selftests: mptcp: add_addr and echo race test

This patch added an extra test for the singal_address_tests() to do the
ADD_ADDR and ADD_ADDR_ECHO race test.

Co-developed-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn>
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

@@ -1016,6 +1016,21 @@ signal_address_tests()
 	run_tests $ns1 $ns2 10.0.1.1
 	chk_join_nr "signal invalid addresses" 1 1 1
 	chk_add_nr 3 3
+
+	# signal addresses race test
+	reset
+	ip netns exec $ns1 ./pm_nl_ctl limits 4 4
+	ip netns exec $ns2 ./pm_nl_ctl limits 4 4
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.1 flags signal
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.3.1 flags signal
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.4.1 flags signal
+	ip netns exec $ns2 ./pm_nl_ctl add 10.0.1.2 flags signal
+	ip netns exec $ns2 ./pm_nl_ctl add 10.0.2.2 flags signal
+	ip netns exec $ns2 ./pm_nl_ctl add 10.0.3.2 flags signal
+	ip netns exec $ns2 ./pm_nl_ctl add 10.0.4.2 flags signal
+	run_tests $ns1 $ns2 10.0.1.1
+	chk_add_nr 4 4
 }
 
 link_failure_tests()