[PATCH net-next v2 2/2] selftests/net: check auto-selected port with reuse options

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

Use IP_LOCAL_PORT_RANGE to limit a socket to 8 ports, bind 8 sockets
to port 0 and check they get 8 distinct ports and the 9th bind fails
with EADDRINUSE. Run it for the four combinations of reuse options on
the sockets:

  none                         (existing test)
  SO_REUSEPORT
  SO_REUSEADDR
  SO_REUSEADDR + SO_REUSEPORT

TCP passes all four. Before the udp fix UDP only passes the first
one: the scan hands out a port already taken by a socket with the
same reuse options, so fewer than 8 distinct ports come back and the
9th bind succeeds.

  # ./ip_local_port_range.sh

Before:

  ok 13 ip_local_port_range.ip4_udp.exhaust_8_port_range
  not ok 14 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseport
  not ok 15 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseaddr
  not ok 16 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseaddr_reuseport
  ok 49 ip_local_port_range.ip6_udp.exhaust_8_port_range
  not ok 50 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseport
  not ok 51 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseaddr
  not ok 52 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseaddr_reuseport

After:

  ok 13 ip_local_port_range.ip4_udp.exhaust_8_port_range
  ok 14 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseport
  ok 15 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseaddr
  ok 16 ip_local_port_range.ip4_udp.exhaust_8_port_range_reuseaddr_reuseport
  ok 49 ip_local_port_range.ip6_udp.exhaust_8_port_range
  ok 50 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseport
  ok 51 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseaddr
  ok 52 ip_local_port_range.ip6_udp.exhaust_8_port_range_reuseaddr_reuseport

Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
---
 .../selftests/net/ip_local_port_range.c       | 52 ++++++++++++++++++-
 1 file changed, 51 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..3d32b33cba46 100644
--- a/tools/testing/selftests/net/ip_local_port_range.c
+++ b/tools/testing/selftests/net/ip_local_port_range.c
@@ -301,7 +301,27 @@ TEST_F(ip_local_port_range, single_port_range)
 	}
 }
 
-TEST_F(ip_local_port_range, exhaust_8_port_range)
+#define REUSEADDR	0x1
+#define REUSEPORT	0x2
+
+static int set_reuse_opts(int fd, unsigned int flags)
+{
+	int one = 1;
+
+	if ((flags & REUSEADDR) &&
+	    setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one)))
+		return -1;
+
+	if ((flags & REUSEPORT) &&
+	    setsockopt(fd, SOL_SOCKET, SO_REUSEPORT, &one, sizeof(one)))
+		return -1;
+
+	return 0;
+}
+
+static void exhaust_8_port_range(struct __test_metadata *_metadata,
+				 const FIXTURE_VARIANT(ip_local_port_range) *variant,
+				 unsigned int flags)
 {
 	__u8 port_set = 0;
 	int i, fd, err;
@@ -313,6 +333,9 @@ 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");
 
+		err = set_reuse_opts(fd, flags);
+		ASSERT_TRUE(!err) TH_LOG("setsockopt(SO_REUSE*) 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 +358,9 @@ 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");
 
+	err = set_reuse_opts(fd, flags);
+	ASSERT_TRUE(!err) TH_LOG("setsockopt(SO_REUSE*) 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 +378,30 @@ 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, 0);
+}
+
+/* Auto-selected port must not land on a port already taken by another
+ * socket, whatever reuse options both of them have, 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, REUSEPORT);
+}
+
+TEST_F(ip_local_port_range, exhaust_8_port_range_reuseaddr)
+{
+	exhaust_8_port_range(_metadata, variant, REUSEADDR);
+}
+
+TEST_F(ip_local_port_range, exhaust_8_port_range_reuseaddr_reuseport)
+{
+	exhaust_8_port_range(_metadata, variant, REUSEADDR | REUSEPORT);
+}
+
 TEST_F(ip_local_port_range, late_bind)
 {
 	union {
-- 
2.43.0