[RFC PATCH net-next 24/33] mptcp: selftests: Add capture option

[Mat Martineau <mathew.j.martineau@linux.intel.com>]

Added a "-c" command line option for mptcp_connect.sh to make it easier
to capture packets from each test. The script will use tcpdump to create
one .pcap file per test case, named according to the namespaces,
protocols, and connect address in use. For example, the first test case
writes the capture to ns1-ns1-MPTCP-MPTCP-10.0.1.1.pcap

The stderr output from tcpdump is printed after the test completes to
show tcpdump's "packets dropped by kernel" information.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
---
 .../selftests/net/mptcp/mptcp_connect.sh      | 33 +++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
index e694dc9d312c..4418163af001 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
@@ -7,6 +7,7 @@ sout=""
 cin=""
 cout=""
 ksft_skip=4
+capture=0
 timeout=30
 
 TEST_COUNT=0
@@ -15,12 +16,19 @@ cleanup()
 {
 	rm -f "$cin" "$cout"
 	rm -f "$sin" "$sout"
+	rm -f "$capout"
 
 	for i in 1 2 3 4; do
 		ip netns del ns$i
 	done
 }
 
+for arg in "$@"; do
+    if [ "$arg" = "-c" ]; then
+	capture=1
+    fi
+done
+
 ip -Version > /dev/null 2>&1
 if [ $? -ne 0 ];then
 	echo "SKIP: Could not run test without ip tool"
@@ -31,6 +39,7 @@ sin=$(mktemp)
 sout=$(mktemp)
 cin=$(mktemp)
 cout=$(mktemp)
+capout=$(mktemp)
 trap cleanup EXIT
 
 for i in 1 2 3 4;do
@@ -123,9 +132,25 @@ do_transfer()
 
 	:> "$cout"
 	:> "$sout"
+	:> "$capout"
 
 	printf "%-4s %-5s -> %-4s (%s:%d) %-5s\t" ${connector_ns} ${cl_proto} ${listener_ns} ${connect_addr} ${port} ${srv_proto}
 
+	if [ $capture -eq 1 ]; then
+	    if [ -z $SUDO_USER ] ; then
+		capuser=""
+	    else
+		capuser="-Z $SUDO_USER"
+	    fi
+
+	    capfile="${listener_ns}-${connector_ns}-${cl_proto}-${srv_proto}-${connect_addr}.pcap"
+
+	    ip netns exec ${listener_ns} tcpdump -i any -s 65535 -B 32768 $capuser -w $capfile > "$capout" 2>&1 &
+	    cappid=$!
+
+	    sleep 1
+	fi
+
 	ip netns exec ${listener_ns} ./mptcp_connect -t $timeout -l -p $port -s ${srv_proto} 0.0.0.0 < "$sin" > "$sout" &
 	spid=$!
 
@@ -139,6 +164,11 @@ do_transfer()
 	wait $spid
 	rets=$?
 
+	if [ $capture -eq 1 ]; then
+	    sleep 1
+	    kill $cappid
+	fi
+
 	if [ ${rets} -ne 0 ] || [ ${retc} -ne 0 ]; then
 		echo "[ FAIL ] client exit code $retc, server $rets" 1>&2
 		echo "\nnetns ${listener_ns} socket stat for $port:" 1>&2
@@ -146,6 +176,7 @@ do_transfer()
 		echo "\nnetns ${connector_ns} socket stat for $port:" 1>&2
 		ip netns exec ${connector_ns} ss -nita 1>&2 -o "dport = :$port"
 
+		cat "$capout"
 		return 1
 	fi
 
@@ -156,9 +187,11 @@ do_transfer()
 
 	if [ $retc -eq 0 ] && [ $rets -eq 0 ];then
 		echo "[ OK ]"
+		cat "$capout"
 		return 0
 	fi
 
+	cat "$capout"
 	return 1
 }
 
-- 
2.22.0