From: Geliang Tang <tanggeliang@kylinos.cn>

Introduce helper functions to set and verify the SO_REUSEADDR socket
option. This includes:
- do_setsockopt_reuseaddr() to set the option
- do_getsockopt_reuseaddr() to validate the value
- Integration into IPv4/IPv6 test flows
- Explicit result reporting in the test script

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 .../selftests/net/mptcp/mptcp_sockopt.c       | 34 ++++++++++++++++---
 .../selftests/net/mptcp/mptcp_sockopt.sh      |  7 ++--
 2 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
index e934dd26a59d..a91709aeca06 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
@@ -182,6 +182,19 @@ static void xgetaddrinfo(const char *node, const char *service,
 	}
 }
 
+static void do_setsockopt_reuseaddr(int fd)
+{
+	int one = 1;
+
+	if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)))
+		perror("setsockopt(SO_REUSEADDR)");
+}
+
+static void do_setsockopts(int fd)
+{
+	do_setsockopt_reuseaddr(fd);
+}
+
 static int sock_listen_mptcp(const char * const listenaddr,
 			     const char * const port)
 {
@@ -195,7 +208,6 @@ static int sock_listen_mptcp(const char * const listenaddr,
 	hints.ai_family = pf;
 
 	struct addrinfo *a, *addr;
-	int one = 1;
 
 	xgetaddrinfo(listenaddr, port, &hints, &addr);
 	hints.ai_family = pf;
@@ -205,9 +217,7 @@ static int sock_listen_mptcp(const char * const listenaddr,
 		if (sock < 0)
 			continue;
 
-		if (-1 == setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one,
-				     sizeof(one)))
-			perror("setsockopt");
+		do_setsockopts(sock);
 
 		if (bind(sock, a->ai_addr, a->ai_addrlen) == 0)
 			break; /* success */
@@ -246,6 +256,8 @@ static int sock_connect_mptcp(const char * const remoteaddr,
 		if (sock < 0)
 			continue;
 
+		do_setsockopts(sock);
+
 		if (connect(sock, a->ai_addr, a->ai_addrlen) == 0)
 			break; /* success */
 
@@ -554,6 +566,18 @@ static void do_getsockopt_mptcp_full_info(struct so_state *s, int fd)
 	assert(!memcmp(&sfinfo->addrs, &s->addrs, sizeof(struct mptcp_subflow_addrs)));
 }
 
+static void do_getsockopt_reuseaddr(int fd)
+{
+	socklen_t len;
+	int reuse;
+
+	len = sizeof(reuse);
+	if (getsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &reuse, &len))
+		perror("getsockopt(SO_REUSEADDR)");
+
+	assert(reuse == 1);
+}
+
 static void do_getsockopts(struct so_state *s, int fd, size_t r, size_t w)
 {
 	do_getsockopt_mptcp_info(s, fd, w);
@@ -564,6 +588,8 @@ static void do_getsockopts(struct so_state *s, int fd, size_t r, size_t w)
 
 	if (r)
 		do_getsockopt_mptcp_full_info(s, fd);
+
+	do_getsockopt_reuseaddr(fd);
 }
 
 static void connect_one_server(int fd, int pipefd)
diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
index 003d218defa8..da6c261275ec 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
@@ -269,7 +269,8 @@ do_mptcp_sockopt_tests()
 		return
 	fi
 
-	for opt in "SOL_MPTCP"; do
+	for opt in "SOL_MPTCP" \
+		   "SO_REUSEADDR"; do
 		print_title "$opt sockopt v4"
 		mptcp_lib_pr_ok
 		mptcp_lib_result_pass "$opt sockopt v4"
@@ -286,12 +287,12 @@ do_mptcp_sockopt_tests()
 		return
 	fi
 
-	for opt in "SOL_MPTCP"; do
+	for opt in "SOL_MPTCP" \
+		   "SO_REUSEADDR"; do
 		print_title "$opt sockopt v6"
 		mptcp_lib_pr_ok
 		mptcp_lib_result_pass "$opt sockopt v6"
 	done
-
 }
 
 run_tests()
-- 
2.48.1