Re: Design misfeature of dhclient for multiple interfaces

[Roy Marples <roy%marples.name@localhost>]

On Fri, 2008-09-12 at 19:19 +0100, Roy Marples wrote:
> On Tue, 2008-09-09 at 08:24 +0100, Roy Marples wrote:
> > On Mon, 2008-09-08 at 21:42 -0400, Steven M. Bellovin wrote:
> > > Certainly one approach.  dhcpcd might handle this better, too.
> > 
> > It does! But currently only for Linux.
> > Linux has route metrics, which means that you can install multiple
> > routes to the same destination. See attached route output for an
> > example.
> > re0 is wired, ral0 is wireless. As re0 has the lower metric it will be
> > the preferred route. The kernel takes care of everything :)
> > 
> > No BSD currently supports route metrics, which poses a problem. To be
> > able to solve this, dhcpcd needs to work like dhclient and have one
> > instance handling multiple interfaces (dhcpcd-4 and earlier are single
> > instance per interface by design). This has already been done and works
> > very well. The code is also a lot smaller and whilst memory usage for
> > the instance has increased (duh - more interfaces == more memory) it's
> > still more efficient than dhclient by quite some margin.
> > 
> > I'll email tech-net@ when this is done so I can get some testing done.
> > Should be done somewhere over the next few days or weeks - prod me if I
> > take a bit longer ;)
> 
> This is now done - well mostly :)
> You can download a snapshot here [1] and use the rc.d script [2] as
> well. Don't enable ifconfig_xxx=dhcp.
> 
> The only things left to do are change the subnet route for the preferred
> interface address and expire the lease when the link goes and re-request
> it comes back up. This maybe done over the weekend, if not next week.
> 
> BTW, this is a very experimental version, ware bugs or broken
> features!
> Check the man pages for changes.

And this in turn is now done - you can swap between wired and wireless
on the same subnet and dhcpcd manages the routing just fine.

It's now getting quite stable, so I've released an experimental version
[1] with rc.d script [2] so I can get some feedback.
Use the command
netstat -nr -f inet
to verify the routing changes to the right interface.

You may wish to add this line to /etc/dhcpcd.conf
denyinterfaces fwip[0-9]* tap[0-9]*
to stop dhcpcd from managing those interfaces.

Let me know how it works for you :)

Thanks

Roy

[1] http://roy.marples.name/dhcpcd/dhcpcd-4.99.1.tar.bz2
[2] http://roy.marples.name/dhcpcd/dhcpcd.rc