[PATCH net-next 3/3] selftests: net: add coverage for fdb nexthop dst port

@@ -36,6 +36,7 @@ TEST_PROGS := \
 	fib_nexthop_multiprefix.sh \
 	fib_nexthop_nongw.sh \
 	fib_nexthops.sh \
+	fib_nexthops_fdb_port.sh \
 	fib_rule_tests.sh \
 	fib_tests.sh \
 	fin_ack_lat.sh \

@@ -0,0 +1,78 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# Control-plane selftest for per-nexthop VXLAN fdb destination port
+# (NHA_FDB_PORT).  Verifies the accept/reject rules and the dump roundtrip.
+# No datapath traffic here -- see tests/integ/vxlan-fdb-port-integ.sh for the
+# real forwarding test.
+#
+# Requires: patched kernel (NHA_FDB_PORT) and patched iproute2 (the "port"
+# keyword on "ip nexthop ... fdb").  SKIPs cleanly otherwise.
+
+set -u
+
+ksft_skip=4
+NS="nhfdbport-$$"
+IP="ip -netns $NS"
+ret=0
+
+log_test() {	# $1 actual_rc  $2 expected_rc  $3 name
+	if [ "$1" = "$2" ]; then
+		printf "TEST: %-58s [ OK ]\n" "$3"
+	else
+		printf "TEST: %-58s [FAIL] (rc=$1 want=$2)\n" "$3"
+		ret=1
+	fi
+}
+
+# passes (returns 0) iff the command FAILS
+expect_fail() {
+	if "$@" >/dev/null 2>&1; then return 1; else return 0; fi
+}
+
+cleanup() { ip netns del "$NS" 2>/dev/null; }
+
+command -v ip >/dev/null 2>&1 || { echo "SKIP: iproute2 not found"; exit $ksft_skip; }
+ip nexthop help 2>&1 | grep -q fdb || { echo "SKIP: no fdb nexthop support"; exit $ksft_skip; }
+
+trap cleanup EXIT
+cleanup
+ip netns add "$NS" || { echo "SKIP: cannot create netns"; exit $ksft_skip; }
+$IP link set lo up
+
+# Probe for "port" keyword + kernel NHA_FDB_PORT support; SKIP if missing.
+if ! $IP nexthop add id 1 via 10.0.0.1 fdb port 4790 2>/dev/null; then
+	echo "SKIP: 'ip nexthop ... fdb port' unsupported (needs patched kernel + iproute2)"
+	exit $ksft_skip
+fi
+log_test 0 0 "add fdb nexthop with port"
+
+# Dump roundtrip must echo the port back.
+$IP nexthop show id 1 | grep -qw "port 4790"
+log_test $? 0 "dump shows fdb port 4790"
+
+# Reject: port on a routed (non-fdb) nexthop.
+expect_fail $IP nexthop add id 2 via 10.0.0.1 dev lo port 4790
+log_test $? 0 "reject port on non-fdb nexthop"
+
+# Reject: fdb port without a gateway.
+expect_fail $IP nexthop add id 3 fdb port 4790
+log_test $? 0 "reject fdb port without gateway"
+
+# The HA case: a group whose legs share the gateway but differ in port.
+$IP nexthop add id 10 via 10.0.0.1 fdb port 4789 && \
+$IP nexthop add id 11 via 10.0.0.1 fdb port 5789 && \
+$IP nexthop add id 100 group 10/11 fdb
+log_test $? 0 "add fdb nexthop group with differing ports"
+
+# A fdb nexthop without a port must NOT emit one (backward compat).
+$IP nexthop add id 20 via 10.0.0.1 fdb
+$IP nexthop show id 20 | grep -qw "port"
+log_test $? 1 "fdb nexthop without port omits NHA_FDB_PORT"
+
+if [ $ret -eq 0 ]; then
+	echo "PASS: all NHA_FDB_PORT control-plane checks"
+else
+	echo "FAIL: one or more NHA_FDB_PORT checks failed"
+fi
+exit $ret