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_donotq; 50 struct iter_prep_list; 51 struct iter_priv; 52 struct rbtree_type; 53 54 /** max number of targets spawned for a query and its subqueries */ 55 #define MAX_TARGET_COUNT 64 56 /** max number of upstream queries for a query and its subqueries, it is 57 * never reset. */ 58 extern int MAX_GLOBAL_QUOTA; 59 /** max number of target lookups per qstate, per delegation point */ 60 #define MAX_DP_TARGET_COUNT 16 61 /** max number of nxdomains allowed for target lookups for a query and 62 * its subqueries */ 63 #define MAX_TARGET_NX 5 64 /** max number of nxdomains allowed for target lookups for a query and 65 * its subqueries when fallback has kicked in */ 66 #define MAX_TARGET_NX_FALLBACK (MAX_TARGET_NX*2) 67 /** max number of referrals. Makes sure resolver does not run away */ 68 #define MAX_REFERRAL_COUNT 130 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 * than 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, and thus when RTT_MAX_TIMEOUT is overwritten by 95 * config infra_cache_max_rtt, it will be overwritten as well. */ 96 extern int USEFUL_SERVER_TOP_TIMEOUT; 97 /** penalty to validation failed blacklisted IPs 98 * Equals USEFUL_SERVER_TOP_TIMEOUT*4, and thus when RTT_MAX_TIMEOUT is 99 * overwritten by config infra_cache_max_rtt, it will be overwritten as well. */ 100 extern int BLACKLIST_PENALTY; 101 /** RTT band, within this amount from the best, servers are chosen randomly. 102 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 103 * fast server, this causes server exploration as a side benefit. msec. */ 104 #define RTT_BAND 400 105 /** Number of retries for empty nodata packets before it is accepted. */ 106 #define EMPTY_NODATA_RETRY_COUNT 2 107 108 /** 109 * Iterator global state for nat64. 110 */ 111 struct iter_nat64 { 112 /** A flag to locally apply NAT64 to make IPv4 addrs into IPv6 */ 113 int use_nat64; 114 115 /** NAT64 prefix address, cf. dns64_env->prefix_addr */ 116 struct sockaddr_storage nat64_prefix_addr; 117 118 /** sizeof(sockaddr_in6) */ 119 socklen_t nat64_prefix_addrlen; 120 121 /** CIDR mask length of NAT64 prefix */ 122 int nat64_prefix_net; 123 }; 124 125 /** 126 * Global state for the iterator. 127 */ 128 struct iter_env { 129 /** A flag to indicate whether or not we have an IPv6 route */ 130 int supports_ipv6; 131 132 /** A flag to indicate whether or not we have an IPv4 route */ 133 int supports_ipv4; 134 135 /** State for nat64 */ 136 struct iter_nat64 nat64; 137 138 /** A set of inetaddrs that should never be queried. */ 139 struct iter_donotq* donotq; 140 141 /** private address space and private domains */ 142 struct iter_priv* priv; 143 144 /** whitelist for capsforid names */ 145 struct rbtree_type* caps_white; 146 147 /** The maximum dependency depth that this resolver will pursue. */ 148 int max_dependency_depth; 149 150 /** 151 * The target fetch policy for each dependency level. This is 152 * described as a simple number (per dependency level): 153 * negative numbers (usually just -1) mean fetch-all, 154 * 0 means only fetch on demand, and 155 * positive numbers mean to fetch at most that many targets. 156 * array of max_dependency_depth+1 size. 157 */ 158 int* target_fetch_policy; 159 160 /** lock on ratelimit counter */ 161 lock_basic_type queries_ratelimit_lock; 162 /** number of queries that have been ratelimited */ 163 size_t num_queries_ratelimited; 164 165 /** number of retries on outgoing queries */ 166 int outbound_msg_retry; 167 168 /** number of queries_sent */ 169 int max_sent_count; 170 171 /** max number of query restarts to limit length of CNAME chain */ 172 int max_query_restarts; 173 }; 174 175 /** 176 * QNAME minimisation state 177 */ 178 enum minimisation_state { 179 /** 180 * (Re)start minimisation. Outgoing QNAME should be set to dp->name. 181 * State entered on new query or after following referral or CNAME. 182 */ 183 INIT_MINIMISE_STATE = 0, 184 /** 185 * QNAME minimisation ongoing. Increase QNAME on every iteration. 186 */ 187 MINIMISE_STATE, 188 /** 189 * Don't increment QNAME this iteration 190 */ 191 SKIP_MINIMISE_STATE, 192 /** 193 * Send out full QNAME + original QTYPE 194 */ 195 DONOT_MINIMISE_STATE, 196 }; 197 198 /** 199 * State of the iterator for a query. 200 */ 201 enum iter_state { 202 /** 203 * Externally generated queries start at this state. Query restarts are 204 * reset to this state. 205 */ 206 INIT_REQUEST_STATE = 0, 207 208 /** 209 * Root priming events reactivate here, most other events pass 210 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 211 */ 212 INIT_REQUEST_2_STATE, 213 214 /** 215 * Stub priming events reactivate here, most other events pass 216 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 217 */ 218 INIT_REQUEST_3_STATE, 219 220 /** 221 * Each time a delegation point changes for a given query or a 222 * query times out and/or wakes up, this state is (re)visited. 223 * This state is responsible for iterating through a list of 224 * nameserver targets. 225 */ 226 QUERYTARGETS_STATE, 227 228 /** 229 * Responses to queries start at this state. This state handles 230 * the decision tree associated with handling responses. 231 */ 232 QUERY_RESP_STATE, 233 234 /** Responses to priming queries finish at this state. */ 235 PRIME_RESP_STATE, 236 237 /** Collecting query class information, for qclass=ANY, when 238 * it spawns off queries for every class, it returns here. */ 239 COLLECT_CLASS_STATE, 240 241 /** Find NS record to resolve DS record from, walking to the right 242 * NS spot until we find it */ 243 DSNS_FIND_STATE, 244 245 /** Responses that are to be returned upstream end at this state. 246 * As well as responses to target queries. */ 247 FINISHED_STATE 248 }; 249 250 /** 251 * Shared counters for queries. 252 */ 253 enum target_count_variables { 254 /** Reference count for the shared iter_qstate->target_count. */ 255 TARGET_COUNT_REF = 0, 256 /** Number of target queries spawned for the query and subqueries. */ 257 TARGET_COUNT_QUERIES, 258 /** Number of nxdomain responses encountered. */ 259 TARGET_COUNT_NX, 260 /** Global quota on number of queries to upstream servers per 261 * client request, that is never reset. */ 262 TARGET_COUNT_GLOBAL_QUOTA, 263 264 /** This should stay last here, it is used for the allocation */ 265 TARGET_COUNT_MAX, 266 }; 267 268 /** 269 * Per query state for the iterator module. 270 */ 271 struct iter_qstate { 272 /** 273 * State of the iterator module. 274 * This is the state that event is in or should sent to -- all 275 * requests should start with the INIT_REQUEST_STATE. All 276 * responses should start with QUERY_RESP_STATE. Subsequent 277 * processing of the event will change this state. 278 */ 279 enum iter_state state; 280 281 /** 282 * Final state for the iterator module. 283 * This is the state that responses should be routed to once the 284 * response is final. For externally initiated queries, this 285 * will be FINISHED_STATE, locally initiated queries will have 286 * different final states. 287 */ 288 enum iter_state final_state; 289 290 /** 291 * The depth of this query, this means the depth of recursion. 292 * This address is needed for another query, which is an address 293 * needed for another query, etc. Original client query has depth 0. 294 */ 295 int depth; 296 297 /** 298 * The response 299 */ 300 struct dns_msg* response; 301 302 /** 303 * This is a list of RRsets that must be prepended to the 304 * ANSWER section of a response before being sent upstream. 305 */ 306 struct iter_prep_list* an_prepend_list; 307 /** Last element of the prepend list */ 308 struct iter_prep_list* an_prepend_last; 309 310 /** 311 * This is the list of RRsets that must be prepended to the 312 * AUTHORITY section of the response before being sent upstream. 313 */ 314 struct iter_prep_list* ns_prepend_list; 315 /** Last element of the authority prepend list */ 316 struct iter_prep_list* ns_prepend_last; 317 318 /** query name used for chasing the results. Initially the same as 319 * the state qinfo, but after CNAMEs this will be different. 320 * The query info used to elicit the results needed. */ 321 struct query_info qchase; 322 /** query flags to use when chasing the answer (i.e. RD flag) */ 323 uint16_t chase_flags; 324 /** true if we set RD bit because of last resort recursion lame query*/ 325 int chase_to_rd; 326 327 /** 328 * This is the current delegation point for an in-progress query. This 329 * object retains state as to which delegation targets need to be 330 * (sub)queried for vs which ones have already been visited. 331 */ 332 struct delegpt* dp; 333 334 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 335 int caps_fallback; 336 /** state for capsfail: current server number to try */ 337 size_t caps_server; 338 /** state for capsfail: stored query for comparisons. Can be NULL if 339 * no response had been seen prior to starting the fallback. */ 340 struct reply_info* caps_reply; 341 struct dns_msg* caps_response; 342 343 /** Current delegation message - returned for non-RD queries */ 344 struct dns_msg* deleg_msg; 345 346 /** number of outstanding target sub queries */ 347 int num_target_queries; 348 349 /** outstanding direct queries */ 350 int num_current_queries; 351 352 /** the number of times this query has been restarted. */ 353 int query_restart_count; 354 355 /** the number of times this query has followed a referral. */ 356 int referral_count; 357 358 /** number of queries fired off */ 359 int sent_count; 360 361 /** malloced-array shared with this query and its subqueries. It keeps 362 * track of the defined enum target_count_variables counters. */ 363 int* target_count; 364 365 /** number of target lookups per delegation point. Reset to 0 after 366 * receiving referral answer. Not shared with subqueries. */ 367 int dp_target_count; 368 369 /** Delegation point that triggered the NXNS fallback; shared with 370 * this query and its subqueries, count-referenced by the reference 371 * counter in target_count. 372 * This also marks the fallback activation. */ 373 uint8_t** nxns_dp; 374 375 /** if true, already tested for ratelimiting and passed the test */ 376 int ratelimit_ok; 377 378 /** 379 * The query must store NS records from referrals as parentside RRs 380 * Enabled once it hits resolution problems, to throttle retries. 381 * If enabled it is the pointer to the old delegation point with 382 * the old retry counts for bad-nameserver-addresses. 383 */ 384 struct delegpt* store_parent_NS; 385 386 /** 387 * The query is for parent-side glue(A or AAAA) for a nameserver. 388 * If the item is seen as glue in a referral, and pside_glue is NULL, 389 * then it is stored in pside_glue for later. 390 * If it was never seen, at the end, then a negative caching element 391 * must be created. 392 * The (data or negative) RR cache element then throttles retries. 393 */ 394 int query_for_pside_glue; 395 /** the parent-side-glue element (NULL if none, its first match) */ 396 struct ub_packed_rrset_key* pside_glue; 397 398 /** If nonNULL we are walking upwards from DS query to find NS */ 399 uint8_t* dsns_point; 400 /** length of the dname in dsns_point */ 401 size_t dsns_point_len; 402 403 /** 404 * expected dnssec information for this iteration step. 405 * If dnssec rrsigs are expected and not given, the server is marked 406 * lame (dnssec-lame). 407 */ 408 int dnssec_expected; 409 410 /** 411 * We are expecting dnssec information, but we also know the server 412 * is DNSSEC lame. The response need not be marked dnssec-lame again. 413 */ 414 int dnssec_lame_query; 415 416 /** 417 * This is flag that, if true, means that this event is 418 * waiting for a stub priming query. 419 */ 420 int wait_priming_stub; 421 422 /** 423 * This is a flag that, if true, means that this query is 424 * for (re)fetching glue from a zone. Since the address should 425 * have been glue, query again to the servers that should have 426 * been returning it as glue. 427 * The delegation point must be set to the one that should *not* 428 * be used when creating the state. A higher one will be attempted. 429 */ 430 int refetch_glue; 431 432 /** 433 * This flag detects that a completely empty nodata was received, 434 * already so that it is accepted later. */ 435 int empty_nodata_found; 436 437 /** list of pending queries to authoritative servers. */ 438 struct outbound_list outlist; 439 440 /** QNAME minimisation state, RFC9156 */ 441 enum minimisation_state minimisation_state; 442 443 /** State for capsfail: QNAME minimisation state for comparisons. */ 444 enum minimisation_state caps_minimisation_state; 445 446 /** 447 * The query info that is sent upstream. Will be a subset of qchase 448 * when qname minimisation is enabled. 449 */ 450 struct query_info qinfo_out; 451 452 /** 453 * Count number of QNAME minimisation iterations. Used to limit number of 454 * outgoing queries when QNAME minimisation is enabled. 455 */ 456 int minimise_count; 457 458 /** 459 * Count number of time-outs. Used to prevent resolving failures when 460 * the QNAME minimisation QTYPE is blocked. Used to determine if 461 * capsforid fallback should be started.*/ 462 int timeout_count; 463 464 /** True if the current response is from auth_zone */ 465 int auth_zone_response; 466 /** True if the auth_zones should not be consulted for the query */ 467 int auth_zone_avoid; 468 /** true if there have been scrubbing failures of reply packets */ 469 int scrub_failures; 470 /** true if there have been parse failures of reply packets */ 471 int parse_failures; 472 /** a failure printout address for last received answer */ 473 union { 474 struct in_addr in; 475 #ifdef AF_INET6 476 struct in6_addr in6; 477 #endif 478 } fail_addr; 479 /** which fail_addr, 0 is nothing, 4 or 6 */ 480 int fail_addr_type; 481 }; 482 483 /** 484 * List of prepend items 485 */ 486 struct iter_prep_list { 487 /** next in list */ 488 struct iter_prep_list* next; 489 /** rrset */ 490 struct ub_packed_rrset_key* rrset; 491 }; 492 493 /** 494 * Get the iterator function block. 495 * @return: function block with function pointers to iterator methods. 496 */ 497 struct module_func_block* iter_get_funcblock(void); 498 499 /** 500 * Get iterator state as a string 501 * @param state: to convert 502 * @return constant string that is printable. 503 */ 504 const char* iter_state_to_string(enum iter_state state); 505 506 /** 507 * See if iterator state is a response state 508 * @param s: to inspect 509 * @return true if response state. 510 */ 511 int iter_state_is_responsestate(enum iter_state s); 512 513 /** iterator init */ 514 int iter_init(struct module_env* env, int id); 515 516 /** iterator deinit */ 517 void iter_deinit(struct module_env* env, int id); 518 519 /** iterator operate on a query */ 520 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 521 struct outbound_entry* outbound); 522 523 /** 524 * Return priming query results to interested super querystates. 525 * 526 * Sets the delegation point and delegation message (not nonRD queries). 527 * This is a callback from walk_supers. 528 * 529 * @param qstate: query state that finished. 530 * @param id: module id. 531 * @param super: the qstate to inform. 532 */ 533 void iter_inform_super(struct module_qstate* qstate, int id, 534 struct module_qstate* super); 535 536 /** iterator cleanup query state */ 537 void iter_clear(struct module_qstate* qstate, int id); 538 539 /** iterator alloc size routine */ 540 size_t iter_get_mem(struct module_env* env, int id); 541 542 #endif /* ITERATOR_ITERATOR_H */ 543