selftests: mptcp: join: check re-using ID of unused ADD_ADDR

commit a13d5aa upstream.

This test extends "delete re-add signal" to validate the previous
commit. An extra address is announced by the server, but this address
cannot be used by the client. The result is that no subflow will be
established to this address.

Later, the server will delete this extra endpoint, and set a new one,
with a valid address, but re-using the same ID. Before the previous
commit, the server would not have been able to announce this new
address.

While at it, extra checks have been added to validate the expected
numbers of MPJ, ADD_ADDR and RM_ADDR.

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: b6c0838 ("mptcp: remove addr and subflow in PM netlink")
Cc: stable@vger.kernel.org
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://patch.msgid.link/20240819-net-mptcp-pm-reusing-id-v1-2-38035d40de5b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
[ Conflicts in mptcp_join.sh, because the helpers are different in this
  version:
  - run_tests has been modified a few times to reduce the number of
    positional parameters
  - no chk_mptcp_info helper
  - chk_subflow_nr taking an extra parameter
  - kill_tests_wait instead of mptcp_lib_kill_wait ]
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

@@ -3243,23 +3243,31 @@ userspace_tests()
 	# 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_set_limits $ns1 0 2
+		pm_nl_set_limits $ns2 2 2
 		pm_nl_add_endpoint $ns1 10.0.2.1 id 1 flags signal
+		# 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
 		run_tests $ns1 $ns2 10.0.1.1 4 0 0 speed_20 2>/dev/null &
 		local tests_pid=$!
 
 		wait_mpj $ns2
 		chk_subflow_nr needtitle "before delete" 2
 
 		pm_nl_del_endpoint $ns1 1 10.0.2.1
+		pm_nl_del_endpoint $ns1 2 224.0.0.1
 		sleep 0.5
 		chk_subflow_nr "" "after delete" 1
 
-		pm_nl_add_endpoint $ns1 10.0.2.1 flags signal
+		pm_nl_add_endpoint $ns1 10.0.2.1 id 1 flags signal
+		pm_nl_add_endpoint $ns1 10.0.3.1 id 2 flags signal
 		wait_mpj $ns2
-		chk_subflow_nr "" "after re-add" 2
+		chk_subflow_nr "" "after re-add" 3
 		kill_tests_wait
+
+		chk_join_nr 3 3 3
+		chk_add_nr 4 4
+		chk_rm_nr 2 1 invert
 	fi
 
 	# flush and re-add