PD hint support in dhclient6?

Paul Dugas paul at dugas.cc
Thu Jan 7 13:51:06 UTC 2016

Trying to get a Sophos UTM9 router to request a /60 IPv6 prefix delegation
without much luck.  Comcast keeps giving me a /64 which i their default
unless they get a PD hint otherwise.  The box is using dhclient6-4.3.0
under the hood and I'm wondering if this version has any support for
including the hint in the initial solicit packet.

It's running the command like so:

    /usr/sbin/dhclient6 -P -d -N -cf /etc/eth1.conf6 -lf
/var/db/eth1_pd_na.leases6 -pf /var/run/dhclient6_eth1.pid eth1

/etc/eth1.conf6 contains:

    interface "eth1" {
script "/usr/sbin/dhcp_updown.plx";
send host-name "eg.example.com";

Packet captures show and IA_PD option (25) in the solicit but no IAPREFIX
option (26) which I think is what's necessary.  I've tried adding "send
ipv6.ia_pd 1;" to the config file but I end up with two IA_PD options in
the packet - one bogus (length 1 and value 0x01) and the original one with
sane values for IAID, T1, and T2.  I've tried poking through the code as
well and I only see it adding IAPREFIX (26) options to renew packets.  Not
sure about that though.

Can someone here definitively tell me this isn't possible or, if it is, how?

Thanks much in advance for the time and effort on the project.

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