selftests: mptcp: join: check re-re-adding ID 0 signal

This test extends "delete re-add signal" to validate the previous
commit: when the 'signal' endpoint linked to the initial subflow (ID 0)
is re-added multiple times, it will re-send the ADD_ADDR with id 0. The
client should still be able to re-create this subflow, even if the
add_addr_accepted limit has been reached as this special address is not
considered as a new address.

The 'Fixes' tag here below is the same as the one from the previous
commit: this patch here is not fixing anything wrong in the selftests,
but it validates the previous fix for an issue introduced by this commit
ID.

Fixes: d0876b22 ("mptcp: add the incoming RM_ADDR support")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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

@@ -3688,7 +3688,7 @@ endpoint_tests()
 		# broadcast IP: no packet for this address will be received on ns1
 		pm_nl_add_endpoint $ns1 224.0.0.1 id 2 flags signal
 		pm_nl_add_endpoint $ns1 10.0.1.1 id 42 flags signal
-		test_linkfail=4 speed=20 \
+		test_linkfail=4 speed=5 \
 			run_tests $ns1 $ns2 10.0.1.1 &
 		local tests_pid=$!
 
@@ -3717,7 +3717,17 @@ endpoint_tests()
 
 		pm_nl_add_endpoint $ns1 10.0.1.1 id 99 flags signal
 		wait_mpj $ns2
-		chk_subflow_nr "after re-add" 3
+		chk_subflow_nr "after re-add ID 0" 3
+		chk_mptcp_info subflows 3 subflows 3
+
+		pm_nl_del_endpoint $ns1 99 10.0.1.1
+		sleep 0.5
+		chk_subflow_nr "after re-delete ID 0" 2
+		chk_mptcp_info subflows 2 subflows 2
+
+		pm_nl_add_endpoint $ns1 10.0.1.1 id 88 flags signal
+		wait_mpj $ns2
+		chk_subflow_nr "after re-re-add ID 0" 3
 		chk_mptcp_info subflows 3 subflows 3
 		mptcp_lib_kill_wait $tests_pid
 
@@ -3727,19 +3737,19 @@ endpoint_tests()
 		chk_evt_nr ns1 MPTCP_LIB_EVENT_ESTABLISHED 1
 		chk_evt_nr ns1 MPTCP_LIB_EVENT_ANNOUNCED 0
 		chk_evt_nr ns1 MPTCP_LIB_EVENT_REMOVED 0
-		chk_evt_nr ns1 MPTCP_LIB_EVENT_SUB_ESTABLISHED 4
-		chk_evt_nr ns1 MPTCP_LIB_EVENT_SUB_CLOSED 2
+		chk_evt_nr ns1 MPTCP_LIB_EVENT_SUB_ESTABLISHED 5
+		chk_evt_nr ns1 MPTCP_LIB_EVENT_SUB_CLOSED 3
 
 		chk_evt_nr ns2 MPTCP_LIB_EVENT_CREATED 1
 		chk_evt_nr ns2 MPTCP_LIB_EVENT_ESTABLISHED 1
-		chk_evt_nr ns2 MPTCP_LIB_EVENT_ANNOUNCED 5
-		chk_evt_nr ns2 MPTCP_LIB_EVENT_REMOVED 3
-		chk_evt_nr ns2 MPTCP_LIB_EVENT_SUB_ESTABLISHED 4
-		chk_evt_nr ns2 MPTCP_LIB_EVENT_SUB_CLOSED 2
+		chk_evt_nr ns2 MPTCP_LIB_EVENT_ANNOUNCED 6
+		chk_evt_nr ns2 MPTCP_LIB_EVENT_REMOVED 4
+		chk_evt_nr ns2 MPTCP_LIB_EVENT_SUB_ESTABLISHED 5
+		chk_evt_nr ns2 MPTCP_LIB_EVENT_SUB_CLOSED 3
 
-		chk_join_nr 4 4 4
-		chk_add_nr 5 5
-		chk_rm_nr 3 2 invert
+		chk_join_nr 5 5 5
+		chk_add_nr 6 6
+		chk_rm_nr 4 3 invert
 	fi
 
 	# flush and re-add