Since we don't reset the proto_csum_blank flag in the skb, the
checksum calculation gets done twice, which is not twice as good as
once.

With this patch, TCP/UDP checksum errors from dom0 are fixed, and
domUs can use TCP/UDP without turning off TX checksum offload. Normal
non-VLAN bridged configs still work fine, tested with xm-test.

Signed-off-by: Jim Dykman <dykman@us.ibm.com>

     1.1 --- a/linux-2.6-xen-sparse/net/core/dev.c	Fri Apr 14 14:21:12 2006 +0100
     1.2 +++ b/linux-2.6-xen-sparse/net/core/dev.c	Fri Apr 14 14:23:40 2006 +0100
     1.3 @@ -1294,6 +1294,7 @@ int dev_queue_xmit(struct sk_buff *skb)
     1.4  		if ((skb->h.raw + skb->csum + 2) > skb->tail)
     1.5  			goto out_kfree_skb;
     1.6  		skb->ip_summed = CHECKSUM_HW;
     1.7 +		skb->proto_csum_blank = 0;
     1.8  	}
     1.9  #endif
    1.10