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authorHerbert Xu <herbert@gondor.apana.org.au>2006-06-23 05:06:41 -0400
committerDavid S. Miller <davem@davemloft.net>2006-06-23 05:06:41 -0400
commit5b057c6b1a25d57edf2b4d1e956e50936480a9ff (patch)
treee641febd6f562e0ed1198c160ff353ab513f0612 /net/core
parent5fa21d821f6972e70942f2c555ec29dde962bdb2 (diff)
[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/core')
-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,
781 * filled. Used by network drivers which may DMA or transfer data 781 * filled. Used by network drivers which may DMA or transfer data
782 * beyond the buffer end onto the wire. 782 * beyond the buffer end onto the wire.
783 * 783 *
784 * May return NULL in out of memory cases. 784 * May return error in out of memory cases. The skb is freed on error.
785 */ 785 */
786 786
787struct sk_buff *skb_pad(struct sk_buff *skb, int pad) 787int skb_pad(struct sk_buff *skb, int pad)
788{ 788{
789 struct sk_buff *nskb; 789 int err;
790 int ntail;
790 791
791 /* If the skbuff is non linear tailroom is always zero.. */ 792 /* If the skbuff is non linear tailroom is always zero.. */
792 if (skb_tailroom(skb) >= pad) { 793 if (!skb_cloned(skb) && skb_tailroom(skb) >= pad) {
793 memset(skb->data+skb->len, 0, pad); 794 memset(skb->data+skb->len, 0, pad);
794 return skb; 795 return 0;
795 } 796 }
796 797
797 nskb = skb_copy_expand(skb, skb_headroom(skb), skb_tailroom(skb) + pad, GFP_ATOMIC); 798 ntail = skb->data_len + pad - (skb->end - skb->tail);
799 if (likely(skb_cloned(skb) || ntail > 0)) {
800 err = pskb_expand_head(skb, 0, ntail, GFP_ATOMIC);
801 if (unlikely(err))
802 goto free_skb;
803 }
804
805 /* FIXME: The use of this function with non-linear skb's really needs
806 * to be audited.
807 */
808 err = skb_linearize(skb);
809 if (unlikely(err))
810 goto free_skb;
811
812 memset(skb->data + skb->len, 0, pad);
813 return 0;
814
815free_skb:
798 kfree_skb(skb); 816 kfree_skb(skb);
799 if (nskb) 817 return err;
800 memset(nskb->data+nskb->len, 0, pad);
801 return nskb;
802} 818}
803 819
804/* Trims skb to length len. It can change skb pointers. 820/* Trims skb to length len. It can change skb pointers.