curl/ares/ares_init.c

/* $Id$ */

/* Copyright 1998 by the Massachusetts Institute of Technology.
 * Copyright (C) 2007-2008 by Daniel Stenberg
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */

#include "setup.h"

#if defined(WIN32) && !defined(WATT32)
#include <iphlpapi.h>
#include <malloc.h>
#endif

#ifdef HAVE_SYS_PARAM_H
#include <sys/param.h>
#endif

#ifdef HAVE_SYS_TIME_H
#include <sys/time.h>
#endif

#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif

#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif

#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif

#ifdef HAVE_ARPA_NAMESER_H
#  include <arpa/nameser.h>
#else
#  include "nameser.h"
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#  include <arpa/nameser_compat.h>
#endif

#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
#include <errno.h>
#include "ares.h"
#include "inet_net_pton.h"
#include "ares_private.h"

#ifdef WATT32
#undef WIN32  /* Redefined in MingW/MSVC headers */
#endif

static int init_by_options(ares_channel channel, const struct ares_options *options,
                           int optmask);
static int init_by_environment(ares_channel channel);
static int init_by_resolv_conf(ares_channel channel);
static int init_by_defaults(ares_channel channel);

static int config_nameserver(struct server_state **servers, int *nservers,
                             char *str);
static int set_search(ares_channel channel, const char *str);
static int set_options(ares_channel channel, const char *str);
static const char *try_option(const char *p, const char *q, const char *opt);
static int init_id_key(rc4_key* key,int key_data_len);

#ifndef WIN32
static int sortlist_alloc(struct apattern **sortlist, int *nsort, struct apattern *pat);
static int ip_addr(const char *s, int len, struct in_addr *addr);
static void natural_mask(struct apattern *pat);
static int config_domain(ares_channel channel, char *str);
static int config_lookup(ares_channel channel, const char *str,
                         const char *bindch, const char *filech);
static int config_sortlist(struct apattern **sortlist, int *nsort,
                           const char *str);
static char *try_config(char *s, const char *opt);
#endif

#define ARES_CONFIG_CHECK(x) (x->lookups && x->nsort > -1 && \
                             x->nservers > -1 && \
                             x->ndomains > -1 && \
                             x->ndots > -1 && x->timeout > -1 && \
                             x->tries > -1)

int ares_init(ares_channel *channelptr)
{
  return ares_init_options(channelptr, NULL, 0);
}

int ares_init_options(ares_channel *channelptr, struct ares_options *options,
                      int optmask)
{
  ares_channel channel;
  int i;
  int status = ARES_SUCCESS;
  struct server_state *server;
  struct timeval now;

#ifdef CURLDEBUG
  const char *env = getenv("CARES_MEMDEBUG");

  if (env)
    curl_memdebug(env);
  env = getenv("CARES_MEMLIMIT");
  if (env)
    curl_memlimit(atoi(env));
#endif

  channel = malloc(sizeof(struct ares_channeldata));
  if (!channel) {
    *channelptr = NULL;
    return ARES_ENOMEM;
  }

  now = ares__tvnow();

  /* Set everything to distinguished values so we know they haven't
   * been set yet.
   */
  channel->flags = -1;
  channel->timeout = -1;
  channel->tries = -1;
  channel->ndots = -1;
  channel->rotate = -1;
  channel->udp_port = -1;
  channel->tcp_port = -1;
  channel->socket_send_buffer_size = -1;
  channel->socket_receive_buffer_size = -1;
  channel->nservers = -1;
  channel->ndomains = -1;
  channel->nsort = -1;
  channel->tcp_connection_generation = 0;
  channel->lookups = NULL;
  channel->domains = NULL;
  channel->sortlist = NULL;
  channel->servers = NULL;
  channel->sock_state_cb = NULL;
  channel->sock_state_cb_data = NULL;

  channel->last_server = 0;
  channel->last_timeout_processed = (time_t)now.tv_sec;

  /* Initialize our lists of queries */
  ares__init_list_head(&(channel->all_queries));
  for (i = 0; i < ARES_QID_TABLE_SIZE; i++)
    {
      ares__init_list_head(&(channel->queries_by_qid[i]));
    }
  for (i = 0; i < ARES_TIMEOUT_TABLE_SIZE; i++)
    {
      ares__init_list_head(&(channel->queries_by_timeout[i]));
    }

  /* Initialize configuration by each of the four sources, from highest
   * precedence to lowest.
   */

  if (status == ARES_SUCCESS) {
  status = init_by_options(channel, options, optmask);
    if (status != ARES_SUCCESS)
      DEBUGF(fprintf(stderr, "Error: init_by_options failed: %s\n",
                     ares_strerror(status)));
  }
  if (status == ARES_SUCCESS) {
    status = init_by_environment(channel);
    if (status != ARES_SUCCESS)
      DEBUGF(fprintf(stderr, "Error: init_by_environment failed: %s\n",
                     ares_strerror(status)));
  }
  if (status == ARES_SUCCESS) {
    status = init_by_resolv_conf(channel);
    if (status != ARES_SUCCESS)
      DEBUGF(fprintf(stderr, "Error: init_by_resolv_conf failed: %s\n",
                     ares_strerror(status)));
  }
  if (status == ARES_SUCCESS) {
    status = init_by_defaults(channel);
    if (status != ARES_SUCCESS)
      DEBUGF(fprintf(stderr, "Error: init_by_defaults failed: %s\n",
                     ares_strerror(status)));
  }

  /* Generate random key */

  if (status == ARES_SUCCESS) {
    status = init_id_key(&channel->id_key, ARES_ID_KEY_LEN);
    if (status == ARES_SUCCESS)
      channel->next_id = ares__generate_new_id(&channel->id_key);
    else
      DEBUGF(fprintf(stderr, "Error: init_id_key failed: %s\n",
                     ares_strerror(status)));
  }

  if (status != ARES_SUCCESS)
    {
      /* Something failed; clean up memory we may have allocated. */
      if (channel->servers)
        free(channel->servers);
      if (channel->domains)
        {
          for (i = 0; i < channel->ndomains; i++)
            free(channel->domains[i]);
          free(channel->domains);
        }
      if (channel->sortlist)
        free(channel->sortlist);
      if(channel->lookups)
        free(channel->lookups);
      free(channel);
      return status;
    }

  /* Trim to one server if ARES_FLAG_PRIMARY is set. */
  if ((channel->flags & ARES_FLAG_PRIMARY) && channel->nservers > 1)
    channel->nservers = 1;

  /* Initialize server states. */
  for (i = 0; i < channel->nservers; i++)
    {
      server = &channel->servers[i];
      server->udp_socket = ARES_SOCKET_BAD;
      server->tcp_socket = ARES_SOCKET_BAD;
      server->tcp_connection_generation = ++channel->tcp_connection_generation;
      server->tcp_lenbuf_pos = 0;
      server->tcp_buffer = NULL;
      server->qhead = NULL;
      server->qtail = NULL;
      ares__init_list_head(&(server->queries_to_server));
      server->channel = channel;
      server->is_broken = 0;
    }

  *channelptr = channel;
  return ARES_SUCCESS;
}

/* Save options from initialized channel */
int ares_save_options(ares_channel channel, struct ares_options *options,
                      int *optmask)
{
  int i;

  /* Zero everything out */
  memset(options, 0, sizeof(struct ares_options));

  if (!ARES_CONFIG_CHECK(channel))
    return ARES_ENODATA;

  (*optmask) = (ARES_OPT_FLAGS|ARES_OPT_TRIES|ARES_OPT_NDOTS|
                ARES_OPT_UDP_PORT|ARES_OPT_TCP_PORT|ARES_OPT_SOCK_STATE_CB|
                ARES_OPT_SERVERS|ARES_OPT_DOMAINS|ARES_OPT_LOOKUPS|
                ARES_OPT_SORTLIST|ARES_OPT_TIMEOUTMS);

  /* Copy easy stuff */
  options->flags   = channel->flags;

  /* We return full millisecond resolution but that's only because we don't
     set the ARES_OPT_TIMEOUT anymore, only the new ARES_OPT_TIMEOUTMS */
  options->timeout = channel->timeout;
  options->tries   = channel->tries;
  options->ndots   = channel->ndots;
  options->udp_port = (unsigned short)channel->udp_port;
  options->tcp_port = (unsigned short)channel->tcp_port;
  options->sock_state_cb     = channel->sock_state_cb;
  options->sock_state_cb_data = channel->sock_state_cb_data;

  /* Copy servers */
  if (channel->nservers) {
    options->servers =
      malloc(channel->nservers * sizeof(struct server_state));
    if (!options->servers && channel->nservers != 0)
      return ARES_ENOMEM;
    for (i = 0; i < channel->nservers; i++)
      options->servers[i] = channel->servers[i].addr;
  }
  options->nservers = channel->nservers;

  /* copy domains */
  if (channel->ndomains) {
    options->domains = malloc(channel->ndomains * sizeof(char *));
    if (!options->domains)
      return ARES_ENOMEM;

    for (i = 0; i < channel->ndomains; i++)
    {
      options->ndomains = i;
      options->domains[i] = strdup(channel->domains[i]);
      if (!options->domains[i])
        return ARES_ENOMEM;
    }
  }
  options->ndomains = channel->ndomains;

  /* copy lookups */
  if (channel->lookups) {
    options->lookups = strdup(channel->lookups);
    if (!options->lookups && channel->lookups)
      return ARES_ENOMEM;
  }

  /* copy sortlist */
  if (channel->nsort) {
    options->sortlist = malloc(channel->nsort * sizeof(struct apattern));
    if (!options->sortlist)
      return ARES_ENOMEM;
    for (i = 0; i < channel->nsort; i++)
    {
      memcpy(&(options->sortlist[i]), &(channel->sortlist[i]),
             sizeof(struct apattern));
    }
  }
  options->nsort = channel->nsort;

  return ARES_SUCCESS;
}

static int init_by_options(ares_channel channel,
                           const struct ares_options *options,
                           int optmask)
{
  int i;

  /* Easy stuff. */
  if ((optmask & ARES_OPT_FLAGS) && channel->flags == -1)
    channel->flags = options->flags;
  if ((optmask & ARES_OPT_TIMEOUTMS) && channel->timeout == -1)
    channel->timeout = options->timeout;
  else if ((optmask & ARES_OPT_TIMEOUT) && channel->timeout == -1)
    channel->timeout = options->timeout * 1000;
  if ((optmask & ARES_OPT_TRIES) && channel->tries == -1)
    channel->tries = options->tries;
  if ((optmask & ARES_OPT_NDOTS) && channel->ndots == -1)
    channel->ndots = options->ndots;
  if ((optmask & ARES_OPT_ROTATE) && channel->rotate == -1)
    channel->rotate = options->rotate;
  if ((optmask & ARES_OPT_UDP_PORT) && channel->udp_port == -1)
    channel->udp_port = options->udp_port;
  if ((optmask & ARES_OPT_TCP_PORT) && channel->tcp_port == -1)
    channel->tcp_port = options->tcp_port;
  if ((optmask & ARES_OPT_SOCK_STATE_CB) && channel->sock_state_cb == NULL)
    {
      channel->sock_state_cb = options->sock_state_cb;
      channel->sock_state_cb_data = options->sock_state_cb_data;
    }
  if ((optmask & ARES_OPT_SOCK_SNDBUF)
      && channel->socket_send_buffer_size == -1)
    channel->socket_send_buffer_size = options->socket_send_buffer_size;
  if ((optmask & ARES_OPT_SOCK_RCVBUF)
      && channel->socket_receive_buffer_size == -1)
    channel->socket_receive_buffer_size = options->socket_receive_buffer_size;

  /* Copy the servers, if given. */
  if ((optmask & ARES_OPT_SERVERS) && channel->nservers == -1)
    {
      /* Avoid zero size allocations at any cost */
      if (options->nservers > 0)
        {
          channel->servers =
            malloc(options->nservers * sizeof(struct server_state));
          if (!channel->servers)
            return ARES_ENOMEM;
          for (i = 0; i < options->nservers; i++)
            channel->servers[i].addr = options->servers[i];
        }
      channel->nservers = options->nservers;
    }

  /* Copy the domains, if given.  Keep channel->ndomains consistent so
   * we can clean up in case of error.
   */
  if ((optmask & ARES_OPT_DOMAINS) && channel->ndomains == -1)
    {
      /* Avoid zero size allocations at any cost */
      if (options->ndomains > 0)
      {
        channel->domains = malloc(options->ndomains * sizeof(char *));
        if (!channel->domains)
          return ARES_ENOMEM;
        for (i = 0; i < options->ndomains; i++)
          {
            channel->ndomains = i;
            channel->domains[i] = strdup(options->domains[i]);
            if (!channel->domains[i])
              return ARES_ENOMEM;
          }
      }
      channel->ndomains = options->ndomains;
    }

  /* Set lookups, if given. */
  if ((optmask & ARES_OPT_LOOKUPS) && !channel->lookups)
    {
      channel->lookups = strdup(options->lookups);
      if (!channel->lookups)
        return ARES_ENOMEM;
    }

  /* copy sortlist */
  if ((optmask & ARES_OPT_SORTLIST) && channel->nsort == -1)
    {
      channel->sortlist = malloc(options->nsort * sizeof(struct apattern));
      if (!channel->sortlist)
        return ARES_ENOMEM;
      for (i = 0; i < options->nsort; i++)
        {
          memcpy(&(channel->sortlist[i]), &(options->sortlist[i]), sizeof(struct apattern));
        }
      channel->nsort = options->nsort;
    }

  return ARES_SUCCESS;
}

static int init_by_environment(ares_channel channel)
{
  const char *localdomain, *res_options;
  int status;

  localdomain = getenv("LOCALDOMAIN");
  if (localdomain && channel->ndomains == -1)
    {
      status = set_search(channel, localdomain);
      if (status != ARES_SUCCESS)
        return status;
    }

  res_options = getenv("RES_OPTIONS");
  if (res_options)
    {
      status = set_options(channel, res_options);
      if (status != ARES_SUCCESS)
        return status;
    }

  return ARES_SUCCESS;
}

#ifdef WIN32
/*
 * Warning: returns a dynamically allocated buffer, the user MUST
 * use free() if the function returns 1
 */
static int get_res_nt(HKEY hKey, const char *subkey, char **obuf)
{
  /* Test for the size we need */
  DWORD size = 0;
  int result;

  result = RegQueryValueEx(hKey, subkey, 0, NULL, NULL, &size);
  if ((result != ERROR_SUCCESS && result != ERROR_MORE_DATA) || !size)
    return 0;
  *obuf = malloc(size+1);
  if (!*obuf)
    return 0;

  if (RegQueryValueEx(hKey, subkey, 0, NULL,
                      (LPBYTE)*obuf, &size) != ERROR_SUCCESS)
  {
    free(*obuf);
    return 0;
  }
  if (size == 1)
  {
    free(*obuf);
    return 0;
  }
  return 1;
}

static int get_res_interfaces_nt(HKEY hKey, const char *subkey, char **obuf)
{
  char enumbuf[39]; /* GUIDs are 38 chars + 1 for NULL */
  DWORD enum_size = 39;
  int idx = 0;
  HKEY hVal;

  while (RegEnumKeyEx(hKey, idx++, enumbuf, &enum_size, 0,
                      NULL, NULL, NULL) != ERROR_NO_MORE_ITEMS)
  {
    int rc;

    enum_size = 39;
    if (RegOpenKeyEx(hKey, enumbuf, 0, KEY_QUERY_VALUE, &hVal) !=
        ERROR_SUCCESS)
      continue;
    rc = get_res_nt(hVal, subkey, obuf);
      RegCloseKey(hVal);
    if (rc)
      return 1;
    }
  return 0;
}

static int get_iphlpapi_dns_info (char *ret_buf, size_t ret_size)
{
  FIXED_INFO    *fi   = alloca (sizeof(*fi));
  DWORD          size = sizeof (*fi);
  typedef DWORD (WINAPI* get_net_param_func) (FIXED_INFO*, DWORD*);
  get_net_param_func fpGetNetworkParams;  /* available only on Win-98/2000+ */
  HMODULE        handle;
  IP_ADDR_STRING *ipAddr;
  int            i, count = 0;
  int            debug  = 0;
  size_t         ip_size = sizeof("255.255.255.255,")-1;
  size_t         left = ret_size;
  char          *ret = ret_buf;
  HRESULT        res;

  if (!fi)
     return (0);

  handle = LoadLibrary ("iphlpapi.dll");
  if (!handle)
     return (0);

  fpGetNetworkParams = (get_net_param_func) GetProcAddress (handle, "GetNetworkParams");
  if (!fpGetNetworkParams)
     goto quit;

  res = (*fpGetNetworkParams) (fi, &size);
  if ((res != ERROR_BUFFER_OVERFLOW) && (res != ERROR_SUCCESS))
     goto quit;

  fi = alloca (size);
  if (!fi || (*fpGetNetworkParams) (fi, &size) != ERROR_SUCCESS)
     goto quit;

  if (debug)
  {
    printf ("Host Name: %s\n", fi->HostName);
    printf ("Domain Name: %s\n", fi->DomainName);
    printf ("DNS Servers:\n"
            "    %s (primary)\n", fi->DnsServerList.IpAddress.String);
  }
  if (strlen(fi->DnsServerList.IpAddress.String) > 0 &&
      inet_addr(fi->DnsServerList.IpAddress.String) != INADDR_NONE &&
      left > ip_size)
  {
    ret += sprintf (ret, "%s,", fi->DnsServerList.IpAddress.String);
    left -= ret - ret_buf;
    count++;
  }

  for (i = 0, ipAddr = fi->DnsServerList.Next; ipAddr && left > ip_size;
       ipAddr = ipAddr->Next, i++)
  {
    if (inet_addr(ipAddr->IpAddress.String) != INADDR_NONE)
    {
       ret += sprintf (ret, "%s,", ipAddr->IpAddress.String);
       left -= ret - ret_buf;
       count++;
    }
    if (debug)
       printf ("    %s (secondary %d)\n", ipAddr->IpAddress.String, i+1);
  }

quit:
  if (handle)
     FreeLibrary (handle);

  if (debug && left <= ip_size)
     printf ("Too many nameservers. Truncating to %d addressess", count);
  if (ret > ret_buf)
     ret[-1] = '\0';
  return (count);
}
#endif

static int init_by_resolv_conf(ares_channel channel)
{
  char *line = NULL;
  int status = -1, nservers = 0, nsort = 0;
  struct server_state *servers = NULL;
  struct apattern *sortlist = NULL;

#ifdef WIN32

    /*
  NameServer info via IPHLPAPI (IP helper API):
    GetNetworkParams() should be the trusted source for this.
    Available in Win-98/2000 and later. If that fail, fall-back to
    registry information.

  NameServer Registry:

   On Windows 9X, the DNS server can be found in:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP\NameServer

        On Windows NT/2000/XP/2003:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\NameServer
        or
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\DhcpNameServer
        or
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\{AdapterID}\
NameServer
        or
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\{AdapterID}\
DhcpNameServer
   */

  HKEY mykey;
  HKEY subkey;
  DWORD data_type;
  DWORD bytes;
  DWORD result;
  char  buf[256];

  if (channel->nservers > -1)  /* don't override ARES_OPT_SERVER */
     return ARES_SUCCESS;

  if (get_iphlpapi_dns_info(buf,sizeof(buf)) > 0)
  {
    status = config_nameserver(&servers, &nservers, buf);
    if (status == ARES_SUCCESS)
      goto okay;
  }

  if (IS_NT())
  {
    if (RegOpenKeyEx(
          HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0,
          KEY_READ, &mykey
          ) == ERROR_SUCCESS)
    {
      RegOpenKeyEx(mykey, "Interfaces", 0,
                   KEY_QUERY_VALUE|KEY_ENUMERATE_SUB_KEYS, &subkey);
      if (get_res_nt(mykey, NAMESERVER, &line))
      {
        status = config_nameserver(&servers, &nservers, line);
        free(line);
      }
      else if (get_res_nt(mykey, DHCPNAMESERVER, &line))
      {
        status = config_nameserver(&servers, &nservers, line);
        free(line);
      }
      /* Try the interfaces */
      else if (get_res_interfaces_nt(subkey, NAMESERVER, &line))
      {
        status = config_nameserver(&servers, &nservers, line);
        free(line);
      }
      else if (get_res_interfaces_nt(subkey, DHCPNAMESERVER, &line))
      {
        status = config_nameserver(&servers, &nservers, line);
        free(line);
      }
      RegCloseKey(subkey);
      RegCloseKey(mykey);
    }
  }
  else
  {
    if (RegOpenKeyEx(
          HKEY_LOCAL_MACHINE, WIN_NS_9X, 0,
          KEY_READ, &mykey
          ) == ERROR_SUCCESS)
    {
      if ((result = RegQueryValueEx(
             mykey, NAMESERVER, NULL, &data_type,
             NULL, &bytes
             )
            ) == ERROR_SUCCESS ||
          result == ERROR_MORE_DATA)
      {
        if (bytes)
        {
          line = malloc(bytes+1);
          if (RegQueryValueEx(mykey, NAMESERVER, NULL, &data_type,
                              (unsigned char *)line, &bytes) ==
              ERROR_SUCCESS)
          {
            status = config_nameserver(&servers, &nservers, line);
          }
          free(line);
        }
      }
    }
    RegCloseKey(mykey);
  }

  if (status == ARES_SUCCESS)
    status = ARES_EOF;
  else
    /* Catch the case when all the above checks fail (which happens when there
       is no network card or the cable is unplugged) */
    status = ARES_EFILE;

#elif defined(__riscos__)

  /* Under RISC OS, name servers are listed in the
     system variable Inet$Resolvers, space separated. */

  line = getenv("Inet$Resolvers");
  status = ARES_EOF;
  if (line) {
    char *resolvers = strdup(line), *pos, *space;

    if (!resolvers)
      return ARES_ENOMEM;

    pos = resolvers;
    do {
      space = strchr(pos, ' ');
      if (space)
        *space = '\0';
      status = config_nameserver(&servers, &nservers, pos);
      if (status != ARES_SUCCESS)
        break;
      pos = space + 1;
    } while (space);

    if (status == ARES_SUCCESS)
      status = ARES_EOF;

    free(resolvers);
  }

#elif defined(WATT32)
  int i;

  sock_init();
  for (i = 0; def_nameservers[i]; i++)
      ;
  if (i == 0)
    return ARES_SUCCESS; /* use localhost DNS server */

  nservers = i;
  servers = calloc(sizeof(*servers), i);
  if (!servers)
     return ARES_ENOMEM;

  for (i = 0; def_nameservers[i]; i++)
      servers[i].addr.s_addr = htonl(def_nameservers[i]);
  status = ARES_EOF;

#else
  {
    char *p;
    FILE *fp;
    int linesize;
    int error;

    /* Don't read resolv.conf and friends if we don't have to */
    if (ARES_CONFIG_CHECK(channel))
        return ARES_SUCCESS;

    fp = fopen(PATH_RESOLV_CONF, "r");
    if (fp) {
      while ((status = ares__read_line(fp, &line, &linesize)) == ARES_SUCCESS)
      {
        if ((p = try_config(line, "domain")) && channel->ndomains == -1)
          status = config_domain(channel, p);
        else if ((p = try_config(line, "lookup")) && !channel->lookups)
          status = config_lookup(channel, p, "bind", "file");
        else if ((p = try_config(line, "search")) && channel->ndomains == -1)
          status = set_search(channel, p);
        else if ((p = try_config(line, "nameserver")) && channel->nservers == -1)
          status = config_nameserver(&servers, &nservers, p);
        else if ((p = try_config(line, "sortlist")) && channel->nsort == -1)
          status = config_sortlist(&sortlist, &nsort, p);
        else if ((p = try_config(line, "options")))
          status = set_options(channel, p);
        else
          status = ARES_SUCCESS;
        if (status != ARES_SUCCESS)
          break;
      }
      fclose(fp);
    }
    else {
      error = ERRNO;
      switch(error) {
      case ENOENT:
      case ESRCH:
        status = ARES_EOF;
        break;
      default:
        DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
                       error, strerror(error)));
        DEBUGF(fprintf(stderr, "Error opening file: %s\n", PATH_RESOLV_CONF));
        status = ARES_EFILE;
      }
    }

    if ((status == ARES_EOF) && (!channel->lookups)) {
      /* Many systems (Solaris, Linux, BSD's) use nsswitch.conf */
      fp = fopen("/etc/nsswitch.conf", "r");
      if (fp) {
        while ((status = ares__read_line(fp, &line, &linesize)) == ARES_SUCCESS)
        {
          if ((p = try_config(line, "hosts:")) && !channel->lookups)
            status = config_lookup(channel, p, "dns", "files");
        }
        fclose(fp);
      }
      else {
        error = ERRNO;
        switch(error) {
        case ENOENT:
        case ESRCH:
          status = ARES_EOF;
          break;
        default:
          DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
                         error, strerror(error)));
          DEBUGF(fprintf(stderr, "Error opening file: %s\n", "/etc/nsswitch.conf"));
          status = ARES_EFILE;
        }
      }
    }

    if ((status == ARES_EOF) && (!channel->lookups)) {
      /* Linux / GNU libc 2.x and possibly others have host.conf */
      fp = fopen("/etc/host.conf", "r");
      if (fp) {
        while ((status = ares__read_line(fp, &line, &linesize)) == ARES_SUCCESS)
        {
          if ((p = try_config(line, "order")) && !channel->lookups)
            status = config_lookup(channel, p, "bind", "hosts");
        }
        fclose(fp);
      }
      else {
        error = ERRNO;
        switch(error) {
        case ENOENT:
        case ESRCH:
          status = ARES_EOF;
          break;
        default:
          DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
                         error, strerror(error)));
          DEBUGF(fprintf(stderr, "Error opening file: %s\n", "/etc/host.conf"));
          status = ARES_EFILE;
        }
      }
    }

    if ((status == ARES_EOF) && (!channel->lookups)) {
      /* Tru64 uses /etc/svc.conf */
      fp = fopen("/etc/svc.conf", "r");
      if (fp) {
        while ((status = ares__read_line(fp, &line, &linesize)) == ARES_SUCCESS)
        {
          if ((p = try_config(line, "hosts=")) && !channel->lookups)
            status = config_lookup(channel, p, "bind", "local");
        }
        fclose(fp);
      }
      else {
        error = ERRNO;
        switch(error) {
        case ENOENT:
        case ESRCH:
          status = ARES_EOF;
          break;
        default:
          DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
                         error, strerror(error)));
          DEBUGF(fprintf(stderr, "Error opening file: %s\n", "/etc/svc.conf"));
          status = ARES_EFILE;
        }
      }
    }

    if(line)
      free(line);
  }

#endif

  /* Handle errors. */
  if (status != ARES_EOF)
    {
      if (servers != NULL)
        free(servers);
      if (sortlist != NULL)
        free(sortlist);
      return status;
    }

  /* If we got any name server entries, fill them in. */
#ifdef WIN32
okay:
#endif
  if (servers)
    {
      channel->servers = servers;
      channel->nservers = nservers;
    }

  /* If we got any sortlist entries, fill them in. */
  if (sortlist)
    {
      channel->sortlist = sortlist;
      channel->nsort = nsort;
    }

  return ARES_SUCCESS;
}

static int init_by_defaults(ares_channel channel)
{
  char *hostname = NULL;
  int rc = ARES_SUCCESS;

  if (channel->flags == -1)
    channel->flags = 0;
  if (channel->timeout == -1)
    channel->timeout = DEFAULT_TIMEOUT;
  if (channel->tries == -1)
    channel->tries = DEFAULT_TRIES;
  if (channel->ndots == -1)
    channel->ndots = 1;
  if (channel->rotate == -1)
    channel->rotate = 0;
  if (channel->udp_port == -1)
    channel->udp_port = htons(NAMESERVER_PORT);
  if (channel->tcp_port == -1)
    channel->tcp_port = htons(NAMESERVER_PORT);

  if (channel->nservers == -1) {
    /* If nobody specified servers, try a local named. */
    channel->servers = malloc(sizeof(struct server_state));
    if (!channel->servers) {
      rc = ARES_ENOMEM;
      goto error;
    }
    channel->servers[0].addr.s_addr = htonl(INADDR_LOOPBACK);
    channel->nservers = 1;
  }

#ifdef ENAMETOOLONG
#define toolong(x) (x == -1) && ((ENAMETOOLONG == errno) || (EINVAL == errno))
#else
#define toolong(x) (x == -1) && (EINVAL == errno)
#endif

  if (channel->ndomains == -1) {
    /* Derive a default domain search list from the kernel hostname,
     * or set it to empty if the hostname isn't helpful.
     */
    size_t len = 64;
    int res;

    hostname = malloc(len);
    if(!hostname) {
      rc = ARES_ENOMEM;
      goto error;
    }

    do {
      res = gethostname(hostname, len);

      if(toolong(res)) {
        char *p;
        len *= 2;
        p = realloc(hostname, len);
        if(!p) {
          rc = ARES_ENOMEM;
          goto error;
        }
        hostname = p;
        continue;
      }
      else if(res) {
        rc = ARES_EBADNAME;
        goto error;
      }

    } while(0);

    channel->ndomains = 0; /* default to none */
    if (strchr(hostname, '.'))  {
      /* a dot was found */

      channel->domains = malloc(sizeof(char *));
      if (!channel->domains) {
        rc = ARES_ENOMEM;
        goto error;
      }
      channel->domains[0] = strdup(strchr(hostname, '.') + 1);
      if (!channel->domains[0]) {
        rc = ARES_ENOMEM;
        goto error;
      }
      channel->ndomains = 1;
    }
  }

  if (channel->nsort == -1) {
    channel->sortlist = NULL;
    channel->nsort = 0;
  }

  if (!channel->lookups) {
    channel->lookups = strdup("fb");
    if (!channel->lookups)
      rc = ARES_ENOMEM;
  }

  error:
  if(rc) {
    if(channel->servers)
      free(channel->servers);

    if(channel->domains && channel->domains[0])
      free(channel->domains[0]);
    if(channel->domains)
      free(channel->domains);
    if(channel->lookups)
      free(channel->lookups);
  }

  if(hostname)
    free(hostname);

  return rc;
}

#ifndef WIN32
static int config_domain(ares_channel channel, char *str)
{
  char *q;

  /* Set a single search domain. */
  q = str;
  while (*q && !ISSPACE(*q))
    q++;
  *q = '\0';
  return set_search(channel, str);
}

static int config_lookup(ares_channel channel, const char *str,
                         const char *bindch, const char *filech)
{
  char lookups[3], *l;
  const char *p;

  /* Set the lookup order.  Only the first letter of each work
   * is relevant, and it has to be "b" for DNS or "f" for the
   * host file.  Ignore everything else.
   */
  l = lookups;
  p = str;
  while (*p)
    {
      if ((*p == *bindch || *p == *filech) && l < lookups + 2) {
        if (*p == *bindch) *l++ = 'b';
        else *l++ = 'f';
      }
      while (*p && !ISSPACE(*p) && (*p != ','))
        p++;
      while (*p && (ISSPACE(*p) || (*p == ',')))
        p++;
    }
  *l = '\0';
  channel->lookups = strdup(lookups);
  return (channel->lookups) ? ARES_SUCCESS : ARES_ENOMEM;
}

#endif

static int config_nameserver(struct server_state **servers, int *nservers,
                             char *str)
{
  struct in_addr addr;
  struct server_state *newserv;
  /* On Windows, there may be more than one nameserver specified in the same
   * registry key, so we parse it as a space or comma seperated list.
   */
#ifdef WIN32
  char *p = str;
  char *begin = str;
  int more = 1;
  while (more)
  {
    more = 0;
    while (*p && !ISSPACE(*p) && *p != ',')
      p++;

    if (*p)
    {
      *p = '\0';
      more = 1;
    }

    /* Skip multiple spaces or trailing spaces */
    if (!*begin)
    {
      begin = ++p;
      continue;
    }

    /* This is the part that actually sets the nameserver */
    addr.s_addr = inet_addr(begin);
    if (addr.s_addr == INADDR_NONE)
      continue;
    newserv = realloc(*servers, (*nservers + 1) * sizeof(struct server_state));
    if (!newserv)
      return ARES_ENOMEM;
    newserv[*nservers].addr = addr;
    *servers = newserv;
    (*nservers)++;

    if (!more)
      break;
    begin = ++p;
  }
#else
  /* Add a nameserver entry, if this is a valid address. */
  addr.s_addr = inet_addr(str);
  if (addr.s_addr == INADDR_NONE)
    return ARES_SUCCESS;
  newserv = realloc(*servers, (*nservers + 1) * sizeof(struct server_state));
  if (!newserv)
    return ARES_ENOMEM;
  newserv[*nservers].addr = addr;
  *servers = newserv;
  (*nservers)++;
#endif
  return ARES_SUCCESS;
}

#ifndef WIN32
static int config_sortlist(struct apattern **sortlist, int *nsort,
                           const char *str)
{
  struct apattern pat;
  const char *q;

  /* Add sortlist entries. */
  while (*str && *str != ';')
    {
      int bits;
      char ipbuf[16], ipbufpfx[32];
      /* Find just the IP */
      q = str;
      while (*q && *q != '/' && *q != ';' && !ISSPACE(*q))
        q++;
      memcpy(ipbuf, str, (int)(q-str));
      ipbuf[(int)(q-str)] = '\0';
      /* Find the prefix */
      if (*q == '/')
        {
          const char *str2 = q+1;
          while (*q && *q != ';' && !ISSPACE(*q))
            q++;
          memcpy(ipbufpfx, str, (int)(q-str));
          ipbufpfx[(int)(q-str)] = '\0';
          str = str2;
        }
      else
        ipbufpfx[0] = '\0';
      /* Lets see if it is CIDR */
      /* First we'll try IPv6 */
      if ((bits = ares_inet_net_pton(AF_INET6, ipbufpfx[0] ? ipbufpfx : ipbuf,
                                     &pat.addr.addr6,
                                     sizeof(pat.addr.addr6))) > 0)
        {
          pat.type = PATTERN_CIDR;
          pat.mask.bits = (unsigned short)bits;
          pat.family = AF_INET6;
          if (!sortlist_alloc(sortlist, nsort, &pat))
            return ARES_ENOMEM;
        }
      if (ipbufpfx[0] &&
          (bits = ares_inet_net_pton(AF_INET, ipbufpfx, &pat.addr.addr4,
                                     sizeof(pat.addr.addr4))) > 0)
        {
          pat.type = PATTERN_CIDR;
          pat.mask.bits = (unsigned short)bits;
          pat.family = AF_INET;
          if (!sortlist_alloc(sortlist, nsort, &pat))
            return ARES_ENOMEM;
        }
      /* See if it is just a regular IP */
      else if (ip_addr(ipbuf, (int)(q-str), &pat.addr.addr4) == 0)
        {
          if (ipbufpfx[0])
            {
              memcpy(ipbuf, str, (int)(q-str));
              ipbuf[(int)(q-str)] = '\0';
              if (ip_addr(ipbuf, (int)(q - str), &pat.mask.addr.addr4) != 0)
                natural_mask(&pat);
            }
          else
            natural_mask(&pat);
          pat.family = AF_INET;
          pat.type = PATTERN_MASK;
          if (!sortlist_alloc(sortlist, nsort, &pat))
            return ARES_ENOMEM;
        }
      else
        {
          while (*q && *q != ';' && !ISSPACE(*q))
            q++;
        }
      str = q;
      while (ISSPACE(*str))
        str++;
    }

  return ARES_SUCCESS;
}
#endif

static int set_search(ares_channel channel, const char *str)
{
  int n;
  const char *p, *q;

  if(channel->ndomains != -1) {
    /* if we already have some domains present, free them first */
    for(n=0; n < channel->ndomains; n++)
      free(channel->domains[n]);
    free(channel->domains);
    channel->domains = NULL;
    channel->ndomains = -1;
  }

  /* Count the domains given. */
  n = 0;
  p = str;
  while (*p)
    {
      while (*p && !ISSPACE(*p))
        p++;
      while (ISSPACE(*p))
        p++;
      n++;
    }

  if (!n)
    {
      channel->ndomains = 0;
      return ARES_SUCCESS;
    }

  channel->domains = malloc(n * sizeof(char *));
  if (!channel->domains)
    return ARES_ENOMEM;

  /* Now copy the domains. */
  n = 0;
  p = str;
  while (*p)
    {
      channel->ndomains = n;
      q = p;
      while (*q && !ISSPACE(*q))
        q++;
      channel->domains[n] = malloc(q - p + 1);
      if (!channel->domains[n])
        return ARES_ENOMEM;
      memcpy(channel->domains[n], p, q - p);
      channel->domains[n][q - p] = 0;
      p = q;
      while (ISSPACE(*p))
        p++;
      n++;
    }
  channel->ndomains = n;

  return ARES_SUCCESS;
}

static int set_options(ares_channel channel, const char *str)
{
  const char *p, *q, *val;

  p = str;
  while (*p)
    {
      q = p;
      while (*q && !ISSPACE(*q))
        q++;
      val = try_option(p, q, "ndots:");
      if (val && channel->ndots == -1)
        channel->ndots = atoi(val);
      val = try_option(p, q, "retrans:");
      if (val && channel->timeout == -1)
        channel->timeout = atoi(val);
      val = try_option(p, q, "retry:");
      if (val && channel->tries == -1)
        channel->tries = atoi(val);
      val = try_option(p, q, "rotate");
      if (val && channel->rotate == -1)
        channel->rotate = 1;
      p = q;
      while (ISSPACE(*p))
        p++;
    }

  return ARES_SUCCESS;
}

#ifndef WIN32
static char *try_config(char *s, const char *opt)
{
  size_t len;
  ssize_t i;
  ssize_t j;
  char *p;

  if (!s || !opt)
    /* no line or no option */
    return NULL;

  /* trim line comment */
  for (i = 0; s[i] && s[i] != '#'; ++i);
  s[i] = '\0';

  /* trim trailing whitespace */
  for (j = i-1; j >= 0 && ISSPACE(s[j]); --j);
  s[++j] = '\0';

  /* skip leading whitespace */
  for (i = 0; s[i] && ISSPACE(s[i]); ++i);
  p = &s[i];

  if (!*p)
    /* empty line */
    return NULL;

  if ((len = strlen(opt)) == 0)
    /* empty option */
    return NULL;

  if (strncmp(p, opt, len) != 0)
    /* line and option do not match */
    return NULL;

  /* skip over given option name */
  p += len;

  if (!*p)
    /* no option value */
    return NULL;

  if ((opt[len-1] != ':') && (opt[len-1] != '=') && !ISSPACE(*p))
    /* whitespace between option name and value is mandatory
       for given option names which do not end with ':' or '=' */
    return NULL;

  /* skip over whitespace */
  while (*p && ISSPACE(*p))
    p++;

  if (!*p)
    /* no option value */
    return NULL;

  /* return pointer to option value */
  return p;
}
#endif

static const char *try_option(const char *p, const char *q, const char *opt)
{
  size_t len = strlen(opt);
  return ((size_t)(q - p) >= len && !strncmp(p, opt, len)) ? &p[len] : NULL;
}

#ifndef WIN32
static int sortlist_alloc(struct apattern **sortlist, int *nsort,
                          struct apattern *pat)
{
  struct apattern *newsort;
  newsort = realloc(*sortlist, (*nsort + 1) * sizeof(struct apattern));
  if (!newsort)
    return 0;
  newsort[*nsort] = *pat;
  *sortlist = newsort;
  (*nsort)++;
  return 1;
}

static int ip_addr(const char *ipbuf, int len, struct in_addr *addr)
{

  /* Four octets and three periods yields at most 15 characters. */
  if (len > 15)
    return -1;

  addr->s_addr = inet_addr(ipbuf);
  if (addr->s_addr == INADDR_NONE && strcmp(ipbuf, "255.255.255.255") != 0)
    return -1;
  return 0;
}

static void natural_mask(struct apattern *pat)
{
  struct in_addr addr;

  /* Store a host-byte-order copy of pat in a struct in_addr.  Icky,
   * but portable.
   */
  addr.s_addr = ntohl(pat->addr.addr4.s_addr);

  /* This is out of date in the CIDR world, but some people might
   * still rely on it.
   */
  if (IN_CLASSA(addr.s_addr))
    pat->mask.addr.addr4.s_addr = htonl(IN_CLASSA_NET);
  else if (IN_CLASSB(addr.s_addr))
    pat->mask.addr.addr4.s_addr = htonl(IN_CLASSB_NET);
  else
    pat->mask.addr.addr4.s_addr = htonl(IN_CLASSC_NET);
}
#endif
/* initialize an rc4 key. If possible a cryptographically secure random key
   is generated using a suitable function (for example win32's RtlGenRandom as
   described in
   http://blogs.msdn.com/michael_howard/archive/2005/01/14/353379.aspx
   otherwise the code defaults to cross-platform albeit less secure mechanism
   using rand
*/
static void randomize_key(unsigned char* key,int key_data_len)
{
  int randomized = 0;
  int counter=0;
#ifdef WIN32
  HMODULE lib=LoadLibrary("ADVAPI32.DLL");
  if (lib) {
    BOOLEAN (APIENTRY *pfn)(void*, ULONG) =
      (BOOLEAN (APIENTRY *)(void*,ULONG))GetProcAddress(lib,"SystemFunction036");
    if (pfn && pfn(key,key_data_len) )
      randomized = 1;

    FreeLibrary(lib);
  }
#else /* !WIN32 */
#ifdef RANDOM_FILE
  FILE *f = fopen(RANDOM_FILE, "rb");
  if(f) {
    counter = fread(key, 1, key_data_len, f);
    fclose(f);
  }
#endif
#endif /* WIN32 */

  if ( !randomized ) {
    for (;counter<key_data_len;counter++)
      key[counter]=(unsigned char)(rand() % 256);
  }
}

static int init_id_key(rc4_key* key,int key_data_len)
{
  unsigned char index1;
  unsigned char index2;
  unsigned char* state;
  short counter;
  unsigned char *key_data_ptr = 0;

  key_data_ptr = calloc(1,key_data_len);
  if (!key_data_ptr)
    return ARES_ENOMEM;

  state = &key->state[0];
  for(counter = 0; counter < 256; counter++)
    /* unnecessary AND but it keeps some compilers happier */
    state[counter] = (unsigned char)(counter & 0xff);
  randomize_key(key->state,key_data_len);
  key->x = 0;
  key->y = 0;
  index1 = 0;
  index2 = 0;
  for(counter = 0; counter < 256; counter++)
  {
    index2 = (unsigned char)((key_data_ptr[index1] + state[counter] +
                              index2) % 256);
    ARES_SWAP_BYTE(&state[counter], &state[index2]);

    index1 = (unsigned char)((index1 + 1) % key_data_len);
  }
  free(key_data_ptr);
  return ARES_SUCCESS;
}

unsigned short ares__generate_new_id(rc4_key* key)
{
  unsigned short r=0;
  ares__rc4(key, (unsigned char *)&r, sizeof(r));
  return r;
}