Hi Jason, Thanks for your clarification. I understand that setting this flag would be a false promise to userspace, because generally Wireguard is point-to-multipoint and doesn't copy messages to multiple peers (which is not exactly necessary in my case, where only a single peer is configured on both sides).
I just wanted to ensure that the introduced change was intentional before looking into other directions, hence my question. On Wed, Apr 14, 2021 at 02:24:20PM -0600, Jason A. Donenfeld wrote: > Does bird completely ignore interfaces without it? Is there no setting > to change that? At least a brief look at the code suggests this: [1] The Babel protocol seems to rely on well-known *link-local* IPv6 multicast addresses. I did not find anything related to unicast "hello" messages in the RFC or in the implementations. (OSPF is similar, but as far as I remember unicast hellos are explicitly allowed.) One odd thing I noticed: On Linux (5.11.13-arch1-1, so quite recent), the interface does not list the MULTICAST flag and the interface is still used by bird: # ip l show dev wg1 4: wg1: <POINTOPOINT,NOARP,UP,LOWER_UP> mtu 1400 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000 I will have a closer look why it doesn't work on FreeBSD but the same thing works on Linux. I am probably missing something important. Kind regards, Stefan [1]: https://gitlab.nic.cz/labs/bird/-/blob/9c41e1ca3e93d4498eaa085139caf1545e08c1d8/proto/babel/babel.c#L1662
