Squash to "selftests: mptcp: get stats just before timing out"

Geliang reported that mptcp_connect.sh test runtime got increased after
this patch.

That's because the previous 'kill' command was only killing the
background job, but the 'sleep' command was still running.

It is not very clear to me why there was a delay at the end, but
switching to mptcp_lib_kill_group_wait to kill the background job and
the running command fixed the issue. The new code is also looking
clearer I think, so that's good.

Link: https://lore.kernel.org/[email protected]
Signed-off-by: Matthieu Baerts (NGI0) <[email protected]>

Author: matttbe

tools/testing/selftests/net/mptcp/mptcp_connect.sh

@@ -415,7 +415,12 @@ do_transfer()
 	local retc=$?
 	wait $spid
 	local rets=$?
-	kill $timeout_pid 2>/dev/null && timeout_pid=0
+
+	if kill -0 $timeout_pid; then
+		# Finished before the timeout: kill the background job
+		mptcp_lib_kill_group_wait $timeout_pid
+		timeout_pid=0
+	fi
 
 	local stop
 	stop=$(date +%s%3N)

tools/testing/selftests/net/mptcp/mptcp_join.sh

@@ -1063,7 +1063,12 @@ do_transfer()
 	local retc=$?
 	wait $spid
 	local rets=$?
-	kill $timeout_pid 2>/dev/null && timeout_pid=0
+
+	if kill -0 $timeout_pid; then
+		# Finished before the timeout: kill the background job
+		mptcp_lib_kill_group_wait $timeout_pid
+		timeout_pid=0
+	fi
 
 	cond_stop_capture
 

tools/testing/selftests/net/mptcp/mptcp_sockopt.sh

@@ -193,7 +193,12 @@ do_transfer()
 	local retc=$?
 	wait $spid
 	local rets=$?
-	kill $timeout_pid 2>/dev/null && timeout_pid=0
+
+	if kill -0 $timeout_pid; then
+		# Finished before the timeout: kill the background job
+		mptcp_lib_kill_group_wait $timeout_pid
+		timeout_pid=0
+	fi
 
 	mptcp_lib_nstat_get "${listener_ns}"
 	mptcp_lib_nstat_get "${connector_ns}"

tools/testing/selftests/net/mptcp/simult_flows.sh

@@ -178,7 +178,12 @@ do_transfer()
 	local retc=$?
 	wait $spid
 	local rets=$?
-	kill $timeout_pid 2>/dev/null && timeout_pid=0
+
+	if kill -0 $timeout_pid; then
+		# Finished before the timeout: kill the background job
+		mptcp_lib_kill_group_wait $timeout_pid
+		timeout_pid=0
+	fi
 
 	if $capture; then
 		sleep 1