From: Herbert Xu <herbert.xu@redhat.com>
Date: Fri, 5 Jun 2009 07:34:50 +1000
Subject: [net] gso: stop fraglists from escaping
Message-id: 20090604213450.GA4051@gondor.apana.org.au
O-Subject: [RHEL5.4 PATCH] gso: Stop fraglists from escaping
Bugzilla: 499347

RHEL5 bugzilla 499347

On Wed, May 27, 2009 at 03:30:31PM +1000, Herbert Xu wrote:
>
> This series patches adds the core part of GRO to RHEL5.  Generic
> Receive Offload aggregates packets before they're processed by
> the rest of the stack.  This is analagous to GSO which does the
> reverse for transmission.  It allows TCP performance to be greatly
> enhanced at high speeds, in particular, it's crucial for good 10GbE
> performance.

This patch is needed also needed as part of the backport.

gso: Stop fraglists from escaping

As it stands skb fraglists can get past the check in dev_queue_xmit
if the skb is marked as GSO.  In particular, if the packet doesn't
have the proper checksums for GSO, but can otherwise be handled by
the underlying device, we will not perform the fraglist check on it
at all.

If the underlying device cannot handle fraglists, then this will
break.

The fix is as simple as moving the fraglist check from the device
check into skb_gso_ok.

This has caused crashes with Xen when used together with GRO which
can generate GSO packets with fraglists.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index b9f15d6..942977a 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1201,15 +1201,14 @@ static inline int net_gso_ok(int features, int gso_type)
 
 static inline int skb_gso_ok(struct sk_buff *skb, int features)
 {
-	return net_gso_ok(features, skb_shinfo(skb)->gso_type);
+	return net_gso_ok(features, skb_shinfo(skb)->gso_type) &&
+	       (!skb_shinfo(skb)->frag_list || (features & NETIF_F_FRAGLIST));
 }
 
 static inline int netif_needs_gso(struct net_device *dev, struct sk_buff *skb)
 {
 	return skb_is_gso(skb) &&
 	       (!skb_gso_ok(skb, dev->features) ||
-	        (skb_shinfo(skb)->frag_list &&
-	         !(dev->features & NETIF_F_FRAGLIST)) ||
 		unlikely(skb->ip_summed != CHECKSUM_HW));
 }