Multiple IPv6 RAs and static routes with metric 1

[Martin Jackson <mhjacks swbell net>]

Hello,

First, let me thank you for all of your hard work in developing and 
maintaining network-manager.  It makes life with a Linux laptop much 
simpler.

I have observed a behavior in network-manager in both Ubuntu (12.10) and 
Fedora (18).  In the presence of multiple routers advertising defaults, 
n-m seems to insert a static default route for one of them, with metric 
1.  Here is example output from my Fedora system:

default via fe80::5054:ff:fe01:b6dc dev eth0  proto static  metric 1
default via fe80::5054:ff:fe01:b6dc dev eth0  proto ra  metric 1024 
expires 2sec
default via fe80::5054:ff:fe2f:62c2 dev eth0  proto ra  metric 1024 
expires 9sec

The Ubuntu system's output looks similar.

I believe that the addition of the "static metric 1" route is incorrect, 
as static routes of this type persist even when the router in question 
is no longer doing router advertisements.  In that case, the system will 
use that route in preference to the other router, which may still be 
doing router advertisements.  This creates issues when multiple routers 
are correctly advertising on the same link, and the intention is to 
provide a failover capability, without the complications of a first hop 
redundancy protocol.

I am in control of both of the advertising routers and can enable debug 
if needed on either the client systems or the advertising routers (which 
are virtual Ubuntu systems running Quagga).

I have filed a bug with Ubuntu 
(https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/1101825), but 
this seemed like a better place to address this - I see that recently 
there has been some discussion about IPv6 semantics on this list and 
some recent patches for IPv6, so this discussion might be timely.

Thanks,
Marty