selftests: net: fix file owner for broadcast_ether_dst test

Ensure the output file is always owned by root (even if tcpdump was
compiled with `--with-user`), by passing the `-Z root` argument when
invoking it.

Cc: stable@vger.kernel.org
Reported-by: Edoardo Canepa <edoardo.canepa@canonical.com>
Closes: https://bugs.launchpad.net/ubuntu-kernel-tests/+bug/2129815
Fixes: bf59028ea8d4 ("selftests: net: add test for destination in broadcast packets")
Suggested-by: Edoardo Canepa <edoardo.canepa@canonical.com>
Tested-by: Ross Porter <ross.porter@canonical.com>
Signed-off-by: Ross Porter <ross.porter@canonical.com>
Link: https://patch.msgid.link/20260617061039.79717-2-ross.porter@canonical.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/testing/selftests/net/broadcast_ether_dst.sh b/tools/testing/selftests/net/broadcast_ether_dst.sh
index 334a7eca8a803b48ad3d562db83003db0576cf0c..cc571f60742970c47c12239fdef45464bfcd8883 100755 (executable)
--- a/tools/testing/selftests/net/broadcast_ether_dst.sh
+++ b/tools/testing/selftests/net/broadcast_ether_dst.sh
@@ -44,7 +44,7 @@ test_broadcast_ether_dst() {
        # 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 &> "${OUTPUT}" &
+               tcpdump -i link0 -c 1 -w "${CAPFILE}" -Z root icmp &> "${OUTPUT}" &
        pid=$!
        slowwait 1 grep -qs "listening" "${OUTPUT}"