Add printing support for vsockmon devices.

Print Linux 4.12 vsockmon captures:

  # modprobe vsockmon
  # ip link add type vsockmon
  # ip link set vsockmon0 up
  # tcpdump -i vsockmon0
  16:25:24.987917 VIRTIO 3.1025 > 2.1234 CONNECT, length 76
  16:25:24.987963 VIRTIO 2.1234 > 3.1025 CONNECT, length 76
  16:25:26.568271 VIRTIO 3.1025 > 2.1234 PAYLOAD, length 82
  16:25:26.568512 VIRTIO 2.1234 > 3.1025 CONTROL, length 76
  16:25:28.411335 VIRTIO 3.1025 > 2.1234 DISCONNECT, length 76
  16:25:28.411628 VIRTIO 2.1234 > 3.1025 DISCONNECT, length 76

For more information about vsock see:
http://wiki.qemu.org/Features/VirtioVsock

1 files changed, 3 insertions, 0 deletions

diff --git a/print.c b/print.c
index 21182ba2..44040ecd 100644
--- a/print.c
+++ b/print.c
@@ -234,6 +234,9 @@ static const struct printer printers[] = {
 #ifdef DLT_DSA_TAG_BRCM_PREPEND
 	{ brcm_tag_prepend_if_print, DLT_DSA_TAG_BRCM_PREPEND },
 #endif
+#ifdef DLT_VSOCK
+	{ vsock_if_print,	DLT_VSOCK },
+#endif
 	{ NULL,			0 },
 };