DHCPv6 PD server

[Philipp Kern]

Seth,

On Thu, Aug 02, 2012 at 02:56:35PM +0200, Seth Mos wrote:
> I sent a message on the ISC dhcpd list but got no response. My most
> educated guess is that they do not have the resource to implement a
> daemon that inserts routes into the routing table yet.

but they have it on a list of known deficiencies?

> Note that this also applies to the dhcp6 relay. Which would need to
> insert routes.

True enough. This requires more logic than just en-/decapsulate those
DHCPv6 queries/answers. And it's also hard to do that from the outside
if it's not supported by the device, as I guess there's no proper
solution to inject routes into the routing table for things that are
not local to the injector. (Like through a routing protocol or using SNMP from
the outside.)

> Because ISC dhcpcd is running under a unpriviledged user a 2nd
> daemon would be required/signaled for the route insert/remove/update
> process.

I presume you mean dhcpd, not dhcpcd? Well, given recent developments
in the Linux world I wouldn't be surprised about a dbus call trying to add
routes and somebody else picking them up. ;-)

In this case a proper signal/hook would already be "enough" for a first stab,
though.

> I briefly looked at other servers but had pretty much the same
> conclusion. This works because the leasefile is written when a new
> lease is handed out, this also causes you lease per second
> performance of your DHCP server to be limited by disk IO.

True. For a recent conference I had to run the DHCPv4 server with eatmydata
because it actually fsync()ed for every lease, which was horrible for
desktop hardware. (There seems to be a configure option for this, too.)
I guess events for the modified file would fire in the same instant even if the
content does not reach persistent storage space.

Kind regards
Philipp Kern
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