ifup will fail if IPv6 has been compiled in the kernel

Are there any known workarounds?
I tried replacing modprobe with an empty shell script that does nothing but exit with no error with no luck.

This also affects OpenVZ, cf.
  http://forum.openvz.org/index.php?t=msg&goto=25378

Seems like this was b0rked in 0.6.8ubuntu3:
  https://launchpad.net/ubuntu/+source/ifupdown/0.6.8ubuntu3
which refers to bug #7091:
  https://bugs.launchpad.net/ubuntu/+bug/7091

I'll try to cook up a patch for this...

ugh. No idea what language the ifupdown sources are written in. I guess the following patch might help, I subscribed fabbione to this bug, he commited the original patch.

diff -u ifupdown-0.6.8ubuntu8.orig/ifupdown.nw ifupdown-0.6.8ubuntu8/ifupdown.nw
--- ifupdown-0.6.8ubuntu8.orig/ifupdown.nw 2007-09-20 00:45:09.000000000 +0200
+++ ifupdown-0.6.8ubuntu8/ifupdown.nw 2008-03-28 00:37:59.000000000 +0100
@@ -4127,7 +4127,7 @@
                                  /address/ is dependent on this choice.
     mtu size -- MTU size
   up
- modprobe -Q ipv6
+ modprobe -Q ipv6 || true
     ifconfig %iface% [[media %media%]] [[hw %hwaddress%]] [[mtu %mtu%]] up
     ifconfig %iface% add %address%/%netmask%
     [[ route -A inet6 add ::/0 gw %gateway% %iface% ]]

+1
This appears to be making my Linode sad. :(

@Malte: The patch seems to break debuild for me; one of the tests is failing. Does it work for you?

@Matt: I haven't actually tried it, the ifupdown source looks like gobbeldygook to me, I just put a command which *should* fix it where it would do. That will work only if ifupdown.nw understand shell syntax of course, no idea if thats the case.

I had the problem on a vserver (which doesn't even have modutils installed because it can't load any modules anyway) and "fixed" it by symlinking modprobe to /bin/true; not usable for most people probably but works for me.

Somebody who actually knows ifupdown has to have a look at this. A fix which might work for you is just removing the modprobe line from ifupdown.nw.

I researched this a bit more. It appears it's modprobe that is actually broken... modprobe -Q *should* work as intended here, but the modprobe source doesn't seem to implement the -Q flag in practice. I've opened bug 210891 to address this.

I completely confirm. I have the kernel with compiled IPv6 support and modules turned off. I spent two days of looking for a fix. I found the good and easy workaround on some forums.

# ln -s /bin/true /sbin/modprobe

Now everything works great. I hope that somebody patch source files of ifupdown so IPv6 support was checked.

Ah, this bug again. Here is a fixed patch which takes care of the test cases as well. If somebody could test it and poke the ifupdown maintainers to finally include it, I'd be happy.

Well, is someone in general deals with this package? This bug report was added exactly one year ago and nobody officialy fix this. :/ Can somebody inform ifupdown attendants?

Malte - your patch seemed to work for me.

debdiff attached

@Matt: If you try to take the credits for a patch you didn't originally create, you should at least create a complete patch: You forgot to apply the patch to inet6.defn. Oh, and maybe you should include a link to this bug in the changelog as it is done with the other entries.

@Malte: I'm not really interested in who gets credit for the solution, I was simply trying to add a patch that could hopefully be merged as seamlessly as possible. I had actually intended to upload the fixed package to my ppa for testing, however I'm experiencing technical difficulties preventing me from doing so at the moment. As far as names are concerned, I can't gpg sign a patch/deb as you, so I'm more or less stuck with using my own name there.

I believe the change to inet6.defn in your version is technically incorrect. The file appears to be dynamically generated on build, so changes there are not necessary.

Linking to the bug is a good idea, however, thanks.

New debdiff with modified ChangeLog.

Updated packages for intrepid are now available in my PPA for testing:

deb http://ppa.launchpad.net/cybrmatt/ubuntu intrepid main
ifupdown_0.6.8ubuntu12~ppa1_i386.deb

or

https://launchpad.net/%7Ecybrmatt/+archive/+files/ifupdown_0.6.8ubuntu12~ppa1_i386.deb
https://launchpad.net/%7Ecybrmatt/+archive/+files/ifupdown_0.6.8ubuntu12~ppa1_amd64.deb

@Matt: Sorry for the harsh words, was a bad day.

I'm not sure where the inet6.defn file is generated from, but it is included in the tarball so it should be patched as well.

Any progress on getting this fixed in hardy? Right now I can't configure my router with a static IPv4 and IPv6 address on the same interface using the interfaces file. I have to resort to a custom script to set the IPv6 address.

This appears to be a duplicate of bug #107432, which was fixed in ifupdown 0.6.8ubuntu16. Changelog:

ifupdown (0.6.8ubuntu16) jaunty; urgency=low

  * modprobe failures for ipv6 are benign as the module is likely built-in.
    (LP: #107432)
  * modprobe -Q is now deprecated and going away, move to using -q.
  * modprobe for ipv6 should honour the blacklists.
  * update all generated files to match their source versions (*.defn,
    main.c).