netdev - Re: [PATCH net-next] tcp: better validation of received ack sequences

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Message-Id: <20170525.132236.1835338699503607288.davem@davemloft.net>
Date:   Thu, 25 May 2017 13:22:36 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     eric.dumazet@...il.com
Cc:     p.fiterau-brostean@...ence.ru.nl, netdev@...r.kernel.org,
        F.Vaandrager@...ru.nl, ncardwell@...gle.com, ycheng@...gle.com,
        soheil@...gle.com
Subject: Re: [PATCH net-next] tcp: better validation of received ack
 sequences

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 25 May 2017 09:50:51 -0700

> On Thu, 2017-05-25 at 12:48 -0400, David Miller wrote:
>> From: Eric Dumazet <eric.dumazet@...il.com>
>> Date: Tue, 23 May 2017 15:24:46 -0700
>> 
>> > Add a FLAG_NO_CHALLENGE_ACK so that tcp_rcv_state_process()
>> > can choose to send a challenge ACK and discard the packet instead
>> > of wrongly change socket state.
>> 
>> Applied, but the tests end up being double-negatives so it might
>> have been easier to understand if the flag was a positive rather
>> than a negative value.
> 
> I thought of this (and was in fact one of the patch I sent for internal
> review at Google), but this was changing all tcp_ack() calls instead of
> a single one ?
> 
> Or maybe I am missing some easier way ?

Indeed, it is a bit of churn to adjust all callers in order to make
one test easier to read.

I'm not so sure it's better or worth it...