selftests: mptcp: make 2nd net namespace use tcp syn cookies unconditionally

check we can establish connections also when syn cookies are in use.

Check that
MPTcpExtMPCapableSYNRX and MPTcpExtMPCapableACKRX increase for each
MPTCP test.

Check TcpExtSyncookiesSent and TcpExtSyncookiesRecv increase in netns2.
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -196,6 +196,9 @@ ip -net "$ns4" link set ns4eth3 up
 ip -net "$ns4" route add default via 10.0.3.2
 ip -net "$ns4" route add default via dead:beef:3::2
 
+# use TCP syn cookies, even if no flooding was detected.
+ip netns exec "$ns2" sysctl -q net.ipv4.tcp_syncookies=2
+
 set_ethtool_flags() {
 	local ns="$1"
 	local dev="$2"
@@ -407,6 +410,11 @@ do_transfer()
 		sleep 1
 	fi
 
+	local stat_synrx_last_l=$(ip netns exec ${listener_ns} nstat -z -a MPTcpExtMPCapableSYNRX | while read a count c rest ;do  echo $count;done)
+	local stat_ackrx_last_l=$(ip netns exec ${listener_ns} nstat -z -a MPTcpExtMPCapableACKRX | while read a count c rest ;do  echo $count;done)
+	local stat_cookietx_last=$(ip netns exec ${listener_ns} nstat -z -a TcpExtSyncookiesSent | while read a count c rest ;do  echo $count;done)
+	local stat_cookierx_last=$(ip netns exec ${listener_ns} nstat -z -a TcpExtSyncookiesRecv | while read a count c rest ;do  echo $count;done)
+
 	ip netns exec ${listener_ns} ./mptcp_connect -t $timeout -l -p $port -s ${srv_proto} $extra_args $local_addr < "$sin" > "$sout" &
 	local spid=$!
 
@@ -450,6 +458,45 @@ do_transfer()
 	check_transfer $cin $sout "file received by server"
 	rets=$?
 
+	local stat_synrx_now_l=$(ip netns exec ${listener_ns} nstat -z -a MPTcpExtMPCapableSYNRX  | while read a count c rest ;do  echo $count;done)
+	local stat_ackrx_now_l=$(ip netns exec ${listener_ns} nstat -z -a MPTcpExtMPCapableACKRX  | while read a count c rest ;do  echo $count;done)
+
+	local stat_cookietx_now=$(ip netns exec ${listener_ns} nstat -z -a TcpExtSyncookiesSent | while read a count c rest ;do  echo $count;done)
+	local stat_cookierx_now=$(ip netns exec ${listener_ns} nstat -z -a TcpExtSyncookiesRecv | while read a count c rest ;do  echo $count;done)
+
+	expect_synrx=$((stat_synrx_last_l))
+	expect_ackrx=$((stat_ackrx_last_l))
+
+	cookies=$(ip netns exec ${listener_ns} sysctl net.ipv4.tcp_syncookies)
+	cookies=${cookies##*=}
+
+	if [ ${cl_proto} = "MPTCP" ] && [ ${srv_proto} = "MPTCP" ]; then
+		expect_synrx=$((stat_synrx_last_l+1))
+		expect_ackrx=$((stat_ackrx_last_l+1))
+	fi
+	if [ $cookies -eq 2 ];then
+		if [ $stat_cookietx_last -ge $stat_cookietx_now ] ;then
+			echo "${listener_ns} CookieSent: ${cl_proto} -> ${srv_proto}: did not advance"
+		fi
+		if [ $stat_cookierx_last -ge $stat_cookierx_now ] ;then
+			echo "${listener_ns} CookieRecv: ${cl_proto} -> ${srv_proto}: did not advance"
+		fi
+	else
+		if [ $stat_cookietx_last -ne $stat_cookietx_now ] ;then
+			echo "${listener_ns} CookieSent: ${cl_proto} -> ${srv_proto}: changed"
+		fi
+		if [ $stat_cookierx_last -ne $stat_cookierx_now ] ;then
+			echo "${listener_ns} CookieRecv: ${cl_proto} -> ${srv_proto}: changed"
+		fi
+	fi
+
+	if [ $expect_synrx -ne $stat_synrx_now_l ] ;then
+		echo "${listener_ns} SYNRX: ${cl_proto} -> ${srv_proto}: expect ${expect_synrx}, got ${stat_synrx_now_l}"
+	fi
+	if [ $expect_ackrx -ne $stat_ackrx_now_l ] ;then
+		echo "${listener_ns} ACKRX: ${cl_proto} -> ${srv_proto}: expect ${expect_synrx}, got ${stat_synrx_now_l}"
+	fi
+
 	if [ $retc -eq 0 ] && [ $rets -eq 0 ];then
 		echo "$duration [ OK ]"
 		cat "$capout"