Creating UNIX sockets the listen() goroutine that races against the main
one dropping to an unprivileged user may cause startup failure when
privdrop happens before privileged filesystem access.
Setup or fail in New() and only do listen(2) in listen() to avoid this.
```
# yggdrasil -autoconf -user nobody
2024/11/03 21:15:27 Build name: yggdrasil-go
2024/11/03 21:15:27 Build version: 0.5.9
...
2024/11/03 21:15:27 Admin socket failed to listen: listen unix /var/run/yggdrasil.sock: bind: permission denied
```
Rerun, now the order is flipped:
```
# yggdrasil -autoconf -user nobody
2024/11/03 21:15:34 Build name: yggdrasil-go
2024/11/03 21:15:34 Build version: 0.5.9
[...]
2024/11/03 21:15:34 UNIX admin socket listening on /var/run/yggdrasil.sock
[...]
```
Fixes#927.
No need to extract it again when the url package provides it for us:
```
$ jq -n '{"AdminListen":"unix:///tmp/ygg.sock"}' | ./yggdrasil -useconf | grep 'admin socket'
2024/10/08 22:41:11 UNIX admin socket listening on /tmp/ygg.sock
```
Follow-up on #1176
This stood out to me while reading the code: [7:] is skipping "unix://",
so why not do that?
Doing so reveals a bug in the last line changed, where chmod(2) failure
would print just the prefix, not everything but it... easy to miss, but
now this kind of bug can no longer happen.
* Reimplement AddPeer and RemovePeer for admin socket
Fix#950
* Disconnect the peer on `removePeer`
Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>
This refactors the request parsing, as well as improving the output for some request types. It also tweaks `yggdrasilctl` output, which should help with #947.
* Link refactoring
* More refactoring
* More tweaking
* Cleaner shutdowns, UNIX socket support, more tweaks
* Actorise links, remove mutex
* SOCKS support
