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 nxdomains allowed for target lookups for a query and 64 * its subqueries when fallback has kicked in */ 65 #define MAX_TARGET_NX_FALLBACK (MAX_TARGET_NX*2) 66 /** max number of query restarts. Determines max number of CNAME chain. */ 67 #define MAX_RESTART_COUNT 11 68 /** max number of referrals. Makes sure resolver does not run away */ 69 #define MAX_REFERRAL_COUNT 130 70 /** max number of queries-sent-out. Make sure large NS set does not loop */ 71 #define MAX_SENT_COUNT 32 72 /** max number of queries for which to perform dnsseclameness detection, 73 * (rrsigs missing detection) after that, just pick up that response */ 74 #define DNSSEC_LAME_DETECT_COUNT 4 75 /** 76 * max number of QNAME minimisation iterations. Limits number of queries for 77 * QNAMEs with a lot of labels. 78 */ 79 #define MAX_MINIMISE_COUNT 10 80 /* max number of time-outs for minimised query. Prevents resolving failures 81 * when the QNAME minimisation QTYPE is blocked. */ 82 #define MAX_MINIMISE_TIMEOUT_COUNT 3 83 /** 84 * number of labels from QNAME that are always send individually when using 85 * QNAME minimisation, even when the number of labels of the QNAME is bigger 86 * than MAX_MINIMISE_COUNT */ 87 #define MINIMISE_ONE_LAB 4 88 #define MINIMISE_MULTIPLE_LABS (MAX_MINIMISE_COUNT - MINIMISE_ONE_LAB) 89 /** at what query-sent-count to stop target fetch policy */ 90 #define TARGET_FETCH_STOP 3 91 /** how nice is a server without further information, in msec 92 * Equals rtt initial timeout value. 93 */ 94 extern int UNKNOWN_SERVER_NICENESS; 95 /** maximum timeout before a host is deemed unsuitable, in msec. 96 * After host_ttl this will be timed out and the host will be tried again. 97 * Equals RTT_MAX_TIMEOUT, and thus when RTT_MAX_TIMEOUT is overwritten by 98 * config infra_cache_max_rtt, it will be overwritten as well. */ 99 extern int USEFUL_SERVER_TOP_TIMEOUT; 100 /** penalty to validation failed blacklisted IPs 101 * Equals USEFUL_SERVER_TOP_TIMEOUT*4, and thus when RTT_MAX_TIMEOUT is 102 * overwritten by config infra_cache_max_rtt, it will be overwritten as well. */ 103 extern int BLACKLIST_PENALTY; 104 /** RTT band, within this amount from the best, servers are chosen randomly. 105 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 106 * fast server, this causes server exploration as a side benefit. msec. */ 107 #define RTT_BAND 400 108 109 /** 110 * Global state for the iterator. 111 */ 112 struct iter_env { 113 /** A flag to indicate whether or not we have an IPv6 route */ 114 int supports_ipv6; 115 116 /** A flag to indicate whether or not we have an IPv4 route */ 117 int supports_ipv4; 118 119 /** A set of inetaddrs that should never be queried. */ 120 struct iter_donotq* donotq; 121 122 /** private address space and private domains */ 123 struct iter_priv* priv; 124 125 /** whitelist for capsforid names */ 126 struct rbtree_type* caps_white; 127 128 /** The maximum dependency depth that this resolver will pursue. */ 129 int max_dependency_depth; 130 131 /** 132 * The target fetch policy for each dependency level. This is 133 * described as a simple number (per dependency level): 134 * negative numbers (usually just -1) mean fetch-all, 135 * 0 means only fetch on demand, and 136 * positive numbers mean to fetch at most that many targets. 137 * array of max_dependency_depth+1 size. 138 */ 139 int* target_fetch_policy; 140 141 /** lock on ratelimit counter */ 142 lock_basic_type queries_ratelimit_lock; 143 /** number of queries that have been ratelimited */ 144 size_t num_queries_ratelimited; 145 146 /** number of retries on outgoing queries */ 147 int outbound_msg_retry; 148 }; 149 150 /** 151 * QNAME minimisation state 152 */ 153 enum minimisation_state { 154 /** 155 * (Re)start minimisation. Outgoing QNAME should be set to dp->name. 156 * State entered on new query or after following referral or CNAME. 157 */ 158 INIT_MINIMISE_STATE = 0, 159 /** 160 * QNAME minimisation ongoing. Increase QNAME on every iteration. 161 */ 162 MINIMISE_STATE, 163 /** 164 * Don't increment QNAME this iteration 165 */ 166 SKIP_MINIMISE_STATE, 167 /** 168 * Send out full QNAME + original QTYPE 169 */ 170 DONOT_MINIMISE_STATE, 171 }; 172 173 /** 174 * State of the iterator for a query. 175 */ 176 enum iter_state { 177 /** 178 * Externally generated queries start at this state. Query restarts are 179 * reset to this state. 180 */ 181 INIT_REQUEST_STATE = 0, 182 183 /** 184 * Root priming events reactivate here, most other events pass 185 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 186 */ 187 INIT_REQUEST_2_STATE, 188 189 /** 190 * Stub priming events reactivate here, most other events pass 191 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 192 */ 193 INIT_REQUEST_3_STATE, 194 195 /** 196 * Each time a delegation point changes for a given query or a 197 * query times out and/or wakes up, this state is (re)visited. 198 * This state is responsible for iterating through a list of 199 * nameserver targets. 200 */ 201 QUERYTARGETS_STATE, 202 203 /** 204 * Responses to queries start at this state. This state handles 205 * the decision tree associated with handling responses. 206 */ 207 QUERY_RESP_STATE, 208 209 /** Responses to priming queries finish at this state. */ 210 PRIME_RESP_STATE, 211 212 /** Collecting query class information, for qclass=ANY, when 213 * it spawns off queries for every class, it returns here. */ 214 COLLECT_CLASS_STATE, 215 216 /** Find NS record to resolve DS record from, walking to the right 217 * NS spot until we find it */ 218 DSNS_FIND_STATE, 219 220 /** Responses that are to be returned upstream end at this state. 221 * As well as responses to target queries. */ 222 FINISHED_STATE 223 }; 224 225 /** 226 * Shared counters for queries. 227 */ 228 enum target_count_variables { 229 /** Reference count for the shared iter_qstate->target_count. */ 230 TARGET_COUNT_REF = 0, 231 /** Number of target queries spawned for the query and subqueries. */ 232 TARGET_COUNT_QUERIES, 233 /** Number of nxdomain responses encountered. */ 234 TARGET_COUNT_NX, 235 236 /** This should stay last here, it is used for the allocation */ 237 TARGET_COUNT_MAX, 238 }; 239 240 /** 241 * Per query state for the iterator module. 242 */ 243 struct iter_qstate { 244 /** 245 * State of the iterator module. 246 * This is the state that event is in or should sent to -- all 247 * requests should start with the INIT_REQUEST_STATE. All 248 * responses should start with QUERY_RESP_STATE. Subsequent 249 * processing of the event will change this state. 250 */ 251 enum iter_state state; 252 253 /** 254 * Final state for the iterator module. 255 * This is the state that responses should be routed to once the 256 * response is final. For externally initiated queries, this 257 * will be FINISHED_STATE, locally initiated queries will have 258 * different final states. 259 */ 260 enum iter_state final_state; 261 262 /** 263 * The depth of this query, this means the depth of recursion. 264 * This address is needed for another query, which is an address 265 * needed for another query, etc. Original client query has depth 0. 266 */ 267 int depth; 268 269 /** 270 * The response 271 */ 272 struct dns_msg* response; 273 274 /** 275 * This is a list of RRsets that must be prepended to the 276 * ANSWER section of a response before being sent upstream. 277 */ 278 struct iter_prep_list* an_prepend_list; 279 /** Last element of the prepend list */ 280 struct iter_prep_list* an_prepend_last; 281 282 /** 283 * This is the list of RRsets that must be prepended to the 284 * AUTHORITY section of the response before being sent upstream. 285 */ 286 struct iter_prep_list* ns_prepend_list; 287 /** Last element of the authority prepend list */ 288 struct iter_prep_list* ns_prepend_last; 289 290 /** query name used for chasing the results. Initially the same as 291 * the state qinfo, but after CNAMEs this will be different. 292 * The query info used to elicit the results needed. */ 293 struct query_info qchase; 294 /** query flags to use when chasing the answer (i.e. RD flag) */ 295 uint16_t chase_flags; 296 /** true if we set RD bit because of last resort recursion lame query*/ 297 int chase_to_rd; 298 299 /** 300 * This is the current delegation point for an in-progress query. This 301 * object retains state as to which delegation targets need to be 302 * (sub)queried for vs which ones have already been visited. 303 */ 304 struct delegpt* dp; 305 306 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 307 int caps_fallback; 308 /** state for capsfail: current server number to try */ 309 size_t caps_server; 310 /** state for capsfail: stored query for comparisons. Can be NULL if 311 * no response had been seen prior to starting the fallback. */ 312 struct reply_info* caps_reply; 313 struct dns_msg* caps_response; 314 315 /** Current delegation message - returned for non-RD queries */ 316 struct dns_msg* deleg_msg; 317 318 /** number of outstanding target sub queries */ 319 int num_target_queries; 320 321 /** outstanding direct queries */ 322 int num_current_queries; 323 324 /** the number of times this query has been restarted. */ 325 int query_restart_count; 326 327 /** the number of times this query has followed a referral. */ 328 int referral_count; 329 330 /** number of queries fired off */ 331 int sent_count; 332 333 /** malloced-array shared with this query and its subqueries. It keeps 334 * track of the defined enum target_count_variables counters. */ 335 int* target_count; 336 337 /** number of target lookups per delegation point. Reset to 0 after 338 * receiving referral answer. Not shared with subqueries. */ 339 int dp_target_count; 340 341 /** Delegation point that triggered the NXNS fallback; shared with 342 * this query and its subqueries, count-referenced by the reference 343 * counter in target_count. 344 * This also marks the fallback activation. */ 345 uint8_t** nxns_dp; 346 347 /** if true, already tested for ratelimiting and passed the test */ 348 int ratelimit_ok; 349 350 /** 351 * The query must store NS records from referrals as parentside RRs 352 * Enabled once it hits resolution problems, to throttle retries. 353 * If enabled it is the pointer to the old delegation point with 354 * the old retry counts for bad-nameserver-addresses. 355 */ 356 struct delegpt* store_parent_NS; 357 358 /** 359 * The query is for parent-side glue(A or AAAA) for a nameserver. 360 * If the item is seen as glue in a referral, and pside_glue is NULL, 361 * then it is stored in pside_glue for later. 362 * If it was never seen, at the end, then a negative caching element 363 * must be created. 364 * The (data or negative) RR cache element then throttles retries. 365 */ 366 int query_for_pside_glue; 367 /** the parent-side-glue element (NULL if none, its first match) */ 368 struct ub_packed_rrset_key* pside_glue; 369 370 /** If nonNULL we are walking upwards from DS query to find NS */ 371 uint8_t* dsns_point; 372 /** length of the dname in dsns_point */ 373 size_t dsns_point_len; 374 375 /** 376 * expected dnssec information for this iteration step. 377 * If dnssec rrsigs are expected and not given, the server is marked 378 * lame (dnssec-lame). 379 */ 380 int dnssec_expected; 381 382 /** 383 * We are expecting dnssec information, but we also know the server 384 * is DNSSEC lame. The response need not be marked dnssec-lame again. 385 */ 386 int dnssec_lame_query; 387 388 /** 389 * This is flag that, if true, means that this event is 390 * waiting for a stub priming query. 391 */ 392 int wait_priming_stub; 393 394 /** 395 * This is a flag that, if true, means that this query is 396 * for (re)fetching glue from a zone. Since the address should 397 * have been glue, query again to the servers that should have 398 * been returning it as glue. 399 * The delegation point must be set to the one that should *not* 400 * be used when creating the state. A higher one will be attempted. 401 */ 402 int refetch_glue; 403 404 /** list of pending queries to authoritative servers. */ 405 struct outbound_list outlist; 406 407 /** QNAME minimisation state, RFC9156 */ 408 enum minimisation_state minimisation_state; 409 410 /** State for capsfail: QNAME minimisation state for comparisons. */ 411 enum minimisation_state caps_minimisation_state; 412 413 /** 414 * The query info that is sent upstream. Will be a subset of qchase 415 * when qname minimisation is enabled. 416 */ 417 struct query_info qinfo_out; 418 419 /** 420 * Count number of QNAME minimisation iterations. Used to limit number of 421 * outgoing queries when QNAME minimisation is enabled. 422 */ 423 int minimise_count; 424 425 /** 426 * Count number of time-outs. Used to prevent resolving failures when 427 * the QNAME minimisation QTYPE is blocked. Used to determine if 428 * capsforid fallback should be started.*/ 429 int timeout_count; 430 431 /** True if the current response is from auth_zone */ 432 int auth_zone_response; 433 /** True if the auth_zones should not be consulted for the query */ 434 int auth_zone_avoid; 435 /** true if there have been scrubbing failures of reply packets */ 436 int scrub_failures; 437 /** true if there have been parse failures of reply packets */ 438 int parse_failures; 439 /** a failure printout address for last received answer */ 440 struct comm_reply* fail_reply; 441 }; 442 443 /** 444 * List of prepend items 445 */ 446 struct iter_prep_list { 447 /** next in list */ 448 struct iter_prep_list* next; 449 /** rrset */ 450 struct ub_packed_rrset_key* rrset; 451 }; 452 453 /** 454 * Get the iterator function block. 455 * @return: function block with function pointers to iterator methods. 456 */ 457 struct module_func_block* iter_get_funcblock(void); 458 459 /** 460 * Get iterator state as a string 461 * @param state: to convert 462 * @return constant string that is printable. 463 */ 464 const char* iter_state_to_string(enum iter_state state); 465 466 /** 467 * See if iterator state is a response state 468 * @param s: to inspect 469 * @return true if response state. 470 */ 471 int iter_state_is_responsestate(enum iter_state s); 472 473 /** iterator init */ 474 int iter_init(struct module_env* env, int id); 475 476 /** iterator deinit */ 477 void iter_deinit(struct module_env* env, int id); 478 479 /** iterator operate on a query */ 480 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 481 struct outbound_entry* outbound); 482 483 /** 484 * Return priming query results to interested super querystates. 485 * 486 * Sets the delegation point and delegation message (not nonRD queries). 487 * This is a callback from walk_supers. 488 * 489 * @param qstate: query state that finished. 490 * @param id: module id. 491 * @param super: the qstate to inform. 492 */ 493 void iter_inform_super(struct module_qstate* qstate, int id, 494 struct module_qstate* super); 495 496 /** iterator cleanup query state */ 497 void iter_clear(struct module_qstate* qstate, int id); 498 499 /** iterator alloc size routine */ 500 size_t iter_get_mem(struct module_env* env, int id); 501 502 #endif /* ITERATOR_ITERATOR_H */ 503