Sunday, September 23, 2012

Call for testing: Upcoming Squeeze point release 6.0.6

We just sent out a new call for testing for the next point release of Debian Squeeze. The last one was back in May, hence there are a bunch of updates. Please test the packages in squeeze-proposed-updates on some machines running squeeze if possible, so that we don't screw up your production machines with bad updates in a week. The point release is scheduled for September 29th, i.e. next Saturday. Don't forget to copy the debian-release mailing list when you encounter regressions. Thanks for your efforts.

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Saturday, September 22, 2012

IPv6 support in debian-installer, take 2

The IPv6 patch set for netcfg (part of debian-installer) has landed in Debian unstable. In follow-up uploads I diverged from the Ubuntu patch set a little bit:
  • I dropped the use of DUID-LL as the client identifier used by the DHCPv6 client. While basically a good idea, because it's predictable, it's also against the RFC to do that. We simply don't know if the network interface is permanently attached to the device. If the NIC that's used for DUID-LL generation is reused for installation in another box, the same identifier would be generated and stored on the machine. That's what DUID-LLT (the default in other software) avoids. As much as I loathe the replacement of the current MAC address-based scheme of DHCPv4 with DUID-LLT, it seems to be more correct to use that instead of DUID-LL, because that identifier is designed to be decoupled from the presence of the NIC. If you want predictable addressing, just enable SLAAC in your broadcast domain and use the EUI-64 address, which already contains the current MAC address.
  • If SLAAC is used, netcfg will activate IPv6 privacy extensions in the installed system by default. They can be turned off by editing /etc/network/interfaces post-installation. This will only affect outgoing traffic, incoming traffic can be addressed at the stable EUI-64 address. (We don't use a randomized interface identifier like Windows does.)
Thanks to Michael Tokarev's recent upload of busybox, we now also have a more featureful ping and ping6 in debian-installer's environment.

Known bugs:
  • As far as I can see, the DUID generated in the debian-installer environment is not copied into the installed system. Given the low prevalence of stateful DHCPv6 for servers I don't consider this a blocker, though.
  • If stateful DHCPv6 is requested by the router advertisement (other config flag being set), the DHCPv6 client will not time out and continuously retry to get an address.
  • According to Debian bug #688273 preseeding of netcfg/use_autoconfig does not work correctly. netcfg/disable_dhcp needs to be re-added as a deprecated preseeding option and mapped onto the use_autoconfig value until somebody comes up with a better scheme.
  • We should state in the installation guide that and can both be used for IPv6-only installation. The installer does not show in the mirror list if a mirror is IPv6-capable.
If you could take another look at a current d-i daily, install a system with it and look if the installed system has a correct network configuration, that would still be appreciated. I also need somebody to test the GNU/kFreeBSD image. I fixed it up to build there but the result might be entirely wrong.

My sincere thanks go to Bernhard Schmidt and Karsten Merker, who successfully completed installations over IPv6 in various environments!

Monday, September 3, 2012

IPv6 support in debian-installer

I tried to continue netcfg's journey to support IPv6 in debian-installer. Matt Palmer wrote a large patch set many moons ago (kudos!) and Colin Watson polished it and included it into Ubuntu. The reason for it not being merged into Debian first was ifupdown. Version 0.7 finally supports IPv6 and only entered Debian unstable by the end of May. Due to a bunch of changes to netcfg, one reason being a Summer of Code project on it, I had to forward-port those 50 patches and add two bug fixes on top. Hence it's possible that I introduced some breakage, even if the result works well for me (apart from one DHCPv6 oddity that cannot be seen from within KVM). The tree can be found in the people/pkern/ipv6 branch. I was unable to check if Ubuntu has introduced any additional patches on top of the old patch set, as I'm not used enough to bzr.

This mini.iso (detached signature) netinst image contains a debian-installer current as of today and two additional patched udebs: netcfg with the aforementioned IPv6 patch set and busybox with ping6 enabled. I'd appreciate if you could go and test it in one (or more) of the following environments: IPv4-only (DHCPv4 / static), wireless (IPv4 / IPv6 as desired, there has been some refactoring), stateless IPv6 autoconfiguration (it even supports RDNSS and DNSSL), stateless IPv6 autoconfiguration with stateless DHCPv6, and stateful DHCPv6. It will try to configure dual stack if possible. Please note that many Debian mirrors are not yet IPv6-enabled. Even prominent hosts like still do not support it. So you'll have to pick one carefully if you want to try IPv6-only installation. (Which worked for me!)

If you have any feedback for me, please leave it here as a comment or mail me at pkern@d.o. Thanks!