Bug in bb 1.5.0 ifupdown applet

[Denis Vlasenko]

On Tuesday 01 May 2007 02:27, Nathan Angelacos wrote:
> Hello,
> 
> The ifupdown applet in 1.5.0 appears to have a bug that was not present
> in 1.4.1.  The bug is that /var/run/ifstate is not updated with all
> interfaces if an interface stanza calls ifup statement to bring up a
> second interface.

1.4.1 never reads /var/run/ifstate. It only writes it.
So I highly doubt that 1.4.1 was better than 1.5.0.
Most likely it was broken in a different way.

Anyway, I'm attaching full diff between 1.4.1 and current svn
for easy reference.

> Given the following interfaces file:
> 
> iface lo inet static
>     address 127.0.0.1
>     netmask 255.0.0.0
>     up ifup tunl
>     down ifdown tunl
> 
> iface tunl inet manual
>     up modprobe ipip || true
>     up ip tun add tunl mode ipip local 127.0.0.1 remote 192.168.0.1
>     up ip link set tunl up
>     down ip link set tunl down
>     down ip tunl del

So you configured "ifup lo" to spawn another: "ifup tunl".

> "ifup lo" correctly brings up lo and the tunl interface.  However,
>  /var/run/ifstate only lists "lo=lo".
> 
> An strace for "ifup lo" shows:
> 
> 1. the "parent" ifup reads /var/run/ifstate
> 2. the "parent" forks to run the child ifup
> 2. the "child" ifup reads /var/run/ifstate
> 3. the "child" writes its interface to /var/run/ifstate
> 4. the "child" exits
> 5. the "parent" writes its interface to /var/run/ifstate, using the info
> from step 1
> 
> That is, the parent does not re-read ifstate before writing.

You can attempt to go after these solutions:

(a) provide a patch for ifupdown to read/write
    /var/run/ifstate AFTER child if done.

(b) stop using ifup for network configuration, as it is unable
    to cover more complex cases anyway (like firewalls, traffic shaping etc).
--
vda
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