From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Perches <joe@perches.com>
Subject: Re: [net-next-2.6 PATCH v6 3/7 RFC] TCPCT part 1c:
 sysctl_tcp_cookie_size, socket option TCP_COOKIE_TRANSACTIONS
Date: Fri, 13 Nov 2009 10:37:22 -0800
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Cc: Linux Kernel Network Developers <netdev@vger.kernel.org>
To: William Allen Simpson <william.allen.simpson@gmail.com>
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On Thu, 2009-11-12 at 23:31 -0500, William Allen Simpson wrote:
> Define sysctl (tcp_cookie_size) to turn on and off the cookie option
> default globally, instead of a compiled configuration option.
[]

> +#define TCP_COOKIE_MIN		 8		/*  64-bits */
> +#define TCP_COOKIE_MAX		16		/* 128-bits */

perhaps something like:

static const int TCP_COOKIE_MIN = 8;
static const int TCP_COOKIE_MAX = 16;

[]

> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -714,6 +714,14 @@ static struct ctl_table ipv4_table[] = {
>  	},
>  	{
>  		.ctl_name	= CTL_UNNUMBERED,
> +		.procname	= "tcp_cookie_size",
> +		.data		= &sysctl_tcp_cookie_size,
> +		.maxlen		= sizeof(int),
> +		.mode		= 0644,
> +		.proc_handler	= proc_dointvec

with proc_dointvec_minmax

		.extra1		= &TCP_COOKIE_MIN,
		.extra2		= &TCP_COOKIE_MAX,

or even adding proc_dointvec_minmax_even
might save some cycles during cookie handling.