From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Wed, 27 May 2009 15:31:15 +1000
Subject: [net] add frag_list support to GSO
Message-id: E1M9BjP-0002BT-6M@gondolin.me.apana.org.au
O-Subject: [PATCH 10/17] net: Add frag_list support to GSO
Bugzilla: 499347
RH-Acked-by: David Miller <davem@redhat.com>
RH-Acked-by: Neil Horman <nhorman@redhat.com>
RH-Acked-by: Thomas Graf <tgraf@redhat.com>

RHEL5 bugzilla #499347

net: Add frag_list support to GSO

This patch allows GSO to handle frag_list in a limited way for the
purposes of allowing packets merged by GRO to be refragmented on
output.

Most hardware won't (and aren't expected to) support handling GRO
frag_list packets directly.  Therefore we will perform GSO in
software for those cases.

However, for drivers that can support it (such as virtual NICs) we
may not have to segment the packets at all.

Whether the added overhead of GRO/GSO is worthwhile for bridges
and routers when weighed against the benefit of potentially
increasing the MTU within the host is still an open question.
However, for the case of host nodes this is undoubtedly a win.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4e3fd45..75ead01 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1063,6 +1063,8 @@ 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));
 }
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 1e6b1cf..f1819ab 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1244,8 +1244,6 @@ struct sk_buff *skb_gso_segment(struct sk_buff *skb, int features)
 	int type = skb->protocol;
 	int err;
 
-	BUG_ON(skb_shinfo(skb)->frag_list);
-
 	skb->mac.raw = skb->data;
 	skb->mac_len = skb->nh.raw - skb->data;
 	__skb_pull(skb, skb->mac_len);