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 query restarts. Determines max number of CNAME chain. */ 59 #define MAX_RESTART_COUNT 8 60 /** max number of referrals. Makes sure resolver does not run away */ 61 #define MAX_REFERRAL_COUNT 130 62 /** max number of queries-sent-out. Make sure large NS set does not loop */ 63 #define MAX_SENT_COUNT 32 64 /** max number of queries for which to perform dnsseclameness detection, 65 * (rrsigs missing detection) after that, just pick up that response */ 66 #define DNSSEC_LAME_DETECT_COUNT 4 67 /** 68 * max number of QNAME minimisation iterations. Limits number of queries for 69 * QNAMEs with a lot of labels. 70 */ 71 #define MAX_MINIMISE_COUNT 10 72 /* max number of time-outs for minimised query. Prevents resolving failures 73 * when the QNAME minimisation QTYPE is blocked. */ 74 #define MAX_MINIMISE_TIMEOUT_COUNT 3 75 /** 76 * number of labels from QNAME that are always send individually when using 77 * QNAME minimisation, even when the number of labels of the QNAME is bigger 78 * tham MAX_MINIMISE_COUNT */ 79 #define MINIMISE_ONE_LAB 4 80 #define MINIMISE_MULTIPLE_LABS (MAX_MINIMISE_COUNT - MINIMISE_ONE_LAB) 81 /** at what query-sent-count to stop target fetch policy */ 82 #define TARGET_FETCH_STOP 3 83 /** how nice is a server without further information, in msec 84 * Equals rtt initial timeout value. 85 */ 86 #define UNKNOWN_SERVER_NICENESS 376 87 /** maximum timeout before a host is deemed unsuitable, in msec. 88 * After host_ttl this will be timed out and the host will be tried again. 89 * Equals RTT_MAX_TIMEOUT 90 */ 91 #define USEFUL_SERVER_TOP_TIMEOUT 120000 92 /** number of retries on outgoing queries */ 93 #define OUTBOUND_MSG_RETRY 5 94 /** RTT band, within this amount from the best, servers are chosen randomly. 95 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 96 * fast server, this causes server exploration as a side benefit. msec. */ 97 #define RTT_BAND 400 98 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */ 99 #define INFRA_BACKOFF_INITIAL 240 100 101 /** 102 * Global state for the iterator. 103 */ 104 struct iter_env { 105 /** A flag to indicate whether or not we have an IPv6 route */ 106 int supports_ipv6; 107 108 /** A flag to indicate whether or not we have an IPv4 route */ 109 int supports_ipv4; 110 111 /** A set of inetaddrs that should never be queried. */ 112 struct iter_donotq* donotq; 113 114 /** private address space and private domains */ 115 struct iter_priv* priv; 116 117 /** whitelist for capsforid names */ 118 struct rbtree_type* caps_white; 119 120 /** The maximum dependency depth that this resolver will pursue. */ 121 int max_dependency_depth; 122 123 /** 124 * The target fetch policy for each dependency level. This is 125 * described as a simple number (per dependency level): 126 * negative numbers (usually just -1) mean fetch-all, 127 * 0 means only fetch on demand, and 128 * positive numbers mean to fetch at most that many targets. 129 * array of max_dependency_depth+1 size. 130 */ 131 int* target_fetch_policy; 132 133 /** lock on ratelimit counter */ 134 lock_basic_type queries_ratelimit_lock; 135 /** number of queries that have been ratelimited */ 136 size_t num_queries_ratelimited; 137 }; 138 139 /** 140 * QNAME minimisation state 141 */ 142 enum minimisation_state { 143 /** 144 * (Re)start minimisation. Outgoing QNAME should be set to dp->name. 145 * State entered on new query or after following referral or CNAME. 146 */ 147 INIT_MINIMISE_STATE = 0, 148 /** 149 * QNAME minimisation ongoing. Increase QNAME on every iteration. 150 */ 151 MINIMISE_STATE, 152 /** 153 * Don't increment QNAME this iteration 154 */ 155 SKIP_MINIMISE_STATE, 156 /** 157 * Send out full QNAME + original QTYPE 158 */ 159 DONOT_MINIMISE_STATE, 160 }; 161 162 /** 163 * State of the iterator for a query. 164 */ 165 enum iter_state { 166 /** 167 * Externally generated queries start at this state. Query restarts are 168 * reset to this state. 169 */ 170 INIT_REQUEST_STATE = 0, 171 172 /** 173 * Root priming events reactivate here, most other events pass 174 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 175 */ 176 INIT_REQUEST_2_STATE, 177 178 /** 179 * Stub priming events reactivate here, most other events pass 180 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 181 */ 182 INIT_REQUEST_3_STATE, 183 184 /** 185 * Each time a delegation point changes for a given query or a 186 * query times out and/or wakes up, this state is (re)visited. 187 * This state is responsible for iterating through a list of 188 * nameserver targets. 189 */ 190 QUERYTARGETS_STATE, 191 192 /** 193 * Responses to queries start at this state. This state handles 194 * the decision tree associated with handling responses. 195 */ 196 QUERY_RESP_STATE, 197 198 /** Responses to priming queries finish at this state. */ 199 PRIME_RESP_STATE, 200 201 /** Collecting query class information, for qclass=ANY, when 202 * it spawns off queries for every class, it returns here. */ 203 COLLECT_CLASS_STATE, 204 205 /** Find NS record to resolve DS record from, walking to the right 206 * NS spot until we find it */ 207 DSNS_FIND_STATE, 208 209 /** Responses that are to be returned upstream end at this state. 210 * As well as responses to target queries. */ 211 FINISHED_STATE 212 }; 213 214 /** 215 * Per query state for the iterator module. 216 */ 217 struct iter_qstate { 218 /** 219 * State of the iterator module. 220 * This is the state that event is in or should sent to -- all 221 * requests should start with the INIT_REQUEST_STATE. All 222 * responses should start with QUERY_RESP_STATE. Subsequent 223 * processing of the event will change this state. 224 */ 225 enum iter_state state; 226 227 /** 228 * Final state for the iterator module. 229 * This is the state that responses should be routed to once the 230 * response is final. For externally initiated queries, this 231 * will be FINISHED_STATE, locally initiated queries will have 232 * different final states. 233 */ 234 enum iter_state final_state; 235 236 /** 237 * The depth of this query, this means the depth of recursion. 238 * This address is needed for another query, which is an address 239 * needed for another query, etc. Original client query has depth 0. 240 */ 241 int depth; 242 243 /** 244 * The response 245 */ 246 struct dns_msg* response; 247 248 /** 249 * This is a list of RRsets that must be prepended to the 250 * ANSWER section of a response before being sent upstream. 251 */ 252 struct iter_prep_list* an_prepend_list; 253 /** Last element of the prepend list */ 254 struct iter_prep_list* an_prepend_last; 255 256 /** 257 * This is the list of RRsets that must be prepended to the 258 * AUTHORITY section of the response before being sent upstream. 259 */ 260 struct iter_prep_list* ns_prepend_list; 261 /** Last element of the authority prepend list */ 262 struct iter_prep_list* ns_prepend_last; 263 264 /** query name used for chasing the results. Initially the same as 265 * the state qinfo, but after CNAMEs this will be different. 266 * The query info used to elicit the results needed. */ 267 struct query_info qchase; 268 /** query flags to use when chasing the answer (i.e. RD flag) */ 269 uint16_t chase_flags; 270 /** true if we set RD bit because of last resort recursion lame query*/ 271 int chase_to_rd; 272 273 /** 274 * This is the current delegation point for an in-progress query. This 275 * object retains state as to which delegation targets need to be 276 * (sub)queried for vs which ones have already been visited. 277 */ 278 struct delegpt* dp; 279 280 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 281 int caps_fallback; 282 /** state for capsfail: current server number to try */ 283 size_t caps_server; 284 /** state for capsfail: stored query for comparisons. Can be NULL if 285 * no response had been seen prior to starting the fallback. */ 286 struct reply_info* caps_reply; 287 struct dns_msg* caps_response; 288 289 /** Current delegation message - returned for non-RD queries */ 290 struct dns_msg* deleg_msg; 291 292 /** number of outstanding target sub queries */ 293 int num_target_queries; 294 295 /** outstanding direct queries */ 296 int num_current_queries; 297 298 /** the number of times this query has been restarted. */ 299 int query_restart_count; 300 301 /** the number of times this query as followed a referral. */ 302 int referral_count; 303 304 /** number of queries fired off */ 305 int sent_count; 306 307 /** number of target queries spawned in [1], for this query and its 308 * subqueries, the malloced-array is shared, [0] refcount. */ 309 int* target_count; 310 311 /** if true, already tested for ratelimiting and passed the test */ 312 int ratelimit_ok; 313 314 /** 315 * The query must store NS records from referrals as parentside RRs 316 * Enabled once it hits resolution problems, to throttle retries. 317 * If enabled it is the pointer to the old delegation point with 318 * the old retry counts for bad-nameserver-addresses. 319 */ 320 struct delegpt* store_parent_NS; 321 322 /** 323 * The query is for parent-side glue(A or AAAA) for a nameserver. 324 * If the item is seen as glue in a referral, and pside_glue is NULL, 325 * then it is stored in pside_glue for later. 326 * If it was never seen, at the end, then a negative caching element 327 * must be created. 328 * The (data or negative) RR cache element then throttles retries. 329 */ 330 int query_for_pside_glue; 331 /** the parent-side-glue element (NULL if none, its first match) */ 332 struct ub_packed_rrset_key* pside_glue; 333 334 /** If nonNULL we are walking upwards from DS query to find NS */ 335 uint8_t* dsns_point; 336 /** length of the dname in dsns_point */ 337 size_t dsns_point_len; 338 339 /** 340 * expected dnssec information for this iteration step. 341 * If dnssec rrsigs are expected and not given, the server is marked 342 * lame (dnssec-lame). 343 */ 344 int dnssec_expected; 345 346 /** 347 * We are expecting dnssec information, but we also know the server 348 * is DNSSEC lame. The response need not be marked dnssec-lame again. 349 */ 350 int dnssec_lame_query; 351 352 /** 353 * This is flag that, if true, means that this event is 354 * waiting for a stub priming query. 355 */ 356 int wait_priming_stub; 357 358 /** 359 * This is a flag that, if true, means that this query is 360 * for (re)fetching glue from a zone. Since the address should 361 * have been glue, query again to the servers that should have 362 * been returning it as glue. 363 * The delegation point must be set to the one that should *not* 364 * be used when creating the state. A higher one will be attempted. 365 */ 366 int refetch_glue; 367 368 /** list of pending queries to authoritative servers. */ 369 struct outbound_list outlist; 370 371 /** QNAME minimisation state, RFC7816 */ 372 enum minimisation_state minimisation_state; 373 374 /** State for capsfail: QNAME minimisation state for comparisons. */ 375 enum minimisation_state caps_minimisation_state; 376 377 /** 378 * The query info that is sent upstream. Will be a subset of qchase 379 * when qname minimisation is enabled. 380 */ 381 struct query_info qinfo_out; 382 383 /** 384 * Count number of QNAME minimisation iterations. Used to limit number of 385 * outgoing queries when QNAME minimisation is enabled. 386 */ 387 int minimise_count; 388 389 /** 390 * Count number of time-outs. Used to prevent resolving failures when 391 * the QNAME minimisation QTYPE is blocked. */ 392 int minimise_timeout_count; 393 394 /** True if the current response is from auth_zone */ 395 int auth_zone_response; 396 /** True if the auth_zones should not be consulted for the query */ 397 int auth_zone_avoid; 398 }; 399 400 /** 401 * List of prepend items 402 */ 403 struct iter_prep_list { 404 /** next in list */ 405 struct iter_prep_list* next; 406 /** rrset */ 407 struct ub_packed_rrset_key* rrset; 408 }; 409 410 /** 411 * Get the iterator function block. 412 * @return: function block with function pointers to iterator methods. 413 */ 414 struct module_func_block* iter_get_funcblock(void); 415 416 /** 417 * Get iterator state as a string 418 * @param state: to convert 419 * @return constant string that is printable. 420 */ 421 const char* iter_state_to_string(enum iter_state state); 422 423 /** 424 * See if iterator state is a response state 425 * @param s: to inspect 426 * @return true if response state. 427 */ 428 int iter_state_is_responsestate(enum iter_state s); 429 430 /** iterator init */ 431 int iter_init(struct module_env* env, int id); 432 433 /** iterator deinit */ 434 void iter_deinit(struct module_env* env, int id); 435 436 /** iterator operate on a query */ 437 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 438 struct outbound_entry* outbound); 439 440 /** 441 * Return priming query results to interested super querystates. 442 * 443 * Sets the delegation point and delegation message (not nonRD queries). 444 * This is a callback from walk_supers. 445 * 446 * @param qstate: query state that finished. 447 * @param id: module id. 448 * @param super: the qstate to inform. 449 */ 450 void iter_inform_super(struct module_qstate* qstate, int id, 451 struct module_qstate* super); 452 453 /** iterator cleanup query state */ 454 void iter_clear(struct module_qstate* qstate, int id); 455 456 /** iterator alloc size routine */ 457 size_t iter_get_mem(struct module_env* env, int id); 458 459 #endif /* ITERATOR_ITERATOR_H */ 460