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 /** 73 * number of labels from QNAME that are always send individually when using 74 * QNAME minimisation, even when the number of labels of the QNAME is bigger 75 * tham MAX_MINIMISE_COUNT */ 76 #define MINIMISE_ONE_LAB 4 77 #define MINIMISE_MULTIPLE_LABS (MAX_MINIMISE_COUNT - MINIMISE_ONE_LAB) 78 /** at what query-sent-count to stop target fetch policy */ 79 #define TARGET_FETCH_STOP 3 80 /** how nice is a server without further information, in msec 81 * Equals rtt initial timeout value. 82 */ 83 #define UNKNOWN_SERVER_NICENESS 376 84 /** maximum timeout before a host is deemed unsuitable, in msec. 85 * After host_ttl this will be timed out and the host will be tried again. 86 * Equals RTT_MAX_TIMEOUT 87 */ 88 #define USEFUL_SERVER_TOP_TIMEOUT 120000 89 /** number of retries on outgoing queries */ 90 #define OUTBOUND_MSG_RETRY 5 91 /** RTT band, within this amount from the best, servers are chosen randomly. 92 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 93 * fast server, this causes server exploration as a side benefit. msec. */ 94 #define RTT_BAND 400 95 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */ 96 #define INFRA_BACKOFF_INITIAL 240 97 98 /** 99 * Global state for the iterator. 100 */ 101 struct iter_env { 102 /** A flag to indicate whether or not we have an IPv6 route */ 103 int supports_ipv6; 104 105 /** A flag to indicate whether or not we have an IPv4 route */ 106 int supports_ipv4; 107 108 /** A set of inetaddrs that should never be queried. */ 109 struct iter_donotq* donotq; 110 111 /** private address space and private domains */ 112 struct iter_priv* priv; 113 114 /** whitelist for capsforid names */ 115 struct rbtree_t* caps_white; 116 117 /** The maximum dependency depth that this resolver will pursue. */ 118 int max_dependency_depth; 119 120 /** 121 * The target fetch policy for each dependency level. This is 122 * described as a simple number (per dependency level): 123 * negative numbers (usually just -1) mean fetch-all, 124 * 0 means only fetch on demand, and 125 * positive numbers mean to fetch at most that many targets. 126 * array of max_dependency_depth+1 size. 127 */ 128 int* target_fetch_policy; 129 130 /** ip6.arpa dname in wireformat, used for qname-minimisation */ 131 uint8_t* ip6arpa_dname; 132 }; 133 134 /** 135 * QNAME minimisation state 136 */ 137 enum minimisation_state { 138 /** 139 * (Re)start minimisation. Outgoing QNAME should be set to dp->name. 140 * State entered on new query or after following refferal or CNAME. 141 */ 142 INIT_MINIMISE_STATE = 0, 143 /** 144 * QNAME minimisataion ongoing. Increase QNAME on every iteration. 145 */ 146 MINIMISE_STATE, 147 /** 148 * Don't increment QNAME this iteration 149 */ 150 SKIP_MINIMISE_STATE, 151 /** 152 * Send out full QNAME + original QTYPE 153 */ 154 DONOT_MINIMISE_STATE, 155 }; 156 157 /** 158 * State of the iterator for a query. 159 */ 160 enum iter_state { 161 /** 162 * Externally generated queries start at this state. Query restarts are 163 * reset to this state. 164 */ 165 INIT_REQUEST_STATE = 0, 166 167 /** 168 * Root priming events reactivate here, most other events pass 169 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 170 */ 171 INIT_REQUEST_2_STATE, 172 173 /** 174 * Stub priming events reactivate here, most other events pass 175 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 176 */ 177 INIT_REQUEST_3_STATE, 178 179 /** 180 * Each time a delegation point changes for a given query or a 181 * query times out and/or wakes up, this state is (re)visited. 182 * This state is reponsible for iterating through a list of 183 * nameserver targets. 184 */ 185 QUERYTARGETS_STATE, 186 187 /** 188 * Responses to queries start at this state. This state handles 189 * the decision tree associated with handling responses. 190 */ 191 QUERY_RESP_STATE, 192 193 /** Responses to priming queries finish at this state. */ 194 PRIME_RESP_STATE, 195 196 /** Collecting query class information, for qclass=ANY, when 197 * it spawns off queries for every class, it returns here. */ 198 COLLECT_CLASS_STATE, 199 200 /** Find NS record to resolve DS record from, walking to the right 201 * NS spot until we find it */ 202 DSNS_FIND_STATE, 203 204 /** Responses that are to be returned upstream end at this state. 205 * As well as responses to target queries. */ 206 FINISHED_STATE 207 }; 208 209 /** 210 * Per query state for the iterator module. 211 */ 212 struct iter_qstate { 213 /** 214 * State of the iterator module. 215 * This is the state that event is in or should sent to -- all 216 * requests should start with the INIT_REQUEST_STATE. All 217 * responses should start with QUERY_RESP_STATE. Subsequent 218 * processing of the event will change this state. 219 */ 220 enum iter_state state; 221 222 /** 223 * Final state for the iterator module. 224 * This is the state that responses should be routed to once the 225 * response is final. For externally initiated queries, this 226 * will be FINISHED_STATE, locally initiated queries will have 227 * different final states. 228 */ 229 enum iter_state final_state; 230 231 /** 232 * The depth of this query, this means the depth of recursion. 233 * This address is needed for another query, which is an address 234 * needed for another query, etc. Original client query has depth 0. 235 */ 236 int depth; 237 238 /** 239 * The response 240 */ 241 struct dns_msg* response; 242 243 /** 244 * This is a list of RRsets that must be prepended to the 245 * ANSWER section of a response before being sent upstream. 246 */ 247 struct iter_prep_list* an_prepend_list; 248 /** Last element of the prepend list */ 249 struct iter_prep_list* an_prepend_last; 250 251 /** 252 * This is the list of RRsets that must be prepended to the 253 * AUTHORITY section of the response before being sent upstream. 254 */ 255 struct iter_prep_list* ns_prepend_list; 256 /** Last element of the authority prepend list */ 257 struct iter_prep_list* ns_prepend_last; 258 259 /** query name used for chasing the results. Initially the same as 260 * the state qinfo, but after CNAMEs this will be different. 261 * The query info used to elicit the results needed. */ 262 struct query_info qchase; 263 /** query flags to use when chasing the answer (i.e. RD flag) */ 264 uint16_t chase_flags; 265 /** true if we set RD bit because of last resort recursion lame query*/ 266 int chase_to_rd; 267 268 /** 269 * This is the current delegation point for an in-progress query. This 270 * object retains state as to which delegation targets need to be 271 * (sub)queried for vs which ones have already been visited. 272 */ 273 struct delegpt* dp; 274 275 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 276 int caps_fallback; 277 /** state for capsfail: current server number to try */ 278 size_t caps_server; 279 /** state for capsfail: stored query for comparisons. Can be NULL if 280 * no response had been seen prior to starting the fallback. */ 281 struct reply_info* caps_reply; 282 struct dns_msg* caps_response; 283 284 /** Current delegation message - returned for non-RD queries */ 285 struct dns_msg* deleg_msg; 286 287 /** number of outstanding target sub queries */ 288 int num_target_queries; 289 290 /** outstanding direct queries */ 291 int num_current_queries; 292 293 /** the number of times this query has been restarted. */ 294 int query_restart_count; 295 296 /** the number of times this query as followed a referral. */ 297 int referral_count; 298 299 /** number of queries fired off */ 300 int sent_count; 301 302 /** number of target queries spawned in [1], for this query and its 303 * subqueries, the malloced-array is shared, [0] refcount. */ 304 int* target_count; 305 306 /** if true, already tested for ratelimiting and passed the test */ 307 int ratelimit_ok; 308 309 /** 310 * The query must store NS records from referrals as parentside RRs 311 * Enabled once it hits resolution problems, to throttle retries. 312 * If enabled it is the pointer to the old delegation point with 313 * the old retry counts for bad-nameserver-addresses. 314 */ 315 struct delegpt* store_parent_NS; 316 317 /** 318 * The query is for parent-side glue(A or AAAA) for a nameserver. 319 * If the item is seen as glue in a referral, and pside_glue is NULL, 320 * then it is stored in pside_glue for later. 321 * If it was never seen, at the end, then a negative caching element 322 * must be created. 323 * The (data or negative) RR cache element then throttles retries. 324 */ 325 int query_for_pside_glue; 326 /** the parent-side-glue element (NULL if none, its first match) */ 327 struct ub_packed_rrset_key* pside_glue; 328 329 /** If nonNULL we are walking upwards from DS query to find NS */ 330 uint8_t* dsns_point; 331 /** length of the dname in dsns_point */ 332 size_t dsns_point_len; 333 334 /** 335 * expected dnssec information for this iteration step. 336 * If dnssec rrsigs are expected and not given, the server is marked 337 * lame (dnssec-lame). 338 */ 339 int dnssec_expected; 340 341 /** 342 * We are expecting dnssec information, but we also know the server 343 * is DNSSEC lame. The response need not be marked dnssec-lame again. 344 */ 345 int dnssec_lame_query; 346 347 /** 348 * This is flag that, if true, means that this event is 349 * waiting for a stub priming query. 350 */ 351 int wait_priming_stub; 352 353 /** 354 * This is a flag that, if true, means that this query is 355 * for (re)fetching glue from a zone. Since the address should 356 * have been glue, query again to the servers that should have 357 * been returning it as glue. 358 * The delegation point must be set to the one that should *not* 359 * be used when creating the state. A higher one will be attempted. 360 */ 361 int refetch_glue; 362 363 /** list of pending queries to authoritative servers. */ 364 struct outbound_list outlist; 365 366 /** QNAME minimisation state, RFC7816 */ 367 enum minimisation_state minimisation_state; 368 369 /** 370 * The query info that is sent upstream. Will be a subset of qchase 371 * when qname minimisation is enabled. 372 */ 373 struct query_info qinfo_out; 374 375 /** 376 * Count number of QNAME minisation iterations. Used to limit number of 377 * outgoing queries when QNAME minimisation is enabled. 378 */ 379 int minimise_count; 380 }; 381 382 /** 383 * List of prepend items 384 */ 385 struct iter_prep_list { 386 /** next in list */ 387 struct iter_prep_list* next; 388 /** rrset */ 389 struct ub_packed_rrset_key* rrset; 390 }; 391 392 /** 393 * Get the iterator function block. 394 * @return: function block with function pointers to iterator methods. 395 */ 396 struct module_func_block* iter_get_funcblock(void); 397 398 /** 399 * Get iterator state as a string 400 * @param state: to convert 401 * @return constant string that is printable. 402 */ 403 const char* iter_state_to_string(enum iter_state state); 404 405 /** 406 * See if iterator state is a response state 407 * @param s: to inspect 408 * @return true if response state. 409 */ 410 int iter_state_is_responsestate(enum iter_state s); 411 412 /** iterator init */ 413 int iter_init(struct module_env* env, int id); 414 415 /** iterator deinit */ 416 void iter_deinit(struct module_env* env, int id); 417 418 /** iterator operate on a query */ 419 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 420 struct outbound_entry* outbound); 421 422 /** 423 * Return priming query results to interestes super querystates. 424 * 425 * Sets the delegation point and delegation message (not nonRD queries). 426 * This is a callback from walk_supers. 427 * 428 * @param qstate: query state that finished. 429 * @param id: module id. 430 * @param super: the qstate to inform. 431 */ 432 void iter_inform_super(struct module_qstate* qstate, int id, 433 struct module_qstate* super); 434 435 /** iterator cleanup query state */ 436 void iter_clear(struct module_qstate* qstate, int id); 437 438 /** iterator alloc size routine */ 439 size_t iter_get_mem(struct module_env* env, int id); 440 441 #endif /* ITERATOR_ITERATOR_H */ 442