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: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 0bc95f3..0d5e567 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -319,6 +319,20 @@
!(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 @@
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 @@
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;