FreeBSD if_wg POINTTOPOINT and MULTICAST behaviour

Stefan Haller stefan.haller at
Fri Apr 16 08:57:46 UTC 2021

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
> 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

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

My new configuration without POINTTOPOINT, but only a single peer
directly attached to other side of the wg tunnel:

> [Interface]
> ...
> Address =, fe80::5/64
> PostUp = route add -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.

Kind regards,

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