Add file descriptor support

Cargo.toml

@@ -20,7 +20,7 @@ log = "0.4"
 mio = { version = "0.8", features = ["os-poll", "net", "os-ext"] }
 nix = { version = "0.26", features = ["process", "signal"] }
 prctl = "1.0"
-smoltcp = { version = "0.9", git = "https://github.com/smoltcp-rs/smoltcp.git", features = ["std"] }
+smoltcp = { version = "0.9", git = "https://github.com/blechschmidt/smoltcp", branch = "android", features = ["std"] }
 thiserror = "1.0"
 url = "2.3"
 

src/lib.rs

@@ -18,6 +18,11 @@ pub struct Proxy {
     pub credentials: Option<Credentials>,
 }
 
+pub enum NetworkInterface {
+    Named(String),
+    Fd(std::os::fd::RawFd),
+}
+
 impl Proxy {
     pub fn from_url(s: &str) -> Result<Proxy, Error> {
         let e = format!("`{s}` is not a valid proxy URL");
@@ -83,6 +88,7 @@ impl std::fmt::Display for ProxyType {
 #[derive(Default)]
 pub struct Options {
     virtdns: Option<virtdns::VirtualDns>,
+    mtu: Option<usize>,
 }
 
 impl Options {
@@ -94,6 +100,11 @@ impl Options {
         self.virtdns = Some(virtdns::VirtualDns::new());
         self
     }
+
+    pub fn with_mtu(mut self, mtu: usize) -> Self {
+        self.mtu = Some(mtu);
+        self
+    }
 }
 
 #[derive(Default, Clone, Debug)]
@@ -111,8 +122,12 @@ impl Credentials {
     }
 }
 
-pub fn main_entry(tun: &str, proxy: &Proxy, options: Options) -> Result<(), Error> {
-    let mut ttp = TunToProxy::new(tun, options)?;
+pub fn main_entry(
+    interface: &NetworkInterface,
+    proxy: &Proxy,
+    options: Options,
+) -> Result<(), Error> {
+    let mut ttp = TunToProxy::new(interface, options)?;
     match proxy.proxy_type {
         ProxyType::Socks4 => {
             ttp.add_connection_manager(SocksManager::new(

src/main.rs

@@ -5,8 +5,8 @@ use std::net::IpAddr;
 use std::process::ExitCode;
 
 use tun2proxy::error::Error;
-use tun2proxy::Options;
 use tun2proxy::{main_entry, Proxy};
+use tun2proxy::{NetworkInterface, Options};
 
 #[cfg(target_os = "linux")]
 use tun2proxy::setup::{get_default_cidrs, Setup};
@@ -89,7 +89,8 @@ fn main() -> ExitCode {
             }
         }
 
-        main_entry(&args.tun, &args.proxy, options)?;
+        let interface = NetworkInterface::Named(args.tun);
+        main_entry(&interface, &args.proxy, options)?;
 
         Ok(())
     })() {

src/tun2proxy.rs

@@ -1,6 +1,6 @@
 use crate::error::Error;
 use crate::virtdevice::VirtualTunDevice;
-use crate::{Credentials, Options};
+use crate::{Credentials, NetworkInterface, Options};
 use log::{error, info};
 use mio::event::Event;
 use mio::net::TcpStream;
@@ -260,8 +260,13 @@ pub(crate) struct TunToProxy<'a> {
 }
 
 impl<'a> TunToProxy<'a> {
-    pub(crate) fn new(interface: &str, options: Options) -> Result<Self, Error> {
-        let tun = TunTapInterface::new(interface, Medium::Ip)?;
+    pub(crate) fn new(interface: &NetworkInterface, options: Options) -> Result<Self, Error> {
+        let tun = match interface {
+            NetworkInterface::Named(name) => TunTapInterface::new(name.as_str(), Medium::Ip)?,
+            NetworkInterface::Fd(fd) => {
+                TunTapInterface::from_fd(*fd, Medium::Ip, options.mtu.unwrap_or(1500))?
+            }
+        };
         let poll = Poll::new()?;
         poll.registry().register(
             &mut SourceFd(&tun.as_raw_fd()),

tests/proxy.rs

@@ -12,7 +12,7 @@ mod tests {
     use serial_test::serial;
 
     use tun2proxy::setup::{get_default_cidrs, Setup};
-    use tun2proxy::{main_entry, Options, Proxy, ProxyType};
+    use tun2proxy::{main_entry, NetworkInterface, Options, Proxy, ProxyType};
 
     #[derive(Clone, Debug)]
     struct Test {
@@ -85,7 +85,7 @@ mod tests {
                         Ok(Fork::Child) => {
                             prctl::set_death_signal(signal::SIGINT as isize).unwrap();
                             let _ = main_entry(
-                                TUN_TEST_DEVICE,
+                                &NetworkInterface::Named(TUN_TEST_DEVICE.into()),
                                 &test.proxy,
                                 Options::new().with_virtual_dns(),
                             );