Bug#806949: ifupdown: some tweaks to networking.service

[Michael Biebl]

Am 03.12.2015 um 15:08 schrieb Martin Pitt:
> 
> Guus Sliepen [2015-12-03 13:44 +0100]:

>>>    In the medium term I'd be interested in cleaning this up, though.
>>>    IMHO there needs to be a proper ifupdown-wait-online.service which
>>>    just starts the virtual interfaces, let all the real ones be
>>>    handleld by udev hotplug rules, and just waits until all "auto"
>>>    services are up. This avoids the race condition and unnecessary
>>>    blocking on udev settle. But this should be discussed in a separate
>>>    bug, and I'll also send one for moving the "allow-hotplug" handling
>>>    bits into ifupdown (where they fit much better than in the udev
>>>    package).
>>
>> Yes. The only problem though is that it requires the admin to correctly
>> specify which interfaces are "auto" and which are "hotplug", because
>> ifupdown cannot really figure that out itself. And there might be some
>> cases where a virtual interface depends on one or more hotpluggable
>> ones.

I actually think this ifupdown-wait-online service should block for
allow-hotplug devices as well.

> Just for the record, Ubuntu has a fairly different approach there: It
> never supported "allow-hotplug" really, udev rules dynamically bring
> up both "auto" and "allow-hotplug" devices, and there is an
> implementation of "ifup-wait-all-auto.service" similar to
> systemd-networkd-wait-all-auto.service that waits for all "auto"
> interfaces in /e/n/i to be up for up to 2 minutes, and then continues
> the boot.

Some time ago, I hacked together a little PoC [1].
It considers the "network up" as soon as one interface (besides lo) has
been configured.
I guess that would be ok for the majority of cases.
If a interface has also a IPv6 config, it might make sense to wait for
both IPv6 and IPv4 config to be complete.

With this little hack, ifupdown under systemd behaved much better, since
network-online.target was now properly hooked up for auto or
allow-hotplug interfaces, and stuff like NFS mounts worked reliably (at
least for simple ifupdown configurations).

Michael

[1] https://people.debian.org/~biebl/ifupdown-wait-online.tar.gz
-- 
Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

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