`ocserv` is a VPN server which follows the openconnect protocol
(https://github.com/openconnect/protocol). The packaging is slightly
inspired by the AUR version
(https://aur.archlinux.org/packages/ocserv/).
This patch initializes the package written in C, the man pages and a
module for a simple systemd unit to run the VPN server. The package
supports the following authentication methods for the server:
* `plain` (mostly username/password)
* `pam`
The third method (`radius`) is currently not supported since `nixpkgs`
misses a packaged client.
The module can be used like this:
``` nix
{
services.ocserv = {
enable = true;
config = ''
...
'';
};
}
```
The option `services.ocserv.config` is required on purpose to
ensure that nobody just enables the service and experiences unexpected
side-effects on the system. For a full reference, please refer to the
man pages, the online docs or the example value.
The docs recommend to simply use `nobody` as user, so no extra user has
been added to the internal user list. Instead a configuration like
this can be used:
```
run-as-user = nobody
run-as-group = nogroup
```
/cc @tenten8401
Fixes #42594
