Commit 11a100f8 authored by Patrick McHardy's avatar Patrick McHardy Committed by David S. Miller
Browse files

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: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9bb8582e

include/linux/if_vlan.h

+3 −15
Original line number Diff line number Diff line
@@ -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");

	if (skb_cow_head(skb, VLAN_HLEN) < 0) {

		kfree_skb(skb);

		return NULL;

	}

	} else {

		skb = skb_unshare(skb, GFP_ATOMIC);

		if (!skb) {

			printk(KERN_ERR "vlan: failed to unshare skbuff\n");

			return NULL;

		}

	}



	veth = (struct vlan_ethhdr *)skb_push(skb, VLAN_HLEN);



	/* Move the mac addresses to the beginning of the new header. */

net/8021q/vlan_dev.c

+5 −29
Original line number Diff line number Diff line
@@ -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,

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