/** * Returns the hostname for this address. * * <p>If there is a security manager, this method first calls its <code>checkConnect</code> method * with the hostname and <code>-1</code> as its arguments to see if the calling code is allowed to * know the hostname for this IP address, i.e., to connect to the host. If the operation is not * allowed, it will return the textual representation of the IP address. * * @return the host name for this IP address, or if the operation is not allowed by the security * check, the textual representation of the IP address. * @param check make security check if true * @see SecurityManager#checkConnect */ private static String getHostFromNameService(InetAddress addr, boolean check) { String host = null; for (NameService nameService : nameServices) { try { // first lookup the hostname host = nameService.getHostByAddr(addr.getAddress()); /* check to see if calling code is allowed to know * the hostname for this IP address, ie, connect to the host */ if (check) { SecurityManager sec = System.getSecurityManager(); if (sec != null) { sec.checkConnect(host, -1); } } /* now get all the IP addresses for this hostname, * and make sure one of them matches the original IP * address. We do this to try and prevent spoofing. */ InetAddress[] arr = InetAddress.getAllByName0(host, check); boolean ok = false; if (arr != null) { for (int i = 0; !ok && i < arr.length; i++) { ok = addr.equals(arr[i]); } } // XXX: if it looks a spoof just return the address? if (!ok) { host = addr.getHostAddress(); return host; } break; } catch (SecurityException e) { host = addr.getHostAddress(); break; } catch (UnknownHostException e) { host = addr.getHostAddress(); // let next provider resolve the hostname } } return host; }