dhclient on Debian Jessie not sending the same identifier for DHCPv4 and DHCPv6 (RFC 4361)

[Nicolas C.]

Hello,

I'm currently testing RFC 4361 (CHCPv4 + DHCPv6 + DDNS), with :

  - a dual-stack DNS server,
  - an IPv4-only DHCPv4 server,
  - an IPv6-only DHCPv6 server,
  - a dual-stack client.

All of those are Debian Jessie 64-bits machines. DHCP servers are 
configured with "ddns-update-style standard".

The client is configured with :

/etc/network/interfaces

auto eth0
iface eth0 inet dhcp
iface eth0 inet6 dhcp

And "send fqdn.fqdn = gethostname();" in /etc/dhcp/dhclient.conf 
(instead of "send host-name").

The client receives its IPv4/v6 addresses correctly but its not 
submitting the same identifier to the DHCP resulting a conflict during DDNS.

I tried using the "-I -D LLT" parameters with dhclient which is supposed 
to make the DHCPv4 client use the same DUID as the DHCPv6 client :

https://deepthought.isc.org/article/AA-01091/0/ISC-DHCP-support-for-Standard-DDNS.html

But it doesn't work, the DHCID in the DNS is not the same.

This is the result in the forward zone (rfc4361.test) when I use 
"dhclient -4 -I -D LLT eth0" :

dual-test.rfc4361.test. 300     IN      DHCID 
AAIBNrUJyL3Zib55vs1WVGxqeX3JQ2VR69qlOISd77gOLXk=
dual-test.rfc4361.test. 300     IN      A       172.20.56.100

This is the result in the forward zone when I use "dhclient -6 -I -D LLT 
eth0" :

dual-test.rfc4361.test. 187     IN      DHCID 
AAIBEiFR4yAyM0FCusKxbBQvAPuAoRu2xiUDSnqLeu/9IY4=
dual-test.rfc4361.test. 187     IN      AAAA    2001:660:3305:122::f5c

Thanks for your help,

Nicolas C.