[PATCH net] selftests: net: fix race condition in icmp.sh causing CKI sporadic failures
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IN NET-NEXT: 1 (0M)
From: Prasenjit Mukherjee <hidden>
Date: 2026-10-12 12:54:14
Subsystem:
kernel selftest framework, networking [general], the rest · Maintainers:
Shuah Khan, Shuah Khan, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
1 review trailer; queued in net-next as c6b97e579ea3 on 2026-10-20.
CKI reports sporadic failures in icmp.sh, Davide suggests this might be
caused by a race condition where tcpdump starts capturing after the last of
expected ICMP unreachable packets have been sent.
Fix this replacing tcpdump with a tc flower filter that
matches ICMP Destination Unreachable (type 3, code 0),
and match on act_gact counters instead.
This will remove any race condition to appear.
Fixes: 7e9838b7915e2 ("selftests/net: Add icmp.sh for testing ICMP dummy address responses")
CC: Toke Høiland-Jørgensen <redacted>
Suggested-by: Davide Caratti <redacted>
Reviewed-by: Davide Caratti <redacted>
Reported-by: CKI Project <redacted>
Closes: https://datawarehouse.cki-project.org/issue/3658
Signed-off-by: Prasenjit Mukherjee <redacted>
---
tools/testing/selftests/net/icmp.sh | 32 ++++++++++++++---------------
1 file changed, 16 insertions(+), 16 deletions(-)
diff --git a/tools/testing/selftests/net/icmp.sh b/tools/testing/selftests/net/icmp.sh
index 824cb0e35eff..0714e8b34d12 100755
--- a/tools/testing/selftests/net/icmp.sh
+++ b/tools/testing/selftests/net/icmp.sh@@ -27,11 +27,8 @@ PINGADDR=172.16.1.1 RT2=172.16.0.0/24 H2_IP6=2001:db8:1::2 -TMPFILE=$(mktemp) - cleanup() { - rm -f "$TMPFILE" cleanup_ns $NS1 $NS2 }
@@ -52,21 +49,24 @@ ip -netns $NS2 route add $RT2 via inet6 $H1_IP6 # Make sure ns2 will respond with ICMP unreachable ip netns exec $NS2 sysctl -qw net.ipv4.icmp_ratelimit=0 net.ipv4.ip_forward=1 +# Install tc flower filter to count ICMP unreachable from 192.0.0.8 +ip netns exec $NS1 tc qdisc add dev veth0 clsact +ip netns exec $NS1 tc filter add dev veth0 ingress \ + protocol ip pref 1 handle 1 flower \ + src_ip 192.0.0.8 ip_proto icmp type 3 code 0 \ + action pass -# Run the test - a ping runs in the background, and we capture ICMP responses -# with tcpdump; -c 1 means it should exit on the first ping, but add a timeout -# in case something goes wrong -ip netns exec $NS1 ping -w 3 -i 0.5 $PINGADDR >/dev/null & -ip netns exec $NS1 timeout 10 tcpdump -tpni veth0 -c 1 'icmp and icmp[icmptype] != icmp-echo' > $TMPFILE 2>/dev/null +# Send ping to trigger ICMP unreachable from ns2 +ip netns exec $NS1 ping -c 1 $PINGADDR >/dev/null 2>&1 -# Parse response and check for dummy address -# tcpdump output looks like: -# IP 192.0.0.8 > 172.16.0.1: ICMP net 172.16.1.1 unreachable, length 92 -RESP_IP=$(awk '{print $2}' < $TMPFILE) -if [[ "$RESP_IP" != "192.0.0.8" ]]; then - echo "FAIL - got ICMP response from $RESP_IP, should be 192.0.0.8" - exit 1 -else +# Verify ICMP unreachable was received from dummy address 192.0.0.8 per RFC7600 +COUNT=$(ip netns exec $NS1 tc -j -s filter show dev veth0 ingress \ + | jq '.[1].options.actions[].stats.packets') + +if [[ "$COUNT" -eq 1 ]]; then echo "OK" exit 0 +else + echo "FAIL - expected 1 ICMP unreachable from 192.0.0.8, got $COUNT" + exit 1 fi
--
2.55.0