selftests: forwarding: use proto icmp for {gretap, ip6gretap}_mac testing

For tc ip_proto filter, when we extract the flow via __skb_flow_dissect()
without flag FLOW_DISSECTOR_F_STOP_AT_ENCAP, we will continue extract to
the inner proto.

So for GRE + ICMP messages, we should not track GRE proto, but inner ICMP
proto.

For test mirror_gre.sh, it may make user confused if we capture ICMP
message on $h3(since the flow is GRE message). So I move the capture
dev to h3-gt{4,6}, and only capture ICMP message.

Before the fix:
]# ./mirror_gre.sh
TEST: ingress mirror to gretap (skip_hw) [ OK ]
TEST: egress mirror to gretap (skip_hw) [ OK ]
TEST: ingress mirror to ip6gretap (skip_hw) [ OK ]
TEST: egress mirror to ip6gretap (skip_hw) [ OK ]
TEST: ingress mirror to gretap: envelope MAC (skip_hw) [FAIL]
Expected to capture 10 packets, got 0.
TEST: egress mirror to gretap: envelope MAC (skip_hw) [FAIL]
Expected to capture 10 packets, got 0.
TEST: ingress mirror to ip6gretap: envelope MAC (skip_hw) [FAIL]
Expected to capture 10 packets, got 0.
TEST: egress mirror to ip6gretap: envelope MAC (skip_hw) [FAIL]
Expected to capture 10 packets, got 0.
TEST: two simultaneously configured mirrors (skip_hw) [ OK ]
WARN: Could not test offloaded functionality

After fix:
]# ./mirror_gre.sh
TEST: ingress mirror to gretap (skip_hw) [ OK ]
TEST: egress mirror to gretap (skip_hw) [ OK ]
TEST: ingress mirror to ip6gretap (skip_hw) [ OK ]
TEST: egress mirror to ip6gretap (skip_hw) [ OK ]
TEST: ingress mirror to gretap: envelope MAC (skip_hw) [ OK ]
TEST: egress mirror to gretap: envelope MAC (skip_hw) [ OK ]
TEST: ingress mirror to ip6gretap: envelope MAC (skip_hw) [ OK ]
TEST: egress mirror to ip6gretap: envelope MAC (skip_hw) [ OK ]
TEST: two simultaneously configured mirrors (skip_hw) [ OK ]
WARN: Could not test offloaded functionality

Fixes: ba8d39871a10 ("selftests: forwarding: Add test for mirror to gretap")
Signed-off-by: Hangbin Liu <[e-mail]>
Reviewed-by: Petr Machata <[e-mail]>
Tested-by: Petr Machata <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

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

···
 {
 	local tundev=$1; shift
 	local direction=$1; shift
-	local prot=$1; shift
 	local what=$1; shift
 
-	local swp3mac=$(mac_get $swp3)
-	local h3mac=$(mac_get $h3)
+	case "$direction" in
+	ingress) local src_mac=$(mac_get $h1); local dst_mac=$(mac_get $h2)
+		;;
+	egress) local src_mac=$(mac_get $h2); local dst_mac=$(mac_get $h1)
+		;;
+	esac
 
 	RET=0
 
 	mirror_install $swp1 $direction $tundev "matchall $tcflags"
-	tc filter add dev $h3 ingress pref 77 prot $prot \
-		flower ip_proto 0x2f src_mac $swp3mac dst_mac $h3mac \
-		action pass
+	icmp_capture_install h3-${tundev} "src_mac $src_mac dst_mac $dst_mac"
 
-	mirror_test v$h1 192.0.2.1 192.0.2.2 $h3 77 10
+	mirror_test v$h1 192.0.2.1 192.0.2.2 h3-${tundev} 100 10
 
-	tc filter del dev $h3 ingress pref 77
+	icmp_capture_uninstall h3-${tundev}
 	mirror_uninstall $swp1 $direction
 
 	log_test "$direction $what: envelope MAC ($tcflags)"
···
 
 test_gretap_mac()
 {
-	test_span_gre_mac gt4 ingress ip "mirror to gretap"
-	test_span_gre_mac gt4 egress ip "mirror to gretap"
+	test_span_gre_mac gt4 ingress "mirror to gretap"
+	test_span_gre_mac gt4 egress "mirror to gretap"
 }
 
 test_ip6gretap_mac()
 {
-	test_span_gre_mac gt6 ingress ipv6 "mirror to ip6gretap"
-	test_span_gre_mac gt6 egress ipv6 "mirror to ip6gretap"
+	test_span_gre_mac gt6 ingress "mirror to ip6gretap"
+	test_span_gre_mac gt6 egress "mirror to ip6gretap"
 }
 
 test_all()