tun0 is not assigned IP and routes on OpenBSD

[FiloSottile]

Describe the bug

tailscaled seems to successfully bring up the interface, but the tun0 interface is left unconfigured.

To Reproduce

I am using the following rc unit on an OpenBSD 6.8 machine.

#!/bin/ksh

daemon="/usr/local/sbin/tailscaled"
daemon_flags="--port 0 --tun tun0"

rc_bg="YES"
rc_reload="NO"

. /etc/rc.d/rc.subr

rc_start() {
        ${rcexec} "${daemon} ${daemon_flags} 2>&1 | logger -t tailscaled ${_bg}"
}

rc_stop() {
        ${rcexec} "${daemon} --cleanup ${daemon_flags} 2>&1 | logger -t tailscaled"
        pkill -xf "${pexp}"
}

rc_cmd $1

After starting tailscaled, the interface has no IP.

tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
        index 9 priority 0 llprio 3
        groups: tun
        status: active

If I manually configure the interface, everything works great!

ifconfig tun0 100.114.190.103 255.192.0.0
route add -inet 100.114.190.103/10 100.114.190.103

Version information:

• Device: x86_64 box
• OS: OpenBSD
• OS version: 6.8
• Tailscale version: date.20210104 (built from @latest)

Additional context

I am told by a very reliable source that

the openbsd router implementation is choking on the v6 addrs + routes being sent from the control plane

[bradfitz]

Confirmed. You're hitting:

freebsd doesn't support setting multiple local addrs yet

(Yes, the error message says freebsd on OpenBSD too, yay)

[FiloSottile]

Looks like a duplicate of #1160.

[DentonGentry]

I installed tailscale built from today's tree on an OpenBSD 6.8 VM, and see the same symptom: control: controlclient: restarting map request for "router" health change to new state: freebsd doesn't support setting multiple local addrs yet

tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
        index 5 priority 0 llprio 3
        groups: tun
        status: active

This happens in wgengine/router/router_openbsd.go in the Set() routine:

        // TODO: support configuring multiple local addrs on interface.
        if len(cfg.LocalAddrs) == 0 {
                return nil
        }
        if len(cfg.LocalAddrs) > 1 {
                return errors.New("freebsd doesn't support setting multiple local addrs yet")
        }

This was intended to apply to having multiple IPv4 addresses, where we don't have a suitable aliases implementation for OpenBSD. However with the addition of IPv6 we now have len(cfg.LocalAddrs) == 2, which we definitely could support.

[DentonGentry]

I think this can be pretty straightforward to resolve, if we want to support one IPv4 and one IPv6 address on the interface. I had it use a /48 prefix, like FreeBSD now does, so as to not need to deal with IPv6 routes.

openbsd# ifconfig tun0
tun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1280
        index 9 priority 0 llprio 3
        groups: tun
        status: active
        inet6 fe80::7cb3:edff:feb9:61f8%tun0 ->  prefixlen 64 scopeid 0x9
        inet 100.69.155.47 --> 0.0.0.0 netmask 0xffffffff
        inet6 fd7a:115c:a1e0:ab12:4843:cd96:6245:9b2f ->  prefixlen 48

[DentonGentry]

Seems to work, I can ping another machine on my tailnet using both IPv4 and IPv6:

openbsd# ping 100.84.216.111
PING 100.84.216.111 (100.84.216.111): 56 data bytes
64 bytes from 100.84.216.111: icmp_seq=0 ttl=64 time=31.461 ms
64 bytes from 100.84.216.111: icmp_seq=1 ttl=64 time=3.798 ms
64 bytes from 100.84.216.111: icmp_seq=2 ttl=64 time=1.576 ms
^C
--- 100.84.216.111 ping statistics ---
3 packets transmitted, 3 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 1.576/12.278/31.461/13.595 ms
openbsd#

openbsd# ping6 fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f
PING fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f (fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f): 56 data bytes
64 bytes from fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f: icmp_seq=0 hlim=64 time=20.596 ms
64 bytes from fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f: icmp_seq=1 hlim=64 time=1.742 ms
64 bytes from fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f: icmp_seq=2 hlim=64 time=1.869 ms
^C64 bytes from fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f: icmp_seq=3 hlim=64 time=1.519 ms
^C
--- fd7a:115c:a1e0:ab12:4843:cd96:6254:d86f ping statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 1.519/6.432/20.596/8.179 ms
openbsd#