Set SO_REUSEADDR by default in libnative.

Fixes std::net test error when re-running too quickly.

src/libnative/io/net.rs

@@ -348,6 +348,17 @@ impl TcpListener {
                 let (addr, len) = addr_to_sockaddr(addr);
                 let addrp = &addr as *libc::sockaddr_storage;
                 let ret = TcpListener { fd: fd };
+                // 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!(unix) {
+                    match setsockopt(fd, libc::SOL_SOCKET,
+                                     libc::SO_REUSEADDR,
+                                     1 as libc::c_int) {
+                        Err(n) => { return Err(n); },
+                        Ok(..) => { }
+                    }
+                }
                 match libc::bind(fd, addrp as *libc::sockaddr,
                                  len as libc::socklen_t) {
                     -1 => Err(super::last_error()),

src/libstd/io/net/tcp.rs

@@ -609,4 +609,44 @@ mod test {
         c.write([1]);
         p.recv();
     })
+
+    iotest!(fn double_bind() {
+        let mut called = false;
+        io_error::cond.trap(|e| {
+            assert!(e.kind == ConnectionRefused || e.kind == OtherIoError);
+            called = true;
+        }).inside(|| {
+            let addr = next_test_ip4();
+            let listener = TcpListener::bind(addr).unwrap().listen();
+            assert!(listener.is_some());
+            let listener2 = TcpListener::bind(addr).and_then(|l|
+                                                    l.listen());
+            assert!(listener2.is_none());
+        });
+        assert!(called);
+    })
+
+    iotest!(fn fast_rebind() {
+        let addr = next_test_ip4();
+        let (port, chan) = Chan::new();
+
+        do spawn {
+            port.recv();
+            let stream = TcpStream::connect(addr);
+            // Close
+            port.recv();
+        }
+
+        {
+            let mut acceptor = TcpListener::bind(addr).listen();
+            chan.send(());
+            {
+                let stream = acceptor.accept();
+                // Close client
+                chan.send(());
+            }
+            // Close listener
+        }
+        let listener = TcpListener::bind(addr);
+    })
 }

src/libstd/libc.rs

@@ -1547,6 +1547,7 @@ pub mod consts {
             pub static SOL_SOCKET: c_int = 0xffff;
             pub static SO_KEEPALIVE: c_int = 8;
             pub static SO_BROADCAST: c_int = 32;
+            pub static SO_REUSEADDR: c_int = 4;
         }
         pub mod extra {
             use libc::types::os::arch::c95::c_int;
@@ -2266,6 +2267,7 @@ pub mod consts {
             pub static SOL_SOCKET: c_int = 1;
             pub static SO_KEEPALIVE: c_int = 9;
             pub static SO_BROADCAST: c_int = 6;
+            pub static SO_REUSEADDR: c_int = 2;
         }
         #[cfg(target_arch = "x86")]
         #[cfg(target_arch = "x86_64")]
@@ -2707,6 +2709,7 @@ pub mod consts {
             pub static SOL_SOCKET: c_int = 0xffff;
             pub static SO_KEEPALIVE: c_int = 0x0008;
             pub static SO_BROADCAST: c_int = 0x0020;
+            pub static SO_REUSEADDR: c_int = 0x0004;
         }
         pub mod extra {
             use libc::types::os::arch::c95::c_int;
@@ -3083,6 +3086,7 @@ pub mod consts {
             pub static SOL_SOCKET: c_int = 0xffff;
             pub static SO_KEEPALIVE: c_int = 0x0008;
             pub static SO_BROADCAST: c_int = 0x0020;
+            pub static SO_REUSEADDR: c_int = 0x0004;
         }
         pub mod extra {
             use libc::types::os::arch::c95::c_int;