FreeBSD if_wg POINTTOPOINT and MULTICAST behaviour

[Toke Høiland-Jørgensen]

Toke Høiland-Jørgensen <toke at toke.dk> writes:

> Stefan Haller <stefan.haller at stha.de> writes:
>
>> Hi Jason,
>>
>> On Thu, Apr 15, 2021 at 06:05:03PM -0600, Jason A. Donenfeld wrote:
>>> I spent the day playing around with bird and babel and sorted out
>>> FreeBSD's v6 situation. Basically, ff00::/8 addresses are treated
>>> differently, and they're blocked unless the interface sets
>>> IFF_MULTICAST. So I've committed
>>> https://git.zx2c4.com/wireguard-freebsd/commit/?id=a7a84a17faf784857f076e37aa4818f6b6c12a95
>>> to do this.
>>
>> That is also what I observed. Without IFF_MULTICAST I see the following
>> error in bird's log:
>>
>> bird[8045]: babel1: Socket error: IPV6_MULTICAST_IF: Can't assign requested address
>> bird[8045]: babel1: Cannot open socket for wg1
>>
>>> Stefan - please let me know if those work for you. In my testing thus
>>> far, things seem to work for me.
>>
>> After applying Toke's patch for bird and your Wireguard patch in
>> a7a84a17faf784 everything is working as before (with minor config
>> changes).
>>
>> Just for the record, my previous configuration looked like this (using
>> POINTTOPOINT interfaces, I use ifconfig to set the peer address):
>>
>>> [Interface]
>>> ...
>>> Address = fe80::5/64
>>> PostUp = ifconfig %i inet 169.254.42.5/32 169.254.42.2
>>
>> My new configuration without POINTTOPOINT, but only a single peer
>> directly attached to other side of the wg tunnel:
>>
>>> [Interface]
>>> ...
>>> Address = 169.254.42.5/32, fe80::5/64
>>> PostUp = route add 169.254.42.2 -iface %i
>>
>> So for me everything works as expected again. A big thanks to all of you for
>> figuring out what was going wrong and getting it fixed so quickly.
>
> Great! You're welcome :)

Stefan, any chance you could test this patch to Bird (*instead of* the
previous one that removes the check from the Babel code)?

-Toke

diff --git a/sysdep/bsd/krt-sock.c b/sysdep/bsd/krt-sock.c
index c2faa23dd44f..cd89544063c7 100644
--- a/sysdep/bsd/krt-sock.c
+++ b/sysdep/bsd/krt-sock.c
@@ -665,6 +665,9 @@ krt_read_ifinfo(struct ks_msg *msg, int scan)
   else
     f.flags |= IF_MULTIACCESS;      /* NBMA */
 
+  if (fl & IFF_MULTICAST)
+    f.flags |= IF_MULTICAST;
+
   iface = if_update(&f);
 
   if (!scan)