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ipv6: use skb_expand_head in ip6_finish_output2

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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>
This commit is contained in:
Vasily Averin 2021-08-02 11:52:22 +03:00 committed by David S. Miller
parent f1260ff15a
commit e415ed3a4b
1 changed files with 16 additions and 35 deletions
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51
net/ipv6/ip6_output.c
View File

@ -60,46 +60,29 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
{
struct dst_entry *dst = skb_dst(skb);
struct net_device *dev = dst->dev;
struct inet6_dev *idev = ip6_dst_idev(dst);
unsigned int hh_len = LL_RESERVED_SPACE(dev);
int delta = hh_len - skb_headroom(skb);
const struct in6_addr *nexthop;
const struct in6_addr *daddr, *nexthop;
struct ipv6hdr *hdr;
struct neighbour *neigh;
int ret;
/* Be paranoid, rather than too clever. */
if (unlikely(delta > 0) && dev->header_ops) {
/* pskb_expand_head() might crash, if skb is shared */
if (skb_shared(skb)) {
struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
if (likely(nskb)) {
if (skb->sk)
skb_set_owner_w(nskb, skb->sk);
consume_skb(skb);
} else {
kfree_skb(skb);
}
skb = nskb;
}
if (skb &&
pskb_expand_head(skb, SKB_DATA_ALIGN(delta), 0, GFP_ATOMIC)) {
kfree_skb(skb);
skb = NULL;
}
if (unlikely(hh_len > skb_headroom(skb)) && dev->header_ops) {
skb = skb_expand_head(skb, hh_len);
if (!skb) {
IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTDISCARDS);
IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTDISCARDS);
return -ENOMEM;
}
}
if (ipv6_addr_is_multicast(&ipv6_hdr(skb)->daddr)) {
struct inet6_dev *idev = ip6_dst_idev(skb_dst(skb));
hdr = ipv6_hdr(skb);
daddr = &hdr->daddr;
if (ipv6_addr_is_multicast(daddr)) {
if (!(dev->flags & IFF_LOOPBACK) && sk_mc_loop(sk) &&
((mroute6_is_socket(net, skb) &&
!(IP6CB(skb)->flags & IP6SKB_FORWARDED)) ||
ipv6_chk_mcast_addr(dev, &ipv6_hdr(skb)->daddr,
&ipv6_hdr(skb)->saddr))) {
ipv6_chk_mcast_addr(dev, daddr, &hdr->saddr))) {
struct sk_buff *newskb = skb_clone(skb, GFP_ATOMIC);
/* Do not check for IFF_ALLMULTI; multicast routing
@ -110,7 +93,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
net, sk, newskb, NULL, newskb->dev,
dev_loopback_xmit);
if (ipv6_hdr(skb)->hop_limit == 0) {
if (hdr->hop_limit == 0) {
IP6_INC_STATS(net, idev,
IPSTATS_MIB_OUTDISCARDS);
kfree_skb(skb);
@ -119,9 +102,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
}
IP6_UPD_PO_STATS(net, idev, IPSTATS_MIB_OUTMCAST, skb->len);
if (IPV6_ADDR_MC_SCOPE(&ipv6_hdr(skb)->daddr) <=
IPV6_ADDR_SCOPE_NODELOCAL &&
if (IPV6_ADDR_MC_SCOPE(daddr) <= IPV6_ADDR_SCOPE_NODELOCAL &&
!(dev->flags & IFF_LOOPBACK)) {
kfree_skb(skb);
return 0;
@ -136,10 +117,10 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
}
rcu_read_lock_bh();
nexthop = rt6_nexthop((struct rt6_info *)dst, &ipv6_hdr(skb)->daddr);
neigh = __ipv6_neigh_lookup_noref(dst->dev, nexthop);
nexthop = rt6_nexthop((struct rt6_info *)dst, daddr);
neigh = __ipv6_neigh_lookup_noref(dev, nexthop);
if (unlikely(!neigh))
neigh = __neigh_create(&nd_tbl, nexthop, dst->dev, false);
neigh = __neigh_create(&nd_tbl, nexthop, dev, false);
if (!IS_ERR(neigh)) {
sock_confirm_neigh(skb, neigh);
ret = neigh_output(neigh, skb, false);
@ -148,7 +129,7 @@ static int ip6_finish_output2(struct net *net, struct sock *sk, struct sk_buff *
}
rcu_read_unlock_bh();
IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
IP6_INC_STATS(net, idev, IPSTATS_MIB_OUTNOROUTES);
kfree_skb(skb);
return -EINVAL;
}