From b5dc3fde8b92286a0cb06bf08e2ec0141cf867bb Mon Sep 17 00:00:00 2001
From: Ido Schimmel <idosch@nvidia.com>
Date: Mon, 19 Oct 2026 17:03:37 +0300
Subject: [PATCH] selftests: netdevsim: Add FIB notification tests for nexthop
 objects

Add IPv4 and IPv6 test cases that program a route that uses a nexthop
object and check that two notifications are emitted for it, with the
second one carrying the RTM_F_TRAP flag.

The new route_nexthop_check() helper follows the same pattern as the
existing route_{addition,deletion,replacement}_check() helpers.

Without "ipv6: Hold RCU when emitting route hardware flags
notification", the IPv6 test case passes, but triggers suspicious RCU
usage splats. The IPv4 test case is added for completeness.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Eric Dumazet <edumazet@kernel.org>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20261019140337.2886875-3-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 .../net/netdevsim/fib_notifications.sh        | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)

diff --git a/tools/testing/selftests/drivers/net/netdevsim/fib_notifications.sh b/tools/testing/selftests/drivers/net/netdevsim/fib_notifications.sh
index 9896580c3d85..c49d6deb621a 100755
--- a/tools/testing/selftests/drivers/net/netdevsim/fib_notifications.sh
+++ b/tools/testing/selftests/drivers/net/netdevsim/fib_notifications.sh
@@ -8,10 +8,12 @@ ALL_TESTS="
 	ipv4_route_deletion_test
 	ipv4_route_replacement_test
 	ipv4_route_offload_failed_test
+	ipv4_route_nexthop_test
 	ipv6_route_addition_test
 	ipv6_route_deletion_test
 	ipv6_route_replacement_test
 	ipv6_route_offload_failed_test
+	ipv6_route_nexthop_test
 "
 
 NETDEVSIM_PATH=/sys/bus/netdevsim/
@@ -269,6 +271,50 @@ ipv4_route_offload_failed_test()
 	log_test "IPv4 route offload failed"
 }
 
+route_nexthop_check()
+{
+	local ip=$1; shift
+	local route=$1; shift
+	local nhid=$1; shift
+	local expected_num_notifications=$1; shift
+	local outfile
+
+	ip netns exec testns1 sysctl -qw net.$ip.fib_notify_on_flag_change=1
+
+	outfile=$(mktemp)
+
+	$IP monitor route &> $outfile &
+	sleep 1
+	$IP route add $route nhid $nhid
+	sleep 1
+	kill_process %%
+
+	route_notify_check $outfile $expected_num_notifications
+	rm -f $outfile
+
+	$IP route del $route nhid $nhid
+}
+
+ipv4_route_nexthop_test()
+{
+	RET=0
+
+	local ip="ipv4"
+	local route=192.0.2.0/24
+	local nhid=1
+
+	$IP -4 nexthop add id $nhid dev dummy1
+
+	# Make sure two notifications will be emitted for a programmed route
+	# that uses a nexthop object.
+	local expected_num_notifications=2
+	route_nexthop_check $ip $route $nhid $expected_num_notifications
+
+	$IP nexthop del id $nhid
+
+	log_test "IPv4 route with nexthop object"
+}
+
 ipv6_route_addition_test()
 {
 	RET=0
@@ -385,6 +431,26 @@ ipv6_route_offload_failed_test()
 	log_test "IPv6 route offload failed"
 }
 
+ipv6_route_nexthop_test()
+{
+	RET=0
+
+	local ip="ipv6"
+	local route=2001:db8:1::/64
+	local nhid=1
+
+	$IP -6 nexthop add id $nhid dev dummy1
+
+	# Make sure two notifications will be emitted for a programmed route
+	# that uses a nexthop object.
+	local expected_num_notifications=2
+	route_nexthop_check $ip $route $nhid $expected_num_notifications
+
+	$IP nexthop del id $nhid
+
+	log_test "IPv6 route with nexthop object"
+}
+
 setup_prepare()
 {
 	modprobe netdevsim &> /dev/null