Add peer_addr function to UdpSocket

src/libstd/net/udp.rs

@@ -180,6 +180,23 @@ impl UdpSocket {
         }
     }
 
+    /// Returns the socket address of the remote peer this socket was connected to.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// use std::net::{Ipv4Addr, SocketAddr, SocketAddrV4, UdpSocket};
+    ///
+    /// let socket = UdpSocket::bind("127.0.0.1:34254").expect("couldn't bind to address");
+    /// socket.connect("192.168.0.1:41203").expect("couldn't connect to address");
+    /// assert_eq!(socket.peer_addr().unwrap(),
+    ///            SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(192, 168, 0, 1), 41203)));
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
+        self.0.peer_addr()
+    }
+
     /// Returns the socket address that this socket was created from.
     ///
     /// # Examples

src/libstd/sys/cloudabi/shims/net.rs

@@ -159,6 +159,10 @@ impl UdpSocket {
         unsupported()
     }
 
+    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
+        match self.0 {}
+    }
+
     pub fn socket_addr(&self) -> io::Result<SocketAddr> {
         match self.0 {}
     }

src/libstd/sys/redox/net/udp.rs

@@ -72,6 +72,11 @@ impl UdpSocket {
         Ok(None)
     }
 
+    pub fn peer_addr(&self) -> Result<SocketAddr> {
+        let path = self.0.path()?;
+        Ok(path_to_peer_addr(path.to_str().unwrap_or("")))
+    }
+
     pub fn socket_addr(&self) -> Result<SocketAddr> {
         let path = self.0.path()?;
         Ok(path_to_local_addr(path.to_str().unwrap_or("")))

src/libstd/sys/sgx/net.rs

@@ -257,6 +257,10 @@ impl UdpSocket {
         unsupported()
     }
 
+    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
+        match self.0 {}
+    }
+
     pub fn socket_addr(&self) -> io::Result<SocketAddr> {
         match self.0 {}
     }

src/libstd/sys_common/net.rs

@@ -472,6 +472,12 @@ impl UdpSocket {
 
     pub fn into_socket(self) -> Socket { self.inner }
 
+    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            c::getpeername(*self.inner.as_inner(), buf, len)
+        })
+    }
+
     pub fn socket_addr(&self) -> io::Result<SocketAddr> {
         sockname(|buf, len| unsafe {
             c::getsockname(*self.inner.as_inner(), buf, len)