flow_dissector: use a 64bit load/store
Le lundi 28 novembre 2011 à 19:06 -0500, David Miller a écrit :
> From: Dimitris Michailidis <dm@chelsio.com>
> Date: Mon, 28 Nov 2011 08:25:39 -0800
>
> >> +bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys
> >> *flow)
> >> +{
> >> + int poff, nhoff = skb_network_offset(skb);
> >> + u8 ip_proto;
> >> + u16 proto = skb->protocol;
> >
> > __be16 instead of u16 for proto?
>
> I'll take care of this when I apply these patches.
( CC trimmed )
Thanks David !
Here is a small patch to use one 64bit load/store on x86_64 instead of
two 32bit load/stores.
[PATCH net-next] flow_dissector: use a 64bit load/store
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 flow_keys (src,dst) 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/core/flow_dissector.c b/net/core/flow_dissector.c
index f0516d9..0985b9b 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -8,6 +8,16 @@
#include <linux/ppp_defs.h>
#include <net/flow_keys.h>
+/* copy saddr & daddr, possibly using 64bit load/store
+ * Equivalent to : flow->src = iph->saddr;
+ * flow->dst = iph->daddr;
+ */
+static void iph_to_flow_copy_addrs(struct flow_keys *flow, const struct iphdr *iph)
+{
+ BUILD_BUG_ON(offsetof(typeof(*flow), dst) !=
+ offsetof(typeof(*flow), src) + sizeof(flow->src));
+ memcpy(&flow->src, &iph->saddr, sizeof(flow->src) + sizeof(flow->dst));
+}
bool skb_flow_dissect(const struct sk_buff *skb, struct flow_keys *flow)
{
@@ -31,8 +41,7 @@
ip_proto = 0;
else
ip_proto = iph->protocol;
- flow->src = iph->saddr;
- flow->dst = iph->daddr;
+ iph_to_flow_copy_addrs(flow, iph);
nhoff += iph->ihl * 4;
break;
}