netdev - Re: [TCP]: min_t/max_t confusion in tcp_select_initial

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Message-Id: <20091222.194747.193724694.davem@davemloft.net>
Date:	Tue, 22 Dec 2009 19:47:47 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	roel.kluin@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [TCP]: min_t/max_t confusion in tcp_select_initial_window()?

From: Roel Kluin <roel.kluin@...il.com>
Date: Wed, 23 Dec 2009 03:00:24 +0100

> I could be confused, but in net/ipv4/tcp_output.c:217:
> 
>                 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
>                 space = min_t(u32, space, *window_clamp);
> ------------------------^^^^^
> 
> shouldn't the min_t and max_t be exchanged? i.e.
> 
>                 space = min_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
>                 space = max_t(u32, space, *window_clamp);

It looks correct to me.

Globally, the largest window we could ever end up advertising
is the maximum of the sysctl_tcp_rmem[2] threshold and
sysctl_rmem_max.

But for this connection, the window clamp is our upper bound.
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