On Thu, Jul 31, 2014 at 09:37:34PM +0200, Hannes Frederic Sowa wrote:

On Do, 2014-07-31 at 12:06 -0700, David Miller wrote:

quoted

From: David Lamparter <redacted>
Date: Wed, 30 Jul 2014 17:39:57 +0200

quoted

GRE devices, for some reason, were coming up with an autoconfigured
address, but no ff00::/8 route in the local table.  This breaks any kind
of multicast, in particular OSPFv3, mDNS, - and ND.  In fact, IPv6 only
works at all because there is little need for ND on PtP devices.

Adding any other IPv6 address on the device from userspace would rectify
this issue through inet6_addr_add()/addrconf_add_dev() - and would leave
the route around even if the address was later removed.  (This is
probably why this issue was not discovered earlier.  AFAICS it has been
there from the beginning, e.g. aee80b5 "generate link local address for
GRE tunnel")

(Note: multicast is supported on GRE devices of all kinds, including PtP
GRE, P-t-Mcast GRE and NBMA-GRE.)

Fixes: aee80b54b235 (ipv6: generate link local address for GRE tunnel)
Signed-off-by: David Lamparter <redacted>
Cc: Hannes Frederic Sowa <redacted>
Cc: Stephen Hemminger <stephen@networkplumber.org>

Hannes, are you OK with this version?  Please ACK if so.

The alternate version does provide the same semantic change and makes
the code more readable. Both changes are technically correct, I acked
the alternate version already.

Give me a few min, I'll go base the other one on this one, that way
there's one 2-line patch changing semantics (this one) and another
50-line patch just mechanically moving stuff around.

-David