[PATCH net] selftests: bonding: feed link monitor to deflake prio_test

[Bjoern Doebel <doebel@amazon.de>]

With the bond idle between test steps, the arp/ns link monitor can
declare a healthy slave down (~300ms without RX/TX). If this hits a
failover step, the bond picks a different active slave than expected,
and primary_reselect=failure/better never reverts it:

  TEST: prio (active-backup ns_ip6_target primary_reselect 2) [FAIL]
      Current active slave is eth0 but not eth2

Reproducible when running tests under load (2-4 / 100 runs).

Fix by pinging a non-existent neighbor for the duration of the test to
keep traffic coming. 100 runs under the same load with the patch
applied: 0 failures.

Fixes: 42a8d4aaea84 ("selftests: bonding: add bonding prio option test")
Signed-off-by: Bjoern Doebel <doebel@amazon.de>
---
 .../selftests/drivers/net/bonding/bond_options.sh   | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/tools/testing/selftests/drivers/net/bonding/bond_options.sh b/tools/testing/selftests/drivers/net/bonding/bond_options.sh
index 187b478d0ddf2..f599a2a8ef156 100755
--- a/tools/testing/selftests/drivers/net/bonding/bond_options.sh
+++ b/tools/testing/selftests/drivers/net/bonding/bond_options.sh
@@ -74,6 +74,16 @@ prio_test()
 
 	# create bond
 	bond_reset "${param}"
+
+	# Keep the arp/ns link monitor fed for the duration of the test:
+	# ping a non-existent neighbor, which generates steady broadcast
+	# ARP requests sourced from the bond's own address. These egress on
+	# the active slave and are flooded onto the backup slaves' links,
+	# where they validate as RX activity. Without traffic, idle slaves
+	# are declared down by the monitor between test steps and the
+	# failover checks below race with the monitor.
+	ip netns exec ${s_ns} ping -i 0.1 -W 1 192.0.2.99 &> /dev/null &
+	local ping_pid=$!
 	# set active_slave to primary eth1 specifically
 	ip -n ${s_ns} link set bond0 type bond active_slave eth1
 
@@ -157,6 +167,9 @@ prio_test()
 		check_active_slave "eth0"
 		bond_check_connection "change slave prio"
 	fi
+
+	kill $ping_pid 2>/dev/null
+	wait $ping_pid 2>/dev/null
 }
 
 prio_miimon()

base-commit: 05441d697f7f9a927264f4058cbbc6a03dfcac9d
-- 
2.50.1