selftests: mptcp: add subflow limits test-cases

Add and delete a bunch of endpoints and verify the
respect of configured limits.

This covers the codepath introduced by the previous patch.

Fixes: 69c6ce7b ("selftests: mptcp: add implicit endpoint test case")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -1444,6 +1444,33 @@ chk_prio_nr()
 	[ "${dump_stats}" = 1 ] && dump_stats
 }
 
+chk_subflow_nr()
+{
+	local need_title="$1"
+	local msg="$2"
+	local subflow_nr=$3
+	local cnt1
+	local cnt2
+
+	if [ -n "${need_title}" ]; then
+		printf "%03u %-36s %s" "${TEST_COUNT}" "${TEST_NAME}" "${msg}"
+	else
+		printf "%-${nr_blank}s %s" " " "${msg}"
+	fi
+
+	cnt1=$(ss -N $ns1 -tOni | grep -c token)
+	cnt2=$(ss -N $ns2 -tOni | grep -c token)
+	if [ "$cnt1" != "$subflow_nr" -o "$cnt2" != "$subflow_nr" ]; then
+		echo "[fail] got $cnt1:$cnt2 subflows expected $subflow_nr"
+		fail_test
+		dump_stats=1
+	else
+		echo "[ ok ]"
+	fi
+
+	[ "${dump_stats}" = 1 ] && ( ss -N $ns1 -tOni ; ss -N $ns1 -tOni | grep token; ip -n $ns1 mptcp endpoint )
+}
+
 chk_link_usage()
 {
 	local ns=$1
@@ -2556,7 +2583,7 @@ fastclose_tests()
 	fi
 }
 
-implicit_tests()
+endpoint_tests()
 {
 	# userspace pm type prevents add_addr
 	if reset "implicit EP"; then
@@ -2578,6 +2605,23 @@ implicit_tests()
 			$ns2 10.0.2.2 id 1 flags signal
 		wait
 	fi
+
+	if reset "delete and re-add"; then
+		pm_nl_set_limits $ns1 1 1
+		pm_nl_set_limits $ns2 1 1
+		pm_nl_add_endpoint $ns2 10.0.2.2 id 2 dev ns2eth2 flags subflow
+		run_tests $ns1 $ns2 10.0.1.1 4 0 0 slow &
+
+		wait_mpj $ns2
+		pm_nl_del_endpoint $ns2 2 10.0.2.2
+		sleep 0.5
+		chk_subflow_nr needtitle "after delete" 1
+
+		pm_nl_add_endpoint $ns2 10.0.2.2 dev ns2eth2 flags subflow
+		wait_mpj $ns2
+		chk_subflow_nr "" "after re-add" 2
+		wait
+	fi
 }
 
 # [$1: error message]
@@ -2624,7 +2668,7 @@ all_tests_sorted=(
 	d@deny_join_id0_tests
 	m@fullmesh_tests
 	z@fastclose_tests
-	I@implicit_tests
+	I@endpoint_tests
 )
 
 all_tests_args=""