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Subject[PATCH NET v3 3/7] ipv6: use skb_expand_head in ip6_xmit
Date
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>
---
net/ipv6/ip6_output.c | 27 +++++++++++----------------
1 file changed, 11 insertions(+), 16 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 7d2ec25..f91d13a 100644
--- 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;
}
--
1.8.3.1
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