[Dnsmasq-discuss] [PATCH] DHCPv6 - Multiple reservations for single host

[Harald Jensås]

On Sun, 2020-01-26 at 20:01 +0100, Oliver Freyermuth wrote:
> I also like this new approach. "Wasting" 4 addresses for one host
> seems to be the only way
> to solve this while conforming to RFCs. 
> 
> However, there's one issue I can't find a good solution for in this
> scheme - 
> how to solve the "DNS problem" if dnsmasq is only used for DHCP, but
> DNS is provided by other means? 
> 
> The "range reservation", as highlighted, means the final address is
> not well predictable (may depend on hardware,
> other parts of the boot process etc.). 
> When dnsmasq is also doing the DNS part, that's not a problem, since
> it will use the final / "most recently leased" address for DNS. 
> Does anybody have a good proposal for the case when DHCP is provided
> by dnsmasq but DNS is maintained separately
> (i.e. the "final address" needs to be fixed)? 
> 
> Cheers,
>         Oliver

I think adding tag support for dhcp-host entries as follow up.

The idea would be to have a config like this:

# OPTION_CLIENT_ARCH_TYPE (61)
dhcp-match=set:efi6,option6:61,0007 
dhcp-match=set:efi6,option6:61,0009
dhcp-match=set:efi6,option6:61,0011
# User class is iPXE
dhcp-userclass=set:ipxe6,iPXE

dhcp-host=tag:efi6,tag:ipxe6,52:54:00:bc:c3:fd,[fd12:3456:789a:1::bb00/126],host2
dhcp-host=tag:!efi6,tag:!ipxe6,52:54:00:bc:c3:fd,[fd12:3456:789a:1::bb05],host2

The "temporary addresses" in [fd12:3456:789a:1::bb00/126] are only used
when architecture type is one of the UEFI types or the userclass option
have "iPXE". The dhcp client in the final OS should always end up with
fd12:3456:789a:1::bb05.


Another possible solution would be to use a dhcp-script which run's
nsupdate to dynamically update the dns server.



--
Harald