From f11f36e76afcc89b6b16d3889644d4b10dbc3c25 Mon Sep 17 00:00:00 2001
From: Patrick McHardy <kaber@trash.net>
Date: Mon, 25 Jun 2007 04:35:20 -0700
Subject: [PATCH] --- yaml --- r: 58925 b: refs/heads/master c:
 334a8132d9950f769f390f0f35c233d099688e7a h: refs/heads/master i:   58923:
 3ab31f2f8f7fbc62c9dae73222d2d66f0f2b17e5 v: v3

---
 [refs]                       |  2 +-
 trunk/include/linux/skbuff.h | 24 ++++++++++++++++++++----
 trunk/net/core/skbuff.c      |  2 ++
 trunk/net/netfilter/core.c   |  4 +++-
 4 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/[refs] b/[refs]
index cdefc3e926e4..6a1be1753f25 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: e50c41b53d7aa48152dd9c633b04fc7abd536f1f
+refs/heads/master: 334a8132d9950f769f390f0f35c233d099688e7a
diff --git a/trunk/include/linux/skbuff.h b/trunk/include/linux/skbuff.h
index 6f0b2f7d0010..881fe80f01d0 100644
--- a/trunk/include/linux/skbuff.h
+++ b/trunk/include/linux/skbuff.h
@@ -147,8 +147,8 @@ struct skb_shared_info {
 
 /* We divide dataref into two halves.  The higher 16 bits hold references
  * to the payload part of skb->data.  The lower 16 bits hold references to
- * the entire skb->data.  It is up to the users of the skb to agree on
- * where the payload starts.
+ * the entire skb->data.  A clone of a headerless skb holds the length of
+ * the header in skb->hdr_len.
  *
  * All users must obey the rule that the skb->data reference count must be
  * greater than or equal to the payload reference count.
@@ -206,6 +206,7 @@ typedef unsigned char *sk_buff_data_t;
  *	@len: Length of actual data
  *	@data_len: Data length
  *	@mac_len: Length of link layer header
+ *	@hdr_len: writable header length of cloned skb
  *	@csum: Checksum (must include start/offset pair)
  *	@csum_start: Offset from skb->head where checksumming should start
  *	@csum_offset: Offset from csum_start where checksum should be stored
@@ -260,8 +261,9 @@ struct sk_buff {
 	char			cb[48];
 
 	unsigned int		len,
-				data_len,
-				mac_len;
+				data_len;
+	__u16			mac_len,
+				hdr_len;
 	union {
 		__wsum		csum;
 		struct {
@@ -1321,6 +1323,20 @@ static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
 	return __netdev_alloc_skb(dev, length, GFP_ATOMIC);
 }
 
+/**
+ *	skb_clone_writable - is the header of a clone writable
+ *	@skb: buffer to check
+ *	@len: length up to which to write
+ *
+ *	Returns true if modifying the header part of the cloned buffer
+ *	does not requires the data to be copied.
+ */
+static inline int skb_clone_writable(struct sk_buff *skb, int len)
+{
+	return !skb_header_cloned(skb) &&
+	       skb_headroom(skb) + len <= skb->hdr_len;
+}
+
 /**
  *	skb_cow - copy header of skb when it is required
  *	@skb: buffer to cow
diff --git a/trunk/net/core/skbuff.c b/trunk/net/core/skbuff.c
index 3943c3ad9145..c989c3a0f907 100644
--- a/trunk/net/core/skbuff.c
+++ b/trunk/net/core/skbuff.c
@@ -415,6 +415,7 @@ struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 	C(csum);
 	C(local_df);
 	n->cloned = 1;
+	n->hdr_len = skb->nohdr ? skb_headroom(skb) : skb->hdr_len;
 	n->nohdr = 0;
 	C(pkt_type);
 	C(ip_summed);
@@ -676,6 +677,7 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
 	skb->network_header   += off;
 	skb->mac_header	      += off;
 	skb->cloned   = 0;
+	skb->hdr_len  = 0;
 	skb->nohdr    = 0;
 	atomic_set(&skb_shinfo(skb)->dataref, 1);
 	return 0;
diff --git a/trunk/net/netfilter/core.c b/trunk/net/netfilter/core.c
index a84478ee2ded..3aaabec70d19 100644
--- a/trunk/net/netfilter/core.c
+++ b/trunk/net/netfilter/core.c
@@ -203,7 +203,9 @@ int skb_make_writable(struct sk_buff **pskb, unsigned int writable_len)
 		return 0;
 
 	/* Not exclusive use of packet?  Must copy. */
-	if (skb_shared(*pskb) || skb_cloned(*pskb))
+	if (skb_cloned(*pskb) && !skb_clone_writable(*pskb, writable_len))
+		goto copy_skb;
+	if (skb_shared(*pskb))
 		goto copy_skb;
 
 	return pskb_may_pull(*pskb, writable_len);