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 55 /** max number of targets spawned for a query and its subqueries */ 56 #define MAX_TARGET_COUNT 32 57 /** max number of query restarts. Determines max number of CNAME chain. */ 58 #define MAX_RESTART_COUNT 8 59 /** max number of referrals. Makes sure resolver does not run away */ 60 #define MAX_REFERRAL_COUNT 130 61 /** max number of queries-sent-out. Make sure large NS set does not loop */ 62 #define MAX_SENT_COUNT 16 63 /** at what query-sent-count to stop target fetch policy */ 64 #define TARGET_FETCH_STOP 3 65 /** how nice is a server without further information, in msec 66 * Equals rtt initial timeout value. 67 */ 68 #define UNKNOWN_SERVER_NICENESS 376 69 /** maximum timeout before a host is deemed unsuitable, in msec. 70 * After host_ttl this will be timed out and the host will be tried again. 71 * Equals RTT_MAX_TIMEOUT 72 */ 73 #define USEFUL_SERVER_TOP_TIMEOUT 120000 74 /** Number of lost messages in a row that get a host blacklisted. 75 * With 16, a couple different queries have to time out and no working 76 * queries are happening */ 77 #define USEFUL_SERVER_MAX_LOST 16 78 /** number of retries on outgoing queries */ 79 #define OUTBOUND_MSG_RETRY 5 80 /** RTT band, within this amount from the best, servers are chosen randomly. 81 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a 82 * fast server, this causes server exploration as a side benefit. msec. */ 83 #define RTT_BAND 400 84 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */ 85 #define INFRA_BACKOFF_INITIAL 240 86 87 /** 88 * Global state for the iterator. 89 */ 90 struct iter_env { 91 /** A flag to indicate whether or not we have an IPv6 route */ 92 int supports_ipv6; 93 94 /** A flag to indicate whether or not we have an IPv4 route */ 95 int supports_ipv4; 96 97 /** A set of inetaddrs that should never be queried. */ 98 struct iter_donotq* donotq; 99 100 /** private address space and private domains */ 101 struct iter_priv* priv; 102 103 /** The maximum dependency depth that this resolver will pursue. */ 104 int max_dependency_depth; 105 106 /** 107 * The target fetch policy for each dependency level. This is 108 * described as a simple number (per dependency level): 109 * negative numbers (usually just -1) mean fetch-all, 110 * 0 means only fetch on demand, and 111 * positive numbers mean to fetch at most that many targets. 112 * array of max_dependency_depth+1 size. 113 */ 114 int* target_fetch_policy; 115 }; 116 117 /** 118 * State of the iterator for a query. 119 */ 120 enum iter_state { 121 /** 122 * Externally generated queries start at this state. Query restarts are 123 * reset to this state. 124 */ 125 INIT_REQUEST_STATE = 0, 126 127 /** 128 * Root priming events reactivate here, most other events pass 129 * through this naturally as the 2nd part of the INIT_REQUEST_STATE. 130 */ 131 INIT_REQUEST_2_STATE, 132 133 /** 134 * Stub priming events reactivate here, most other events pass 135 * through this naturally as the 3rd part of the INIT_REQUEST_STATE. 136 */ 137 INIT_REQUEST_3_STATE, 138 139 /** 140 * Each time a delegation point changes for a given query or a 141 * query times out and/or wakes up, this state is (re)visited. 142 * This state is reponsible for iterating through a list of 143 * nameserver targets. 144 */ 145 QUERYTARGETS_STATE, 146 147 /** 148 * Responses to queries start at this state. This state handles 149 * the decision tree associated with handling responses. 150 */ 151 QUERY_RESP_STATE, 152 153 /** Responses to priming queries finish at this state. */ 154 PRIME_RESP_STATE, 155 156 /** Collecting query class information, for qclass=ANY, when 157 * it spawns off queries for every class, it returns here. */ 158 COLLECT_CLASS_STATE, 159 160 /** Find NS record to resolve DS record from, walking to the right 161 * NS spot until we find it */ 162 DSNS_FIND_STATE, 163 164 /** Responses that are to be returned upstream end at this state. 165 * As well as responses to target queries. */ 166 FINISHED_STATE 167 }; 168 169 /** 170 * Per query state for the iterator module. 171 */ 172 struct iter_qstate { 173 /** 174 * State of the iterator module. 175 * This is the state that event is in or should sent to -- all 176 * requests should start with the INIT_REQUEST_STATE. All 177 * responses should start with QUERY_RESP_STATE. Subsequent 178 * processing of the event will change this state. 179 */ 180 enum iter_state state; 181 182 /** 183 * Final state for the iterator module. 184 * This is the state that responses should be routed to once the 185 * response is final. For externally initiated queries, this 186 * will be FINISHED_STATE, locally initiated queries will have 187 * different final states. 188 */ 189 enum iter_state final_state; 190 191 /** 192 * The depth of this query, this means the depth of recursion. 193 * This address is needed for another query, which is an address 194 * needed for another query, etc. Original client query has depth 0. 195 */ 196 int depth; 197 198 /** 199 * The response 200 */ 201 struct dns_msg* response; 202 203 /** 204 * This is a list of RRsets that must be prepended to the 205 * ANSWER section of a response before being sent upstream. 206 */ 207 struct iter_prep_list* an_prepend_list; 208 /** Last element of the prepend list */ 209 struct iter_prep_list* an_prepend_last; 210 211 /** 212 * This is the list of RRsets that must be prepended to the 213 * AUTHORITY section of the response before being sent upstream. 214 */ 215 struct iter_prep_list* ns_prepend_list; 216 /** Last element of the authority prepend list */ 217 struct iter_prep_list* ns_prepend_last; 218 219 /** query name used for chasing the results. Initially the same as 220 * the state qinfo, but after CNAMEs this will be different. 221 * The query info used to elicit the results needed. */ 222 struct query_info qchase; 223 /** query flags to use when chasing the answer (i.e. RD flag) */ 224 uint16_t chase_flags; 225 /** true if we set RD bit because of last resort recursion lame query*/ 226 int chase_to_rd; 227 228 /** 229 * This is the current delegation point for an in-progress query. This 230 * object retains state as to which delegation targets need to be 231 * (sub)queried for vs which ones have already been visited. 232 */ 233 struct delegpt* dp; 234 235 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ 236 int caps_fallback; 237 /** state for capsfail: current server number to try */ 238 size_t caps_server; 239 /** state for capsfail: stored query for comparisons */ 240 struct reply_info* caps_reply; 241 242 /** Current delegation message - returned for non-RD queries */ 243 struct dns_msg* deleg_msg; 244 245 /** number of outstanding target sub queries */ 246 int num_target_queries; 247 248 /** outstanding direct queries */ 249 int num_current_queries; 250 251 /** the number of times this query has been restarted. */ 252 int query_restart_count; 253 254 /** the number of times this query as followed a referral. */ 255 int referral_count; 256 257 /** number of queries fired off */ 258 int sent_count; 259 260 /** number of target queries spawned in [1], for this query and its 261 * subqueries, the malloced-array is shared, [0] refcount. */ 262 int* target_count; 263 264 /** 265 * The query must store NS records from referrals as parentside RRs 266 * Enabled once it hits resolution problems, to throttle retries. 267 * If enabled it is the pointer to the old delegation point with 268 * the old retry counts for bad-nameserver-addresses. 269 */ 270 struct delegpt* store_parent_NS; 271 272 /** 273 * The query is for parent-side glue(A or AAAA) for a nameserver. 274 * If the item is seen as glue in a referral, and pside_glue is NULL, 275 * then it is stored in pside_glue for later. 276 * If it was never seen, at the end, then a negative caching element 277 * must be created. 278 * The (data or negative) RR cache element then throttles retries. 279 */ 280 int query_for_pside_glue; 281 /** the parent-side-glue element (NULL if none, its first match) */ 282 struct ub_packed_rrset_key* pside_glue; 283 284 /** If nonNULL we are walking upwards from DS query to find NS */ 285 uint8_t* dsns_point; 286 /** length of the dname in dsns_point */ 287 size_t dsns_point_len; 288 289 /** 290 * expected dnssec information for this iteration step. 291 * If dnssec rrsigs are expected and not given, the server is marked 292 * lame (dnssec-lame). 293 */ 294 int dnssec_expected; 295 296 /** 297 * We are expecting dnssec information, but we also know the server 298 * is DNSSEC lame. The response need not be marked dnssec-lame again. 299 */ 300 int dnssec_lame_query; 301 302 /** 303 * This is flag that, if true, means that this event is 304 * waiting for a stub priming query. 305 */ 306 int wait_priming_stub; 307 308 /** 309 * This is a flag that, if true, means that this query is 310 * for (re)fetching glue from a zone. Since the address should 311 * have been glue, query again to the servers that should have 312 * been returning it as glue. 313 * The delegation point must be set to the one that should *not* 314 * be used when creating the state. A higher one will be attempted. 315 */ 316 int refetch_glue; 317 318 /** list of pending queries to authoritative servers. */ 319 struct outbound_list outlist; 320 }; 321 322 /** 323 * List of prepend items 324 */ 325 struct iter_prep_list { 326 /** next in list */ 327 struct iter_prep_list* next; 328 /** rrset */ 329 struct ub_packed_rrset_key* rrset; 330 }; 331 332 /** 333 * Get the iterator function block. 334 * @return: function block with function pointers to iterator methods. 335 */ 336 struct module_func_block* iter_get_funcblock(void); 337 338 /** 339 * Get iterator state as a string 340 * @param state: to convert 341 * @return constant string that is printable. 342 */ 343 const char* iter_state_to_string(enum iter_state state); 344 345 /** 346 * See if iterator state is a response state 347 * @param s: to inspect 348 * @return true if response state. 349 */ 350 int iter_state_is_responsestate(enum iter_state s); 351 352 /** iterator init */ 353 int iter_init(struct module_env* env, int id); 354 355 /** iterator deinit */ 356 void iter_deinit(struct module_env* env, int id); 357 358 /** iterator operate on a query */ 359 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, 360 struct outbound_entry* outbound); 361 362 /** 363 * Return priming query results to interestes super querystates. 364 * 365 * Sets the delegation point and delegation message (not nonRD queries). 366 * This is a callback from walk_supers. 367 * 368 * @param qstate: query state that finished. 369 * @param id: module id. 370 * @param super: the qstate to inform. 371 */ 372 void iter_inform_super(struct module_qstate* qstate, int id, 373 struct module_qstate* super); 374 375 /** iterator cleanup query state */ 376 void iter_clear(struct module_qstate* qstate, int id); 377 378 /** iterator alloc size routine */ 379 size_t iter_get_mem(struct module_env* env, int id); 380 381 #endif /* ITERATOR_ITERATOR_H */ 382