netdev - Re: [PATCH 001/001] QoS and/or fair queueing: Stateless NAT BUG

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Message-Id: <201007091937.17349.rpartearroyo@albentia.com>
Date:	Fri, 9 Jul 2010 19:37:16 +0200
From:	Rodrigo Partearroyo González 
	<rpartearroyo@...entia.com>
To:	"Eric Dumazet" <eric.dumazet@...il.com>
Cc:	"Herbert Xu" <herbert@...dor.apana.org.au>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"Iratxo Pichel Ortiz" <ipichel@...entia.com>,
	Noelia Morón <nmoron@...entia.com>,
	"netdev" <netdev@...r.kernel.org>
Subject: Re: [PATCH 001/001] QoS and/or fair queueing: Stateless NAT BUG

Hi all,
I have been testing Stateless NAT and found that ICMP packets with length
less than 20 bytes were not correctly NAT'ed. I have found a BUG that
makes taking into account IP header length twice, so ICMP packets smaller
than 20 bytes were being dropped.

Proposed formal patch is below, as suggested by Eric Dumazet, thanks.
It is taken from 2.6.34.1 stable version.

Signed-off-by: Rodrigo Partearroyo González <rpartearroyo@...entia.com>
---
diff -uprN a/net/sched/act_nat.c b/net/sched/act_nat.c
--- a/net/sched/act_nat.c	2010-07-09 18:25:18.000000000 +0200
+++ b/net/sched/act_nat.c	2010-07-09 18:26:16.000000000 +0200
@@ -202,7 +202,7 @@ static int tcf_nat(struct sk_buff *skb, 
 	{
 		struct icmphdr *icmph;
 
-		if (!pskb_may_pull(skb, ihl + sizeof(*icmph) + sizeof(*iph)))
+		if (!pskb_may_pull(skb, ihl + sizeof(*icmph)))
 			goto drop;
 
 		icmph = (void *)(skb_network_header(skb) + ihl);
@@ -223,7 +223,7 @@ static int tcf_nat(struct sk_buff *skb, 
 
 		if (skb_cloned(skb) &&
 		    !skb_clone_writable(skb,
-					ihl + sizeof(*icmph) + sizeof(*iph)) &&
+					ihl + sizeof(*icmph)) &&
 		    pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
 			goto drop;

---
Rodrigo Partearroyo González
R&D Engineer

Albentia Systems S.A.
http://www.albentia.com
+34 914400213

C\Margarita Salas 22
Parque Tecnológico de Leganés
Leganés (28918)
Madrid
Spain
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