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 98 */ 99 #define USEFUL_SERVER_TOP_TIMEOUT 120000 100 /** RTT band, within this amount from the best, servers are chosen randomly. 101 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 102 * fast server, this causes server exploration as a side benefit. msec. */ 103 #define RTT_BAND 400 104 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */ 105 #define INFRA_BACKOFF_INITIAL 240 106 107 /** 108 * Global state for the iterator. 109 */ 110 struct iter_env { 111 /** A flag to indicate whether or not we have an IPv6 route */ 112 int supports_ipv6; 113 114 /** A flag to indicate whether or not we have an IPv4 route */ 115 int supports_ipv4; 116 117 /** A set of inetaddrs that should never be queried. */ 118 struct iter_donotq* donotq; 119 120 /** private address space and private domains */ 121 struct iter_priv* priv; 122 123 /** whitelist for capsforid names */ 124 struct rbtree_type* caps_white; 125 126 /** The maximum dependency depth that this resolver will pursue. */ 127 int max_dependency_depth; 128 129 /** 130 * The target fetch policy for each dependency level. This is 131 * described as a simple number (per dependency level): 132 * negative numbers (usually just -1) mean fetch-all, 133 * 0 means only fetch on demand, and 134 * positive numbers mean to fetch at most that many targets. 135 * array of max_dependency_depth+1 size. 136 */ 137 int* target_fetch_policy; 138 139 /** lock on ratelimit counter */ 140 lock_basic_type queries_ratelimit_lock; 141 /** number of queries that have been ratelimited */ 142 size_t num_queries_ratelimited; 143 144 /** number of retries on outgoing queries */ 145 int outbound_msg_retry; 146 }; 147 148 /** 149 * QNAME minimisation state 150 */ 151 enum minimisation_state { 152 /** 153 * (Re)start minimisation. Outgoing QNAME should be set to dp->name. 154 * State entered on new query or after following referral or CNAME. 155 */ 156 INIT_MINIMISE_STATE = 0, 157 /** 158 * QNAME minimisation ongoing. Increase QNAME on every iteration. 159 */ 160 MINIMISE_STATE, 161 /** 162 * Don't increment QNAME this iteration 163 */ 164 SKIP_MINIMISE_STATE, 165 /** 166 * Send out full QNAME + original QTYPE 167 */ 168 DONOT_MINIMISE_STATE, 169 }; 170 171 /** 172 * State of the iterator for a query. 173 */ 174 enum iter_state { 175 /** 176 * Externally generated queries start at this state. Query restarts are 177 * reset to this state. 178 */ 179 INIT_REQUEST_STATE = 0, 180 181 /** 182 * Root priming events reactivate here, most other events pass 183 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 184 */ 185 INIT_REQUEST_2_STATE, 186 187 /** 188 * Stub priming events reactivate here, most other events pass 189 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 190 */ 191 INIT_REQUEST_3_STATE, 192 193 /** 194 * Each time a delegation point changes for a given query or a 195 * query times out and/or wakes up, this state is (re)visited. 196 * This state is responsible for iterating through a list of 197 * nameserver targets. 198 */ 199 QUERYTARGETS_STATE, 200 201 /** 202 * Responses to queries start at this state. This state handles 203 * the decision tree associated with handling responses. 204 */ 205 QUERY_RESP_STATE, 206 207 /** Responses to priming queries finish at this state. */ 208 PRIME_RESP_STATE, 209 210 /** Collecting query class information, for qclass=ANY, when 211 * it spawns off queries for every class, it returns here. */ 212 COLLECT_CLASS_STATE, 213 214 /** Find NS record to resolve DS record from, walking to the right 215 * NS spot until we find it */ 216 DSNS_FIND_STATE, 217 218 /** Responses that are to be returned upstream end at this state. 219 * As well as responses to target queries. */ 220 FINISHED_STATE 221 }; 222 223 /** 224 * Shared counters for queries. 225 */ 226 enum target_count_variables { 227 /** Reference count for the shared iter_qstate->target_count. */ 228 TARGET_COUNT_REF = 0, 229 /** Number of target queries spawned for the query and subqueries. */ 230 TARGET_COUNT_QUERIES, 231 /** Number of nxdomain responses encountered. */ 232 TARGET_COUNT_NX, 233 234 /** This should stay last here, it is used for the allocation */ 235 TARGET_COUNT_MAX, 236 }; 237 238 /** 239 * Per query state for the iterator module. 240 */ 241 struct iter_qstate { 242 /** 243 * State of the iterator module. 244 * This is the state that event is in or should sent to -- all 245 * requests should start with the INIT_REQUEST_STATE. All 246 * responses should start with QUERY_RESP_STATE. Subsequent 247 * processing of the event will change this state. 248 */ 249 enum iter_state state; 250 251 /** 252 * Final state for the iterator module. 253 * This is the state that responses should be routed to once the 254 * response is final. For externally initiated queries, this 255 * will be FINISHED_STATE, locally initiated queries will have 256 * different final states. 257 */ 258 enum iter_state final_state; 259 260 /** 261 * The depth of this query, this means the depth of recursion. 262 * This address is needed for another query, which is an address 263 * needed for another query, etc. Original client query has depth 0. 264 */ 265 int depth; 266 267 /** 268 * The response 269 */ 270 struct dns_msg* response; 271 272 /** 273 * This is a list of RRsets that must be prepended to the 274 * ANSWER section of a response before being sent upstream. 275 */ 276 struct iter_prep_list* an_prepend_list; 277 /** Last element of the prepend list */ 278 struct iter_prep_list* an_prepend_last; 279 280 /** 281 * This is the list of RRsets that must be prepended to the 282 * AUTHORITY section of the response before being sent upstream. 283 */ 284 struct iter_prep_list* ns_prepend_list; 285 /** Last element of the authority prepend list */ 286 struct iter_prep_list* ns_prepend_last; 287 288 /** query name used for chasing the results. Initially the same as 289 * the state qinfo, but after CNAMEs this will be different. 290 * The query info used to elicit the results needed. */ 291 struct query_info qchase; 292 /** query flags to use when chasing the answer (i.e. RD flag) */ 293 uint16_t chase_flags; 294 /** true if we set RD bit because of last resort recursion lame query*/ 295 int chase_to_rd; 296 297 /** 298 * This is the current delegation point for an in-progress query. This 299 * object retains state as to which delegation targets need to be 300 * (sub)queried for vs which ones have already been visited. 301 */ 302 struct delegpt* dp; 303 304 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 305 int caps_fallback; 306 /** state for capsfail: current server number to try */ 307 size_t caps_server; 308 /** state for capsfail: stored query for comparisons. Can be NULL if 309 * no response had been seen prior to starting the fallback. */ 310 struct reply_info* caps_reply; 311 struct dns_msg* caps_response; 312 313 /** Current delegation message - returned for non-RD queries */ 314 struct dns_msg* deleg_msg; 315 316 /** number of outstanding target sub queries */ 317 int num_target_queries; 318 319 /** outstanding direct queries */ 320 int num_current_queries; 321 322 /** the number of times this query has been restarted. */ 323 int query_restart_count; 324 325 /** the number of times this query as followed a referral. */ 326 int referral_count; 327 328 /** number of queries fired off */ 329 int sent_count; 330 331 /** malloced-array shared with this query and its subqueries. It keeps 332 * track of the defined enum target_count_variables counters. */ 333 int* target_count; 334 335 /** number of target lookups per delegation point. Reset to 0 after 336 * receiving referral answer. Not shared with subqueries. */ 337 int dp_target_count; 338 339 /** Delegation point that triggered the NXNS fallback; shared with 340 * this query and its subqueries, count-referenced by the reference 341 * counter in target_count. 342 * This also marks the fallback activation. */ 343 uint8_t** nxns_dp; 344 345 /** if true, already tested for ratelimiting and passed the test */ 346 int ratelimit_ok; 347 348 /** 349 * The query must store NS records from referrals as parentside RRs 350 * Enabled once it hits resolution problems, to throttle retries. 351 * If enabled it is the pointer to the old delegation point with 352 * the old retry counts for bad-nameserver-addresses. 353 */ 354 struct delegpt* store_parent_NS; 355 356 /** 357 * The query is for parent-side glue(A or AAAA) for a nameserver. 358 * If the item is seen as glue in a referral, and pside_glue is NULL, 359 * then it is stored in pside_glue for later. 360 * If it was never seen, at the end, then a negative caching element 361 * must be created. 362 * The (data or negative) RR cache element then throttles retries. 363 */ 364 int query_for_pside_glue; 365 /** the parent-side-glue element (NULL if none, its first match) */ 366 struct ub_packed_rrset_key* pside_glue; 367 368 /** If nonNULL we are walking upwards from DS query to find NS */ 369 uint8_t* dsns_point; 370 /** length of the dname in dsns_point */ 371 size_t dsns_point_len; 372 373 /** 374 * expected dnssec information for this iteration step. 375 * If dnssec rrsigs are expected and not given, the server is marked 376 * lame (dnssec-lame). 377 */ 378 int dnssec_expected; 379 380 /** 381 * We are expecting dnssec information, but we also know the server 382 * is DNSSEC lame. The response need not be marked dnssec-lame again. 383 */ 384 int dnssec_lame_query; 385 386 /** 387 * This is flag that, if true, means that this event is 388 * waiting for a stub priming query. 389 */ 390 int wait_priming_stub; 391 392 /** 393 * This is a flag that, if true, means that this query is 394 * for (re)fetching glue from a zone. Since the address should 395 * have been glue, query again to the servers that should have 396 * been returning it as glue. 397 * The delegation point must be set to the one that should *not* 398 * be used when creating the state. A higher one will be attempted. 399 */ 400 int refetch_glue; 401 402 /** list of pending queries to authoritative servers. */ 403 struct outbound_list outlist; 404 405 /** QNAME minimisation state, RFC9156 */ 406 enum minimisation_state minimisation_state; 407 408 /** State for capsfail: QNAME minimisation state for comparisons. */ 409 enum minimisation_state caps_minimisation_state; 410 411 /** 412 * The query info that is sent upstream. Will be a subset of qchase 413 * when qname minimisation is enabled. 414 */ 415 struct query_info qinfo_out; 416 417 /** 418 * Count number of QNAME minimisation iterations. Used to limit number of 419 * outgoing queries when QNAME minimisation is enabled. 420 */ 421 int minimise_count; 422 423 /** 424 * Count number of time-outs. Used to prevent resolving failures when 425 * the QNAME minimisation QTYPE is blocked. Used to determine if 426 * capsforid fallback should be started.*/ 427 int timeout_count; 428 429 /** True if the current response is from auth_zone */ 430 int auth_zone_response; 431 /** True if the auth_zones should not be consulted for the query */ 432 int auth_zone_avoid; 433 /** true if there have been scrubbing failures of reply packets */ 434 int scrub_failures; 435 /** true if there have been parse failures of reply packets */ 436 int parse_failures; 437 /** a failure printout address for last received answer */ 438 struct comm_reply* fail_reply; 439 }; 440 441 /** 442 * List of prepend items 443 */ 444 struct iter_prep_list { 445 /** next in list */ 446 struct iter_prep_list* next; 447 /** rrset */ 448 struct ub_packed_rrset_key* rrset; 449 }; 450 451 /** 452 * Get the iterator function block. 453 * @return: function block with function pointers to iterator methods. 454 */ 455 struct module_func_block* iter_get_funcblock(void); 456 457 /** 458 * Get iterator state as a string 459 * @param state: to convert 460 * @return constant string that is printable. 461 */ 462 const char* iter_state_to_string(enum iter_state state); 463 464 /** 465 * See if iterator state is a response state 466 * @param s: to inspect 467 * @return true if response state. 468 */ 469 int iter_state_is_responsestate(enum iter_state s); 470 471 /** iterator init */ 472 int iter_init(struct module_env* env, int id); 473 474 /** iterator deinit */ 475 void iter_deinit(struct module_env* env, int id); 476 477 /** iterator operate on a query */ 478 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 479 struct outbound_entry* outbound); 480 481 /** 482 * Return priming query results to interested super querystates. 483 * 484 * Sets the delegation point and delegation message (not nonRD queries). 485 * This is a callback from walk_supers. 486 * 487 * @param qstate: query state that finished. 488 * @param id: module id. 489 * @param super: the qstate to inform. 490 */ 491 void iter_inform_super(struct module_qstate* qstate, int id, 492 struct module_qstate* super); 493 494 /** iterator cleanup query state */ 495 void iter_clear(struct module_qstate* qstate, int id); 496 497 /** iterator alloc size routine */ 498 size_t iter_get_mem(struct module_env* env, int id); 499 500 #endif /* ITERATOR_ITERATOR_H */ 501