linux-kernel - Re: [PATCH v4] tcp: harmonize tcp_vx

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Date:	Wed, 13 Jan 2010 17:03:10 -0800
From:	Joe Perches <joe@...ches.com>
To:	William Allen Simpson <william.allen.simpson@...il.com>,
	Patrick McHardy <kaber@...sh.net>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Linux Kernel Developers <linux-kernel@...r.kernel.org>,
	Linux Kernel Network Developers <netdev@...r.kernel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v4] tcp: harmonize tcp_vx_rcv header length assumptions

On Wed, 2010-01-13 at 16:13 -0500, William Allen Simpson wrote:
> I did today's tests on tcp_ipv4, but part of this harmonization is to
> make v4 and v6 match up better.  As I was examining line by line, one of
> the things that leaps out is that ipv4 has nf_reset(skb):
> 
> tcp_ipv4:
> 	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
> 		goto discard_and_relse;
> 	nf_reset(skb);
> 
> 	if (sk_filter(sk, skb))
> 		goto discard_and_relse;
> 
> tcp_ipv6:
> 	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
> 		goto discard_and_relse;
> 
> 	if (sk_filter(sk, skb))
> 		goto discard_and_relse;
> 
> Does anybody know why?  Should ipv6 have it?  Or at least a comment
> explaining the reasoning for the omission?

You should ask the person that put the line in, but
it might be because no IPv6 NAT support exists.

$ git blame -L 1658,1658 net/ipv4/tcp_ipv4.c
b59c2701 (Patrick McHardy 2006-01-06 23:06:10 -0800 1658)       nf_reset(skb);

And

$ git log -p -1 b59c2701
commit b59c270104f03960069596722fea70340579244d
Author: Patrick McHardy <kaber@...sh.net>
Date:   Fri Jan 6 23:06:10 2006 -0800

    [NETFILTER]: Keep conntrack reference until IPsec policy checks are done
    
    Keep the conntrack reference until policy checks have been performed for
    IPsec NAT support. The reference needs to be dropped before a packet is
    queued to avoid having the conntrack module unloadable.
    
    Signed-off-by: Patrick McHardy <kaber@...sh.net>
    Signed-off-by: David S. Miller <davem@...emloft.net>





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