Add socket-relay crate with udp support

4 files changed, 291 insertions, 0 deletions

diff --git a/socket-relay/Cargo.toml b/socket-relay/Cargo.toml
new file mode 100644
index 0000000000..b7141bec8f
--- /dev/null
+++ b/socket-relay/Cargo.toml
@@ -0,0 +1,15 @@
+[package]
+name = "socket-relay"
+version = "0.1.0"
+authors = ["Mullvad VPN <admin@mullvad.net>", "Linus Färnstrand <linus@mullvad.net>"]
+description = "A relay for bidirectional sockets. Listens to one address and relays all traffic to another."
+license = "MIT/Apache-2.0"
+keywords = ["socket", "network", "forward", "relay", "proxy"]
+categories = ["network-programming", "asynchronous"]
+
+[dependencies]
+env_logger = "0.4.3"
+error-chain = "0.11"
+futures = "0.1.15"
+log = "0.3"
+tokio-core = "0.1"
diff --git a/socket-relay/src/lib.rs b/socket-relay/src/lib.rs
new file mode 100644
index 0000000000..a342cce2dc
--- /dev/null
+++ b/socket-relay/src/lib.rs
@@ -0,0 +1,7 @@
+extern crate futures;
+#[macro_use]
+extern crate log;
+extern crate tokio_core;
+
+/// UDP based relaying.
+pub mod udp;
diff --git a/socket-relay/src/main.rs b/socket-relay/src/main.rs
new file mode 100644
index 0000000000..7eb6fd50db
--- /dev/null
+++ b/socket-relay/src/main.rs
@@ -0,0 +1,48 @@
+extern crate env_logger;
+#[macro_use]
+extern crate error_chain;
+extern crate tokio_core;
+
+extern crate socket_relay;
+
+use std::net::{IpAddr, Ipv4Addr, SocketAddr};
+use std::thread;
+use std::time::Duration;
+
+use tokio_core::reactor::Core;
+
+error_chain!{}
+
+quick_main!(run);
+fn run() -> Result<()> {
+    env_logger::init().chain_err(|| "Failed to init logging")?;
+
+    let listen_ip = IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1));
+    let listen_port = 53;
+    let listen_addr = SocketAddr::new(listen_ip, listen_port);
+
+    let forward_bind_ip = IpAddr::V4(Ipv4Addr::new(0, 0, 0, 0));
+
+    let forward_ip = IpAddr::V4(Ipv4Addr::new(8, 8, 8, 8));
+    let forward_port = 53;
+    let forward_addr = SocketAddr::new(forward_ip, forward_port);
+
+
+    let mut core = Core::new().chain_err(|| "Unable to create Tokio core")?;
+    let handle = core.handle();
+
+    let relay = socket_relay::udp::Relay::new(listen_addr, forward_bind_ip, forward_addr, handle)
+        .chain_err(|| "Unable to init forwarder")?;
+    println!("Forwarder listening on {}", relay.listen_addr());
+
+    let close_handle = relay.close_handle();
+    thread::spawn(move || {
+        thread::sleep(Duration::from_secs(20));
+        println!("Closing relay");
+        close_handle.close();
+    });
+
+    let result = core.run(relay);
+    println!("result: {:?}", result);
+    Ok(())
+}
diff --git a/socket-relay/src/udp.rs b/socket-relay/src/udp.rs
new file mode 100644
index 0000000000..cc9a9139a1
--- /dev/null
+++ b/socket-relay/src/udp.rs
@@ -0,0 +1,221 @@
+use futures;
+use futures::future::{self, Future};
+use futures::sink::Sink;
+use futures::stream::Stream;
+use futures::sync::mpsc::{channel as sync_channel, Sender as SyncSender};
+use futures::unsync::mpsc::{channel as unsync_channel, Sender};
+
+use std::io;
+use std::net::{IpAddr, SocketAddr};
+use std::result::Result as StdResult;
+use std::time::Duration;
+
+use tokio_core::net::{UdpCodec, UdpSocket};
+use tokio_core::reactor::{Handle, Timeout};
+
+/// The amount of time the forwarding socket is open for replies.
+pub static FORWARD_TIMEOUT_MS: u64 = 60000;
+
+/// Number of slots in internal channel transfering responses back to clients.
+pub static CLIENT_SINK_CHANNEL_SIZE: usize = 10;
+
+
+pub struct Relay {
+    listen_addr: SocketAddr,
+    forwarding_future: Box<Future<Item = (), Error = io::Error>>,
+    close_handle: SyncSender<()>,
+}
+
+impl Relay {
+    /// Sets up relaying from `listen_addr` to `destination_addr`.
+    ///
+    /// `forward_bind_ip` is the local IP the socket that sends to the destination binds to.
+    pub fn new(
+        listen_addr: SocketAddr,
+        forward_bind_ip: IpAddr,
+        destination_addr: SocketAddr,
+        handle: Handle,
+    ) -> Result<Relay, io::Error> {
+        let listen_socket = UdpSocket::bind(&listen_addr, &handle)?;
+        let listen_addr = listen_socket.local_addr()?;
+        debug!("Bound relay listening socket to {}", listen_addr);
+
+        // Split the listening socket into a stream of incoming and a sink for outgoing datagrams.
+        let (client_sink, client_stream) = listen_socket.framed(ServerCodec).split();
+        let (closable_client_stream, close_handle) = closable_stream(client_stream);
+        let client_sink_channel = create_client_sink_channel(client_sink, &handle);
+
+        let forwarding_future = closable_client_stream.for_each(move |(client_addr, data)| {
+            let response_sink = client_sink_channel
+                .clone()
+                .sink_map_err(|_| ())
+                .with(move |data| future::ok((client_addr, data)));
+
+            if let Err(e) = Self::forward(
+                forward_bind_ip,
+                destination_addr,
+                data,
+                response_sink,
+                &handle,
+            ) {
+                error!("Unable to perform forwarding for {}: {}", client_addr, e);
+            };
+            future::ok(())
+        });
+
+        Ok(Relay {
+            listen_addr,
+            forwarding_future: Box::new(forwarding_future),
+            close_handle,
+        })
+    }
+
+    /// Forwards `data` to `destination` and streams all replies into `response_sink`.
+    fn forward<S>(
+        bind_ip: IpAddr,
+        destination: SocketAddr,
+        data: Vec<u8>,
+        response_sink: S,
+        handle: &Handle,
+    ) -> io::Result<()>
+    where
+        S: Sink<SinkItem = Vec<u8>, SinkError = ()> + 'static,
+    {
+        let bind_addr = SocketAddr::new(bind_ip, 0);
+        let socket = UdpSocket::bind(&bind_addr, &handle)?;
+        trace!(
+            "Datagram with {} bytes forwarded from {} to {}",
+            data.len(),
+            socket.local_addr().unwrap_or(bind_addr),
+            destination
+        );
+
+        let (forward_sink, forward_stream) = socket.framed(ServerCodec).split();
+
+        let send_future = forward_sink.send((destination, data)).map_err(|e| {
+            error!("Error while forwarding to destination addr: {}", e);
+        });
+
+        let recv_future = forward_stream
+            .filter_map(move |(addr, data)| if addr == destination {
+                Some(data)
+            } else {
+                None
+            })
+            .map_err(|e| {
+                error!("Error reading datagrams from forward socket: {}", e)
+            })
+            .forward(response_sink)
+            .map(|_| ());
+
+        let network_future = send_future.and_then(|_| recv_future);
+
+        let timeout =
+            Timeout::new(Duration::from_millis(FORWARD_TIMEOUT_MS), &handle)?.map_err(|_| ());
+
+        handle.spawn(network_future.select(timeout).map(|_| ()).map_err(|_| ()));
+        Ok(())
+    }
+
+    pub fn listen_addr(&self) -> SocketAddr {
+        self.listen_addr
+    }
+
+    pub fn close_handle(&self) -> RelayCloseHandle {
+        RelayCloseHandle(self.close_handle.clone())
+    }
+}
+
+impl Future for Relay {
+    type Item = ();
+    type Error = io::Error;
+
+    fn poll(&mut self) -> futures::Poll<Self::Item, Self::Error> {
+        self.forwarding_future.poll()
+    }
+}
+
+impl Drop for Relay {
+    fn drop(&mut self) {
+        self.close_handle().close();
+    }
+}
+
+pub struct RelayCloseHandle(SyncSender<()>);
+
+impl RelayCloseHandle {
+    pub fn close(self) {
+        if self.0.send(()).wait().is_err() {
+            warn!("Relay already closed");
+        }
+    }
+}
+
+
+fn closable_stream<S: Stream + 'static>(
+    stream: S,
+) -> (
+    Box<Stream<Item = S::Item, Error = S::Error>>,
+    SyncSender<()>,
+) {
+    let (close_handle_sink, close_signal_stream) = sync_channel(0);
+    let close_signal_stream = close_signal_stream.map(|_| None).map_err(|_| None);
+    let mapped_stream = stream.map(|t| Some(t)).map_err(|e| Some(e));
+
+    let output_stream = mapped_stream
+        .select(close_signal_stream)
+        // Map close_signal_stream error as Ok(None) and stream error back to S::Error
+        .then(|element| match element {
+            Err(None) => Ok(None),
+            Err(Some(e)) => Err(e),
+            Ok(item) => Ok(item),
+        })
+        // Make the stream end when signaled by close_signal_stream.
+        .take_while(|item| Ok(item.is_some()))
+        // Map Option<S::Item> to S::Item, we know it is a Some from the take_while above.
+        .map(|item| item.unwrap());
+    (Box::new(output_stream), close_handle_sink)
+}
+
+
+/// Create a channel accepting tuples of `SocketAddr` and binary data and forward anything coming
+/// on this channel to the `client_sink`. Returns the sender half of the channel.
+fn create_client_sink_channel<S>(client_sink: S, handle: &Handle) -> Sender<(SocketAddr, Vec<u8>)>
+where
+    S: Sink<SinkItem = (SocketAddr, Vec<u8>), SinkError = io::Error> + 'static,
+{
+    let (channel_sink, channel_stream) = unsync_channel(CLIENT_SINK_CHANNEL_SIZE);
+
+    let forward_future = channel_stream
+        .map_err(|_| None)
+        .forward(client_sink.sink_map_err(|e| Some(e)))
+        .and_then(|_| Ok(()))
+        .map_err(|error: Option<io::Error>| match error {
+            Some(sink_error) => {
+                error!("Error sending response back to client: {}", sink_error);
+            }
+            None => debug!("Closing relay socket sink"),
+        });
+    handle.spawn(forward_future);
+
+    channel_sink
+}
+
+
+/// Internal struct implementing `Codec`. Just so it becomes possible to split a `UdpSocket` into
+/// a sink and a stream.
+struct ServerCodec;
+
+impl UdpCodec for ServerCodec {
+    type In = (SocketAddr, Vec<u8>);
+    type Out = (SocketAddr, Vec<u8>);
+
+    fn decode(&mut self, addr: &SocketAddr, buf: &[u8]) -> StdResult<Self::In, io::Error> {
+        Ok((*addr, buf.to_vec()))
+    }
+
+    fn encode(&mut self, (addr, buf): Self::Out, into: &mut Vec<u8>) -> SocketAddr {
+        into.extend(buf);
+        addr
+    }
+}