2 * iterator/iterator.h - iterative resolver DNS query response module
4 * Copyright (c) 2007, NLnet Labs. All rights reserved.
6 * This software is open source.
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
12 * Redistributions of source code must retain the above copyright notice,
13 * this list of conditions and the following disclaimer.
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.
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.
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.
39 * This file contains a module that performs recusive iterative DNS query
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"
52 struct iter_prep_list;
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 32
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.
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
71 #define USEFUL_SERVER_TOP_TIMEOUT 120000
72 /** number of retries on outgoing queries */
73 #define OUTBOUND_MSG_RETRY 5
74 /** RTT band, within this amount from the best, servers are chosen randomly.
75 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a
76 * fast server, this causes server exploration as a side benefit. msec. */
78 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */
79 #define INFRA_BACKOFF_INITIAL 240
82 * Global state for the iterator.
85 /** A flag to indicate whether or not we have an IPv6 route */
88 /** A flag to indicate whether or not we have an IPv4 route */
91 /** A set of inetaddrs that should never be queried. */
92 struct iter_donotq* donotq;
94 /** private address space and private domains */
95 struct iter_priv* priv;
97 /** The maximum dependency depth that this resolver will pursue. */
98 int max_dependency_depth;
101 * The target fetch policy for each dependency level. This is
102 * described as a simple number (per dependency level):
103 * negative numbers (usually just -1) mean fetch-all,
104 * 0 means only fetch on demand, and
105 * positive numbers mean to fetch at most that many targets.
106 * array of max_dependency_depth+1 size.
108 int* target_fetch_policy;
112 * State of the iterator for a query.
116 * Externally generated queries start at this state. Query restarts are
117 * reset to this state.
119 INIT_REQUEST_STATE = 0,
122 * Root priming events reactivate here, most other events pass
123 * through this naturally as the 2nd part of the INIT_REQUEST_STATE.
125 INIT_REQUEST_2_STATE,
128 * Stub priming events reactivate here, most other events pass
129 * through this naturally as the 3rd part of the INIT_REQUEST_STATE.
131 INIT_REQUEST_3_STATE,
134 * Each time a delegation point changes for a given query or a
135 * query times out and/or wakes up, this state is (re)visited.
136 * This state is reponsible for iterating through a list of
137 * nameserver targets.
142 * Responses to queries start at this state. This state handles
143 * the decision tree associated with handling responses.
147 /** Responses to priming queries finish at this state. */
150 /** Collecting query class information, for qclass=ANY, when
151 * it spawns off queries for every class, it returns here. */
154 /** Find NS record to resolve DS record from, walking to the right
155 * NS spot until we find it */
158 /** Responses that are to be returned upstream end at this state.
159 * As well as responses to target queries. */
164 * Per query state for the iterator module.
168 * State of the iterator module.
169 * This is the state that event is in or should sent to -- all
170 * requests should start with the INIT_REQUEST_STATE. All
171 * responses should start with QUERY_RESP_STATE. Subsequent
172 * processing of the event will change this state.
174 enum iter_state state;
177 * Final state for the iterator module.
178 * This is the state that responses should be routed to once the
179 * response is final. For externally initiated queries, this
180 * will be FINISHED_STATE, locally initiated queries will have
181 * different final states.
183 enum iter_state final_state;
186 * The depth of this query, this means the depth of recursion.
187 * This address is needed for another query, which is an address
188 * needed for another query, etc. Original client query has depth 0.
195 struct dns_msg* response;
198 * This is a list of RRsets that must be prepended to the
199 * ANSWER section of a response before being sent upstream.
201 struct iter_prep_list* an_prepend_list;
202 /** Last element of the prepend list */
203 struct iter_prep_list* an_prepend_last;
206 * This is the list of RRsets that must be prepended to the
207 * AUTHORITY section of the response before being sent upstream.
209 struct iter_prep_list* ns_prepend_list;
210 /** Last element of the authority prepend list */
211 struct iter_prep_list* ns_prepend_last;
213 /** query name used for chasing the results. Initially the same as
214 * the state qinfo, but after CNAMEs this will be different.
215 * The query info used to elicit the results needed. */
216 struct query_info qchase;
217 /** query flags to use when chasing the answer (i.e. RD flag) */
218 uint16_t chase_flags;
219 /** true if we set RD bit because of last resort recursion lame query*/
223 * This is the current delegation point for an in-progress query. This
224 * object retains state as to which delegation targets need to be
225 * (sub)queried for vs which ones have already been visited.
229 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */
231 /** state for capsfail: current server number to try */
233 /** state for capsfail: stored query for comparisons. Can be NULL if
234 * no response had been seen prior to starting the fallback. */
235 struct reply_info* caps_reply;
237 /** Current delegation message - returned for non-RD queries */
238 struct dns_msg* deleg_msg;
240 /** number of outstanding target sub queries */
241 int num_target_queries;
243 /** outstanding direct queries */
244 int num_current_queries;
246 /** the number of times this query has been restarted. */
247 int query_restart_count;
249 /** the number of times this query as followed a referral. */
252 /** number of queries fired off */
256 * The query must store NS records from referrals as parentside RRs
257 * Enabled once it hits resolution problems, to throttle retries.
258 * If enabled it is the pointer to the old delegation point with
259 * the old retry counts for bad-nameserver-addresses.
261 struct delegpt* store_parent_NS;
264 * The query is for parent-side glue(A or AAAA) for a nameserver.
265 * If the item is seen as glue in a referral, and pside_glue is NULL,
266 * then it is stored in pside_glue for later.
267 * If it was never seen, at the end, then a negative caching element
269 * The (data or negative) RR cache element then throttles retries.
271 int query_for_pside_glue;
272 /** the parent-side-glue element (NULL if none, its first match) */
273 struct ub_packed_rrset_key* pside_glue;
275 /** If nonNULL we are walking upwards from DS query to find NS */
277 /** length of the dname in dsns_point */
278 size_t dsns_point_len;
281 * expected dnssec information for this iteration step.
282 * If dnssec rrsigs are expected and not given, the server is marked
283 * lame (dnssec-lame).
288 * We are expecting dnssec information, but we also know the server
289 * is DNSSEC lame. The response need not be marked dnssec-lame again.
291 int dnssec_lame_query;
294 * This is flag that, if true, means that this event is
295 * waiting for a stub priming query.
297 int wait_priming_stub;
300 * This is a flag that, if true, means that this query is
301 * for (re)fetching glue from a zone. Since the address should
302 * have been glue, query again to the servers that should have
303 * been returning it as glue.
304 * The delegation point must be set to the one that should *not*
305 * be used when creating the state. A higher one will be attempted.
309 /** list of pending queries to authoritative servers. */
310 struct outbound_list outlist;
314 * List of prepend items
316 struct iter_prep_list {
318 struct iter_prep_list* next;
320 struct ub_packed_rrset_key* rrset;
324 * Get the iterator function block.
325 * @return: function block with function pointers to iterator methods.
327 struct module_func_block* iter_get_funcblock(void);
330 * Get iterator state as a string
331 * @param state: to convert
332 * @return constant string that is printable.
334 const char* iter_state_to_string(enum iter_state state);
337 * See if iterator state is a response state
338 * @param s: to inspect
339 * @return true if response state.
341 int iter_state_is_responsestate(enum iter_state s);
344 int iter_init(struct module_env* env, int id);
346 /** iterator deinit */
347 void iter_deinit(struct module_env* env, int id);
349 /** iterator operate on a query */
350 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id,
351 struct outbound_entry* outbound);
354 * Return priming query results to interestes super querystates.
356 * Sets the delegation point and delegation message (not nonRD queries).
357 * This is a callback from walk_supers.
359 * @param qstate: query state that finished.
360 * @param id: module id.
361 * @param super: the qstate to inform.
363 void iter_inform_super(struct module_qstate* qstate, int id,
364 struct module_qstate* super);
366 /** iterator cleanup query state */
367 void iter_clear(struct module_qstate* qstate, int id);
369 /** iterator alloc size routine */
370 size_t iter_get_mem(struct module_env* env, int id);
372 #endif /* ITERATOR_ITERATOR_H */