[Dnsmasq-discuss] [PATCH] DHCPv6: Add support for more than one hardware address per IPv6 address
simon at thekelleys.org.uk
Fri May 12 16:15:20 BST 2017
On 09/05/17 10:21, Pali Rohár wrote:
> On Sunday 02 October 2016 11:43:43 Pali Rohár wrote:
>> On Wednesday 27 January 2016 13:37:27 Pali Rohár wrote:
>>> On Wednesday 20 January 2016 20:15:23 Simon Kelley wrote:
>>>> Dnsmasq identifies IPv6 clients via their MAC address for the
>>>> purpose of selecting dhcp-host configuration to use, but it
>>>> doesn't use the MAC address as a unique client identifier for the
>>>> purpose of assigning DHCP leases in the same way the DHCPv4 does.
>>>> That's the crucial difference.
>>> Yes, I know.
>>>> The equivalent of the DHCPv4 share MAC address facility, should
>>>> really be something which shares IAIDs, maybe?
>>> Right, in lease file is stored pair (MAC address, IP address) for
>>> IPv4 and pair (IAID, IPv6 address) for IPv6.
>>>> The crucial thing I'm trying to achieve here is turning your patch
>>>> from something that works on your network, with your very odd
>>>> configuration, into something that other people might want and use.
>>>> Without that, it's fine as your patch, but it can't go into the
>>>> dnsmasq mainline.
>>>> Maybe the way to think about that is to think about
>>>> how to document it. If we can describe what problem it solves, and
>>>> how it should be used, then we'll be getting there.
>>> I was thinking about it for more days. It is really not easy to solve
>>> this problem... Here are my results:
>>> * There are people who misuse original concept of "more mac
>>> addresses" for one ipv4 address. Dnsmasq supports this configuration
>>> only if one mac address from that --dhcp-host line is used at same
>>> * DHCPv6 clients are identified by DUID string, which we can say is
>>> totally random and are not persistent across multi-OS computers or
>>> * Internally DHCPv6 leases are identified by IAID.
>>> So to make configuration clean for both IPv4 and IPv6 we need support
>>> * Assigning IPv4 lease to more MAC addresses at the same time
>>> (This will help people to use "more mac addresses" functionality
>>> * Assigning IPv6 address to more DUIDs at the same time
>>> (This is "correct" IPv6 equivalent for previous request)
>>> * Assigning IPv6 address to more MAC addresses at the same time
>>> (This is what would fix DUID problem)
>>> And it means that pair (IAID, IPv6 address) for IPv6 leases it not
>>> enough to do it.
>>> So, what about extending lease line for IPv6 addresses to include
>>> DUID and MAC address?
>>>> We need to bear in
>>>> mind that the behaviour we're talking about violates the RFCs
>>>> specifying DHCPv6, so it has to be especially carefull justified.
>>> Thats probably truth, but if something is useful users will try to
>>> use it. Either itself by patching dnsmasq or if possible by optional
>>> config options...
>> Hi Simon! Replaying to my old email from January. Have you found some
>> time to look at my suggestions? If yes, what do you think about it?
> PING again.
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.
Using MAC addresses with DHCPv6 AT ALL is quite difficult - it's not a
concept that the RFCs deal with. Doing the sleight-of-hand trick that
works with DHCPv4 doesn't seem feasible to me for DHCPv6.
More information about the Dnsmasq-discuss