netdev - Re: [PATCH net-next 3/3] net: Add table id from route lookup to route response

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Message-ID: <20150902194326.GZ504@gospo.home.greyhouse.net>
Date:	Wed, 2 Sep 2015 15:43:27 -0400
From:	Andy Gospodarek <gospo@...ulusnetworks.com>
To:	Thomas Graf <tgraf@...g.ch>
Cc:	David Ahern <dsa@...ulusnetworks.com>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 3/3] net: Add table id from route lookup to
 route response

On Wed, Sep 02, 2015 at 09:08:36PM +0200, Thomas Graf wrote:
> On 09/02/15 at 12:51pm, David Ahern wrote:
> > On 9/2/15 12:49 PM, David Miller wrote:
> > >From: Thomas Graf <tgraf@...g.ch>
> > >Date: Wed, 2 Sep 2015 20:43:46 +0200
> > >
> > >>On 09/02/15 at 09:40am, David Ahern wrote:
> > >>>rt_fill_info which is called for 'route get' requests hardcodes the
> > >>>table id as RT_TABLE_MAIN which is not correct when multiple tables
> > >>>are used. Use the newly added table id in the rtable to send back
> > >>>the correct table.
> > >>>
> > >>>Signed-off-by: David Ahern <dsa@...ulusnetworks.com>
> > >>
> > >>What RTM_GETROUTE returns is not the actual route but a description
> > >>of the routing decision which is why table id, scope, protocol, and
> > >>prefix length are hardcoded. This is indicated by the RTM_F_CLONED
> > >>flag. What you propose would break userspace ABI.
> > >
> > >Agreed, I don't think we can do this.
> > >
> > 
> > Doesn't the table used to come up with the decision matter for IPv4? ie.,
> > hardcoding to MAIN is misleading when there is absolutely no way the
> > decision comes from that table. IPv6 already returns the table id.
> > 
> > Or is your response that it breaks ABI and hence not going to fix.
> 
> This behaviour comes back from when we still had the IPv4 routing cache
> which was flat.

So before the routing cache was removed, was the response always
RTA_TABLE_MAIN since there was no way to indicate which table may have
route if it came from the cache?
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