test *test,
+					 const char *rw_dst_ip)
+{
+	struct sockaddr_in6 dst6_rw_addr;
+	struct in6_addr src6_rw_ip;
+
+	if (inet_pton(AF_INET6, SRC6_REWRITE_IP, (void *)&src6_rw_ip) != 1) {
+		log_err("Invalid IPv6: %s", SRC6_REWRITE_IP);
+		return -1;
+	}
+
+	if (mk_sockaddr(AF_INET6, rw_dst_ip, SERV6_REWRITE_PORT,
+			(struct sockaddr *)&dst6_rw_addr,
+			sizeof(dst6_rw_addr)) == -1)
+		return -1;
+
+	struct bpf_insn insns[] = {
+		BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+
+		/* if (sk.family == AF_INET6) { */
+		BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+			    offsetof(struct bpf_sock_addr, family)),
+		BPF_JMP_IMM(BPF_JNE, BPF_REG_7, AF_INET6, 18),
+
+#define STORE_IPV6_WORD_N(DST, SRC, N)					       \
+		BPF_MOV32_IMM(BPF_REG_7, SRC[N]),			       \
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,		       \
+			    offsetof(struct bpf_sock_addr, DST[N]))
+
+#define STORE_IPV6(DST, SRC)						       \
+		STORE_IPV6_WORD_N(DST, SRC, 0),				       \
+		STORE_IPV6_WORD_N(DST, SRC, 1),				       \
+		STORE_IPV6_WORD_N(DST, SRC, 2),				       \
+		STORE_IPV6_WORD_N(DST, SRC, 3)
+
+		STORE_IPV6(msg_src_ip6, src6_rw_ip.s6_addr32),
+		STORE_IPV6(user_ip6, dst6_rw_addr.sin6_addr.s6_addr32),
+
+		/*      user_port = dst6_rw_addr.sin6_port */
+		BPF_MOV32_IMM(BPF_REG_7, dst6_rw_addr.sin6_port),
+		BPF_STX_MEM(BPF_W, BPF_REG_6, BPF_REG_7,
+			    offsetof(struct bpf_sock_addr, user_port)),
+
+		/* } */
+
+		/* return 1 */
+		BPF_MOV64_IMM(BPF_REG_0, 1),
+		BPF_EXIT_INSN(),
+	};
+
+	return load_insns(test, insns, sizeof(insns) / sizeof(struct bpf_insn));
+}
+
+static int sendmsg6_rw_asm_prog_load(const struct sock_addr_test *test)
+{
+	return sendmsg6_rw_dst_asm_prog_load(test, SERV6_REWRITE_IP);
+}
+
+static int sendmsg6_rw_v4mapped_prog_load(const struct sock_addr_test *test)
+{
+	return sendmsg6_rw_dst_asm_prog_load(test, SERV6_V4MAPPED_IP);
+}
+
+static int sendmsg6_rw_c_prog_load(const struct sock_addr_test *test)
+{
+	return load_path(test, SENDMSG6_PROG_PATH);
+}
+
 static int cmp_addr(const struct sockaddr_storage *addr1,
 		    const struct sockaddr_storage *addr2, int cmp_port)
 {
@@ -656,6 +968,135 @@ static int connect_to_server(int type, const struct sockaddr_storage *addr,
 	return fd;
 }
 
+int init_pktinfo(int domain, struct cmsghdr *cmsg)
+{
+	struct in6_pktinfo *pktinfo6;
+	struct in_pktinfo *pktinfo4;
+
+	if (domain == AF_INET) {
+		cmsg->cmsg_level = SOL_IP;
+		cmsg->cmsg_type = IP_PKTINFO;
+		cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_pktinfo));
+		pktinfo4 = (struct in_pktinfo *)CMSG_DATA(cmsg);
+		memset(pktinfo4, 0, sizeof(struct in_pktinfo));
+		if (inet_pton(domain, SRC4_IP,
+			      (void *)&pktinfo4->ipi_spec_dst) != 1)
+			return -1;
+	} else if (domain == AF_INET6) {
+		cmsg->cmsg_level = SOL_IPV6;
+		cmsg->cmsg_type = IPV6_PKTINFO;
+		cmsg->cmsg_len = CMSG_LEN(sizeof(struct in6_pktinfo));
+		pktinfo6 = (struct in6_pktinfo *)CMSG_DATA(cmsg);
+		memset(pktinfo6, 0, sizeof(struct in6_pktinfo));
+		if (inet_pton(domain, SRC6_IP,
+			      (void *)&pktinfo6->ipi6_addr) != 1)
+			return -1;
+	} else {
+		return -1;
+	}
+
+	return 0;
+}
+
+static int sendmsg_to_server(const struct sockaddr_storage *addr,
+			     socklen_t addr_len, int set_cmsg, int *syscall_err)
+{
+	union {
+		char buf[CMSG_SPACE(sizeof(struct in6_pktinfo))];
+		struct cmsghdr align;
+	} control6;
+	union {
+		char buf[CMSG_SPACE(sizeof(struct in_pktinfo))];
+		struct cmsghdr align;
+	} control4;
+	struct msghdr hdr;
+	struct iovec iov;
+	char data = 'a';
+	int domain;
+	int fd = -1;
+
+	domain = addr->ss_family;
+
+	if (domain != AF_INET && domain != AF_INET6) {
+		log_err("Unsupported address family");
+		goto err;
+	}
+
+	fd = socket(domain, SOCK_DGRAM, 0);
+	if (fd == -1) {
+		log_err("Failed to create client socket");
+		goto err;
+	}
+
+	memset(&iov, 0, sizeof(iov));
+	iov.iov_base = &data;
+	iov.iov_len = sizeof(data);
+
+	memset(&hdr, 0, sizeof(hdr));
+	hdr.msg_name = (void *)addr;
+	hdr.msg_namelen = addr_len;
+	hdr.msg_iov = &iov;
+	hdr.msg_iovlen = 1;
+
+	if (set_cmsg) {
+		if (domain == AF_INET) {
+			hdr.msg_control = &control4;
+			hdr.msg_controllen = sizeof(control4.buf);
+		} else if (domain == AF_INET6) {
+			hdr.msg_control = &control6;
+			hdr.msg_controllen = sizeof(control6.buf);
+		}
+		if (init_pktinfo(domain, CMSG_FIRSTHDR(&hdr))) {
+			log_err("Fail to init pktinfo");
+			goto err;
+		}
+	}
+
+	if (sendmsg(fd, &hdr, 0) != sizeof(data)) {
+		log_err("Fail to send message to server");
+		*syscall_err = errno;
+		goto err;
+	}
+
+	goto out;
+err:
+	close(fd);
+	fd = -1;
+out:
+	return fd;
+}
+
+static int recvmsg_from_client(int sockfd, struct sockaddr_storage *src_addr)
+{
+	struct timeval tv;
+	struct msghdr hdr;
+	struct iovec iov;
+	char data[64];
+	fd_set rfds;
+
+	FD_ZERO(&rfds);
+	FD_SET(sockfd, &rfds);
+
+	tv.tv_sec = 2;
+	tv.tv_usec = 0;
+
+	if (select(sockfd + 1, &rfds, NULL, NULL, &tv) <= 0 ||
+	    !FD_ISSET(sockfd, &rfds))
+		return -1;
+
+	memset(&iov, 0, sizeof(iov));
+	iov.iov_base = data;
+	iov.iov_len = sizeof(data);
+
+	memset(&hdr, 0, sizeof(hdr));
+	hdr.msg_name = src_addr;
+	hdr.msg_namelen = sizeof(struct sockaddr_storage);
+	hdr.msg_iov = &iov;
+	hdr.msg_iovlen = 1;
+
+	return recvmsg(sockfd, &hdr, 0);
+}
+
 static int init_addrs(const struct sock_addr_test *test,
 		      struct sockaddr_storage *requested_addr,
 		      struct sockaddr_storage *expected_addr,
@@ -753,6 +1194,69 @@ static int run_connect_test_case(const struct sock_addr_test *test)
 	return err;
 }
 
+static int run_sendmsg_test_case(const struct sock_addr_test *test)
+{
+	socklen_t addr_len = sizeof(struct sockaddr_storage);
+	struct sockaddr_storage expected_src_addr;
+	struct sockaddr_storage requested_addr;
+	struct sockaddr_storage expected_addr;
+	struct sockaddr_storage real_src_addr;
+	int clientfd = -1;
+	int servfd = -1;
+	int set_cmsg;
+	int err = 0;
+
+	if (test->type != SOCK_DGRAM)
+		goto err;
+
+	if (init_addrs(test, &requested_addr, &expected_addr,
+		       &expected_src_addr))
+		goto err;
+
+	/* Prepare server to sendmsg to */
+	servfd = start_server(test->type, &expected_addr, addr_len);
+	if (servfd == -1)
+		goto err;
+
+	for (set_cmsg = 0; set_cmsg <= 1; ++set_cmsg) {
+		if (clientfd >= 0)
+			close(clientfd);
+
+		clientfd = sendmsg_to_server(&requested_addr, addr_len,
+					     set_cmsg, &err);
+		if (err)
+			goto out;
+		else if (clientfd == -1)
+			goto err;
+
+		/* Try to receive message on server instead of using
+		 * getpeername(2) on client socket, to check that client's
+		 * destination address was rewritten properly, since
+		 * getpeername(2) doesn't work with unconnected datagram
+		 * sockets.
+		 *
+		 * Get source address from recvmsg(2) as well to make sure
+		 * source was rewritten properly: getsockname(2) can't be used
+		 * since socket is unconnected and source defined for one
+		 * specific packet may differ from the one used by default and
+		 * returned by getsockname(2).
+		 */
+		if (recvmsg_from_client(servfd, &real_src_addr) == -1)
+			goto err;
+
+		if (cmp_addr(&real_src_addr, &expected_src_addr, /*cmp_port*/0))
+			goto err;
+	}
+
+	goto out;
+err:
+	err = -1;
+out:
+	close(clientfd);
+	close(servfd);
+	return err;
+}
+
 static int run_test_case(int cgfd, const struct sock_addr_test *test)
 {
 	int progfd = -1;
@@ -784,10 +1288,24 @@ static int run_test_case(int cgfd, const struct sock_addr_test *test)
 	case BPF_CGROUP_INET6_CONNECT:
 		err = run_connect_test_case(test);
 		break;
+	case BPF_CGROUP_UDP4_SENDMSG:
+	case BPF_CGROUP_UDP6_SENDMSG:
+		err = run_sendmsg_test_case(test);
+		break;
 	default:
 		goto err;
 	}
 
+	if (test->expected_result == SYSCALL_EPERM && err == EPERM) {
+		err = 0; /* error was expected, reset it */
+		goto out;
+	}
+
+	if (test->expected_result == SYSCALL_ENOTSUPP && err == ENOTSUPP) {
+		err = 0; /* error was expected, reset it */
+		goto out;
+	}
+
 	if (err || test->expected_result != SUCCESS)
 		goto err;