On Mi, 2014-07-30 at 18:23 +0200, David Lamparter wrote:

On Wed, Jul 30, 2014 at 06:12:35PM +0200, Hannes Frederic Sowa wrote:

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On Mi, 2014-07-30 at 17:58 +0200, David Lamparter wrote:

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This is an alternate version, yanking the switch() down and removing
dev_config/gre_config duplication.  I have no idea what rationale is behind
prefix_route - the result is a fe80::/64 route, but no address, which is not a
functioning configuration.  Jiri, you touched this just a few weeks ago, can
you comment?  (The "XXX: why is GRE special?")

Sure, it is valid. You can still use global addresses to talk to link
local addresses on the same link, even from another interface.

Okay, well, that may give some purpose to it, but doesn't really explain
why GRE is special in this regard...

(And it's a violation of RFC4291 section 2.1 - "All interfaces are
required to have at least one Link-Local unicast address" - and I'd bet
on ndisc doing weird things in a setup like that.)

Yep - sure. But we also allow someone to remove the ll address manually.
And people did do that to transition the interface into an
disable_ipv6=1 mode, which had its own problems.

We don't care if the user does rfc compliant configurations. :)
The settings in the kernel should just be reasonable.