node/src/cares_wrap.cc

// Copyright Joyent, Inc. and other Node contributors.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to permit
// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
// USE OR OTHER DEALINGS IN THE SOFTWARE.

#define CARES_STATICLIB
#include "ares.h"
#include "node.h"
#include "req_wrap.h"
#include "tree.h"
#include "uv.h"

#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#if defined(__ANDROID__) || \
    defined(__MINGW32__) || \
    defined(__OpenBSD__) || \
    defined(_MSC_VER)
# include <nameser.h>
#else
# include <arpa/nameser.h>
#endif


namespace node {
namespace cares_wrap {

using v8::Array;
using v8::Function;
using v8::FunctionCallbackInfo;
using v8::Handle;
using v8::HandleScope;
using v8::Integer;
using v8::Local;
using v8::Null;
using v8::Object;
using v8::Persistent;
using v8::String;
using v8::Value;


typedef class ReqWrap<uv_getaddrinfo_t> GetAddrInfoReqWrap;

struct ares_task_t {
  UV_HANDLE_FIELDS
  ares_socket_t sock;
  uv_poll_t poll_watcher;
  RB_ENTRY(ares_task_t) node;
};


static Cached<String> oncomplete_sym;
static ares_channel ares_channel;
static uv_timer_t ares_timer;
static RB_HEAD(ares_task_list, ares_task_t) ares_tasks;


static int cmp_ares_tasks(const ares_task_t* a, const ares_task_t* b) {
  if (a->sock < b->sock) return -1;
  if (a->sock > b->sock) return 1;
  return 0;
}


RB_GENERATE_STATIC(ares_task_list, ares_task_t, node, cmp_ares_tasks)



/* This is called once per second by loop->timer. It is used to constantly */
/* call back into c-ares for possibly processing timeouts. */
static void ares_timeout(uv_timer_t* handle, int status) {
  assert(!RB_EMPTY(&ares_tasks));
  ares_process_fd(ares_channel, ARES_SOCKET_BAD, ARES_SOCKET_BAD);
}


static void ares_poll_cb(uv_poll_t* watcher, int status, int events) {
  ares_task_t* task = container_of(watcher, ares_task_t, poll_watcher);

  /* Reset the idle timer */
  uv_timer_again(&ares_timer);

  if (status < 0) {
    /* An error happened. Just pretend that the socket is both readable and */
    /* writable. */
    ares_process_fd(ares_channel, task->sock, task->sock);
    return;
  }

  /* Process DNS responses */
  ares_process_fd(ares_channel,
                  events & UV_READABLE ? task->sock : ARES_SOCKET_BAD,
                  events & UV_WRITABLE ? task->sock : ARES_SOCKET_BAD);
}


static void ares_poll_close_cb(uv_handle_t* watcher) {
  ares_task_t* task = container_of(watcher, ares_task_t, poll_watcher);
  free(task);
}


/* Allocates and returns a new ares_task_t */
static ares_task_t* ares_task_create(uv_loop_t* loop, ares_socket_t sock) {
  ares_task_t* task = static_cast<ares_task_t*>(malloc(sizeof(*task)));

  if (task == NULL) {
    /* Out of memory. */
    return NULL;
  }

  task->loop = loop;
  task->sock = sock;

  if (uv_poll_init_socket(loop, &task->poll_watcher, sock) < 0) {
    /* This should never happen. */
    free(task);
    return NULL;
  }

  return task;
}


/* Callback from ares when socket operation is started */
static void ares_sockstate_cb(void* data,
                              ares_socket_t sock,
                              int read,
                              int write) {
  uv_loop_t* loop = static_cast<uv_loop_t*>(data);
  ares_task_t* task;

  ares_task_t lookup_task;
  lookup_task.sock = sock;
  task = RB_FIND(ares_task_list, &ares_tasks, &lookup_task);

  if (read || write) {
    if (!task) {
      /* New socket */

      /* If this is the first socket then start the timer. */
      if (!uv_is_active(reinterpret_cast<uv_handle_t*>(&ares_timer))) {
        assert(RB_EMPTY(&ares_tasks));
        uv_timer_start(&ares_timer, ares_timeout, 1000, 1000);
      }

      task = ares_task_create(loop, sock);
      if (task == NULL) {
        /* This should never happen unless we're out of memory or something */
        /* is seriously wrong. The socket won't be polled, but the the query */
        /* will eventually time out. */
        return;
      }

      RB_INSERT(ares_task_list, &ares_tasks, task);
    }

    /* This should never fail. If it fails anyway, the query will eventually */
    /* time out. */
    uv_poll_start(&task->poll_watcher,
                  (read ? UV_READABLE : 0) | (write ? UV_WRITABLE : 0),
                  ares_poll_cb);

  } else {
    /* read == 0 and write == 0 this is c-ares's way of notifying us that */
    /* the socket is now closed. We must free the data associated with */
    /* socket. */
    assert(task &&
           "When an ares socket is closed we should have a handle for it");

    RB_REMOVE(ares_task_list, &ares_tasks, task);
    uv_close(reinterpret_cast<uv_handle_t*>(&task->poll_watcher),
             ares_poll_close_cb);

    if (RB_EMPTY(&ares_tasks)) {
      uv_timer_stop(&ares_timer);
    }
  }
}


static Local<Array> HostentToAddresses(struct hostent* host) {
  HandleScope scope(node_isolate);
  Local<Array> addresses = Array::New();

  char ip[INET6_ADDRSTRLEN];
  for (int i = 0; host->h_addr_list[i]; ++i) {
    uv_inet_ntop(host->h_addrtype, host->h_addr_list[i], ip, sizeof(ip));

    Local<String> address = String::New(ip);
    addresses->Set(Integer::New(i, node_isolate), address);
  }

  return scope.Close(addresses);
}


static Local<Array> HostentToNames(struct hostent* host) {
  HandleScope scope(node_isolate);
  Local<Array> names = Array::New();

  for (int i = 0; host->h_aliases[i]; ++i) {
    Local<String> address = String::New(host->h_aliases[i]);
    names->Set(Integer::New(i, node_isolate), address);
  }

  return scope.Close(names);
}


class QueryWrap {
 public:
  explicit QueryWrap(Local<Object> req_wrap_obj) {
    HandleScope scope(node_isolate);
    persistent().Reset(node_isolate, req_wrap_obj);
  }

  virtual ~QueryWrap() {
    assert(!persistent().IsEmpty());
    object()->Delete(oncomplete_sym);
    persistent().Dispose();
  }

  void SetOnComplete(Handle<Value> oncomplete) {
    assert(oncomplete->IsFunction());
    object()->Set(oncomplete_sym, oncomplete);
  }

  // Subclasses should implement the appropriate Send method.
  virtual int Send(const char* name) {
    assert(0);
    return 0;
  }

  virtual int Send(const char* name, int family) {
    assert(0);
    return 0;
  }

  inline Persistent<Object>& persistent() {
    return object_;
  }

  inline Local<Object> object() {
    return PersistentToLocal(node_isolate, persistent());
  }

 protected:
  void* GetQueryArg() {
    return static_cast<void*>(this);
  }

  static void Callback(void *arg, int status, int timeouts,
      unsigned char* answer_buf, int answer_len) {
    QueryWrap* wrap = static_cast<QueryWrap*>(arg);

    if (status != ARES_SUCCESS) {
      wrap->ParseError(status);
    } else {
      wrap->Parse(answer_buf, answer_len);
    }

    delete wrap;
  }

  static void Callback(void *arg, int status, int timeouts,
      struct hostent* host) {
    QueryWrap* wrap = static_cast<QueryWrap*>(arg);

    if (status != ARES_SUCCESS) {
      wrap->ParseError(status);
    } else {
      wrap->Parse(host);
    }

    delete wrap;
  }

  void CallOnComplete(Local<Value> answer) {
    HandleScope scope(node_isolate);
    Local<Value> argv[2] = { Integer::New(0, node_isolate), answer };
    MakeCallback(object(), oncomplete_sym, ARRAY_SIZE(argv), argv);
  }

  void CallOnComplete(Local<Value> answer, Local<Value> family) {
    HandleScope scope(node_isolate);
    Local<Value> argv[3] = { Integer::New(0, node_isolate), answer, family };
    MakeCallback(object(), oncomplete_sym, ARRAY_SIZE(argv), argv);
  }

  void ParseError(int status) {
    assert(status != ARES_SUCCESS);
    HandleScope scope(node_isolate);
    Local<Value> argv[] = {
      Integer::New(status, node_isolate)
    };
    MakeCallback(object(), oncomplete_sym, ARRAY_SIZE(argv), argv);
  }

  // Subclasses should implement the appropriate Parse method.
  virtual void Parse(unsigned char* buf, int len) {
    assert(0);
  };

  virtual void Parse(struct hostent* host) {
    assert(0);
  };

 private:
  Persistent<Object> object_;
};


class QueryAWrap: public QueryWrap {
 public:
  explicit QueryAWrap(Local<Object> req_wrap_obj) : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel, name, ns_c_in, ns_t_a, Callback, GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    HandleScope scope(node_isolate);

    struct hostent* host;

    int status = ares_parse_a_reply(buf, len, &host, NULL, NULL);
    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    Local<Array> addresses = HostentToAddresses(host);
    ares_free_hostent(host);

    this->CallOnComplete(addresses);
  }
};


class QueryAaaaWrap: public QueryWrap {
 public:
  explicit QueryAaaaWrap(Local<Object> req_wrap_obj) : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel,
               name,
               ns_c_in,
               ns_t_aaaa,
               Callback,
               GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    HandleScope scope(node_isolate);

    struct hostent* host;

    int status = ares_parse_aaaa_reply(buf, len, &host, NULL, NULL);
    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    Local<Array> addresses = HostentToAddresses(host);
    ares_free_hostent(host);

    this->CallOnComplete(addresses);
  }
};


class QueryCnameWrap: public QueryWrap {
 public:
  explicit QueryCnameWrap(Local<Object> req_wrap_obj)
      : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel,
               name,
               ns_c_in,
               ns_t_cname,
               Callback,
               GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    HandleScope scope(node_isolate);

    struct hostent* host;

    int status = ares_parse_a_reply(buf, len, &host, NULL, NULL);
    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    // A cname lookup always returns a single record but we follow the
    // common API here.
    Local<Array> result = Array::New(1);
    result->Set(0, String::New(host->h_name));
    ares_free_hostent(host);

    this->CallOnComplete(result);
  }
};


class QueryMxWrap: public QueryWrap {
 public:
  explicit QueryMxWrap(Local<Object> req_wrap_obj) : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel, name, ns_c_in, ns_t_mx, Callback, GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    HandleScope scope(node_isolate);

    struct ares_mx_reply* mx_start;
    int status = ares_parse_mx_reply(buf, len, &mx_start);
    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    Local<Array> mx_records = Array::New();
    Local<String> exchange_symbol = String::NewSymbol("exchange");
    Local<String> priority_symbol = String::NewSymbol("priority");
    int i = 0;
    for (struct ares_mx_reply* mx_current = mx_start;
         mx_current;
         mx_current = mx_current->next) {
      Local<Object> mx_record = Object::New();
      mx_record->Set(exchange_symbol, String::New(mx_current->host));
      mx_record->Set(priority_symbol,
                     Integer::New(mx_current->priority, node_isolate));
      mx_records->Set(Integer::New(i++, node_isolate), mx_record);
    }

    ares_free_data(mx_start);

    this->CallOnComplete(mx_records);
  }
};


class QueryNsWrap: public QueryWrap {
 public:
  explicit QueryNsWrap(Local<Object> req_wrap_obj) : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel, name, ns_c_in, ns_t_ns, Callback, GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    struct hostent* host;

    int status = ares_parse_ns_reply(buf, len, &host);
    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    Local<Array> names = HostentToNames(host);
    ares_free_hostent(host);

    this->CallOnComplete(names);
  }
};


class QueryTxtWrap: public QueryWrap {
 public:
  explicit QueryTxtWrap(Local<Object> req_wrap_obj) : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel, name, ns_c_in, ns_t_txt, Callback, GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    struct ares_txt_reply* txt_out;

    int status = ares_parse_txt_reply(buf, len, &txt_out);
    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    Local<Array> txt_records = Array::New();

    struct ares_txt_reply *current = txt_out;
    for (int i = 0; current; ++i, current = current->next) {
      Local<String> txt = String::New(reinterpret_cast<char*>(current->txt));
      txt_records->Set(Integer::New(i, node_isolate), txt);
    }

    ares_free_data(txt_out);

    this->CallOnComplete(txt_records);
  }
};


class QuerySrvWrap: public QueryWrap {
 public:
  explicit QuerySrvWrap(Local<Object> req_wrap_obj) : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel,
               name,
               ns_c_in,
               ns_t_srv,
               Callback,
               GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    HandleScope scope(node_isolate);

    struct ares_srv_reply* srv_start;
    int status = ares_parse_srv_reply(buf, len, &srv_start);
    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    Local<Array> srv_records = Array::New();
    Local<String> name_symbol = String::NewSymbol("name");
    Local<String> port_symbol = String::NewSymbol("port");
    Local<String> priority_symbol = String::NewSymbol("priority");
    Local<String> weight_symbol = String::NewSymbol("weight");
    int i = 0;
    for (struct ares_srv_reply* srv_current = srv_start;
         srv_current;
         srv_current = srv_current->next) {
      Local<Object> srv_record = Object::New();
      srv_record->Set(name_symbol, String::New(srv_current->host));
      srv_record->Set(port_symbol,
                      Integer::New(srv_current->port, node_isolate));
      srv_record->Set(priority_symbol,
                      Integer::New(srv_current->priority, node_isolate));
      srv_record->Set(weight_symbol,
                      Integer::New(srv_current->weight, node_isolate));
      srv_records->Set(Integer::New(i++, node_isolate), srv_record);
    }

    ares_free_data(srv_start);

    this->CallOnComplete(srv_records);
  }
};

class QueryNaptrWrap: public QueryWrap {
 public:
  explicit QueryNaptrWrap(Local<Object> req_wrap_obj)
      : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    ares_query(ares_channel,
               name,
               ns_c_in,
               ns_t_naptr,
               Callback,
               GetQueryArg());
    return 0;
  }

 protected:
  void Parse(unsigned char* buf, int len) {
    HandleScope scope(node_isolate);

    ares_naptr_reply* naptr_start;
    int status = ares_parse_naptr_reply(buf, len, &naptr_start);

    if (status != ARES_SUCCESS) {
      this->ParseError(status);
      return;
    }

    Local<Array> naptr_records = Array::New();
    Local<String> flags_symbol = String::NewSymbol("flags");
    Local<String> service_symbol = String::NewSymbol("service");
    Local<String> regexp_symbol = String::NewSymbol("regexp");
    Local<String> replacement_symbol = String::NewSymbol("replacement");
    Local<String> order_symbol = String::NewSymbol("order");
    Local<String> preference_symbol = String::NewSymbol("preference");

    int i = 0;
    for (ares_naptr_reply* naptr_current = naptr_start;
         naptr_current;
         naptr_current = naptr_current->next) {
      Local<Object> naptr_record = Object::New();

      naptr_record->Set(flags_symbol,
          String::New(reinterpret_cast<char*>(naptr_current->flags)));
      naptr_record->Set(service_symbol,
          String::New(reinterpret_cast<char*>(naptr_current->service)));
      naptr_record->Set(regexp_symbol,
          String::New(reinterpret_cast<char*>(naptr_current->regexp)));
      naptr_record->Set(replacement_symbol,
          String::New(naptr_current->replacement));
      naptr_record->Set(order_symbol, Integer::New(naptr_current->order,
                                                   node_isolate));
      naptr_record->Set(preference_symbol,
          Integer::New(naptr_current->preference, node_isolate));

      naptr_records->Set(Integer::New(i++, node_isolate), naptr_record);
    }

    ares_free_data(naptr_start);

    this->CallOnComplete(naptr_records);
  }
};


class GetHostByAddrWrap: public QueryWrap {
 public:
  explicit GetHostByAddrWrap(Local<Object> req_wrap_obj)
      : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name) {
    int length, family;
    char address_buffer[sizeof(struct in6_addr)];

    if (uv_inet_pton(AF_INET, name, &address_buffer) == 0) {
      length = sizeof(struct in_addr);
      family = AF_INET;
    } else if (uv_inet_pton(AF_INET6, name, &address_buffer) == 0) {
      length = sizeof(struct in6_addr);
      family = AF_INET6;
    } else {
      return UV_EINVAL;  // So errnoException() reports a proper error.
    }

    ares_gethostbyaddr(ares_channel,
                       address_buffer,
                       length,
                       family,
                       Callback,
                       GetQueryArg());
    return 0;
  }

 protected:
  void Parse(struct hostent* host) {
    HandleScope scope(node_isolate);

    this->CallOnComplete(HostentToNames(host));
  }
};


class GetHostByNameWrap: public QueryWrap {
 public:
  explicit GetHostByNameWrap(Local<Object> req_wrap_obj)
      : QueryWrap(req_wrap_obj) {
  }

  int Send(const char* name, int family) {
    ares_gethostbyname(ares_channel, name, family, Callback, GetQueryArg());
    return 0;
  }

 protected:
  void Parse(struct hostent* host) {
    HandleScope scope(node_isolate);

    Local<Array> addresses = HostentToAddresses(host);
    Local<Integer> family = Integer::New(host->h_addrtype, node_isolate);

    this->CallOnComplete(addresses, family);
  }
};


template <class Wrap>
static void Query(const FunctionCallbackInfo<Value>& args) {
  HandleScope scope(node_isolate);

  assert(!args.IsConstructCall());
  assert(args[0]->IsObject());
  assert(args[1]->IsString());
  assert(args[2]->IsFunction());

  Local<Object> req_wrap_obj = args[0].As<Object>();
  Local<String> string = args[1].As<String>();
  Local<Function> callback = args[2].As<Function>();

  Wrap* wrap = new Wrap(req_wrap_obj);
  wrap->SetOnComplete(callback);

  String::Utf8Value name(string);
  int err = wrap->Send(*name);
  if (err) delete wrap;

  args.GetReturnValue().Set(err);
}


template <class Wrap>
static void QueryWithFamily(const FunctionCallbackInfo<Value>& args) {
  HandleScope scope(node_isolate);

  assert(!args.IsConstructCall());
  assert(args[0]->IsObject());
  assert(args[1]->IsString());
  assert(args[2]->IsInt32());
  assert(args[3]->IsFunction());

  Local<Object> req_wrap_obj = args[0].As<Object>();
  Local<String> string = args[1].As<String>();
  int family = args[2]->Int32Value();
  Local<Function> callback = args[3].As<Function>();

  Wrap* wrap = new Wrap(req_wrap_obj);
  wrap->SetOnComplete(callback);

  String::Utf8Value name(string);
  int err = wrap->Send(*name, family);
  if (err) delete wrap;

  args.GetReturnValue().Set(err);
}


void AfterGetAddrInfo(uv_getaddrinfo_t* req, int status, struct addrinfo* res) {
  HandleScope scope(node_isolate);

  GetAddrInfoReqWrap* req_wrap =
      reinterpret_cast<GetAddrInfoReqWrap*>(req->data);

  Local<Value> argv[] = {
    Integer::New(status, node_isolate),
    Null(node_isolate)
  };

  if (status == 0) {
    // Success
    struct addrinfo *address;
    int n = 0;

    // Count the number of responses.
    for (address = res; address; address = address->ai_next) {
      n++;
    }

    // Create the response array.
    Local<Array> results = Array::New(n);

    char ip[INET6_ADDRSTRLEN];
    const char *addr;

    n = 0;

    // Iterate over the IPv4 responses again this time creating javascript
    // strings for each IP and filling the results array.
    address = res;
    while (address) {
      assert(address->ai_socktype == SOCK_STREAM);

      // Ignore random ai_family types.
      if (address->ai_family == AF_INET) {
        // Juggle pointers
        addr = reinterpret_cast<char*>(&(reinterpret_cast<struct sockaddr_in*>(
            address->ai_addr)->sin_addr));
        int err = uv_inet_ntop(address->ai_family,
                               addr,
                               ip,
                               INET6_ADDRSTRLEN);
        if (err)
          continue;

        // Create JavaScript string
        Local<String> s = String::New(ip);
        results->Set(n, s);
        n++;
      }

      // Increment
      address = address->ai_next;
    }

    // Iterate over the IPv6 responses putting them in the array.
    address = res;
    while (address) {
      assert(address->ai_socktype == SOCK_STREAM);

      // Ignore random ai_family types.
      if (address->ai_family == AF_INET6) {
        // Juggle pointers
        addr = reinterpret_cast<char*>(&(reinterpret_cast<struct sockaddr_in6*>(
            address->ai_addr)->sin6_addr));
        int err = uv_inet_ntop(address->ai_family,
                               addr,
                               ip,
                               INET6_ADDRSTRLEN);
        if (err)
          continue;

        // Create JavaScript string
        Local<String> s = String::New(ip);
        results->Set(n, s);
        n++;
      }

      // Increment
      address = address->ai_next;
    }


    argv[1] = results;
  }

  uv_freeaddrinfo(res);

  // Make the callback into JavaScript
  MakeCallback(req_wrap->object(), oncomplete_sym, ARRAY_SIZE(argv), argv);

  delete req_wrap;
}


static void IsIP(const FunctionCallbackInfo<Value>& args) {
  HandleScope scope(node_isolate);

  String::AsciiValue ip(args[0]);
  char address_buffer[sizeof(struct in6_addr)];

  int rc = 0;
  if (uv_inet_pton(AF_INET, *ip, &address_buffer) == 0)
    rc = 4;
  else if (uv_inet_pton(AF_INET6, *ip, &address_buffer) == 0)
    rc = 6;

  args.GetReturnValue().Set(rc);
}


static void GetAddrInfo(const FunctionCallbackInfo<Value>& args) {
  HandleScope scope(node_isolate);

  assert(args[0]->IsObject());
  assert(args[1]->IsString());
  assert(args[2]->IsInt32());
  Local<Object> req_wrap_obj = args[0].As<Object>();
  String::Utf8Value hostname(args[1]);

  int family;
  switch (args[2]->Int32Value()) {
  case 0:
    family = AF_UNSPEC;
    break;
  case 4:
    family = AF_INET;
    break;
  case 6:
    family = AF_INET6;
    break;
  default:
    assert(0 && "bad address family");
    abort();
  }

  GetAddrInfoReqWrap* req_wrap = new GetAddrInfoReqWrap(req_wrap_obj);

  struct addrinfo hints;
  memset(&hints, 0, sizeof(struct addrinfo));
  hints.ai_family = family;
  hints.ai_socktype = SOCK_STREAM;

  int err = uv_getaddrinfo(uv_default_loop(),
                           &req_wrap->req_,
                           AfterGetAddrInfo,
                           *hostname,
                           NULL,
                           &hints);
  req_wrap->Dispatched();
  if (err) delete req_wrap;

  args.GetReturnValue().Set(err);
}


static void GetServers(const FunctionCallbackInfo<Value>& args) {
  HandleScope scope(node_isolate);

  Local<Array> server_array = Array::New();

  ares_addr_node* servers;

  int r = ares_get_servers(ares_channel, &servers);
  assert(r == ARES_SUCCESS);

  ares_addr_node* cur = servers;

  for (int i = 0; cur != NULL; ++i, cur = cur->next) {
    char ip[INET6_ADDRSTRLEN];

    const void* caddr = static_cast<const void*>(&cur->addr);
    int err = uv_inet_ntop(cur->family, caddr, ip, sizeof(ip));
    assert(err == 0);

    Local<String> addr = String::New(ip);
    server_array->Set(i, addr);
  }

  ares_free_data(servers);

  args.GetReturnValue().Set(server_array);
}


static void SetServers(const FunctionCallbackInfo<Value>& args) {
  HandleScope scope(node_isolate);

  assert(args[0]->IsArray());

  Local<Array> arr = Local<Array>::Cast(args[0]);

  uint32_t len = arr->Length();

  if (len == 0) {
    int rv = ares_set_servers(ares_channel, NULL);
    return args.GetReturnValue().Set(rv);
  }

  ares_addr_node* servers = new ares_addr_node[len];
  ares_addr_node* last = NULL;

  int err;

  for (uint32_t i = 0; i < len; i++) {
    assert(arr->Get(i)->IsArray());

    Local<Array> elm = Local<Array>::Cast(arr->Get(i));

    assert(elm->Get(0)->Int32Value());
    assert(elm->Get(1)->IsString());

    int fam = elm->Get(0)->Int32Value();
    String::Utf8Value ip(elm->Get(1));

    ares_addr_node* cur = &servers[i];

    switch (fam) {
      case 4:
        cur->family = AF_INET;
        err = uv_inet_pton(AF_INET, *ip, &cur->addr);
        break;
      case 6:
        cur->family = AF_INET6;
        err = uv_inet_pton(AF_INET6, *ip, &cur->addr);
        break;
      default:
        assert(0 && "Bad address family.");
        abort();
    }

    if (err)
      break;

    cur->next = NULL;

    if (last != NULL)
      last->next = cur;

    last = cur;
  }

  if (err == 0)
    err = ares_set_servers(ares_channel, &servers[0]);
  else
    err = ARES_EBADSTR;

  delete[] servers;

  args.GetReturnValue().Set(err);
}


static void StrError(const FunctionCallbackInfo<Value>& args) {
  HandleScope scope(node_isolate);
  const char* errmsg = ares_strerror(args[0]->Int32Value());
  args.GetReturnValue().Set(String::New(errmsg));
}


static void Initialize(Handle<Object> target) {
  HandleScope scope(node_isolate);
  int r;

  r = ares_library_init(ARES_LIB_INIT_ALL);
  assert(r == ARES_SUCCESS);

  struct ares_options options;
  memset(&options, 0, sizeof(options));
  options.flags = ARES_FLAG_NOCHECKRESP;
  options.sock_state_cb = ares_sockstate_cb;
  options.sock_state_cb_data = uv_default_loop();

  /* We do the call to ares_init_option for caller. */
  r = ares_init_options(&ares_channel,
                        &options,
                        ARES_OPT_FLAGS | ARES_OPT_SOCK_STATE_CB);
  assert(r == ARES_SUCCESS);

  /* Initialize the timeout timer. The timer won't be started until the */
  /* first socket is opened. */
  uv_timer_init(uv_default_loop(), &ares_timer);

  NODE_SET_METHOD(target, "queryA", Query<QueryAWrap>);
  NODE_SET_METHOD(target, "queryAaaa", Query<QueryAaaaWrap>);
  NODE_SET_METHOD(target, "queryCname", Query<QueryCnameWrap>);
  NODE_SET_METHOD(target, "queryMx", Query<QueryMxWrap>);
  NODE_SET_METHOD(target, "queryNs", Query<QueryNsWrap>);
  NODE_SET_METHOD(target, "queryTxt", Query<QueryTxtWrap>);
  NODE_SET_METHOD(target, "querySrv", Query<QuerySrvWrap>);
  NODE_SET_METHOD(target, "queryNaptr", Query<QueryNaptrWrap>);
  NODE_SET_METHOD(target, "getHostByAddr", Query<GetHostByAddrWrap>);
  NODE_SET_METHOD(target, "getHostByName", QueryWithFamily<GetHostByNameWrap>);

  NODE_SET_METHOD(target, "getaddrinfo", GetAddrInfo);
  NODE_SET_METHOD(target, "isIP", IsIP);

  NODE_SET_METHOD(target, "strerror", StrError);
  NODE_SET_METHOD(target, "getServers", GetServers);
  NODE_SET_METHOD(target, "setServers", SetServers);

  target->Set(String::NewSymbol("AF_INET"),
              Integer::New(AF_INET, node_isolate));
  target->Set(String::NewSymbol("AF_INET6"),
              Integer::New(AF_INET6, node_isolate));
  target->Set(String::NewSymbol("AF_UNSPEC"),
              Integer::New(AF_UNSPEC, node_isolate));

  oncomplete_sym = String::New("oncomplete");
}

}  // namespace cares_wrap
}  // namespace node

NODE_MODULE(node_cares_wrap, node::cares_wrap::Initialize)