bpf, sockmap: Build helper to create connected socket pair

A common operation for testing is to spin up a pair of sockets that are
connected. Then we can use these to run specific tests that need to
send data, check BPF programs and so on.

The sockmap_listen programs already have this logic lets move it into
the new sockmap_helpers header file for general use.
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20230523025618.113937-11-john.fastabend@gmail.com

tools/testing/selftests/bpf/prog_tests/sockmap_helpers.h

@@ -269,4 +269,122 @@ static inline struct sockaddr *sockaddr(struct sockaddr_storage *ss)
 	return (struct sockaddr *)ss;
 }
 
+static inline int add_to_sockmap(int sock_mapfd, int fd1, int fd2)
+{
+	u64 value;
+	u32 key;
+	int err;
+
+	key = 0;
+	value = fd1;
+	err = xbpf_map_update_elem(sock_mapfd, &key, &value, BPF_NOEXIST);
+	if (err)
+		return err;
+
+	key = 1;
+	value = fd2;
+	return xbpf_map_update_elem(sock_mapfd, &key, &value, BPF_NOEXIST);
+}
+
+static inline int create_pair(int s, int family, int sotype, int *c, int *p)
+{
+	struct sockaddr_storage addr;
+	socklen_t len;
+	int err = 0;
+
+	len = sizeof(addr);
+	err = xgetsockname(s, sockaddr(&addr), &len);
+	if (err)
+		return err;
+
+	*c = xsocket(family, sotype, 0);
+	if (*c < 0)
+		return errno;
+	err = xconnect(*c, sockaddr(&addr), len);
+	if (err) {
+		err = errno;
+		goto close_cli0;
+	}
+
+	*p = xaccept_nonblock(s, NULL, NULL);
+	if (*p < 0) {
+		err = errno;
+		goto close_cli0;
+	}
+	return err;
+close_cli0:
+	close(*c);
+	return err;
+}
+
+static inline int create_socket_pairs(int s, int family, int sotype,
+				      int *c0, int *c1, int *p0, int *p1)
+{
+	int err;
+
+	err = create_pair(s, family, sotype, c0, p0);
+	if (err)
+		return err;
+
+	err = create_pair(s, family, sotype, c1, p1);
+	if (err) {
+		close(*c0);
+		close(*p0);
+	}
+	return err;
+}
+
+static inline int enable_reuseport(int s, int progfd)
+{
+	int err, one = 1;
+
+	err = xsetsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
+	if (err)
+		return -1;
+	err = xsetsockopt(s, SOL_SOCKET, SO_ATTACH_REUSEPORT_EBPF, &progfd,
+			  sizeof(progfd));
+	if (err)
+		return -1;
+
+	return 0;
+}
+
+static inline int socket_loopback_reuseport(int family, int sotype, int progfd)
+{
+	struct sockaddr_storage addr;
+	socklen_t len;
+	int err, s;
+
+	init_addr_loopback(family, &addr, &len);
+
+	s = xsocket(family, sotype, 0);
+	if (s == -1)
+		return -1;
+
+	if (progfd >= 0)
+		enable_reuseport(s, progfd);
+
+	err = xbind(s, sockaddr(&addr), len);
+	if (err)
+		goto close;
+
+	if (sotype & SOCK_DGRAM)
+		return s;
+
+	err = xlisten(s, SOMAXCONN);
+	if (err)
+		goto close;
+
+	return s;
+close:
+	xclose(s);
+	return -1;
+}
+
+static inline int socket_loopback(int family, int sotype)
+{
+	return socket_loopback_reuseport(family, sotype, -1);
+}
+
+
 #endif // __SOCKMAP_HELPERS__

tools/testing/selftests/bpf/prog_tests/sockmap_listen.c

@@ -29,58 +29,6 @@
 
 #include "sockmap_helpers.h"
 
-static int enable_reuseport(int s, int progfd)
-{
-	int err, one = 1;
-
-	err = xsetsockopt(s, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one));
-	if (err)
-		return -1;
-	err = xsetsockopt(s, SOL_SOCKET, SO_ATTACH_REUSEPORT_EBPF, &progfd,
-			  sizeof(progfd));
-	if (err)
-		return -1;
-
-	return 0;
-}
-
-static int socket_loopback_reuseport(int family, int sotype, int progfd)
-{
-	struct sockaddr_storage addr;
-	socklen_t len;
-	int err, s;
-
-	init_addr_loopback(family, &addr, &len);
-
-	s = xsocket(family, sotype, 0);
-	if (s == -1)
-		return -1;
-
-	if (progfd >= 0)
-		enable_reuseport(s, progfd);
-
-	err = xbind(s, sockaddr(&addr), len);
-	if (err)
-		goto close;
-
-	if (sotype & SOCK_DGRAM)
-		return s;
-
-	err = xlisten(s, SOMAXCONN);
-	if (err)
-		goto close;
-
-	return s;
-close:
-	xclose(s);
-	return -1;
-}
-
-static int socket_loopback(int family, int sotype)
-{
-	return socket_loopback_reuseport(family, sotype, -1);
-}
-
 static void test_insert_invalid(struct test_sockmap_listen *skel __always_unused,
 				int family, int sotype, int mapfd)
 {
@@ -723,31 +671,12 @@ static const char *redir_mode_str(enum redir_mode mode)
 	}
 }
 
-static int add_to_sockmap(int sock_mapfd, int fd1, int fd2)
-{
-	u64 value;
-	u32 key;
-	int err;
-
-	key = 0;
-	value = fd1;
-	err = xbpf_map_update_elem(sock_mapfd, &key, &value, BPF_NOEXIST);
-	if (err)
-		return err;
-
-	key = 1;
-	value = fd2;
-	return xbpf_map_update_elem(sock_mapfd, &key, &value, BPF_NOEXIST);
-}
-
 static void redir_to_connected(int family, int sotype, int sock_mapfd,
 			       int verd_mapfd, enum redir_mode mode)
 {
 	const char *log_prefix = redir_mode_str(mode);
-	struct sockaddr_storage addr;
 	int s, c0, c1, p0, p1;
 	unsigned int pass;
-	socklen_t len;
 	int err, n;
 	u32 key;
 	char b;
@@ -758,36 +687,13 @@ static void redir_to_connected(int family, int sotype, int sock_mapfd,
 	if (s < 0)
 		return;
 
-	len = sizeof(addr);
-	err = xgetsockname(s, sockaddr(&addr), &len);
+	err = create_socket_pairs(s, family, sotype, &c0, &c1, &p0, &p1);
 	if (err)
 		goto close_srv;
 
-	c0 = xsocket(family, sotype, 0);
-	if (c0 < 0)
-		goto close_srv;
-	err = xconnect(c0, sockaddr(&addr), len);
-	if (err)
-		goto close_cli0;
-
-	p0 = xaccept_nonblock(s, NULL, NULL);
-	if (p0 < 0)
-		goto close_cli0;
-
-	c1 = xsocket(family, sotype, 0);
-	if (c1 < 0)
-		goto close_peer0;
-	err = xconnect(c1, sockaddr(&addr), len);
-	if (err)
-		goto close_cli1;
-
-	p1 = xaccept_nonblock(s, NULL, NULL);
-	if (p1 < 0)
-		goto close_cli1;
-
 	err = add_to_sockmap(sock_mapfd, p0, p1);
 	if (err)
-		goto close_peer1;
+		goto close;
 
 	n = write(mode == REDIR_INGRESS ? c1 : p1, "a", 1);
 	if (n < 0)
@@ -795,12 +701,12 @@ static void redir_to_connected(int family, int sotype, int sock_mapfd,
 	if (n == 0)
 		FAIL("%s: incomplete write", log_prefix);
 	if (n < 1)
-		goto close_peer1;
+		goto close;
 
 	key = SK_PASS;
 	err = xbpf_map_lookup_elem(verd_mapfd, &key, &pass);
 	if (err)
-		goto close_peer1;
+		goto close;
 	if (pass != 1)
 		FAIL("%s: want pass count 1, have %d", log_prefix, pass);
 	n = recv_timeout(c0, &b, 1, 0, IO_TIMEOUT_SEC);
@@ -809,13 +715,10 @@ static void redir_to_connected(int family, int sotype, int sock_mapfd,
 	if (n == 0)
 		FAIL("%s: incomplete recv", log_prefix);
 
-close_peer1:
+close:
 	xclose(p1);
-close_cli1:
 	xclose(c1);
-close_peer0:
 	xclose(p0);
-close_cli0:
 	xclose(c0);
 close_srv:
 	xclose(s);