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.

Co-developed-by: Brett A C Sheffield bacs@librecast.net Signed-off-by: Brett A C Sheffield bacs@librecast.net Signed-off-by: Oscar Maes oscmaes92@gmail.com --- v4 -> v5: - Fixed Signed-off-by chain

v3 -> v4: - Added Brett as co-author - Wait for tcpdump to bind using slowwait

Links: - Discussion: https://lore.kernel.org/netdev/20250822165231.4353-4-bacs@librecast.net/ - Previous version: https://lore.kernel.org/netdev/20250828114242.6433-1-oscmaes92@gmail.com/

Thanks to Brett Sheffield for co-developing 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 $?