Re: [PATCH] tcp: incoming connections might use wrong route undersynflood

From: David Miller
Date: Wed Apr 10 2013 - 23:26:20 EST

From: Dmitry Popov <dp@xxxxxxxxxxxxxxx>
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),
> 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@xxxxxxxxxxxxxxx>

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