I have finished a syncthing-relaysrvpackage for arch linux. Since there are no regular releases (yet?) I created a -git package for the time being. So, if you want to host a relay just install that package with your favorite AUR helper. I prefer pacaur:
$ pacaur -S syncthing-relaysrv-git
It can be started with systemd:
$ sudo systemctl start syncthing-relaysrv.service
It is packaged like this:
During install time a syncthing-relaysrv user and group is created.
The homedir of that user is /var/lib/syncthing-relaysrv.
The shell /bin/nologin is used.
The systemd service runs under the user syncthing-relaysrv with an active chroot(2) in his homedirectory, where the certificate and the private key are being stored.
If you want to use that setup on another systemd enabled distro, you have to:
Create a user/group syncthing-relaysrv with homedir /var/lib/syncthing-relaysrv
Pick the service file and drop it in /etc/systemd/system/
Could this be made as a simple VirtualBox VM? Audrius pointed out somewhere else that it does not require a lot of resources so if that is possible it could be run under Windows machine without somebody managing the build.
Sorry, I did not realize that there were builds for windows (I wrongly assumed that since 0.12 was still in beta relaysrv was only build for Linux, BSD and such ) I am waiting for 0.12 to leave Beta status to start using it