[Dnsmasq-discuss] [PATCH] DHCPv6: Add support for more than one hardware address per IPv6 address

Pali Rohár pali.rohar at gmail.com
Fri May 12 16:32:47 BST 2017

On Friday 12 May 2017 17:15:20 Simon Kelley wrote:
> There are so many layers of quotes here that I've completely lost
> track of what we were trying to achieve, and how to achieve it. My
> memory is that we'd failed to come up with any consensus on either
> of those.

Goal 1:

Ability to assign one IPv4 address to two different MAC addresses. 
Currently it is possible by misusing concept of "more mac addresses" 
(where IPv4 address can be "steal" by later DHCP client).

Goal 2:

Achieve Goal 1 also for DHCPv6.

> Using MAC addresses with DHCPv6 AT ALL is quite difficult - it's not
> a concept that the RFCs deal with.

I read DHCPv6 RFC and it does not refuse assigning IPv6 address based on 
link layer MAC address. Anyway, this is already supported by dnsmasq.

But what I want to achieve has ability to assign one IPv6 address to 
more MAC addresses at same time. This DHCPv6 RFC does not allow, but in 
some situations it is useful and I think such options could be provided 
by DHCPv6 server with explicit warning in documentation.

> Doing the sleight-of-hand trick
> that works with DHCPv4 doesn't seem feasible to me for DHCPv6.

Do you completely disagree with fact that dnsmasq could support this 
scenario for assigning one IP address to more network cards (identified 
by MAC address)? Or you just do not like my current implementation?

In previous email I wrote that Goal 2 can be achieved by storing tuple 
DUID, IAID, MAC address and IPv6 address into DHCPv6 leases file.

Pali Rohár
pali.rohar at gmail.com
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