* [PATCH net-next v2 2/2] selftests/net: check auto-selected port with reuse options
2026-09-28 2:31 [PATCH net-next v2 1/2] udp: fix auto-selected port colliding with an existing SO_REUSEPORT socket Jiayuan Chen
@ 2026-09-28 2:31 ` Jiayuan Chen
0 siblings, 0 replies; 2+ messages in thread
From: Jiayuan Chen @ 2026-09-28 2:31 UTC (permalink / raw)
To: netdev
Cc: Jiayuan Chen, Willem de Bruijn, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Simon Horman, Shuah Khan,
Tom Herbert, linux-kernel, linux-kselftest
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
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