Merge branch 'selftests-pmtu-sh-fix-cleanup-of-processes-launched-in-subshell'

Guillaume Nault says:

====================
selftests: pmtu.sh: Fix cleanup of processes launched in subshell.

Depending on the options used, pmtu.sh may launch tcpdump and nettest
processes in the background. However it fails to clean them up after
the tests complete.

Patch 1 allows the cleanup() function to read the list of PIDs launched
by the tests.
Patch 2 fixes the way the nettest PIDs are retrieved.
====================

Link: https://lore.kernel.org/r/cover.1646776561.git.gnault@redhat.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/pmtu.sh

@@ -374,6 +374,16 @@ run_cmd() {
 	return $rc
 }
 
+run_cmd_bg() {
+	cmd="$*"
+
+	if [ "$VERBOSE" = "1" ]; then
+		printf "    COMMAND: %s &\n" "${cmd}"
+	fi
+
+	$cmd 2>&1 &
+}
+
 # Find the auto-generated name for this namespace
 nsname() {
 	eval echo \$NS_$1
@@ -670,10 +680,10 @@ setup_nettest_xfrm() {
 	[ ${1} -eq 6 ] && proto="-6" || proto=""
 	port=${2}
 
-	run_cmd ${ns_a} nettest ${proto} -q -D -s -x -p ${port} -t 5 &
+	run_cmd_bg "${ns_a}" nettest "${proto}" -q -D -s -x -p "${port}" -t 5
 	nettest_pids="${nettest_pids} $!"
 
-	run_cmd ${ns_b} nettest ${proto} -q -D -s -x -p ${port} -t 5 &
+	run_cmd_bg "${ns_b}" nettest "${proto}" -q -D -s -x -p "${port}" -t 5
 	nettest_pids="${nettest_pids} $!"
 }
 
@@ -865,7 +875,6 @@ setup_ovs_bridge() {
 setup() {
 	[ "$(id -u)" -ne 0 ] && echo "  need to run as root" && return $ksft_skip
 
-	cleanup
 	for arg do
 		eval setup_${arg} || { echo "  ${arg} not supported"; return 1; }
 	done
@@ -876,7 +885,7 @@ trace() {
 
 	for arg do
 		[ "${ns_cmd}" = "" ] && ns_cmd="${arg}" && continue
-		${ns_cmd} tcpdump -s 0 -i "${arg}" -w "${name}_${arg}.pcap" 2> /dev/null &
+		${ns_cmd} tcpdump --immediate-mode -s 0 -i "${arg}" -w "${name}_${arg}.pcap" 2> /dev/null &
 		tcpdump_pids="${tcpdump_pids} $!"
 		ns_cmd=
 	done
@@ -1836,6 +1845,10 @@ run_test() {
 
 	unset IFS
 
+	# Since cleanup() relies on variables modified by this subshell, it
+	# has to run in this context.
+	trap cleanup EXIT
+
 	if [ "$VERBOSE" = "1" ]; then
 		printf "\n##########################################################################\n\n"
 	fi