virtio_net: Fix MAX_PACKET_LEN to support 802.1Q VLANs

[ Upstream commit e918085aaff34086e265f825dd469926b1aec4a4 ]

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 <alex.williamson@hp.com>
Acked-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 0196a0df90210995ec6a5abe228eb23bb22d494c..ce743ecc5d612657cfccabfa37d3e63318a5584c 100644 (file)
--- 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)
 
 struct virtnet_info
 {