From owner-svn-src-all@FreeBSD.ORG  Mon Nov 24 19:40:25 2014
Return-Path: <owner-svn-src-all@FreeBSD.ORG>
Delivered-To: svn-src-all@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits))
 (No client certificate requested)
 by hub.freebsd.org (Postfix) with ESMTPS id DAAB1230;
 Mon, 24 Nov 2014 19:40:25 +0000 (UTC)
Received: from cell.glebius.int.ru (glebius.int.ru [81.19.69.10])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client CN "cell.glebius.int.ru", Issuer "cell.glebius.int.ru" (not verified))
 by mx1.freebsd.org (Postfix) with ESMTPS id 5E1B57BF;
 Mon, 24 Nov 2014 19:40:24 +0000 (UTC)
Received: from cell.glebius.int.ru (localhost [127.0.0.1])
 by cell.glebius.int.ru (8.14.9/8.14.9) with ESMTP id sAOJeMmF081929
 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO);
 Mon, 24 Nov 2014 22:40:22 +0300 (MSK)
 (envelope-from glebius@FreeBSD.org)
Received: (from glebius@localhost)
 by cell.glebius.int.ru (8.14.9/8.14.9/Submit) id sAOJeMsQ081928;
 Mon, 24 Nov 2014 22:40:22 +0300 (MSK)
 (envelope-from glebius@FreeBSD.org)
X-Authentication-Warning: cell.glebius.int.ru: glebius set sender to
 glebius@FreeBSD.org using -f
Date: Mon, 24 Nov 2014 22:40:22 +0300
From: Gleb Smirnoff <glebius@FreeBSD.org>
To: Philip Paeps <philip@FreeBSD.org>
Subject: Re: svn commit: r274966 - head/sys/net
Message-ID: <20141124194022.GR47144@FreeBSD.org>
References: <201411241400.sAOE0Srq063100@svn.freebsd.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <201411241400.sAOE0Srq063100@svn.freebsd.org>
User-Agent: Mutt/1.5.23 (2014-03-12)
Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
 src-committers@freebsd.org
X-BeenThere: svn-src-all@freebsd.org
X-Mailman-Version: 2.1.18-1
Precedence: list
List-Id: "SVN commit messages for the entire src tree \(except for &quot;
 user&quot; and &quot; projects&quot; \)" <svn-src-all.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/svn-src-all>,
 <mailto:svn-src-all-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-all/>
List-Post: <mailto:svn-src-all@freebsd.org>
List-Help: <mailto:svn-src-all-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-all>,
 <mailto:svn-src-all-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 24 Nov 2014 19:40:26 -0000

On Mon, Nov 24, 2014 at 02:00:28PM +0000, Philip Paeps wrote:
P> Author: philip
P> Date: Mon Nov 24 14:00:27 2014
P> New Revision: 274966
P> URL: https://svnweb.freebsd.org/changeset/base/274966
P> 
P> Log:
P>   Add a sysctl `net.link.tap.deladdrs_on_close' to configure whether tap
P>   should delete configured addresses and routes when the interface is
P>   closed.  Default is enabled (preserve current behaviour).
P> 
P>   MFC after:	1 week

Any time I see yet another sysctl knob added I ask myself: what if I want
this feature on tap0 but doesn't want it on tap1? What if want it on host,
but doesn't want it on vmnet-enabled jail? Where from could I learn about
this sysctl if I am not subscribed to svn-src-*@?

Of course adding a sysctl knob is faster and easier for a FreeBSD hacker.
But is it a better for a FreeBSD user? Are we making OS for just ourselves?

Look, we've got tapifioctl(). If you are too lazy to introduce new
ioctl command and code it support in ifconfig, in this case you can just
use any of IFF_LINK0, IFF_LINK1, IFF_LINK2 flag to toggle this feature
via SIOCSIFFLAGS.  And then document it in tap(4).

Finally, if later some developer comes and does it in a proper way, then
he would have a burden of supporting your sysctl for backwards compatibility,
because you very quickly MFCed it.

P.S. I am sorry if my email sounds like old man's grumbling.

-- 
Totus tuus, Glebius.