Subject: [PATCH] virtio_net: Fix MAX_PACKET_LEN to support 802.1Q VLANs

From: Alex Williamson <[email-masked]>
Date: Tue, 20 Jan 2009 09:48:58 -0700

802.1Q expanded the maximum ethernet frame size by 4 bytes for the
VLAN tag.  We're not taking this into account in virtio_net, which
means the buffers we provide to the backend in the virtqueue RX ring
aren't big enough to hold a full MTU VLAN packet.  For QEMU/KVM,
this results in the backend exiting with a packet truncation error.

Signed-off-by: Alex Williamson <[email-masked]>
---

 drivers/net/virtio_net.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 43f6523..63ef2a8 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -24,6 +24,7 @@
 #include <linux/virtio.h>
 #include <linux/virtio_net.h>
 #include <linux/scatterlist.h>
+#include <linux/if_vlan.h>
 
 static int napi_weight = 128;
 module_param(napi_weight, int, 0444);
@@ -33,7 +34,7 @@ module_param(csum, bool, 0444);
 module_param(gso, bool, 0444);
 
 /* FIXME: MTU in config. */
-#define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)
+#define MAX_PACKET_LEN (ETH_HLEN + VLAN_HLEN + ETH_DATA_LEN)
 #define GOOD_COPY_LEN	128
 
 struct virtnet_info