[Dnsmasq-discuss] dnsmasq not responding to DHCPv6 DHCPCONFIRM messages attempting to confirm an unknown lease

[Michael Marley]

Hi,

I have dnsmasq set to be a DHCPv6 and DHCPv6 server for my local 
network.  Here is the relevant part of the configuration:

interface=vlan1
interface=vlan2
interface=vlan3
interface=vlan4
interface=vlan5
dhcp-authoritative
dhcp-range=interface:vlan1,10.1.0.2,10.1.255.253,1h
dhcp-range=interface:vlan2,10.2.0.2,10.2.255.253,1h
dhcp-range=interface:vlan3,10.3.0.2,10.3.255.253,1h
dhcp-range=interface:vlan4,10.4.0.2,10.4.255.253,1h
dhcp-range=interface:vlan5,10.5.0.2,10.5.255.253,1h
dhcp-range=interface:vlan1,fdda:5f29:421b:1::2,fdda:5f29:421b:1::ffff,64,1h
dhcp-range=interface:vlan2,fdda:5f29:421b:2::2,fdda:5f29:421b:2::ffff,64,1h
dhcp-range=interface:vlan3,fdda:5f29:421b:3::2,fdda:5f29:421b:3::ffff,64,1h
dhcp-range=interface:vlan4,fdda:5f29:421b:4::2,fdda:5f29:421b:4::ffff,64,1h
dhcp-range=interface:vlan5,fdda:5f29:421b:5::2,fdda:5f29:421b:5::ffff,64,1h

My problem is that if a DHCPv6 client attempts to confirm an unknown 
lease (from another network, for example if I unplug a computer from 
vlan4 and plug it into vlan3), dnsmasq doesn't respond to the 
DHCPCONFIRM messages that the client sends.  I just get a long string of

DHCPCONFIRM(vlan4) 00:01:00:01:20:65:91:d7:3c:97:0e:7f:f5:ba

until the client finally gives up and acquires a new lease from scratch. 
  This also happens if I connect a client to my network that was 
previously connected to another network with a DHCPv6 lease.  For DHCPv4 
in the same situation, it works correctly and sends a DHCPNAK, causing 
the client to retry from scratch immediately and get a new lease quickly 
as described in the documentation for the "dhcp-authoritative" option.  
It seems to me this ought to take place for DHCPv6 as well, preventing 
the client from having to time out before obtaining a lease.  Have I 
configured something wrong or is there a bug?

Thanks,

Michael Marley