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ipv4: use a 64bit load/store in output path

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gcc compiler is smart enough to use a single load/store if we
memcpy(dptr, sptr, 8) on x86_64, regardless of
CONFIG_CC_OPTIMIZE_FOR_SIZE

In IP header, daddr immediately follows saddr, this wont change in the
future. We only need to make sure our flowi4 (saddr,daddr) fields wont
break the rule.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2011-11-30 19:00:53 +00:00 committed by David S. Miller
parent 898f73585b
commit 84f9307c5d
2 changed files with 21 additions and 5 deletions
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5
include/net/flow.h
View File

@ -59,8 +59,11 @@ struct flowi4 {
#define flowi4_proto __fl_common.flowic_proto
#define flowi4_flags __fl_common.flowic_flags
#define flowi4_secid __fl_common.flowic_secid
__be32 daddr;
/* (saddr,daddr) must be grouped, same order as in IP header */
__be32 saddr;
__be32 daddr;
union flowi_uli uli;
#define fl4_sport uli.ports.sport
#define fl4_dport uli.ports.dport

21
net/ipv4/ip_output.c
View File

@ -319,6 +319,20 @@ int ip_output(struct sk_buff *skb)
!(IPCB(skb)->flags & IPSKB_REROUTED));
}
/*
* copy saddr and daddr, possibly using 64bit load/stores
* Equivalent to :
* iph->saddr = fl4->saddr;
* iph->daddr = fl4->daddr;
*/
static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
{
BUILD_BUG_ON(offsetof(typeof(*fl4), daddr) !=
offsetof(typeof(*fl4), saddr) + sizeof(fl4->saddr));
memcpy(&iph->saddr, &fl4->saddr,
sizeof(fl4->saddr) + sizeof(fl4->daddr));
}
int ip_queue_xmit(struct sk_buff *skb, struct flowi *fl)
{
struct sock *sk = skb->sk;
@ -381,8 +395,8 @@ int ip_queue_xmit(struct sk_buff *skb, struct flowi *fl)
iph->frag_off = 0;
iph->ttl = ip_select_ttl(inet, &rt->dst);
iph->protocol = sk->sk_protocol;
iph->saddr = fl4->saddr;
iph->daddr = fl4->daddr;
ip_copy_addrs(iph, fl4);
/* Transport layer set skb->h.foo itself. */
if (inet_opt && inet_opt->opt.optlen) {
@ -1337,8 +1351,7 @@ struct sk_buff *__ip_make_skb(struct sock *sk,
ip_select_ident(iph, &rt->dst, sk);
iph->ttl = ttl;
iph->protocol = sk->sk_protocol;
iph->saddr = fl4->saddr;
iph->daddr = fl4->daddr;
ip_copy_addrs(iph, fl4);
if (opt) {
iph->ihl += opt->optlen>>2;