Michael Richardson <mcr@sandelman.ca> writes:

https://www.rfc-editor.org/rfc/rfc9096.html was just published.
While is has specific relevance to those running Debian as their CPE, it also has relevance to people running Debian on a desktop or laptop, and also using virtual machines.

It is not yet popular to get prefixes via DHCPv6-PD for use with VMs (LXCs, Dockers...), I think that part of this is due to lack of clear infrastructure for doing that.

In particular, RFC9096 makes it clear that DHCPv6-PD clients ought to store the prefixes they got in stable fashion that survives reboots.
The question is, where would we do that on Debian?
It would be nice if we could do this in a fashion that was independant of the various tool options that exist to manage things.

Yes, standardised persistent lease and DUID storage would be nice.

But I think we can start much simpler by making sure we follow https://datatracker.ietf.org/doc/html/rfc9096#section-3.1
everywhere.

ifupdown has this extremely annoying misfeature that it forces a release
on shutdown, both for DHCP and DHCPv6. The automatic release on every
restart forces an unwanted and unnecessary renumbering event.

Personally, I just gave up on the whole thing and started configuring my interfaces as manual instead. Using stanzas similar to this:

iface foo0 inet manual
up /sbin/dhclient -4 -v -i -pf /run/dhclient.$IFACE.pid -lf /var/lib/dhcp/dhclient.$IFACE.leases $IFACE
up /sbin/dhclient -P -v -pf /run/dhclient6.$IFACE.pid -lf /var/lib/dhcp/dhclient6.$IFACE.leases $IFACE
down /sbin/dhclient -4 -v -i -x -pf /run/dhclient.$IFACE.pid -lf /var/lib/dhcp/dhclient.$IFACE.leases $IFACE
doen /sbin/dhclient -P -v -x -pf /run/dhclient6.$IFACE.pid -lf /var/lib/dhcp/dhclient6.$IFACE.leases $IFACE


If it's not obvious: That is exactly what ifupdown would do with
"dhcp" except that we run the client with -x (stop) instead of -r
(release) on interface down.



Bjørn

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Hi, I don't know if I'm still on this list, or if I got kicked off due to outsourced spam filtering.
I did find my subscribe message from 2001 :-)

https://www.rfc-editor.org/rfc/rfc9096.html was just published.
While is has specific relevance to those running Debian as their CPE, it also has relevance to people running Debian on a desktop or laptop, and also using virtual machines.

It is not yet popular to get prefixes via DHCPv6-PD for use with VMs (LXCs, Dockers...), I think that part of this is due to lack of clear infrastructure for doing that.

In particular, RFC9096 makes it clear that DHCPv6-PD clients ought to store
the prefixes they got in stable fashion that survives reboots.
The question is, where would we do that on Debian?
It would be nice if we could do this in a fashion that was independant of the various tool options that exist to manage things.


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--
] Never tell me the odds! | ipv6 mesh networks [ ] Michael Richardson, Sandelman Software Works | IoT architect [ ] mcr@sandelman.ca http://www.sandelman.ca/ | ruby on rails [





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Henrique de Moraes Holschuh <hmh@debian.org> writes:

On Wed, 01 Sep 2021, Bjørn Mork wrote:

ifupdown has this extremely annoying misfeature that it forces a release
on shutdown, both for DHCP and DHCPv6. The automatic release on every

This is *highly* desired *on IPv4*, wherever address pools are scarce.

I disagree.

You'll always need enough addresses for all your clients. If you have a
stable set of clients, then there is no problem letting a client reboot
without releasing the address.

If you have a constant client churn, like for example a public hotspot,
then you should definitely not depend on clients releasing their address
on shutdown. You need to set a short enough lease time. Preferably
still long enough to keep the address over a reboot.

Releasing the address on shutdown doesn't solve anything. It just
creates unnecessary problems.

The correct thing would likely be: do not do it on IPv6, but still do it
on IPv4.

Then at least make it configurable.


Bjørn

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On Wed, 01 Sep 2021, Bjørn Mork wrote:

ifupdown has this extremely annoying misfeature that it forces a release
on shutdown, both for DHCP and DHCPv6. The automatic release on every

This is *highly* desired *on IPv4*, wherever address pools are scarce.

The correct thing would likely be: do not do it on IPv6, but still do it
on IPv4.

--
Henrique Holschuh

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