netdev - Re: [PATCH net] tcp md5sig: Use skb's saddr when replying to an incoming segment

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Date:   Mon, 11 Dec 2017 20:51:09 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Christoph Paasch <cpaasch@...le.com>,
        David Miller <davem@...emloft.net>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net] tcp md5sig: Use skb's saddr when replying to an
 incoming segment

On Mon, 2017-12-11 at 00:05 -0800, Christoph Paasch wrote:
> The MD5-key that belongs to a connection is identified by the peer's
> IP-address. When we are in tcp_v4(6)_reqsk_send_ack(), we are
> replying
> to an incoming segment from tcp_check_req() that failed the seq-
> number
> checks.
> 
> Thus, to find the correct key, we need to use the skb's saddr and not
> the daddr.
> 
> This bug seems to have been there since quite a while, but probably
> got
> unnoticed because the consequences are not catastrophic. We will call
> tcp_v4_reqsk_send_ack only to send a challenge-ACK back to the peer,
> thus the connection doesn't really fail.
> 
> Fixes: 9501f9722922 ("tcp md5sig: Let the caller pass appropriate key
> for tcp_v{4,6}_do_calc_md5_hash().")
> Signed-off-by: Christoph Paasch <cpaasch@...le.com>
> ---
>  net/ipv4/tcp_ipv4.c | 2 +-
>  net/ipv6/tcp_ipv6.c | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)

Reviewed-by: Eric Dumazet <edumazet@...gle.com>

Thanks !