Adding upstream version 14.2.21.upstream/14.2.21upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2158 insertions, 0 deletions

diff --git a/src/c-ares/ares_init.c b/src/c-ares/ares_init.c
new file mode 100644
index 00000000..3811a915
--- /dev/null
+++ b/src/c-ares/ares_init.c
@@ -0,0 +1,2158 @@
+
+/* Copyright 1998 by the Massachusetts Institute of Technology.
+ * Copyright (C) 2007-2013 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 "ares_setup.h"
+
+#ifdef HAVE_SYS_PARAM_H
+#include <sys/param.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
+
+#if defined(ANDROID) || defined(__ANDROID__)
+#include <sys/system_properties.h>
+/* From the Bionic sources */
+#define DNS_PROP_NAME_PREFIX  "net.dns"
+#define MAX_DNS_PROPERTIES    8
+#endif
+
+#if defined(CARES_USE_LIBRESOLV)
+#include <resolv.h>
+#endif
+
+#include "ares.h"
+#include "ares_inet_net_pton.h"
+#include "ares_library_init.h"
+#include "ares_nowarn.h"
+#include "ares_platform.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);
+
+#ifndef WATT32
+static int config_nameserver(struct server_state **servers, int *nservers,
+                             char *str);
+#endif
+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);
+
+static int config_sortlist(struct apattern **sortlist, int *nsort,
+                           const char *str);
+static int sortlist_alloc(struct apattern **sortlist, int *nsort,
+                          struct apattern *pat);
+static int ip_addr(const char *s, ssize_t len, struct in_addr *addr);
+static void natural_mask(struct apattern *pat);
+#if !defined(WIN32) && !defined(WATT32) && \
+    !defined(ANDROID) && !defined(__ANDROID__) && !defined(CARES_USE_LIBRESOLV)
+static int config_domain(ares_channel channel, char *str);
+static int config_lookup(ares_channel channel, const char *str,
+                         const char *bindch, const char *altbindch,
+                         const char *filech);
+static char *try_config(char *s, const char *opt, char scc);
+#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 timeval now;
+
+#ifdef CURLDEBUG
+  const char *env = getenv("CARES_MEMDEBUG");
+
+  if (env)
+    curl_memdebug(env);
+  env = getenv("CARES_MEMLIMIT");
+  if (env) {
+    char *endptr;
+    long num = strtol(env, &endptr, 10);
+    if((endptr != env) && (endptr == env + strlen(env)) && (num > 0))
+      curl_memlimit(num);
+  }
+#endif
+
+  if (ares_library_initialized() != ARES_SUCCESS)
+    return ARES_ENOTINITIALIZED;  /* LCOV_EXCL_LINE: n/a on non-WinSock */
+
+  channel = ares_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->ednspsz = -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->sock_create_cb = NULL;
+  channel->sock_create_cb_data = NULL;
+  channel->sock_config_cb = NULL;
+  channel->sock_config_cb_data = NULL;
+  channel->sock_funcs = NULL;
+  channel->sock_func_cb_data = NULL;
+
+  channel->last_server = 0;
+  channel->last_timeout_processed = (time_t)now.tv_sec;
+
+  memset(&channel->local_dev_name, 0, sizeof(channel->local_dev_name));
+  channel->local_ip4 = 0;
+  memset(&channel->local_ip6, 0, sizeof(channel->local_ip6));
+
+  /* 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.
+   */
+
+  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 we fail to apply user-specified options, fail the whole init process */
+    goto done;
+  }
+  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)));
+  }
+
+  /*
+   * No matter what failed or succeeded, seed defaults to provide
+   * useful behavior for things that we missed.
+   */
+  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)));
+  }
+
+done:
+  if (status != ARES_SUCCESS)
+    {
+      /* Something failed; clean up memory we may have allocated. */
+      if (channel->servers)
+        ares_free(channel->servers);
+      if (channel->domains)
+        {
+          for (i = 0; i < channel->ndomains; i++)
+            ares_free(channel->domains[i]);
+          ares_free(channel->domains);
+        }
+      if (channel->sortlist)
+        ares_free(channel->sortlist);
+      if(channel->lookups)
+        ares_free(channel->lookups);
+      ares_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;
+
+  ares__init_servers_state(channel);
+
+  *channelptr = channel;
+  return ARES_SUCCESS;
+}
+
+/* ares_dup() duplicates a channel handle with all its options and returns a
+   new channel handle */
+int ares_dup(ares_channel *dest, ares_channel src)
+{
+  struct ares_options opts;
+  struct ares_addr_port_node *servers;
+  int non_v4_default_port = 0;
+  int i, rc;
+  int optmask;
+
+  *dest = NULL; /* in case of failure return NULL explicitly */
+
+  /* First get the options supported by the old ares_save_options() function,
+     which is most of them */
+  rc = ares_save_options(src, &opts, &optmask);
+  if(rc)
+  {
+    ares_destroy_options(&opts);
+    return rc;
+  }
+
+  /* Then create the new channel with those options */
+  rc = ares_init_options(dest, &opts, optmask);
+
+  /* destroy the options copy to not leak any memory */
+  ares_destroy_options(&opts);
+
+  if(rc)
+    return rc;
+
+  /* Now clone the options that ares_save_options() doesn't support. */
+  (*dest)->sock_create_cb      = src->sock_create_cb;
+  (*dest)->sock_create_cb_data = src->sock_create_cb_data;
+  (*dest)->sock_config_cb      = src->sock_config_cb;
+  (*dest)->sock_config_cb_data = src->sock_config_cb_data;
+  (*dest)->sock_funcs          = src->sock_funcs;
+  (*dest)->sock_func_cb_data   = src->sock_func_cb_data;
+
+  strncpy((*dest)->local_dev_name, src->local_dev_name,
+          sizeof(src->local_dev_name));
+  (*dest)->local_ip4 = src->local_ip4;
+  memcpy((*dest)->local_ip6, src->local_ip6, sizeof(src->local_ip6));
+
+  /* Full name server cloning required if there is a non-IPv4, or non-default port, nameserver */
+  for (i = 0; i < src->nservers; i++)
+    {
+      if ((src->servers[i].addr.family != AF_INET) ||
+          (src->servers[i].addr.udp_port != 0) ||
+          (src->servers[i].addr.tcp_port != 0)) {
+        non_v4_default_port++;
+        break;
+      }
+    }
+  if (non_v4_default_port) {
+    rc = ares_get_servers_ports(src, &servers);
+    if (rc != ARES_SUCCESS) {
+      ares_destroy(*dest);
+      *dest = NULL;
+      return rc;
+    }
+    rc = ares_set_servers_ports(*dest, servers);
+    ares_free_data(servers);
+    if (rc != ARES_SUCCESS) {
+      ares_destroy(*dest);
+      *dest = NULL;
+      return rc;
+    }
+  }
+
+  return ARES_SUCCESS; /* everything went fine */
+}
+
+/* Save options from initialized channel */
+int ares_save_options(ares_channel channel, struct ares_options *options,
+                      int *optmask)
+{
+  int i, j;
+  int ipv4_nservers = 0;
+
+  /* Zero everything out */
+  memset(options, 0, sizeof(struct ares_options));
+
+  if (!ARES_CONFIG_CHECK(channel))
+    return ARES_ENODATA;
+
+  /* Traditionally the optmask wasn't saved in the channel struct so it was
+     recreated here. ROTATE is the first option that has no struct field of
+     its own in the public config struct */
+  (*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);
+  (*optmask) |= (channel->rotate ? ARES_OPT_ROTATE : ARES_OPT_NOROTATE);
+
+  /* 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 = ntohs(aresx_sitous(channel->udp_port));
+  options->tcp_port = ntohs(aresx_sitous(channel->tcp_port));
+  options->sock_state_cb     = channel->sock_state_cb;
+  options->sock_state_cb_data = channel->sock_state_cb_data;
+
+  /* Copy IPv4 servers that use the default port */
+  if (channel->nservers) {
+    for (i = 0; i < channel->nservers; i++)
+    {
+      if ((channel->servers[i].addr.family == AF_INET) &&
+          (channel->servers[i].addr.udp_port == 0) &&
+          (channel->servers[i].addr.tcp_port == 0))
+        ipv4_nservers++;
+    }
+    if (ipv4_nservers) {
+      options->servers = ares_malloc(ipv4_nservers * sizeof(struct in_addr));
+      if (!options->servers)
+        return ARES_ENOMEM;
+      for (i = j = 0; i < channel->nservers; i++)
+      {
+        if ((channel->servers[i].addr.family == AF_INET) &&
+            (channel->servers[i].addr.udp_port == 0) &&
+            (channel->servers[i].addr.tcp_port == 0))
+          memcpy(&options->servers[j++],
+                 &channel->servers[i].addr.addrV4,
+                 sizeof(channel->servers[i].addr.addrV4));
+      }
+    }
+  }
+  options->nservers = ipv4_nservers;
+
+  /* copy domains */
+  if (channel->ndomains) {
+    options->domains = ares_malloc(channel->ndomains * sizeof(char *));
+    if (!options->domains)
+      return ARES_ENOMEM;
+
+    for (i = 0; i < channel->ndomains; i++)
+    {
+      options->ndomains = i;
+      options->domains[i] = ares_strdup(channel->domains[i]);
+      if (!options->domains[i])
+        return ARES_ENOMEM;
+    }
+  }
+  options->ndomains = channel->ndomains;
+
+  /* copy lookups */
+  if (channel->lookups) {
+    options->lookups = ares_strdup(channel->lookups);
+    if (!options->lookups && channel->lookups)
+      return ARES_ENOMEM;
+  }
+
+  /* copy sortlist */
+  if (channel->nsort) {
+    options->sortlist = ares_malloc(channel->nsort * sizeof(struct apattern));
+    if (!options->sortlist)
+      return ARES_ENOMEM;
+    for (i = 0; i < channel->nsort; i++)
+      options->sortlist[i] = channel->sortlist[i];
+  }
+  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 = 1;
+  if ((optmask & ARES_OPT_NOROTATE) && channel->rotate == -1)
+    channel->rotate = 0;
+  if ((optmask & ARES_OPT_UDP_PORT) && channel->udp_port == -1)
+    channel->udp_port = htons(options->udp_port);
+  if ((optmask & ARES_OPT_TCP_PORT) && channel->tcp_port == -1)
+    channel->tcp_port = htons(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;
+
+  if ((optmask & ARES_OPT_EDNSPSZ) && channel->ednspsz == -1)
+    channel->ednspsz = options->ednspsz;
+
+  /* Copy the IPv4 servers, if given. */
+  if ((optmask & ARES_OPT_SERVERS) && channel->nservers == -1)
+    {
+      /* Avoid zero size allocations at any cost */
+      if (options->nservers > 0)
+        {
+          channel->servers =
+            ares_malloc(options->nservers * sizeof(struct server_state));
+          if (!channel->servers)
+            return ARES_ENOMEM;
+          for (i = 0; i < options->nservers; i++)
+            {
+              channel->servers[i].addr.family = AF_INET;
+              channel->servers[i].addr.udp_port = 0;
+              channel->servers[i].addr.tcp_port = 0;
+              memcpy(&channel->servers[i].addr.addrV4,
+                     &options->servers[i],
+                     sizeof(channel->servers[i].addr.addrV4));
+            }
+        }
+      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 = ares_malloc(options->ndomains * sizeof(char *));
+        if (!channel->domains)
+          return ARES_ENOMEM;
+        for (i = 0; i < options->ndomains; i++)
+          {
+            channel->ndomains = i;
+            channel->domains[i] = ares_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 = ares_strdup(options->lookups);
+      if (!channel->lookups)
+        return ARES_ENOMEM;
+    }
+
+  /* copy sortlist */
+  if ((optmask & ARES_OPT_SORTLIST) && (channel->nsort == -1)) {
+    if (options->nsort > 0) {
+      channel->sortlist = ares_malloc(options->nsort * sizeof(struct apattern));
+      if (!channel->sortlist)
+        return ARES_ENOMEM;
+      for (i = 0; i < options->nsort; i++)
+        channel->sortlist[i] = options->sortlist[i];
+    }
+    channel->nsort = options->nsort;
+  }
+
+  channel->optmask = optmask;
+
+  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;  /* LCOV_EXCL_LINE: set_options() never fails */
+    }
+
+  return ARES_SUCCESS;
+}
+
+#ifdef WIN32
+/*
+ * get_REG_SZ()
+ *
+ * Given a 'hKey' handle to an open registry key and a 'leafKeyName' pointer
+ * to the name of the registry leaf key to be queried, fetch it's string
+ * value and return a pointer in *outptr to a newly allocated memory area
+ * holding it as a null-terminated string.
+ *
+ * Returns 0 and nullifies *outptr upon inability to return a string value.
+ *
+ * Returns 1 and sets *outptr when returning a dynamically allocated string.
+ *
+ * Supported on Windows NT 3.5 and newer.
+ */
+static int get_REG_SZ(HKEY hKey, const char *leafKeyName, char **outptr)
+{
+  DWORD size = 0;
+  int   res;
+
+  *outptr = NULL;
+
+  /* Find out size of string stored in registry */
+  res = RegQueryValueEx(hKey, leafKeyName, 0, NULL, NULL, &size);
+  if ((res != ERROR_SUCCESS && res != ERROR_MORE_DATA) || !size)
+    return 0;
+
+  /* Allocate buffer of indicated size plus one given that string
+     might have been stored without null termination */
+  *outptr = ares_malloc(size+1);
+  if (!*outptr)
+    return 0;
+
+  /* Get the value for real */
+  res = RegQueryValueEx(hKey, leafKeyName, 0, NULL,
+                        (unsigned char *)*outptr, &size);
+  if ((res != ERROR_SUCCESS) || (size == 1))
+  {
+    ares_free(*outptr);
+    *outptr = NULL;
+    return 0;
+  }
+
+  /* Null terminate buffer allways */
+  *(*outptr + size) = '\0';
+
+  return 1;
+}
+
+/*
+ * get_REG_SZ_9X()
+ *
+ * Functionally identical to get_REG_SZ()
+ *
+ * Supported on Windows 95, 98 and ME.
+ */
+static int get_REG_SZ_9X(HKEY hKey, const char *leafKeyName, char **outptr)
+{
+  DWORD dataType = 0;
+  DWORD size = 0;
+  int   res;
+
+  *outptr = NULL;
+
+  /* Find out size of string stored in registry */
+  res = RegQueryValueEx(hKey, leafKeyName, 0, &dataType, NULL, &size);
+  if ((res != ERROR_SUCCESS && res != ERROR_MORE_DATA) || !size)
+    return 0;
+
+  /* Allocate buffer of indicated size plus one given that string
+     might have been stored without null termination */
+  *outptr = ares_malloc(size+1);
+  if (!*outptr)
+    return 0;
+
+  /* Get the value for real */
+  res = RegQueryValueEx(hKey, leafKeyName, 0, &dataType,
+                        (unsigned char *)*outptr, &size);
+  if ((res != ERROR_SUCCESS) || (size == 1))
+  {
+    ares_free(*outptr);
+    *outptr = NULL;
+    return 0;
+  }
+
+  /* Null terminate buffer allways */
+  *(*outptr + size) = '\0';
+
+  return 1;
+}
+
+/*
+ * get_enum_REG_SZ()
+ *
+ * Given a 'hKeyParent' handle to an open registry key and a 'leafKeyName'
+ * pointer to the name of the registry leaf key to be queried, parent key
+ * is enumerated searching in child keys for given leaf key name and its
+ * associated string value. When located, this returns a pointer in *outptr
+ * to a newly allocated memory area holding it as a null-terminated string.
+ *
+ * Returns 0 and nullifies *outptr upon inability to return a string value.
+ *
+ * Returns 1 and sets *outptr when returning a dynamically allocated string.
+ *
+ * Supported on Windows NT 3.5 and newer.
+ */
+static int get_enum_REG_SZ(HKEY hKeyParent, const char *leafKeyName,
+                           char **outptr)
+{
+  char  enumKeyName[256];
+  DWORD enumKeyNameBuffSize;
+  DWORD enumKeyIdx = 0;
+  HKEY  hKeyEnum;
+  int   gotString;
+  int   res;
+
+  *outptr = NULL;
+
+  for(;;)
+  {
+    enumKeyNameBuffSize = sizeof(enumKeyName);
+    res = RegEnumKeyEx(hKeyParent, enumKeyIdx++, enumKeyName,
+                       &enumKeyNameBuffSize, 0, NULL, NULL, NULL);
+    if (res != ERROR_SUCCESS)
+      break;
+    res = RegOpenKeyEx(hKeyParent, enumKeyName, 0, KEY_QUERY_VALUE,
+                       &hKeyEnum);
+    if (res != ERROR_SUCCESS)
+      continue;
+    gotString = get_REG_SZ(hKeyEnum, leafKeyName, outptr);
+    RegCloseKey(hKeyEnum);
+    if (gotString)
+      break;
+  }
+
+  if (!*outptr)
+    return 0;
+
+  return 1;
+}
+
+/*
+ * get_DNS_Registry_9X()
+ *
+ * Functionally identical to get_DNS_Registry()
+ *
+ * Implementation supports Windows 95, 98 and ME.
+ */
+static int get_DNS_Registry_9X(char **outptr)
+{
+  HKEY hKey_VxD_MStcp;
+  int  gotString;
+  int  res;
+
+  *outptr = NULL;
+
+  res = RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_9X, 0, KEY_READ,
+                     &hKey_VxD_MStcp);
+  if (res != ERROR_SUCCESS)
+    return 0;
+
+  gotString = get_REG_SZ_9X(hKey_VxD_MStcp, NAMESERVER, outptr);
+  RegCloseKey(hKey_VxD_MStcp);
+
+  if (!gotString || !*outptr)
+    return 0;
+
+  return 1;
+}
+
+/*
+ * get_DNS_Registry_NT()
+ *
+ * Functionally identical to get_DNS_Registry()
+ *
+ * Refs: Microsoft Knowledge Base articles KB120642 and KB314053.
+ *
+ * Implementation supports Windows NT 3.5 and newer.
+ */
+static int get_DNS_Registry_NT(char **outptr)
+{
+  HKEY hKey_Interfaces = NULL;
+  HKEY hKey_Tcpip_Parameters;
+  int  gotString;
+  int  res;
+
+  *outptr = NULL;
+
+  res = RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ,
+                     &hKey_Tcpip_Parameters);
+  if (res != ERROR_SUCCESS)
+    return 0;
+
+  /*
+  ** Global DNS settings override adapter specific parameters when both
+  ** are set. Additionally static DNS settings override DHCP-configured
+  ** parameters when both are set.
+  */
+
+  /* Global DNS static parameters */
+  gotString = get_REG_SZ(hKey_Tcpip_Parameters, NAMESERVER, outptr);
+  if (gotString)
+    goto done;
+
+  /* Global DNS DHCP-configured parameters */
+  gotString = get_REG_SZ(hKey_Tcpip_Parameters, DHCPNAMESERVER, outptr);
+  if (gotString)
+    goto done;
+
+  /* Try adapter specific parameters */
+  res = RegOpenKeyEx(hKey_Tcpip_Parameters, "Interfaces", 0,
+                     KEY_QUERY_VALUE | KEY_ENUMERATE_SUB_KEYS,
+                     &hKey_Interfaces);
+  if (res != ERROR_SUCCESS)
+  {
+    hKey_Interfaces = NULL;
+    goto done;
+  }
+
+  /* Adapter specific DNS static parameters */
+  gotString = get_enum_REG_SZ(hKey_Interfaces, NAMESERVER, outptr);
+  if (gotString)
+    goto done;
+
+  /* Adapter specific DNS DHCP-configured parameters */
+  gotString = get_enum_REG_SZ(hKey_Interfaces, DHCPNAMESERVER, outptr);
+
+done:
+  if (hKey_Interfaces)
+    RegCloseKey(hKey_Interfaces);
+
+  RegCloseKey(hKey_Tcpip_Parameters);
+
+  if (!gotString || !*outptr)
+    return 0;
+
+  return 1;
+}
+
+/*
+ * get_DNS_Registry()
+ *
+ * Locates DNS info in the registry. When located, this returns a pointer
+ * in *outptr to a newly allocated memory area holding a null-terminated
+ * string with a space or comma seperated list of DNS IP addresses.
+ *
+ * Returns 0 and nullifies *outptr upon inability to return DNSes string.
+ *
+ * Returns 1 and sets *outptr when returning a dynamically allocated string.
+ */
+static int get_DNS_Registry(char **outptr)
+{
+  win_platform platform;
+  int gotString = 0;
+
+  *outptr = NULL;
+
+  platform = ares__getplatform();
+
+  if (platform == WIN_NT)
+    gotString = get_DNS_Registry_NT(outptr);
+  else if (platform == WIN_9X)
+    gotString = get_DNS_Registry_9X(outptr);
+
+  if (!gotString)
+    return 0;
+
+  return 1;
+}
+
+/*
+ * commajoin()
+ *
+ * RTF code.
+ */
+static void commajoin(char **dst, const char *src)
+{
+  char *tmp;
+
+  if (*dst)
+  {
+    tmp = ares_malloc(strlen(*dst) + strlen(src) + 2);
+    if (!tmp)
+      return;
+    sprintf(tmp, "%s,%s", *dst, src);
+    ares_free(*dst);
+    *dst = tmp;
+  }
+  else
+  {
+    *dst = ares_malloc(strlen(src) + 1);
+    if (!*dst)
+      return;
+    strcpy(*dst, src);
+  }
+}
+
+/*
+ * get_DNS_NetworkParams()
+ *
+ * Locates DNS info using GetNetworkParams() function from the Internet
+ * Protocol Helper (IP Helper) API. When located, this returns a pointer
+ * in *outptr to a newly allocated memory area holding a null-terminated
+ * string with a space or comma seperated list of DNS IP addresses.
+ *
+ * Returns 0 and nullifies *outptr upon inability to return DNSes string.
+ *
+ * Returns 1 and sets *outptr when returning a dynamically allocated string.
+ *
+ * Implementation supports Windows 98 and newer.
+ *
+ * Note: Ancient PSDK required in order to build a W98 target.
+ */
+static int get_DNS_NetworkParams(char **outptr)
+{
+  FIXED_INFO       *fi, *newfi;
+  struct ares_addr namesrvr;
+  char             *txtaddr;
+  IP_ADDR_STRING   *ipAddr;
+  int              res;
+  DWORD            size = sizeof (*fi);
+
+  *outptr = NULL;
+
+  /* Verify run-time availability of GetNetworkParams() */
+  if (ares_fpGetNetworkParams == ZERO_NULL)
+    return 0;
+
+  fi = ares_malloc(size);
+  if (!fi)
+    return 0;
+
+  res = (*ares_fpGetNetworkParams) (fi, &size);
+  if ((res != ERROR_BUFFER_OVERFLOW) && (res != ERROR_SUCCESS))
+    goto done;
+
+  newfi = ares_realloc(fi, size);
+  if (!newfi)
+    goto done;
+
+  fi = newfi;
+  res = (*ares_fpGetNetworkParams) (fi, &size);
+  if (res != ERROR_SUCCESS)
+    goto done;
+
+  for (ipAddr = &fi->DnsServerList; ipAddr; ipAddr = ipAddr->Next)
+  {
+    txtaddr = &ipAddr->IpAddress.String[0];
+
+    /* Validate converting textual address to binary format. */
+    if (ares_inet_pton(AF_INET, txtaddr, &namesrvr.addrV4) == 1)
+    {
+      if ((namesrvr.addrV4.S_un.S_addr == INADDR_ANY) ||
+          (namesrvr.addrV4.S_un.S_addr == INADDR_NONE))
+        continue;
+    }
+    else if (ares_inet_pton(AF_INET6, txtaddr, &namesrvr.addrV6) == 1)
+    {
+      if (memcmp(&namesrvr.addrV6, &ares_in6addr_any,
+                 sizeof(namesrvr.addrV6)) == 0)
+        continue;
+    }
+    else
+      continue;
+
+    commajoin(outptr, txtaddr);
+
+    if (!*outptr)
+      break;
+  }
+
+done:
+  if (fi)
+    ares_free(fi);
+
+  if (!*outptr)
+    return 0;
+
+  return 1;
+}
+
+/*
+ * get_DNS_AdaptersAddresses()
+ *
+ * Locates DNS info using GetAdaptersAddresses() function from the Internet
+ * Protocol Helper (IP Helper) API. When located, this returns a pointer
+ * in *outptr to a newly allocated memory area holding a null-terminated
+ * string with a space or comma seperated list of DNS IP addresses.
+ *
+ * Returns 0 and nullifies *outptr upon inability to return DNSes string.
+ *
+ * Returns 1 and sets *outptr when returning a dynamically allocated string.
+ *
+ * Implementation supports Windows XP and newer.
+ */
+#define IPAA_INITIAL_BUF_SZ 15 * 1024
+#define IPAA_MAX_TRIES 3
+static int get_DNS_AdaptersAddresses(char **outptr)
+{
+  IP_ADAPTER_DNS_SERVER_ADDRESS *ipaDNSAddr;
+  IP_ADAPTER_ADDRESSES *ipaa, *newipaa, *ipaaEntry;
+  ULONG ReqBufsz = IPAA_INITIAL_BUF_SZ;
+  ULONG Bufsz = IPAA_INITIAL_BUF_SZ;
+  ULONG AddrFlags = 0;
+  int trying = IPAA_MAX_TRIES;
+  int res;
+
+  union {
+    struct sockaddr     *sa;
+    struct sockaddr_in  *sa4;
+    struct sockaddr_in6 *sa6;
+  } namesrvr;
+
+  char txtaddr[sizeof("ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255")];
+
+  *outptr = NULL;
+
+  /* Verify run-time availability of GetAdaptersAddresses() */
+  if (ares_fpGetAdaptersAddresses == ZERO_NULL)
+    return 0;
+
+  ipaa = ares_malloc(Bufsz);
+  if (!ipaa)
+    return 0;
+
+  /* Usually this call suceeds with initial buffer size */
+  res = (*ares_fpGetAdaptersAddresses) (AF_UNSPEC, AddrFlags, NULL,
+                                        ipaa, &ReqBufsz);
+  if ((res != ERROR_BUFFER_OVERFLOW) && (res != ERROR_SUCCESS))
+    goto done;
+
+  while ((res == ERROR_BUFFER_OVERFLOW) && (--trying))
+  {
+    if (Bufsz < ReqBufsz)
+    {
+      newipaa = ares_realloc(ipaa, ReqBufsz);
+      if (!newipaa)
+        goto done;
+      Bufsz = ReqBufsz;
+      ipaa = newipaa;
+    }
+    res = (*ares_fpGetAdaptersAddresses) (AF_UNSPEC, AddrFlags, NULL,
+                                          ipaa, &ReqBufsz);
+    if (res == ERROR_SUCCESS)
+      break;
+  }
+  if (res != ERROR_SUCCESS)
+    goto done;
+
+  for (ipaaEntry = ipaa; ipaaEntry; ipaaEntry = ipaaEntry->Next)
+  {
+    if(ipaaEntry->OperStatus != IfOperStatusUp)
+        continue;
+
+    for (ipaDNSAddr = ipaaEntry->FirstDnsServerAddress;
+         ipaDNSAddr;
+         ipaDNSAddr = ipaDNSAddr->Next)
+    {
+      namesrvr.sa = ipaDNSAddr->Address.lpSockaddr;
+
+      if (namesrvr.sa->sa_family == AF_INET)
+      {
+        if ((namesrvr.sa4->sin_addr.S_un.S_addr == INADDR_ANY) ||
+            (namesrvr.sa4->sin_addr.S_un.S_addr == INADDR_NONE))
+          continue;
+        if (! ares_inet_ntop(AF_INET, &namesrvr.sa4->sin_addr,
+                             txtaddr, sizeof(txtaddr)))
+          continue;
+      }
+      else if (namesrvr.sa->sa_family == AF_INET6)
+      {
+        if (memcmp(&namesrvr.sa6->sin6_addr, &ares_in6addr_any,
+                   sizeof(namesrvr.sa6->sin6_addr)) == 0)
+          continue;
+        if (! ares_inet_ntop(AF_INET6, &namesrvr.sa6->sin6_addr,
+                             txtaddr, sizeof(txtaddr)))
+          continue;
+      }
+      else
+        continue;
+
+      commajoin(outptr, txtaddr);
+
+      if (!*outptr)
+        goto done;
+    }
+  }
+
+done:
+  if (ipaa)
+    ares_free(ipaa);
+
+  if (!*outptr)
+    return 0;
+
+  return 1;
+}
+
+/*
+ * get_DNS_Windows()
+ *
+ * Locates DNS info from Windows employing most suitable methods available at
+ * run-time no matter which Windows version it is. When located, this returns
+ * a pointer in *outptr to a newly allocated memory area holding a string with
+ * a space or comma seperated list of DNS IP addresses, null-terminated.
+ *
+ * Returns 0 and nullifies *outptr upon inability to return DNSes string.
+ *
+ * Returns 1 and sets *outptr when returning a dynamically allocated string.
+ *
+ * Implementation supports Windows 95 and newer.
+ */
+static int get_DNS_Windows(char **outptr)
+{
+  /*
+     Use GetNetworkParams First in case of
+     multiple adapter is enabled on this machine.
+     GetAdaptersAddresses will retrive dummy dns servers.
+     That will slowing DNS lookup.
+  */
+  /* Try using IP helper API GetNetworkParams() */
+  if (get_DNS_NetworkParams(outptr))
+    return 1;
+
+  /* Try using IP helper API GetAdaptersAddresses() */
+  if (get_DNS_AdaptersAddresses(outptr))
+    return 1;
+
+  /* Fall-back to registry information */
+  return get_DNS_Registry(outptr);
+}
+#endif
+
+static int init_by_resolv_conf(ares_channel channel)
+{
+#if !defined(ANDROID) && !defined(__ANDROID__) && !defined(WATT32) && \
+    !defined(CARES_USE_LIBRESOLV)
+  char *line = NULL;
+#endif
+  int status = -1, nservers = 0, nsort = 0;
+  struct server_state *servers = NULL;
+  struct apattern *sortlist = NULL;
+
+#ifdef WIN32
+
+  if (channel->nservers > -1)  /* don't override ARES_OPT_SERVER */
+     return ARES_SUCCESS;
+
+  if (get_DNS_Windows(&line))
+  {
+    status = config_nameserver(&servers, &nservers, line);
+    ares_free(line);
+  }
+
+  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 = ares_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;
+
+    ares_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 = ares_malloc(sizeof(struct server_state));
+  if (!servers)
+     return ARES_ENOMEM;
+  memset(servers, 0, sizeof(struct server_state));
+
+  for (i = 0; def_nameservers[i]; i++)
+  {
+    servers[i].addr.addrV4.s_addr = htonl(def_nameservers[i]);
+    servers[i].addr.family = AF_INET;
+    servers[i].addr.udp_port = 0;
+    servers[i].addr.tcp_port = 0;
+  }
+  status = ARES_EOF;
+
+#elif defined(ANDROID) || defined(__ANDROID__)
+  unsigned int i;
+  char propname[PROP_NAME_MAX];
+  char propvalue[PROP_VALUE_MAX]="";
+
+  for (i = 1; i <= MAX_DNS_PROPERTIES; i++) {
+    snprintf(propname, sizeof(propname), "%s%u", DNS_PROP_NAME_PREFIX, i);
+    if (__system_property_get(propname, propvalue) < 1) {
+      status = ARES_EOF;
+      break;
+    }
+    status = config_nameserver(&servers, &nservers, propvalue);
+    if (status != ARES_SUCCESS)
+      break;
+    status = ARES_EOF;
+  }
+#elif defined(CARES_USE_LIBRESOLV)
+  struct __res_state res;
+  memset(&res, 0, sizeof(res));
+  int result = res_ninit(&res);
+  if (result == 0 && (res.options & RES_INIT)) {
+    status = ARES_EOF;
+
+    if (channel->nservers == -1) {
+      union res_sockaddr_union addr[MAXNS];
+      int nscount = res_getservers(&res, addr, MAXNS);
+      for (int i = 0; i < nscount; ++i) {
+        char str[INET6_ADDRSTRLEN];
+        int config_status;
+        sa_family_t family = addr[i].sin.sin_family;
+        if (family == AF_INET) {
+          ares_inet_ntop(family, &addr[i].sin.sin_addr, str, sizeof(str));
+        } else if (family == AF_INET6) {
+          ares_inet_ntop(family, &addr[i].sin6.sin6_addr, str, sizeof(str));
+        } else {
+          continue;
+        }
+
+        config_status = config_nameserver(&servers, &nservers, str);
+        if (config_status != ARES_SUCCESS) {
+          status = config_status;
+          break;
+        }
+      }
+    }
+    if (channel->ndomains == -1) {
+      int entries = 0;
+      while ((entries < MAXDNSRCH) && res.dnsrch[entries])
+        entries++;
+
+      channel->domains = ares_malloc(entries * sizeof(char *));
+      if (!channel->domains) {
+        status = ARES_ENOMEM;
+      } else {
+        channel->ndomains = entries;
+        for (int i = 0; i < channel->ndomains; ++i) {
+          channel->domains[i] = ares_strdup(res.dnsrch[i]);
+          if (!channel->domains[i])
+            status = ARES_ENOMEM;
+        }
+      }
+    }
+    if (channel->ndots == -1)
+      channel->ndots = res.ndots;
+    if (channel->tries == -1)
+      channel->tries = res.retry;
+    if (channel->rotate == -1)
+      channel->rotate = res.options & RES_ROTATE;
+    if (channel->timeout == -1)
+      channel->timeout = res.retrans * 1000;
+
+    res_ndestroy(&res);
+  }
+#else
+  {
+    char *p;
+    FILE *fp;
+    size_t linesize;
+    int error;
+    int update_domains;
+
+    /* Don't read resolv.conf and friends if we don't have to */
+    if (ARES_CONFIG_CHECK(channel))
+        return ARES_SUCCESS;
+
+    /* Only update search domains if they're not already specified */
+    update_domains = (channel->ndomains == -1);
+
+    fp = fopen(PATH_RESOLV_CONF, "r");
+    if (fp) {
+      while ((status = ares__read_line(fp, &line, &linesize)) == ARES_SUCCESS)
+      {
+        if ((p = try_config(line, "domain", ';')) && update_domains)
+          status = config_domain(channel, p);
+        else if ((p = try_config(line, "lookup", ';')) && !channel->lookups)
+          status = config_lookup(channel, p, "bind", NULL, "file");
+        else if ((p = try_config(line, "search", ';')) && update_domains)
+          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:", '\0')) && !channel->lookups)
+            (void)config_lookup(channel, p, "dns", "resolve", "files");
+        }
+        fclose(fp);
+      }
+      else {
+        error = ERRNO;
+        switch(error) {
+        case ENOENT:
+        case ESRCH:
+          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"));
+        }
+
+        /* ignore error, maybe we will get luck in next if clause */
+        status = ARES_EOF;
+      }
+    }
+
+    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", '\0')) && !channel->lookups)
+            /* ignore errors */
+            (void)config_lookup(channel, p, "bind", NULL, "hosts");
+        }
+        fclose(fp);
+      }
+      else {
+        error = ERRNO;
+        switch(error) {
+        case ENOENT:
+        case ESRCH:
+          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"));
+        }
+
+        /* ignore error, maybe we will get luck in next if clause */
+        status = ARES_EOF;
+      }
+    }
+
+    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=", '\0')) && !channel->lookups)
+            /* ignore errors */
+            (void)config_lookup(channel, p, "bind", NULL, "local");
+        }
+        fclose(fp);
+      }
+      else {
+        error = ERRNO;
+        switch(error) {
+        case ENOENT:
+        case ESRCH:
+          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"));
+        }
+
+        /* ignore error, default value will be chosen for `channel->lookups` */
+        status = ARES_EOF;
+      }
+    }
+
+    if(line)
+      ares_free(line);
+  }
+
+#endif
+
+  /* Handle errors. */
+  if (status != ARES_EOF)
+    {
+      if (servers != NULL)
+        ares_free(servers);
+      if (sortlist != NULL)
+        ares_free(sortlist);
+      return status;
+    }
+
+  /* If we got any name server entries, fill them in. */
+  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;
+#ifdef HAVE_GETHOSTNAME
+  char *dot;
+#endif
+
+  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->ednspsz == -1)
+    channel->ednspsz = EDNSPACKETSZ;
+
+  if (channel->nservers == -1) {
+    /* If nobody specified servers, try a local named. */
+    channel->servers = ares_malloc(sizeof(struct server_state));
+    if (!channel->servers) {
+      rc = ARES_ENOMEM;
+      goto error;
+    }
+    channel->servers[0].addr.family = AF_INET;
+    channel->servers[0].addr.addrV4.s_addr = htonl(INADDR_LOOPBACK);
+    channel->servers[0].addr.udp_port = 0;
+    channel->servers[0].addr.tcp_port = 0;
+    channel->nservers = 1;
+  }
+
+#if defined(USE_WINSOCK)
+#define toolong(x) (x == -1) &&  (SOCKERRNO == WSAEFAULT)
+#elif defined(ENAMETOOLONG)
+#define toolong(x) (x == -1) && ((SOCKERRNO == ENAMETOOLONG) || \
+                                 (SOCKERRNO == EINVAL))
+#else
+#define toolong(x) (x == -1) &&  (SOCKERRNO == EINVAL)
+#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.
+     */
+#ifndef HAVE_GETHOSTNAME
+    channel->ndomains = 0; /* default to none */
+#else
+    GETHOSTNAME_TYPE_ARG2 lenv = 64;
+    size_t len = 64;
+    int res;
+    channel->ndomains = 0; /* default to none */
+
+    hostname = ares_malloc(len);
+    if(!hostname) {
+      rc = ARES_ENOMEM;
+      goto error;
+    }
+
+    do {
+      res = gethostname(hostname, lenv);
+
+      if(toolong(res)) {
+        char *p;
+        len *= 2;
+        lenv *= 2;
+        p = ares_realloc(hostname, len);
+        if(!p) {
+          rc = ARES_ENOMEM;
+          goto error;
+        }
+        hostname = p;
+        continue;
+      }
+      else if(res) {
+        rc = ARES_EBADNAME;
+        goto error;
+      }
+
+    } while (res != 0);
+
+    dot = strchr(hostname, '.');
+    if (dot) {
+      /* a dot was found */
+      channel->domains = ares_malloc(sizeof(char *));
+      if (!channel->domains) {
+        rc = ARES_ENOMEM;
+        goto error;
+      }
+      channel->domains[0] = ares_strdup(dot + 1);
+      if (!channel->domains[0]) {
+        rc = ARES_ENOMEM;
+        goto error;
+      }
+      channel->ndomains = 1;
+    }
+#endif
+  }
+
+  if (channel->nsort == -1) {
+    channel->sortlist = NULL;
+    channel->nsort = 0;
+  }
+
+  if (!channel->lookups) {
+    channel->lookups = ares_strdup("fb");
+    if (!channel->lookups)
+      rc = ARES_ENOMEM;
+  }
+
+  error:
+  if(rc) {
+    if(channel->servers) {
+      ares_free(channel->servers);
+      channel->servers = NULL;
+    }
+
+    if(channel->domains && channel->domains[0])
+      ares_free(channel->domains[0]);
+    if(channel->domains) {
+      ares_free(channel->domains);
+      channel->domains = NULL;
+    }
+
+    if(channel->lookups) {
+      ares_free(channel->lookups);
+      channel->lookups = NULL;
+    }
+  }
+
+  if(hostname)
+    ares_free(hostname);
+
+  return rc;
+}
+
+#if !defined(WIN32) && !defined(WATT32) && \
+    !defined(ANDROID) && !defined(__ANDROID__) && !defined(CARES_USE_LIBRESOLV)
+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);
+}
+
+#if defined(__INTEL_COMPILER) && (__INTEL_COMPILER == 910) && \
+    defined(__OPTIMIZE__) && defined(__unix__) &&  defined(__i386__)
+  /* workaround icc 9.1 optimizer issue */
+# define vqualifier volatile
+#else
+# define vqualifier
+#endif
+
+static int config_lookup(ares_channel channel, const char *str,
+                         const char *bindch, const char *altbindch,
+                         const char *filech)
+{
+  char lookups[3], *l;
+  const char *vqualifier p;
+
+  if (altbindch == NULL)
+    altbindch = bindch;
+
+  /* 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 == *altbindch || *p == *filech) && l < lookups + 2) {
+        if (*p == *bindch || *p == *altbindch) *l++ = 'b';
+        else *l++ = 'f';
+      }
+      while (*p && !ISSPACE(*p) && (*p != ','))
+        p++;
+      while (*p && (ISSPACE(*p) || (*p == ',')))
+        p++;
+    }
+  *l = '\0';
+  channel->lookups = ares_strdup(lookups);
+  return (channel->lookups) ? ARES_SUCCESS : ARES_ENOMEM;
+}
+#endif  /* !WIN32 & !WATT32 & !ANDROID & !__ANDROID__ & !CARES_USE_LIBRESOLV */
+
+#ifndef WATT32
+static int config_nameserver(struct server_state **servers, int *nservers,
+                             char *str)
+{
+  struct ares_addr host;
+  struct server_state *newserv;
+  char *p, *txtaddr;
+  /* On Windows, there may be more than one nameserver specified in the same
+   * registry key, so we parse input as a space or comma seperated list.
+   */
+  for (p = str; p;)
+    {
+      /* Skip whitespace and commas. */
+      while (*p && (ISSPACE(*p) || (*p == ',')))
+        p++;
+      if (!*p)
+        /* No more input, done. */
+        break;
+
+      /* Pointer to start of IPv4 or IPv6 address part. */
+      txtaddr = p;
+
+      /* Advance past this address. */
+      while (*p && !ISSPACE(*p) && (*p != ','))
+        p++;
+      if (*p)
+        /* Null terminate this address. */
+        *p++ = '\0';
+      else
+        /* Reached end of input, done when this address is processed. */
+        p = NULL;
+
+      /* Convert textual address to binary format. */
+      if (ares_inet_pton(AF_INET, txtaddr, &host.addrV4) == 1)
+        host.family = AF_INET;
+      else if (ares_inet_pton(AF_INET6, txtaddr, &host.addrV6) == 1)
+        host.family = AF_INET6;
+      else
+        continue;
+
+      /* Resize servers state array. */
+      newserv = ares_realloc(*servers, (*nservers + 1) *
+                             sizeof(struct server_state));
+      if (!newserv)
+        return ARES_ENOMEM;
+
+      /* Store address data. */
+      newserv[*nservers].addr.family = host.family;
+      newserv[*nservers].addr.udp_port = 0;
+      newserv[*nservers].addr.tcp_port = 0;
+      if (host.family == AF_INET)
+        memcpy(&newserv[*nservers].addr.addrV4, &host.addrV4,
+               sizeof(host.addrV4));
+      else
+        memcpy(&newserv[*nservers].addr.addrV6, &host.addrV6,
+               sizeof(host.addrV6));
+
+      /* Update arguments. */
+      *servers = newserv;
+      *nservers += 1;
+    }
+
+  return ARES_SUCCESS;
+}
+#endif  /* !WATT32 */
+
+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, q-str);
+      ipbuf[q-str] = '\0';
+      /* Find the prefix */
+      if (*q == '/')
+        {
+          const char *str2 = q+1;
+          while (*q && *q != ';' && !ISSPACE(*q))
+            q++;
+          memcpy(ipbufpfx, str, q-str);
+          ipbufpfx[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.addrV6,
+                                     sizeof(pat.addrV6))) > 0)
+        {
+          pat.type = PATTERN_CIDR;
+          pat.mask.bits = (unsigned short)bits;
+          pat.family = AF_INET6;
+          if (!sortlist_alloc(sortlist, nsort, &pat)) {
+            ares_free(*sortlist);
+            *sortlist = NULL;
+            return ARES_ENOMEM;
+          }
+        }
+      else if (ipbufpfx[0] &&
+               (bits = ares_inet_net_pton(AF_INET, ipbufpfx, &pat.addrV4,
+                                          sizeof(pat.addrV4))) > 0)
+        {
+          pat.type = PATTERN_CIDR;
+          pat.mask.bits = (unsigned short)bits;
+          pat.family = AF_INET;
+          if (!sortlist_alloc(sortlist, nsort, &pat)) {
+            ares_free(*sortlist);
+            *sortlist = NULL;
+            return ARES_ENOMEM;
+          }
+        }
+      /* See if it is just a regular IP */
+      else if (ip_addr(ipbuf, q-str, &pat.addrV4) == 0)
+        {
+          if (ipbufpfx[0])
+            {
+              memcpy(ipbuf, str, q-str);
+              ipbuf[q-str] = '\0';
+              if (ip_addr(ipbuf, q-str, &pat.mask.addr4) != 0)
+                natural_mask(&pat);
+            }
+          else
+            natural_mask(&pat);
+          pat.family = AF_INET;
+          pat.type = PATTERN_MASK;
+          if (!sortlist_alloc(sortlist, nsort, &pat)) {
+            ares_free(*sortlist);
+            *sortlist = NULL;
+            return ARES_ENOMEM;
+          }
+        }
+      else
+        {
+          while (*q && *q != ';' && !ISSPACE(*q))
+            q++;
+        }
+      str = q;
+      while (ISSPACE(*str))
+        str++;
+    }
+
+  return ARES_SUCCESS;
+}
+
+static int set_search(ares_channel channel, const char *str)
+{
+  int n;
+  const char *p, *q;
+
+  if(channel->ndomains != -1) {
+    /* LCOV_EXCL_START: all callers check ndomains == -1 */
+    /* if we already have some domains present, free them first */
+    for(n=0; n < channel->ndomains; n++)
+      ares_free(channel->domains[n]);
+    ares_free(channel->domains);
+    channel->domains = NULL;
+    channel->ndomains = -1;
+  } /* LCOV_EXCL_STOP */
+
+  /* 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 = ares_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] = ares_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 = aresx_sltosi(strtol(val, NULL, 10));
+      val = try_option(p, q, "retrans:");
+      if (val && channel->timeout == -1)
+        channel->timeout = aresx_sltosi(strtol(val, NULL, 10));
+      val = try_option(p, q, "retry:");
+      if (val && channel->tries == -1)
+        channel->tries = aresx_sltosi(strtol(val, NULL, 10));
+      val = try_option(p, q, "rotate");
+      if (val && channel->rotate == -1)
+        channel->rotate = 1;
+      p = q;
+      while (ISSPACE(*p))
+        p++;
+    }
+
+  return ARES_SUCCESS;
+}
+
+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;
+}
+
+#if !defined(WIN32) && !defined(WATT32) && \
+    !defined(ANDROID) && !defined(__ANDROID__) && !defined(CARES_USE_LIBRESOLV)
+static char *try_config(char *s, const char *opt, char scc)
+{
+  size_t len;
+  char *p;
+  char *q;
+
+  if (!s || !opt)
+    /* no line or no option */
+    return NULL;  /* LCOV_EXCL_LINE */
+
+  /* Hash '#' character is always used as primary comment char, additionally
+     a not-NUL secondary comment char will be considered when specified. */
+
+  /* trim line comment */
+  p = s;
+  if(scc)
+    while (*p && (*p != '#') && (*p != scc))
+      p++;
+  else
+    while (*p && (*p != '#'))
+      p++;
+  *p = '\0';
+
+  /* trim trailing whitespace */
+  q = p - 1;
+  while ((q >= s) && ISSPACE(*q))
+    q--;
+  *++q = '\0';
+
+  /* skip leading whitespace */
+  p = s;
+  while (*p && ISSPACE(*p))
+    p++;
+
+  if (!*p)
+    /* empty line */
+    return NULL;
+
+  if ((len = strlen(opt)) == 0)
+    /* empty option */
+    return NULL;  /* LCOV_EXCL_LINE */
+
+  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;  /* LCOV_EXCL_LINE */
+
+  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  /* !WIN32 & !WATT32 & !ANDROID & !__ANDROID__ */
+
+static int ip_addr(const char *ipbuf, ssize_t 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->addrV4.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.addr4.s_addr = htonl(IN_CLASSA_NET);
+  else if (IN_CLASSB(addr.s_addr))
+    pat->mask.addr4.s_addr = htonl(IN_CLASSB_NET);
+  else
+    pat->mask.addr4.s_addr = htonl(IN_CLASSC_NET);
+}
+
+static int sortlist_alloc(struct apattern **sortlist, int *nsort,
+                          struct apattern *pat)
+{
+  struct apattern *newsort;
+  newsort = ares_realloc(*sortlist, (*nsort + 1) * sizeof(struct apattern));
+  if (!newsort)
+    return 0;
+  newsort[*nsort] = *pat;
+  *sortlist = newsort;
+  (*nsort)++;
+  return 1;
+}
+
+/* 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
+  BOOLEAN res;
+  if (ares_fpSystemFunction036)
+    {
+      res = (*ares_fpSystemFunction036) (key, key_data_len);
+      if (res)
+        randomized = 1;
+    }
+#else /* !WIN32 */
+#ifdef RANDOM_FILE
+  FILE *f = fopen(RANDOM_FILE, "rb");
+  if(f) {
+    counter = aresx_uztosi(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);  /* LCOV_EXCL_LINE */
+  }
+}
+
+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 = ares_malloc(key_data_len);
+  if (!key_data_ptr)
+    return ARES_ENOMEM;
+  memset(key_data_ptr, 0, key_data_len);
+
+  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);
+  }
+  ares_free(key_data_ptr);
+  return ARES_SUCCESS;
+}
+
+void ares_set_local_ip4(ares_channel channel, unsigned int local_ip)
+{
+  channel->local_ip4 = local_ip;
+}
+
+/* local_ip6 should be 16 bytes in length */
+void ares_set_local_ip6(ares_channel channel,
+                        const unsigned char* local_ip6)
+{
+  memcpy(&channel->local_ip6, local_ip6, sizeof(channel->local_ip6));
+}
+
+/* local_dev_name should be null terminated. */
+void ares_set_local_dev(ares_channel channel,
+                        const char* local_dev_name)
+{
+  strncpy(channel->local_dev_name, local_dev_name,
+          sizeof(channel->local_dev_name));
+  channel->local_dev_name[sizeof(channel->local_dev_name) - 1] = 0;
+}
+
+
+void ares_set_socket_callback(ares_channel channel,
+                              ares_sock_create_callback cb,
+                              void *data)
+{
+  channel->sock_create_cb = cb;
+  channel->sock_create_cb_data = data;
+}
+
+void ares_set_socket_configure_callback(ares_channel channel,
+                                        ares_sock_config_callback cb,
+                                        void *data)
+{
+  channel->sock_config_cb = cb;
+  channel->sock_config_cb_data = data;
+}
+
+void ares_set_socket_functions(ares_channel channel,
+                               const struct ares_socket_functions * funcs,
+                               void *data)
+{
+  channel->sock_funcs = funcs;
+  channel->sock_func_cb_data = data;
+}
+
+int ares_set_sortlist(ares_channel channel, const char *sortstr)
+{
+  int nsort = 0;
+  struct apattern *sortlist = NULL;
+  int status;
+
+  if (!channel)
+    return ARES_ENODATA;
+
+  status = config_sortlist(&sortlist, &nsort, sortstr);
+  if (status == ARES_SUCCESS && sortlist) {
+    if (channel->sortlist)
+      ares_free(channel->sortlist);
+    channel->sortlist = sortlist;
+    channel->nsort = nsort;
+  }
+  return status;
+}
+
+void ares__init_servers_state(ares_channel channel)
+{
+  struct server_state *server;
+  int i;
+
+  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_pos = 0;
+      server->tcp_buffer = NULL;
+      server->tcp_length = 0;
+      server->qhead = NULL;
+      server->qtail = NULL;
+      ares__init_list_head(&server->queries_to_server);
+      server->channel = channel;
+      server->is_broken = 0;
+    }
+}