unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta)
{
	/* If skb has not enough free space at tail, get new one
	 * plus 128 bytes for future expansions. If we have enough
	 * room at tail, reallocate without expansion only if skb is cloned.
	 */
	int i, k, eat = (skb->tail + delta) - skb->end;

	if (eat > 0 || skb_cloned(skb)) {
		if (pskb_expand_head(skb, 0, eat > 0 ? eat + 128 : 0,
				     GFP_ATOMIC))
			return NULL;
	}

	if (skb_copy_bits(skb, skb_headlen(skb), skb_tail_pointer(skb), delta))
		BUG();

	/* Optimization: no fragments, no reasons to preestimate
	 * size of pulled pages. Superb.
	 */
	if (!skb_has_frag_list(skb))
		goto pull_pages;

	/* Estimate size of pulled pages. */
	eat = delta;
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

		if (size >= eat)
			goto pull_pages;
		eat -= size;
	}

	/* If we need update frag list, we are in troubles.
	 * Certainly, it possible to add an offset to skb data,
	 * but taking into account that pulling is expected to
	 * be very rare operation, it is worth to fight against
	 * further bloating skb head and crucify ourselves here instead.
	 * Pure masohism, indeed. 8)8)
	 */
	if (eat) {
		struct sk_buff *list = skb_shinfo(skb)->frag_list;
		struct sk_buff *clone = NULL;
		struct sk_buff *insp = NULL;

		do {
			BUG_ON(!list);

			if (list->len <= eat) {
				/* Eaten as whole. */
				eat -= list->len;
				list = list->next;
				insp = list;
			} else {
				/* Eaten partially. */

				if (skb_shared(list)) {
					/* Sucks! We need to fork list. :-( */
					clone = skb_clone(list, GFP_ATOMIC);
					if (!clone)
						return NULL;
					insp = list->next;
					list = clone;
				} else {
					/* This may be pulled without
					 * problems. */
					insp = list;
				}
				if (!pskb_pull(list, eat)) {
					kfree_skb(clone);
					return NULL;
				}
				break;
			}
		} while (eat);

		/* Free pulled out fragments. */
		while ((list = skb_shinfo(skb)->frag_list) != insp) {
			skb_shinfo(skb)->frag_list = list->next;
			kfree_skb(list);
		}
		/* And insert new clone at head. */
		if (clone) {
			clone->next = list;
			skb_shinfo(skb)->frag_list = clone;
		}
	}
	/* Success! Now we may commit changes to skb data. */

pull_pages:
	eat = delta;
	k = 0;
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

		if (size <= eat) {
			skb_frag_unref(skb, i);
			eat -= size;
		} else {
			skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
			if (eat) {
				skb_shinfo(skb)->frags[k].page_offset += eat;
				skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
				eat = 0;
			}
			k++;
		}
	}
	skb_shinfo(skb)->nr_frags = k;

	skb->tail     += delta;
	skb->data_len -= delta;

	return skb_tail_pointer(skb);
}
unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta)
{
	 
	int i, k, eat = (skb->tail + delta) - skb->end;

	if (eat > 0 || skb_cloned(skb)) {
		if (pskb_expand_head(skb, 0, eat > 0 ? eat + 128 : 0,
				     GFP_ATOMIC))
			return NULL;
	}

	if (skb_copy_bits(skb, skb_headlen(skb), skb_tail_pointer(skb), delta))
		BUG();

	 
	if (!skb_has_frag_list(skb))
		goto pull_pages;

	 
	eat = delta;
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

		if (size >= eat)
			goto pull_pages;
		eat -= size;
	}

	 
	if (eat) {
		struct sk_buff *list = skb_shinfo(skb)->frag_list;
		struct sk_buff *clone = NULL;
		struct sk_buff *insp = NULL;

		do {
			BUG_ON(!list);

			if (list->len <= eat) {
				 
				eat -= list->len;
				list = list->next;
				insp = list;
			} else {
				 

				if (skb_shared(list)) {
					 
					clone = skb_clone(list, GFP_ATOMIC);
					if (!clone)
						return NULL;
					insp = list->next;
					list = clone;
				} else {
					 
					insp = list;
				}
				if (!pskb_pull(list, eat)) {
					kfree_skb(clone);
					return NULL;
				}
				break;
			}
		} while (eat);

		 
		while ((list = skb_shinfo(skb)->frag_list) != insp) {
			skb_shinfo(skb)->frag_list = list->next;
			kfree_skb(list);
		}
		 
		if (clone) {
			clone->next = list;
			skb_shinfo(skb)->frag_list = clone;
		}
	}
	 

pull_pages:
	eat = delta;
	k = 0;
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		int size = skb_frag_size(&skb_shinfo(skb)->frags[i]);

		if (size <= eat) {
			skb_frag_unref(skb, i);
			eat -= size;
		} else {
			skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
			if (eat) {
				skb_shinfo(skb)->frags[k].page_offset += eat;
				skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat);
				eat = 0;
			}
			k++;
		}
	}
	skb_shinfo(skb)->nr_frags = k;

	skb->tail     += delta;
	skb->data_len -= delta;

	return skb_tail_pointer(skb);
}