From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Wed, 27 May 2009 15:31:18 +1000
Subject: [net] add skb_gro_receive
Message-id: E1M9BjS-0002C0-Di@gondolin.me.apana.org.au
O-Subject: [PATCH 13/17] net: Add skb_gro_receive
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 skb_gro_receive

This patch adds the helper skb_gro_receive to merge packets for
GRO.  The current method is to allocate a new header skb and then
chain the original packets to its frag_list.  This is done to
make it easier to integrate into the existing GSO framework.

In future as GSO is moved into the drivers, we can undo this and
simply chain the original packets together.

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 8e81912..b9f15d6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -707,6 +707,8 @@ extern int		dev_restart(struct net_device *dev);
 extern int		netpoll_trap(void);
 #endif
 
+extern int	       skb_gro_receive(struct sk_buff **head,
+				       struct sk_buff *skb);
 extern void	       skb_gro_reset_offset(struct sk_buff *skb);
 
 static inline unsigned int skb_gro_offset(const struct sk_buff *skb)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 975369d..6bd609d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2080,6 +2080,112 @@ err:
 }
 EXPORT_SYMBOL_GPL(skb_segment);
 
+int skb_gro_receive(struct sk_buff **head, struct sk_buff *skb)
+{
+	struct sk_buff *p = *head;
+	struct sk_buff *nskb;
+	struct skb_shared_info *skbinfo = skb_shinfo(skb);
+	struct skb_shared_info *pinfo = skb_shinfo(p);
+	unsigned int headroom;
+	unsigned int len = skb_gro_len(skb);
+	unsigned int offset = skb_gro_offset(skb);
+	unsigned int headlen = skb_headlen(skb);
+
+	if (p->len + len >= 65536)
+		return -E2BIG;
+
+	if (pinfo->frag_list)
+		goto merge;
+	else if (headlen <= offset) {
+		skb_frag_t *frag;
+		skb_frag_t *frag2;
+		int i = skbinfo->nr_frags;
+		int nr_frags = pinfo->nr_frags + i;
+
+		offset -= headlen;
+
+		if (nr_frags > MAX_SKB_FRAGS)
+			return -E2BIG;
+
+		pinfo->nr_frags = nr_frags;
+		skbinfo->nr_frags = 0;
+
+		frag = pinfo->frags + nr_frags;
+		frag2 = skbinfo->frags + i;
+		do {
+			*--frag = *--frag2;
+		} while (--i);
+
+		frag->page_offset += offset;
+		frag->size -= offset;
+
+		skb->truesize -= skb->data_len;
+		skb->len -= skb->data_len;
+		skb->data_len = 0;
+
+		NAPI_GRO_CB(skb)->free = 1;
+		goto done;
+	}
+
+	headroom = skb_headroom(p);
+	nskb = netdev_alloc_skb(p->dev, headroom + skb_gro_offset(p));
+	if (unlikely(!nskb))
+		return -ENOMEM;
+
+	__copy_skb_header(nskb, p);
+	nskb->mac_len = p->mac_len;
+
+	skb_reserve(nskb, headroom);
+	__skb_put(nskb, skb_gro_offset(p));
+
+	skb_set_mac_header(nskb, skb_mac_header(p) - p->data);
+	skb_set_network_header(nskb, skb_network_offset(p));
+	skb_set_transport_header(nskb, skb_transport_offset(p));
+
+	__skb_pull(p, skb_gro_offset(p));
+	memcpy(skb_mac_header(nskb), skb_mac_header(p),
+	       p->data - skb_mac_header(p));
+
+	*NAPI_GRO_CB(nskb) = *NAPI_GRO_CB(p);
+	skb_shinfo(nskb)->frag_list = p;
+	skb_shinfo(nskb)->gso_size = pinfo->gso_size;
+	skb_header_release(p);
+	nskb->prev = p;
+
+	nskb->data_len += p->len;
+	nskb->truesize += p->len;
+	nskb->len += p->len;
+
+	*head = nskb;
+	nskb->next = p->next;
+	p->next = NULL;
+
+	p = nskb;
+
+merge:
+	if (offset > headlen) {
+		skbinfo->frags[0].page_offset += offset - headlen;
+		skbinfo->frags[0].size -= offset - headlen;
+		offset = headlen;
+	}
+
+	__skb_pull(skb, offset);
+
+	p->prev->next = skb;
+	p->prev = skb;
+	skb_header_release(skb);
+
+done:
+	NAPI_GRO_CB(p)->count++;
+	p->data_len += len;
+	p->truesize += len;
+	p->len += len;
+
+	NAPI_GRO_CB(skb)->same_flow = 1;
+	return 0;
+}
+EXPORT_SYMBOL_GPL(skb_gro_receive);
+
 void __init skb_init(void)
 {
 	skbuff_head_cache = kmem_cache_create("skbuff_head_cache",