selftests: forwarding: mirror_lib: skip_hw the VLAN capture

When the VLAN capture is installed on a front panel device and not a
soft device, the packets are counted twice: once in fast path, and once
after they are trapped to the kernel. Resolve the problem by passing
skip_hw flag to vlan_capture_install().

Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -102,7 +102,10 @@ do_test_span_vlan_dir_ips()
 	local ip1=$1; shift
 	local ip2=$1; shift
 
-	vlan_capture_install $dev "vlan_id $vid"
+	# Install the capture as skip_hw to avoid double-counting of packets.
+	# The traffic is meant for local box anyway, so will be trapped to
+	# kernel.
+	vlan_capture_install $dev "skip_hw vlan_id $vid"
 	mirror_test v$h1 $ip1 $ip2 $dev 100 $expect
 	mirror_test v$h2 $ip2 $ip1 $dev 100 $expect
 	vlan_capture_uninstall $dev