2 * iterator/iterator.h - iterative resolver DNS query response module
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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 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.
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
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. */
84 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */
85 #define INFRA_BACKOFF_INITIAL 240
88 * Global state for the iterator.
91 /** A flag to indicate whether or not we have an IPv6 route */
94 /** A flag to indicate whether or not we have an IPv4 route */
97 /** A set of inetaddrs that should never be queried. */
98 struct iter_donotq* donotq;
100 /** private address space and private domains */
101 struct iter_priv* priv;
103 /** The maximum dependency depth that this resolver will pursue. */
104 int max_dependency_depth;
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.
114 int* target_fetch_policy;
118 * State of the iterator for a query.
122 * Externally generated queries start at this state. Query restarts are
123 * reset to this state.
125 INIT_REQUEST_STATE = 0,
128 * Root priming events reactivate here, most other events pass
129 * through this naturally as the 2nd part of the INIT_REQUEST_STATE.
131 INIT_REQUEST_2_STATE,
134 * Stub priming events reactivate here, most other events pass
135 * through this naturally as the 3rd part of the INIT_REQUEST_STATE.
137 INIT_REQUEST_3_STATE,
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.
148 * Responses to queries start at this state. This state handles
149 * the decision tree associated with handling responses.
153 /** Responses to priming queries finish at this state. */
156 /** Collecting query class information, for qclass=ANY, when
157 * it spawns off queries for every class, it returns here. */
160 /** Find NS record to resolve DS record from, walking to the right
161 * NS spot until we find it */
164 /** Responses that are to be returned upstream end at this state.
165 * As well as responses to target queries. */
170 * Per query state for the iterator module.
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.
180 enum iter_state state;
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.
189 enum iter_state final_state;
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.
201 struct dns_msg* response;
204 * This is a list of RRsets that must be prepended to the
205 * ANSWER section of a response before being sent upstream.
207 struct iter_prep_list* an_prepend_list;
208 /** Last element of the prepend list */
209 struct iter_prep_list* an_prepend_last;
212 * This is the list of RRsets that must be prepended to the
213 * AUTHORITY section of the response before being sent upstream.
215 struct iter_prep_list* ns_prepend_list;
216 /** Last element of the authority prepend list */
217 struct iter_prep_list* ns_prepend_last;
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*/
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.
235 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */
237 /** state for capsfail: current server number to try */
239 /** state for capsfail: stored query for comparisons */
240 struct reply_info* caps_reply;
242 /** Current delegation message - returned for non-RD queries */
243 struct dns_msg* deleg_msg;
245 /** number of outstanding target sub queries */
246 int num_target_queries;
248 /** outstanding direct queries */
249 int num_current_queries;
251 /** the number of times this query has been restarted. */
252 int query_restart_count;
254 /** the number of times this query as followed a referral. */
257 /** number of queries fired off */
260 /** number of target queries spawned in [1], for this query and its
261 * subqueries, the malloced-array is shared, [0] refcount. */
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.
270 struct delegpt* store_parent_NS;
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
278 * The (data or negative) RR cache element then throttles retries.
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;
284 /** If nonNULL we are walking upwards from DS query to find NS */
286 /** length of the dname in dsns_point */
287 size_t dsns_point_len;
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).
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.
300 int dnssec_lame_query;
303 * This is flag that, if true, means that this event is
304 * waiting for a stub priming query.
306 int wait_priming_stub;
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.
318 /** list of pending queries to authoritative servers. */
319 struct outbound_list outlist;
323 * List of prepend items
325 struct iter_prep_list {
327 struct iter_prep_list* next;
329 struct ub_packed_rrset_key* rrset;
333 * Get the iterator function block.
334 * @return: function block with function pointers to iterator methods.
336 struct module_func_block* iter_get_funcblock(void);
339 * Get iterator state as a string
340 * @param state: to convert
341 * @return constant string that is printable.
343 const char* iter_state_to_string(enum iter_state state);
346 * See if iterator state is a response state
347 * @param s: to inspect
348 * @return true if response state.
350 int iter_state_is_responsestate(enum iter_state s);
353 int iter_init(struct module_env* env, int id);
355 /** iterator deinit */
356 void iter_deinit(struct module_env* env, int id);
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);
363 * Return priming query results to interestes super querystates.
365 * Sets the delegation point and delegation message (not nonRD queries).
366 * This is a callback from walk_supers.
368 * @param qstate: query state that finished.
369 * @param id: module id.
370 * @param super: the qstate to inform.
372 void iter_inform_super(struct module_qstate* qstate, int id,
373 struct module_qstate* super);
375 /** iterator cleanup query state */
376 void iter_clear(struct module_qstate* qstate, int id);
378 /** iterator alloc size routine */
379 size_t iter_get_mem(struct module_env* env, int id);
381 #endif /* ITERATOR_ITERATOR_H */