[Dibbler] Question: Does DHCP Server supoports "Prefix Delegation reconfiguration"

Tomek Mrugalski thomson at klub.com.pl
Sun Mar 31 18:18:34 CEST 2013

On 13-03-31 09:03, Rapoport, MichaelX wrote:
> Hello.
> Thank you for clarification. My concern comes from the following
> requirement of the attached document:
> "If the eRouter has used all of its sub-prefixes and new
> Customer-Facing Logical Interfaces are enabled, the eRouter MUST
> revoke the most recently delegated sub-prefix and use it to assign
> /64 interface-prefixes to the new Customer-Facing Logical
> Interface(s). If more /64 interface-prefixes are needed, the eRouter
> MUST continue to revoke delegated sub-prefixes from most recent to
> least recent until all Customer-Facing Logical Interfaces have been
> assigned /64 interface-prefixes."
There are couple problems. dibbler-client is not designed
to take any actions based on new interfaces being enabled. It can be
configured to ask for configuration on that newly enabled interface, but
this is not what you want. It can't change configuration on a different
(uplink or network facing) interface. To make this work the following
things would have to happen:
1. dibbler-client would need to gain the ability to detect new
interfaces. There's some code for that already.
2. there would have to be a way to tell dibbler-client that it needs to
release current and/or acquire new (or extra) prefixes.
3. dibbler-client would have to know how to split received PD when
new interface appears.

All of those actions are specific to your use case and are not planned
in dibbler. Please do not submit bugs for those. You may develop such
features on your own and submit a patch. I may be able to accept it, if
the code is of good quality.

> According to this requirement there is a need to revoke the
> previously delegated Prefix, possibly by using the Release command
> and configure the interfaces. Is it possible to cause Dibbler sending
> the Release command ?
Which one do you want to initiate release: requesting router
(dibbler-client) or delegating router (dibbler-server)? If you ask about
dibbler-client, then yes - it's possible and quite easy to do, just
initiate shutdown procedure. Send term signal (kill `cat
/var/lib/client.pd` or dibbler-client stop). For server - no, there's
not such mechanism in DHCPv6 protocol that could allow the server to
force the client to do something specific. Stopping client and starting
it again is a kludge, but it potentially may work for you.


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