Re: ip6mode in rc

[Mihai Chelaru <mihai.chelaru%ngnetworks.ro@localhost>]

On Mon, 2010-04-26 at 09:45 -0400, Greg Troxel wrote:
> As I understand it the v6 specifications define the notion of router vs
> host as a serious distinction, and ip6mode sets a number of defaults.
> ip6mode=router forces v6 forwarding on.  autohost sets up the machine to
> take router advertisements, and there is a complaint if one has rtsold
> w/o autohost.

The serious distinction refers mostly to the router advertisments case
if I remember correctly.

> 
> Is there something that you want to do that is difficult to do now?  I
> have been running a number of v6 routers and hosts and not been having
> problems.
> 

No, when I needed both rtsol and rtadvd, I modified the rc scripts and
got rid of ip6mode.

> The only thing I can think of is trying to set up a router where one
> interface uses stateless autoconfiguration.  This is a bizarre setup
> that the specs as I remember say one shouldn't do.

That's exactly the example I'm referring to. Yes, I know that dhcpdv6 is
prefered over rtsol in this case (and probably in all cases) but that's
another discussion.
Moreover, one can be surprised to find out that he can't forward packets
and also have an interface autoconfigured (the router + rtsol case),
especially if that interface is not taking active part in routing
process.

> I think it's good that someone can just set ip6mode=autohost in rc.conf
> and then have functioning v6, without having to muck with sysctls.

You also have to add rtsol=YES and probably change rtsol_flags if you
don't want to autoconfigure all interfaces. So, all sysctls can be done
separately in a rtsol script - and there's just one sysctl to muck with
in this case. So, it looks to me like one more line to write in this
case.

For router case, I don't understand why one has to do different for ipv4
and ipv6. If you muck with sysctls for v4, do the same for v6. Why
should one set a variable in rc.conf in order for network script to set
a sysctl flag ? I strongly believe that we should minimize difference
between v4 and v6 procedures - including startup configs and different
utilities like ping-ping6, traceroute-traceroute6.

Don't think that I have a teeth against it. If you or someone else find
these options useful, it's fine for me, I just want to understand the
logic behind their long and happy existence.

-- 
Mihai