[patch 05/15] virtio_net: Fix skb->csum_start computation

[Greg KH <gregkh@suse.de>]

[-- Attachment #1: virtio_net-fix-skb-csum_start-computation.patch --]
[-- Type: text/plain, Size: 1800 bytes --]


2.6.25-stable review patch.  If anyone has any objections, please let us
know.

------------------
From: Mark McLoughlin <markmc@redhat.com>

commit 23cde76d801246a702e7a84c3fe3d655b35c89a1 upstream.

hdr->csum_start is the offset from the start of the ethernet
header to the transport layer checksum field. skb->csum_start
is the offset from skb->head.

skb_partial_csum_set() assumes that skb->data points to the
ethernet header - i.e. it computes skb->csum_start by adding
the headroom to hdr->csum_start.

Since eth_type_trans() skb_pull()s the ethernet header,
skb_partial_csum_set() should be called before
eth_type_trans().

(Without this patch, GSO packets from a guest to the world outside the
host are corrupted).

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 drivers/net/virtio_net.c |    8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -83,9 +83,7 @@ static void receive_skb(struct net_devic
 	BUG_ON(len > MAX_PACKET_LEN);
 
 	skb_trim(skb, len);
-	skb->protocol = eth_type_trans(skb, dev);
-	pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
-		 ntohs(skb->protocol), skb->len, skb->pkt_type);
+
 	dev->stats.rx_bytes += skb->len;
 	dev->stats.rx_packets++;
 
@@ -95,6 +93,10 @@ static void receive_skb(struct net_devic
 			goto frame_err;
 	}
 
+	skb->protocol = eth_type_trans(skb, dev);
+	pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
+		 ntohs(skb->protocol), skb->len, skb->pkt_type);
+
 	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
 		pr_debug("GSO!\n");
 		switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {

--