Re: bin/58016: wg-userspace(8) requires explicit route setup

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

The following reply was made to PR bin/58016; it has been noted by GNATS.

From: Taylor R Campbell <riastradh%NetBSD.org@localhost>
To: gnats-bugs%NetBSD.org@localhost, netbsd-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: bin/58016: wg-userspace(8) requires explicit route setup
Date: Sun, 10 Mar 2024 04:53:29 +0000

 If I change wg-userspace(8) to do
 
 	ifmode =3D IFF_BROADCAST|IFF_MULTICAST;
 	if (ioctl(fd, TUNSIFMODE, &ifmode) =3D=3D -1) {
 		close(fd);
 		fd =3D -1;
 	}
 
 when creating the tun(4) interface, then ifconfig(8) output looks like
 this instead:
 
 # ifconfig tun0
 tun0: flags=3D0x8043<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
         status: active
         inet6 fd01::2/64 flags 0
         inet6 fe80::9afa:9bff:fe60:a0d2%tun0/64 flags 0 scopeid 0x4
         inet 10.1.0.2/24 broadcast 10.1.0.255 flags 0
 
 And both inet and inet6 routes work as expected on 10.1.0.0/24
 addresses:
 
 # route -n get -inet 10.1.0.1
    route to: 10.1.0.1
 destination: 10.1.0.0
        mask: 255.255.255.0
  local addr: 10.1.0.2
   interface: tun0
       flags: 0x41<UP,DONE>
  recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     ex=
 pire
        0         0         0         0         0         0         0       =
   0
 
 # route -n get -inet6 fd01::1
    route to: fd01::1
 destination: fd01::
        mask: ffff:ffff:ffff:ffff::
  local addr: fd01::2
   interface: tun0
       flags: 0x141<UP,DONE,CONNECTED>
  recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     ex=
 pire
        0         0         0         0         0         0         0       =
   0
 
 (Still unclear on why, in the default IFF_POINTOPOINT setting of
 tun(4), an explicit route is needed only for IPv4 while the system
 automagically adds the necessary route for IPv6.)