On 2025-08-28 13:42, Oscar Maes wrote:
Add test to check the broadcast ethernet destination field is set correctly.
This test sends a broadcast ping, captures it using tcpdump and ensures that all bits of the 6 octet ethernet destination address are correctly set by examining the output capture file.
Signed-off-by: Oscar Maes oscmaes92@gmail.com Co-authored-by: Brett A C Sheffield bacs@librecast.net
v3 -> v4:
- Added Brett as co-author
- Wait for tcpdump to bind using slowwait
Thanks Oscar.
I've tested the v4 selftest on a kernel with the regression and one without and it looks good.
6.17.0-rc3 Testing ethernet broadcast destination [FAIL] expected dst ether addr to be ff:ff:ff:ff:ff:ff, got 00:11:22:33:44:55
6.17.0-rc3-00002-g329af5eb13d7 (with v3 patch applied) Testing ethernet broadcast destination [ OK ]
Links:
- Discussion: https://lore.kernel.org/netdev/20250822165231.4353-4-bacs@librecast.net/
- Previous version: https://lore.kernel.org/netdev/20250827062322.4807-2-oscmaes92@gmail.com/
Thanks to Brett Sheffield for writing the initial version of this selftest!
tools/testing/selftests/net/Makefile | 1 + .../selftests/net/broadcast_ether_dst.sh | 83 +++++++++++++++++++ 2 files changed, 84 insertions(+) create mode 100755 tools/testing/selftests/net/broadcast_ether_dst.sh
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile index b31a71f2b372..56ad10ea6628 100644 --- a/tools/testing/selftests/net/Makefile +++ b/tools/testing/selftests/net/Makefile @@ -115,6 +115,7 @@ TEST_PROGS += skf_net_off.sh TEST_GEN_FILES += skf_net_off TEST_GEN_FILES += tfo TEST_PROGS += tfo_passive.sh +TEST_PROGS += broadcast_ether_dst.sh TEST_PROGS += broadcast_pmtu.sh TEST_PROGS += ipv6_force_forwarding.sh diff --git a/tools/testing/selftests/net/broadcast_ether_dst.sh b/tools/testing/selftests/net/broadcast_ether_dst.sh new file mode 100755 index 000000000000..334a7eca8a80 --- /dev/null +++ b/tools/testing/selftests/net/broadcast_ether_dst.sh @@ -0,0 +1,83 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0 +# +# Author: Brett A C Sheffield bacs@librecast.net +# Author: Oscar Maes oscmaes92@gmail.com +# +# Ensure destination ethernet field is correctly set for +# broadcast packets
+source lib.sh
+CLIENT_IP4="192.168.0.1" +GW_IP4="192.168.0.2"
+setup() {
- setup_ns CLIENT_NS SERVER_NS
- ip -net "${SERVER_NS}" link add link1 type veth \
peer name link0 netns "${CLIENT_NS}"- ip -net "${CLIENT_NS}" link set link0 up
- ip -net "${CLIENT_NS}" addr add "${CLIENT_IP4}"/24 dev link0
- ip -net "${SERVER_NS}" link set link1 up
- ip -net "${CLIENT_NS}" route add default via "${GW_IP4}"
- ip netns exec "${CLIENT_NS}" arp -s "${GW_IP4}" 00:11:22:33:44:55
+}
+cleanup() {
- rm -f "${CAPFILE}" "${OUTPUT}"
- ip -net "${SERVER_NS}" link del link1
- cleanup_ns "${CLIENT_NS}" "${SERVER_NS}"
+}
+test_broadcast_ether_dst() {
- local rc=0
- CAPFILE=$(mktemp -u cap.XXXXXXXXXX)
- OUTPUT=$(mktemp -u out.XXXXXXXXXX)
- echo "Testing ethernet broadcast destination"
- # start tcpdump listening for icmp
- # tcpdump will exit after receiving a single packet
- # timeout will kill tcpdump if it is still running after 2s
- timeout 2s ip netns exec "${CLIENT_NS}" \
tcpdump -i link0 -c 1 -w "${CAPFILE}" icmp &> "${OUTPUT}" &- pid=$!
- slowwait 1 grep -qs "listening" "${OUTPUT}"
- # send broadcast ping
- ip netns exec "${CLIENT_NS}" \
ping -W0.01 -c1 -b 255.255.255.255 &> /dev/null- # wait for tcpdump for exit after receiving packet
- wait "${pid}"
- # compare ethernet destination field to ff:ff:ff:ff:ff:ff
- ether_dst=$(tcpdump -r "${CAPFILE}" -tnne 2>/dev/null | \
awk '{sub(/,/,"",$3); print $3}')- if [[ "${ether_dst}" == "ff:ff:ff:ff:ff:ff" ]]; then
echo "[ OK ]"rc="${ksft_pass}"- else
echo "[FAIL] expected dst ether addr to be ff:ff:ff:ff:ff:ff," \"got ${ether_dst}"rc="${ksft_fail}"- fi
- return "${rc}"
+}
+if [ ! -x "$(command -v tcpdump)" ]; then
- echo "SKIP: Could not run test without tcpdump tool"
- exit "${ksft_skip}"
+fi
+trap cleanup EXIT
+setup +test_broadcast_ether_dst
+exit $?
2.39.5