Tun cannot be configured with raw fd

[pronebird]

I have configured utun manually and now basically turning it into raw file descriptor. But then SS creates a new tunnel device configured to 10.0.0.1 ignoring the tun_device_fd setting.

let tun_fd = my_tun_device.as_raw_fd();

let mut local_config = LocalConfig::new(ProtocolType::Tun);
local_config.mode = Mode::TcpAndUdp;
local_config.tun_device_fd = Some(tun_fd);

let server_addr = ServerAddr::SocketAddr(SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::LOCALHOST, 10069,)));
let mut server_config = ServerConfig::new(server_addr, "", CipherKind::NONE);
server_config.set_mode(Mode::TcpAndUdp);

let local_instance_config = LocalInstanceConfig::with_local_config(local_config);
let server_instance_config = ServerInstanceConfig::with_server_config(server_config);

let mut ss_config = Config::new(ConfigType::Local);
ss_config.local = vec![local_instance_config];
ss_config.server = vec![server_instance_config];
ss_config.dns = DnsConfig::System;

shadowsocks_service::run_local(ss_config).await

[zonyitoo]

tun_device_fd was passed correctly to the builder:

shadowsocks-rust/crates/shadowsocks-service/src/local/mod.rs

Lines 428 to 429 in 65eb758

	if let Some(fd) = local_config.tun_device_fd {
	builder.file_descriptor(fd);

which will be set to the tun_config:

shadowsocks-rust/crates/shadowsocks-service/src/local/tun/mod.rs

Lines 70 to 73 in 65eb758

	#[cfg(unix)]
	pub fn file_descriptor(&mut self, fd: RawFd) {
	self.tun_config.raw_fd(fd);
	}

So the problem is: why tun didn't use the provided raw_fd?

Just look through https://github.com/meh/rust-tun/tree/master/src/platform , I realized that only iOS supports the raw_fd configuration. :(

[pronebird]

@zonyitoo darn that explains a lot! Thanks for digging. tun crate seems to be quite out of date and there aren’t any viable alternatives from what I know. Perhaps I will patch it one day. Lotta other things on my radar these days.