text: /*
   * libwebsockets - small server side websockets and web server implementation
   *
   * Copyright (C) 2010 - 2019 Andy Green <andy@warmcat.com>
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy
   * of this software and associated documentation files (the "Software"), to
   * deal in the Software without restriction, including without limitation the
   * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
   * sell copies of the Software, and to permit persons to whom the Software is
   * furnished to do so, subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in
   * all copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
   * IN THE SOFTWARE.
   */
  
  
  #define DNS_MAX			96	/* Maximum host name		*/
  #define DNS_RECURSION_LIMIT	3
  #define DNS_PACKET_LEN		1400	/* Buffer size for DNS packet	*/
  #define MAX_CACHE_ENTRIES	10	/* Dont cache more than that	*/
  #define DNS_QUERY_TIMEOUT	30	/* Query timeout, seconds	*/
  
  #if defined(LWS_WITH_SYS_ASYNC_DNS)
  
  /*
   * ... when we completed a query then the query object is destroyed and a
   * cache object below is created with the results in getaddrinfo format
   * appended to the allocation
   */
  
  typedef struct lws_adns_cache {
  	lws_sorted_usec_list_t	sul;	/* for cache TTL management */
  	lws_dll2_t		list;
  
  	struct lws_adns_cache	*firstcache;
  	struct lws_adns_cache	*chain;
  	struct addrinfo		*results;
  	const char		*name;
  	uint8_t			flags;	/* b0 = has ipv4, b1 = has ipv6 */
  	char			refcount;
  	char			incomplete;
  	/* addrinfo, lws_sa46, then name overallocated here */
  } lws_adns_cache_t;
  
  /*
   * these objects are used while a query is ongoing...
   */
  
  typedef struct lws_adns_q {
  	lws_sorted_usec_list_t	sul;	/* per-query write retry timer */
  	lws_sorted_usec_list_t	write_sul;	/* fail if unable to write by this time */
  	lws_dll2_t		list;
  
  	lws_metrics_caliper_compose(metcal)
  
  	lws_dll2_owner_t	wsi_adns;
  	lws_async_dns_cb_t	standalone_cb;	/* if not associated to wsi */
  	struct lws_context	*context;
  	void			*opaque;
  	struct addrinfo		**last;
  	lws_async_dns_t		*dns;
  	lws_async_dns_server_t	*dsrv;
  
  	lws_adns_cache_t	*firstcache;
  
  	lws_async_dns_retcode_t	ret;
  	uint16_t		tid[3]; /* last 3 sent tid */
  	uint16_t		qtype;
  	uint16_t		retry;
  	uint8_t			tsi;
  
  #if defined(LWS_WITH_IPV6)
  	uint8_t			sent[2];
  #else
  	uint8_t			sent[1];
  #endif
  	uint8_t			asked;
  	uint8_t			responded;
  
  	uint8_t			recursion;
  	uint8_t			tids;
  	uint8_t			go_nogo;
  
  	uint8_t			is_retry:1;
  	uint8_t			is_synthetic:1; /* test will deliver canned */
  
  	/* name overallocated here */
  } lws_adns_q_t;
  
  #define LADNS_MOST_RECENT_TID(_q) \
  		q->tid[(int)(_q->tids - 1) % (int)LWS_ARRAY_SIZE(q->tid)]
  
  enum {
  	DHO_TID,
  	DHO_FLAGS = 2,
  	DHO_NQUERIES = 4,
  	DHO_NANSWERS = 6,
  	DHO_NAUTH = 8,
  	DHO_NOTHER = 10,
  
  	DHO_SIZEOF = 12 /* last */
  };
  
  void
  lws_adns_q_destroy(lws_adns_q_t *q);
  
  void
  sul_cb_expire(struct lws_sorted_usec_list *sul);
  
  void
  lws_adns_cache_destroy(lws_adns_cache_t *c);
  
  int
  lws_async_dns_complete(lws_adns_q_t *q, lws_adns_cache_t *c);
  
  lws_adns_cache_t *
  lws_adns_get_cache(lws_async_dns_t *dns, const char *name);
  
  lws_adns_q_t *
  lws_adns_get_query(lws_async_dns_t *dns, adns_query_type_t qtype,
  		   uint16_t tid, const char *name);
  
  lws_adns_q_t *
  lws_adns_get_query_srv(lws_async_dns_server_t *dsrv, adns_query_type_t qtype,
  		       uint16_t tid, const char *name);
  
  void
  lws_async_dns_trim_cache(lws_async_dns_t *dns);
  
  int
  lws_async_dns_get_new_tid(struct lws_context *context, lws_adns_q_t *q);
  
  
  
  /* require: context lock on this set */
  
  lws_async_dns_server_t *
  __lws_async_dns_server_find(lws_async_dns_t *dns, const lws_sockaddr46 *sa46);
  lws_async_dns_server_t *
  __lws_async_dns_server_find_wsi(lws_async_dns_t *dns, struct lws *wsi);
  lws_async_dns_server_t *
  __lws_async_dns_server_add(lws_async_dns_t *dns, const lws_sockaddr46 *sa46);
  void
  __lws_async_dns_server_remove(lws_async_dns_t *dns, const lws_sockaddr46 *sa46);
  
  
  #if defined(_DEBUG)
  void
  lws_adns_dump(lws_async_dns_t *dns);
  #else
  #define lws_adns_dump(_d)
  #endif
  
  #endif
  
  