From 11a100f844f6096787ab20e19f17d72abc957a8f Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Tue, 8 Jul 2008 15:36:57 -0700 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- include/linux/if_vlan.h | 18 +++--------------- net/8021q/vlan_dev.c | 34 +++++----------------------------- 2 files changed, 8 insertions(+), 44 deletions(-) diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h index d36515dae62f..93f5d9b0e9f9 100644 --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -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. */ diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c index 2ccac6bea57e..b6e52c025fd8 100644 --- a/net/8021q/vlan_dev.c +++ b/net/8021q/vlan_dev.c @@ -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, -- 2.30.2