src/or/dns_structs.h

   1 /* Copyright (c) 2003-2004, Roger Dingledine.
   2  * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
   3  * Copyright (c) 2007-2017, The Tor Project, Inc. */
   4 /* See LICENSE for licensing information */
   5
   6 /**
   7  * \file dns_structs.h
   8  *
   9  * \brief Structures used in dns.c. Exposed to dns.c, and to the unit tests
  10  * that declare DNS_PRIVATE.
  11  */
  12
  13 #ifndef TOR_DNS_STRUCTS_H
  14 #define TOR_DNS_STRUCTS_H
  15
  16 /** Longest hostname we're willing to resolve. */
  17 #define MAX_ADDRESSLEN 256
  18
  19 /** Linked list of connections waiting for a DNS answer. */
  20 typedef struct pending_connection_t {
  21   edge_connection_t *conn;
  22   struct pending_connection_t *next;
  23 } pending_connection_t;
  24
  25 /** Value of 'magic' field for cached_resolve_t.  Used to try to catch bad
  26  * pointers and memory stomping. */
  27 #define CACHED_RESOLVE_MAGIC 0x1234F00D
  28
  29 /* Possible states for a cached resolve_t */
  30 /** We are waiting for the resolver system to tell us an answer here.
  31  * When we get one, or when we time out, the state of this cached_resolve_t
  32  * will become "DONE" and we'll possibly add a CACHED
  33  * entry. This cached_resolve_t will be in the hash table so that we will
  34  * know not to launch more requests for this addr, but rather to add more
  35  * connections to the pending list for the addr. */
  36 #define CACHE_STATE_PENDING 0
  37 /** This used to be a pending cached_resolve_t, and we got an answer for it.
  38  * Now we're waiting for this cached_resolve_t to expire.  This should
  39  * have no pending connections, and should not appear in the hash table. */
  40 #define CACHE_STATE_DONE 1
  41 /** We are caching an answer for this address. This should have no pending
  42  * connections, and should appear in the hash table. */
  43 #define CACHE_STATE_CACHED 2
  44
  45 /** @name status values for a single DNS request.
  46  *
  47  * @{ */
  48 /** The DNS request is in progress. */
  49 #define RES_STATUS_INFLIGHT 1
  50 /** The DNS request finished and gave an answer */
  51 #define RES_STATUS_DONE_OK 2
  52 /** The DNS request finished and gave an error */
  53 #define RES_STATUS_DONE_ERR 3
  54 /**@}*/
  55
  56 /** A DNS request: possibly completed, possibly pending; cached_resolve
  57  * structs are stored at the OR side in a hash table, and as a linked
  58  * list from oldest to newest.
  59  */
  60 typedef struct cached_resolve_t {
  61   HT_ENTRY(cached_resolve_t) node;
  62   uint32_t magic;  /**< Must be CACHED_RESOLVE_MAGIC */
  63   char address[MAX_ADDRESSLEN]; /**< The hostname to be resolved. */
  64
  65   union {
  66     uint32_t addr_ipv4; /**< IPv4 addr for <b>address</b>, if successful.
  67                          * (In host order.) */
  68     int err_ipv4; /**< One of DNS_ERR_*, if IPv4 lookup failed. */
  69   } result_ipv4; /**< Outcome of IPv4 lookup */
  70   union {
  71     struct in6_addr addr_ipv6; /**< IPv6 addr for <b>address</b>, if
  72                                 * successful */
  73     int err_ipv6; /**< One of DNS_ERR_*, if IPv6 lookup failed. */
  74   } result_ipv6; /**< Outcome of IPv6 lookup, if any */
  75   union {
  76     char *hostname; /** A hostname, if PTR lookup happened successfully*/
  77     int err_hostname; /** One of DNS_ERR_*, if PTR lookup failed. */
  78   } result_ptr;
  79   /** @name Status fields
  80    *
  81    * These take one of the RES_STATUS_* values, depending on the state
  82    * of the corresponding lookup.
  83    *
  84    * @{ */
  85   unsigned int res_status_ipv4 : 2;
  86   unsigned int res_status_ipv6 : 2;
  87   unsigned int res_status_hostname : 2;
  88   /**@}*/
  89   uint8_t state; /**< Is this cached entry pending/done/informative? */
  90
  91   time_t expire; /**< Remove items from cache after this time. */
  92   uint32_t ttl_ipv4; /**< What TTL did the nameserver tell us? */
  93   uint32_t ttl_ipv6; /**< What TTL did the nameserver tell us? */
  94   uint32_t ttl_hostname; /**< What TTL did the nameserver tell us? */
  95   /** Connections that want to know when we get an answer for this resolve. */
  96   pending_connection_t *pending_connections;
  97   /** Position of this element in the heap*/
  98   int minheap_idx;
  99 } cached_resolve_t;
 100
 101 #endif /* !defined(TOR_DNS_STRUCTS_H) */
 102