lw4o6 [rfc 7596] provisioning with ISC dhcpd(v6) [rfc 7598]

[Kostas Zorbadelos]

Greetings to the list,

First I have to say that I have a very limited experience to dhcp
protocols and should be considered a rookie in the area.

I am investigating the provisioning mechanism in a lw4o6 setup. The
"must" according to RFC is DHCPv6 to issue information to the
client. The relevant options are described in rfc 7598
(OPTION_S46_CONT_LW). The problem is actually identifying each dhcp
client and providing to it a set of parameters (global AFTR IPv6,
global CPE IPv4, restricted port_set, IPv6 binding prefix).

In our setup, each broadband subscriber makes a PPP connection to the
network. The steps are

- PPP is established, customer gets global IPv4 address/DNS servers etc
  through IPCP
- Through IPCPv6 the user also gets IPv6 link local and IPv6
  connectivity
- User gets a public WAN /64 through SLAAC over the PPP link
- User makes a DHCPv6 request to get a delegated IPv6 prefix (/56) and
  v6 resolver info

The DHCPv6 functionality is now part of the BNG terminating router.
In the new lw4o6 setup we believe we should maintain a central DHCPv6
setup that will provide the lw4o6 params to clients (and most probably
also assume to role to provide the delegated IPv6 prefixes). In this
setup the BNG routers will become DHCPv6 relays. 

The problem is our tests so far is that the central ISC DHCPv6 server
sees the address of the relay in the "link address" field of the relayed 
message and so we cannot match subnet6 configured blocks for the
end-users. In relevant captures and communication with the BNG vendor we
saw that the end-user info (the address the DHCPv6 request is coming
from) is contained in a "peer address" field in the relay-forward
message. I guess if we could use that field as a matching criterion in
the dhcpd config we could find a solution. Another approach would be to
use the client port info (option 82) but the vendor said that it cannot
provide this information in the DHCPv6 relayed messages at this time.

The actual questions:

- is it possible (using the class or some other feature) to perform a
  match in dhcpd based on the "peer address" field? Can the match be of
  the form "peer address contained in a v6 network prefix"?
- do you see any other way to perform the configuration? Pointers or
  hints to actual config would be highly appreciated.

Thanks in advance and sorry for the long mail :)

Regards,

Kostas 

-- 
Kostas Zorbadelos	http://gr.linkedin.com/in/kzorba