[PATCH net 2/2] selftests/net: check auto-selected port with SO_REUSEPORT

[Jiayuan Chen <jiayuan.chen@linux.dev>]

Use IP_LOCAL_PORT_RANGE to limit a socket to 8 ports and bind 8
SO_REUSEPORT sockets to port 0. They must get 8 distinct ports and
the 9th bind must fail with EADDRINUSE. TCP and UDP should both
behave this way.

  # ./ip_local_port_range.sh

Before the udp fix:

  ok 5 ip_local_port_range.ip4_tcp.exhaust_8_port_range_reuseport
  not ok 12 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseport
  ok 33 ip_local_port_range.ip6_tcp.exhaust_8_port_range_reuseport
  not ok 40 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseport

After:

  ok 5 ip_local_port_range.ip4_tcp.exhaust_8_port_range_reuseport
  ok 12 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseport
  ok 33 ip_local_port_range.ip6_tcp.exhaust_8_port_range_reuseport
  ok 40 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseport

Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
 .../selftests/net/ip_local_port_range.c       | 27 ++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/ip_local_port_range.c b/tools/testing/selftests/net/ip_local_port_range.c
index e6834a6cfc8f..04feb702fff4 100644
--- a/tools/testing/selftests/net/ip_local_port_range.c
+++ b/tools/testing/selftests/net/ip_local_port_range.c
@@ -301,7 +301,9 @@ TEST_F(ip_local_port_range, single_port_range)
 	}
 }
 
-TEST_F(ip_local_port_range, exhaust_8_port_range)
+static void exhaust_8_port_range(struct __test_metadata *_metadata,
+				 const FIXTURE_VARIANT(ip_local_port_range) *variant,
+				 bool reuseport)
 {
 	__u8 port_set = 0;
 	int i, fd, err;
@@ -313,6 +315,11 @@ TEST_F(ip_local_port_range, exhaust_8_port_range)
 		fd = socket(variant->so_domain, variant->so_type, variant->so_protocol);
 		ASSERT_GE(fd, 0) TH_LOG("socket failed");
 
+		if (reuseport) {
+			err = setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &(int){ 1 }, sizeof(int));
+			ASSERT_TRUE(!err) TH_LOG("setsockopt(SO_REUSEPORT) failed");
+		}
+
 		range = pack_port_range(40000, 40007);
 		err = setsockopt(fd, SOL_IP, IP_LOCAL_PORT_RANGE, &range, sizeof(range));
 		ASSERT_TRUE(!err) TH_LOG("setsockopt(IP_LOCAL_PORT_RANGE) failed");
@@ -335,6 +342,11 @@ TEST_F(ip_local_port_range, exhaust_8_port_range)
 	fd = socket(variant->so_domain, variant->so_type, variant->so_protocol);
 	ASSERT_GE(fd, 0) TH_LOG("socket failed");
 
+	if (reuseport) {
+		err = setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &(int){ 1 }, sizeof(int));
+		ASSERT_TRUE(!err) TH_LOG("setsockopt(SO_REUSEPORT) failed");
+	}
+
 	range = pack_port_range(40000, 40007);
 	err = setsockopt(fd, SOL_IP, IP_LOCAL_PORT_RANGE, &range, sizeof(range));
 	ASSERT_TRUE(!err) TH_LOG("setsockopt(IP_LOCAL_PORT_RANGE) failed");
@@ -352,6 +364,19 @@ TEST_F(ip_local_port_range, exhaust_8_port_range)
 	}
 }
 
+TEST_F(ip_local_port_range, exhaust_8_port_range)
+{
+	exhaust_8_port_range(_metadata, variant, false);
+}
+
+/* Auto-selected port must not land on a port already taken by a
+ * SO_REUSEPORT socket, so all 8 sockets must get distinct ports.
+ */
+TEST_F(ip_local_port_range, exhaust_8_port_range_reuseport)
+{
+	exhaust_8_port_range(_metadata, variant, true);
+}
+
 TEST_F(ip_local_port_range, late_bind)
 {
 	union {
-- 
2.43.0