Enable the async feature of tun

Use `tun::AsyncDevice` instead of hand-rolling an async tunnel device
with `tun::Device` + sys calls.

Author: MarkusPettersson98

Cargo.lock

@@ -24,8 +24,7 @@ jnix = { version = "0.5.1", features = ["derive"] }
 log = { workspace = true }
 
 [target.'cfg(any(target_os = "linux", target_os = "macos"))'.dependencies]
-tun = "0.7"
-nix = "0.23"
+tun = { version = "0.7", features = ["async"] }
 
 [target.'cfg(windows)'.dependencies]
 talpid-windows = { path = "../talpid-windows" }

talpid-tunnel/Cargo.toml

@@ -1,11 +1,10 @@
 use super::TunConfig;
-use nix::fcntl;
 #[cfg(target_os = "macos")]
 use std::io;
 use std::{
     net::IpAddr,
     ops::Deref,
-    os::unix::io::{AsRawFd, IntoRawFd, RawFd},
+    os::unix::io::{AsRawFd, RawFd},
 };
 use tun::{AbstractDevice, Configuration};
 
@@ -31,10 +30,6 @@ pub enum Error {
     #[error("Unable to open a tunnel device")]
     CreateDevice(#[source] tun::Error),
 
-    /// Failed to apply async flags to tunnel device
-    #[error("Failed to apply async flags to tunnel device")]
-    SetDeviceAsync(#[source] nix::Error),
-
     /// Failed to enable/disable link device
     #[error("Failed to enable/disable link device")]
     ToggleDevice(#[source] tun::Error),
@@ -107,7 +102,7 @@ impl Deref for UnixTun {
 
 /// A tunnel device
 pub struct TunnelDevice {
-    dev: tun::Device,
+    dev: tun::AsyncDevice,
 }
 
 /// A tunnel device builder.
@@ -121,15 +116,7 @@ pub struct TunnelDeviceBuilder {
 impl TunnelDeviceBuilder {
     /// Create a [`TunnelDevice`] from this builder.
     pub fn create(self) -> Result<TunnelDevice, Error> {
-        fn apply_async_flags(fd: RawFd) -> Result<(), nix::Error> {
-            fcntl::fcntl(fd, fcntl::FcntlArg::F_GETFL)?;
-            let arg = fcntl::FcntlArg::F_SETFL(fcntl::OFlag::O_RDWR | fcntl::OFlag::O_NONBLOCK);
-            fcntl::fcntl(fd, arg)?;
-            Ok(())
-        }
-
-        let dev = tun::create(&self.config).map_err(Error::CreateDevice)?;
-        apply_async_flags(dev.as_raw_fd()).map_err(Error::SetDeviceAsync)?;
+        let dev = tun::create_as_async(&self.config).map_err(Error::CreateDevice)?;
         Ok(TunnelDevice { dev })
     }
 
@@ -160,12 +147,6 @@ impl AsRawFd for TunnelDevice {
     }
 }
 
-impl IntoRawFd for TunnelDevice {
-    fn into_raw_fd(self) -> RawFd {
-        self.dev.into_raw_fd()
-    }
-}
-
 impl TunnelDevice {
     #[cfg(target_os = "linux")]
     fn set_ip(&mut self, ip: IpAddr) -> Result<(), Error> {