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Re: NM bug 684242 and other stuff

On 09/25/2012 07:55 PM, Pavel Simerda wrote:

I'll divide my reaction into four parts and post it also to NM mailing list so that anyone can
benefit.

1) DHCPv6 currently works according to IETF standards and has been tested with NetworkManager
commit 70f64fbc4277c636c0a373d6e6eddf0574d53827 before merging the 'ipv6' branch into
master. The problem with setting default route has been fixed in the previous commit
70f64fbc4277c636c0a373d6e6eddf0574d53827. You can look at them for more details.

I have just checkout out 0.9.6.0, ran ./autogen.sh, make, make install and ran NetworkManager.

DHCPv6 works like a charm including RA-originated default route. It even works without any
configuration (just delete it or move it away).

# ip address show dev eth1
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
     link/ether 52:54:00:eb:e9:fb brd ff:ff:ff:ff:ff:ff
     inet 192.168.25.12/24 brd 192.168.25.255 scope global eth1
     inet6 2001:abcd:1:1::1:115b/128 scope global
        valid_lft forever preferred_lft forever
     inet6 fe80::5054:ff:feeb:e9fb/64 scope link
        valid_lft forever preferred_lft forever

# ip -6 route show default
default via fe80::5054:ff:fe44:5d16 dev eth1  proto static  metric 1
default via fe80::20c:42ff:fe13:857b dev eth0  proto kernel  metric 1024  expires 57sec
default via fe80::5054:ff:fe44:5d16 dev eth1  proto kernel  metric 1024  expires 252sec

The routes with metric 1024 are from kernel. NetworkManager wants to make eth1 the default
interface so it creates the same route with metric 1.

The testing server environment is as described in:

https://fedoraproject.org/wiki/Tools/NetworkManager/IPv6#DHCPv6_address_and_DNS_configuration

I'm doing first tests with firewall and selinux disabled (if applicable). If your tests show
different results, please present them in their full beauty.

When you are right, you are right!  Yes, Pavel you very much right!
The small difference between what I had and what is specified for the test is radvd.conf. The configuration that works adds "AdvManagedFlag on;", deletes most of the rest, and has "AdvAutonomous off;". What a difference that made.
Now, my next question. The above was with plugin=ifcfg-rh and I also have a virtual system using plugin=keyfile (I want to made sure that my ddns works). What parameters do I need to add to the keyfile definition so that it works too?
When I tested both virtual systems I removed all previous configuration stuff and let NM create some default configuration files. The results were that plugin=ifcfg-rh worked and plugin=keyfile did not.
For the default plugin=keyfile system you got a SLAAC address and a good default route. If I specify that method=dhcp, then dhcp6 assigns an address and named is updated but there is no good default route.
BTW, my testing that worked was using named/dhcpd/dhcp6 on the server. I now need to test dnsmasq to make sure that it works too. It is possible that for a small network (which is the primary use of dnsmasq), you might not need radvd because dnsmasq does some RA support too. That might be very convenient for the libvirt folks ... if it works or can be made to work. 
2) NetworkManager supports the following methods:

method=auto (this is the automatic configuration described in IPv6 standards including DHCPv6)
method=manual (you can set up addresses here)
method=link-local (global addressing is disabled)

It doesn't currently support all sorts of hybrids. If you want it to support something more than
autoconf (including DHCP) and manual configuration, please file a RFE in bugzilla (if it's not
filed already).

Don't use method=dhcp (aka DHCP only). It never worked.

Don't use method=ignore, it was there to leave everything up to the kernel when NetworkManager
didn't have such good support for IPv6.
DHCP worked for IPv4 because there was a lot of "just make it work" stuff done. But IPv6 is a new ballgame.
I do not know if implementing support for a static, specified default route if worth the effort or not, I do not know that it is needed other than when you do a manual, static configuration.
BTW, I found that I could make some interesting entries in nm-applet's route specification for IPv6 when crashed NetworkManager real hard ... took a reboot to get it back. I will have to collect more info and bugzilla that. 

3) http://tools.ietf.org/html/draft-ietf-mif-dhcpv6-route-option-03

This draft is recycling something that has been proposed for *years*. In my opinion, there is no
need to care about this at all at this point of time. I think mostly only need to care about
the current IPv6 node requirements:

http://tools.ietf.org/html/rfc6434

This is what you can expect from IPv6 configuration daemon. If this document is updated/obsoleted,
then there's time for implementing the change in NetworkManager. Unless, of course, you have a very
good reason to do otherwise.

4) Looking forward to seeing your IPv6 dynamic DNS patch merged. Even though I'm not using dyndns at
all, I'm glad that you are trying to make IPv6 work like IPv4 did for you.
I am looking forward to it too. Unfortunately, while what I have works, it will only work on a Fedora or other RHEL system. I did not realize that the "-F" dhclient command line specification was a Red Hat only patch. So I need to go back and put stuff into a conf file ... that is probably the better way anyway.
With this IPv6 stuff I do feel like I am out in front with a few arrows in my back. My hope is to provide more opportunity to test IPv6 by adding "full" support to qemu/kvm/libvirt virtualization. 

Gene
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