netdev - Re: [PATCH net-next v2] tcp: force cwnd at least 2 in tcp_cwnd

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d07bfdf1-2060-bdaf-8df0-7e33a8f017b7@gmail.com>
Date:   Wed, 27 Jun 2018 08:04:57 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Lawrence Brakmo <brakmo@...com>, netdev <netdev@...r.kernel.org>
Cc:     Kernel Team <kernel-team@...com>, Blake Matheny <bmatheny@...com>,
        Alexei Starovoitov <ast@...com>
Subject: Re: [PATCH net-next v2] tcp: force cwnd at least 2 in
 tcp_cwnd_reduction



On 06/26/2018 07:34 PM, Lawrence Brakmo wrote:
> When using dctcp and doing RPCs, if the last packet of a request is
> ECN marked as having seen congestion (CE), the sender can decrease its
> cwnd to 1. As a result, it will only send one packet when a new request
> is sent. In some instances this results in high tail latencies.
> 

>  	}
>  	/* Force a fast retransmit upon entering fast recovery */
>  	sndcnt = max(sndcnt, (tp->prr_out ? 0 : 1));
> -	tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt;
> +	tp->snd_cwnd = max((int)tcp_packets_in_flight(tp) + sndcnt, 2);

Canonical way is to use min_t(), please respin (no need to explain this trivia in changelog)

Thanks.