2 * iterator/iterator.h - iterative resolver DNS query response module
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39 * This file contains a module that performs recursive 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;
56 /** max number of targets spawned for a query and its subqueries */
57 #define MAX_TARGET_COUNT 64
58 /** max number of target lookups per qstate, per delegation point */
59 #define MAX_DP_TARGET_COUNT 16
60 /** max number of nxdomains allowed for target lookups for a query and
62 #define MAX_TARGET_NX 5
63 /** max number of nxdomains allowed for target lookups for a query and
64 * its subqueries when fallback has kicked in */
65 #define MAX_TARGET_NX_FALLBACK (MAX_TARGET_NX*2)
66 /** max number of referrals. Makes sure resolver does not run away */
67 #define MAX_REFERRAL_COUNT 130
68 /** max number of queries for which to perform dnsseclameness detection,
69 * (rrsigs missing detection) after that, just pick up that response */
70 #define DNSSEC_LAME_DETECT_COUNT 4
72 * max number of QNAME minimisation iterations. Limits number of queries for
73 * QNAMEs with a lot of labels.
75 #define MAX_MINIMISE_COUNT 10
76 /* max number of time-outs for minimised query. Prevents resolving failures
77 * when the QNAME minimisation QTYPE is blocked. */
78 #define MAX_MINIMISE_TIMEOUT_COUNT 3
80 * number of labels from QNAME that are always send individually when using
81 * QNAME minimisation, even when the number of labels of the QNAME is bigger
82 * than MAX_MINIMISE_COUNT */
83 #define MINIMISE_ONE_LAB 4
84 #define MINIMISE_MULTIPLE_LABS (MAX_MINIMISE_COUNT - MINIMISE_ONE_LAB)
85 /** at what query-sent-count to stop target fetch policy */
86 #define TARGET_FETCH_STOP 3
87 /** how nice is a server without further information, in msec
88 * Equals rtt initial timeout value.
90 extern int UNKNOWN_SERVER_NICENESS;
91 /** maximum timeout before a host is deemed unsuitable, in msec.
92 * After host_ttl this will be timed out and the host will be tried again.
93 * Equals RTT_MAX_TIMEOUT, and thus when RTT_MAX_TIMEOUT is overwritten by
94 * config infra_cache_max_rtt, it will be overwritten as well. */
95 extern int USEFUL_SERVER_TOP_TIMEOUT;
96 /** penalty to validation failed blacklisted IPs
97 * Equals USEFUL_SERVER_TOP_TIMEOUT*4, and thus when RTT_MAX_TIMEOUT is
98 * overwritten by config infra_cache_max_rtt, it will be overwritten as well. */
99 extern int BLACKLIST_PENALTY;
100 /** RTT band, within this amount from the best, servers are chosen randomly.
101 * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a
102 * fast server, this causes server exploration as a side benefit. msec. */
104 /** Number of retries for empty nodata packets before it is accepted. */
105 #define EMPTY_NODATA_RETRY_COUNT 2
108 * Global state for the iterator.
111 /** A flag to indicate whether or not we have an IPv6 route */
114 /** A flag to indicate whether or not we have an IPv4 route */
117 /** A flag to locally apply NAT64 to make IPv4 addrs into IPv6 */
120 /** NAT64 prefix address, cf. dns64_env->prefix_addr */
121 struct sockaddr_storage nat64_prefix_addr;
123 /** sizeof(sockaddr_in6) */
124 socklen_t nat64_prefix_addrlen;
126 /** CIDR mask length of NAT64 prefix */
127 int nat64_prefix_net;
129 /** A set of inetaddrs that should never be queried. */
130 struct iter_donotq* donotq;
132 /** private address space and private domains */
133 struct iter_priv* priv;
135 /** whitelist for capsforid names */
136 struct rbtree_type* caps_white;
138 /** The maximum dependency depth that this resolver will pursue. */
139 int max_dependency_depth;
142 * The target fetch policy for each dependency level. This is
143 * described as a simple number (per dependency level):
144 * negative numbers (usually just -1) mean fetch-all,
145 * 0 means only fetch on demand, and
146 * positive numbers mean to fetch at most that many targets.
147 * array of max_dependency_depth+1 size.
149 int* target_fetch_policy;
151 /** lock on ratelimit counter */
152 lock_basic_type queries_ratelimit_lock;
153 /** number of queries that have been ratelimited */
154 size_t num_queries_ratelimited;
156 /** number of retries on outgoing queries */
157 int outbound_msg_retry;
159 /** number of queries_sent */
162 /** max number of query restarts to limit length of CNAME chain */
163 int max_query_restarts;
167 * QNAME minimisation state
169 enum minimisation_state {
171 * (Re)start minimisation. Outgoing QNAME should be set to dp->name.
172 * State entered on new query or after following referral or CNAME.
174 INIT_MINIMISE_STATE = 0,
176 * QNAME minimisation ongoing. Increase QNAME on every iteration.
180 * Don't increment QNAME this iteration
184 * Send out full QNAME + original QTYPE
186 DONOT_MINIMISE_STATE,
190 * State of the iterator for a query.
194 * Externally generated queries start at this state. Query restarts are
195 * reset to this state.
197 INIT_REQUEST_STATE = 0,
200 * Root priming events reactivate here, most other events pass
201 * through this naturally as the 2nd part of the INIT_REQUEST_STATE.
203 INIT_REQUEST_2_STATE,
206 * Stub priming events reactivate here, most other events pass
207 * through this naturally as the 3rd part of the INIT_REQUEST_STATE.
209 INIT_REQUEST_3_STATE,
212 * Each time a delegation point changes for a given query or a
213 * query times out and/or wakes up, this state is (re)visited.
214 * This state is responsible for iterating through a list of
215 * nameserver targets.
220 * Responses to queries start at this state. This state handles
221 * the decision tree associated with handling responses.
225 /** Responses to priming queries finish at this state. */
228 /** Collecting query class information, for qclass=ANY, when
229 * it spawns off queries for every class, it returns here. */
232 /** Find NS record to resolve DS record from, walking to the right
233 * NS spot until we find it */
236 /** Responses that are to be returned upstream end at this state.
237 * As well as responses to target queries. */
242 * Shared counters for queries.
244 enum target_count_variables {
245 /** Reference count for the shared iter_qstate->target_count. */
246 TARGET_COUNT_REF = 0,
247 /** Number of target queries spawned for the query and subqueries. */
248 TARGET_COUNT_QUERIES,
249 /** Number of nxdomain responses encountered. */
252 /** This should stay last here, it is used for the allocation */
257 * Per query state for the iterator module.
261 * State of the iterator module.
262 * This is the state that event is in or should sent to -- all
263 * requests should start with the INIT_REQUEST_STATE. All
264 * responses should start with QUERY_RESP_STATE. Subsequent
265 * processing of the event will change this state.
267 enum iter_state state;
270 * Final state for the iterator module.
271 * This is the state that responses should be routed to once the
272 * response is final. For externally initiated queries, this
273 * will be FINISHED_STATE, locally initiated queries will have
274 * different final states.
276 enum iter_state final_state;
279 * The depth of this query, this means the depth of recursion.
280 * This address is needed for another query, which is an address
281 * needed for another query, etc. Original client query has depth 0.
288 struct dns_msg* response;
291 * This is a list of RRsets that must be prepended to the
292 * ANSWER section of a response before being sent upstream.
294 struct iter_prep_list* an_prepend_list;
295 /** Last element of the prepend list */
296 struct iter_prep_list* an_prepend_last;
299 * This is the list of RRsets that must be prepended to the
300 * AUTHORITY section of the response before being sent upstream.
302 struct iter_prep_list* ns_prepend_list;
303 /** Last element of the authority prepend list */
304 struct iter_prep_list* ns_prepend_last;
306 /** query name used for chasing the results. Initially the same as
307 * the state qinfo, but after CNAMEs this will be different.
308 * The query info used to elicit the results needed. */
309 struct query_info qchase;
310 /** query flags to use when chasing the answer (i.e. RD flag) */
311 uint16_t chase_flags;
312 /** true if we set RD bit because of last resort recursion lame query*/
316 * This is the current delegation point for an in-progress query. This
317 * object retains state as to which delegation targets need to be
318 * (sub)queried for vs which ones have already been visited.
322 /** state for 0x20 fallback when capsfail happens, 0 not a fallback */
324 /** state for capsfail: current server number to try */
326 /** state for capsfail: stored query for comparisons. Can be NULL if
327 * no response had been seen prior to starting the fallback. */
328 struct reply_info* caps_reply;
329 struct dns_msg* caps_response;
331 /** Current delegation message - returned for non-RD queries */
332 struct dns_msg* deleg_msg;
334 /** number of outstanding target sub queries */
335 int num_target_queries;
337 /** outstanding direct queries */
338 int num_current_queries;
340 /** the number of times this query has been restarted. */
341 int query_restart_count;
343 /** the number of times this query has followed a referral. */
346 /** number of queries fired off */
349 /** malloced-array shared with this query and its subqueries. It keeps
350 * track of the defined enum target_count_variables counters. */
353 /** number of target lookups per delegation point. Reset to 0 after
354 * receiving referral answer. Not shared with subqueries. */
357 /** Delegation point that triggered the NXNS fallback; shared with
358 * this query and its subqueries, count-referenced by the reference
359 * counter in target_count.
360 * This also marks the fallback activation. */
363 /** if true, already tested for ratelimiting and passed the test */
367 * The query must store NS records from referrals as parentside RRs
368 * Enabled once it hits resolution problems, to throttle retries.
369 * If enabled it is the pointer to the old delegation point with
370 * the old retry counts for bad-nameserver-addresses.
372 struct delegpt* store_parent_NS;
375 * The query is for parent-side glue(A or AAAA) for a nameserver.
376 * If the item is seen as glue in a referral, and pside_glue is NULL,
377 * then it is stored in pside_glue for later.
378 * If it was never seen, at the end, then a negative caching element
380 * The (data or negative) RR cache element then throttles retries.
382 int query_for_pside_glue;
383 /** the parent-side-glue element (NULL if none, its first match) */
384 struct ub_packed_rrset_key* pside_glue;
386 /** If nonNULL we are walking upwards from DS query to find NS */
388 /** length of the dname in dsns_point */
389 size_t dsns_point_len;
392 * expected dnssec information for this iteration step.
393 * If dnssec rrsigs are expected and not given, the server is marked
394 * lame (dnssec-lame).
399 * We are expecting dnssec information, but we also know the server
400 * is DNSSEC lame. The response need not be marked dnssec-lame again.
402 int dnssec_lame_query;
405 * This is flag that, if true, means that this event is
406 * waiting for a stub priming query.
408 int wait_priming_stub;
411 * This is a flag that, if true, means that this query is
412 * for (re)fetching glue from a zone. Since the address should
413 * have been glue, query again to the servers that should have
414 * been returning it as glue.
415 * The delegation point must be set to the one that should *not*
416 * be used when creating the state. A higher one will be attempted.
421 * This flag detects that a completely empty nodata was received,
422 * already so that it is accepted later. */
423 int empty_nodata_found;
425 /** list of pending queries to authoritative servers. */
426 struct outbound_list outlist;
428 /** QNAME minimisation state, RFC9156 */
429 enum minimisation_state minimisation_state;
431 /** State for capsfail: QNAME minimisation state for comparisons. */
432 enum minimisation_state caps_minimisation_state;
435 * The query info that is sent upstream. Will be a subset of qchase
436 * when qname minimisation is enabled.
438 struct query_info qinfo_out;
441 * Count number of QNAME minimisation iterations. Used to limit number of
442 * outgoing queries when QNAME minimisation is enabled.
447 * Count number of time-outs. Used to prevent resolving failures when
448 * the QNAME minimisation QTYPE is blocked. Used to determine if
449 * capsforid fallback should be started.*/
452 /** True if the current response is from auth_zone */
453 int auth_zone_response;
454 /** True if the auth_zones should not be consulted for the query */
456 /** true if there have been scrubbing failures of reply packets */
458 /** true if there have been parse failures of reply packets */
460 /** a failure printout address for last received answer */
467 /** which fail_addr, 0 is nothing, 4 or 6 */
472 * List of prepend items
474 struct iter_prep_list {
476 struct iter_prep_list* next;
478 struct ub_packed_rrset_key* rrset;
482 * Get the iterator function block.
483 * @return: function block with function pointers to iterator methods.
485 struct module_func_block* iter_get_funcblock(void);
488 * Get iterator state as a string
489 * @param state: to convert
490 * @return constant string that is printable.
492 const char* iter_state_to_string(enum iter_state state);
495 * See if iterator state is a response state
496 * @param s: to inspect
497 * @return true if response state.
499 int iter_state_is_responsestate(enum iter_state s);
502 int iter_init(struct module_env* env, int id);
504 /** iterator deinit */
505 void iter_deinit(struct module_env* env, int id);
507 /** iterator operate on a query */
508 void iter_operate(struct module_qstate* qstate, enum module_ev event, int id,
509 struct outbound_entry* outbound);
512 * Return priming query results to interested super querystates.
514 * Sets the delegation point and delegation message (not nonRD queries).
515 * This is a callback from walk_supers.
517 * @param qstate: query state that finished.
518 * @param id: module id.
519 * @param super: the qstate to inform.
521 void iter_inform_super(struct module_qstate* qstate, int id,
522 struct module_qstate* super);
524 /** iterator cleanup query state */
525 void iter_clear(struct module_qstate* qstate, int id);
527 /** iterator alloc size routine */
528 size_t iter_get_mem(struct module_env* env, int id);
530 #endif /* ITERATOR_ITERATOR_H */