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 <[email protected]>
---
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 <[email protected]> wrote:
> From: Dmitry Popov <[email protected]>
> 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 <[email protected]>
>
> Please format your commit messages properly, by not allowing lines of
> text longer than 80 columns.
>
> Thank you.
--
Dmitry Popov <[email protected]>
--
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