From c41817fcaf397f6ff7c530b682581f5eb5465844 Mon Sep 17 00:00:00 2001
From: Omar Ramadan <omar@blockcast.net>
Date: Mon, 28 Sep 2026 23:23:12 +0300
Subject: [PATCH] selftests: net: amt: check that the relay's queries bypass
 the amt device

The relay used to hand its General Queries to dev_queue_xmit() on the
amt device, where a query could wait in a qdisc and outlive the tunnel
it pointed to. The previous patch sends them directly from the receive
path instead.

Count the IGMP and MLD queries that leave the relay through amtr with
tc flower filters on its egress, installed before the gateway comes
up, and check that there are none. The forwarding tests before it
already show that the gateway received its queries, since it cannot
join without one.

Without the previous patch the new test fails (one run counted 7 IGMP
and 6 MLD queries); with it, all of amt.sh passes.

Signed-off-by: Omar Ramadan <omar@blockcast.net>
Link: https://patch.msgid.link/20260928202312.74574-3-omar@blockcast.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 tools/testing/selftests/net/amt.sh | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/tools/testing/selftests/net/amt.sh b/tools/testing/selftests/net/amt.sh
index 663744305e52..d13b20cccba9 100755
--- a/tools/testing/selftests/net/amt.sh
+++ b/tools/testing/selftests/net/amt.sh
@@ -150,6 +150,13 @@ setup_interface()
 	ip netns exec "${RELAY}" ip a a 10.0.0.2/24 dev relay_gw
 	ip netns exec "${RELAY}" ip link add amtr type amt mode relay \
 		local 10.0.0.2 dev relay_gw relay_port 2268 max_tunnels 4
+	# Count the IGMP and MLD queries that leave the relay through its own
+	# amt device; test_query_egress expects none.
+	ip netns exec "${RELAY}" tc qdisc add dev amtr clsact
+	ip netns exec "${RELAY}" tc filter add dev amtr egress pref 1 \
+		protocol ip flower ip_proto 0x2 action pass
+	ip netns exec "${RELAY}" tc filter add dev amtr egress pref 2 \
+		protocol ipv6 flower ip_proto icmpv6 type 130 action pass
 	ip netns exec "${RELAY}" ip a a 172.17.0.1/24 dev relay_src
 	ip netns exec "${RELAY}" ip a a 2001:db8:3::1/64 dev relay_src
 	ip netns exec "${SOURCE}" ip a a 172.17.0.2/24 dev src_relay
@@ -246,6 +253,27 @@ test_ipv6_forward()
 	fi
 }
 
+# The relay sends its General Queries straight from the receive path, in
+# the same context that found the tunnel. A query queued on the amt device
+# instead could outlive the tunnel it was built for. The forwarding tests
+# above show that the gateway got its queries.
+test_query_egress()
+{
+	local n4 n6
+
+	n4=$(ip netns exec "${RELAY}" tc -s -j filter show dev amtr egress \
+		pref 1 | jq '[.[].options.actions[0].stats.packets // empty] | add // 0')
+	n6=$(ip netns exec "${RELAY}" tc -s -j filter show dev amtr egress \
+		pref 2 | jq '[.[].options.actions[0].stats.packets // empty] | add // 0')
+	if [ "$n4" -eq 0 ] && [ "$n6" -eq 0 ]; then
+		printf "TEST: %-60s  [ OK ]\n" "amt relay queries bypass the amt device"
+	else
+		printf "TEST: %-60s  [FAIL]\n" "amt relay queries bypass the amt device"
+		echo "IGMP queries on amtr egress: $n4, MLD queries: $n6" >&2
+		ERR=1
+	fi
+}
+
 send_mcast4()
 {
 	sleep 5
@@ -287,6 +315,7 @@ wait $pid || err=$?
 if [ $err -eq 1 ]; then
 	ERR=1
 fi
+test_query_egress
 printf "TEST: %-50s" "IPv4 amt traffic forwarding torture"
 send_mcast_torture4
 printf "  [ OK ]\n"