src/lib/ares_sysconfig.c - third_party/c-ares - Git at Google

 /* MIT License
  *
  * Copyright (c) 1998 Massachusetts Institute of Technology
  * Copyright (c) 2007 Daniel Stenberg
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice (including the next
  * paragraph) shall be included in all copies or substantial portions of the
  * Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  * SOFTWARE.
  *
  * SPDX-License-Identifier: MIT
  */

 #include "ares_private.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

 #if defined(ANDROID) || defined(__ANDROID__)
 #  include <sys/system_properties.h>
 #  include "ares_android.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_inet_net_pton.h"


 #if defined(__MVS__)
 static ares_status_t ares_init_sysconfig_mvs(const ares_channel_t *channel,
                                              ares_sysconfig_t     *sysconfig)
 {
   struct __res_state *res = 0;
   size_t              count4;
   size_t              count6;
   int                 i;
   __STATEEXTIPV6     *v6;
   arse__llist_t      *sconfig = NULL;
   ares_status_t       status;

   if (0 == res) {
     int rc = res_init();
     while (rc == -1 && h_errno == TRY_AGAIN) {
       rc = res_init();
     }
     if (rc == -1) {
       return ARES_ENOMEM;
     }
     res = __res();
   }

   v6 = res->__res_extIPv6;
   if (res->nscount > 0) {
     count4 = (size_t)res->nscount;
   }

   if (v6 && v6->__stat_nscount > 0) {
     count6 = (size_t)v6->__stat_nscount;
   } else {
     count6 = 0;
   }

   for (i = 0; i < count4; i++) {
     struct sockaddr_in *addr_in = &(res->nsaddr_list[i]);
     struct ares_addr    addr;

     addr.addr.addr4.s_addr = addr_in->sin_addr.s_addr;
     addr.family            = AF_INET;

     status = ares_sconfig_append(channel, &sysconfig->sconfig, &addr,
                                  htons(addr_in->sin_port),
                                  htons(addr_in->sin_port), NULL);

     if (status != ARES_SUCCESS) {
       return status;
     }
   }

   for (i = 0; i < count6; i++) {
     struct sockaddr_in6 *addr_in = &(v6->__stat_nsaddr_list[i]);
     struct ares_addr     addr;

     addr.family = AF_INET6;
     memcpy(&(addr.addr.addr6), &(addr_in->sin6_addr),
            sizeof(addr_in->sin6_addr));

     status = ares_sconfig_append(channel, &sysconfig->sconfig, &addr,
                                  htons(addr_in->sin_port),
                                  htons(addr_in->sin_port), NULL);

     if (status != ARES_SUCCESS) {
       return status;
     }
   }

   return ARES_SUCCESS;
 }
 #endif

 #if defined(__riscos__)
 static ares_status_t ares_init_sysconfig_riscos(const ares_channel_t *channel,
                                                 ares_sysconfig_t     *sysconfig)
 {
   char         *line;
   ares_status_t status = ARES_SUCCESS;

   /* Under RISC OS, name servers are listed in the
      system variable Inet$Resolvers, space separated. */
   line = getenv("Inet$Resolvers");
   if (line) {
     char *resolvers = ares_strdup(line);
     char *pos;
     char *space;

     if (!resolvers) {
       return ARES_ENOMEM;
     }

     pos = resolvers;
     do {
       space = strchr(pos, ' ');
       if (space) {
         *space = '\0';
       }
       status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig, pos,
                                            ARES_TRUE);
       if (status != ARES_SUCCESS) {
         break;
       }
       pos = space + 1;
     } while (space);

     ares_free(resolvers);
   }

   return status;
 }
 #endif

 #if defined(WATT32)
 static ares_status_t ares_init_sysconfig_watt32(const ares_channel_t *channel,
                                                 ares_sysconfig_t     *sysconfig)
 {
   size_t        i;
   ares_status_t status;

   sock_init();

   for (i = 0; def_nameservers[i]; i++) {
     struct ares_addr addr;

     addr.family            = AF_INET;
     addr.addr.addr4.s_addr = htonl(def_nameservers[i]);

     status =
       ares_sconfig_append(channel, &sysconfig->sconfig, &addr, 0, 0, NULL);

     if (status != ARES_SUCCESS) {
       return status;
     }
   }

   return ARES_SUCCESS;
 }
 #endif

 #if defined(ANDROID) || defined(__ANDROID__)
 static ares_status_t ares_init_sysconfig_android(const ares_channel_t *channel,
                                                  ares_sysconfig_t *sysconfig)
 {
   size_t        i;
   char        **dns_servers;
   char         *domains;
   size_t        num_servers;
   ares_status_t status = ARES_EFILE;

   /* Use the Android connectivity manager to get a list
    * of DNS servers. As of Android 8 (Oreo) net.dns#
    * system properties are no longer available. Google claims this
    * improves privacy. Apps now need the ACCESS_NETWORK_STATE
    * permission and must use the ConnectivityManager which
    * is Java only. */
   dns_servers = ares_get_android_server_list(MAX_DNS_PROPERTIES, &num_servers);
   if (dns_servers != NULL) {
     for (i = 0; i < num_servers; i++) {
       status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig,
                                            dns_servers[i], ARES_TRUE);
       if (status != ARES_SUCCESS) {
         return status;
       }
     }
     for (i = 0; i < num_servers; i++) {
       ares_free(dns_servers[i]);
     }
     ares_free(dns_servers);
   }

   domains            = ares_get_android_search_domains_list();
   sysconfig->domains = ares_strsplit(domains, ", ", &sysconfig->ndomains);
   ares_free(domains);

 #  ifdef HAVE___SYSTEM_PROPERTY_GET
   /* Old way using the system property still in place as
    * a fallback. Older android versions can still use this.
    * it's possible for older apps not not have added the new
    * permission and we want to try to avoid breaking those.
    *
    * We'll only run this if we don't have any dns servers
    * because this will get the same ones (if it works). */
   if (sysconfig->sconfig == NULL) {
     char propname[PROP_NAME_MAX];
     char propvalue[PROP_VALUE_MAX] = "";
     for (i = 1; i <= MAX_DNS_PROPERTIES; i++) {
       snprintf(propname, sizeof(propname), "%s%zu", DNS_PROP_NAME_PREFIX, i);
       if (__system_property_get(propname, propvalue) < 1) {
         break;
       }
       status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig,
                                            propvalue, ARES_TRUE);
       if (status != ARES_SUCCESS) {
         return status;
       }
     }
   }
 #  endif /* HAVE___SYSTEM_PROPERTY_GET */

   return status;
 }
 #endif

 #if defined(__QNX__)
 static ares_status_t
   ares_init_sysconfig_qnx(const ares_channel_t *channel,
                           ares_sysconfig_t     *sysconfig)
 {
   /* QNX:
    *   1. use confstr(_CS_RESOLVE, ...) as primary resolv.conf data, replacing
    *      "_" with " ".  If that is empty, then do normal /etc/resolv.conf
    *      processing.
    *   2. We want to process /etc/nsswitch.conf as normal.
    *   3. if confstr(_CS_DOMAIN, ...) this is the domain name.  Use this as
    *      preference over anything else found.
    */
   ares_buf_t    *buf                = ares_buf_create();
   unsigned char *data               = NULL;
   size_t         data_size          = 0;
   ares_bool_t    process_resolvconf = ARES_TRUE;
   ares_status_t  status             = ARES_SUCCESS;

   /* Prefer confstr(_CS_RESOLVE, ...) */
   buf = ares_buf_create();
   if (buf == NULL) {
     status = ARES_ENOMEM;
     goto done;
   }

   data_size = 1024;
   data      = ares_buf_append_start(buf, &data_size);
   if (data == NULL) {
     status = ARES_ENOMEM;
     goto done;
   }

   data_size = confstr(_CS_RESOLVE, (char *)data, data_size);
   if (data_size > 1) {
     /* confstr returns byte for NULL terminator, strip */
     data_size--;

     ares_buf_append_finish(buf, data_size);
     /* Its odd, this uses _ instead of " " between keywords, otherwise the
      * format is the same as resolv.conf, replace. */
     ares_buf_replace(buf, (const unsigned char *)"_", 1,
                      (const unsigned char *)" ", 1);

     status = ares_sysconfig_process_buf(channel, sysconfig, buf,
                                         ares_sysconfig_parse_resolv_line);
     if (status != ARES_SUCCESS) {
       /* ENOMEM is really the only error we'll get here */
       goto done;
     }

     /* don't read resolv.conf if we processed *any* nameservers */
     if (ares_llist_len(sysconfig->sconfig) != 0) {
       process_resolvconf = ARES_FALSE;
     }
   }

   /* Process files */
   status = ares_init_sysconfig_files(channel, sysconfig, process_resolvconf);
   if (status != ARES_SUCCESS) {
     goto done;
   }

   /* Read confstr(_CS_DOMAIN, ...), but if we had a search path specified with
    * more than one domain, lets prefer that instead.  Its not exactly clear
    * the best way to handle this. */
   if (sysconfig->ndomains <= 1) {
     char   domain[256];
     size_t domain_len;

     domain_len = confstr(_CS_DOMAIN, domain, sizeof(domain_len));
     if (domain_len != 0) {
       ares_strsplit_free(sysconfig->domains, sysconfig->ndomains);
       sysconfig->domains = ares_strsplit(domain, ", ", &sysconfig->ndomains);
       if (sysconfig->domains == NULL) {
         status = ARES_ENOMEM;
         goto done;
       }
     }
   }

 done:
   ares_buf_destroy(buf);

   return status;
 }
 #endif

 #if defined(CARES_USE_LIBRESOLV)
 static ares_status_t
   ares_init_sysconfig_libresolv(const ares_channel_t *channel,
                                 ares_sysconfig_t     *sysconfig)
 {
   struct __res_state       res;
   ares_status_t            status = ARES_SUCCESS;
   union res_sockaddr_union addr[MAXNS];
   int                      nscount;
   size_t                   i;
   size_t                   entries = 0;
   ares_buf_t              *ipbuf   = NULL;

   memset(&res, 0, sizeof(res));

   if (res_ninit(&res) != 0 || !(res.options & RES_INIT)) {
     return ARES_EFILE;
   }

   nscount = res_getservers(&res, addr, MAXNS);

   for (i = 0; i < (size_t)nscount; ++i) {
     char           ipaddr[INET6_ADDRSTRLEN] = "";
     char          *ipstr                    = NULL;
     unsigned short port                     = 0;
     unsigned int   ll_scope                 = 0;

     sa_family_t    family = addr[i].sin.sin_family;
     if (family == AF_INET) {
       ares_inet_ntop(family, &addr[i].sin.sin_addr, ipaddr, sizeof(ipaddr));
       port = ntohs(addr[i].sin.sin_port);
     } else if (family == AF_INET6) {
       ares_inet_ntop(family, &addr[i].sin6.sin6_addr, ipaddr, sizeof(ipaddr));
       port     = ntohs(addr[i].sin6.sin6_port);
       ll_scope = addr[i].sin6.sin6_scope_id;
     } else {
       continue;
     }


     /* [ip]:port%iface */
     ipbuf = ares_buf_create();
     if (ipbuf == NULL) {
       status = ARES_ENOMEM;
       goto done;
     }

     status = ares_buf_append_str(ipbuf, "[");
     if (status != ARES_SUCCESS) {
       goto done;
     }

     status = ares_buf_append_str(ipbuf, ipaddr);
     if (status != ARES_SUCCESS) {
       goto done;
     }

     status = ares_buf_append_str(ipbuf, "]");
     if (status != ARES_SUCCESS) {
       goto done;
     }

     if (port) {
       status = ares_buf_append_str(ipbuf, ":");
       if (status != ARES_SUCCESS) {
         goto done;
       }
       status = ares_buf_append_num_dec(ipbuf, port, 0);
       if (status != ARES_SUCCESS) {
         goto done;
       }
     }

     if (ll_scope) {
       status = ares_buf_append_str(ipbuf, "%");
       if (status != ARES_SUCCESS) {
         goto done;
       }
       status = ares_buf_append_num_dec(ipbuf, ll_scope, 0);
       if (status != ARES_SUCCESS) {
         goto done;
       }
     }

     ipstr = ares_buf_finish_str(ipbuf, NULL);
     ipbuf = NULL;
     if (ipstr == NULL) {
       status = ARES_ENOMEM;
       goto done;
     }

     status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig, ipstr,
                                          ARES_TRUE);

     ares_free(ipstr);
     if (status != ARES_SUCCESS) {
       goto done;
     }
   }

   while ((entries < MAXDNSRCH) && res.dnsrch[entries]) {
     entries++;
   }

   if (entries) {
     sysconfig->domains = ares_malloc_zero(entries * sizeof(char *));
     if (sysconfig->domains == NULL) {
       status = ARES_ENOMEM;
       goto done;
     } else {
       sysconfig->ndomains = entries;
       for (i = 0; i < sysconfig->ndomains; i++) {
         sysconfig->domains[i] = ares_strdup(res.dnsrch[i]);
         if (sysconfig->domains[i] == NULL) {
           status = ARES_ENOMEM;
           goto done;
         }
       }
     }
   }

   if (res.ndots >= 0) {
     sysconfig->ndots = (size_t)res.ndots;
   }
 /* Apple does not allow configuration of retry, so this is a static dummy
  * value, ignore */
 #  ifndef __APPLE__
   if (res.retry > 0) {
     sysconfig->tries = (size_t)res.retry;
   }
 #  endif
   if (res.options & RES_ROTATE) {
     sysconfig->rotate = ARES_TRUE;
   }

   if (res.retrans > 0) {
 /* Apple does not allow configuration of retrans, so this is a dummy value
  * that is extremely high (5s) */
 #  ifndef __APPLE__
     if (res.retrans > 0) {
       sysconfig->timeout_ms = (unsigned int)res.retrans * 1000;
     }
 #  endif
   }

 done:
   ares_buf_destroy(ipbuf);
   res_ndestroy(&res);
   return status;
 }
 #endif

 static void ares_sysconfig_free(ares_sysconfig_t *sysconfig)
 {
   ares_llist_destroy(sysconfig->sconfig);
   ares_strsplit_free(sysconfig->domains, sysconfig->ndomains);
   ares_free(sysconfig->sortlist);
   ares_free(sysconfig->lookups);
   memset(sysconfig, 0, sizeof(*sysconfig));
 }

 static ares_status_t ares_sysconfig_apply(ares_channel_t         *channel,
                                           const ares_sysconfig_t *sysconfig)
 {
   ares_status_t status;

   if (sysconfig->sconfig && !(channel->optmask & ARES_OPT_SERVERS)) {
     status = ares_servers_update(channel, sysconfig->sconfig, ARES_FALSE);
     if (status != ARES_SUCCESS) {
       return status;
     }
   }

   if (sysconfig->domains && !(channel->optmask & ARES_OPT_DOMAINS)) {
     /* Make sure we duplicate first then replace so even if there is
      * ARES_ENOMEM, the channel stays in a good state */
     char **temp =
       ares_strsplit_duplicate(sysconfig->domains, sysconfig->ndomains);
     if (temp == NULL) {
       return ARES_ENOMEM; /* LCOV_EXCL_LINE: OutOfMemory */
     }

     ares_strsplit_free(channel->domains, channel->ndomains);
     channel->domains  = temp;
     channel->ndomains = sysconfig->ndomains;
   }

   if (sysconfig->lookups && !(channel->optmask & ARES_OPT_LOOKUPS)) {
     char *temp = ares_strdup(sysconfig->lookups);
     if (temp == NULL) {
       return ARES_ENOMEM; /* LCOV_EXCL_LINE: OutOfMemory */
     }

     ares_free(channel->lookups);
     channel->lookups = temp;
   }

   if (sysconfig->sortlist && !(channel->optmask & ARES_OPT_SORTLIST)) {
     struct apattern *temp =
       ares_malloc(sizeof(*channel->sortlist) * sysconfig->nsortlist);
     if (temp == NULL) {
       return ARES_ENOMEM; /* LCOV_EXCL_LINE: OutOfMemory */
     }
     memcpy(temp, sysconfig->sortlist,
            sizeof(*channel->sortlist) * sysconfig->nsortlist);

     ares_free(channel->sortlist);
     channel->sortlist = temp;
     channel->nsort    = sysconfig->nsortlist;
   }

   if (!(channel->optmask & ARES_OPT_NDOTS)) {
     channel->ndots = sysconfig->ndots;
   }

   if (sysconfig->tries && !(channel->optmask & ARES_OPT_TRIES)) {
     channel->tries = sysconfig->tries;
   }

   if (sysconfig->timeout_ms && !(channel->optmask & ARES_OPT_TIMEOUTMS)) {
     channel->timeout = sysconfig->timeout_ms;
   }

   if (!(channel->optmask & (ARES_OPT_ROTATE | ARES_OPT_NOROTATE))) {
     channel->rotate = sysconfig->rotate;
   }

   if (sysconfig->usevc) {
     channel->flags |= ARES_FLAG_USEVC;
   }

   return ARES_SUCCESS;
 }

 ares_status_t ares_init_by_sysconfig(ares_channel_t *channel)
 {
   ares_status_t    status;
   ares_sysconfig_t sysconfig;

   memset(&sysconfig, 0, sizeof(sysconfig));
   sysconfig.ndots = 1; /* Default value if not otherwise set */

 #if defined(USE_WINSOCK)
   status = ares_init_sysconfig_windows(channel, &sysconfig);
 #elif defined(__MVS__)
   status = ares_init_sysconfig_mvs(channel, &sysconfig);
 #elif defined(__riscos__)
   status = ares_init_sysconfig_riscos(channel, &sysconfig);
 #elif defined(WATT32)
   status = ares_init_sysconfig_watt32(channel, &sysconfig);
 #elif defined(ANDROID) || defined(__ANDROID__)
   status = ares_init_sysconfig_android(channel, &sysconfig);
 #elif defined(__APPLE__)
   status = ares_init_sysconfig_macos(channel, &sysconfig);
 #elif defined(CARES_USE_LIBRESOLV)
   status = ares_init_sysconfig_libresolv(channel, &sysconfig);
 #elif defined(__QNX__)
   status = ares_init_sysconfig_qnx(channel, &sysconfig);
 #else
   status = ares_init_sysconfig_files(channel, &sysconfig, ARES_TRUE);
 #endif

   if (status != ARES_SUCCESS) {
     goto done;
   }

   /* Environment is supposed to override sysconfig */
   status = ares_init_by_environment(&sysconfig);
   if (status != ARES_SUCCESS) {
     goto done;
   }

   /* Lock when applying the configuration to the channel.  Don't need to
    * lock prior to this. */

   ares_channel_lock(channel);

   status = ares_sysconfig_apply(channel, &sysconfig);
   ares_channel_unlock(channel);

   if (status != ARES_SUCCESS) {
     goto done;
   }

 done:
   ares_sysconfig_free(&sysconfig);

   return status;
 }
	/* MIT License
	*
	* Copyright (c) 1998 Massachusetts Institute of Technology
	* Copyright (c) 2007 Daniel Stenberg
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice (including the next
	* paragraph) shall be included in all copies or substantial portions of the
	* Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
	* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
	* SOFTWARE.
	*
	* SPDX-License-Identifier: MIT
	*/

	#include "ares_private.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

	#if defined(ANDROID) \|\| defined(__ANDROID__)
	# include <sys/system_properties.h>
	# include "ares_android.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_inet_net_pton.h"


	#if defined(__MVS__)
	static ares_status_t ares_init_sysconfig_mvs(const ares_channel_t *channel,
	ares_sysconfig_t *sysconfig)
	{
	struct __res_state *res = 0;
	size_t count4;
	size_t count6;
	int i;
	__STATEEXTIPV6 *v6;
	arse__llist_t *sconfig = NULL;
	ares_status_t status;

	if (0 == res) {
	int rc = res_init();
	while (rc == -1 && h_errno == TRY_AGAIN) {
	rc = res_init();
	}
	if (rc == -1) {
	return ARES_ENOMEM;
	}
	res = __res();
	}

	v6 = res->__res_extIPv6;
	if (res->nscount > 0) {
	count4 = (size_t)res->nscount;
	}

	if (v6 && v6->__stat_nscount > 0) {
	count6 = (size_t)v6->__stat_nscount;
	} else {
	count6 = 0;
	}

	for (i = 0; i < count4; i++) {
	struct sockaddr_in *addr_in = &(res->nsaddr_list[i]);
	struct ares_addr addr;

	addr.addr.addr4.s_addr = addr_in->sin_addr.s_addr;
	addr.family = AF_INET;

	status = ares_sconfig_append(channel, &sysconfig->sconfig, &addr,
	htons(addr_in->sin_port),
	htons(addr_in->sin_port), NULL);

	if (status != ARES_SUCCESS) {
	return status;
	}
	}

	for (i = 0; i < count6; i++) {
	struct sockaddr_in6 *addr_in = &(v6->__stat_nsaddr_list[i]);
	struct ares_addr addr;

	addr.family = AF_INET6;
	memcpy(&(addr.addr.addr6), &(addr_in->sin6_addr),
	sizeof(addr_in->sin6_addr));

	status = ares_sconfig_append(channel, &sysconfig->sconfig, &addr,
	htons(addr_in->sin_port),
	htons(addr_in->sin_port), NULL);

	if (status != ARES_SUCCESS) {
	return status;
	}
	}

	return ARES_SUCCESS;
	}
	#endif

	#if defined(__riscos__)
	static ares_status_t ares_init_sysconfig_riscos(const ares_channel_t *channel,
	ares_sysconfig_t *sysconfig)
	{
	char *line;
	ares_status_t status = ARES_SUCCESS;

	/* Under RISC OS, name servers are listed in the
	system variable Inet$Resolvers, space separated. */
	line = getenv("Inet$Resolvers");
	if (line) {
	char *resolvers = ares_strdup(line);
	char *pos;
	char *space;

	if (!resolvers) {
	return ARES_ENOMEM;
	}

	pos = resolvers;
	do {
	space = strchr(pos, ' ');
	if (space) {
	*space = '\0';
	}
	status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig, pos,
	ARES_TRUE);
	if (status != ARES_SUCCESS) {
	break;
	}
	pos = space + 1;
	} while (space);

	ares_free(resolvers);
	}

	return status;
	}
	#endif

	#if defined(WATT32)
	static ares_status_t ares_init_sysconfig_watt32(const ares_channel_t *channel,
	ares_sysconfig_t *sysconfig)
	{
	size_t i;
	ares_status_t status;

	sock_init();

	for (i = 0; def_nameservers[i]; i++) {
	struct ares_addr addr;

	addr.family = AF_INET;
	addr.addr.addr4.s_addr = htonl(def_nameservers[i]);

	status =
	ares_sconfig_append(channel, &sysconfig->sconfig, &addr, 0, 0, NULL);

	if (status != ARES_SUCCESS) {
	return status;
	}
	}

	return ARES_SUCCESS;
	}
	#endif

	#if defined(ANDROID) \|\| defined(__ANDROID__)
	static ares_status_t ares_init_sysconfig_android(const ares_channel_t *channel,
	ares_sysconfig_t *sysconfig)
	{
	size_t i;
	char **dns_servers;
	char *domains;
	size_t num_servers;
	ares_status_t status = ARES_EFILE;

	/* Use the Android connectivity manager to get a list
	* of DNS servers. As of Android 8 (Oreo) net.dns#
	* system properties are no longer available. Google claims this
	* improves privacy. Apps now need the ACCESS_NETWORK_STATE
	* permission and must use the ConnectivityManager which
	* is Java only. */
	dns_servers = ares_get_android_server_list(MAX_DNS_PROPERTIES, &num_servers);
	if (dns_servers != NULL) {
	for (i = 0; i < num_servers; i++) {
	status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig,
	dns_servers[i], ARES_TRUE);
	if (status != ARES_SUCCESS) {
	return status;
	}
	}
	for (i = 0; i < num_servers; i++) {
	ares_free(dns_servers[i]);
	}
	ares_free(dns_servers);
	}

	domains = ares_get_android_search_domains_list();
	sysconfig->domains = ares_strsplit(domains, ", ", &sysconfig->ndomains);
	ares_free(domains);

	# ifdef HAVE___SYSTEM_PROPERTY_GET
	/* Old way using the system property still in place as
	* a fallback. Older android versions can still use this.
	* it's possible for older apps not not have added the new
	* permission and we want to try to avoid breaking those.
	*
	* We'll only run this if we don't have any dns servers
	* because this will get the same ones (if it works). */
	if (sysconfig->sconfig == NULL) {
	char propname[PROP_NAME_MAX];
	char propvalue[PROP_VALUE_MAX] = "";
	for (i = 1; i <= MAX_DNS_PROPERTIES; i++) {
	snprintf(propname, sizeof(propname), "%s%zu", DNS_PROP_NAME_PREFIX, i);
	if (__system_property_get(propname, propvalue) < 1) {
	break;
	}
	status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig,
	propvalue, ARES_TRUE);
	if (status != ARES_SUCCESS) {
	return status;
	}
	}
	}
	# endif /* HAVE___SYSTEM_PROPERTY_GET */

	return status;
	}
	#endif

	#if defined(__QNX__)
	static ares_status_t
	ares_init_sysconfig_qnx(const ares_channel_t *channel,
	ares_sysconfig_t *sysconfig)
	{
	/* QNX:
	* 1. use confstr(_CS_RESOLVE, ...) as primary resolv.conf data, replacing
	* "_" with " ". If that is empty, then do normal /etc/resolv.conf
	* processing.
	* 2. We want to process /etc/nsswitch.conf as normal.
	* 3. if confstr(_CS_DOMAIN, ...) this is the domain name. Use this as
	* preference over anything else found.
	*/
	ares_buf_t *buf = ares_buf_create();
	unsigned char *data = NULL;
	size_t data_size = 0;
	ares_bool_t process_resolvconf = ARES_TRUE;
	ares_status_t status = ARES_SUCCESS;

	/* Prefer confstr(_CS_RESOLVE, ...) */
	buf = ares_buf_create();
	if (buf == NULL) {
	status = ARES_ENOMEM;
	goto done;
	}

	data_size = 1024;
	data = ares_buf_append_start(buf, &data_size);
	if (data == NULL) {
	status = ARES_ENOMEM;
	goto done;
	}

	data_size = confstr(_CS_RESOLVE, (char *)data, data_size);
	if (data_size > 1) {
	/* confstr returns byte for NULL terminator, strip */
	data_size--;

	ares_buf_append_finish(buf, data_size);
	/* Its odd, this uses _ instead of " " between keywords, otherwise the
	* format is the same as resolv.conf, replace. */
	ares_buf_replace(buf, (const unsigned char *)"_", 1,
	(const unsigned char *)" ", 1);

	status = ares_sysconfig_process_buf(channel, sysconfig, buf,
	ares_sysconfig_parse_resolv_line);
	if (status != ARES_SUCCESS) {
	/* ENOMEM is really the only error we'll get here */
	goto done;
	}

	/* don't read resolv.conf if we processed any nameservers */
	if (ares_llist_len(sysconfig->sconfig) != 0) {
	process_resolvconf = ARES_FALSE;
	}
	}

	/* Process files */
	status = ares_init_sysconfig_files(channel, sysconfig, process_resolvconf);
	if (status != ARES_SUCCESS) {
	goto done;
	}

	/* Read confstr(_CS_DOMAIN, ...), but if we had a search path specified with
	* more than one domain, lets prefer that instead. Its not exactly clear
	* the best way to handle this. */
	if (sysconfig->ndomains <= 1) {
	char domain[256];
	size_t domain_len;

	domain_len = confstr(_CS_DOMAIN, domain, sizeof(domain_len));
	if (domain_len != 0) {
	ares_strsplit_free(sysconfig->domains, sysconfig->ndomains);
	sysconfig->domains = ares_strsplit(domain, ", ", &sysconfig->ndomains);
	if (sysconfig->domains == NULL) {
	status = ARES_ENOMEM;
	goto done;
	}
	}
	}

	done:
	ares_buf_destroy(buf);

	return status;
	}
	#endif

	#if defined(CARES_USE_LIBRESOLV)
	static ares_status_t
	ares_init_sysconfig_libresolv(const ares_channel_t *channel,
	ares_sysconfig_t *sysconfig)
	{
	struct __res_state res;
	ares_status_t status = ARES_SUCCESS;
	union res_sockaddr_union addr[MAXNS];
	int nscount;
	size_t i;
	size_t entries = 0;
	ares_buf_t *ipbuf = NULL;

	memset(&res, 0, sizeof(res));

	if (res_ninit(&res) != 0 \|\| !(res.options & RES_INIT)) {
	return ARES_EFILE;
	}

	nscount = res_getservers(&res, addr, MAXNS);

	for (i = 0; i < (size_t)nscount; ++i) {
	char ipaddr[INET6_ADDRSTRLEN] = "";
	char *ipstr = NULL;
	unsigned short port = 0;
	unsigned int ll_scope = 0;

	sa_family_t family = addr[i].sin.sin_family;
	if (family == AF_INET) {
	ares_inet_ntop(family, &addr[i].sin.sin_addr, ipaddr, sizeof(ipaddr));
	port = ntohs(addr[i].sin.sin_port);
	} else if (family == AF_INET6) {
	ares_inet_ntop(family, &addr[i].sin6.sin6_addr, ipaddr, sizeof(ipaddr));
	port = ntohs(addr[i].sin6.sin6_port);
	ll_scope = addr[i].sin6.sin6_scope_id;
	} else {
	continue;
	}


	/* [ip]:port%iface */
	ipbuf = ares_buf_create();
	if (ipbuf == NULL) {
	status = ARES_ENOMEM;
	goto done;
	}

	status = ares_buf_append_str(ipbuf, "[");
	if (status != ARES_SUCCESS) {
	goto done;
	}

	status = ares_buf_append_str(ipbuf, ipaddr);
	if (status != ARES_SUCCESS) {
	goto done;
	}

	status = ares_buf_append_str(ipbuf, "]");
	if (status != ARES_SUCCESS) {
	goto done;
	}

	if (port) {
	status = ares_buf_append_str(ipbuf, ":");
	if (status != ARES_SUCCESS) {
	goto done;
	}
	status = ares_buf_append_num_dec(ipbuf, port, 0);
	if (status != ARES_SUCCESS) {
	goto done;
	}
	}

	if (ll_scope) {
	status = ares_buf_append_str(ipbuf, "%");
	if (status != ARES_SUCCESS) {
	goto done;
	}
	status = ares_buf_append_num_dec(ipbuf, ll_scope, 0);
	if (status != ARES_SUCCESS) {
	goto done;
	}
	}

	ipstr = ares_buf_finish_str(ipbuf, NULL);
	ipbuf = NULL;
	if (ipstr == NULL) {
	status = ARES_ENOMEM;
	goto done;
	}

	status = ares_sconfig_append_fromstr(channel, &sysconfig->sconfig, ipstr,
	ARES_TRUE);

	ares_free(ipstr);
	if (status != ARES_SUCCESS) {
	goto done;
	}
	}

	while ((entries < MAXDNSRCH) && res.dnsrch[entries]) {
	entries++;
	}

	if (entries) {
	sysconfig->domains = ares_malloc_zero(entries * sizeof(char *));
	if (sysconfig->domains == NULL) {
	status = ARES_ENOMEM;
	goto done;
	} else {
	sysconfig->ndomains = entries;
	for (i = 0; i < sysconfig->ndomains; i++) {
	sysconfig->domains[i] = ares_strdup(res.dnsrch[i]);
	if (sysconfig->domains[i] == NULL) {
	status = ARES_ENOMEM;
	goto done;
	}
	}
	}
	}

	if (res.ndots >= 0) {
	sysconfig->ndots = (size_t)res.ndots;
	}
	/* Apple does not allow configuration of retry, so this is a static dummy
	* value, ignore */
	# ifndef __APPLE__
	if (res.retry > 0) {
	sysconfig->tries = (size_t)res.retry;
	}
	# endif
	if (res.options & RES_ROTATE) {
	sysconfig->rotate = ARES_TRUE;
	}

	if (res.retrans > 0) {
	/* Apple does not allow configuration of retrans, so this is a dummy value
	* that is extremely high (5s) */
	# ifndef __APPLE__
	if (res.retrans > 0) {
	sysconfig->timeout_ms = (unsigned int)res.retrans * 1000;
	}
	# endif
	}

	done:
	ares_buf_destroy(ipbuf);
	res_ndestroy(&res);
	return status;
	}
	#endif

	static void ares_sysconfig_free(ares_sysconfig_t *sysconfig)
	{
	ares_llist_destroy(sysconfig->sconfig);
	ares_strsplit_free(sysconfig->domains, sysconfig->ndomains);
	ares_free(sysconfig->sortlist);
	ares_free(sysconfig->lookups);
	memset(sysconfig, 0, sizeof(*sysconfig));
	}

	static ares_status_t ares_sysconfig_apply(ares_channel_t *channel,
	const ares_sysconfig_t *sysconfig)
	{
	ares_status_t status;

	if (sysconfig->sconfig && !(channel->optmask & ARES_OPT_SERVERS)) {
	status = ares_servers_update(channel, sysconfig->sconfig, ARES_FALSE);
	if (status != ARES_SUCCESS) {
	return status;
	}
	}

	if (sysconfig->domains && !(channel->optmask & ARES_OPT_DOMAINS)) {
	/* Make sure we duplicate first then replace so even if there is
	* ARES_ENOMEM, the channel stays in a good state */
	char **temp =
	ares_strsplit_duplicate(sysconfig->domains, sysconfig->ndomains);
	if (temp == NULL) {
	return ARES_ENOMEM; /* LCOV_EXCL_LINE: OutOfMemory */
	}

	ares_strsplit_free(channel->domains, channel->ndomains);
	channel->domains = temp;
	channel->ndomains = sysconfig->ndomains;
	}

	if (sysconfig->lookups && !(channel->optmask & ARES_OPT_LOOKUPS)) {
	char *temp = ares_strdup(sysconfig->lookups);
	if (temp == NULL) {
	return ARES_ENOMEM; /* LCOV_EXCL_LINE: OutOfMemory */
	}

	ares_free(channel->lookups);
	channel->lookups = temp;
	}

	if (sysconfig->sortlist && !(channel->optmask & ARES_OPT_SORTLIST)) {
	struct apattern *temp =
	ares_malloc(sizeof(channel->sortlist) sysconfig->nsortlist);
	if (temp == NULL) {
	return ARES_ENOMEM; /* LCOV_EXCL_LINE: OutOfMemory */
	}
	memcpy(temp, sysconfig->sortlist,
	sizeof(channel->sortlist) sysconfig->nsortlist);

	ares_free(channel->sortlist);
	channel->sortlist = temp;
	channel->nsort = sysconfig->nsortlist;
	}

	if (!(channel->optmask & ARES_OPT_NDOTS)) {
	channel->ndots = sysconfig->ndots;
	}

	if (sysconfig->tries && !(channel->optmask & ARES_OPT_TRIES)) {
	channel->tries = sysconfig->tries;
	}

	if (sysconfig->timeout_ms && !(channel->optmask & ARES_OPT_TIMEOUTMS)) {
	channel->timeout = sysconfig->timeout_ms;
	}

	if (!(channel->optmask & (ARES_OPT_ROTATE \| ARES_OPT_NOROTATE))) {
	channel->rotate = sysconfig->rotate;
	}

	if (sysconfig->usevc) {
	channel->flags \|= ARES_FLAG_USEVC;
	}

	return ARES_SUCCESS;
	}

	ares_status_t ares_init_by_sysconfig(ares_channel_t *channel)
	{
	ares_status_t status;
	ares_sysconfig_t sysconfig;

	memset(&sysconfig, 0, sizeof(sysconfig));
	sysconfig.ndots = 1; /* Default value if not otherwise set */

	#if defined(USE_WINSOCK)
	status = ares_init_sysconfig_windows(channel, &sysconfig);
	#elif defined(__MVS__)
	status = ares_init_sysconfig_mvs(channel, &sysconfig);
	#elif defined(__riscos__)
	status = ares_init_sysconfig_riscos(channel, &sysconfig);
	#elif defined(WATT32)
	status = ares_init_sysconfig_watt32(channel, &sysconfig);
	#elif defined(ANDROID) \|\| defined(__ANDROID__)
	status = ares_init_sysconfig_android(channel, &sysconfig);
	#elif defined(__APPLE__)
	status = ares_init_sysconfig_macos(channel, &sysconfig);
	#elif defined(CARES_USE_LIBRESOLV)
	status = ares_init_sysconfig_libresolv(channel, &sysconfig);
	#elif defined(__QNX__)
	status = ares_init_sysconfig_qnx(channel, &sysconfig);
	#else
	status = ares_init_sysconfig_files(channel, &sysconfig, ARES_TRUE);
	#endif

	if (status != ARES_SUCCESS) {
	goto done;
	}

	/* Environment is supposed to override sysconfig */
	status = ares_init_by_environment(&sysconfig);
	if (status != ARES_SUCCESS) {
	goto done;
	}

	/* Lock when applying the configuration to the channel. Don't need to
	* lock prior to this. */

	ares_channel_lock(channel);

	status = ares_sysconfig_apply(channel, &sysconfig);
	ares_channel_unlock(channel);

	if (status != ARES_SUCCESS) {
	goto done;
	}

	done:
	ares_sysconfig_free(&sysconfig);

	return status;
	}