selftests: net: Add SO_REUSEADDR test to check if 4-tuples are fully utilized.

This commit adds a test to check if we can fully utilize 4-tuples for
connect() when all ephemeral ports are exhausted.

The test program changes the local port range to use only one port and binds
two sockets with or without SO_REUSEADDR and SO_REUSEPORT, and with the same
EUID or with different EUIDs, then do listen().

We should be able to bind only one socket having both SO_REUSEADDR and
SO_REUSEPORT per EUID, which restriction is to prevent unintentional
listen().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 35 insertions, 0 deletions

diff --git a/tools/testing/selftests/net/reuseaddr_ports_exhausted.sh b/tools/testing/selftests/net/reuseaddr_ports_exhausted.sh
new file mode 100755
index 000000000000..20e3a2913d06
--- /dev/null
+++ b/tools/testing/selftests/net/reuseaddr_ports_exhausted.sh
@@ -0,0 +1,35 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Run tests when all ephemeral ports are exhausted.
+#
+# Author: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
+
+set +x
+set -e
+
+readonly NETNS="ns-$(mktemp -u XXXXXX)"
+
+setup() {
+	ip netns add "${NETNS}"
+	ip -netns "${NETNS}" link set lo up
+	ip netns exec "${NETNS}" \
+		sysctl -w net.ipv4.ip_local_port_range="32768 32768" \
+		> /dev/null 2>&1
+	ip netns exec "${NETNS}" \
+		sysctl -w net.ipv4.ip_autobind_reuse=1 > /dev/null 2>&1
+}
+
+cleanup() {
+	ip netns del "${NETNS}"
+}
+
+trap cleanup EXIT
+setup
+
+do_test() {
+	ip netns exec "${NETNS}" ./reuseaddr_ports_exhausted
+}
+
+do_test
+echo "tests done"