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

[Pali Rohár]

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.
> > 
> > Understood.
> > 
> > > 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
> > time.
> > 
> > * DHCPv6 clients are identified by DUID string, which we can say is
> >   totally random and are not persistent across multi-OS computers or
> >   reinstalling...
> > 
> > * Internally DHCPv6 leases are identified by IAID.
> > 
> > So to make configuration clean for both IPv4 and IPv6 we need support
> > for:
> > 
> > * Assigning IPv4 lease to more MAC addresses at the same time
> >   (This will help people to use "more mac addresses" functionality
> > correctly)
> > 
> > * 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.

-- 
Pali Rohár
pali.rohar at gmail.com