selftests: net: Test bridge backup port when port is administratively down

Test that packets are redirected to the backup port when the primary
port is administratively down.

With the previous patch:

# ./test_bridge_backup_port.sh
[...]
TEST: swp1 administratively down [ OK ]
TEST: No forwarding out of swp1 [ OK ]
TEST: Forwarding out of vx0 [ OK ]
TEST: swp1 administratively up [ OK ]
TEST: Forwarding out of swp1 [ OK ]
TEST: No forwarding out of vx0 [ OK ]
[...]
Tests passed: 89
Tests failed: 0

Without the previous patch:

# ./test_bridge_backup_port.sh
[...]
TEST: swp1 administratively down [ OK ]
TEST: No forwarding out of swp1 [ OK ]
TEST: Forwarding out of vx0 [FAIL]
TEST: swp1 administratively up [ OK ]
TEST: Forwarding out of swp1 [ OK ]
[...]
Tests passed: 85
Tests failed: 4

Signed-off-by: Ido Schimmel <[e-mail]>
Acked-by: Nikolay Aleksandrov <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/test_bridge_backup_port.sh

···
 	tc_check_packets $sw1 "dev vx0 egress" 101 1
 	log_test $? 0 "No forwarding out of vx0"
 
+	# Check that packets are forwarded out of vx0 when swp1 is
+	# administratively down and out of swp1 when it is administratively up
+	# again.
+	run_cmd "ip -n $sw1 link set dev swp1 down"
+	busywait $BUSYWAIT_TIMEOUT bridge_link_check $sw1 swp1 disabled
+	log_test $? 0 "swp1 administratively down"
+
+	run_cmd "ip netns exec $sw1 mausezahn br0.10 -a $smac -b $dmac -A 198.51.100.1 -B 198.51.100.2 -t ip -p 100 -q -c 1"
+	tc_check_packets $sw1 "dev swp1 egress" 101 3
+	log_test $? 0 "No forwarding out of swp1"
+	tc_check_packets $sw1 "dev vx0 egress" 101 2
+	log_test $? 0 "Forwarding out of vx0"
+
+	run_cmd "ip -n $sw1 link set dev swp1 up"
+	busywait $BUSYWAIT_TIMEOUT bridge_link_check $sw1 swp1 forwarding
+	log_test $? 0 "swp1 administratively up"
+
+	run_cmd "ip netns exec $sw1 mausezahn br0.10 -a $smac -b $dmac -A 198.51.100.1 -B 198.51.100.2 -t ip -p 100 -q -c 1"
+	tc_check_packets $sw1 "dev swp1 egress" 101 4
+	log_test $? 0 "Forwarding out of swp1"
+	tc_check_packets $sw1 "dev vx0 egress" 101 2
+	log_test $? 0 "No forwarding out of vx0"
+
 	# Remove vx0 as the backup port of swp1 and check that packets are no
 	# longer forwarded out of vx0 when swp1 does not have a carrier.
 	run_cmd "bridge -n $sw1 link set dev swp1 nobackup_port"
···
 	log_test $? 1 "vx0 not configured as backup port of swp1"
 
 	run_cmd "ip netns exec $sw1 mausezahn br0.10 -a $smac -b $dmac -A 198.51.100.1 -B 198.51.100.2 -t ip -p 100 -q -c 1"
-	tc_check_packets $sw1 "dev swp1 egress" 101 4
+	tc_check_packets $sw1 "dev swp1 egress" 101 5
 	log_test $? 0 "Forwarding out of swp1"
-	tc_check_packets $sw1 "dev vx0 egress" 101 1
+	tc_check_packets $sw1 "dev vx0 egress" 101 2
 	log_test $? 0 "No forwarding out of vx0"
 
 	run_cmd "ip -n $sw1 link set dev swp1 carrier off"
···
 	log_test $? 0 "swp1 carrier off"
 
 	run_cmd "ip netns exec $sw1 mausezahn br0.10 -a $smac -b $dmac -A 198.51.100.1 -B 198.51.100.2 -t ip -p 100 -q -c 1"
-	tc_check_packets $sw1 "dev swp1 egress" 101 4
+	tc_check_packets $sw1 "dev swp1 egress" 101 5
 	log_test $? 0 "No forwarding out of swp1"
-	tc_check_packets $sw1 "dev vx0 egress" 101 1
+	tc_check_packets $sw1 "dev vx0 egress" 101 2
 	log_test $? 0 "No forwarding out of vx0"
 }