std: Add a net module for TCP/UDP

This commit is an implementation of [RFC 807][rfc] which adds a `std::net`
module for basic neworking based on top of `std::io`. This module serves as a
replacement for the `std::old_io::net` module and networking primitives in
`old_io`.

[rfc]: fillmein

The major focus of this redesign is to cut back on the level of abstraction to
the point that each of the networking types is just a bare socket. To this end
functionality such as timeouts and cloning has been removed (although cloning
can be done through `duplicate`, it may just yield an error).

With this `net` module comes a new implementation of `SocketAddr` and `IpAddr`.
This work is entirely based on rust-lang#20785 and the only changes were to alter the
in-memory representation to match the `libc`-expected variants and to move from
public fields to accessors.

Author: alexcrichton

src/libstd/lib.rs

@@ -250,6 +250,7 @@ pub mod ffi;
 pub mod old_io;
 pub mod io;
 pub mod fs;
+pub mod net;
 pub mod os;
 pub mod env;
 pub mod path;

src/libstd/net/addr.rs

@@ -0,0 +1,99 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Networking primitives for TCP/UDP communication
+//!
+//! > **NOTE**: This module is very much a work in progress and is under active
+//! > development. At this time it is still recommended to use the `old_io`
+//! > module while the details of this module shake out.
+
+#![unstable(feature = "net")]
+
+use prelude::v1::*;
+
+use io::{self, Error, ErrorKind};
+use num::Int;
+use sys_common::net2 as net_imp;
+
+pub use self::ip::{IpAddr, Ipv4Addr, Ipv6Addr, Ipv6MulticastScope};
+pub use self::addr::{SocketAddr, ToSocketAddrs};
+pub use self::tcp::{TcpStream, TcpListener};
+pub use self::udp::UdpSocket;
+
+mod ip;
+mod addr;
+mod tcp;
+mod udp;
+mod parser;
+#[cfg(test)] mod test;
+
+/// Possible values which can be passed to the `shutdown` method of `TcpStream`
+/// and `UdpSocket`.
+#[derive(Copy, Clone, PartialEq)]
+pub enum Shutdown {
+    /// Indicates that the reading portion of this stream/socket should be shut
+    /// down. All currently blocked and future reads will return `Ok(0)`.
+    Read,
+    /// Indicates that the writing portion of this stream/socket should be shut
+    /// down. All currently blocked and future writes will return an error.
+    Write,
+    /// Shut down both the reading and writing portions of this stream.
+    ///
+    /// See `Shutdown::Read` and `Shutdown::Write` for more information.
+    Both
+}
+
+fn hton<I: Int>(i: I) -> I { i.to_be() }
+fn ntoh<I: Int>(i: I) -> I { Int::from_be(i) }
+
+fn each_addr<A: ToSocketAddrs + ?Sized, F, T>(addr: &A, mut f: F) -> io::Result<T>
+    where F: FnMut(&SocketAddr) -> io::Result<T>
+{
+    let mut last_err = None;
+    for addr in try!(addr.to_socket_addrs()) {
+        match f(&addr) {
+            Ok(l) => return Ok(l),
+            Err(e) => last_err = Some(e),
+        }
+    }
+    Err(last_err.unwrap_or_else(|| {
+        Error::new(ErrorKind::InvalidInput,
+                   "could not resolve to any addresses", None)
+    }))
+}
+
+/// An iterator over `SocketAddr` values returned from a host lookup operation.
+pub struct LookupHost(net_imp::LookupHost);
+
+impl Iterator for LookupHost {
+    type Item = io::Result<SocketAddr>;
+    fn next(&mut self) -> Option<io::Result<SocketAddr>> { self.0.next() }
+}
+
+/// Resolve the host specified by `host` as a number of `SocketAddr` instances.
+///
+/// This method may perform a DNS query to resolve `host` and may also inspect
+/// system configuration to resolve the specified hostname.
+///
+/// # Example
+///
+/// ```no_run
+/// use std::net;
+///
+/// # fn foo() -> std::io::Result<()> {
+/// for host in try!(net::lookup_host("rust-lang.org")) {
+///     println!("found address: {}", try!(host));
+/// }
+/// # Ok(())
+/// # }
+/// ```
+pub fn lookup_host(host: &str) -> io::Result<LookupHost> {
+    net_imp::lookup_host(host).map(LookupHost)
+}

src/libstd/net/ip.rs

@@ -0,0 +1,330 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A private parser implementation of IPv4, IPv6, and socket addresses.
+//!
+//! This module is "publicly exported" through the `FromStr` implementations
+//! below.
+
+use prelude::v1::*;
+
+use str::FromStr;
+use net::{Ipv4Addr, Ipv6Addr, IpAddr, SocketAddr};
+
+struct Parser<'a> {
+    // parsing as ASCII, so can use byte array
+    s: &'a [u8],
+    pos: usize,
+}
+
+impl<'a> Parser<'a> {
+    fn new(s: &'a str) -> Parser<'a> {
+        Parser {
+            s: s.as_bytes(),
+            pos: 0,
+        }
+    }
+
+    fn is_eof(&self) -> bool {
+        self.pos == self.s.len()
+    }
+
+    // Commit only if parser returns Some
+    fn read_atomically<T, F>(&mut self, cb: F) -> Option<T> where
+        F: FnOnce(&mut Parser) -> Option<T>,
+    {
+        let pos = self.pos;
+        let r = cb(self);
+        if r.is_none() {
+            self.pos = pos;
+        }
+        r
+    }
+
+    // Commit only if parser read till EOF
+    fn read_till_eof<T, F>(&mut self, cb: F) -> Option<T> where
+        F: FnOnce(&mut Parser) -> Option<T>,
+    {
+        self.read_atomically(move |p| {
+            match cb(p) {
+                Some(x) => if p.is_eof() {Some(x)} else {None},
+                None => None,
+            }
+        })
+    }
+
+    // Return result of first successful parser
+    fn read_or<T>(&mut self, parsers: &mut [Box<FnMut(&mut Parser) -> Option<T>>])
+               -> Option<T> {
+        for pf in parsers.iter_mut() {
+            match self.read_atomically(|p: &mut Parser| pf(p)) {
+                Some(r) => return Some(r),
+                None => {}
+            }
+        }
+        None
+    }
+
+    // Apply 3 parsers sequentially
+    fn read_seq_3<A, B, C, PA, PB, PC>(&mut self,
+                                       pa: PA,
+                                       pb: PB,
+                                       pc: PC)
+                                       -> Option<(A, B, C)> where
+        PA: FnOnce(&mut Parser) -> Option<A>,
+        PB: FnOnce(&mut Parser) -> Option<B>,
+        PC: FnOnce(&mut Parser) -> Option<C>,
+    {
+        self.read_atomically(move |p| {
+            let a = pa(p);
+            let b = if a.is_some() { pb(p) } else { None };
+            let c = if b.is_some() { pc(p) } else { None };
+            match (a, b, c) {
+                (Some(a), Some(b), Some(c)) => Some((a, b, c)),
+                _ => None
+            }
+        })
+    }
+
+    // Read next char
+    fn read_char(&mut self) -> Option<char> {
+        if self.is_eof() {
+            None
+        } else {
+            let r = self.s[self.pos] as char;
+            self.pos += 1;
+            Some(r)
+        }
+    }
+
+    // Return char and advance iff next char is equal to requested
+    fn read_given_char(&mut self, c: char) -> Option<char> {
+        self.read_atomically(|p| {
+            match p.read_char() {
+                Some(next) if next == c => Some(next),
+                _ => None,
+            }
+        })
+    }
+
+    // Read digit
+    fn read_digit(&mut self, radix: u8) -> Option<u8> {
+        fn parse_digit(c: char, radix: u8) -> Option<u8> {
+            let c = c as u8;
+            // assuming radix is either 10 or 16
+            if c >= b'0' && c <= b'9' {
+                Some(c - b'0')
+            } else if radix > 10 && c >= b'a' && c < b'a' + (radix - 10) {
+                Some(c - b'a' + 10)
+            } else if radix > 10 && c >= b'A' && c < b'A' + (radix - 10) {
+                Some(c - b'A' + 10)
+            } else {
+                None
+            }
+        }
+
+        self.read_atomically(|p| {
+            p.read_char().and_then(|c| parse_digit(c, radix))
+        })
+    }
+
+    fn read_number_impl(&mut self, radix: u8, max_digits: u32, upto: u32) -> Option<u32> {
+        let mut r = 0u32;
+        let mut digit_count = 0;
+        loop {
+            match self.read_digit(radix) {
+                Some(d) => {
+                    r = r * (radix as u32) + (d as u32);
+                    digit_count += 1;
+                    if digit_count > max_digits || r >= upto {
+                        return None
+                    }
+                }
+                None => {
+                    if digit_count == 0 {
+                        return None
+                    } else {
+                        return Some(r)
+                    }
+                }
+            };
+        }
+    }
+
+    // Read number, failing if max_digits of number value exceeded
+    fn read_number(&mut self, radix: u8, max_digits: u32, upto: u32) -> Option<u32> {
+        self.read_atomically(|p| p.read_number_impl(radix, max_digits, upto))
+    }
+
+    fn read_ipv4_addr_impl(&mut self) -> Option<Ipv4Addr> {
+        let mut bs = [0u8; 4];
+        let mut i = 0;
+        while i < 4 {
+            if i != 0 && self.read_given_char('.').is_none() {
+                return None;
+            }
+
+            let octet = self.read_number(10, 3, 0x100).map(|n| n as u8);
+            match octet {
+                Some(d) => bs[i] = d,
+                None => return None,
+            };
+            i += 1;
+        }
+        Some(Ipv4Addr::new(bs[0], bs[1], bs[2], bs[3]))
+    }
+
+    // Read IPv4 address
+    fn read_ipv4_addr(&mut self) -> Option<Ipv4Addr> {
+        self.read_atomically(|p| p.read_ipv4_addr_impl())
+    }
+
+    fn read_ipv6_addr_impl(&mut self) -> Option<Ipv6Addr> {
+        fn ipv6_addr_from_head_tail(head: &[u16], tail: &[u16]) -> Ipv6Addr {
+            assert!(head.len() + tail.len() <= 8);
+            let mut gs = [0u16; 8];
+            gs.clone_from_slice(head);
+            gs[(8 - tail.len()) .. 8].clone_from_slice(tail);
+            Ipv6Addr::new(gs[0], gs[1], gs[2], gs[3], gs[4], gs[5], gs[6], gs[7])
+        }
+
+        fn read_groups(p: &mut Parser, groups: &mut [u16; 8], limit: usize)
+                       -> (usize, bool) {
+            let mut i = 0;
+            while i < limit {
+                if i < limit - 1 {
+                    let ipv4 = p.read_atomically(|p| {
+                        if i == 0 || p.read_given_char(':').is_some() {
+                            p.read_ipv4_addr()
+                        } else {
+                            None
+                        }
+                    });
+                    if let Some(v4_addr) = ipv4 {
+                        let octets = v4_addr.octets();
+                        groups[i + 0] = ((octets[0] as u16) << 8) | (octets[1] as u16);
+                        groups[i + 1] = ((octets[2] as u16) << 8) | (octets[3] as u16);
+                        return (i + 2, true);
+                    }
+                }
+
+                let group = p.read_atomically(|p| {
+                    if i == 0 || p.read_given_char(':').is_some() {
+                        p.read_number(16, 4, 0x10000).map(|n| n as u16)
+                    } else {
+                        None
+                    }
+                });
+                match group {
+                    Some(g) => groups[i] = g,
+                    None => return (i, false)
+                }
+                i += 1;
+            }
+            (i, false)
+        }
+
+        let mut head = [0u16; 8];
+        let (head_size, head_ipv4) = read_groups(self, &mut head, 8);
+
+        if head_size == 8 {
+            return Some(Ipv6Addr::new(
+                head[0], head[1], head[2], head[3],
+                head[4], head[5], head[6], head[7]))
+        }
+
+        // IPv4 part is not allowed before `::`
+        if head_ipv4 {
+            return None
+        }
+
+        // read `::` if previous code parsed less than 8 groups
+        if !self.read_given_char(':').is_some() || !self.read_given_char(':').is_some() {
+            return None;
+        }
+
+        let mut tail = [0u16; 8];
+        let (tail_size, _) = read_groups(self, &mut tail, 8 - head_size);
+        Some(ipv6_addr_from_head_tail(&head[..head_size], &tail[..tail_size]))
+    }
+
+    fn read_ipv6_addr(&mut self) -> Option<Ipv6Addr> {
+        self.read_atomically(|p| p.read_ipv6_addr_impl())
+    }
+
+    fn read_ip_addr(&mut self) -> Option<IpAddr> {
+        let ipv4_addr = |p: &mut Parser| p.read_ipv4_addr().map(|v4| IpAddr::V4(v4));
+        let ipv6_addr = |p: &mut Parser| p.read_ipv6_addr().map(|v6| IpAddr::V6(v6));
+        self.read_or(&mut [Box::new(ipv4_addr), Box::new(ipv6_addr)])
+    }
+
+    fn read_socket_addr(&mut self) -> Option<SocketAddr> {
+        let ip_addr = |p: &mut Parser| {
+            let ipv4_p = |p: &mut Parser| p.read_ip_addr();
+            let ipv6_p = |p: &mut Parser| {
+                let open_br = |p: &mut Parser| p.read_given_char('[');
+                let ip_addr = |p: &mut Parser| p.read_ipv6_addr();
+                let clos_br = |p: &mut Parser| p.read_given_char(']');
+                p.read_seq_3::<char, Ipv6Addr, char, _, _, _>(open_br, ip_addr, clos_br)
+                        .map(|t| match t { (_, ip, _) => IpAddr::V6(ip) })
+            };
+            p.read_or(&mut [Box::new(ipv4_p), Box::new(ipv6_p)])
+        };
+        let colon = |p: &mut Parser| p.read_given_char(':');
+        let port  = |p: &mut Parser| p.read_number(10, 5, 0x10000).map(|n| n as u16);
+
+        // host, colon, port
+        self.read_seq_3::<IpAddr, char, u16, _, _, _>(ip_addr, colon, port)
+                .map(|t| match t { (ip, _, port) => SocketAddr::new(ip, port) })
+    }
+}
+
+impl FromStr for IpAddr {
+    type Err = ParseError;
+    fn from_str(s: &str) -> Result<IpAddr, ParseError> {
+        match Parser::new(s).read_till_eof(|p| p.read_ip_addr()) {
+            Some(s) => Ok(s),
+            None => Err(ParseError),
+        }
+    }
+}
+
+impl FromStr for Ipv4Addr {
+    type Err = ParseError;
+    fn from_str(s: &str) -> Result<Ipv4Addr, ParseError> {
+        match Parser::new(s).read_till_eof(|p| p.read_ipv4_addr()) {
+            Some(s) => Ok(s),
+            None => Err(ParseError)
+        }
+    }
+}
+
+impl FromStr for Ipv6Addr {
+    type Err = ParseError;
+    fn from_str(s: &str) -> Result<Ipv6Addr, ParseError> {
+        match Parser::new(s).read_till_eof(|p| p.read_ipv6_addr()) {
+            Some(s) => Ok(s),
+            None => Err(ParseError)
+        }
+    }
+}
+
+impl FromStr for SocketAddr {
+    type Err = ParseError;
+    fn from_str(s: &str) -> Result<SocketAddr, ParseError> {
+        match Parser::new(s).read_till_eof(|p| p.read_socket_addr()) {
+            Some(s) => Ok(s),
+            None => Err(ParseError),
+        }
+    }
+}
+
+#[derive(Debug, Clone, PartialEq, Copy)]
+pub struct ParseError;

src/libstd/net/mod.rs

@@ -0,0 +1,39 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use prelude::v1::*;
+
+use env;
+use net::{SocketAddr, IpAddr};
+use sync::atomic::{AtomicUsize, ATOMIC_USIZE_INIT, Ordering};
+
+pub fn next_test_ip4() -> SocketAddr {
+    static PORT: AtomicUsize = ATOMIC_USIZE_INIT;
+    SocketAddr::new(IpAddr::new_v4(127, 0, 0, 1),
+                    PORT.fetch_add(1, Ordering::SeqCst) as u16 + base_port())
+}
+
+pub fn next_test_ip6() -> SocketAddr {
+    static PORT: AtomicUsize = ATOMIC_USIZE_INIT;
+    SocketAddr::new(IpAddr::new_v6(0, 0, 0, 0, 0, 0, 0, 1),
+                    PORT.fetch_add(1, Ordering::SeqCst) as u16 + base_port())
+}
+
+// The bots run multiple builds at the same time, and these builds
+// all want to use ports. This function figures out which workspace
+// it is running in and assigns a port range based on it.
+fn base_port() -> u16 {
+    let cwd = env::current_dir().unwrap();
+    let dirs = ["32-opt", "32-nopt", "64-opt", "64-nopt", "64-opt-vg",
+                "all-opt", "snap3", "dist"];
+    dirs.iter().enumerate().find(|&(i, dir)| {
+        cwd.as_str().unwrap().contains(dir)
+    }).map(|p| p.0).unwrap_or(0) as u16 * 1000 + 19600
+}

src/libstd/net/parser.rs

@@ -0,0 +1,291 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use prelude::v1::*;
+
+use io::{self, Error, ErrorKind};
+use net::{ToSocketAddrs, SocketAddr, IpAddr};
+use sys_common::net2 as net_imp;
+use sys_common::AsInner;
+
+/// A User Datagram Protocol socket.
+///
+/// This is an implementation of a bound UDP socket. This supports both IPv4 and
+/// IPv6 addresses, and there is no corresponding notion of a server because UDP
+/// is a datagram protocol.
+///
+/// # Example
+///
+/// ```no_run
+/// use std::net::UdpSocket;
+///
+/// # fn foo() -> std::io::Result<()> {
+/// let mut socket = try!(UdpSocket::bind("127.0.0.1:34254"));
+///
+/// let mut buf = [0; 10];
+/// let (amt, src) = try!(socket.recv_from(&mut buf));
+///
+/// // Send a reply to the socket we received data from
+/// let buf = &mut buf[..amt];
+/// buf.reverse();
+/// try!(socket.send_to(buf, &src));
+///
+/// drop(socket); // close the socket
+/// # Ok(())
+/// # }
+/// ```
+pub struct UdpSocket(net_imp::UdpSocket);
+
+impl UdpSocket {
+    /// Creates a UDP socket from the given address.
+    ///
+    /// Address type can be any implementor of `ToSocketAddr` trait. See its
+    /// documentation for concrete examples.
+    pub fn bind<A: ToSocketAddrs + ?Sized>(addr: &A) -> io::Result<UdpSocket> {
+        super::each_addr(addr, net_imp::UdpSocket::bind).map(UdpSocket)
+    }
+
+    /// 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)> {
+        self.0.recv_from(buf)
+    }
+
+    /// Sends data on the socket to the given address. Returns nothing on
+    /// success.
+    ///
+    /// Address type can be any implementor of `ToSocketAddrs` trait. See its
+    /// documentation for concrete examples.
+    pub fn send_to<A: ToSocketAddrs + ?Sized>(&self, buf: &[u8], addr: &A)
+                                              -> io::Result<usize> {
+        match try!(addr.to_socket_addrs()).next() {
+            Some(addr) => self.0.send_to(buf, &addr),
+            None => Err(Error::new(ErrorKind::InvalidInput,
+                                   "no addresses to send data to", None)),
+        }
+    }
+
+    /// Returns the socket address that this socket was created from.
+    pub fn socket_addr(&self) -> io::Result<SocketAddr> {
+        self.0.socket_addr()
+    }
+
+    /// Create a new independently owned handle to the underlying socket.
+    ///
+    /// The returned `UdpSocket` is a reference to the same socket that this
+    /// object references. Both handles will read and write the same port, and
+    /// options set on one socket will be propagated to the other.
+    pub fn try_clone(&self) -> io::Result<UdpSocket> {
+        self.0.duplicate().map(UdpSocket)
+    }
+
+    /// Sets the broadcast flag on or off
+    pub fn set_broadcast(&self, on: bool) -> io::Result<()> {
+        self.0.set_broadcast(on)
+    }
+
+    /// Set the multicast loop flag to the specified value
+    ///
+    /// This lets multicast packets loop back to local sockets (if enabled)
+    pub fn set_multicast_loop(&self, on: bool) -> io::Result<()> {
+        self.0.set_multicast_loop(on)
+    }
+
+    /// Joins a multicast IP address (becomes a member of it)
+    pub fn join_multicast(&self, multi: &IpAddr) -> io::Result<()> {
+        self.0.join_multicast(multi)
+    }
+
+    /// Leaves a multicast IP address (drops membership from it)
+    pub fn leave_multicast(&self, multi: &IpAddr) -> io::Result<()> {
+        self.0.leave_multicast(multi)
+    }
+
+    /// Sets the multicast TTL
+    pub fn set_multicast_time_to_live(&self, ttl: i32) -> io::Result<()> {
+        self.0.multicast_time_to_live(ttl)
+    }
+
+    /// Sets this socket's TTL
+    pub fn set_time_to_live(&self, ttl: i32) -> io::Result<()> {
+        self.0.time_to_live(ttl)
+    }
+}
+
+impl AsInner<net_imp::UdpSocket> for UdpSocket {
+    fn as_inner(&self) -> &net_imp::UdpSocket { &self.0 }
+}
+
+#[cfg(test)]
+mod tests {
+    use prelude::v1::*;
+
+    use io::ErrorKind;
+    use net::*;
+    use net::test::{next_test_ip4, next_test_ip6};
+    use sync::mpsc::channel;
+    use thread::Thread;
+
+    fn each_ip(f: &mut FnMut(SocketAddr, SocketAddr)) {
+        f(next_test_ip4(), next_test_ip4());
+        f(next_test_ip6(), next_test_ip6());
+    }
+
+    macro_rules! t {
+        ($e:expr) => {
+            match $e {
+                Ok(t) => t,
+                Err(e) => panic!("received error for `{}`: {}", stringify!($e), e),
+            }
+        }
+    }
+
+    // FIXME #11530 this fails on android because tests are run as root
+    #[cfg_attr(any(windows, target_os = "android"), ignore)]
+    #[test]
+    fn bind_error() {
+        let addr = SocketAddr::new(IpAddr::new_v4(0, 0, 0, 0), 1);
+        match UdpSocket::bind(&addr) {
+            Ok(..) => panic!(),
+            Err(e) => assert_eq!(e.kind(), ErrorKind::PermissionDenied),
+        }
+    }
+
+    #[test]
+    fn socket_smoke_test_ip4() {
+        each_ip(&mut |server_ip, client_ip| {
+            let (tx1, rx1) = channel();
+            let (tx2, rx2) = channel();
+
+            let _t = Thread::spawn(move|| {
+                let client = t!(UdpSocket::bind(&client_ip));
+                rx1.recv().unwrap();
+                t!(client.send_to(&[99], &server_ip));
+                tx2.send(()).unwrap();
+            });
+
+            let server = t!(UdpSocket::bind(&server_ip));
+            tx1.send(()).unwrap();
+            let mut buf = [0];
+            let (nread, src) = t!(server.recv_from(&mut buf));
+            assert_eq!(nread, 1);
+            assert_eq!(buf[0], 99);
+            assert_eq!(src, client_ip);
+            rx2.recv().unwrap();
+        })
+    }
+
+    #[test]
+    fn socket_name_ip4() {
+        each_ip(&mut |addr, _| {
+            let server = t!(UdpSocket::bind(&addr));
+            assert_eq!(addr, t!(server.socket_addr()));
+        })
+    }
+
+    #[test]
+    fn udp_clone_smoke() {
+        each_ip(&mut |addr1, addr2| {
+            let sock1 = t!(UdpSocket::bind(&addr1));
+            let sock2 = t!(UdpSocket::bind(&addr2));
+
+            let _t = Thread::spawn(move|| {
+                let mut buf = [0, 0];
+                assert_eq!(sock2.recv_from(&mut buf), Ok((1, addr1)));
+                assert_eq!(buf[0], 1);
+                t!(sock2.send_to(&[2], &addr1));
+            });
+
+            let sock3 = t!(sock1.try_clone());
+
+            let (tx1, rx1) = channel();
+            let (tx2, rx2) = channel();
+            let _t = Thread::spawn(move|| {
+                rx1.recv().unwrap();
+                t!(sock3.send_to(&[1], &addr2));
+                tx2.send(()).unwrap();
+            });
+            tx1.send(()).unwrap();
+            let mut buf = [0, 0];
+            assert_eq!(sock1.recv_from(&mut buf), Ok((1, addr2)));
+            rx2.recv().unwrap();
+        })
+    }
+
+    #[test]
+    fn udp_clone_two_read() {
+        each_ip(&mut |addr1, addr2| {
+            let sock1 = t!(UdpSocket::bind(&addr1));
+            let sock2 = t!(UdpSocket::bind(&addr2));
+            let (tx1, rx) = channel();
+            let tx2 = tx1.clone();
+
+            let _t = Thread::spawn(move|| {
+                t!(sock2.send_to(&[1], &addr1));
+                rx.recv().unwrap();
+                t!(sock2.send_to(&[2], &addr1));
+                rx.recv().unwrap();
+            });
+
+            let sock3 = t!(sock1.try_clone());
+
+            let (done, rx) = channel();
+            let _t = Thread::spawn(move|| {
+                let mut buf = [0, 0];
+                t!(sock3.recv_from(&mut buf));
+                tx2.send(()).unwrap();
+                done.send(()).unwrap();
+            });
+            let mut buf = [0, 0];
+            t!(sock1.recv_from(&mut buf));
+            tx1.send(()).unwrap();
+
+            rx.recv().unwrap();
+        })
+    }
+
+    #[test]
+    fn udp_clone_two_write() {
+        each_ip(&mut |addr1, addr2| {
+            let sock1 = t!(UdpSocket::bind(&addr1));
+            let sock2 = t!(UdpSocket::bind(&addr2));
+
+            let (tx, rx) = channel();
+            let (serv_tx, serv_rx) = channel();
+
+            let _t = Thread::spawn(move|| {
+                let mut buf = [0, 1];
+                rx.recv().unwrap();
+                t!(sock2.recv_from(&mut buf));
+                serv_tx.send(()).unwrap();
+            });
+
+            let sock3 = t!(sock1.try_clone());
+
+            let (done, rx) = channel();
+            let tx2 = tx.clone();
+            let _t = Thread::spawn(move|| {
+                match sock3.send_to(&[1], &addr2) {
+                    Ok(..) => { let _ = tx2.send(()); }
+                    Err(..) => {}
+                }
+                done.send(()).unwrap();
+            });
+            match sock1.send_to(&[2], &addr2) {
+                Ok(..) => { let _ = tx.send(()); }
+                Err(..) => {}
+            }
+            drop(tx);
+
+            rx.recv().unwrap();
+            serv_rx.recv().unwrap();
+        })
+    }
+}

src/libstd/net/tcp.rs

@@ -24,6 +24,7 @@ pub mod condvar;
 pub mod helper_thread;
 pub mod mutex;
 pub mod net;
+pub mod net2;
 pub mod rwlock;
 pub mod stack;
 pub mod thread;

src/libstd/net/test.rs

@@ -0,0 +1,393 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use prelude::v1::*;
+
+use ffi::CString;
+use io::{self, Error, ErrorKind};
+use libc::{self, c_int, c_char, c_void, socklen_t};
+use mem;
+use net::{IpAddr, SocketAddr, Shutdown};
+use num::Int;
+use sys::c;
+use sys::net::{cvt, cvt_r, cvt_gai, Socket, init, wrlen_t};
+use sys_common::{AsInner, FromInner, IntoInner};
+
+////////////////////////////////////////////////////////////////////////////////
+// sockaddr and misc bindings
+////////////////////////////////////////////////////////////////////////////////
+
+fn hton<I: Int>(i: I) -> I { i.to_be() }
+fn ntoh<I: Int>(i: I) -> I { Int::from_be(i) }
+
+fn setsockopt<T>(sock: &Socket, opt: c_int, val: c_int,
+                     payload: T) -> io::Result<()> {
+    unsafe {
+        let payload = &payload as *const T as *const c_void;
+        try!(cvt(libc::setsockopt(*sock.as_inner(), opt, val, payload,
+                                  mem::size_of::<T>() as socklen_t)));
+        Ok(())
+    }
+}
+
+#[allow(dead_code)]
+fn getsockopt<T: Copy>(sock: &Socket, opt: c_int,
+                           val: c_int) -> io::Result<T> {
+    unsafe {
+        let mut slot: T = mem::zeroed();
+        let mut len = mem::size_of::<T>() as socklen_t;
+        let ret = try!(cvt(c::getsockopt(*sock.as_inner(), opt, val,
+                                         &mut slot as *mut _ as *mut _,
+                                         &mut len)));
+        assert_eq!(ret as usize, mem::size_of::<T>());
+        Ok(slot)
+    }
+}
+
+fn sockname<F>(f: F) -> io::Result<SocketAddr>
+    where F: FnOnce(*mut libc::sockaddr, *mut socklen_t) -> c_int
+{
+    unsafe {
+        let mut storage: libc::sockaddr_storage = mem::zeroed();
+        let mut len = mem::size_of_val(&storage) as socklen_t;
+        try!(cvt(f(&mut storage as *mut _ as *mut _, &mut len)));
+        sockaddr_to_addr(&storage, len as usize)
+    }
+}
+
+fn sockaddr_to_addr(storage: &libc::sockaddr_storage,
+                    len: usize) -> io::Result<SocketAddr> {
+    match storage.ss_family as libc::c_int {
+        libc::AF_INET => {
+            assert!(len as usize >= mem::size_of::<libc::sockaddr_in>());
+            Ok(FromInner::from_inner(unsafe {
+                *(storage as *const _ as *const libc::sockaddr_in)
+            }))
+        }
+        libc::AF_INET6 => {
+            assert!(len as usize >= mem::size_of::<libc::sockaddr_in6>());
+            Ok(FromInner::from_inner(unsafe {
+                *(storage as *const _ as *const libc::sockaddr_in6)
+            }))
+        }
+        _ => {
+            Err(Error::new(ErrorKind::InvalidInput, "invalid argument", None))
+        }
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// get_host_addresses
+////////////////////////////////////////////////////////////////////////////////
+
+extern "system" {
+    fn getaddrinfo(node: *const c_char, service: *const c_char,
+                   hints: *const libc::addrinfo,
+                   res: *mut *mut libc::addrinfo) -> c_int;
+    fn freeaddrinfo(res: *mut libc::addrinfo);
+}
+
+pub struct LookupHost {
+    original: *mut libc::addrinfo,
+    cur: *mut libc::addrinfo,
+}
+
+impl Iterator for LookupHost {
+    type Item = io::Result<SocketAddr>;
+    fn next(&mut self) -> Option<io::Result<SocketAddr>> {
+        unsafe {
+            if self.cur.is_null() { return None }
+            let ret = sockaddr_to_addr(mem::transmute((*self.cur).ai_addr),
+                                       (*self.cur).ai_addrlen as usize);
+            self.cur = (*self.cur).ai_next as *mut libc::addrinfo;
+            Some(ret)
+        }
+    }
+}
+
+impl Drop for LookupHost {
+    fn drop(&mut self) {
+        unsafe { freeaddrinfo(self.original) }
+    }
+}
+
+pub fn lookup_host(host: &str) -> io::Result<LookupHost> {
+    init();
+
+    let c_host = CString::from_slice(host.as_bytes());
+    let mut res = 0 as *mut _;
+    unsafe {
+        try!(cvt_gai(getaddrinfo(c_host.as_ptr(), 0 as *const _, 0 as *const _,
+                                 &mut res)));
+        Ok(LookupHost { original: res, cur: res })
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// TCP streams
+////////////////////////////////////////////////////////////////////////////////
+
+pub struct TcpStream {
+    inner: Socket,
+}
+
+impl TcpStream {
+    pub fn connect(addr: &SocketAddr) -> io::Result<TcpStream> {
+        init();
+
+        let sock = try!(Socket::new(addr, libc::SOCK_STREAM));
+
+        let (addrp, len) = addr.into_inner();
+        try!(cvt_r(|| unsafe { libc::connect(*sock.as_inner(), addrp, len) }));
+        Ok(TcpStream { inner: sock })
+    }
+
+    pub fn socket(&self) -> &Socket { &self.inner }
+
+    pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
+        setsockopt(&self.inner, libc::IPPROTO_TCP, libc::TCP_NODELAY,
+                   nodelay as c_int)
+    }
+
+    pub fn set_keepalive(&self, seconds: Option<u32>) -> io::Result<()> {
+        let ret = setsockopt(&self.inner, libc::SOL_SOCKET, libc::SO_KEEPALIVE,
+                             seconds.is_some() as c_int);
+        match seconds {
+            Some(n) => ret.and_then(|()| self.set_tcp_keepalive(n)),
+            None => ret,
+        }
+    }
+
+    #[cfg(any(target_os = "macos", target_os = "ios"))]
+    fn set_tcp_keepalive(&self, seconds: u32) -> io::Result<()> {
+        setsockopt(&self.inner, libc::IPPROTO_TCP, libc::TCP_KEEPALIVE,
+                   seconds as c_int)
+    }
+    #[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+    fn set_tcp_keepalive(&self, seconds: u32) -> io::Result<()> {
+        setsockopt(&self.inner, libc::IPPROTO_TCP, libc::TCP_KEEPIDLE,
+                   seconds as c_int)
+    }
+    #[cfg(not(any(target_os = "macos",
+                  target_os = "ios",
+                  target_os = "freebsd",
+                  target_os = "dragonfly")))]
+    fn set_tcp_keepalive(&self, _seconds: u32) -> io::Result<()> {
+        Ok(())
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+
+    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
+        let ret = try!(cvt(unsafe {
+            libc::send(*self.inner.as_inner(),
+                       buf.as_ptr() as *const c_void,
+                       buf.len() as wrlen_t,
+                       0)
+        }));
+        Ok(ret as usize)
+    }
+
+    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            libc::getpeername(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn socket_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            libc::getsockname(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
+        use libc::consts::os::bsd44::SHUT_RDWR;
+
+        let how = match how {
+            Shutdown::Write => libc::SHUT_WR,
+            Shutdown::Read => libc::SHUT_RD,
+            Shutdown::Both => SHUT_RDWR,
+        };
+        try!(cvt(unsafe { libc::shutdown(*self.inner.as_inner(), how) }));
+        Ok(())
+    }
+
+    pub fn duplicate(&self) -> io::Result<TcpStream> {
+        self.inner.duplicate().map(|s| TcpStream { inner: s })
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// TCP listeners
+////////////////////////////////////////////////////////////////////////////////
+
+pub struct TcpListener {
+    inner: Socket,
+}
+
+impl TcpListener {
+    pub fn bind(addr: &SocketAddr) -> io::Result<TcpListener> {
+        init();
+
+        let sock = try!(Socket::new(addr, libc::SOCK_STREAM));
+
+        // On platforms with Berkeley-derived sockets, this allows
+        // to quickly rebind a socket, without needing to wait for
+        // the OS to clean up the previous one.
+        if !cfg!(windows) {
+            try!(setsockopt(&sock, libc::SOL_SOCKET, libc::SO_REUSEADDR,
+                            1 as c_int));
+        }
+
+        // Bind our new socket
+        let (addrp, len) = addr.into_inner();
+        try!(cvt(unsafe { libc::bind(*sock.as_inner(), addrp, len) }));
+
+        // Start listening
+        try!(cvt(unsafe { libc::listen(*sock.as_inner(), 128) }));
+        Ok(TcpListener { inner: sock })
+    }
+
+    pub fn socket(&self) -> &Socket { &self.inner }
+
+    pub fn socket_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            libc::getsockname(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn accept(&self) -> io::Result<(TcpStream, SocketAddr)> {
+        let mut storage: libc::sockaddr_storage = unsafe { mem::zeroed() };
+        let mut len = mem::size_of_val(&storage) as socklen_t;
+        let sock = try!(self.inner.accept(&mut storage as *mut _ as *mut _,
+                                          &mut len));
+        let addr = try!(sockaddr_to_addr(&storage, len as usize));
+        Ok((TcpStream { inner: sock, }, addr))
+    }
+
+    pub fn duplicate(&self) -> io::Result<TcpListener> {
+        self.inner.duplicate().map(|s| TcpListener { inner: s })
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// UDP
+////////////////////////////////////////////////////////////////////////////////
+
+pub struct UdpSocket {
+    inner: Socket,
+}
+
+impl UdpSocket {
+    pub fn bind(addr: &SocketAddr) -> io::Result<UdpSocket> {
+        init();
+
+        let sock = try!(Socket::new(addr, libc::SOCK_DGRAM));
+        let (addrp, len) = addr.into_inner();
+        try!(cvt(unsafe { libc::bind(*sock.as_inner(), addrp, len) }));
+        Ok(UdpSocket { inner: sock })
+    }
+
+    pub fn socket(&self) -> &Socket { &self.inner }
+
+    pub fn socket_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            libc::getsockname(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
+        let mut storage: libc::sockaddr_storage = unsafe { mem::zeroed() };
+        let mut addrlen = mem::size_of_val(&storage) as socklen_t;
+
+        let n = try!(cvt(unsafe {
+            libc::recvfrom(*self.inner.as_inner(),
+                           buf.as_mut_ptr() as *mut c_void,
+                           buf.len() as wrlen_t, 0,
+                           &mut storage as *mut _ as *mut _, &mut addrlen)
+        }));
+        Ok((n as usize, try!(sockaddr_to_addr(&storage, addrlen as usize))))
+    }
+
+    pub fn send_to(&self, buf: &[u8], dst: &SocketAddr) -> io::Result<usize> {
+        let (dstp, dstlen) = dst.into_inner();
+        let ret = try!(cvt(unsafe {
+            libc::sendto(*self.inner.as_inner(),
+                         buf.as_ptr() as *const c_void, buf.len() as wrlen_t,
+                         0, dstp, dstlen)
+        }));
+        Ok(ret as usize)
+    }
+
+    pub fn set_broadcast(&self, on: bool) -> io::Result<()> {
+        setsockopt(&self.inner, libc::SOL_SOCKET, libc::SO_BROADCAST,
+                   on as c_int)
+    }
+
+    pub fn set_multicast_loop(&self, on: bool) -> io::Result<()> {
+        setsockopt(&self.inner, libc::IPPROTO_IP,
+                   libc::IP_MULTICAST_LOOP, on as c_int)
+    }
+
+    pub fn join_multicast(&self, multi: &IpAddr) -> io::Result<()> {
+        match *multi {
+            IpAddr::V4(..) => {
+                self.set_membership(multi, libc::IP_ADD_MEMBERSHIP)
+            }
+            IpAddr::V6(..) => {
+                self.set_membership(multi, libc::IPV6_ADD_MEMBERSHIP)
+            }
+        }
+    }
+    pub fn leave_multicast(&self, multi: &IpAddr) -> io::Result<()> {
+        match *multi {
+            IpAddr::V4(..) => {
+                self.set_membership(multi, libc::IP_DROP_MEMBERSHIP)
+            }
+            IpAddr::V6(..) => {
+                self.set_membership(multi, libc::IPV6_DROP_MEMBERSHIP)
+            }
+        }
+    }
+    fn set_membership(&self, addr: &IpAddr, opt: c_int) -> io::Result<()> {
+        match *addr {
+            IpAddr::V4(ref addr) => {
+                let mreq = libc::ip_mreq {
+                    imr_multiaddr: *addr.as_inner(),
+                    // interface == INADDR_ANY
+                    imr_interface: libc::in_addr { s_addr: 0x0 },
+                };
+                setsockopt(&self.inner, libc::IPPROTO_IP, opt, mreq)
+            }
+            IpAddr::V6(ref addr) => {
+                let mreq = libc::ip6_mreq {
+                    ipv6mr_multiaddr: *addr.as_inner(),
+                    ipv6mr_interface: 0,
+                };
+                setsockopt(&self.inner, libc::IPPROTO_IPV6, opt, mreq)
+            }
+        }
+    }
+
+    pub fn multicast_time_to_live(&self, ttl: i32) -> io::Result<()> {
+        setsockopt(&self.inner, libc::IPPROTO_IP, libc::IP_MULTICAST_TTL,
+                   ttl as c_int)
+    }
+
+    pub fn time_to_live(&self, ttl: i32) -> io::Result<()> {
+        setsockopt(&self.inner, libc::IPPROTO_IP, libc::IP_TTL, ttl as c_int)
+    }
+
+    pub fn duplicate(&self) -> io::Result<UdpSocket> {
+        self.inner.duplicate().map(|s| UdpSocket { inner: s })
+    }
+}

src/libstd/net/udp.rs

@@ -157,6 +157,7 @@ extern {
 
     pub fn utimes(filename: *const libc::c_char,
                   times: *const libc::timeval) -> libc::c_int;
+    pub fn gai_strerror(errcode: libc::c_int) -> *const libc::c_char;
 }
 
 #[cfg(any(target_os = "macos", target_os = "ios"))]

src/libstd/sys/common/mod.rs

@@ -32,8 +32,8 @@
 #![unstable(feature = "std_misc")]
 
 use ffi::{OsStr, OsString};
-use fs::{Permissions, OpenOptions};
-use fs;
+use fs::{self, Permissions, OpenOptions};
+use net;
 use libc;
 use mem;
 use sys::os_str::Buf;
@@ -111,6 +111,16 @@ impl AsRawFd for old_io::net::udp::UdpSocket {
     }
 }
 
+impl AsRawFd for net::TcpStream {
+    fn as_raw_fd(&self) -> Fd { *self.as_inner().socket().as_inner() }
+}
+impl AsRawFd for net::TcpListener {
+    fn as_raw_fd(&self) -> Fd { *self.as_inner().socket().as_inner() }
+}
+impl AsRawFd for net::UdpSocket {
+    fn as_raw_fd(&self) -> Fd { *self.as_inner().socket().as_inner() }
+}
+
 // Unix-specific extensions to `OsString`.
 pub trait OsStringExt {
     /// Create an `OsString` from a byte vector.

src/libstd/sys/common/net2.rs

@@ -15,8 +15,7 @@ use io;
 use libc::{self, c_int, size_t, c_void};
 use mem;
 use sys::cvt;
-
-pub type fd_t = c_int;
+use sys_common::AsInner;
 
 pub struct FileDesc {
     fd: c_int,
@@ -55,6 +54,10 @@ impl FileDesc {
     }
 }
 
+impl AsInner<c_int> for FileDesc {
+    fn as_inner(&self) -> &c_int { &self.fd }
+}
+
 impl Drop for FileDesc {
     fn drop(&mut self) {
         // closing stdio file handles makes no sense, so never do it. Also, note

src/libstd/sys/unix/c.rs

@@ -18,12 +18,11 @@
 use prelude::v1::*;
 
 use ffi;
-use io::ErrorKind;
+use io::{self, ErrorKind};
 use libc;
 use num::{Int, SignedInt};
 use num;
 use old_io::{self, IoResult, IoError};
-use io;
 use str;
 use sys_common::mkerr_libc;
 
@@ -47,6 +46,7 @@ pub mod fs;  // support for std::old_io
 pub mod fs2; // support for std::fs
 pub mod helper_signal;
 pub mod mutex;
+pub mod net;
 pub mod os;
 pub mod os_str;
 pub mod pipe;

src/libstd/sys/unix/ext.rs

@@ -0,0 +1,74 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use prelude::v1::*;
+
+use ffi;
+use io;
+use libc::{self, c_int, size_t};
+use str;
+use sys::c;
+use net::{SocketAddr, IpAddr};
+use sys::fd::FileDesc;
+use sys_common::AsInner;
+
+pub use sys::{cvt, cvt_r};
+
+pub type wrlen_t = size_t;
+
+pub struct Socket(FileDesc);
+
+pub fn init() {}
+
+pub fn cvt_gai(err: c_int) -> io::Result<()> {
+    if err == 0 { return Ok(()) }
+
+    let detail = unsafe {
+        str::from_utf8(ffi::c_str_to_bytes(&c::gai_strerror(err))).unwrap()
+            .to_string()
+    };
+    Err(io::Error::new(io::ErrorKind::Other,
+                       "failed to lookup address information", Some(detail)))
+}
+
+impl Socket {
+    pub fn new(addr: &SocketAddr, ty: c_int) -> io::Result<Socket> {
+        let fam = match addr.ip() {
+            IpAddr::V4(..) => libc::AF_INET,
+            IpAddr::V6(..) => libc::AF_INET6,
+        };
+        unsafe {
+            let fd = try!(cvt(libc::socket(fam, ty, 0)));
+            Ok(Socket(FileDesc::new(fd)))
+        }
+    }
+
+    pub fn accept(&self, storage: *mut libc::sockaddr,
+                  len: *mut libc::socklen_t) -> io::Result<Socket> {
+        let fd = try!(cvt_r(|| unsafe {
+            libc::accept(self.0.raw(), storage, len)
+        }));
+        Ok(Socket(FileDesc::new(fd)))
+    }
+
+    pub fn duplicate(&self) -> io::Result<Socket> {
+        cvt(unsafe { libc::dup(self.0.raw()) }).map(|fd| {
+            Socket(FileDesc::new(fd))
+        })
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.0.read(buf)
+    }
+}
+
+impl AsInner<c_int> for Socket {
+    fn as_inner(&self) -> &c_int { self.0.as_inner() }
+}

src/libstd/sys/unix/fd.rs

@@ -21,6 +21,7 @@ pub use sys_common::wtf8::{Wtf8Buf, EncodeWide};
 use ffi::{OsStr, OsString};
 use fs::{self, OpenOptions};
 use libc;
+use net;
 use sys::os_str::Buf;
 use sys_common::{AsInner, FromInner, AsInnerMut};
 
@@ -103,6 +104,16 @@ impl AsRawSocket for old_io::net::udp::UdpSocket {
     }
 }
 
+impl AsRawSocket for net::TcpStream {
+    fn as_raw_socket(&self) -> Socket { *self.as_inner().socket().as_inner() }
+}
+impl AsRawSocket for net::TcpListener {
+    fn as_raw_socket(&self) -> Socket { *self.as_inner().socket().as_inner() }
+}
+impl AsRawSocket for net::UdpSocket {
+    fn as_raw_socket(&self) -> Socket { *self.as_inner().socket().as_inner() }
+}
+
 // Windows-specific extensions to `OsString`.
 pub trait OsStringExt {
     /// Create an `OsString` from a potentially ill-formed UTF-16 slice of 16-bit code units.

src/libstd/sys/unix/mod.rs

@@ -43,6 +43,7 @@ pub mod fs2;
 pub mod handle;
 pub mod helper_signal;
 pub mod mutex;
+pub mod net;
 pub mod os;
 pub mod os_str;
 pub mod pipe;

src/libstd/sys/unix/net.rs

@@ -0,0 +1,121 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use prelude::v1::*;
+
+use io;
+use libc::consts::os::extra::INVALID_SOCKET;
+use libc::{self, c_int, c_void};
+use mem;
+use net::{SocketAddr, IpAddr};
+use num::{SignedInt, Int};
+use rt;
+use sync::{Once, ONCE_INIT};
+use sys::c;
+use sys_common::AsInner;
+
+pub type wrlen_t = i32;
+
+pub struct Socket(libc::SOCKET);
+
+pub fn init() {
+    static START: Once = ONCE_INIT;
+
+    START.call_once(|| unsafe {
+        let mut data: c::WSADATA = mem::zeroed();
+        let ret = c::WSAStartup(0x202, // version 2.2
+                                &mut data);
+        assert_eq!(ret, 0);
+
+        rt::at_exit(|| { c::WSACleanup(); })
+    });
+}
+
+fn last_error() -> io::Error {
+    io::Error::from_os_error(unsafe { c::WSAGetLastError() })
+}
+
+pub fn cvt<T: SignedInt>(t: T) -> io::Result<T> {
+    let one: T = Int::one();
+    if t == -one {
+        Err(last_error())
+    } else {
+        Ok(t)
+    }
+}
+
+pub fn cvt_gai(err: c_int) -> io::Result<()> {
+    if err == 0 { return Ok(()) }
+    cvt(err).map(|_| ())
+}
+
+pub fn cvt_r<T: SignedInt, F>(mut f: F) -> io::Result<T> where F: FnMut() -> T {
+    cvt(f())
+}
+
+impl Socket {
+    pub fn new(addr: &SocketAddr, ty: c_int) -> io::Result<Socket> {
+        let fam = match addr.ip {
+            IpAddr::V4(..) => libc::AF_INET,
+            IpAddr::V6(..) => libc::AF_INET6,
+        };
+        match unsafe { libc::socket(fam, ty, 0) } {
+            INVALID_SOCKET => Err(last_error()),
+            n => Ok(Socket(n)),
+        }
+    }
+
+    pub fn accept(&self, storage: *mut libc::sockaddr,
+                  len: *mut libc::socklen_t) -> io::Result<Socket> {
+        match unsafe { libc::accept(self.0, storage, len) } {
+            INVALID_SOCKET => Err(last_error()),
+            n => Ok(Socket(n)),
+        }
+    }
+
+    pub fn duplicate(&self) -> io::Result<Socket> {
+        unsafe {
+            let mut info: c::WSAPROTOCOL_INFO = mem::zeroed();
+            try!(cvt(c::WSADuplicateSocketW(self.0,
+                                            c::GetCurrentProcessId(),
+                                            &mut info)));
+            match c::WSASocketW(info.iAddressFamily,
+                                info.iSocketType,
+                                info.iProtocol,
+                                &mut info, 0, 0) {
+                INVALID_SOCKET => Err(last_error()),
+                n => Ok(Socket(n)),
+            }
+        }
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        // On unix when a socket is shut down all further reads return 0, so we
+        // do the same on windows to map a shut down socket to returning EOF.
+        unsafe {
+            match libc::recv(self.0, buf.as_mut_ptr() as *mut c_void,
+                             buf.len() as i32, 0) {
+                -1 if c::WSAGetLastError() == c::WSAESHUTDOWN => Ok(0),
+                -1 => Err(last_error()),
+                n => Ok(n as usize)
+            }
+        }
+    }
+}
+
+impl Drop for Socket {
+    fn drop(&mut self) {
+        unsafe { let _ = libc::closesocket(self.0); }
+    }
+}
+
+impl AsInner<libc::SOCKET> for Socket {
+    fn as_inner(&self) -> &libc::SOCKET { &self.0 }
+}