selftests: net: add test for destination in broadcast packets

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>
Link: https://patch.msgid.link/20250902150240.4272-1-oscmaes92@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index c7e03e1d6f63bbba3179000814caf9b32827eee2..2b31d4a93ad7f7ae422583a833f06854b180e318 100644 (file)
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -116,6 +116,7 @@ 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 (executable)
index 0000000..334a7ec
--- /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 $?