Messages in this thread Patch in this message | | | Date | Thu, 11 Apr 2013 11:46:00 +0400 | From | Dmitry Popov <> | Subject | Re: [PATCH] tcp: incoming connections might use wrong route under synflood |
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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 by new socket (get_cookie_sock -> tcp_v4_syn_recv_sock), so its packets may take the wrong path.
Signed-off-by: Dmitry Popov <dp@highloadlab.com> --- net/ipv4/syncookies.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/ipv4/syncookies.c b/net/ipv4/syncookies.c index ef54377..397e0f6 100644 --- a/net/ipv4/syncookies.c +++ b/net/ipv4/syncookies.c @@ -349,8 +349,8 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb, * hasn't changed since we received the original syn, but I see * no easy way to do this. */ - flowi4_init_output(&fl4, 0, sk->sk_mark, RT_CONN_FLAGS(sk), - RT_SCOPE_UNIVERSE, IPPROTO_TCP, + flowi4_init_output(&fl4, sk->sk_bound_dev_if, 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); On Wed, 10 Apr 2013 23:26:12 -0400 (EDT) David Miller <davem@davemloft.net> wrote:
> From: Dmitry Popov <dp@highloadlab.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@highloadlab.com> > > Please format your commit messages properly, by not allowing lines of > text longer than 80 columns. > > Thank you.
-- Dmitry Popov <dp@highloadlab.com>
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