Merge branch 'net: bpf: handle return value of post_bind{4,6} and add selftests for it'

Menglong Dong says:

====================

From: Menglong Dong <imagedong@tencent.com>

The return value of BPF_CGROUP_RUN_PROG_INET{4,6}_POST_BIND() in
__inet_bind() is not handled properly. While the return value
is non-zero, it will set inet_saddr and inet_rcv_saddr to 0 and
exit:

        err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk);
        if (err) {
                inet->inet_saddr = inet->inet_rcv_saddr = 0;
                goto out_release_sock;
        }

Let's take UDP for example and see what will happen. For UDP
socket, it will be added to 'udp_prot.h.udp_table->hash' and
'udp_prot.h.udp_table->hash2' after the sk->sk_prot->get_port()
called success. If 'inet->inet_rcv_saddr' is specified here,
then 'sk' will be in the 'hslot2' of 'hash2' that it don't belong
to (because inet_saddr is changed to 0), and UDP packet received
will not be passed to this sock. If 'inet->inet_rcv_saddr' is not
specified here, the sock will work fine, as it can receive packet
properly, which is wired, as the 'bind()' is already failed.

To undo the get_port() operation, introduce the 'put_port' field
for 'struct proto'. For TCP proto, it is inet_put_port(); For UDP
proto, it is udp_lib_unhash(); For icmp proto, it is
ping_unhash().

Therefore, after sys_bind() fail caused by
BPF_CGROUP_RUN_PROG_INET4_POST_BIND(), it will be unbinded, which
means that it can try to be binded to another port.

The second patch use C99 initializers in test_sock.c

The third patch is the selftests for this modification.

Changes since v4:
- use C99 initializers in test_sock.c before adding the test case

Changes since v3:
- add the third patch which use C99 initializers in test_sock.c

Changes since v2:
- NULL check for sk->sk_prot->put_port

Changes since v1:
- introduce 'put_port' field for 'struct proto'
- add selftests for it
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

include/net/sock.h

@@ -1209,6 +1209,7 @@ struct proto {
 	void			(*unhash)(struct sock *sk);
 	void			(*rehash)(struct sock *sk);
 	int			(*get_port)(struct sock *sk, unsigned short snum);
+	void			(*put_port)(struct sock *sk);
 #ifdef CONFIG_BPF_SYSCALL
 	int			(*psock_update_sk_prot)(struct sock *sk,
 							struct sk_psock *psock,

net/ipv4/af_inet.c

@@ -531,6 +531,8 @@ int __inet_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
 			err = BPF_CGROUP_RUN_PROG_INET4_POST_BIND(sk);
 			if (err) {
 				inet->inet_saddr = inet->inet_rcv_saddr = 0;
+				if (sk->sk_prot->put_port)
+					sk->sk_prot->put_port(sk);
 				goto out_release_sock;
 			}
 		}

net/ipv4/ping.c

@@ -994,6 +994,7 @@ struct proto ping_prot = {
 	.hash =		ping_hash,
 	.unhash =	ping_unhash,
 	.get_port =	ping_get_port,
+	.put_port =	ping_unhash,
 	.obj_size =	sizeof(struct inet_sock),
 };
 EXPORT_SYMBOL(ping_prot);

net/ipv4/tcp_ipv4.c

@@ -3076,6 +3076,7 @@ struct proto tcp_prot = {
 	.hash			= inet_hash,
 	.unhash			= inet_unhash,
 	.get_port		= inet_csk_get_port,
+	.put_port		= inet_put_port,
 #ifdef CONFIG_BPF_SYSCALL
 	.psock_update_sk_prot	= tcp_bpf_update_proto,
 #endif

net/ipv4/udp.c

@@ -2927,6 +2927,7 @@ struct proto udp_prot = {
 	.unhash			= udp_lib_unhash,
 	.rehash			= udp_v4_rehash,
 	.get_port		= udp_v4_get_port,
+	.put_port		= udp_lib_unhash,
 #ifdef CONFIG_BPF_SYSCALL
 	.psock_update_sk_prot	= udp_bpf_update_proto,
 #endif

net/ipv6/af_inet6.c

@@ -413,6 +413,8 @@ static int __inet6_bind(struct sock *sk, struct sockaddr *uaddr, int addr_len,
 			if (err) {
 				sk->sk_ipv6only = saved_ipv6only;
 				inet_reset_saddr(sk);
+				if (sk->sk_prot->put_port)
+					sk->sk_prot->put_port(sk);
 				goto out;
 			}
 		}

net/ipv6/ping.c

@@ -177,6 +177,7 @@ struct proto pingv6_prot = {
 	.hash =		ping_hash,
 	.unhash =	ping_unhash,
 	.get_port =	ping_get_port,
+	.put_port =	ping_unhash,
 	.obj_size =	sizeof(struct raw6_sock),
 };
 EXPORT_SYMBOL_GPL(pingv6_prot);

net/ipv6/tcp_ipv6.c

@@ -2181,6 +2181,7 @@ struct proto tcpv6_prot = {
 	.hash			= inet6_hash,
 	.unhash			= inet_unhash,
 	.get_port		= inet_csk_get_port,
+	.put_port		= inet_put_port,
 #ifdef CONFIG_BPF_SYSCALL
 	.psock_update_sk_prot	= tcp_bpf_update_proto,
 #endif

net/ipv6/udp.c

@@ -1732,6 +1732,7 @@ struct proto udpv6_prot = {
 	.unhash			= udp_lib_unhash,
 	.rehash			= udp_v6_rehash,
 	.get_port		= udp_v6_get_port,
+	.put_port		= udp_lib_unhash,
 #ifdef CONFIG_BPF_SYSCALL
 	.psock_update_sk_prot	= udp_bpf_update_proto,
 #endif

tools/testing/selftests/bpf/test_sock.c

@@ -35,18 +35,21 @@ struct sock_test {
 	/* Endpoint to bind() to */
 	const char *ip;
 	unsigned short port;
+	unsigned short port_retry;
 	/* Expected test result */
 	enum {
 		LOAD_REJECT,
 		ATTACH_REJECT,
 		BIND_REJECT,
 		SUCCESS,
+		RETRY_SUCCESS,
+		RETRY_REJECT
 	} result;
 };
 
 static struct sock_test tests[] = {
 	{
-		"bind4 load with invalid access: src_ip6",
+		.descr = "bind4 load with invalid access: src_ip6",
 		.insns = {
 			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
 			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
@@ -54,16 +57,12 @@ static struct sock_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET4_POST_BIND,
-		BPF_CGROUP_INET4_POST_BIND,
-		0,
-		0,
-		NULL,
-		0,
-		LOAD_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.result = LOAD_REJECT,
 	},
 	{
-		"bind4 load with invalid access: mark",
+		.descr = "bind4 load with invalid access: mark",
 		.insns = {
 			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
 			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
@@ -71,16 +70,12 @@ static struct sock_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET4_POST_BIND,
-		BPF_CGROUP_INET4_POST_BIND,
-		0,
-		0,
-		NULL,
-		0,
-		LOAD_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.result = LOAD_REJECT,
 	},
 	{
-		"bind6 load with invalid access: src_ip4",
+		.descr = "bind6 load with invalid access: src_ip4",
 		.insns = {
 			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
 			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
@@ -88,16 +83,12 @@ static struct sock_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET6_POST_BIND,
-		BPF_CGROUP_INET6_POST_BIND,
-		0,
-		0,
-		NULL,
-		0,
-		LOAD_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.result = LOAD_REJECT,
 	},
 	{
-		"sock_create load with invalid access: src_port",
+		.descr = "sock_create load with invalid access: src_port",
 		.insns = {
 			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
 			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
@@ -105,128 +96,106 @@ static struct sock_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET_SOCK_CREATE,
-		BPF_CGROUP_INET_SOCK_CREATE,
-		0,
-		0,
-		NULL,
-		0,
-		LOAD_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE,
+		.attach_type = BPF_CGROUP_INET_SOCK_CREATE,
+		.result = LOAD_REJECT,
 	},
 	{
-		"sock_create load w/o expected_attach_type (compat mode)",
+		.descr = "sock_create load w/o expected_attach_type (compat mode)",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		0,
-		BPF_CGROUP_INET_SOCK_CREATE,
-		AF_INET,
-		SOCK_STREAM,
-		"127.0.0.1",
-		8097,
-		SUCCESS,
+		.expected_attach_type = 0,
+		.attach_type = BPF_CGROUP_INET_SOCK_CREATE,
+		.domain = AF_INET,
+		.type = SOCK_STREAM,
+		.ip = "127.0.0.1",
+		.port = 8097,
+		.result = SUCCESS,
 	},
 	{
-		"sock_create load w/ expected_attach_type",
+		.descr = "sock_create load w/ expected_attach_type",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET_SOCK_CREATE,
-		BPF_CGROUP_INET_SOCK_CREATE,
-		AF_INET,
-		SOCK_STREAM,
-		"127.0.0.1",
-		8097,
-		SUCCESS,
+		.expected_attach_type = BPF_CGROUP_INET_SOCK_CREATE,
+		.attach_type = BPF_CGROUP_INET_SOCK_CREATE,
+		.domain = AF_INET,
+		.type = SOCK_STREAM,
+		.ip = "127.0.0.1",
+		.port = 8097,
+		.result = SUCCESS,
 	},
 	{
-		"attach type mismatch bind4 vs bind6",
+		.descr = "attach type mismatch bind4 vs bind6",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET4_POST_BIND,
-		BPF_CGROUP_INET6_POST_BIND,
-		0,
-		0,
-		NULL,
-		0,
-		ATTACH_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.result = ATTACH_REJECT,
 	},
 	{
-		"attach type mismatch bind6 vs bind4",
+		.descr = "attach type mismatch bind6 vs bind4",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET6_POST_BIND,
-		BPF_CGROUP_INET4_POST_BIND,
-		0,
-		0,
-		NULL,
-		0,
-		ATTACH_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.result = ATTACH_REJECT,
 	},
 	{
-		"attach type mismatch default vs bind4",
+		.descr = "attach type mismatch default vs bind4",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		0,
-		BPF_CGROUP_INET4_POST_BIND,
-		0,
-		0,
-		NULL,
-		0,
-		ATTACH_REJECT,
+		.expected_attach_type = 0,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.result = ATTACH_REJECT,
 	},
 	{
-		"attach type mismatch bind6 vs sock_create",
+		.descr = "attach type mismatch bind6 vs sock_create",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET6_POST_BIND,
-		BPF_CGROUP_INET_SOCK_CREATE,
-		0,
-		0,
-		NULL,
-		0,
-		ATTACH_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.attach_type = BPF_CGROUP_INET_SOCK_CREATE,
+		.result = ATTACH_REJECT,
 	},
 	{
-		"bind4 reject all",
+		.descr = "bind4 reject all",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 0),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET4_POST_BIND,
-		BPF_CGROUP_INET4_POST_BIND,
-		AF_INET,
-		SOCK_STREAM,
-		"0.0.0.0",
-		0,
-		BIND_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.domain = AF_INET,
+		.type = SOCK_STREAM,
+		.ip = "0.0.0.0",
+		.result = BIND_REJECT,
 	},
 	{
-		"bind6 reject all",
+		.descr = "bind6 reject all",
 		.insns = {
 			BPF_MOV64_IMM(BPF_REG_0, 0),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET6_POST_BIND,
-		BPF_CGROUP_INET6_POST_BIND,
-		AF_INET6,
-		SOCK_STREAM,
-		"::",
-		0,
-		BIND_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.domain = AF_INET6,
+		.type = SOCK_STREAM,
+		.ip = "::",
+		.result = BIND_REJECT,
 	},
 	{
-		"bind6 deny specific IP & port",
+		.descr = "bind6 deny specific IP & port",
 		.insns = {
 			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
 
@@ -247,16 +216,16 @@ static struct sock_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET6_POST_BIND,
-		BPF_CGROUP_INET6_POST_BIND,
-		AF_INET6,
-		SOCK_STREAM,
-		"::1",
-		8193,
-		BIND_REJECT,
+		.expected_attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.domain = AF_INET6,
+		.type = SOCK_STREAM,
+		.ip = "::1",
+		.port = 8193,
+		.result = BIND_REJECT,
 	},
 	{
-		"bind4 allow specific IP & port",
+		.descr = "bind4 allow specific IP & port",
 		.insns = {
 			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
 
@@ -277,41 +246,132 @@ static struct sock_test tests[] = {
 			BPF_MOV64_IMM(BPF_REG_0, 0),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET4_POST_BIND,
-		BPF_CGROUP_INET4_POST_BIND,
-		AF_INET,
-		SOCK_STREAM,
-		"127.0.0.1",
-		4098,
-		SUCCESS,
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.domain = AF_INET,
+		.type = SOCK_STREAM,
+		.ip = "127.0.0.1",
+		.port = 4098,
+		.result = SUCCESS,
 	},
 	{
-		"bind4 allow all",
+		.descr = "bind4 deny specific IP & port of TCP, and retry",
 		.insns = {
+			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+
+			/* if (ip == expected && port == expected) */
+			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+				    offsetof(struct bpf_sock, src_ip4)),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_7,
+				    __bpf_constant_ntohl(0x7F000001), 4),
+			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+				    offsetof(struct bpf_sock, src_port)),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0x1002, 2),
+
+			/* return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_A(1),
+
+			/* else return ALLOW; */
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET4_POST_BIND,
-		BPF_CGROUP_INET4_POST_BIND,
-		AF_INET,
-		SOCK_STREAM,
-		"0.0.0.0",
-		0,
-		SUCCESS,
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.domain = AF_INET,
+		.type = SOCK_STREAM,
+		.ip = "127.0.0.1",
+		.port = 4098,
+		.port_retry = 5000,
+		.result = RETRY_SUCCESS,
 	},
 	{
-		"bind6 allow all",
+		.descr = "bind4 deny specific IP & port of UDP, and retry",
 		.insns = {
+			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+
+			/* if (ip == expected && port == expected) */
+			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+				    offsetof(struct bpf_sock, src_ip4)),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_7,
+				    __bpf_constant_ntohl(0x7F000001), 4),
+			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+				    offsetof(struct bpf_sock, src_port)),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0x1002, 2),
+
+			/* return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_A(1),
+
+			/* else return ALLOW; */
 			BPF_MOV64_IMM(BPF_REG_0, 1),
 			BPF_EXIT_INSN(),
 		},
-		BPF_CGROUP_INET6_POST_BIND,
-		BPF_CGROUP_INET6_POST_BIND,
-		AF_INET6,
-		SOCK_STREAM,
-		"::",
-		0,
-		SUCCESS,
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.domain = AF_INET,
+		.type = SOCK_DGRAM,
+		.ip = "127.0.0.1",
+		.port = 4098,
+		.port_retry = 5000,
+		.result = RETRY_SUCCESS,
+	},
+	{
+		.descr = "bind6 deny specific IP & port, and retry",
+		.insns = {
+			BPF_MOV64_REG(BPF_REG_6, BPF_REG_1),
+
+			/* if (ip == expected && port == expected) */
+			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+				    offsetof(struct bpf_sock, src_ip6[3])),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_7,
+				    __bpf_constant_ntohl(0x00000001), 4),
+			BPF_LDX_MEM(BPF_W, BPF_REG_7, BPF_REG_6,
+				    offsetof(struct bpf_sock, src_port)),
+			BPF_JMP_IMM(BPF_JNE, BPF_REG_7, 0x2001, 2),
+
+			/* return DENY; */
+			BPF_MOV64_IMM(BPF_REG_0, 0),
+			BPF_JMP_A(1),
+
+			/* else return ALLOW; */
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_EXIT_INSN(),
+		},
+		.expected_attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.domain = AF_INET6,
+		.type = SOCK_STREAM,
+		.ip = "::1",
+		.port = 8193,
+		.port_retry = 9000,
+		.result = RETRY_SUCCESS,
+	},
+	{
+		.descr = "bind4 allow all",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_EXIT_INSN(),
+		},
+		.expected_attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.attach_type = BPF_CGROUP_INET4_POST_BIND,
+		.domain = AF_INET,
+		.type = SOCK_STREAM,
+		.ip = "0.0.0.0",
+		.result = SUCCESS,
+	},
+	{
+		.descr = "bind6 allow all",
+		.insns = {
+			BPF_MOV64_IMM(BPF_REG_0, 1),
+			BPF_EXIT_INSN(),
+		},
+		.expected_attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.attach_type = BPF_CGROUP_INET6_POST_BIND,
+		.domain = AF_INET6,
+		.type = SOCK_STREAM,
+		.ip = "::",
+		.result = SUCCESS,
 	},
 };
 
@@ -351,14 +411,15 @@ static int attach_sock_prog(int cgfd, int progfd,
 	return bpf_prog_attach(progfd, cgfd, attach_type, BPF_F_ALLOW_OVERRIDE);
 }
 
-static int bind_sock(int domain, int type, const char *ip, unsigned short port)
+static int bind_sock(int domain, int type, const char *ip,
+		     unsigned short port, unsigned short port_retry)
 {
 	struct sockaddr_storage addr;
 	struct sockaddr_in6 *addr6;
 	struct sockaddr_in *addr4;
 	int sockfd = -1;
 	socklen_t len;
-	int err = 0;
+	int res = SUCCESS;
 
 	sockfd = socket(domain, type, 0);
 	if (sockfd < 0)
@@ -384,21 +445,44 @@ static int bind_sock(int domain, int type, const char *ip, unsigned short port)
 		goto err;
 	}
 
-	if (bind(sockfd, (const struct sockaddr *)&addr, len) == -1)
-		goto err;
+	if (bind(sockfd, (const struct sockaddr *)&addr, len) == -1) {
+		/* sys_bind() may fail for different reasons, errno has to be
+		 * checked to confirm that BPF program rejected it.
+		 */
+		if (errno != EPERM)
+			goto err;
+		if (port_retry)
+			goto retry;
+		res = BIND_REJECT;
+		goto out;
+	}
 
+	goto out;
+retry:
+	if (domain == AF_INET)
+		addr4->sin_port = htons(port_retry);
+	else
+		addr6->sin6_port = htons(port_retry);
+	if (bind(sockfd, (const struct sockaddr *)&addr, len) == -1) {
+		if (errno != EPERM)
+			goto err;
+		res = RETRY_REJECT;
+	} else {
+		res = RETRY_SUCCESS;
+	}
 	goto out;
 err:
-	err = -1;
+	res = -1;
 out:
 	close(sockfd);
-	return err;
+	return res;
 }
 
 static int run_test_case(int cgfd, const struct sock_test *test)
 {
 	int progfd = -1;
 	int err = 0;
+	int res;
 
 	printf("Test case: %s .. ", test->descr);
 	progfd = load_sock_prog(test->insns, test->expected_attach_type);
@@ -416,21 +500,11 @@ static int run_test_case(int cgfd, const struct sock_test *test)
 			goto err;
 	}
 
-	if (bind_sock(test->domain, test->type, test->ip, test->port) == -1) {
-		/* sys_bind() may fail for different reasons, errno has to be
-		 * checked to confirm that BPF program rejected it.
-		 */
-		if (test->result == BIND_REJECT && errno == EPERM)
-			goto out;
-		else
-			goto err;
-	}
-
+	res = bind_sock(test->domain, test->type, test->ip, test->port,
+			test->port_retry);
+	if (res > 0 && test->result == res)
+		goto out;
 
-	if (test->result != SUCCESS)
-		goto err;
-
-	goto out;
 err:
 	err = -1;
 out: