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>
diff --git a/net/core/dev.c b/net/core/dev.c
index 1a90530..7d5691c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2724,22 +2724,25 @@
{
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;
}
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 9a423e2..7b3df0d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3083,6 +3083,11 @@
}
} 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: