netdev - Re: [PATCH net-next 1/1] net: tcp: Define the TCP_MAX

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Date:   Sun, 2 Apr 2017 14:59:25 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     gfree.wind@...mail.com
Cc:     David Miller <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Patrick McHardy <kaber@...sh.net>,
        Netdev <netdev@...r.kernel.org>, Gao Feng <fgao@...ai8.com>
Subject: Re: [PATCH net-next 1/1] net: tcp: Define the TCP_MAX_WSCALE instead
 of literal number 14

On Sat, Apr 1, 2017 at 12:14 AM,  <gfree.wind@...mail.com> wrote:
> From: Gao Feng <fgao@...ai8.com>
>
> Define one new macro TCP_MAX_WSCALE instead of literal number '14',
> and use U16_MAX instead of 65535 as the max value of TCP window.
> There is another minor change, use rounddown(space, mss) instead of
> (space / mss) * mss;
>
> Signed-off-by: Gao Feng <fgao@...ai8.com>
> ---

Looks OK to me.

IMHO this is a nice direction, since there is a proposal to increase
the maximum shift factor from 14 to 15:
  https://tools.ietf.org/html/draft-nishida-tcpm-maxwin-03

Though there are a few spots where a literal 14 appears:

tcp_input.c:3763:  net_info_ratelimited("%s: Illegal window scaling
value %d >14 received\n",

tcp_output.c:238:                * See RFC1323 for an explanation of
the limit to 14


neal