From: Geliang Tang <tanggeliang@kylinos.cn>

Implement comprehensive testing for the SO_REUSEPORT socket option:
- Setsockopt and getsockopt helpers for SO_REUSEPORT
- Verification of the set value
- Integration into both client/server workflows
- IPv4 and IPv6 test coverage

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 .../selftests/net/mptcp/mptcp_sockopt.c       | 23 +++++++++++++++++++
 .../selftests/net/mptcp/mptcp_sockopt.sh      |  4 ++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
index a91709aeca06..816d71706f7d 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
@@ -190,9 +190,18 @@ static void do_setsockopt_reuseaddr(int fd)
 		perror("setsockopt(SO_REUSEADDR)");
 }
 
+static void do_setsockopt_reuseport(int fd)
+{
+	int one = 1;
+
+	if (setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)))
+		perror("setsockopt(SO_REUSEPORT)");
+}
+
 static void do_setsockopts(int fd)
 {
 	do_setsockopt_reuseaddr(fd);
+	do_setsockopt_reuseport(fd);
 }
 
 static int sock_listen_mptcp(const char * const listenaddr,
@@ -578,6 +587,18 @@ static void do_getsockopt_reuseaddr(int fd)
 	assert(reuse == 1);
 }
 
+static void do_getsockopt_reuseport(int fd)
+{
+	socklen_t len;
+	int reuse;
+
+	len = sizeof(reuse);
+	if (getsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &reuse, &len))
+		perror("getsockopt(SO_REUSEPORT)");
+
+	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);
@@ -590,6 +611,8 @@ static void do_getsockopts(struct so_state *s, int fd, size_t r, size_t w)
 		do_getsockopt_mptcp_full_info(s, fd);
 
 	do_getsockopt_reuseaddr(fd);
+
+	do_getsockopt_reuseport(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 da6c261275ec..1c357ed757d6 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
@@ -270,7 +270,7 @@ do_mptcp_sockopt_tests()
 	fi
 
 	for opt in "SOL_MPTCP" \
-		   "SO_REUSEADDR"; do
+		   "SO_REUSEADDR" "SO_REUSEPORT"; do
 		print_title "$opt sockopt v4"
 		mptcp_lib_pr_ok
 		mptcp_lib_result_pass "$opt sockopt v4"
@@ -288,7 +288,7 @@ do_mptcp_sockopt_tests()
 	fi
 
 	for opt in "SOL_MPTCP" \
-		   "SO_REUSEADDR"; do
+		   "SO_REUSEADDR" "SO_REUSEPORT"; do
 		print_title "$opt sockopt v6"
 		mptcp_lib_pr_ok
 		mptcp_lib_result_pass "$opt sockopt v6"
-- 
2.48.1