Re: wg(4) listen on a specific interface / address

Hi Pierre,
The error may indicate that port 53 on 127.0.0.1 is already used by
another service. This appears to be confirmed by your netstat example.
This is probably a dns service.
Hope this helps explain the error.
Joe

-------- Original message --------
From: Pierre Emeriaud <petrus.lt+openbsd@gmail.com>
Date: Wed, 28 Oct 2020, 10:36 am
To: misc <misc@openbsd.org>
Subject: wg(4) listen on a specific interface / address

Howdy misc@,

I have a fairly complicated setup with lots of interfaces, a couple
of
rdomains etc.

I'd like wireguard to listen only on an IP address, not all. But if
my
understanding of ifconfig(8) is correct, this doesn't seem possible
currently:

wgport port
Set the UDP port that the tunnel operates on. _The interface will
bind to INADDR_ANY and IN6ADDR_ANY_INIT._

I guess this the reason for the following behaviour?

$ doas ifconfig wg0 wgport 53
ifconfig: SIOCSWG: Address already in use
(the error message is generic I guess - but confusing imho)

$ netstat -natfinet | grep 53
tcp 0 0 127.0.0.1.53 *.*
LISTEN
udp 0 0 127.0.0.1.53 *.*

$ netstat -T1 -natfinet | grep 53
udp 0 0 127.0.0.1.53 *.*

Is there a way to circumvent this restriction? (is there a reason
behind it maybe?)

thanks
--
pierre