netdev - Re: RFC: netfilter: synproxy iptables target

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Message-ID: <AANLkTimLBc58O4FA2S5wsA0kDD6eP7je_OGapfhPQK1s@mail.gmail.com>
Date:	Thu, 20 May 2010 22:42:25 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Patrick McHardy <kaber@...sh.net>,
	Netfilter Developer Mailing List 
	<netfilter-devel@...r.kernel.org>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: RFC: netfilter: synproxy iptables target

On Thu, May 20, 2010 at 10:32 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le jeudi 20 mai 2010 à 22:21 +0800, Changli Gao a écrit :
>
>>
>> pure synproxy can be used on firewall to protect the internal servers,
>> which don't support neither syncookies and synproxy, from the attack
>> of SYN-flood.
>>
>
> protecting servers using conntracking ?
>
> Thats seems very dangerous to me.

If NAT is needed, conntracking is needed in any way. The conntrack
won't be confirmed until the connection between firewall and client is
established.

>
>> synproxy with defered connection relay acts as a layer 7 proxy, but
>> works in kernel space totally, unlike tcp splice tech., which needs
>> the applications in user space parse the requests, and establish the
>> connections.
>>
>
> In the example given, only non persistent connections are handled...
>
> These days, browsers and servers dont establish one socket per http
> request...
>
>

Yea. But some users still use non persistent connections, as they want
to fetch URLs in parallel.

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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