From: Geliang Tang <tanggeliang@kylinos.cn>

Add tests for IP_FREEBIND (IPv4) and IPV6_FREEBIND (IPv6):
- Setsockopt helpers to enable FREEBIND
- Getsockopt validation of the enabled state
- Test integration for both address families
- Script result reporting

Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
 .../selftests/net/mptcp/mptcp_sockopt.c       | 27 +++++++++++++++++++
 .../selftests/net/mptcp/mptcp_sockopt.sh      |  6 +++--
 2 files changed, 31 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
index 25456e540cad..e9ef908dc270 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.c
@@ -233,12 +233,23 @@ static void do_setsockopt_bindtoifindex(int fd)
 		perror("setsockopt(SO_BINDTOIFINDEX)");
 }
 
+static void do_setsockopt_freebind(int fd)
+{
+	int optname = (pf == AF_INET ? IP_FREEBIND : IPV6_FREEBIND);
+	int level = (pf == AF_INET ? SOL_IP : SOL_IPV6);
+	int enable = 1;
+
+	if (setsockopt(fd, level, optname, &enable, sizeof(enable)))
+		perror("setsockopt(IP(V6)_FREEBIND)");
+}
+
 static void do_setsockopts(int fd)
 {
 	do_setsockopt_reuseaddr(fd);
 	do_setsockopt_reuseport(fd);
 	do_setsockopt_bindtodevice(fd);
 	do_setsockopt_bindtoifindex(fd);
+	do_setsockopt_freebind(fd);
 }
 
 static int sock_listen_mptcp(const char * const listenaddr,
@@ -661,6 +672,20 @@ static void do_getsockopt_bindtoifindex(int fd)
 	assert(ifindex == get_ifindex(fd, "lo"));
 }
 
+static void do_getsockopt_freebind(int fd)
+{
+	int optname = (pf == AF_INET ? IP_FREEBIND : IPV6_FREEBIND);
+	int level = (pf == AF_INET ? SOL_IP : SOL_IPV6);
+	socklen_t len;
+	int enable;
+
+	len = sizeof(enable);
+	if (getsockopt(fd, level, optname, &enable, &len))
+		die_perror("getsockopt(IP(V6)_FREEBIND)");
+
+	assert(enable == 1);
+}
+
 static void do_getsockopts(struct so_state *s, int fd, size_t r, size_t w)
 {
 	do_getsockopt_mptcp_info(s, fd, w);
@@ -679,6 +704,8 @@ static void do_getsockopts(struct so_state *s, int fd, size_t r, size_t w)
 	do_getsockopt_bindtodevice(fd);
 
 	do_getsockopt_bindtoifindex(fd);
+
+	do_getsockopt_freebind(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 7f2effd82af8..193f4d4dc41a 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
@@ -271,7 +271,8 @@ do_mptcp_sockopt_tests()
 
 	for opt in "SOL_MPTCP" \
 		   "SO_REUSEADDR" "SO_REUSEPORT" \
-		   "SO_BINDTODEVICE" "SO_BINDTOIFINDEX"; do
+		   "SO_BINDTODEVICE" "SO_BINDTOIFINDEX" \
+		   "IP_FREEBIND"; do
 		print_title "$opt sockopt v4"
 		mptcp_lib_pr_ok
 		mptcp_lib_result_pass "$opt sockopt v4"
@@ -290,7 +291,8 @@ do_mptcp_sockopt_tests()
 
 	for opt in "SOL_MPTCP" \
 		   "SO_REUSEADDR" "SO_REUSEPORT" \
-		   "SO_BINDTODEVICE" "SO_BINDTOIFINDEX"; do
+		   "SO_BINDTODEVICE" "SO_BINDTOIFINDEX" \
+		   "IPV6_FREEBIND"; do
 		print_title "$opt sockopt v6"
 		mptcp_lib_pr_ok
 		mptcp_lib_result_pass "$opt sockopt v6"
-- 
2.48.1