aboutsummaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--include/linux/skbuff.h24
-rw-r--r--net/core/skbuff.c2
-rw-r--r--net/netfilter/core.c4
3 files changed, 25 insertions, 5 deletions
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 6f0b2f7d001..881fe80f01d 100644
--- a/include/linux/skbuff.h
+++ b/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 {
@@ -1322,6 +1324,20 @@ static inline struct sk_buff *netdev_alloc_skb(struct net_device *dev,
}
/**
+ * 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
* @headroom: needed headroom
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3943c3ad914..c989c3a0f90 100644
--- a/net/core/skbuff.c
+++ b/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/net/netfilter/core.c b/net/netfilter/core.c
index a84478ee2de..3aaabec70d1 100644
--- a/net/netfilter/core.c
+++ b/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);