Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=a030847e9f0eed2a080f6114381c649a7aa43d25
Commit: a030847e9f0eed2a080f6114381c649a7aa43d25
Parent: 172a863f2bfbacf4b6bfc06db219b946a058ce1a
Author: Herbert Xu <[EMAIL PROTECTED]>
AuthorDate: Mon Oct 15 01:47:15 2007 -0700
Committer: David S. Miller <[EMAIL PROTECTED]>
CommitDate: Mon Oct 15 12:26:34 2007 -0700
[NET]: Avoid copying TCP packets unnecessarily
TCP packets all have writable heads, that is, even though it's cloned, it is
writable up to the end of the TCP header. This patch makes
skb_checksum_help
aware of this fact by using skb_clone_writable and avoiding a copy for TCP.
I've also modified the BUG_ON tests to be unsigned. The only case where
this
makes a difference is if csum_start points to a location before skb->data.
Since skb->data should always include the header where the checksum field
is (and all currently callers adhere to that), this change is safe and may
uncover bugs later.
Signed-off-by: Herbert Xu <[EMAIL PROTECTED]>
Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
---
net/core/dev.c | 21 ++++++++++-----------
1 files changed, 10 insertions(+), 11 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index 39aba48..38b03da 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1362,22 +1362,21 @@ int skb_checksum_help(struct sk_buff *skb)
goto out_set_summed;
}
- if (skb_cloned(skb)) {
+ offset = skb->csum_start - skb_headroom(skb);
+ BUG_ON(offset >= skb_headlen(skb));
+ csum = skb_checksum(skb, offset, skb->len - offset, 0);
+
+ offset += skb->csum_offset;
+ BUG_ON(offset + sizeof(__sum16) > skb_headlen(skb));
+
+ if (skb_cloned(skb) &&
+ !skb_clone_writable(skb, offset + sizeof(__sum16))) {
ret = pskb_expand_head(skb, 0, 0, GFP_ATOMIC);
if (ret)
goto out;
}
- offset = skb->csum_start - skb_headroom(skb);
- BUG_ON(offset > (int)skb->len);
- csum = skb_checksum(skb, offset, skb->len-offset, 0);
-
- offset = skb_headlen(skb) - offset;
- BUG_ON(offset <= 0);
- BUG_ON(skb->csum_offset + 2 > offset);
-
- *(__sum16 *)(skb->head + skb->csum_start + skb->csum_offset) =
- csum_fold(csum);
+ *(__sum16 *)(skb->data + offset) = csum_fold(csum);
out_set_summed:
skb->ip_summed = CHECKSUM_NONE;
out:
-
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