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