From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: iproute2: adding /128 address to sit interface borks Date: Sat, 27 Feb 2010 08:23:56 -0800 Message-ID: <20100227082356.67b7c0a3@nehalam> References: <20090710082731.0b06c0eb@nehalam> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Stephen Hemminger , netdev@vger.kernel.org To: Jan Engelhardt Return-path: Received: from mail.vyatta.com ([76.74.103.46]:57952 "EHLO mail.vyatta.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S968514Ab0B0QYJ (ORCPT ); Sat, 27 Feb 2010 11:24:09 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: On Sat, 27 Feb 2010 16:03:36 +0100 (CET) Jan Engelhardt wrote: > > On Friday 2009-07-10 17:27, Stephen Hemminger wrote: > >On Fri, 10 Jul 2009 14:05:01 +0200 (CEST) > >Jan Engelhardt wrote: > > > >> it's impossible to do this, and the error message does not say why > >> that is so. No word in dmesg either. > >> > >> # ip a a fc00::49/128 peer fc00::7 dev sit7 > >> RTNETLINK answers: Invalid argument > > > >You will need to walk through the path in the kernel. > >In worst case, it means adding kernel printk's. > > > >Then if you want to be nice, make a patch to ipaddr.c in iproute > >utilities so command line can find the error before passing to > >kernel and give a nice error :-) > > The issue here was that the peer is encoded using the broadcast > field, and since IPv6 has no broadcast, it was rejected by > the kernel. The error messages really need to be improved. > > This year also came an article about that, > http://lwn.net/Articles/374794/ The article overlooks the fact that netlink is a message based interface. There is no reason that the response message can't be extended to add additional sections to give more detailed answer. The issues are: * no infrastructure for this (message format, helpers, etc) * tedious effort to annotate all the existing error returns * update to command and library The extended error reports could even be a kernel config option so the embedded and those worried about space would not have to have it. --