Remove IPv6 ND prefix on ethernet disconnect?

Remove IPv6 ND prefix on ethernet disconnect?

[Harald Welte]

Hi all,

I know I've lost a bit touch with the Linux networking area in recent
years...

Nonetheless, there's one thing that's been bugging me for a long time
and I'm thinking of investing some time to resolve it.  Before doing
that, I'm curious to see if there are existing solutions or existing
discussions that I've missed on the subject:

Imagine a setting where somebody is carrying a laptop around all day,
visiting several sites (office, customer, home,...) without rebooting
the machine (suspend to ram or disk).

You start at home in the morning, you get an IPv6 prefix via
auto-discovery, everything is fine.  Now you move along to your office,
but despite the link down and link up events, the IPv6 prefix remains
configured.

You may or may not get a new prefix, but based on my experience, in both
cases you experience errors following up:
1) in the case of the new prefix, the old default route/prefix is still
   used
2) in case there is no new prefix, the kernel happily sends ipv6 packets
   to the non-existant router of a completely different network.

Now I presume that those things are supposedly resolved by
NetworkManager, but I don't really see why a complex and large userspace
program should be required for something as simple as removing prefixes
that have prevously been added automatically.

My point is: If it's the kernel that automatically adds it, why is it
not the kernel that automatically deletes it when it is no longer safe
to assume it is valid (such as after loosing the link)?

Any input is appreciated. Regards,
	Harald
-- 
- Harald Welte <laforge@gnumonks.org>           http://laforge.gnumonks.org/
============================================================================
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

Re: Remove IPv6 ND prefix on ethernet disconnect?

[Hagen Paul Pfeifer]

* Harald Welte | 2011-06-22 23:41:29 [+0200]:

>My point is: If it's the kernel that automatically adds it, why is it
>not the kernel that automatically deletes it when it is no longer safe
>to assume it is valid (such as after loosing the link)?

Is loosing the link a sufficient criterion to restart ND? IMHO it is superior
to keep the same IP address (I assume privacy extension enabled) in the same
network if you lose the link artificial.

Environments where the link goes down and up again may suffer from such a
behavior. Maybe a script in Network Manager may be the better place. For me it
sounds like a policy thing which should not handled in the kernel.

But yes Harald, I understand your objection! ;-)

Hagen