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Commit 89319d38 authored by Herbert Xu's avatar Herbert Xu Committed by David S. Miller
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net: Add frag_list support to skb_segment 



This patch adds limited support for handling frag_list packets in
skb_segment.  The intention is to support GRO (Generic Receive Offload)
packets which will be constructed by chaining normal packets using
frag_list.

As such we require all frag_list members terminate on exact MSS
boundaries.  This is checked using BUG_ON.

As there should only be one producer in the kernel of such packets,
namely GRO, this requirement should not be difficult to maintain.

Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent eb14f019

net/core/skbuff.c

+59 −14
Original line number Diff line number Diff line
@@ -2428,6 +2428,7 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features) 
{

	struct sk_buff *segs = NULL;

	struct sk_buff *tail = NULL;

	struct sk_buff *fskb = skb_shinfo(skb)->frag_list;

	unsigned int mss = skb_shinfo(skb)->gso_size;

	unsigned int doffset = skb->data - skb_mac_header(skb);

	unsigned int offset = doffset;
@@ -2447,7 +2448,6 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features) 
		struct sk_buff *nskb;

		skb_frag_t *frag;

		int hsize;

		int k;

		int size;



		len = skb->len - offset;
@@ -2460,10 +2460,37 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features) 
		if (hsize > len || !sg)

			hsize = len;



		nskb = alloc_skb(hsize + doffset + headroom, GFP_ATOMIC);

		if (!hsize && i >= nfrags) {

			BUG_ON(fskb->len != len);



			pos += len;

			nskb = skb_clone(fskb, GFP_ATOMIC);

			fskb = fskb->next;



			if (unlikely(!nskb))

				goto err;



			hsize = skb_end_pointer(nskb) - nskb->head;

			if (skb_cow_head(nskb, doffset + headroom)) {

				kfree_skb(nskb);

				goto err;

			}



			nskb->truesize += skb_end_pointer(nskb) - nskb->head -

					  hsize;

			skb_release_head_state(nskb);

			__skb_push(nskb, doffset);

		} else {

			nskb = alloc_skb(hsize + doffset + headroom,

					 GFP_ATOMIC);



			if (unlikely(!nskb))

				goto err;



			skb_reserve(nskb, headroom);

			__skb_put(nskb, doffset);

		}



		if (segs)

			tail->next = nskb;

		else
@@ -2473,13 +2500,15 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features) 
		__copy_skb_header(nskb, skb);

		nskb->mac_len = skb->mac_len;



		skb_reserve(nskb, headroom);

		skb_reset_mac_header(nskb);

		skb_set_network_header(nskb, skb->mac_len);

		nskb->transport_header = (nskb->network_header +

					  skb_network_header_len(skb));

		skb_copy_from_linear_data(skb, skb_put(nskb, doffset),

					  doffset);

		skb_copy_from_linear_data(skb, nskb->data, doffset);



		if (pos >= offset + len)

			continue;



		if (!sg) {

			nskb->ip_summed = CHECKSUM_NONE;

			nskb->csum = skb_copy_and_csum_bits(skb, offset,
@@ -2489,14 +2518,11 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features) 
		}



		frag = skb_shinfo(nskb)->frags;

		k = 0;



		skb_copy_from_linear_data_offset(skb, offset,

						 skb_put(nskb, hsize), hsize);



		while (pos < offset + len) {

			BUG_ON(i >= nfrags);



		while (pos < offset + len && i < nfrags) {

			*frag = skb_shinfo(skb)->frags[i];

			get_page(frag->page);

			size = frag->size;
@@ -2506,20 +2532,39 @@ struct sk_buff *skb_segment(struct sk_buff *skb, int features) 
				frag->size -= offset - pos;

			}



			k++;

			skb_shinfo(nskb)->nr_frags++;



			if (pos + size <= offset + len) {

				i++;

				pos += size;

			} else {

				frag->size -= pos + size - (offset + len);

				break;

				goto skip_fraglist;

			}



			frag++;

		}



		skb_shinfo(nskb)->nr_frags = k;

		if (pos < offset + len) {

			struct sk_buff *fskb2 = fskb;



			BUG_ON(pos + fskb->len != offset + len);



			pos += fskb->len;

			fskb = fskb->next;



			if (fskb2->next) {

				fskb2 = skb_clone(fskb2, GFP_ATOMIC);

				if (!fskb2)

					goto err;

			} else

				skb_get(fskb2);



			BUG_ON(skb_shinfo(nskb)->frag_list);

			skb_shinfo(nskb)->frag_list = fskb2;

		}



skip_fraglist:

		nskb->data_len = len - hsize;

		nskb->len += nskb->data_len;

		nskb->truesize += nskb->data_len;