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Re: Incompatible change in the ifupdown hooks interface

Hi Joss,

On Tue, Mar 05, 2013 at 08:39:45PM +0100, Josselin Mouette wrote:

> while investigating on #699749 (which apparently affects many machines
> using NM, but not all of them), I discovered that the interface for
> ifupdown hooks has changed since squeeze.

> >From the manpage: 
>        When  ifupdown is being called with the --all option, before doing any‐
>        thing to interfaces, if calls all the hook  scripts  (pre-up  or  down)
>        with  IFACE set to "--all", LOGICAL set to the current value of --allow
>        parameter  (or  "auto"   if   it's   not   set),   ADDRFAM="meta"   and
>        METHOD="none".   After all the interfaces have been brought up or taken
>        down, the appropriate scripts (up or post-down) are executed.

> After discussing this on IRC, the ifupdown maintainer disagrees this is
> an incompatible interface change. Some of the existing hooks were not
> broken by this change, by pure chance. Some were fixed in subsequent
> uploads since squeeze. At least avahi was not.

> What is the position of the Release Team? 
>       * Is it a bug in avahi (and probably other packages)? 
>       * Is it a bug in ifupdown to have changed the interface?

> Given how close we are to the release, the simplest solution is probably
> to upload a fixed avahi and hope there aren’t any other scripts
> remaining. However this will not fix partial upgrades or manually
> updated scripts.

FWIW, I agree with Andrew that this isn't an interface change; this is a
latent bug in the avahi hook which has merely been exposed by this behavior
change in ifupdown.  ifupdown supports more address families than ipv4 and
ipv6 (specifically, it supports ipx); if a user had configured a system with
only ipx interfaces statically configured (as unlikely as that would be in
the 21st century), it appears that avahi would have misbehaved in the same

I don't know why these --all calls are a useful thing for ifupdown to do,
but I do think it's the responsibility of the avahi package to sensibly
ignore values of $ADDRFAM that it doesn't understand.

Steve Langasek                   Give me a lever long enough and a Free OS
Debian Developer                   to set it on, and I can move the world.
Ubuntu Developer                                    http://www.debian.org/
slangasek@ubuntu.com                                     vorlon@debian.org

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