To: linux-net@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, Al Boldi <a1426z@gawab.com>
Subject: Re: [RFC] ip / ifconfig redesign
References: <200512022253.19029.a1426z@gawab.com>
	<20051202211920.GJ13985@lug-owl.de>
From: ebiederm@xmission.com (Eric W. Biederman)
Date: Thu, 08 Dec 2005 03:15:51 -0700
In-Reply-To: <20051202211920.GJ13985@lug-owl.de> (Jan-Benedict Glaw's
 message of "Fri, 2 Dec 2005 22:19:20 +0100")
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Jan-Benedict Glaw <jbglaw@lug-owl.de> writes:

> On Fri, 2005-12-02 22:53:19 +0300, Al Boldi <a1426z@gawab.com> wrote:
>
>> The obvious benefit here, would be the transparent ability for apps to bind 
>> to addresses, regardless of the link existence.
>
> # echo 1 > /proc/sys/net/ipv4/ip_nonlocal_bind
>
> and/or bind to address 0 (aka 0.0.0.0) instead of a given IP address.

Or equally:
	int opt = 1;
	setsockopt(fd, IPFREEBIND, &opt, sizeof(opt));
in your application.

It's cool the backwards compatibility is so good no one even
noticed it was implemented :)
And from the kernel source as to why this behaviour is not
the default.

	/* Not specified by any standard per-se, however it breaks too
	 * many applications when removed.  It is unfortunate since
	 * allowing applications to make a non-local bind solves
	 * several problems with systems using dynamic addressing.
	 * (ie. your servers still start up even if your ISDN link
	 *  is temporarily down)
	 */

Eric
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