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vlan: avoid header copying and linearisation where possible 

- 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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
include/linux/if_vlan.h
View File

@ -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. */

34
net/8021q/vlan_dev.c
View File

@ -74,11 +74,8 @@ static int vlan_dev_rebuild_header(struct sk_buff *skb)
static inline struct sk_buff *vlan_check_reorder_header(struct sk_buff *skb)
{
if (vlan_dev_info(skb->dev)->flags & VLAN_FLAG_REORDER_HDR) {
if (skb_shared(skb) || skb_cloned(skb)) {
struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
kfree_skb(skb);
skb = nskb;
}
if (skb_cow(skb, skb_headroom(skb)) < 0)
skb = NULL;
if (skb) {
/* Lifted from Gleb's VLAN code... */
memmove(skb->data - ETH_HLEN,
@ -262,12 +259,14 @@ static int vlan_dev_hard_header(struct sk_buff *skb, struct net_device *dev,
u16 vlan_tci = 0;
int rc = 0;
int build_vlan_header = 0;
struct net_device *vdev = dev;
pr_debug("%s: skb: %p type: %hx len: %u vlan_id: %hx, daddr: %p\n",
__func__, skb, type, len, vlan_dev_info(dev)->vlan_id,
daddr);
if (WARN_ON(skb_headroom(skb) < dev->hard_header_len))
return -ENOSPC;
/* build vlan header only if re_order_header flag is NOT set. This
* fixes some programs that get confused when they see a VLAN device
* sending a frame that is VLAN encoded (the consensus is that the VLAN
@ -316,29 +315,6 @@ static int vlan_dev_hard_header(struct sk_buff *skb, struct net_device *dev,
dev = vlan_dev_info(dev)->real_dev;
/* MPLS can send us skbuffs w/out enough space. This check will grow
* the skb if it doesn't have enough headroom. Not a beautiful solution,
* so I'll tick a counter so that users can know it's happening...
* If they care...
*/
/* NOTE: This may still break if the underlying device is not the final
* device (and thus there are more headers to add...) It should work for
* good-ole-ethernet though.
*/
if (skb_headroom(skb) < dev->hard_header_len) {
struct sk_buff *sk_tmp = skb;
skb = skb_realloc_headroom(sk_tmp, dev->hard_header_len);
kfree_skb(sk_tmp);
if (skb == NULL) {
struct net_device_stats *stats = &vdev->stats;
stats->tx_dropped++;
return -ENOMEM;
}
vlan_dev_info(vdev)->cnt_inc_headroom_on_tx++;
pr_debug("%s: %s: had to grow skb\n", __func__, vdev->name);
}
if (build_vlan_header) {
/* Now make the underlying real hard header */
rc = dev_hard_header(skb, dev, ETH_P_8021Q, daddr, saddr,