From: Qingshuang Fu <[email protected]> The broadcast_pmtu.sh test verifies that broadcast route MTU is respected, but it uses an incorrect criteria for test success: it relies solely on the ping command's exit code, which leads to false failures.
When the kernel correctly blocks oversized broadcast packets due to the configured MTU limit (1500), ping fails to transmit any packets and returns exit code 1. The original script interprets this as a test failure, even though the kernel is properly enforcing the MTU (the core goal of the test). Fix this by: 1. Checking ping's output for clear signs of MTU enforcement (instead of exit code) - Match "0 packets transmitted" (no packets sent due to MTU limit) - Match "message too long" (kernel rejects oversized packets) 2. Use an exit code variable to avoid early exit breaking the script flow 3. Maintain full compatibility with the original setup/cleanup logic After this fix, the script returns 0 (success) when the kernel enforces the broadcast route MTU (packets blocked), and 1 (failure) only when the kernel fails to enforce the MTU (packets are transmitted but no response is received). Signed-off-by: Qingshuang Fu <[email protected]> --- tools/testing/selftests/net/broadcast_pmtu.sh | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/net/broadcast_pmtu.sh b/tools/testing/selftests/net/broadcast_pmtu.sh index 726eb5d25839..c2d66c6284eb 100755 --- a/tools/testing/selftests/net/broadcast_pmtu.sh +++ b/tools/testing/selftests/net/broadcast_pmtu.sh @@ -40,8 +40,14 @@ cleanup() { trap cleanup EXIT setup && - echo "Testing for broadcast route MTU" && - ip net exec "${CLIENT_NS}" ping -f -M want -q -c 1 -s 8000 -w 1 -b "${CLIENT_BROADCAST_ADDRESS}" > /dev/null 2>&1 - -exit $? + echo "Testing for broadcast route MTU" + ping_output=$(ip net exec "${CLIENT_NS}" ping -f -M want -c 1 -s 8000 -w 1 -b \ + "${CLIENT_BROADCAST_ADDRESS}" 2>&1) + if echo "${ping_output}" | grep -q -E "0 packets transmitted|message too long"; then + exit_code=0 + else + exit_code=1 + fi + +exit ${exit_code} base-commit: bbeb83d3182abe0d245318e274e8531e5dd7a948 -- 2.25.1
