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Re: Disabling IPv6 accept_ra on just some interface (fwd)

To: netdev@xxxxxxxxxxx
Subject: Re: Disabling IPv6 accept_ra on just some interface (fwd)
From: Pekka Savola <pekkas@xxxxxxxxxx>
Date: Mon, 30 Aug 2004 09:10:26 +0300 (EEST)
Sender: netdev-bounce@xxxxxxxxxxx
I already re-sent this in Feb 2004, but apparently it got lost.

In summary, I'd like to get accept_ra overloaded so that when it
changes from 0->1, it sends out a router solicititation.  Seems like a 
good idea to me.  This helps in the situation where you want to 
disable autoconf on some interfaces, but because you need to disable 
it by default on all interfaces before any interface is created, 
you'll want a mechanism to trigger router solicitications from the 
user space.

Another thing to consider is what happens when accept_ra changes from
1->0.  The most conservative thing would be nothing..

---------- Forwarded message ----------
Date: Mon, 27 Oct 2003 15:05:42 +0200 (EET)
From: Pekka Savola <pekkas@xxxxxxxxxx>
To: "YOSHIFUJI Hideaki / [iso-2022-jp] 吉藤英明"
Cc: netdev@xxxxxxxxxxx, sekiya@xxxxxxxxxx
Subject: Re: Disabling IPv6 accept_ra on just some interface

On Mon, 27 Oct 2003, YOSHIFUJI Hideaki / [iso-2022-jp] 吉藤英明 wrote:
> In article <Pine.LNX.4.44.0310231457110.3347-100000@xxxxxxxxxx> (at Thu, 23 
> Oct 2003 15:22:47 +0300 (EEST)), Pekka Savola <pekkas@xxxxxxxxxx> says:
> > So, my thought (comments welcome) is:
> > 
> >  1) when accept_ra changes from 0 -> 1, initiate the route 
> >     solicitation process, likewise as one would when the interface is 
> >     brought up.
> > 
> >     Makes sense?
> > 
> >  2) (probably not a good idea, but some food for thought..) when accept_ra 
> >     changes from 1 -> 0, delete any autoconfigured routes or
> >     prefixes.  (could be ugly / dangerous..)
> Well, we'd propose to have another config "send_rs" or something like that
> because accept_ra is also effective against unsolicited RAs.
> It, "send_rs," tells kernel to start sending RS 
> when the variable is changed 0 to 1 and/or 
> when interface is going up.

I don't have any major objections to this model, I'm just worried that it
might make the configuration more complex (we already have accept_ra and
"autoconf" toggles which are confusing enough without documentation :-)
with little gain.

That is, is there any case when you'd want to accept an RA but *not* send 
RS?  I fail to see clear applicability for this, hence my proposal to 
overload accept_ra :-)

> Assume the node has eth0 and eth1.
> Operation will be something like the following.
> If you want to listen RA and to send RS on some interfaces,
>  sysctl -w net.ipv6.conf.default.accept_ra=0
>  sysctl -w net.ipv6.conf.default.send_rs=0
>  ifup -a
>  sysctl -w net.ipv6.conf.eth0.accept_ra=1
>  sysctl -w net.ipv6.conf.eth0.send_rs=1
> If you want to listen RA on all interfaces, but do not want to send RS on 
> some of them, 
>  sysctl -w net.ipv6.conf.default.accept_ra=1
>  sysctl -w net.ipv6.conf.default.send_rs=0
>  ifup -a
>  sysctl -w net.ipv6.cont.eth0.send_rs=1

Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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