Add reverse dns lookup as a method on InternetAddress.

runtime/bin/socket_macos.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include <errno.h>  // NOLINT
 #include <stdio.h>  // NOLINT
 #include <stdlib.h>  // NOLINT
@@ skipping 203 matching lines @@
     if (c->ai_family == AF_INET || c->ai_family == AF_INET6) {
       addresses->SetAt(i, new SocketAddress(c->ai_addr));
       i++;
     }
   }
   freeaddrinfo(info);
   return addresses;
 }
 
 
+const char* Socket::ReverseLookup(RawAddr addr, OSError** os_error) {
+  char* host = new char[NI_MAXHOST];
+  int status = TEMP_FAILURE_RETRY(getnameinfo(
+      &addr.addr,
+      SocketAddress::GetAddrLength(&addr),
+      host,
+      NI_MAXHOST,
+      NULL,
+      0,
+      NI_NAMEREQD));
+  if (status != 0) {
+    ASSERT(*os_error == NULL);
+    *os_error = new OSError(status,
+                            gai_strerror(status),
+                            OSError::kGetAddressInfo);
+    delete host;
+    return NULL;
+  }
+  return host;
+}
+
+
 static bool ShouldIncludeIfaAddrs(struct ifaddrs* ifa, int lookup_family) {
   int family = ifa->ifa_addr->sa_family;
   if (lookup_family == family) return true;
   if (lookup_family == AF_UNSPEC &&
       (family == AF_INET || family == AF_INET6)) {
     return true;
   }
   return false;
 }
 
@@ skipping 122 matching lines @@
                                        IPPROTO_TCP,
                                        TCP_NODELAY,
                                        reinterpret_cast<char *>(&on),
                                        sizeof(on))) == 0;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)