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 recusive 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_t; 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 misssing 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_t* 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 /** ip6.arpa dname in wireformat, used for qname-minimisation */ 134 uint8_t* ip6arpa_dname; 135 }; 136 137 /** 138 * QNAME minimisation state 139 */ 140 enum minimisation_state { 141 /** 142 * (Re)start minimisation. Outgoing QNAME should be set to dp->name. 143 * State entered on new query or after following refferal or CNAME. 144 */ 145 INIT_MINIMISE_STATE = 0, 146 /** 147 * QNAME minimisataion ongoing. Increase QNAME on every iteration. 148 */ 149 MINIMISE_STATE, 150 /** 151 * Don't increment QNAME this iteration 152 */ 153 SKIP_MINIMISE_STATE, 154 /** 155 * Send out full QNAME + original QTYPE 156 */ 157 DONOT_MINIMISE_STATE, 158 }; 159 160 /** 161 * State of the iterator for a query. 162 */ 163 enum iter_state { 164 /** 165 * Externally generated queries start at this state. Query restarts are 166 * reset to this state. 167 */ 168 INIT_REQUEST_STATE = 0, 169 170 /** 171 * Root priming events reactivate here, most other events pass 172 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 173 */ 174 INIT_REQUEST_2_STATE, 175 176 /** 177 * Stub priming events reactivate here, most other events pass 178 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 179 */ 180 INIT_REQUEST_3_STATE, 181 182 /** 183 * Each time a delegation point changes for a given query or a 184 * query times out and/or wakes up, this state is (re)visited. 185 * This state is reponsible for iterating through a list of 186 * nameserver targets. 187 */ 188 QUERYTARGETS_STATE, 189 190 /** 191 * Responses to queries start at this state. This state handles 192 * the decision tree associated with handling responses. 193 */ 194 QUERY_RESP_STATE, 195 196 /** Responses to priming queries finish at this state. */ 197 PRIME_RESP_STATE, 198 199 /** Collecting query class information, for qclass=ANY, when 200 * it spawns off queries for every class, it returns here. */ 201 COLLECT_CLASS_STATE, 202 203 /** Find NS record to resolve DS record from, walking to the right 204 * NS spot until we find it */ 205 DSNS_FIND_STATE, 206 207 /** Responses that are to be returned upstream end at this state. 208 * As well as responses to target queries. */ 209 FINISHED_STATE 210 }; 211 212 /** 213 * Per query state for the iterator module. 214 */ 215 struct iter_qstate { 216 /** 217 * State of the iterator module. 218 * This is the state that event is in or should sent to -- all 219 * requests should start with the INIT_REQUEST_STATE. All 220 * responses should start with QUERY_RESP_STATE. Subsequent 221 * processing of the event will change this state. 222 */ 223 enum iter_state state; 224 225 /** 226 * Final state for the iterator module. 227 * This is the state that responses should be routed to once the 228 * response is final. For externally initiated queries, this 229 * will be FINISHED_STATE, locally initiated queries will have 230 * different final states. 231 */ 232 enum iter_state final_state; 233 234 /** 235 * The depth of this query, this means the depth of recursion. 236 * This address is needed for another query, which is an address 237 * needed for another query, etc. Original client query has depth 0. 238 */ 239 int depth; 240 241 /** 242 * The response 243 */ 244 struct dns_msg* response; 245 246 /** 247 * This is a list of RRsets that must be prepended to the 248 * ANSWER section of a response before being sent upstream. 249 */ 250 struct iter_prep_list* an_prepend_list; 251 /** Last element of the prepend list */ 252 struct iter_prep_list* an_prepend_last; 253 254 /** 255 * This is the list of RRsets that must be prepended to the 256 * AUTHORITY section of the response before being sent upstream. 257 */ 258 struct iter_prep_list* ns_prepend_list; 259 /** Last element of the authority prepend list */ 260 struct iter_prep_list* ns_prepend_last; 261 262 /** query name used for chasing the results. Initially the same as 263 * the state qinfo, but after CNAMEs this will be different. 264 * The query info used to elicit the results needed. */ 265 struct query_info qchase; 266 /** query flags to use when chasing the answer (i.e. RD flag) */ 267 uint16_t chase_flags; 268 /** true if we set RD bit because of last resort recursion lame query*/ 269 int chase_to_rd; 270 271 /** 272 * This is the current delegation point for an in-progress query. This 273 * object retains state as to which delegation targets need to be 274 * (sub)queried for vs which ones have already been visited. 275 */ 276 struct delegpt* dp; 277 278 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 279 int caps_fallback; 280 /** state for capsfail: current server number to try */ 281 size_t caps_server; 282 /** state for capsfail: stored query for comparisons. Can be NULL if 283 * no response had been seen prior to starting the fallback. */ 284 struct reply_info* caps_reply; 285 struct dns_msg* caps_response; 286 287 /** Current delegation message - returned for non-RD queries */ 288 struct dns_msg* deleg_msg; 289 290 /** number of outstanding target sub queries */ 291 int num_target_queries; 292 293 /** outstanding direct queries */ 294 int num_current_queries; 295 296 /** the number of times this query has been restarted. */ 297 int query_restart_count; 298 299 /** the number of times this query as followed a referral. */ 300 int referral_count; 301 302 /** number of queries fired off */ 303 int sent_count; 304 305 /** number of target queries spawned in [1], for this query and its 306 * subqueries, the malloced-array is shared, [0] refcount. */ 307 int* target_count; 308 309 /** if true, already tested for ratelimiting and passed the test */ 310 int ratelimit_ok; 311 312 /** 313 * The query must store NS records from referrals as parentside RRs 314 * Enabled once it hits resolution problems, to throttle retries. 315 * If enabled it is the pointer to the old delegation point with 316 * the old retry counts for bad-nameserver-addresses. 317 */ 318 struct delegpt* store_parent_NS; 319 320 /** 321 * The query is for parent-side glue(A or AAAA) for a nameserver. 322 * If the item is seen as glue in a referral, and pside_glue is NULL, 323 * then it is stored in pside_glue for later. 324 * If it was never seen, at the end, then a negative caching element 325 * must be created. 326 * The (data or negative) RR cache element then throttles retries. 327 */ 328 int query_for_pside_glue; 329 /** the parent-side-glue element (NULL if none, its first match) */ 330 struct ub_packed_rrset_key* pside_glue; 331 332 /** If nonNULL we are walking upwards from DS query to find NS */ 333 uint8_t* dsns_point; 334 /** length of the dname in dsns_point */ 335 size_t dsns_point_len; 336 337 /** 338 * expected dnssec information for this iteration step. 339 * If dnssec rrsigs are expected and not given, the server is marked 340 * lame (dnssec-lame). 341 */ 342 int dnssec_expected; 343 344 /** 345 * We are expecting dnssec information, but we also know the server 346 * is DNSSEC lame. The response need not be marked dnssec-lame again. 347 */ 348 int dnssec_lame_query; 349 350 /** 351 * This is flag that, if true, means that this event is 352 * waiting for a stub priming query. 353 */ 354 int wait_priming_stub; 355 356 /** 357 * This is a flag that, if true, means that this query is 358 * for (re)fetching glue from a zone. Since the address should 359 * have been glue, query again to the servers that should have 360 * been returning it as glue. 361 * The delegation point must be set to the one that should *not* 362 * be used when creating the state. A higher one will be attempted. 363 */ 364 int refetch_glue; 365 366 /** list of pending queries to authoritative servers. */ 367 struct outbound_list outlist; 368 369 /** QNAME minimisation state, RFC7816 */ 370 enum minimisation_state minimisation_state; 371 372 /** 373 * The query info that is sent upstream. Will be a subset of qchase 374 * when qname minimisation is enabled. 375 */ 376 struct query_info qinfo_out; 377 378 /** 379 * Count number of QNAME minisation iterations. Used to limit number of 380 * outgoing queries when QNAME minimisation is enabled. 381 */ 382 int minimise_count; 383 384 /** 385 * Count number of time-outs. Used to prevent resolving failures when 386 * the QNAME minimisation QTYPE is blocked. */ 387 int minimise_timeout_count; 388 }; 389 390 /** 391 * List of prepend items 392 */ 393 struct iter_prep_list { 394 /** next in list */ 395 struct iter_prep_list* next; 396 /** rrset */ 397 struct ub_packed_rrset_key* rrset; 398 }; 399 400 /** 401 * Get the iterator function block. 402 * @return: function block with function pointers to iterator methods. 403 */ 404 struct module_func_block* iter_get_funcblock(void); 405 406 /** 407 * Get iterator state as a string 408 * @param state: to convert 409 * @return constant string that is printable. 410 */ 411 const char* iter_state_to_string(enum iter_state state); 412 413 /** 414 * See if iterator state is a response state 415 * @param s: to inspect 416 * @return true if response state. 417 */ 418 int iter_state_is_responsestate(enum iter_state s); 419 420 /** iterator init */ 421 int iter_init(struct module_env* env, int id); 422 423 /** iterator deinit */ 424 void iter_deinit(struct module_env* env, int id); 425 426 /** iterator operate on a query */ 427 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 428 struct outbound_entry* outbound); 429 430 /** 431 * Return priming query results to interestes super querystates. 432 * 433 * Sets the delegation point and delegation message (not nonRD queries). 434 * This is a callback from walk_supers. 435 * 436 * @param qstate: query state that finished. 437 * @param id: module id. 438 * @param super: the qstate to inform. 439 */ 440 void iter_inform_super(struct module_qstate* qstate, int id, 441 struct module_qstate* super); 442 443 /** iterator cleanup query state */ 444 void iter_clear(struct module_qstate* qstate, int id); 445 446 /** iterator alloc size routine */ 447 size_t iter_get_mem(struct module_env* env, int id); 448 449 #endif /* ITERATOR_ITERATOR_H */ 450