From: Eric Dumazet <edumazet@google.com>
Date: Thu, 7 Nov 2013 16:37:28 +0000 (-0800)
Subject: net: flow_dissector: small optimizations in IPv4 dissect
X-Git-Tag: v3.13-rc1~105^2~21
X-Git-Url: http://pileus.org/git/?p=~andy%2Flinux;a=commitdiff_plain;h=3797d3e8462efdaadb64164ca540626b55fe8336

net: flow_dissector: small optimizations in IPv4 dissect

By moving code around, we avoid :

1) A reload of iph->ihl (bit field, so needs a mask)

2) A conditional test (replaced by a conditional mov on x86)
   Fast path loads iph->protocol anyway.

Signed-off-by: Eric Dumazet <edumazet@google.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 0242035192f..d6ef1732250 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -68,13 +68,13 @@ ip:
 		iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
 		if (!iph || iph->ihl < 5)
 			return false;
+		nhoff += iph->ihl * 4;
 
+		ip_proto = iph->protocol;
 		if (ip_is_fragment(iph))
 			ip_proto = 0;
-		else
-			ip_proto = iph->protocol;
+
 		iph_to_flow_copy_addrs(flow, iph);
-		nhoff += iph->ihl * 4;
 		break;
 	}
 	case __constant_htons(ETH_P_IPV6): {