DHCPv6-4.1.mumble

[bmanning at vacation.karoshi.com]

On Thu, Jun 12, 2008 at 04:58:59PM +0100, Simon Hobson wrote:
> bmanning at vacation.karoshi.com wrote:
> >i did mention merging as an issue -IF- it was not possible to
> >pass DNS server information.  to borrow from the DNS side of the
> >house, it is perfectly reasonable to return, over IPv4 transport,
> >data about IPv6.
> >the dhcp "Domain Nameserver" option should be able to return a series
> >of IP addresses that a client might use.  this capability is seriously
> >crippled by the presumption that the IPv4 version of DHCP can -ONLY-
> >return IPv4 addresses for this option and the IPv6 version of DHCP can
> >-ONLY- return IPv6 addresses for its functional equivalent of the
> >Domain Nameserver option.  The presumption seems false.
> >
> >If, as asserted elsewhere in this thread, the IP address string to be
> >returned is unspecified then it should be fairly easy to assert that
> >any valid IP address string/structure should be valid. I am working on
> >patching the ISC code to do just this.
> 
> You seem to have missed the point - completely !
> 
> The existing option was defined well before IPv6 was even being 
> considered, and so it was defined in terms of IP addresses taking 4 
> bytes<period>. There is no 'flag' in there to say what the contents 
> are, it's just a sequence of one or more 4 byte values.
> 
> Certainly, if DHCP was being started from scratch now then we almost 
> certainly wouldn't come up with what we have now - but we are where 
> we are.

	fatalistic to the end. :)

> Changing the source won't help you. You could stick an IPv6 address 
> in the option, but unmodified clients will assume that it's four IPv4 
> addresses and (wrongly) configure four IPv4 nameserver entries. The 
> only way to fix that will be to modify EVERY client on your entire 
> network - including the closed binary clients included in Windows, 
> Mac OS etc. You CANNOT put a flag in there to say "this is an IPv6 
> address" because that will break compatibility with unmodified 
> clients.

	actually, changing the source just might.
	i am willing (and nomimally able) to change the client
	code on all the machines in my network.  (well all but the 
	one Windows machine)... just don't expect results when
	you come visit unless you want to install the local client
	code.

> It took years for the 'old' DHCP to be implemented and supported, 
> your chances of getting all the vendors to modify existing clients in 
> a timely manner is (being optimistic) approximately nil !

	open source is a joy and thing of beauty forever...
	Vendors can (and will) do what they like.

--bill