[Devel] 2.6.18-ovz028test015 and 2.6.18-ovz028test018 break IPv6
Michael H. Warfield
mhw at WittsEnd.com
Sat Mar 3 09:21:05 PST 2007
Hello,
Introduction... I've been on the users list for a while and just
joined the developers list. Excuse the cross post but I'm not sure
which would be most appropriate.
I work extensively with IPv6. All of my devices are configured for
IPv6 and I actively participate in the global IPv6 network and have for
over 5 years. I'm a member of the North American v6 Task Force,
NAv6TF.org. My name servers, ntp servers, smtp servers, and web servers
all show active IPv6 traffic and have for years. I'm also a big user of
VMware and I'm also the author of an IPv6 paper that's up on their site
somewhere.
So, I'll prefix this with a bit of a rant.
<Rant>
I don't use venet. The way it's implemented, especially vis-a-vis
IPv6, it makes no sense to me at all. the venet0 devices have no
hardware / mac layer addresses so how is IPv6 neighbor discovery and
autoconfiguration protocols suppose to work? These are really
fundamental to the nature of IPv6 and, unless you want to use IPv6
purely like it just IPv4 with fat addresses (which it is NOT) and live
entirely in an IPv4 mind-think cocoon when working with IPv6, how can
you expect this to work with fully implemented IPv6?
The bridged networking of the veth devices seem to be the only viable
way to deal with this. I HAVE tried using venet for IPv6 and failed
miserably.
This is also how I deal with IPv6 on VMware. I never use the local
networking (host local or NAT) devices and only use the bridged devices
there. In the case of VMware, the bridged devices are the default and
you can add the routed or nat'ed devices. That makes a lot more sense
to me.
So IPv6 HAS to work for me. Consequently, I have to work with
everything running over the veth devices. The venet devices just do not
cut it at all with IPv6, so are totally useless to me for both IPv4 as
well as IPv6 (why split the network two ways).
Funny thing is, if you "turn on" IPv6 in the vz configuration files, it
dicks things up royally by trying to force IPv6 routes out through the
venet0 interface, which can't work, and interferes with stateless
autoconfiguration and router discovery configuration. Leaving IPv6 off
in the config, then it doesn't insert bogus routes and everything
configures properly on the veth devices and IPv6 works like a charm.
Interestingly enough, the veth devices DO get their proper link-local
and global-unicast addresses while vnet0 sits there with not even a
link-local address (of course - it has no mac address so how could it
possibly have a link-local address - duh...).
</Rant>
Now... Onto the problem. IPv6 is working sweet with
2.6.18-ovz028test010 on Fedora Core 6. It would be nice to get it up to
the FC6 2.6.19 (soon to be the 2.6.20) rebase but that's ok for now.
When I tried 2.6.18-ovz028test015 and subsequently 2.6.18-ovz028test018,
I found that IPv6 was totally broken. While all my interfaces properly
autoconfigure on test10, stateless autoconf appears to be totally broken
on test15 and test18 and even manual configuration doesn't work (hints
strongly at broken neighbor discovery there).
This may not be an OpenVZ problem, per se, though. Some time in the
very later part of the 2.6.18 kernel.org release updates, a problem was
introduced that broke IPv6. Some patch or another caused nodes to fail
to join the "all nodes multicast" (ff02::1) address. This is critical
to IPv6 router discovery and advertisement, neighbor discovery, and
autoconfiguration. All fall down go boom.
This actually wasn't "discovered" until 2.6.19 but it seems to have
been introduced in a couple of late clicks of 2.6.18 and is not fixed in
the kernel.org tree until 2.6.20-rc5 or so. Fedora Core seems to have
retrofitted the fix into the last couple of clicks of the FC6 2.6.19
(currently 2.6.19-2911) but the stock kernel.org kernels have been
broken in a couple of 2.6.18 releases and, AFAICT, all of the 2.6.19
releases.
This is re-enforced by checking the group memberships on test010 vs
test018 in both host and guest (netstat -g).
Host test010:
IPv6/IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
lo 1 ff02::1
eth0 1 ff02::fb
eth0 1 ff02::1:ff10:f84d
eth0 1 ff02::1
veth0 1 ff02::fb
veth0 2 ff02::1:ff10:f84d
veth0 1 ff02::1
veth1 1 ff02::fb
veth1 1 ff02::1:ff3a:e3e2
veth1 1 ff02::1
veth1006.0 1 ff02::fb
veth1006.0 1 ff02::1:ff01:6
veth1006.0 1 ff02::1
veth1010.1 1 ff02::fb
veth1010.1 1 ff02::1:ff01:100a
veth1010.1 1 ff02::1
veth1026.0 1 ff02::fb
veth1026.0 1 ff02::1:ff01:1a
veth1026.0 1 ff02::1
Host test018:
IPv6/IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
eth0 1 ff02::fb
eth0 1 ff02::1:ff10:f84d
veth0 1 ff02::fb
veth0 1 ff02::1:ff10:f84d
veth1 1 ff02::fb
veth1 1 ff02::1:ff3a:e3e2
veth1006.0 1 ff02::fb
veth1006.0 1 ff02::1:ff01:6
veth1010.1 1 ff02::fb
veth1010.1 1 ff02::1:ff01:100a
Yeah, that would be a problem and is the symptoms reported on lkml.
Here's one of the guest systems (1006 above):
Guest 1006 test010:
IPv6/IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
lo 1 ff02::1
eth0 2 ff02::1:ff01:106
eth0 1 ff02::1
eth1 1 ff02::1:ff01:1106
eth1 1 ff02::1
Guest 1006 test018:
IPv6/IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
eth0 1 ff02::1:ff01:106
eth1 1 ff02::1:ff01:1106
Same problem. Missing the ff02::1 address on every interface. Bad
juju.
I suspect that test15 and test18 picked up the bad IPv6 patch and broke
IPv6. We need a rebase to a working kernel or a retrofit of the patch
from 2.6.20. I have not been able to get the oz patch to patch into the
2.6.19 FC6 kernels, but that would be a good place to start since they
are no have IPv6 working. You might examine those retrofit patches.
Better yet would be to rebase the test series up to 2.6.20.
Mike
--
Michael H. Warfield (AI4NB) | (770) 985-6132 | mhw at WittsEnd.com
/\/\|=mhw=|\/\/ | (678) 463-0932 | http://www.wittsend.com/mhw/
NIC whois: MHW9 | An optimist believes we live in the best of all
PGP Key: 0xDF1DD471 | possible worlds. A pessimist is sure of it!
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