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Date:	Mon, 19 Oct 2009 21:34:02 +0200
From:	Torsten Schmidt <torsten.schmidt@...06.tu-chemnitz.de>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	Linux Netdev List <netdev@...r.kernel.org>
Subject: [PATCH] IPv4: skip loopback checksums in ip_rcv()

Skip loopback checksum in ip_rcv() for speed optimisation.

Signed-off-by: Torsten Schmidt <schmto@....tu-chemnitz.de>
---
 net/ipv4/ip_input.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 6c98b43..dc72286 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -406,7 +406,7 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
 	 *
 	 *	1.	Length at least the size of an ip header
 	 *	2.	Version of 4
-	 *	3.	Checksums correctly. [Speed optimisation for later, skip loopback checksums]
+	 *	3.	Checksums correctly. [Speed optimisation: skip loopback checksums]
 	 *	4.	Doesn't have a bogus length
 	 */
 
@@ -418,8 +418,9 @@ int ip_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt,
 
 	iph = ip_hdr(skb);
 
-	if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
-		goto inhdr_error;
+	if (!ipv4_is_loopback(iph->daddr))
+		if (unlikely(ip_fast_csum((u8 *)iph, iph->ihl)))
+			goto inhdr_error;
 
 	len = ntohs(iph->tot_len);
 	if (skb->len < len) {
-- 
--
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