selftests: add route_localnet test script

Add a simple scripts to exercise several situations when enable
route_localnet.

Signed-off-by: Shijie Luo <luoshijie1@huawei.com>
Signed-off-by: Zhiqiang liu <liuzhiqiang26@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

tools/testing/selftests/net/route_localnet.sh

@@ -0,0 +1,74 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Run a couple of tests when route_localnet = 1.
+
+readonly PEER_NS="ns-peer-$(mktemp -u XXXXXX)"
+
+setup() {
+    ip netns add "${PEER_NS}"
+    ip -netns "${PEER_NS}" link set dev lo up
+    ip link add name veth0 type veth peer name veth1
+    ip link set dev veth0 up
+    ip link set dev veth1 netns "${PEER_NS}"
+
+    # Enable route_localnet and delete useless route 127.0.0.0/8.
+    sysctl -w net.ipv4.conf.veth0.route_localnet=1
+    ip netns exec "${PEER_NS}" sysctl -w net.ipv4.conf.veth1.route_localnet=1
+    ip route del 127.0.0.0/8 dev lo table local
+    ip netns exec "${PEER_NS}" ip route del 127.0.0.0/8 dev lo table local
+
+    ifconfig veth0 127.25.3.4/24 up
+    ip netns exec "${PEER_NS}" ifconfig veth1 127.25.3.14/24 up
+
+    ip route flush cache
+    ip netns exec "${PEER_NS}" ip route flush cache
+}
+
+cleanup() {
+    ip link del veth0
+    ip route add local 127.0.0.0/8 dev lo proto kernel scope host src 127.0.0.1
+    local -r ns="$(ip netns list|grep $PEER_NS)"
+    [ -n "$ns" ] && ip netns del $ns 2>/dev/null
+}
+
+# Run test when arp_announce = 2.
+run_arp_announce_test() {
+    echo "run arp_announce test"
+    setup
+
+    sysctl -w net.ipv4.conf.veth0.arp_announce=2
+    ip netns exec "${PEER_NS}" sysctl -w net.ipv4.conf.veth1.arp_announce=2
+    ping -c5 -I veth0 127.25.3.14
+    if [ $? -ne 0 ];then
+        echo "failed"
+    else
+        echo "ok"
+    fi
+
+    cleanup
+}
+
+# Run test when arp_ignore = 3.
+run_arp_ignore_test() {
+    echo "run arp_ignore test"
+    setup
+
+    sysctl -w net.ipv4.conf.veth0.arp_ignore=3
+    ip netns exec "${PEER_NS}" sysctl -w net.ipv4.conf.veth1.arp_ignore=3
+    ping -c5 -I veth0 127.25.3.14
+    if [ $? -ne 0 ];then
+        echo "failed"
+    else
+        echo "ok"
+    fi
+
+    cleanup
+}
+
+run_all_tests() {
+    run_arp_announce_test
+    run_arp_ignore_test
+}
+
+run_all_tests