From 5b057c6b1a25d57edf2b4d1e956e50936480a9ff Mon Sep 17 00:00:00 2001 From: Herbert Xu Date: Fri, 23 Jun 2006 02:06:41 -0700 Subject: [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 Signed-off-by: David S. Miller --- net/core/skbuff.c | 36 ++++++++++++++++++++++++++---------- 1 file changed, 26 insertions(+), 10 deletions(-) (limited to 'net') diff --git a/net/core/skbuff.c b/net/core/skbuff.c index bb7210f4005..fe63d4efbd4 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. -- cgit v1.2.3