unbound/iterator/iterator.h

   1 /*
   2  * iterator/iterator.h - iterative resolver DNS query response module
   3  *
   4  * Copyright (c) 2007, NLnet Labs. All rights reserved.
   5  *
   6  * This software is open source.
   7  *
   8  * Redistribution and use in source and binary forms, with or without
   9  * modification, are permitted provided that the following conditions
  10  * are met:
  11  *
  12  * Redistributions of source code must retain the above copyright notice,
  13  * this list of conditions and the following disclaimer.
  14  *
  15  * Redistributions in binary form must reproduce the above copyright notice,
  16  * this list of conditions and the following disclaimer in the documentation
  17  * and/or other materials provided with the distribution.
  18  *
  19  * Neither the name of the NLNET LABS nor the names of its contributors may
  20  * be used to endorse or promote products derived from this software without
  21  * specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  24  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  25  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  26  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  27  * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  28  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
  29  * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  30  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  31  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  32  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  33  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  34  */
  35
  36 /**
  37  * \file
  38  *
  39  * This file contains a module that performs recusive iterative DNS query
  40  * processing.
  41  */
  42
  43 #ifndef ITERATOR_ITERATOR_H
  44 #define ITERATOR_ITERATOR_H
  45 #include "services/outbound_list.h"
  46 #include "util/data/msgreply.h"
  47 #include "util/module.h"
  48 struct delegpt;
  49 struct iter_hints;
  50 struct iter_forwards;
  51 struct iter_donotq;
  52 struct iter_prep_list;
  53 struct iter_priv;
  54
  55 /** max number of targets spawned for a query and its subqueries */
  56 #define MAX_TARGET_COUNT        32
  57 /** max number of query restarts. Determines max number of CNAME chain. */
  58 #define MAX_RESTART_COUNT       8
  59 /** max number of referrals. Makes sure resolver does not run away */
  60 #define MAX_REFERRAL_COUNT      130
  61 /** max number of queries-sent-out.  Make sure large NS set does not loop */
  62 #define MAX_SENT_COUNT          32
  63 /** at what query-sent-count to stop target fetch policy */
  64 #define TARGET_FETCH_STOP       3
  65 /** how nice is a server without further information, in msec
  66  * Equals rtt initial timeout value.
  67  */
  68 #define UNKNOWN_SERVER_NICENESS 376
  69 /** maximum timeout before a host is deemed unsuitable, in msec.
  70  * After host_ttl this will be timed out and the host will be tried again.
  71  * Equals RTT_MAX_TIMEOUT
  72  */
  73 #define USEFUL_SERVER_TOP_TIMEOUT       120000
  74 /** number of retries on outgoing queries */
  75 #define OUTBOUND_MSG_RETRY 5
  76 /** RTT band, within this amount from the best, servers are chosen randomly.
  77  * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a
  78  * fast server, this causes server exploration as a side benefit. msec. */
  79 #define RTT_BAND 400
  80 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */
  81 #define INFRA_BACKOFF_INITIAL 240
  82
  83 /**
  84  * Global state for the iterator.
  85  */
  86 struct iter_env {
  87         /** A flag to indicate whether or not we have an IPv6 route */
  88         int supports_ipv6;
  89
  90         /** A flag to indicate whether or not we have an IPv4 route */
  91         int supports_ipv4;
  92
  93         /** A set of inetaddrs that should never be queried. */
  94         struct iter_donotq* donotq;
  95
  96         /** private address space and private domains */
  97         struct iter_priv* priv;
  98
  99         /** The maximum dependency depth that this resolver will pursue. */
 100         int max_dependency_depth;
 101
 102         /**
 103          * The target fetch policy for each dependency level. This is
 104          * described as a simple number (per dependency level):
 105          *      negative numbers (usually just -1) mean fetch-all,
 106          *      0 means only fetch on demand, and
 107          *      positive numbers mean to fetch at most that many targets.
 108          * array of max_dependency_depth+1 size.
 109          */
 110         int* target_fetch_policy;
 111 };
 112
 113 /**
 114  * State of the iterator for a query.
 115  */
 116 enum iter_state {
 117         /**
 118          * Externally generated queries start at this state. Query restarts are
 119          * reset to this state.
 120          */
 121         INIT_REQUEST_STATE = 0,
 122
 123         /**
 124          * Root priming events reactivate here, most other events pass
 125          * through this naturally as the 2nd part of the INIT_REQUEST_STATE.
 126          */
 127         INIT_REQUEST_2_STATE,
 128
 129         /**
 130          * Stub priming events reactivate here, most other events pass
 131          * through this naturally as the 3rd part of the INIT_REQUEST_STATE.
 132          */
 133         INIT_REQUEST_3_STATE,
 134
 135         /**
 136          * Each time a delegation point changes for a given query or a
 137          * query times out and/or wakes up, this state is (re)visited.
 138          * This state is reponsible for iterating through a list of
 139          * nameserver targets.
 140          */
 141         QUERYTARGETS_STATE,
 142
 143         /**
 144          * Responses to queries start at this state. This state handles
 145          * the decision tree associated with handling responses.
 146          */
 147         QUERY_RESP_STATE,
 148
 149         /** Responses to priming queries finish at this state. */
 150         PRIME_RESP_STATE,
 151
 152         /** Collecting query class information, for qclass=ANY, when
 153          * it spawns off queries for every class, it returns here. */
 154         COLLECT_CLASS_STATE,
 155
 156         /** Find NS record to resolve DS record from, walking to the right
 157          * NS spot until we find it */
 158         DSNS_FIND_STATE,
 159
 160         /** Responses that are to be returned upstream end at this state.
 161          * As well as responses to target queries. */
 162         FINISHED_STATE
 163 };
 164
 165 /**
 166  * Per query state for the iterator module.
 167  */
 168 struct iter_qstate {
 169         /**
 170          * State of the iterator module.
 171          * This is the state that event is in or should sent to -- all
 172          * requests should start with the INIT_REQUEST_STATE. All
 173          * responses should start with QUERY_RESP_STATE. Subsequent
 174          * processing of the event will change this state.
 175          */
 176         enum iter_state state;
 177
 178         /**
 179          * Final state for the iterator module.
 180          * This is the state that responses should be routed to once the
 181          * response is final. For externally initiated queries, this
 182          * will be FINISHED_STATE, locally initiated queries will have
 183          * different final states.
 184          */
 185         enum iter_state final_state;
 186
 187         /**
 188          * The depth of this query, this means the depth of recursion.
 189          * This address is needed for another query, which is an address
 190          * needed for another query, etc. Original client query has depth 0.
 191          */
 192         int depth;
 193
 194         /**
 195          * The response
 196          */
 197         struct dns_msg* response;
 198
 199         /**
 200          * This is a list of RRsets that must be prepended to the
 201          * ANSWER section of a response before being sent upstream.
 202          */
 203         struct iter_prep_list* an_prepend_list;
 204         /** Last element of the prepend list */
 205         struct iter_prep_list* an_prepend_last;
 206
 207         /**
 208          * This is the list of RRsets that must be prepended to the
 209          * AUTHORITY section of the response before being sent upstream.
 210          */
 211         struct iter_prep_list* ns_prepend_list;
 212         /** Last element of the authority prepend list */
 213         struct iter_prep_list* ns_prepend_last;
 214
 215         /** query name used for chasing the results. Initially the same as
 216          * the state qinfo, but after CNAMEs this will be different.
 217          * The query info used to elicit the results needed. */
 218         struct query_info qchase;
 219         /** query flags to use when chasing the answer (i.e. RD flag) */
 220         uint16_t chase_flags;
 221         /** true if we set RD bit because of last resort recursion lame query*/
 222         int chase_to_rd;
 223
 224         /**
 225          * This is the current delegation point for an in-progress query. This
 226          * object retains state as to which delegation targets need to be
 227          * (sub)queried for vs which ones have already been visited.
 228          */
 229         struct delegpt* dp;
 230
 231         /** state for 0x20 fallback when capsfail happens, 0 not a fallback */
 232         int caps_fallback;
 233         /** state for capsfail: current server number to try */
 234         size_t caps_server;
 235         /** state for capsfail: stored query for comparisons. Can be NULL if
 236          * no response had been seen prior to starting the fallback. */
 237         struct reply_info* caps_reply;
 238
 239         /** Current delegation message - returned for non-RD queries */
 240         struct dns_msg* deleg_msg;
 241
 242         /** number of outstanding target sub queries */
 243         int num_target_queries;
 244
 245         /** outstanding direct queries */
 246         int num_current_queries;
 247
 248         /** the number of times this query has been restarted. */
 249         int query_restart_count;
 250
 251         /** the number of times this query as followed a referral. */
 252         int referral_count;
 253
 254         /** number of queries fired off */
 255         int sent_count;
 256
 257         /** number of target queries spawned in [1], for this query and its
 258          * subqueries, the malloced-array is shared, [0] refcount. */
 259         int* target_count;
 260
 261         /**
 262          * The query must store NS records from referrals as parentside RRs
 263          * Enabled once it hits resolution problems, to throttle retries.
 264          * If enabled it is the pointer to the old delegation point with
 265          * the old retry counts for bad-nameserver-addresses.
 266          */
 267         struct delegpt* store_parent_NS;
 268
 269         /**
 270          * The query is for parent-side glue(A or AAAA) for a nameserver.
 271          * If the item is seen as glue in a referral, and pside_glue is NULL,
 272          * then it is stored in pside_glue for later.
 273          * If it was never seen, at the end, then a negative caching element
 274          * must be created.
 275          * The (data or negative) RR cache element then throttles retries.
 276          */
 277         int query_for_pside_glue;
 278         /** the parent-side-glue element (NULL if none, its first match) */
 279         struct ub_packed_rrset_key* pside_glue;
 280
 281         /** If nonNULL we are walking upwards from DS query to find NS */
 282         uint8_t* dsns_point;
 283         /** length of the dname in dsns_point */
 284         size_t dsns_point_len;
 285
 286         /**
 287          * expected dnssec information for this iteration step.
 288          * If dnssec rrsigs are expected and not given, the server is marked
 289          * lame (dnssec-lame).
 290          */
 291         int dnssec_expected;
 292
 293         /**
 294          * We are expecting dnssec information, but we also know the server
 295          * is DNSSEC lame.  The response need not be marked dnssec-lame again.
 296          */
 297         int dnssec_lame_query;
 298
 299         /**
 300          * This is flag that, if true, means that this event is
 301          * waiting for a stub priming query.
 302          */
 303         int wait_priming_stub;
 304
 305         /**
 306          * This is a flag that, if true, means that this query is
 307          * for (re)fetching glue from a zone. Since the address should
 308          * have been glue, query again to the servers that should have
 309          * been returning it as glue.
 310          * The delegation point must be set to the one that should *not*
 311          * be used when creating the state. A higher one will be attempted.
 312          */
 313         int refetch_glue;
 314
 315         /** list of pending queries to authoritative servers. */
 316         struct outbound_list outlist;
 317 };
 318
 319 /**
 320  * List of prepend items
 321  */
 322 struct iter_prep_list {
 323         /** next in list */
 324         struct iter_prep_list* next;
 325         /** rrset */
 326         struct ub_packed_rrset_key* rrset;
 327 };
 328
 329 /**
 330  * Get the iterator function block.
 331  * @return: function block with function pointers to iterator methods.
 332  */
 333 struct module_func_block* iter_get_funcblock(void);
 334
 335 /**
 336  * Get iterator state as a string
 337  * @param state: to convert
 338  * @return constant string that is printable.
 339  */
 340 const char* iter_state_to_string(enum iter_state state);
 341
 342 /**
 343  * See if iterator state is a response state
 344  * @param s: to inspect
 345  * @return true if response state.
 346  */
 347 int iter_state_is_responsestate(enum iter_state s);
 348
 349 /** iterator init */
 350 int iter_init(struct module_env* env, int id);
 351
 352 /** iterator deinit */
 353 void iter_deinit(struct module_env* env, int id);
 354
 355 /** iterator operate on a query */
 356 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id,
 357         struct outbound_entry* outbound);
 358
 359 /**
 360  * Return priming query results to interestes super querystates.
 361  *
 362  * Sets the delegation point and delegation message (not nonRD queries).
 363  * This is a callback from walk_supers.
 364  *
 365  * @param qstate: query state that finished.
 366  * @param id: module id.
 367  * @param super: the qstate to inform.
 368  */
 369 void iter_inform_super(struct module_qstate* qstate, int id,
 370         struct module_qstate* super);
 371
 372 /** iterator cleanup query state */
 373 void iter_clear(struct module_qstate* qstate, int id);
 374
 375 /** iterator alloc size routine */
 376 size_t iter_get_mem(struct module_env* env, int id);
 377
 378 #endif /* ITERATOR_ITERATOR_H */