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Commit eefa3906 authored by Jean Delvare's avatar Jean Delvare Committed by David S. Miller
Browse files

[NET]: Clean up sk_buff walkers. 



I noticed recently that, in skb_checksum(), "offset" and "start" are
essentially the same thing and have the same value throughout the
function, despite being computed differently. Using a single variable
allows some cleanups and makes the skb_checksum() function smaller,
more readable, and presumably marginally faster.

We appear to have many other "sk_buff walker" functions built on the
exact same model, so the cleanup applies to them, too. Here is a list
of the functions I found to be affected:

net/appletalk/ddp.c:atalk_sum_skb()
net/core/datagram.c:skb_copy_datagram_iovec()
net/core/datagram.c:skb_copy_and_csum_datagram()
net/core/skbuff.c:skb_copy_bits()
net/core/skbuff.c:skb_store_bits()
net/core/skbuff.c:skb_checksum()
net/core/skbuff.c:skb_copy_and_csum_bit()
net/core/user_dma.c:dma_skb_copy_datagram_iovec()
net/xfrm/xfrm_algo.c:skb_icv_walk()
net/xfrm/xfrm_algo.c:skb_to_sgvec()

OTOH, I admit I'm a bit surprised, the cleanup is rather obvious so I'm
really wondering if I am missing something. Can anyone please comment
on this?

Signed-off-by: default avatarJean Delvare <jdelvare@suse.de>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 28d8909b

net/appletalk/ddp.c

+9 −16
Original line number Diff line number Diff line
@@ -937,11 +937,11 @@ static unsigned long atalk_sum_partial(const unsigned char *data, 
static unsigned long atalk_sum_skb(const struct sk_buff *skb, int offset,

				   int len, unsigned long sum)

{

	int start = skb_headlen(skb);

	int end = skb_headlen(skb);

	int i, copy;



	/* checksum stuff in header space */

	if ( (copy = start - offset) > 0) {

	if ((copy = end - offset) > 0) {

		if (copy > len)

			copy = len;

		sum = atalk_sum_partial(skb->data + offset, copy, sum);
@@ -953,11 +953,9 @@ static unsigned long atalk_sum_skb(const struct sk_buff *skb, int offset, 


	/* checksum stuff in frags */

	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;



		BUG_TRAP(start <= offset + len);

		BUG_TRAP(len >= 0);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

			u8 *vaddr;

			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -965,36 +963,31 @@ static unsigned long atalk_sum_skb(const struct sk_buff *skb, int offset, 
			if (copy > len)

				copy = len;

			vaddr = kmap_skb_frag(frag);

			sum = atalk_sum_partial(vaddr + frag->page_offset +

						  offset - start, copy, sum);

			sum = atalk_sum_partial(vaddr + frag->page_offset,

						copy, sum);

			kunmap_skb_frag(vaddr);



			if (!(len -= copy))

				return sum;

			offset += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;

			BUG_TRAP(len >= 0);



			BUG_TRAP(start <= offset + len);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				if (copy > len)

					copy = len;

				sum = atalk_sum_skb(list, offset - start,

						    copy, sum);

				sum = atalk_sum_skb(list, 0, copy, sum);

				if ((len -= copy) == 0)

					return sum;

				offset += copy;

			}

			start = end;

		}

	}

net/core/datagram.c

+17 −33
Original line number Diff line number Diff line
@@ -247,8 +247,8 @@ EXPORT_SYMBOL(skb_kill_datagram); 
int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,

			    struct iovec *to, int len)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;

	int end = skb_headlen(skb);

	int i, copy = end - offset;



	/* Copy header. */

	if (copy > 0) {
@@ -263,11 +263,9 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset, 


	/* Copy paged appendix. Hmm... why does this look so complicated? */

	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

			int err;

			u8  *vaddr;
@@ -277,8 +275,8 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset, 
			if (copy > len)

				copy = len;

			vaddr = kmap(page);

			err = memcpy_toiovec(to, vaddr + frag->page_offset +

					     offset - start, copy);

			err = memcpy_toiovec(to, vaddr + frag->page_offset,

					     copy);

			kunmap(page);

			if (err)

				goto fault;
@@ -286,30 +284,24 @@ int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset, 
				return 0;

			offset += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;



			BUG_TRAP(start <= offset + len);

			BUG_TRAP(len >= 0);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				if (copy > len)

					copy = len;

				if (skb_copy_datagram_iovec(list,

							    offset - start,

							    to, copy))

				if (skb_copy_datagram_iovec(list, 0, to, copy))

					goto fault;

				if ((len -= copy) == 0)

					return 0;

				offset += copy;

			}

			start = end;

		}

	}

	if (!len)
@@ -323,9 +315,9 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, 
				      u8 __user *to, int len,

				      __wsum *csump)

{

	int start = skb_headlen(skb);

	int end = skb_headlen(skb);

	int pos = 0;

	int i, copy = start - offset;

	int i, copy = end - offset;



	/* Copy header. */

	if (copy > 0) {
@@ -344,11 +336,9 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, 
	}



	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

			__wsum csum2;

			int err = 0;
@@ -360,8 +350,7 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, 
				copy = len;

			vaddr = kmap(page);

			csum2 = csum_and_copy_to_user(vaddr +

							frag->page_offset +

							offset - start,

							frag->page_offset,

						      to, copy, 0, &err);

			kunmap(page);

			if (err)
@@ -373,24 +362,20 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, 
			to += copy;

			pos += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list=list->next) {

			int end;



			BUG_TRAP(start <= offset + len);

			BUG_TRAP(len >= 0);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				__wsum csum2 = 0;

				if (copy > len)

					copy = len;

				if (skb_copy_and_csum_datagram(list,

							       offset - start,

				if (skb_copy_and_csum_datagram(list, 0,

							       to, copy,

							       &csum2))

					goto fault;
@@ -401,7 +386,6 @@ static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset, 
				to += copy;

				pos += copy;

			}

			start = end;

		}

	}

	if (!len)

net/core/skbuff.c

+43 −79
Original line number Diff line number Diff line
@@ -1045,13 +1045,13 @@ unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta) 
int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len)

{

	int i, copy;

	int start = skb_headlen(skb);

	int end = skb_headlen(skb);



	if (offset > (int)skb->len - len)

		goto fault;



	/* Copy header. */

	if ((copy = start - offset) > 0) {

	if ((copy = end - offset) > 0) {

		if (copy > len)

			copy = len;

		skb_copy_from_linear_data_offset(skb, offset, to, copy);
@@ -1062,11 +1062,9 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len) 
	}



	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;



		BUG_TRAP(start <= offset + len);

		BUG_TRAP(len >= 0);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

			u8 *vaddr;
@@ -1075,8 +1073,8 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len) 


			vaddr = kmap_skb_frag(&skb_shinfo(skb)->frags[i]);

			memcpy(to,

			       vaddr + skb_shinfo(skb)->frags[i].page_offset+

			       offset - start, copy);

			       vaddr + skb_shinfo(skb)->frags[i].page_offset,

			       copy);

			kunmap_skb_frag(vaddr);



			if ((len -= copy) == 0)
@@ -1084,30 +1082,25 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len) 
			offset += copy;

			to     += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;

			BUG_TRAP(len >= 0);



			BUG_TRAP(start <= offset + len);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				if (copy > len)

					copy = len;

				if (skb_copy_bits(list, offset - start,

						  to, copy))

				if (skb_copy_bits(list, 0, to, copy))

					goto fault;

				if ((len -= copy) == 0)

					return 0;

				offset += copy;

				to     += copy;

			}

			start = end;

		}

	}

	if (!len)
@@ -1132,12 +1125,12 @@ int skb_copy_bits(const struct sk_buff *skb, int offset, void *to, int len) 
int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len)

{

	int i, copy;

	int start = skb_headlen(skb);

	int end = skb_headlen(skb);



	if (offset > (int)skb->len - len)

		goto fault;



	if ((copy = start - offset) > 0) {

	if ((copy = end - offset) > 0) {

		if (copy > len)

			copy = len;

		skb_copy_to_linear_data_offset(skb, offset, from, copy);
@@ -1149,11 +1142,9 @@ int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len) 


	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

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

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + frag->size;

		end = offset + frag->size;

		if ((copy = end - offset) > 0) {

			u8 *vaddr;
@@ -1161,8 +1152,7 @@ int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len) 
				copy = len;



			vaddr = kmap_skb_frag(frag);

			memcpy(vaddr + frag->page_offset + offset - start,

			       from, copy);

			memcpy(vaddr + frag->page_offset, from, copy);

			kunmap_skb_frag(vaddr);



			if ((len -= copy) == 0)
@@ -1170,30 +1160,25 @@ int skb_store_bits(struct sk_buff *skb, int offset, const void *from, int len) 
			offset += copy;

			from += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;



			BUG_TRAP(start <= offset + len);

			BUG_TRAP(len >= 0);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				if (copy > len)

					copy = len;

				if (skb_store_bits(list, offset - start,

						   from, copy))

				if (skb_store_bits(list, 0, from, copy))

					goto fault;

				if ((len -= copy) == 0)

					return 0;

				offset += copy;

				from += copy;

			}

			start = end;

		}

	}

	if (!len)
@@ -1210,8 +1195,8 @@ EXPORT_SYMBOL(skb_store_bits); 
__wsum skb_checksum(const struct sk_buff *skb, int offset,

			  int len, __wsum csum)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;

	int end = skb_headlen(skb);

	int i, copy = end - offset;

	int pos = 0;



	/* Checksum header. */
@@ -1226,11 +1211,9 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 
	}



	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

			__wsum csum2;

			u8 *vaddr;
@@ -1239,8 +1222,8 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 
			if (copy > len)

				copy = len;

			vaddr = kmap_skb_frag(frag);

			csum2 = csum_partial(vaddr + frag->page_offset +

					     offset - start, copy, 0);

			csum2 = csum_partial(vaddr + frag->page_offset,

					     copy, 0);

			kunmap_skb_frag(vaddr);

			csum = csum_block_add(csum, csum2, pos);

			if (!(len -= copy))
@@ -1248,31 +1231,26 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 
			offset += copy;

			pos    += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;

			BUG_TRAP(len >= 0);



			BUG_TRAP(start <= offset + len);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				__wsum csum2;

				if (copy > len)

					copy = len;

				csum2 = skb_checksum(list, offset - start,

						     copy, 0);

				csum2 = skb_checksum(list, 0, copy, 0);

				csum = csum_block_add(csum, csum2, pos);

				if ((len -= copy) == 0)

					return csum;

				offset += copy;

				pos    += copy;

			}

			start = end;

		}

	}

	BUG_ON(len);
@@ -1285,8 +1263,8 @@ __wsum skb_checksum(const struct sk_buff *skb, int offset, 
__wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,

				    u8 *to, int len, __wsum csum)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;

	int end = skb_headlen(skb);

	int i, copy = end - offset;

	int pos = 0;



	/* Copy header. */
@@ -1303,11 +1281,9 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, 
	}



	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

			__wsum csum2;

			u8 *vaddr;
@@ -1317,9 +1293,8 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, 
				copy = len;

			vaddr = kmap_skb_frag(frag);

			csum2 = csum_partial_copy_nocheck(vaddr +

							  frag->page_offset +

							  offset - start, to,

							  copy, 0);

							  frag->page_offset,

							  to, copy, 0);

			kunmap_skb_frag(vaddr);

			csum = csum_block_add(csum, csum2, pos);

			if (!(len -= copy))
@@ -1328,7 +1303,6 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, 
			to     += copy;

			pos    += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {
@@ -1336,16 +1310,13 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, 


		for (; list; list = list->next) {

			__wsum csum2;

			int end;



			BUG_TRAP(start <= offset + len);

			BUG_TRAP(len >= 0);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				if (copy > len)

					copy = len;

				csum2 = skb_copy_and_csum_bits(list,

							       offset - start,

				csum2 = skb_copy_and_csum_bits(list, 0,

							       to, copy, 0);

				csum = csum_block_add(csum, csum2, pos);

				if ((len -= copy) == 0)
@@ -1354,7 +1325,6 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset, 
				to     += copy;

				pos    += copy;

			}

			start = end;

		}

	}

	BUG_ON(len);
@@ -2026,8 +1996,8 @@ void __init skb_init(void) 
int

skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;

	int end = skb_headlen(skb);

	int i, copy = end - offset;

	int elt = 0;



	if (copy > 0) {
@@ -2043,45 +2013,39 @@ skb_to_sgvec(struct sk_buff *skb, struct scatterlist *sg, int offset, int len) 
	}



	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

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



			if (copy > len)

				copy = len;

			sg[elt].page = frag->page;

			sg[elt].offset = frag->page_offset+offset-start;

			sg[elt].offset = frag->page_offset;

			sg[elt].length = copy;

			elt++;

			if (!(len -= copy))

				return elt;

			offset += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;



			BUG_TRAP(start <= offset + len);

			BUG_TRAP(len >= 0);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				if (copy > len)

					copy = len;

				elt += skb_to_sgvec(list, sg+elt, offset - start, copy);

				elt += skb_to_sgvec(list, sg+elt, 0, copy);

				if ((len -= copy) == 0)

					return elt;

				offset += copy;

			}

			start = end;

		}

	}

	BUG_ON(len);

net/core/user_dma.c

+9 −16
Original line number Diff line number Diff line
@@ -49,8 +49,8 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan, 
			struct sk_buff *skb, int offset, struct iovec *to,

			size_t len, struct dma_pinned_list *pinned_list)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;

	int end = skb_headlen(skb);

	int i, copy = end - offset;

	dma_cookie_t cookie = 0;



	/* Copy header. */
@@ -69,11 +69,9 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan, 


	/* Copy paged appendix. Hmm... why does this look so complicated? */

	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		copy = end - offset;

		if ((copy = end - offset) > 0) {

			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -82,8 +80,8 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan, 
			if (copy > len)

				copy = len;



			cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list, page,

					frag->page_offset + offset - start, copy);

			cookie = dma_memcpy_pg_to_iovec(chan, to, pinned_list,

					page, frag->page_offset, copy);

			if (cookie < 0)

				goto fault;

			len -= copy;
@@ -91,25 +89,21 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan, 
				goto end;

			offset += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;



			BUG_TRAP(start <= offset + len);

			BUG_TRAP(len >= 0);



			end = start + list->len;

			end = offset + list->len;

			copy = end - offset;

			if (copy > 0) {

				if (copy > len)

					copy = len;

				cookie = dma_skb_copy_datagram_iovec(chan, list,

						offset - start, to, copy,

						pinned_list);

						0, to, copy, pinned_list);

				if (cookie < 0)

					goto fault;

				len -= copy;
@@ -117,7 +111,6 @@ int dma_skb_copy_datagram_iovec(struct dma_chan *chan, 
					goto end;

				offset += copy;

			}

			start = end;

		}

	}

net/xfrm/xfrm_algo.c

+8 −14
Original line number Diff line number Diff line
@@ -532,8 +532,8 @@ EXPORT_SYMBOL_GPL(xfrm_count_enc_supported); 
int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc,

		 int offset, int len, icv_update_fn_t icv_update)

{

	int start = skb_headlen(skb);

	int i, copy = start - offset;

	int end = skb_headlen(skb);

	int i, copy = end - offset;

	int err;

	struct scatterlist sg;
@@ -556,11 +556,9 @@ int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc, 
	}



	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {

		int end;

		BUG_TRAP(len >= 0);



		BUG_TRAP(start <= offset + len);



		end = start + skb_shinfo(skb)->frags[i].size;

		end = offset + skb_shinfo(skb)->frags[i].size;

		if ((copy = end - offset) > 0) {

			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
@@ -568,7 +566,7 @@ int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc, 
				copy = len;



			sg.page = frag->page;

			sg.offset = frag->page_offset + offset-start;

			sg.offset = frag->page_offset;

			sg.length = copy;



			err = icv_update(desc, &sg, copy);
@@ -579,22 +577,19 @@ int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc, 
				return 0;

			offset += copy;

		}

		start = end;

	}



	if (skb_shinfo(skb)->frag_list) {

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



		for (; list; list = list->next) {

			int end;



			BUG_TRAP(start <= offset + len);

			BUG_TRAP(len >= 0);



			end = start + list->len;

			end = offset + list->len;

			if ((copy = end - offset) > 0) {

				if (copy > len)

					copy = len;

				err = skb_icv_walk(list, desc, offset-start,

				err = skb_icv_walk(list, desc, 0,

						   copy, icv_update);

				if (unlikely(err))

					return err;
@@ -602,7 +597,6 @@ int skb_icv_walk(const struct sk_buff *skb, struct hash_desc *desc, 
					return 0;

				offset += copy;

			}

			start = end;

		}

	}

	BUG_ON(len);