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authorHerbert Xu <herbert@gondor.apana.org.au>2006-06-23 02:06:41 -0700
committerDavid S. Miller <davem@davemloft.net>2006-06-23 02:06:41 -0700
commit5b057c6b1a25d57edf2b4d1e956e50936480a9ff (patch)
treee641febd6f562e0ed1198c160ff353ab513f0612 /net
parentMerge master.kernel.org:/pub/scm/linux/kernel/git/gregkh/usb-2.6 (diff)
downloadlinux-dev-5b057c6b1a25d57edf2b4d1e956e50936480a9ff.tar.xz
linux-dev-5b057c6b1a25d57edf2b4d1e956e50936480a9ff.zip
[NET]: Avoid allocating skb in skb_pad
First of all it is unnecessary to allocate a new skb in skb_pad since the existing one is not shared. More importantly, our hard_start_xmit interface does not allow a new skb to be allocated since that breaks requeueing. This patch uses pskb_expand_head to expand the existing skb and linearize it if needed. Actually, someone should sift through every instance of skb_pad on a non-linear skb as they do not fit the reasons why this was originally created. Incidentally, this fixes a minor bug when the skb is cloned (tcpdump, TCP, etc.). As it is skb_pad will simply write over a cloned skb. Because of the position of the write it is unlikely to cause problems but still it's best if we don't do it. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/core/skbuff.c36
1 files changed, 26 insertions, 10 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index bb7210f4005e..fe63d4efbd4d 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -781,24 +781,40 @@ struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
* filled. Used by network drivers which may DMA or transfer data
* beyond the buffer end onto the wire.
*
- * May return NULL in out of memory cases.
+ * May return error in out of memory cases. The skb is freed on error.
*/
-struct sk_buff *skb_pad(struct sk_buff *skb, int pad)
+int skb_pad(struct sk_buff *skb, int pad)
{
- struct sk_buff *nskb;
+ int err;
+ int ntail;
/* If the skbuff is non linear tailroom is always zero.. */
- if (skb_tailroom(skb) >= pad) {
+ if (!skb_cloned(skb) && skb_tailroom(skb) >= pad) {
memset(skb->data+skb->len, 0, pad);
- return skb;
+ return 0;
}
-
- nskb = skb_copy_expand(skb, skb_headroom(skb), skb_tailroom(skb) + pad, GFP_ATOMIC);
+
+ ntail = skb->data_len + pad - (skb->end - skb->tail);
+ if (likely(skb_cloned(skb) || ntail > 0)) {
+ err = pskb_expand_head(skb, 0, ntail, GFP_ATOMIC);
+ if (unlikely(err))
+ goto free_skb;
+ }
+
+ /* FIXME: The use of this function with non-linear skb's really needs
+ * to be audited.
+ */
+ err = skb_linearize(skb);
+ if (unlikely(err))
+ goto free_skb;
+
+ memset(skb->data + skb->len, 0, pad);
+ return 0;
+
+free_skb:
kfree_skb(skb);
- if (nskb)
- memset(nskb->data+nskb->len, 0, pad);
- return nskb;
+ return err;
}
/* Trims skb to length len. It can change skb pointers.