udp: switch to own tokio UdpSocket implementation for performance reasons

6 files changed, 673 insertions, 5 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 08f9950..99ec977 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1300,6 +1300,7 @@ dependencies = [
  "hex 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mio 0.6.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "nix 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "notify 4.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "pnet_packet 0.20.0 (registry+https://github.com/rust-lang/crates.io-index)",
diff --git a/Cargo.toml b/Cargo.toml
index 298c792..36aa823 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -42,6 +42,7 @@ hex = "^0.3"
 notify = "4.0.0"
 rand = "^0.4"
 nix = "^0.10"
+mio = "^0.6"
 pnet_packet = "^0.20"
 snow = { git = "https://github.com/mcginty/snow", features = ["ring-accelerated"], branch = "wireguard" }
 socket2 = "^0.3"
diff --git a/src/interface/peer_server.rs b/src/interface/peer_server.rs
index 42e275c..f9045df 100644
--- a/src/interface/peer_server.rs
+++ b/src/interface/peer_server.rs
@@ -15,7 +15,7 @@ use failure::{Error, err_msg};
 use futures::{Async, Future, Stream, Sink, Poll, unsync::mpsc, stream, future};
 use rand::{self, Rng};
 use socket2::{Socket, Domain, Type, Protocol};
-use tokio_core::net::{UdpSocket, UdpCodec, UdpFramed};
+use udp::{UdpSocket, UdpCodec, UdpFramed};
 use tokio_core::reactor::Handle;
 
 
diff --git a/src/lib.rs b/src/lib.rs
index 90a690e..7ff0944 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -7,16 +7,18 @@
 #![cfg_attr(feature = "cargo-clippy", allow(decimal_literal_representation))]
 
 #[macro_use] extern crate failure;
+#[macro_use] extern crate futures;
 #[macro_use] extern crate lazy_static;
 #[macro_use] extern crate log;
+#[macro_use] extern crate tokio_core;
 
 extern crate base64;
 extern crate blake2_rfc;
 extern crate byteorder;
 extern crate bytes;
 extern crate chacha20_poly1305_aead;
-extern crate futures;
 extern crate hex;
+extern crate mio;
 extern crate nix;
 extern crate notify;
 extern crate pnet_packet;
@@ -25,7 +27,6 @@ extern crate snow;
 extern crate socket2;
 extern crate subtle;
 extern crate test;
-extern crate tokio_core;
 extern crate tokio_io;
 extern crate tokio_uds;
 extern crate tokio_utun;
@@ -34,6 +35,8 @@ extern crate tokio_signal;
 extern crate treebitmap;
 extern crate x25519_dalek;
 
+mod udp;
+
 pub mod consts;
 pub mod cookie;
 pub mod error;
@@ -47,5 +50,3 @@ pub mod time;
 pub mod timer;
 pub mod ip_packet;
 pub mod xchacha20poly1305;
-
-
diff --git a/src/udp/frame.rs b/src/udp/frame.rs
new file mode 100644
index 0000000..c85c873
--- /dev/null
+++ b/src/udp/frame.rs
@@ -0,0 +1,188 @@
+use std::io;
+use std::net::{SocketAddr, Ipv4Addr, SocketAddrV4};
+
+use futures::{Async, Poll, Stream, Sink, StartSend, AsyncSink};
+
+use udp::{ConnectedUdpSocket, UdpSocket};
+
+/// Encoding of frames via buffers.
+///
+/// This trait is used when constructing an instance of `UdpFramed` and provides
+/// the `In` and `Out` types which are decoded and encoded from the socket,
+/// respectively.
+///
+/// Because UDP is a connectionless protocol, the `decode` method receives the
+/// address where data came from and the `encode` method is also responsible for
+/// determining the remote host to which the datagram should be sent
+///
+/// The trait itself is implemented on a type that can track state for decoding
+/// or encoding, which is particularly useful for streaming parsers. In many
+/// cases, though, this type will simply be a unit struct (e.g. `struct
+/// HttpCodec`).
+pub trait UdpCodec {
+    /// The type of decoded frames.
+    type In;
+
+    /// The type of frames to be encoded.
+    type Out;
+
+    /// Attempts to decode a frame from the provided buffer of bytes.
+    ///
+    /// This method is called by `UdpFramed` on a single datagram which has been
+    /// read from a socket. The `buf` argument contains the data that was
+    /// received from the remote address, and `src` is the address the data came
+    /// from. Note that typically this method should require the entire contents
+    /// of `buf` to be valid or otherwise return an error with trailing data.
+    ///
+    /// Finally, if the bytes in the buffer are malformed then an error is
+    /// returned indicating why. This informs `Framed` that the stream is now
+    /// corrupt and should be terminated.
+    fn decode(&mut self, src: &SocketAddr, buf: &[u8]) -> io::Result<Self::In>;
+
+    /// Encodes a frame into the buffer provided.
+    ///
+    /// This method will encode `msg` into the byte buffer provided by `buf`.
+    /// The `buf` provided is an internal buffer of the `Framed` instance and
+    /// will be written out when possible.
+    ///
+    /// The encode method also determines the destination to which the buffer
+    /// should be directed, which will be returned as a `SocketAddr`.
+    fn encode(&mut self, msg: Self::Out, buf: &mut Vec<u8>) -> SocketAddr;
+}
+
+pub enum Socket {
+    Unconnected(UdpSocket),
+    Connected(ConnectedUdpSocket),
+}
+
+/// A unified `Stream` and `Sink` interface to an underlying `UdpSocket`, using
+/// the `UdpCodec` trait to encode and decode frames.
+///
+/// You can acquire a `UdpFramed` instance by using the `UdpSocket::framed`
+/// adapter.
+#[must_use = "sinks do nothing unless polled"]
+pub struct UdpFramed<C> {
+    socket: Socket,
+    codec: C,
+    rd: Vec<u8>,
+    wr: Vec<u8>,
+    out_addr: SocketAddr,
+    flushed: bool,
+}
+
+impl<C: UdpCodec> Stream for UdpFramed<C> {
+    type Item = C::In;
+    type Error = io::Error;
+
+    fn poll(&mut self) -> Poll<Option<C::In>, io::Error> {
+        let (n, addr) = match self.socket {
+            Socket::Unconnected(ref socket) => try_nb!(socket.recv_from(&mut self.rd)),
+            Socket::Connected(ref socket)   => (try_nb!(socket.inner.recv(&mut self.rd)), socket.addr),
+        };
+        trace!("received {} bytes, decoding", n);
+        let frame = try!(self.codec.decode(&addr, &self.rd[..n]));
+        trace!("frame decoded from buffer");
+        Ok(Async::Ready(Some(frame)))
+    }
+}
+
+impl<C: UdpCodec> Sink for UdpFramed<C> {
+    type SinkItem = C::Out;
+    type SinkError = io::Error;
+
+    fn start_send(&mut self, item: C::Out) -> StartSend<C::Out, io::Error> {
+        trace!("sending frame");
+
+        if !self.flushed {
+            match try!(self.poll_complete()) {
+                Async::Ready(()) => {},
+                Async::NotReady => return Ok(AsyncSink::NotReady(item)),
+            }
+        }
+
+        self.out_addr = self.codec.encode(item, &mut self.wr);
+        self.flushed = false;
+        trace!("frame encoded; length={}", self.wr.len());
+
+        Ok(AsyncSink::Ready)
+    }
+
+    fn poll_complete(&mut self) -> Poll<(), io::Error> {
+        if self.flushed {
+            return Ok(Async::Ready(()))
+        }
+
+        trace!("flushing frame; length={}", self.wr.len());
+        let n = match self.socket {
+            Socket::Unconnected(ref socket) => try_nb!(socket.send_to(&self.wr, &self.out_addr)),
+            Socket::Connected(ref socket)   => try_nb!(socket.inner.send(&self.wr)) // TODO check to make sure the address is the connected address
+        };
+        trace!("written {}", n);
+
+        let wrote_all = n == self.wr.len();
+        self.wr.clear();
+        self.flushed = true;
+
+        if wrote_all {
+            Ok(Async::Ready(()))
+        } else {
+            Err(io::Error::new(io::ErrorKind::Other,
+                               "failed to write entire datagram to socket"))
+        }
+    }
+
+    fn close(&mut self) -> Poll<(), io::Error> {
+        try_ready!(self.poll_complete());
+        Ok(().into())
+    }
+}
+
+pub fn new<C: UdpCodec>(socket: Socket, codec: C) -> UdpFramed<C> {
+    UdpFramed {
+        socket,
+        codec,
+        out_addr: SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(0, 0, 0, 0), 0)),
+        rd: vec![0; 64 * 1024],
+        wr: Vec::with_capacity(8 * 1024),
+        flushed: true,
+    }
+}
+
+impl<C> UdpFramed<C> {
+    /// Returns a reference to the underlying I/O stream wrapped by `Framed`.
+    ///
+    /// Note that care should be taken to not tamper with the underlying stream
+    /// of data coming in as it may corrupt the stream of frames otherwise being
+    /// worked with.
+    pub fn get_ref(&self) -> &UdpSocket {
+        match self.socket {
+            Socket::Connected(ref socket) => &socket.inner,
+            Socket::Unconnected(ref socket) => socket
+        }
+    }
+
+    /// Returns a mutable reference to the underlying I/O stream wrapped by
+    /// `Framed`.
+    ///
+    /// Note that care should be taken to not tamper with the underlying stream
+    /// of data coming in as it may corrupt the stream of frames otherwise being
+    /// worked with.
+    pub fn get_mut(&mut self) -> &mut UdpSocket {
+        match self.socket {
+            Socket::Connected(ref mut socket) => &mut socket.inner,
+            Socket::Unconnected(ref mut socket) => socket
+        }
+    }
+
+    /// Consumes the `Framed`, returning its underlying I/O stream.
+    ///
+    /// Note that care should be taken to not tamper with the underlying stream
+    /// of data coming in as it may corrupt the stream of frames otherwise being
+    /// worked with.
+    pub fn into_inner(self) -> UdpSocket {
+        match self.socket {
+            Socket::Connected(socket) => socket.inner,
+            Socket::Unconnected(socket) => socket
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/udp/mod.rs b/src/udp/mod.rs
new file mode 100644
index 0000000..a7196f9
--- /dev/null
+++ b/src/udp/mod.rs
@@ -0,0 +1,477 @@
+#![allow(unused)]
+
+use std::io;
+use std::net::{self, SocketAddr, Ipv4Addr, Ipv6Addr};
+use std::fmt;
+
+use futures::{Async, Future, Poll};
+use mio;
+
+use tokio_core::reactor::{Handle, PollEvented};
+
+/// An I/O object representing a UDP socket.
+pub struct UdpSocket {
+    io: PollEvented<mio::net::UdpSocket>,
+}
+
+mod frame;
+pub use self::frame::{UdpFramed, UdpCodec};
+
+pub struct ConnectedUdpSocket {
+    inner: UdpSocket,
+    addr: SocketAddr,
+}
+
+impl ConnectedUdpSocket {
+    pub fn framed<C: UdpCodec>(self, codec: C) -> UdpFramed<C> {
+        frame::new(frame::Socket::Connected(self), codec)
+    }
+}
+
+impl UdpSocket {
+    /// Create a new UDP socket bound to the specified address.
+    ///
+    /// This function will create a new UDP socket and attempt to bind it to the
+    /// `addr` provided. If the result is `Ok`, the socket has successfully bound.
+    pub fn bind(addr: &SocketAddr, handle: &Handle) -> io::Result<UdpSocket> {
+        let udp = try!(mio::net::UdpSocket::bind(addr));
+        UdpSocket::new(udp, handle)
+    }
+
+    fn new(socket: mio::net::UdpSocket, handle: &Handle) -> io::Result<UdpSocket> {
+        let io = try!(PollEvented::new(socket, handle));
+        Ok(UdpSocket { io: io })
+    }
+
+    /// Creates a new `UdpSocket` from the previously bound socket provided.
+    ///
+    /// The socket given will be registered with the event loop that `handle` is
+    /// associated with. This function requires that `socket` has previously
+    /// been bound to an address to work correctly.
+    ///
+    /// This can be used in conjunction with net2's `UdpBuilder` interface to
+    /// configure a socket before it's handed off, such as setting options like
+    /// `reuse_address` or binding to multiple addresses.
+    pub fn from_socket(socket: net::UdpSocket,
+                       handle: &Handle) -> io::Result<UdpSocket> {
+        let udp = try!(mio::net::UdpSocket::from_socket(socket));
+        UdpSocket::new(udp, handle)
+    }
+
+    /// Provides a `Stream` and `Sink` interface for reading and writing to this
+    /// `UdpSocket` object, using the provided `UdpCodec` to read and write the
+    /// raw data.
+    ///
+    /// Raw UDP sockets work with datagrams, but higher-level code usually
+    /// wants to batch these into meaningful chunks, called "frames". This
+    /// method layers framing on top of this socket by using the `UdpCodec`
+    /// trait to handle encoding and decoding of messages frames. Note that
+    /// the incoming and outgoing frame types may be distinct.
+    ///
+    /// This function returns a *single* object that is both `Stream` and
+    /// `Sink`; grouping this into a single object is often useful for layering
+    /// things which require both read and write access to the underlying
+    /// object.
+    ///
+    /// If you want to work more directly with the streams and sink, consider
+    /// calling `split` on the `UdpFramed` returned by this method, which will
+    /// break them into separate objects, allowing them to interact more
+    /// easily.
+    pub fn framed<C: UdpCodec>(self, codec: C) -> UdpFramed<C> {
+        frame::new(frame::Socket::Unconnected(self), codec)
+    }
+
+    /// Returns the local address that this stream is bound to.
+    pub fn local_addr(&self) -> io::Result<SocketAddr> {
+        self.io.get_ref().local_addr()
+    }
+
+    /// Connects the UDP socket setting the default destination for send() and
+    /// limiting packets that are read via recv from the address specified in addr.
+    pub fn connect(self, addr: &SocketAddr) -> io::Result<ConnectedUdpSocket> {
+        self.io.get_ref().connect(*addr)?;
+        Ok(ConnectedUdpSocket{ inner: self, addr: *addr })
+    }
+
+    /// Sends data on the socket to the address previously bound via connect().
+    /// On success, returns the number of bytes written.
+    pub fn send(&self, buf: &[u8]) -> io::Result<usize> {
+        if let Async::NotReady = self.io.poll_write() {
+            return Err(io::ErrorKind::WouldBlock.into())
+        }
+        match self.io.get_ref().send(buf) {
+            Ok(n) => Ok(n),
+            Err(e) => {
+                if e.kind() == io::ErrorKind::WouldBlock {
+                    self.io.need_write();
+                }
+                Err(e)
+            }
+        }
+    }
+
+    /// Receives data from the socket previously bound with connect().
+    /// On success, returns the number of bytes read.
+    pub fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {
+        if let Async::NotReady = self.io.poll_read() {
+            return Err(io::ErrorKind::WouldBlock.into())
+        }
+        match self.io.get_ref().recv(buf) {
+            Ok(n) => Ok(n),
+            Err(e) => {
+                if e.kind() == io::ErrorKind::WouldBlock {
+                    self.io.need_read();
+                }
+                Err(e)
+            }
+        }
+    }
+
+    /// Test whether this socket is ready to be read or not.
+    ///
+    /// If the socket is *not* readable then the current task is scheduled to
+    /// get a notification when the socket does become readable. That is, this
+    /// is only suitable for calling in a `Future::poll` method and will
+    /// automatically handle ensuring a retry once the socket is readable again.
+    pub fn poll_read(&self) -> Async<()> {
+        self.io.poll_read()
+    }
+
+    /// Test whether this socket is ready to be written to or not.
+    ///
+    /// If the socket is *not* writable then the current task is scheduled to
+    /// get a notification when the socket does become writable. That is, this
+    /// is only suitable for calling in a `Future::poll` method and will
+    /// automatically handle ensuring a retry once the socket is writable again.
+    pub fn poll_write(&self) -> Async<()> {
+        self.io.poll_write()
+    }
+
+    /// Sends data on the socket to the given address. On success, returns the
+    /// number of bytes written.
+    ///
+    /// Address type can be any implementer of `ToSocketAddrs` trait. See its
+    /// documentation for concrete examples.
+    pub fn send_to(&self, buf: &[u8], target: &SocketAddr) -> io::Result<usize> {
+        if let Async::NotReady = self.io.poll_write() {
+            return Err(io::ErrorKind::WouldBlock.into())
+        }
+        match self.io.get_ref().send_to(buf, target) {
+            Ok(n) => Ok(n),
+            Err(e) => {
+                if e.kind() == io::ErrorKind::WouldBlock {
+                    self.io.need_write();
+                }
+                Err(e)
+            }
+        }
+    }
+
+    /// Creates a future that will write the entire contents of the buffer
+    /// `buf` provided as a datagram to this socket.
+    ///
+    /// The returned future will return after data has been written to the
+    /// outbound socket.  The future will resolve to the stream as well as the
+    /// buffer (for reuse if needed).
+    ///
+    /// Any error which happens during writing will cause both the stream and
+    /// the buffer to get destroyed. Note that failure to write the entire
+    /// buffer is considered an error for the purposes of sending a datagram.
+    ///
+    /// The `buf` parameter here only requires the `AsRef<[u8]>` trait, which
+    /// should be broadly applicable to accepting data which can be converted
+    /// to a slice.  The `Window` struct is also available in this crate to
+    /// provide a different window into a slice if necessary.
+    pub fn send_dgram<T>(self, buf: T, addr: SocketAddr) -> SendDgram<T>
+        where T: AsRef<[u8]>,
+    {
+        SendDgram(Some((self, buf, addr)))
+    }
+
+    /// Receives data from the socket. On success, returns the number of bytes
+    /// read and the address from whence the data came.
+    pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
+        if let Async::NotReady = self.io.poll_read() {
+            return Err(io::ErrorKind::WouldBlock.into())
+        }
+        match self.io.get_ref().recv_from(buf) {
+            Ok(n) => Ok(n),
+            Err(e) => {
+                if e.kind() == io::ErrorKind::WouldBlock {
+                    self.io.need_read();
+                }
+                Err(e)
+            }
+        }
+    }
+
+    /// Creates a future that receive a datagram to be written to the buffer
+    /// provided.
+    ///
+    /// The returned future will return after a datagram has been received on
+    /// this socket. The future will resolve to the socket, the buffer, the
+    /// amount of data read, and the address the data was received from.
+    ///
+    /// An error during reading will cause the socket and buffer to get
+    /// destroyed and the socket will be returned.
+    ///
+    /// The `buf` parameter here only requires the `AsMut<[u8]>` trait, which
+    /// should be broadly applicable to accepting data which can be converted
+    /// to a slice.  The `Window` struct is also available in this crate to
+    /// provide a different window into a slice if necessary.
+    pub fn recv_dgram<T>(self, buf: T) -> RecvDgram<T>
+        where T: AsMut<[u8]>,
+    {
+        RecvDgram(Some((self, buf)))
+    }
+
+    /// Gets the value of the `SO_BROADCAST` option for this socket.
+    ///
+    /// For more information about this option, see
+    /// [`set_broadcast`][link].
+    ///
+    /// [link]: #method.set_broadcast
+    pub fn broadcast(&self) -> io::Result<bool> {
+        self.io.get_ref().broadcast()
+    }
+
+    /// Sets the value of the `SO_BROADCAST` option for this socket.
+    ///
+    /// When enabled, this socket is allowed to send packets to a broadcast
+    /// address.
+    pub fn set_broadcast(&self, on: bool) -> io::Result<()> {
+        self.io.get_ref().set_broadcast(on)
+    }
+
+    /// Gets the value of the `IP_MULTICAST_LOOP` option for this socket.
+    ///
+    /// For more information about this option, see
+    /// [`set_multicast_loop_v4`][link].
+    ///
+    /// [link]: #method.set_multicast_loop_v4
+    pub fn multicast_loop_v4(&self) -> io::Result<bool> {
+        self.io.get_ref().multicast_loop_v4()
+    }
+
+    /// Sets the value of the `IP_MULTICAST_LOOP` option for this socket.
+    ///
+    /// If enabled, multicast packets will be looped back to the local socket.
+    /// Note that this may not have any affect on IPv6 sockets.
+    pub fn set_multicast_loop_v4(&self, on: bool) -> io::Result<()> {
+        self.io.get_ref().set_multicast_loop_v4(on)
+    }
+
+    /// Gets the value of the `IP_MULTICAST_TTL` option for this socket.
+    ///
+    /// For more information about this option, see
+    /// [`set_multicast_ttl_v4`][link].
+    ///
+    /// [link]: #method.set_multicast_ttl_v4
+    pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
+        self.io.get_ref().multicast_ttl_v4()
+    }
+
+    /// Sets the value of the `IP_MULTICAST_TTL` option for this socket.
+    ///
+    /// Indicates the time-to-live value of outgoing multicast packets for
+    /// this socket. The default value is 1 which means that multicast packets
+    /// don't leave the local network unless explicitly requested.
+    ///
+    /// Note that this may not have any affect on IPv6 sockets.
+    pub fn set_multicast_ttl_v4(&self, ttl: u32) -> io::Result<()> {
+        self.io.get_ref().set_multicast_ttl_v4(ttl)
+    }
+
+    /// Gets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
+    ///
+    /// For more information about this option, see
+    /// [`set_multicast_loop_v6`][link].
+    ///
+    /// [link]: #method.set_multicast_loop_v6
+    pub fn multicast_loop_v6(&self) -> io::Result<bool> {
+        self.io.get_ref().multicast_loop_v6()
+    }
+
+    /// Sets the value of the `IPV6_MULTICAST_LOOP` option for this socket.
+    ///
+    /// Controls whether this socket sees the multicast packets it sends itself.
+    /// Note that this may not have any affect on IPv4 sockets.
+    pub fn set_multicast_loop_v6(&self, on: bool) -> io::Result<()> {
+        self.io.get_ref().set_multicast_loop_v6(on)
+    }
+
+    /// Gets the value of the `IP_TTL` option for this socket.
+    ///
+    /// For more information about this option, see [`set_ttl`][link].
+    ///
+    /// [link]: #method.set_ttl
+    pub fn ttl(&self) -> io::Result<u32> {
+        self.io.get_ref().ttl()
+    }
+
+    /// Sets the value for the `IP_TTL` option on this socket.
+    ///
+    /// This value sets the time-to-live field that is used in every packet sent
+    /// from this socket.
+    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
+        self.io.get_ref().set_ttl(ttl)
+    }
+
+    /// Executes an operation of the `IP_ADD_MEMBERSHIP` type.
+    ///
+    /// This function specifies a new multicast group for this socket to join.
+    /// The address must be a valid multicast address, and `interface` is the
+    /// address of the local interface with which the system should join the
+    /// multicast group. If it's equal to `INADDR_ANY` then an appropriate
+    /// interface is chosen by the system.
+    pub fn join_multicast_v4(&self,
+                             multiaddr: &Ipv4Addr,
+                             interface: &Ipv4Addr) -> io::Result<()> {
+        self.io.get_ref().join_multicast_v4(multiaddr, interface)
+    }
+
+    /// Executes an operation of the `IPV6_ADD_MEMBERSHIP` type.
+    ///
+    /// This function specifies a new multicast group for this socket to join.
+    /// The address must be a valid multicast address, and `interface` is the
+    /// index of the interface to join/leave (or 0 to indicate any interface).
+    pub fn join_multicast_v6(&self,
+                             multiaddr: &Ipv6Addr,
+                             interface: u32) -> io::Result<()> {
+        self.io.get_ref().join_multicast_v6(multiaddr, interface)
+    }
+
+    /// Executes an operation of the `IP_DROP_MEMBERSHIP` type.
+    ///
+    /// For more information about this option, see
+    /// [`join_multicast_v4`][link].
+    ///
+    /// [link]: #method.join_multicast_v4
+    pub fn leave_multicast_v4(&self,
+                              multiaddr: &Ipv4Addr,
+                              interface: &Ipv4Addr) -> io::Result<()> {
+        self.io.get_ref().leave_multicast_v4(multiaddr, interface)
+    }
+
+    /// Executes an operation of the `IPV6_DROP_MEMBERSHIP` type.
+    ///
+    /// For more information about this option, see
+    /// [`join_multicast_v6`][link].
+    ///
+    /// [link]: #method.join_multicast_v6
+    pub fn leave_multicast_v6(&self,
+                              multiaddr: &Ipv6Addr,
+                              interface: u32) -> io::Result<()> {
+        self.io.get_ref().leave_multicast_v6(multiaddr, interface)
+    }
+
+    /// Sets the value for the `IPV6_V6ONLY` option on this socket.
+    ///
+    /// If this is set to `true` then the socket is restricted to sending and
+    /// receiving IPv6 packets only. In this case two IPv4 and IPv6 applications
+    /// can bind the same port at the same time.
+    ///
+    /// If this is set to `false` then the socket can be used to send and
+    /// receive packets from an IPv4-mapped IPv6 address.
+    pub fn set_only_v6(&self, only_v6: bool) -> io::Result<()> {
+        self.io.get_ref().set_only_v6(only_v6)
+    }
+
+    /// Gets the value of the `IPV6_V6ONLY` option for this socket.
+    ///
+    /// For more information about this option, see [`set_only_v6`][link].
+    ///
+    /// [link]: #method.set_only_v6
+    pub fn only_v6(&self) -> io::Result<bool> {
+        self.io.get_ref().only_v6()
+    }
+}
+
+impl fmt::Debug for UdpSocket {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.io.get_ref().fmt(f)
+    }
+}
+
+/// A future used to write the entire contents of some data to a UDP socket.
+///
+/// This is created by the `UdpSocket::send_dgram` method.
+#[must_use = "futures do nothing unless polled"]
+pub struct SendDgram<T>(Option<(UdpSocket, T, SocketAddr)>);
+
+fn incomplete_write(reason: &str) -> io::Error {
+    io::Error::new(io::ErrorKind::Other, reason)
+}
+
+impl<T> Future for SendDgram<T>
+    where T: AsRef<[u8]>,
+{
+    type Item = (UdpSocket, T);
+    type Error = io::Error;
+
+    fn poll(&mut self) -> Poll<(UdpSocket, T), io::Error> {
+        {
+            let (ref sock, ref buf, ref addr) =
+                *self.0.as_ref().expect("SendDgram polled after completion");
+            let n = try_nb!(sock.send_to(buf.as_ref(), addr));
+            if n != buf.as_ref().len() {
+                return Err(incomplete_write("failed to send entire message \
+                                             in datagram"))
+            }
+        }
+
+        let (sock, buf, _addr) = self.0.take().unwrap();
+        Ok(Async::Ready((sock, buf)))
+    }
+}
+
+/// A future used to receive a datagram from a UDP socket.
+///
+/// This is created by the `UdpSocket::recv_dgram` method.
+#[must_use = "futures do nothing unless polled"]
+pub struct RecvDgram<T>(Option<(UdpSocket, T)>);
+
+impl<T> Future for RecvDgram<T>
+    where T: AsMut<[u8]>,
+{
+    type Item = (UdpSocket, T, usize, SocketAddr);
+    type Error = io::Error;
+
+    fn poll(&mut self) -> Poll<Self::Item, io::Error> {
+        let (n, addr) = {
+            let (ref socket, ref mut buf) =
+                *self.0.as_mut().expect("RecvDgram polled after completion");
+
+            try_nb!(socket.recv_from(buf.as_mut()))
+        };
+
+        let (socket, buf) = self.0.take().unwrap();
+        Ok(Async::Ready((socket, buf, n, addr)))
+    }
+}
+
+#[cfg(all(unix, not(target_os = "fuchsia")))]
+mod sys {
+    use std::os::unix::prelude::*;
+    use super::UdpSocket;
+
+    impl AsRawFd for UdpSocket {
+        fn as_raw_fd(&self) -> RawFd {
+            self.io.get_ref().as_raw_fd()
+        }
+    }
+}
+
+#[cfg(windows)]
+mod sys {
+    // TODO: let's land these upstream with mio and then we can add them here.
+    //
+    // use std::os::windows::prelude::*;
+    // use super::UdpSocket;
+    //
+    // impl AsRawHandle for UdpSocket {
+    //     fn as_raw_handle(&self) -> RawHandle {
+    //         self.io.get_ref().as_raw_handle()
+    //     }
+    // }
+}
\ No newline at end of file