selftests: mptcp: dump more info on mpjoin errors

Very occasionally, MPTCP selftests fail. Yeah, I saw that at least once!

Here we provide more details in case of errors with mptcp_join.sh script
like it was done with mptcp_connect.sh, see
commit 767389c8dd ("selftests: mptcp: dump more info on errors")

Suggested-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -78,6 +78,7 @@ cleanup_partial()
 
 	for netns in "$ns1" "$ns2"; do
 		ip netns del $netns
+		rm -f /tmp/$netns.{nstat,out}
 	done
 }
 
@@ -233,6 +234,11 @@ do_transfer()
 		sleep 1
 	fi
 
+	NSTAT_HISTORY=/tmp/${listener_ns}.nstat ip netns exec ${listener_ns} \
+		nstat -n
+	NSTAT_HISTORY=/tmp/${connector_ns}.nstat ip netns exec ${connector_ns} \
+		nstat -n
+
 	if [ $speed = "fast" ]; then
 		mptcp_connect="./mptcp_connect -j"
 	elif [ $speed = "slow" ]; then
@@ -383,12 +389,19 @@ do_transfer()
 	    kill $cappid
 	fi
 
+	NSTAT_HISTORY=/tmp/${listener_ns}.nstat ip netns exec ${listener_ns} \
+		nstat | grep Tcp > /tmp/${listener_ns}.out
+	NSTAT_HISTORY=/tmp/${connector_ns}.nstat ip netns exec ${connector_ns} \
+		nstat | grep Tcp > /tmp/${connector_ns}.out
+
 	if [ ${rets} -ne 0 ] || [ ${retc} -ne 0 ]; then
 		echo " client exit code $retc, server $rets" 1>&2
 		echo -e "\nnetns ${listener_ns} socket stat for ${port}:" 1>&2
-		ip netns exec ${listener_ns} ss -nita 1>&2 -o "sport = :$port"
+		ip netns exec ${listener_ns} ss -Menita 1>&2 -o "sport = :$port"
+		cat /tmp/${listener_ns}.out
 		echo -e "\nnetns ${connector_ns} socket stat for ${port}:" 1>&2
-		ip netns exec ${connector_ns} ss -nita 1>&2 -o "dport = :$port"
+		ip netns exec ${connector_ns} ss -Menita 1>&2 -o "dport = :$port"
+		cat /tmp/${connector_ns}.out
 
 		cat "$capout"
 		ret=1