[Dnsmasq-discuss] [PATCH] DHCPv6: Honor assigning IPv6 address based on MAC address

[Oliver Freyermuth]

Am 14.05.19 um 17:52 schrieb Roy Marples:
> On 14/05/2019 14:29, Oliver Freyermuth wrote:
>> Same here. In an automated deployment situation, client changes DUID in each phase:
>> - PXE (if done via IPv6)
>> - Installation time (from ramdisk)
>> - Final OS after installation
>> This may improve if newer versions of dhcpcd get packaged in installer ramdisks and OS, and also for systemd-dhcp,
>> but I am still unaware of any implementation of machine-id as base for the client DUID in dhclient and of course the implementations are all not exactly the same.
>> And then there is still the UEFI doing the PXE part, systems with broken machine-id etc.... And of course, dual booting if not set up with identical cliend-DUID.
>>
>> In general, my belief is that the RFC was made without real life use cases in mind and hence did not think of these.
>> The patch is very helpful to overcome these issues and matches user expectation (when specifying a MAC address in the config file, I want it to be used).
> 
> Speaking for dhcpcd (as yay, I am the author) - if the OS presents a stable UUID dhcpcd will use that for the DUID:
> 
> https://tools.ietf.org/html/rfc6355
> https://roy.marples.name/cgit/dhcpcd.git/tree/src/duid.c#n63
> 
> So a fully automated deployment using dhcpcd AND a kernel which reports a stable UUID then all is good.

There's also still another step that may cause an issue: If the UEFI also PXE boots via IPv6, it may present even another client DUID. 
It should certainly use the same UUID dhcpcd is using, but if it does not, you might be screwed (at least if your environment is IPv6 only). 

> 
> But not everyone uses dhcpcd>=7.0.6 with the UUID code in, nor a kernel which reports a stable UUID.
> 
> There is literally no reason to use dhclient anymore - and hasn't been for a number of years.

I fully agree (as a Gentoo user who has the freedom of choice). 
Somebody should teach those guys still shipping dhclient by default in their distro (e.g. Ubuntus network-manager package pulls in dhclient :-( ) or in their installer. 
And in our case, we are sadly not fully free in terms of choice of distro to use :-(. 

Cheers (and thanks again for the implementation in dhcpcd, and of course for dhcpcd itself!),
	Oliver

> 
> Roy