net: skb_segment() provides list head and tail
Its unfortunate we have to walk again skb list to find the tail after segmentation, even if data is probably hot in cpu caches. skb_segment() can store the tail of the list into segs->prev, and validate_xmit_skb_list() can immediately get the tail. Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -2724,22 +2724,25 @@ struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *d
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{
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struct sk_buff *next, *head = NULL, *tail;
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while (skb) {
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for (; skb != NULL; skb = next) {
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next = skb->next;
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skb->next = NULL;
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skb = validate_xmit_skb(skb, dev);
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if (skb) {
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struct sk_buff *end = skb;
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while (end->next)
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end = end->next;
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if (!head)
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head = skb;
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else
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tail->next = skb;
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tail = end;
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}
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skb = next;
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/* in case skb wont be segmented, point to itself */
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skb->prev = skb;
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skb = validate_xmit_skb(skb, dev);
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if (!skb)
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continue;
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if (!head)
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head = skb;
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else
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tail->next = skb;
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/* If skb was segmented, skb->prev points to
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* the last segment. If not, it still contains skb.
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*/
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tail = skb->prev;
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}
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return head;
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}
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@ -3083,6 +3083,11 @@ perform_csum_check:
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}
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} while ((offset += len) < head_skb->len);
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/* Some callers want to get the end of the list.
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* Put it in segs->prev to avoid walking the list.
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* (see validate_xmit_skb_list() for example)
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*/
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segs->prev = tail;
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return segs;
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err:
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