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>
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@ -185,22 +185,10 @@ static inline struct sk_buff *__vlan_put_tag(struct sk_buff *skb, u16 vlan_tci)
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{
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struct vlan_ethhdr *veth;
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if (skb_headroom(skb) < VLAN_HLEN) {
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struct sk_buff *sk_tmp = skb;
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skb = skb_realloc_headroom(sk_tmp, VLAN_HLEN);
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kfree_skb(sk_tmp);
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if (!skb) {
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printk(KERN_ERR "vlan: failed to realloc headroom\n");
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return NULL;
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}
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} else {
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skb = skb_unshare(skb, GFP_ATOMIC);
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if (!skb) {
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printk(KERN_ERR "vlan: failed to unshare skbuff\n");
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return NULL;
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}
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if (skb_cow_head(skb, VLAN_HLEN) < 0) {
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kfree_skb(skb);
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return NULL;
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}
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veth = (struct vlan_ethhdr *)skb_push(skb, VLAN_HLEN);
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/* Move the mac addresses to the beginning of the new header. */
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@ -74,11 +74,8 @@ static int vlan_dev_rebuild_header(struct sk_buff *skb)
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static inline struct sk_buff *vlan_check_reorder_header(struct sk_buff *skb)
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{
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if (vlan_dev_info(skb->dev)->flags & VLAN_FLAG_REORDER_HDR) {
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if (skb_shared(skb) || skb_cloned(skb)) {
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struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
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kfree_skb(skb);
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skb = nskb;
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}
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if (skb_cow(skb, skb_headroom(skb)) < 0)
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skb = NULL;
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if (skb) {
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/* Lifted from Gleb's VLAN code... */
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memmove(skb->data - ETH_HLEN,
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@ -262,12 +259,14 @@ static int vlan_dev_hard_header(struct sk_buff *skb, struct net_device *dev,
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u16 vlan_tci = 0;
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int rc = 0;
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int build_vlan_header = 0;
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struct net_device *vdev = dev;
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pr_debug("%s: skb: %p type: %hx len: %u vlan_id: %hx, daddr: %p\n",
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__func__, skb, type, len, vlan_dev_info(dev)->vlan_id,
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daddr);
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if (WARN_ON(skb_headroom(skb) < dev->hard_header_len))
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return -ENOSPC;
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/* build vlan header only if re_order_header flag is NOT set. This
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* fixes some programs that get confused when they see a VLAN device
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* sending a frame that is VLAN encoded (the consensus is that the VLAN
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@ -316,29 +315,6 @@ static int vlan_dev_hard_header(struct sk_buff *skb, struct net_device *dev,
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dev = vlan_dev_info(dev)->real_dev;
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/* MPLS can send us skbuffs w/out enough space. This check will grow
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* the skb if it doesn't have enough headroom. Not a beautiful solution,
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* so I'll tick a counter so that users can know it's happening...
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* If they care...
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*/
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/* NOTE: This may still break if the underlying device is not the final
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* device (and thus there are more headers to add...) It should work for
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* good-ole-ethernet though.
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*/
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if (skb_headroom(skb) < dev->hard_header_len) {
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struct sk_buff *sk_tmp = skb;
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skb = skb_realloc_headroom(sk_tmp, dev->hard_header_len);
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kfree_skb(sk_tmp);
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if (skb == NULL) {
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struct net_device_stats *stats = &vdev->stats;
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stats->tx_dropped++;
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return -ENOMEM;
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}
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vlan_dev_info(vdev)->cnt_inc_headroom_on_tx++;
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pr_debug("%s: %s: had to grow skb\n", __func__, vdev->name);
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}
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if (build_vlan_header) {
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/* Now make the underlying real hard header */
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rc = dev_hard_header(skb, dev, ETH_P_8021Q, daddr, saddr,
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