linux-kernel - Re: [PATCH] tcp: incoming connections might use wrong route under synflood

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Message-Id: <20130410.232612.1922869742696275542.davem@davemloft.net>
Date:	Wed, 10 Apr 2013 23:26:12 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	dp@...hloadlab.com
Cc:	kuznet@....inr.ac.ru, jmorris@...ei.org, yoshfuji@...ux-ipv6.org,
	kaber@...sh.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcp: incoming connections might use wrong route under
 synflood

From: Dmitry Popov <dp@...hloadlab.com>
Date: Thu, 11 Apr 2013 00:09:09 +0400

> There is a bug in cookie_v4_check (net/ipv4/syncookies.c):
> 	flowi4_init_output(&fl4, 0, sk->sk_mark, RT_CONN_FLAGS(sk),
> 			   RT_SCOPE_UNIVERSE, IPPROTO_TCP,
> 			   inet_sk_flowi_flags(sk),
> 			   (opt && opt->srr) ? opt->faddr : ireq->rmt_addr,
> 			   ireq->loc_addr, th->source, th->dest);
> 
> Here we do not respect sk->sk_bound_dev_if, therefore wrong dst_entry may be taken. This dst_entry is used in new socket (get_cookie_sock -> tcp_v4_syn_recv_sock), so its packets may take wrong path. There is no such bug in ipv6 code and non-cookie code (usual case). Bugfix below.
> 
> Signed-off-by: Dmitry Popov <dp@...hloadlab.com>

Please format your commit messages properly, by not allowing lines of
text longer than 80 columns.

Thank you.
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