netdev - Re: [PATCH] Add sysctl to set the advertised TCP initial receive window.

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Message-ID: <1260320369.27677.183.camel@Joe-Laptop.home>
Date:	Tue, 08 Dec 2009 16:59:29 -0800
From:	Joe Perches <joe@...ches.com>
To:	chavey@...gle.com
Cc:	davem@...emloft.net, netdev@...r.kernel.org, therbert@...gle.com
Subject: Re: [PATCH] Add sysctl to set the advertised TCP initial receive
 window.

On Tue, 2009-12-08 at 16:30 -0800, chavey@...gle.com wrote:
> Add a sysctl, tcp_init_rcv_wnd, to set the TCP initial receive window
> size advertised by passive and active TCP connections.

Hi Laurent.

> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
> index 2dcf04d..1257f89 100644
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -656,6 +656,16 @@ static struct ctl_table ipv4_table[] = {
>  		.mode		= 0644,
>  		.proc_handler	= proc_dointvec
>  	},
> +	{
> +		.ctl_name	= CTL_UNNUMBERED,
> +		.procname	= "tcp_init_rcv_wnd",
> +		.data 		= &sysctl_tcp_init_rcv_wnd,
> +		.maxlen 	= sizeof(int),
> +		.mode 		= 0644,
> +		.proc_handler 	= proc_dointvec_minmax,
> +		.extra1		= &zero,
> +		.extra2		= TCP_INIT_RCV_WND_MAX

This won't work if you use proc_dointvec_minmax.

.extra1 and .extra2 are used as pointers to int,
not the int values themselves.

You'd have to use something like:

static const int zero = 0;
static const int tcp_init_rcv_wnd_max = TCP_INIT_RCV_WND_MAX;

[...]
		.proc_handler 	= proc_dointvec_minmax,
		.extra1		= &zero,
		.extra2		= &tcp_init_rcv_wnd_max;

For instance, the tcp_retries1 entry:

{
	.procname = "tcp_retries1",
	.data = &sysctl_tcp_retries1,
	.maxlen = sizeof(int),
	.mode = 0644,
	.proc_handler = proc_dointvec_minmax,
	.extra2 = &tcp_retr1_max
}


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