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vlan: avoid header copying and linearisation where possible

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- vlan_dev_reorder_header() is only called on the receive path after
  calling skb_share_check(). This means we can use skb_cow() since
  all we need is a writable header.

- vlan_dev_hard_header() includes a work-around for some apparently
  broken out of tree MPLS code. The hard_header functions can expect
  to always have a headroom of at least there own hard_header_len
  available, so the reallocation check is unnecessary.

- __vlan_put_tag() can use skb_cow_head() to avoid the skb_unshare()
  copy when the header is writable.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Patrick McHardy
2008-07-08 15:36:57 -07:00
committed by David S. Miller
parent 9bb8582efb
commit 11a100f844
2 changed files with 8 additions and 44 deletions
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18
include/linux/if_vlan.h
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@@ -185,22 +185,10 @@ static inline struct sk_buff *__vlan_put_tag(struct sk_buff *skb, u16 vlan_tci)
{
struct vlan_ethhdr *veth;
if (skb_headroom(skb) < VLAN_HLEN) {
struct sk_buff *sk_tmp = skb;
skb = skb_realloc_headroom(sk_tmp, VLAN_HLEN);
kfree_skb(sk_tmp);
if (!skb) {
printk(KERN_ERR "vlan: failed to realloc headroom\n");
return NULL;
}
} else {
skb = skb_unshare(skb, GFP_ATOMIC);
if (!skb) {
printk(KERN_ERR "vlan: failed to unshare skbuff\n");
return NULL;
}
if (skb_cow_head(skb, VLAN_HLEN) < 0) {
kfree_skb(skb);
return NULL;
}
veth = (struct vlan_ethhdr *)skb_push(skb, VLAN_HLEN);
/* Move the mac addresses to the beginning of the new header. */