unimore/kernel-hacking-2024-linux-steffo
unimore/kernel-hacking-2024-linux-steffo
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net: skb_segment() provides list head and tail

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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>
This commit is contained in:
Eric Dumazet 2014-10-03 20:59:19 -07:00 committed by David S. Miller
parent 45d9cc7c60
commit bec3cfdca3
2 changed files with 21 additions and 13 deletions
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29
net/core/dev.c
View file

@ -2724,22 +2724,25 @@ struct sk_buff *validate_xmit_skb_list(struct sk_buff *skb, struct net_device *d
{
struct sk_buff *next, *head = NULL, *tail;
while (skb) {
for (; skb != NULL; skb = next) {
next = skb->next;
skb->next = NULL;
skb = validate_xmit_skb(skb, dev);
if (skb) {
struct sk_buff *end = skb;
while (end->next)
end = end->next;
if (!head)
head = skb;
else
tail->next = skb;
tail = end;
}
skb = next;
/* in case skb wont be segmented, point to itself */
skb->prev = skb;
skb = validate_xmit_skb(skb, dev);
if (!skb)
continue;
if (!head)
head = skb;
else
tail->next = skb;
/* If skb was segmented, skb->prev points to
* the last segment. If not, it still contains skb.
*/
tail = skb->prev;
}
return head;
}

5
net/core/skbuff.c
View file

@ -3083,6 +3083,11 @@ struct sk_buff *skb_segment(struct sk_buff *head_skb,
}
} while ((offset += len) < head_skb->len);
/* Some callers want to get the end of the list.
* Put it in segs->prev to avoid walking the list.
* (see validate_xmit_skb_list() for example)
*/
segs->prev = tail;
return segs;
err: