Re: fixed ipv6 address with DHCPv6

[Pavel Simerda <psimerda redhat com>]

Yeah, just read it. And I don't think it changes anything from the NetworkManager perspective.

Cheers,

Pavel

----- Original Message -----
> From: "Gene Czarcinski" <gene czarc net>
> To: networkmanager-list gnome org
> Sent: Saturday, February 9, 2013 5:03:52 PM
> Subject: Re: fixed ipv6 address with DHCPv6
> 
> See my reply to dcbw on the dnsmasq-discuss mailing list.
> 
> Gene
> 
> 
> On 02/08/2013 12:20 PM, Pavel Simerda wrote:
> > ----- Original Message -----
> >> From: "Gene Czarcinski" <gene czarc net>
> >> For some time I have been having a problem attempting to have a
> >> dnsmasq
> >> server provide a system with a fixed IPv6 address.  Setting an
> >> IPv4
> >> address and identifying the system with its NIC's MAC address.
> >>  But,
> >> with DHCPv6 there is no relationship defined in the standard for
> >> DHCPv6 to use the MAC.
> > Correct. It's replaced with UUID.
> >
> >> I tried using the system's name but that has not proven reliable.
> >> When
> >> the system and the dnsmasq server get "out of sync", it takes
> >> manual
> >> intervention to correct things.  When things do work, it works
> >> fine.
> > System's name is generally considered unreliable due to possible
> > collisions.
> >
> >> I looked into using the Client-ID but that "number" is based on
> >> the
> >> MAC plus time and will vary unpredictably.
> > This has been already fixed by dcbw after long talks with me and
> > cyphermox.
> >
> >> Suddenly (like yesterday) I found what appears to be the solution
> >> and
> >> it is likely to have been there for some time.  By default,
> >> dhclient
> >> will use LLT (Link-Layer plus Time) to define its DUID
> >> (Client-ID).
> > We are switching to DUID-UUID from /etc/machine-id reportedly
> > required by D-Bus (even though I can't image any reason as D-Bus
> > is not commonly used over the network).
> >
> >> But, there is an command-line override which can change this to LL
> >> (Link-Layer) which uses the MAC prepended with 0:3:0:1.
> > This was the solution I originally proposed but...
> >
> > 1) It has some drawbacks.
> >
> > 2) You don't need it for normal operation. DUID-LLT saved in a disk
> > file is stable enough for day-to-day operation. This has been
> > solved by cyphermox even before we switched to machine-id.
> >
> >> The important info is here:
> >> http://tools.ietf.org/html/rfc3315#section-9.4
> > See:
> >
> > * http://tools.ietf.org/html/rfc6355 for the DUID-UUID (in the form
> > of /etc/machine-id).
> > * https://bugzilla.gnome.org/show_bug.cgi?id=691885
> >
> >> Also examine the dhclient man age and scroll down to "*-D*/ LL or
> >> LLT/"
> > I admit that DUID-LL is still better than non-stored DUID-LLT but
> > DUID-UUID proves to be a better match that the two of those. If
> > you have specific needs, you can still override the DUID manually.
> >
> >> I then did a quick (two line) patch to NetworkManage
> >> [src/dhcp-manager/nm-dhcp-dhclient.c] to hardcode the addition of
> >> "-D",
> >> "LL" to the command-line if it is "-6".  It works as advertised.
> > Thanks for your effort but unless there's a very good reason to use
> > DUID-LL, we're not going to do that (but you can still override
> > the actual DUID e.g. by a script).
> >
> >> While this works for me, I do not propose that this be the
> >> solution
> >> in NetworkManager.  Instead, I propose that the default remain the
> >> same
> >> and a new configuration file parameter be added: DUID= which will
> >> have
> >> only two valid values: LL or LLT.
> > As UUID is now the default, this proposal is obsolete.
> >
> >> If DUID= is not specified then the default is LLT.
> >>
> >> Once this is accepted and part of NetworkManager, I will update
> >> network-manager-applet so the the DUID value can be specified when
> >> defining an IPv6 interface.  Initially, editing the configuration
> >> file should be adequate.
> > Do you have any questions or arguments for still supporting DUID-LL
> > when we have DUID-UUID?
> >
> > Cheers,
> >
> > Pavel
> >
> >
> 
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