ipv6: use skb_expand_head in ip6_xmit

Unlike skb_realloc_headroom, new helper skb_expand_head
does not allocate a new skb if possible.

Additionally this patch replaces commonly used dereferencing with variables.

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 3fa5891..12f985f 100644 (file)
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -249,6 +249,8 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
        const struct ipv6_pinfo *np = inet6_sk(sk);
        struct in6_addr *first_hop = &fl6->daddr;
        struct dst_entry *dst = skb_dst(skb);
+       struct net_device *dev = dst->dev;
+       struct inet6_dev *idev = ip6_dst_idev(dst);
        unsigned int head_room;
        struct ipv6hdr *hdr;
        u8  proto = fl6->flowi6_proto;
@@ -256,22 +258,16 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
        int hlimit = -1;
        u32 mtu;
 
-       head_room = sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dst->dev);
+       head_room = sizeof(struct ipv6hdr) + LL_RESERVED_SPACE(dev);
        if (opt)
                head_room += opt->opt_nflen + opt->opt_flen;
 
-       if (unlikely(skb_headroom(skb) < head_room)) {
-               struct sk_buff *skb2 = skb_realloc_headroom(skb, head_room);
-               if (!skb2) {
-                       IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)),
-                                     IPSTATS_MIB_OUTDISCARDS);
-                       kfree_skb(skb);
+       if (unlikely(head_room > skb_headroom(skb))) {
+               skb = skb_expand_head(skb, head_room);
+               if (!skb) {
+                       IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
                        return -ENOBUFS;
                }
-               if (skb->sk)
-                       skb_set_owner_w(skb2, skb->sk);
-               consume_skb(skb);
-               skb = skb2;
        }
 
        if (opt) {
@@ -313,8 +309,7 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
 
        mtu = dst_mtu(dst);
        if ((skb->len <= mtu) || skb->ignore_df || skb_is_gso(skb)) {
-               IP6_UPD_PO_STATS(net, ip6_dst_idev(skb_dst(skb)),
-                             IPSTATS_MIB_OUT, skb->len);
+               IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUT, skb->len);
 
                /* if egress device is enslaved to an L3 master device pass the
                 * skb to its handler for processing
@@ -327,17 +322,17 @@ int ip6_xmit(const struct sock *sk, struct sk_buff *skb, struct flowi6 *fl6,
                 * we promote our socket to non const
                 */
                return NF_HOOK(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
-                              net, (struct sock *)sk, skb, NULL, dst->dev,
+                              net, (struct sock *)sk, skb, NULL, dev,
                               dst_output);
        }
 
-       skb->dev = dst->dev;
+       skb->dev = dev;
        /* ipv6_local_error() does not require socket lock,
         * we promote our socket to non const
         */
        ipv6_local_error((struct sock *)sk, EMSGSIZE, fl6, mtu);
 
-       IP6_INC_STATS(net, ip6_dst_idev(skb_dst(skb)), IPSTATS_MIB_FRAGFAILS);
+       IP6_INC_STATS(net, idev, IPSTATS_MIB_FRAGFAILS);
        kfree_skb(skb);
        return -EMSGSIZE;
 }