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>

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>
Herbert Xu · David S. Miller
1 parent 73cc19f155
Showing 2 changed files with 61 additions and 0 deletions Side-by-side Diff
include/linux/skbuff.h
net/core/skbuff.c
@@ -1687,6 +1687,8 @@
 				 int shiftlen);
  
 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)
@@ -2582,6 +2582,65 @@
  
 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",
...	...	@@ -1687,6 +1687,8 @@
1687	1687	int shiftlen);
1688	1688
1689	1689	extern struct sk_buff skb_segment(struct sk_buff skb, int features);
	1690	+extern int skb_gro_receive(struct sk_buff **head,
	1691	+ struct sk_buff *skb);
1690	1692
1691	1693	static inline void skb_header_pointer(const struct sk_buff skb, int offset,
1692	1694	int len, void *buffer)
...	...	@@ -2582,6 +2582,65 @@
2582	2582
2583	2583	EXPORT_SYMBOL_GPL(skb_segment);
2584	2584
	2585	+int skb_gro_receive(struct sk_buff *head, struct sk_buff skb)
	2586	+{
	2587	+ struct sk_buff p = head;
	2588	+ struct sk_buff *nskb;
	2589	+ unsigned int headroom;
	2590	+ unsigned int hlen = p->data - skb_mac_header(p);
	2591	+
	2592	+ if (hlen + p->len + skb->len >= 65536)
	2593	+ return -E2BIG;
	2594	+
	2595	+ if (skb_shinfo(p)->frag_list)
	2596	+ goto merge;
	2597	+
	2598	+ headroom = skb_headroom(p);
	2599	+ nskb = netdev_alloc_skb(p->dev, headroom);
	2600	+ if (unlikely(!nskb))
	2601	+ return -ENOMEM;
	2602	+
	2603	+ __copy_skb_header(nskb, p);
	2604	+ nskb->mac_len = p->mac_len;
	2605	+
	2606	+ skb_reserve(nskb, headroom);
	2607	+
	2608	+ skb_set_mac_header(nskb, -hlen);
	2609	+ skb_set_network_header(nskb, skb_network_offset(p));
	2610	+ skb_set_transport_header(nskb, skb_transport_offset(p));
	2611	+
	2612	+ memcpy(skb_mac_header(nskb), skb_mac_header(p), hlen);
	2613	+
	2614	+ NAPI_GRO_CB(nskb) = NAPI_GRO_CB(p);
	2615	+ skb_shinfo(nskb)->frag_list = p;
	2616	+ skb_header_release(p);
	2617	+ nskb->prev = p;
	2618	+
	2619	+ nskb->data_len += p->len;
	2620	+ nskb->truesize += p->len;
	2621	+ nskb->len += p->len;
	2622	+
	2623	+ *head = nskb;
	2624	+ nskb->next = p->next;
	2625	+ p->next = NULL;
	2626	+
	2627	+ p = nskb;
	2628	+
	2629	+merge:
	2630	+ NAPI_GRO_CB(p)->count++;
	2631	+ p->prev->next = skb;
	2632	+ p->prev = skb;
	2633	+ skb_header_release(skb);
	2634	+
	2635	+ p->data_len += skb->len;
	2636	+ p->truesize += skb->len;
	2637	+ p->len += skb->len;
	2638	+
	2639	+ NAPI_GRO_CB(skb)->same_flow = 1;
	2640	+ return 0;
	2641	+}
	2642	+EXPORT_SYMBOL_GPL(skb_gro_receive);
	2643	+
2585	2644	void __init skb_init(void)
2586	2645	{
2587	2646	skbuff_head_cache = kmem_cache_create("skbuff_head_cache",