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 LIMITED 25 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 26 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE 27 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 28 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 29 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 30 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 31 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 32 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 33 * 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 55 /** max number of query restarts. Determines max number of CNAME chain. */ 56 #define MAX_RESTART_COUNT 8 57 /** max number of referrals. Makes sure resolver does not run away */ 58 #define MAX_REFERRAL_COUNT 130 59 /** max number of queries-sent-out. Make sure large NS set does not loop */ 60 #define MAX_SENT_COUNT 16 61 /** at what query-sent-count to stop target fetch policy */ 62 #define TARGET_FETCH_STOP 3 63 /** how nice is a server without further information, in msec 64 * Equals rtt initial timeout value. 65 */ 66 #define UNKNOWN_SERVER_NICENESS 376 67 /** maximum timeout before a host is deemed unsuitable, in msec. 68 * After host_ttl this will be timed out and the host will be tried again. 69 * Equals RTT_MAX_TIMEOUT 70 */ 71 #define USEFUL_SERVER_TOP_TIMEOUT 120000 72 /** Number of lost messages in a row that get a host blacklisted. 73 * With 16, a couple different queries have to time out and no working 74 * queries are happening */ 75 #define USEFUL_SERVER_MAX_LOST 16 76 /** number of retries on outgoing queries */ 77 #define OUTBOUND_MSG_RETRY 5 78 /** RTT band, within this amount from the best, servers are chosen randomly. 79 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 80 * fast server, this causes server exploration as a side benefit. msec. */ 81 #define RTT_BAND 400 82 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */ 83 #define INFRA_BACKOFF_INITIAL 240 84 85 /** 86 * Global state for the iterator. 87 */ 88 struct iter_env { 89 /** 90 * The hints -- these aren't stored in the cache because they don't 91 * expire. The hints are always used to "prime" the cache. Note 92 * that both root hints and stub zone "hints" are stored in this 93 * data structure. 94 */ 95 struct iter_hints* hints; 96 97 /** A flag to indicate whether or not we have an IPv6 route */ 98 int supports_ipv6; 99 100 /** A flag to indicate whether or not we have an IPv4 route */ 101 int supports_ipv4; 102 103 /** A set of inetaddrs that should never be queried. */ 104 struct iter_donotq* donotq; 105 106 /** private address space and private domains */ 107 struct iter_priv* priv; 108 109 /** The maximum dependency depth that this resolver will pursue. */ 110 int max_dependency_depth; 111 112 /** 113 * The target fetch policy for each dependency level. This is 114 * described as a simple number (per dependency level): 115 * negative numbers (usually just -1) mean fetch-all, 116 * 0 means only fetch on demand, and 117 * positive numbers mean to fetch at most that many targets. 118 * array of max_dependency_depth+1 size. 119 */ 120 int* target_fetch_policy; 121 }; 122 123 /** 124 * State of the iterator for a query. 125 */ 126 enum iter_state { 127 /** 128 * Externally generated queries start at this state. Query restarts are 129 * reset to this state. 130 */ 131 INIT_REQUEST_STATE = 0, 132 133 /** 134 * Root priming events reactivate here, most other events pass 135 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 136 */ 137 INIT_REQUEST_2_STATE, 138 139 /** 140 * Stub priming events reactivate here, most other events pass 141 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 142 */ 143 INIT_REQUEST_3_STATE, 144 145 /** 146 * Each time a delegation point changes for a given query or a 147 * query times out and/or wakes up, this state is (re)visited. 148 * This state is reponsible for iterating through a list of 149 * nameserver targets. 150 */ 151 QUERYTARGETS_STATE, 152 153 /** 154 * Responses to queries start at this state. This state handles 155 * the decision tree associated with handling responses. 156 */ 157 QUERY_RESP_STATE, 158 159 /** Responses to priming queries finish at this state. */ 160 PRIME_RESP_STATE, 161 162 /** Collecting query class information, for qclass=ANY, when 163 * it spawns off queries for every class, it returns here. */ 164 COLLECT_CLASS_STATE, 165 166 /** Responses that are to be returned upstream end at this state. 167 * As well as responses to target queries. */ 168 FINISHED_STATE 169 }; 170 171 /** 172 * Per query state for the iterator module. 173 */ 174 struct iter_qstate { 175 /** 176 * State of the iterator module. 177 * This is the state that event is in or should sent to -- all 178 * requests should start with the INIT_REQUEST_STATE. All 179 * responses should start with QUERY_RESP_STATE. Subsequent 180 * processing of the event will change this state. 181 */ 182 enum iter_state state; 183 184 /** 185 * Final state for the iterator module. 186 * This is the state that responses should be routed to once the 187 * response is final. For externally initiated queries, this 188 * will be FINISHED_STATE, locally initiated queries will have 189 * different final states. 190 */ 191 enum iter_state final_state; 192 193 /** 194 * The depth of this query, this means the depth of recursion. 195 * This address is needed for another query, which is an address 196 * needed for another query, etc. Original client query has depth 0. 197 */ 198 int depth; 199 200 /** 201 * The response 202 */ 203 struct dns_msg* response; 204 205 /** 206 * This is a list of RRsets that must be prepended to the 207 * ANSWER section of a response before being sent upstream. 208 */ 209 struct iter_prep_list* an_prepend_list; 210 /** Last element of the prepend list */ 211 struct iter_prep_list* an_prepend_last; 212 213 /** 214 * This is the list of RRsets that must be prepended to the 215 * AUTHORITY section of the response before being sent upstream. 216 */ 217 struct iter_prep_list* ns_prepend_list; 218 /** Last element of the authority prepend list */ 219 struct iter_prep_list* ns_prepend_last; 220 221 /** query name used for chasing the results. Initially the same as 222 * the state qinfo, but after CNAMEs this will be different. 223 * The query info used to elicit the results needed. */ 224 struct query_info qchase; 225 /** query flags to use when chasing the answer (i.e. RD flag) */ 226 uint16_t chase_flags; 227 /** true if we set RD bit because of last resort recursion lame query*/ 228 int chase_to_rd; 229 230 /** 231 * This is the current delegation point for an in-progress query. This 232 * object retains state as to which delegation targets need to be 233 * (sub)queried for vs which ones have already been visited. 234 */ 235 struct delegpt* dp; 236 237 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 238 int caps_fallback; 239 /** state for capsfail: current server number to try */ 240 size_t caps_server; 241 /** state for capsfail: stored query for comparisons */ 242 struct reply_info* caps_reply; 243 244 /** Current delegation message - returned for non-RD queries */ 245 struct dns_msg* deleg_msg; 246 247 /** number of outstanding target sub queries */ 248 int num_target_queries; 249 250 /** outstanding direct queries */ 251 int num_current_queries; 252 253 /** the number of times this query has been restarted. */ 254 int query_restart_count; 255 256 /** the number of times this query as followed a referral. */ 257 int referral_count; 258 259 /** number of queries fired off */ 260 int sent_count; 261 262 /** 263 * The query must store NS records from referrals as parentside RRs 264 * Enabled once it hits resolution problems, to throttle retries. 265 * If enabled it is the pointer to the old delegation point with 266 * the old retry counts for bad-nameserver-addresses. 267 */ 268 struct delegpt* store_parent_NS; 269 270 /** 271 * The query is for parent-side glue(A or AAAA) for a nameserver. 272 * If the item is seen as glue in a referral, and pside_glue is NULL, 273 * then it is stored in pside_glue for later. 274 * If it was never seen, at the end, then a negative caching element 275 * must be created. 276 * The (data or negative) RR cache element then throttles retries. 277 */ 278 int query_for_pside_glue; 279 /** the parent-side-glue element (NULL if none, its first match) */ 280 struct ub_packed_rrset_key* pside_glue; 281 282 /** 283 * expected dnssec information for this iteration step. 284 * If dnssec rrsigs are expected and not given, the server is marked 285 * lame (dnssec-lame). 286 */ 287 int dnssec_expected; 288 289 /** 290 * We are expecting dnssec information, but we also know the server 291 * is DNSSEC lame. The response need not be marked dnssec-lame again. 292 */ 293 int dnssec_lame_query; 294 295 /** 296 * This is flag that, if true, means that this event is 297 * waiting for a stub priming query. 298 */ 299 int wait_priming_stub; 300 301 /** 302 * This is a flag that, if true, means that this query is 303 * for (re)fetching glue from a zone. Since the address should 304 * have been glue, query again to the servers that should have 305 * been returning it as glue. 306 * The delegation point must be set to the one that should *not* 307 * be used when creating the state. A higher one will be attempted. 308 */ 309 int refetch_glue; 310 311 /** list of pending queries to authoritative servers. */ 312 struct outbound_list outlist; 313 }; 314 315 /** 316 * List of prepend items 317 */ 318 struct iter_prep_list { 319 /** next in list */ 320 struct iter_prep_list* next; 321 /** rrset */ 322 struct ub_packed_rrset_key* rrset; 323 }; 324 325 /** 326 * Get the iterator function block. 327 * @return: function block with function pointers to iterator methods. 328 */ 329 struct module_func_block* iter_get_funcblock(void); 330 331 /** 332 * Get iterator state as a string 333 * @param state: to convert 334 * @return constant string that is printable. 335 */ 336 const char* iter_state_to_string(enum iter_state state); 337 338 /** 339 * See if iterator state is a response state 340 * @param s: to inspect 341 * @return true if response state. 342 */ 343 int iter_state_is_responsestate(enum iter_state s); 344 345 /** iterator init */ 346 int iter_init(struct module_env* env, int id); 347 348 /** iterator deinit */ 349 void iter_deinit(struct module_env* env, int id); 350 351 /** iterator operate on a query */ 352 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 353 struct outbound_entry* outbound); 354 355 /** 356 * Return priming query results to interestes super querystates. 357 * 358 * Sets the delegation point and delegation message (not nonRD queries). 359 * This is a callback from walk_supers. 360 * 361 * @param qstate: query state that finished. 362 * @param id: module id. 363 * @param super: the qstate to inform. 364 */ 365 void iter_inform_super(struct module_qstate* qstate, int id, 366 struct module_qstate* super); 367 368 /** iterator cleanup query state */ 369 void iter_clear(struct module_qstate* qstate, int id); 370 371 /** iterator alloc size routine */ 372 size_t iter_get_mem(struct module_env* env, int id); 373 374 #endif /* ITERATOR_ITERATOR_H */ 375