netdev - Re: [PATCH 5/8] net: Add skb_gro

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Message-ID: <20081213025246.GA14173@gondor.apana.org.au>
Date:	Sat, 13 Dec 2008 13:52:46 +1100
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Evgeniy Polyakov <johnpol@....mipt.ru>,
	Ben Hutchings <bhutchings@...arflare.com>
Subject: Re: [PATCH 5/8] net: Add skb_gro_receive

On Sat, Dec 13, 2008 at 12:35:23PM +1100, Herbert Xu wrote:
> 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@...dor.apana.org.au>

Looks like I forgot to stop the merging at 64K.  Here is an update
with the check added.

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 2725f4e..2bdb539 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1649,6 +1649,8 @@ extern void	       skb_split(struct sk_buff *skb,
 				 struct sk_buff *skb1, const u32 len);
 
 extern struct sk_buff *skb_segment(struct sk_buff *skb, int features);
+extern int	       skb_gro_receive(struct sk_buff **head,
+				       struct sk_buff *skb);
 
 static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
 				       int len, void *buffer)
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index cf05a8c..88c37a5 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2439,6 +2439,65 @@ 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;
+	unsigned int headroom;
+	unsigned int hlen = p->data - skb_mac_header(p);
+
+	if (hlen + p->len + skb->len >= 65536)
+		return -E2BIG;
+
+	if (skb_shinfo(p)->frag_list)
+		goto merge;
+
+	headroom = skb_headroom(p);
+	nskb = netdev_alloc_skb(p->dev, headroom);
+	if (unlikely(!nskb))
+		return -ENOMEM;
+
+	__copy_skb_header(nskb, p);
+	nskb->mac_len = p->mac_len;
+
+	skb_reserve(nskb, headroom);
+
+	skb_set_mac_header(nskb, -hlen);
+	skb_set_network_header(nskb, skb_network_offset(p));
+	skb_set_transport_header(nskb, skb_transport_offset(p));
+
+	memcpy(skb_mac_header(nskb), skb_mac_header(p), hlen);
+
+	*NAPI_GRO_CB(nskb) = *NAPI_GRO_CB(p);
+	skb_shinfo(nskb)->frag_list = p;
+	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:
+	NAPI_GRO_CB(p)->count++;
+	p->prev->next = skb;
+	p->prev = skb;
+	skb_header_release(skb);
+
+	p->data_len += skb->len;
+	p->truesize += skb->len;
+	p->len += skb->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",

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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