selftests: add regression test for br_netfilter panic

Add a new netfilter selftests to test against br_netfilter panics when
VxLAN single-device is used together with untagged traffic and high MTU.

Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Andy Roulin <aroulin@nvidia.com>
Acked-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/20241001154400.22787-3-aroulin@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/netfilter/Makefile

@@ -31,6 +31,7 @@ TEST_PROGS += nft_tproxy_tcp.sh
 TEST_PROGS += nft_tproxy_udp.sh
 TEST_PROGS += nft_zones_many.sh
 TEST_PROGS += rpath.sh
+TEST_PROGS += vxlan_mtu_frag.sh
 TEST_PROGS += xt_string.sh
 
 TEST_PROGS_EXTENDED = nft_concat_range_perf.sh

tools/testing/selftests/net/netfilter/config

@@ -7,6 +7,7 @@ CONFIG_BRIDGE_EBT_REDIRECT=m
 CONFIG_BRIDGE_EBT_T_FILTER=m
 CONFIG_BRIDGE_NETFILTER=m
 CONFIG_BRIDGE_NF_EBTABLES=m
+CONFIG_BRIDGE_VLAN_FILTERING=y
 CONFIG_CGROUP_BPF=y
 CONFIG_DUMMY=m
 CONFIG_INET_ESP=m
@@ -84,6 +85,7 @@ CONFIG_NFT_SYNPROXY=m
 CONFIG_NFT_TPROXY=m
 CONFIG_VETH=m
 CONFIG_VLAN_8021Q=m
+CONFIG_VXLAN=m
 CONFIG_XFRM_USER=m
 CONFIG_XFRM_STATISTICS=y
 CONFIG_NET_PKTGEN=m

tools/testing/selftests/net/netfilter/vxlan_mtu_frag.sh

@@ -0,0 +1,121 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source lib.sh
+
+if ! modprobe -q -n br_netfilter 2>&1; then
+        echo "SKIP: Test needs br_netfilter kernel module"
+        exit $ksft_skip
+fi
+
+cleanup()
+{
+        cleanup_all_ns
+}
+
+trap cleanup EXIT
+
+setup_ns host vtep router
+
+create_topology()
+{
+    ip link add host-eth0 netns "$host" type veth peer name vtep-host netns "$vtep"
+    ip link add vtep-router netns "$vtep" type veth peer name router-vtep netns "$router"
+}
+
+setup_host()
+{
+    # bring ports up
+    ip -n "$host" addr add 10.0.0.1/24 dev host-eth0
+    ip -n "$host" link set host-eth0 up
+
+    # Add VLAN 10,20
+    for vid in 10 20; do
+        ip -n "$host" link add link host-eth0 name host-eth0.$vid type vlan id $vid
+        ip -n "$host" addr add 10.0.$vid.1/24 dev host-eth0.$vid
+        ip -n "$host" link set host-eth0.$vid up
+    done
+}
+
+setup_vtep()
+{
+    # create bridge on vtep
+    ip -n "$vtep" link add name br0 type bridge
+    ip -n "$vtep" link set br0 type bridge vlan_filtering 1
+
+    # VLAN 10 is untagged PVID
+    ip -n "$vtep" link set dev vtep-host master br0
+    bridge -n "$vtep" vlan add dev vtep-host vid 10 pvid untagged
+
+    # VLAN 20 as other VID
+    ip -n "$vtep" link set dev vtep-host master br0
+    bridge -n "$vtep" vlan add dev vtep-host vid 20
+
+    # single-vxlan device on vtep
+    ip -n "$vtep" address add dev vtep-router 60.0.0.1/24
+    ip -n "$vtep" link add dev vxd type vxlan external \
+        vnifilter local 60.0.0.1 remote 60.0.0.2 dstport 4789 ttl 64
+    ip -n "$vtep" link set vxd master br0
+
+    # Add VLAN-VNI 1-1 mappings
+    bridge -n "$vtep" link set dev vxd vlan_tunnel on
+    for vid in 10 20; do
+        bridge -n "$vtep" vlan add dev vxd vid $vid
+        bridge -n "$vtep" vlan add dev vxd vid $vid tunnel_info id $vid
+        bridge -n "$vtep" vni add dev vxd vni $vid
+    done
+
+    # bring ports up
+    ip -n "$vtep" link set vxd up
+    ip -n "$vtep" link set vtep-router up
+    ip -n "$vtep" link set vtep-host up
+    ip -n "$vtep" link set dev br0 up
+}
+
+setup_router()
+{
+    # bring ports up
+    ip -n "$router" link set router-vtep up
+}
+
+setup()
+{
+    modprobe -q br_netfilter
+    create_topology
+    setup_host
+    setup_vtep
+    setup_router
+}
+
+test_large_mtu_untagged_traffic()
+{
+    ip -n "$vtep" link set vxd mtu 1000
+    ip -n "$host" neigh add 10.0.0.2 lladdr ca:fe:ba:be:00:01 dev host-eth0
+    ip netns exec "$host" \
+        ping -q 10.0.0.2 -I host-eth0 -c 1 -W 0.5 -s2000 > /dev/null 2>&1
+    return 0
+}
+
+test_large_mtu_tagged_traffic()
+{
+    for vid in 10 20; do
+        ip -n "$vtep" link set vxd mtu 1000
+        ip -n "$host" neigh add 10.0.$vid.2 lladdr ca:fe:ba:be:00:01 dev host-eth0.$vid
+        ip netns exec "$host" \
+            ping -q 10.0.$vid.2 -I host-eth0.$vid -c 1 -W 0.5 -s2000 > /dev/null 2>&1
+    done
+    return 0
+}
+
+do_test()
+{
+    # Frames will be dropped so ping will not succeed
+    # If it doesn't panic, it passes
+    test_large_mtu_tagged_traffic
+    test_large_mtu_untagged_traffic
+}
+
+setup && \
+echo "Test for VxLAN fragmentation with large MTU in br_netfilter:" && \
+do_test && echo "PASS!"
+exit $?