selftests: add a test case for mirred egress to ingress

add a selftest that verifies the correct behavior of TC act_mirred egress
to ingress: in particular, it checks if the dst_entry is removed from skb
before redirect egress -> ingress. The correct behavior is: an ICMP 'echo
request' generated by ping will be received and generate a reply the same
way as the one generated by mausezahn.

Suggested-by: Jamal Hadi Salim <[e-mail]>
Signed-off-by: Davide Caratti <[e-mail]>
Acked-by: Cong Wang <[e-mail]>
Reviewed-by: Marcelo Ricardo Leitner <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/testing/selftests/net/forwarding/config

···
 CONFIG_NET_VRF=m
 CONFIG_BPF_SYSCALL=y
 CONFIG_CGROUP_BPF=y
+CONFIG_NET_ACT_CT=m
 CONFIG_NET_ACT_MIRRED=m
 CONFIG_NET_ACT_MPLS=m
 CONFIG_NET_ACT_VLAN=m

tools/testing/selftests/net/forwarding/tc_actions.sh

···
 
 ALL_TESTS="gact_drop_and_ok_test mirred_egress_redirect_test \
 	mirred_egress_mirror_test matchall_mirred_egress_mirror_test \
-	gact_trap_test"
+	gact_trap_test mirred_egress_to_ingress_test"
 NUM_NETIFS=4
 source tc_common.sh
 source lib.sh
···
 h1_create()
 {
 	simple_if_init $h1 192.0.2.1/24
+	tc qdisc add dev $h1 clsact
 }
 
 h1_destroy()
 {
+	tc qdisc del dev $h1 clsact
 	simple_if_fini $h1 192.0.2.1/24
 }
 
···
 	tc filter del dev $swp1 ingress protocol ip pref 1 handle 101 flower
 
 	log_test "trap ($tcflags)"
+}
+
+mirred_egress_to_ingress_test()
+{
+	RET=0
+
+	tc filter add dev $h1 protocol ip pref 100 handle 100 egress flower \
+		ip_proto icmp src_ip 192.0.2.1 dst_ip 192.0.2.2 type 8 action \
+			ct commit nat src addr 192.0.2.2 pipe \
+			ct clear pipe \
+			ct commit nat dst addr 192.0.2.1 pipe \
+			mirred ingress redirect dev $h1
+
+	tc filter add dev $swp1 protocol ip pref 11 handle 111 ingress flower \
+		ip_proto icmp src_ip 192.0.2.1 dst_ip 192.0.2.2 type 8 action drop
+	tc filter add dev $swp1 protocol ip pref 12 handle 112 ingress flower \
+		ip_proto icmp src_ip 192.0.2.1 dst_ip 192.0.2.2 type 0 action pass
+
+	$MZ $h1 -c 1 -p 64 -a $h1mac -b $h2mac -A 192.0.2.1 -B 192.0.2.2 \
+		-t icmp "ping,id=42,seq=10" -q
+
+	tc_check_packets "dev $h1 egress" 100 1
+	check_err $? "didn't mirror first packet"
+
+	tc_check_packets "dev $swp1 ingress" 111 1
+	check_fail $? "didn't redirect first packet"
+	tc_check_packets "dev $swp1 ingress" 112 1
+	check_err $? "didn't receive reply to first packet"
+
+	ping 192.0.2.2 -I$h1 -c1 -w1 -q 1>/dev/null 2>&1
+
+	tc_check_packets "dev $h1 egress" 100 2
+	check_err $? "didn't mirror second packet"
+	tc_check_packets "dev $swp1 ingress" 111 1
+	check_fail $? "didn't redirect second packet"
+	tc_check_packets "dev $swp1 ingress" 112 2
+	check_err $? "didn't receive reply to second packet"
+
+	tc filter del dev $h1 egress protocol ip pref 100 handle 100 flower
+	tc filter del dev $swp1 ingress protocol ip pref 11 handle 111 flower
+	tc filter del dev $swp1 ingress protocol ip pref 12 handle 112 flower
+
+	log_test "mirred_egress_to_ingress ($tcflags)"
 }
 
 setup_prepare()