How to access delegated prefix

[Mike]

On 10/1/2016 9:26 AM, André Keller wrote:
> Hi,
> 
> I'm struggling in accessing the delegated prefix to use in a log statement.
> 
> Log:
> Oct  1 15:17:23 dhcp dhcpd[18161]: Relay-forward message from
> 2001:db8:ffff:c::195 port 547, link address ::, peer address
> fe80::a9ab:abff:fe42:8cd2
> Oct  1 15:17:23 dhcp dhcpd[18161]: [L2 Relay] No link address in relay
> packet assuming L2 relay and using receiving interface
> Oct  1 15:17:23 dhcp dhcpd[18161]: Reply PD: address
> 2001:db8:123f:f600::/56 to client with duid
> 00:03:00:01:ab:ab:ab:42:8c:d2 iaid = 2034404562 valid for 300 seconds
> 
> 
> I'd like to access the 2001:db8:123f:f600::/56 for another log message
> (I'd like to print the v6relay(0, option dhcp6.interface-id) along with it.
> 
> What I came up with so far:
> 
> on commit {
>         log(info, concat("IPv6 requested: ", binary-to-ascii (16, 16,
> ":", suffix(option dhcp6.ia-pd, 16)), "/", binary-to-ascii(10, 8, ":",
> substring(suffix(option dhcp6.ia-pd, 17), 0, 1)), " / Port: ",
> v6relay(0, option dhcp6.interface-id)));
>     }
> 
> This will log the IP address requested by the client. This address does
> not necessarily match the Reply sent by the server (especially for the
> initial allocation, the client will send ::/0).
> 
> Any idea how I can access the PD reply sent by the server?


I obtain the PD delegated by using the environment variables passed in
to the dhclient-exit-hooks script.