Hi,

On Mi, 2014-07-30 at 17:35 +0200, David Lamparter wrote:

(New patch following in separate mail - I haven't touched
addrconf_sit_config since I have no clue about ISATAP & the likes.)

isatap shouldn't use multicast and afaik output path does block
multicast tx. sit in non-ptp mainly depends on 2002:: or 6rd prefix and
drops others packets. sit-ptp can use multicast.

On Wed, Jul 30, 2014 at 05:14:42PM +0200, Hannes Frederic Sowa wrote:

quoted

On Mi, 2014-07-30 at 02:55 +0200, David Lamparter wrote:

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 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")

Yep, this is poor, but changing this will break user space...

How exactly will this break user space?

Because the multicast routes will always be restored after e.g. a route
flush or manual route deletion. Scripts might depend on this.

quoted

quoted

(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: Stephen Hemminger <stephen@networkplumber.org>

We should install routes before joining LL, I would go with

        idev = addrconf_add_dev(dev);
        if (IS_ERR(idev))
                return;

in addrconf_gre_config etc.

Well, yeah, to be honest I have no clue why these functions are
separated as they are.  Once fixed up, the only difference between
addrconf_gre_config and addrconf_dev_config is the true/false value on
prefix_route for addrconf_addr_gen...  and what the rationale for that
is, I can only consult an oracle for.

Basically this is a slalom run to keep exisisting behaviour and clean up
the code a little bit.

How about pushing the switch(dev->type) down from addrconf_notify into
addrconf_dev_config()?

quoted

Looks like we don't correctly configure ARPHRD_IP6GRE gre tunnels...

IP6GRE doesn't currently auto-generate a link-local address at all, is
that what you meant?  (Yeah we could/should add that too...)

Exactly. 

Thanks,
Hannes