Commit 84f9307c authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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ipv4: use a 64bit load/store in output path 



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: default avatarEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 898f7358

include/net/flow.h

+4 −1
Original line number Diff line number Diff line
@@ -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

net/ipv4/ip_output.c

+17 −4
Original line number Diff line number Diff line
@@ -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 @@ packet_routed: 
		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;

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