[PATCH 6.1.y] selftests: mptcp: join: check re-adding init endp with != id

["Matthieu Baerts (NGI0)" <matttbe@kernel.org>]

commit 1c2326fcae4f0c5de8ad0d734ced43a8e5f17dac upstream.

The initial subflow has a special local ID: 0. It is specific per
connection.

When a global endpoint is deleted and re-added later, it can have a
different ID, but the kernel should still use the ID 0 if it corresponds
to the initial address.

This test validates this behaviour: the endpoint linked to the initial
subflow is removed, and re-added with a different ID.

Note that removing the initial subflow will not decrement the 'subflows'
counters, which corresponds to the *additional* subflows. On the other
hand, when the same endpoint is re-added, it will increment this
counter, as it will be seen as an additional subflow this time.

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: 3ad14f54bd74 ("mptcp: more accurate MPC endpoint tracking")
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>
[ 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>
---
 .../testing/selftests/net/mptcp/mptcp_join.sh | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 57ede4c6af5e..7682a7e2cb51 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -3301,11 +3301,12 @@ endpoint_tests()
 	# remove and re-add
 	if reset "delete re-add signal" &&
 	   mptcp_lib_kallsyms_has "subflow_rebuild_header$"; then
-		pm_nl_set_limits $ns1 0 2
-		pm_nl_set_limits $ns2 2 2
+		pm_nl_set_limits $ns1 0 3
+		pm_nl_set_limits $ns2 3 3
 		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
+		pm_nl_add_endpoint $ns1 10.0.1.1 id 42 flags signal
 		run_tests $ns1 $ns2 10.0.1.1 4 0 0 speed_20 2>/dev/null &
 		local tests_pid=$!
 
@@ -3321,11 +3322,19 @@ endpoint_tests()
 		pm_nl_add_endpoint $ns1 10.0.3.1 id 2 flags signal
 		wait_mpj $ns2
 		chk_subflow_nr "" "after re-add" 3
+
+		pm_nl_del_endpoint $ns1 42 10.0.1.1
+		sleep 0.5
+		chk_subflow_nr "" "after delete ID 0" 2
+
+		pm_nl_add_endpoint $ns1 10.0.1.1 id 99 flags signal
+		wait_mpj $ns2
+		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
+		chk_join_nr 4 4 4
+		chk_add_nr 5 5
+		chk_rm_nr 3 2 invert
 	fi
 
 	# flush and re-add
-- 
2.45.2