Added configs for snap daemons

[fertkir]

Currently if you run snap start shadowsocks-rust.ssserver-daemon it will fail because of the missing config.

This patch adds paths to config files. All a user needs to do is to add desired local/server configs to $SNAP_COMMON directory.

Still there's a problem, that only one sslocal/ssserver daemon instance is allowed.
With ssserver you can work around this by runing multiple servers in one process (shadowsocks config allows it).
But with sslocal this is, alas, impossible.

[zonyitoo]

shadowsocks-rust/src/config.rs

Lines 59 to 66 in 0c4f9da

	// UNIX global configuration file
	#[cfg(unix)]
	{
	let global_config_path = Path::new("/etc/shadowsocks-rust/config.json");
	if global_config_path.exists() {
	return Some(global_config_path.to_path_buf());
	}
	}

/etc/shadowsocks-rust/config.json is already in the default path. It should be able to read the config in $SNAP_COMMON in the current implementation.

[fertkir]

I don't think that having one config file for both ssserver and sslocal is very usable, since same config fields mean different things for server and local. AFAIU, server and local need separate configs.

[zonyitoo]

Why would you run sslocal and ssserver simotanously on the same machine?

On the other hand, add these local.json and server.json into src/config.rs.

[fertkir]

Added, please review

[fertkir]

Also, I would like to be able to run multiple instances of sslocal.
Here they say that it's impossible to run multiple instances of a snap daemon: https://forum.snapcraft.io/t/run-multiple-service-instances/35233
ssserver supports having 2 instances as a one process (I can add multiple configs to "locals' field).
But sslocal, unfortunately, does not support anything like this (it instead load-balances between configs in "servers" field).

Do you know any workaround?

[zonyitoo]

I don't know. I run my own services with handwriting systemd service files.

[fertkir]

Me too. But when running snaps with handwritten systemd service, journalctl doesn't show the logs.

[zonyitoo]

Hmm, shouldn't we also support config.json?

[fertkir]

It is used if server.json/local.json is not provided:

 let config_files = vec![config_file, "config.json"];