selftests: mptcp: add explicit test case for remove/readd

Delete and re-create a signal endpoint and ensure that the PM
actually deletes and re-create the subflow.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -3526,6 +3526,35 @@ endpoint_tests()
 		chk_mptcp_info subflows 1 subflows 1
 		mptcp_lib_kill_wait $tests_pid
 	fi
+
+	# remove and re-add
+	if reset "delete re-add signal" &&
+	   mptcp_lib_kallsyms_has "subflow_rebuild_header$"; then
+		pm_nl_set_limits $ns1 1 1
+		pm_nl_set_limits $ns2 1 1
+		pm_nl_add_endpoint $ns1 10.0.2.1 id 1 flags signal
+		test_linkfail=4 speed=20 \
+			run_tests $ns1 $ns2 10.0.1.1 &
+		local tests_pid=$!
+
+		wait_mpj $ns2
+		pm_nl_check_endpoint "creation" \
+			$ns1 10.0.2.1 id 1 flags signal
+		chk_subflow_nr "before delete" 2
+		chk_mptcp_info subflows 1 subflows 1
+
+		pm_nl_del_endpoint $ns1 1 10.0.2.1
+		sleep 0.5
+		chk_subflow_nr "after delete" 1
+		chk_mptcp_info subflows 0 subflows 0
+
+		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
+		wait_mpj $ns2
+		chk_subflow_nr "after re-add" 2
+		chk_mptcp_info subflows 1 subflows 1
+		mptcp_lib_kill_wait $tests_pid
+	fi
+
 }
 
 # [$1: error message]