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 recursive 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 struct rbtree_type; 55 56 /** max number of targets spawned for a query and its subqueries */ 57 #define MAX_TARGET_COUNT 64 58 /** max number of target lookups per qstate, per delegation point */ 59 #define MAX_DP_TARGET_COUNT 16 60 /** max number of nxdomains allowed for target lookups for a query and 61 * its subqueries */ 62 #define MAX_TARGET_NX 5 63 /** max number of query restarts. Determines max number of CNAME chain. */ 64 #define MAX_RESTART_COUNT 11 65 /** max number of referrals. Makes sure resolver does not run away */ 66 #define MAX_REFERRAL_COUNT 130 67 /** max number of queries-sent-out. Make sure large NS set does not loop */ 68 #define MAX_SENT_COUNT 32 69 /** max number of queries for which to perform dnsseclameness detection, 70 * (rrsigs missing detection) after that, just pick up that response */ 71 #define DNSSEC_LAME_DETECT_COUNT 4 72 /** 73 * max number of QNAME minimisation iterations. Limits number of queries for 74 * QNAMEs with a lot of labels. 75 */ 76 #define MAX_MINIMISE_COUNT 10 77 /* max number of time-outs for minimised query. Prevents resolving failures 78 * when the QNAME minimisation QTYPE is blocked. */ 79 #define MAX_MINIMISE_TIMEOUT_COUNT 3 80 /** 81 * number of labels from QNAME that are always send individually when using 82 * QNAME minimisation, even when the number of labels of the QNAME is bigger 83 * tham MAX_MINIMISE_COUNT */ 84 #define MINIMISE_ONE_LAB 4 85 #define MINIMISE_MULTIPLE_LABS (MAX_MINIMISE_COUNT - MINIMISE_ONE_LAB) 86 /** at what query-sent-count to stop target fetch policy */ 87 #define TARGET_FETCH_STOP 3 88 /** how nice is a server without further information, in msec 89 * Equals rtt initial timeout value. 90 */ 91 extern int UNKNOWN_SERVER_NICENESS; 92 /** maximum timeout before a host is deemed unsuitable, in msec. 93 * After host_ttl this will be timed out and the host will be tried again. 94 * Equals RTT_MAX_TIMEOUT 95 */ 96 #define USEFUL_SERVER_TOP_TIMEOUT 120000 97 /** number of retries on outgoing queries */ 98 #define OUTBOUND_MSG_RETRY 5 99 /** RTT band, within this amount from the best, servers are chosen randomly. 100 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 101 * fast server, this causes server exploration as a side benefit. msec. */ 102 #define RTT_BAND 400 103 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */ 104 #define INFRA_BACKOFF_INITIAL 240 105 106 /** 107 * Global state for the iterator. 108 */ 109 struct iter_env { 110 /** A flag to indicate whether or not we have an IPv6 route */ 111 int supports_ipv6; 112 113 /** A flag to indicate whether or not we have an IPv4 route */ 114 int supports_ipv4; 115 116 /** A set of inetaddrs that should never be queried. */ 117 struct iter_donotq* donotq; 118 119 /** private address space and private domains */ 120 struct iter_priv* priv; 121 122 /** whitelist for capsforid names */ 123 struct rbtree_type* caps_white; 124 125 /** The maximum dependency depth that this resolver will pursue. */ 126 int max_dependency_depth; 127 128 /** 129 * The target fetch policy for each dependency level. This is 130 * described as a simple number (per dependency level): 131 * negative numbers (usually just -1) mean fetch-all, 132 * 0 means only fetch on demand, and 133 * positive numbers mean to fetch at most that many targets. 134 * array of max_dependency_depth+1 size. 135 */ 136 int* target_fetch_policy; 137 138 /** lock on ratelimit counter */ 139 lock_basic_type queries_ratelimit_lock; 140 /** number of queries that have been ratelimited */ 141 size_t num_queries_ratelimited; 142 }; 143 144 /** 145 * QNAME minimisation state 146 */ 147 enum minimisation_state { 148 /** 149 * (Re)start minimisation. Outgoing QNAME should be set to dp->name. 150 * State entered on new query or after following referral or CNAME. 151 */ 152 INIT_MINIMISE_STATE = 0, 153 /** 154 * QNAME minimisation ongoing. Increase QNAME on every iteration. 155 */ 156 MINIMISE_STATE, 157 /** 158 * Don't increment QNAME this iteration 159 */ 160 SKIP_MINIMISE_STATE, 161 /** 162 * Send out full QNAME + original QTYPE 163 */ 164 DONOT_MINIMISE_STATE, 165 }; 166 167 /** 168 * State of the iterator for a query. 169 */ 170 enum iter_state { 171 /** 172 * Externally generated queries start at this state. Query restarts are 173 * reset to this state. 174 */ 175 INIT_REQUEST_STATE = 0, 176 177 /** 178 * Root priming events reactivate here, most other events pass 179 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 180 */ 181 INIT_REQUEST_2_STATE, 182 183 /** 184 * Stub priming events reactivate here, most other events pass 185 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 186 */ 187 INIT_REQUEST_3_STATE, 188 189 /** 190 * Each time a delegation point changes for a given query or a 191 * query times out and/or wakes up, this state is (re)visited. 192 * This state is responsible for iterating through a list of 193 * nameserver targets. 194 */ 195 QUERYTARGETS_STATE, 196 197 /** 198 * Responses to queries start at this state. This state handles 199 * the decision tree associated with handling responses. 200 */ 201 QUERY_RESP_STATE, 202 203 /** Responses to priming queries finish at this state. */ 204 PRIME_RESP_STATE, 205 206 /** Collecting query class information, for qclass=ANY, when 207 * it spawns off queries for every class, it returns here. */ 208 COLLECT_CLASS_STATE, 209 210 /** Find NS record to resolve DS record from, walking to the right 211 * NS spot until we find it */ 212 DSNS_FIND_STATE, 213 214 /** Responses that are to be returned upstream end at this state. 215 * As well as responses to target queries. */ 216 FINISHED_STATE 217 }; 218 219 /** 220 * Per query state for the iterator module. 221 */ 222 struct iter_qstate { 223 /** 224 * State of the iterator module. 225 * This is the state that event is in or should sent to -- all 226 * requests should start with the INIT_REQUEST_STATE. All 227 * responses should start with QUERY_RESP_STATE. Subsequent 228 * processing of the event will change this state. 229 */ 230 enum iter_state state; 231 232 /** 233 * Final state for the iterator module. 234 * This is the state that responses should be routed to once the 235 * response is final. For externally initiated queries, this 236 * will be FINISHED_STATE, locally initiated queries will have 237 * different final states. 238 */ 239 enum iter_state final_state; 240 241 /** 242 * The depth of this query, this means the depth of recursion. 243 * This address is needed for another query, which is an address 244 * needed for another query, etc. Original client query has depth 0. 245 */ 246 int depth; 247 248 /** 249 * The response 250 */ 251 struct dns_msg* response; 252 253 /** 254 * This is a list of RRsets that must be prepended to the 255 * ANSWER section of a response before being sent upstream. 256 */ 257 struct iter_prep_list* an_prepend_list; 258 /** Last element of the prepend list */ 259 struct iter_prep_list* an_prepend_last; 260 261 /** 262 * This is the list of RRsets that must be prepended to the 263 * AUTHORITY section of the response before being sent upstream. 264 */ 265 struct iter_prep_list* ns_prepend_list; 266 /** Last element of the authority prepend list */ 267 struct iter_prep_list* ns_prepend_last; 268 269 /** query name used for chasing the results. Initially the same as 270 * the state qinfo, but after CNAMEs this will be different. 271 * The query info used to elicit the results needed. */ 272 struct query_info qchase; 273 /** query flags to use when chasing the answer (i.e. RD flag) */ 274 uint16_t chase_flags; 275 /** true if we set RD bit because of last resort recursion lame query*/ 276 int chase_to_rd; 277 278 /** 279 * This is the current delegation point for an in-progress query. This 280 * object retains state as to which delegation targets need to be 281 * (sub)queried for vs which ones have already been visited. 282 */ 283 struct delegpt* dp; 284 285 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 286 int caps_fallback; 287 /** state for capsfail: current server number to try */ 288 size_t caps_server; 289 /** state for capsfail: stored query for comparisons. Can be NULL if 290 * no response had been seen prior to starting the fallback. */ 291 struct reply_info* caps_reply; 292 struct dns_msg* caps_response; 293 294 /** Current delegation message - returned for non-RD queries */ 295 struct dns_msg* deleg_msg; 296 297 /** number of outstanding target sub queries */ 298 int num_target_queries; 299 300 /** outstanding direct queries */ 301 int num_current_queries; 302 303 /** the number of times this query has been restarted. */ 304 int query_restart_count; 305 306 /** the number of times this query as followed a referral. */ 307 int referral_count; 308 309 /** number of queries fired off */ 310 int sent_count; 311 312 /** number of target queries spawned in [1], for this query and its 313 * subqueries, the malloced-array is shared, [0] refcount. 314 * in [2] the number of nxdomains is counted. */ 315 int* target_count; 316 317 /** number of target lookups per delegation point. Reset to 0 after 318 * receiving referral answer. Not shared with subqueries. */ 319 int dp_target_count; 320 321 /** if true, already tested for ratelimiting and passed the test */ 322 int ratelimit_ok; 323 324 /** 325 * The query must store NS records from referrals as parentside RRs 326 * Enabled once it hits resolution problems, to throttle retries. 327 * If enabled it is the pointer to the old delegation point with 328 * the old retry counts for bad-nameserver-addresses. 329 */ 330 struct delegpt* store_parent_NS; 331 332 /** 333 * The query is for parent-side glue(A or AAAA) for a nameserver. 334 * If the item is seen as glue in a referral, and pside_glue is NULL, 335 * then it is stored in pside_glue for later. 336 * If it was never seen, at the end, then a negative caching element 337 * must be created. 338 * The (data or negative) RR cache element then throttles retries. 339 */ 340 int query_for_pside_glue; 341 /** the parent-side-glue element (NULL if none, its first match) */ 342 struct ub_packed_rrset_key* pside_glue; 343 344 /** If nonNULL we are walking upwards from DS query to find NS */ 345 uint8_t* dsns_point; 346 /** length of the dname in dsns_point */ 347 size_t dsns_point_len; 348 349 /** 350 * expected dnssec information for this iteration step. 351 * If dnssec rrsigs are expected and not given, the server is marked 352 * lame (dnssec-lame). 353 */ 354 int dnssec_expected; 355 356 /** 357 * We are expecting dnssec information, but we also know the server 358 * is DNSSEC lame. The response need not be marked dnssec-lame again. 359 */ 360 int dnssec_lame_query; 361 362 /** 363 * This is flag that, if true, means that this event is 364 * waiting for a stub priming query. 365 */ 366 int wait_priming_stub; 367 368 /** 369 * This is a flag that, if true, means that this query is 370 * for (re)fetching glue from a zone. Since the address should 371 * have been glue, query again to the servers that should have 372 * been returning it as glue. 373 * The delegation point must be set to the one that should *not* 374 * be used when creating the state. A higher one will be attempted. 375 */ 376 int refetch_glue; 377 378 /** list of pending queries to authoritative servers. */ 379 struct outbound_list outlist; 380 381 /** QNAME minimisation state, RFC7816 */ 382 enum minimisation_state minimisation_state; 383 384 /** State for capsfail: QNAME minimisation state for comparisons. */ 385 enum minimisation_state caps_minimisation_state; 386 387 /** 388 * The query info that is sent upstream. Will be a subset of qchase 389 * when qname minimisation is enabled. 390 */ 391 struct query_info qinfo_out; 392 393 /** 394 * Count number of QNAME minimisation iterations. Used to limit number of 395 * outgoing queries when QNAME minimisation is enabled. 396 */ 397 int minimise_count; 398 399 /** 400 * Count number of time-outs. Used to prevent resolving failures when 401 * the QNAME minimisation QTYPE is blocked. Used to determine if 402 * capsforid fallback should be started.*/ 403 int timeout_count; 404 405 /** True if the current response is from auth_zone */ 406 int auth_zone_response; 407 /** True if the auth_zones should not be consulted for the query */ 408 int auth_zone_avoid; 409 /** true if there have been scrubbing failures of reply packets */ 410 int scrub_failures; 411 /** true if there have been parse failures of reply packets */ 412 int parse_failures; 413 /** a failure printout address for last received answer */ 414 struct comm_reply* fail_reply; 415 }; 416 417 /** 418 * List of prepend items 419 */ 420 struct iter_prep_list { 421 /** next in list */ 422 struct iter_prep_list* next; 423 /** rrset */ 424 struct ub_packed_rrset_key* rrset; 425 }; 426 427 /** 428 * Get the iterator function block. 429 * @return: function block with function pointers to iterator methods. 430 */ 431 struct module_func_block* iter_get_funcblock(void); 432 433 /** 434 * Get iterator state as a string 435 * @param state: to convert 436 * @return constant string that is printable. 437 */ 438 const char* iter_state_to_string(enum iter_state state); 439 440 /** 441 * See if iterator state is a response state 442 * @param s: to inspect 443 * @return true if response state. 444 */ 445 int iter_state_is_responsestate(enum iter_state s); 446 447 /** iterator init */ 448 int iter_init(struct module_env* env, int id); 449 450 /** iterator deinit */ 451 void iter_deinit(struct module_env* env, int id); 452 453 /** iterator operate on a query */ 454 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 455 struct outbound_entry* outbound); 456 457 /** 458 * Return priming query results to interested super querystates. 459 * 460 * Sets the delegation point and delegation message (not nonRD queries). 461 * This is a callback from walk_supers. 462 * 463 * @param qstate: query state that finished. 464 * @param id: module id. 465 * @param super: the qstate to inform. 466 */ 467 void iter_inform_super(struct module_qstate* qstate, int id, 468 struct module_qstate* super); 469 470 /** iterator cleanup query state */ 471 void iter_clear(struct module_qstate* qstate, int id); 472 473 /** iterator alloc size routine */ 474 size_t iter_get_mem(struct module_env* env, int id); 475 476 #endif /* ITERATOR_ITERATOR_H */ 477