netdev - Re: [PATCH RFC] netfilter: iptables target SYNPROXY

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Date:	Tue, 25 May 2010 13:50:52 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Changli Gao <xiaosuo@...il.com>
cc:	Patrick McHardy <kaber@...sh.net>,
	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH RFC] netfilter: iptables target SYNPROXY


On Tuesday 2010-05-25 13:26, Changli Gao wrote:
>> On Tuesday 2010-05-25 09:06, Changli Gao wrote:
>>> net/ipv4/netfilter/Kconfig                  |   12
>>> net/ipv4/netfilter/Makefile                 |    1
>>> net/ipv4/netfilter/ipt_SYNPROXY.c           |  658 ++++++++++++++++++++++++++++
>>> net/ipv4/syncookies.c                       |   21
>>> net/ipv4/tcp_ipv4.c                         |    5
>>> net/netfilter/nf_conntrack_core.c           |   44 +
>>
>> Please make this an Xtables extension.
>> There is excellent documentation ("Writing Netfilter Modules" to google)
>> on the details if needed.
>
>Hmm. I don't know IPv6 well. So I leave it as an iptables extension,
>and hope sb. comes on with IPv6 support after it gets merged.

This should still be xt even if it does not do ipv6.

>>>+      th = skb_header_pointer(skb, iph->ihl * 4, sizeof(_th), &_th);
>>>+      BUG_ON(th == NULL);
>>
>> I wouldn't call that a bug. I think that can happen on an evil TCP tinygram
>> (with proper IPV4 header).
>
>I copied the code from file nf_conntrack_proto_tcp.c. In fact, BUG_ON
>isn't useful at all, as tcp_error is called before this function
>is called.

Ah I see it hard-depends on nf_conntrack_ipv4 (in Kconfig).
That too could be done instead by using nf_ct_get_l3proto at runtime.
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