2 * util/module.h - DNS handling module interface
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39 * This file contains the interface for DNS handling modules.
41 * The module interface uses the DNS modules as state machines. The
42 * state machines are activated in sequence to operate on queries. Once
43 * they are done, the reply is passed back. In the usual setup the mesh
44 * is the caller of the state machines and once things are done sends replies
45 * and invokes result callbacks.
47 * The module provides a number of functions, listed in the module_func_block.
48 * The module is inited and destroyed and memory usage queries, for the
49 * module as a whole, for entire-module state (such as a cache). And per-query
50 * functions are called, operate to move the state machine and cleanup of
51 * the per-query state.
53 * Most per-query state should simply be allocated in the query region.
54 * This is destroyed at the end of the query.
56 * The module environment contains services and information and caches
57 * shared by the modules and the rest of the system. It also contains
58 * function pointers for module-specific tasks (like sending queries).
60 * *** Example module calls for a normal query
62 * In this example, the query does not need recursion, all the other data
63 * can be found in the cache. This makes the example shorter.
65 * At the start of the program the iterator module is initialised.
66 * The iterator module sets up its global state, such as donotquery lists
67 * and private address trees.
69 * A query comes in, and a mesh entry is created for it. The mesh
70 * starts the resolution process. The validator module is the first
71 * in the list of modules, and it is started on this new query. The
72 * operate() function is called. The validator decides it needs not do
73 * anything yet until there is a result and returns wait_module, that
74 * causes the next module in the list to be started.
76 * The next module is the iterator. It is started on the passed query and
77 * decides to perform a lookup. For this simple example, the delegation
78 * point information is available, and all the iterator wants to do is
79 * send a UDP query. The iterator uses env.send_query() to send the
80 * query. Then the iterator suspends (returns from the operate call).
82 * When the UDP reply comes back (and on errors and timeouts), the
83 * operate function is called for the query, on the iterator module,
84 * with the event that there is a reply. The iterator decides that this
85 * is enough, the work is done. It returns the value finished from the
86 * operate call, which causes the previous module to be started.
88 * The previous module, the validator module, is started with the event
89 * that the iterator module is done. The validator decides to validate
90 * the query. Once it is done (which could take recursive lookups, but
91 * in this example no recursive lookups are needed), it returns from the
92 * operate function with finished.
94 * There is no previous module from the validator module, and the mesh
95 * takes this to mean that the query is finally done. The mesh invokes
96 * callbacks and sends packets to queriers.
98 * If other modules had been waiting (recursively) on the answer to this
99 * query, then the mesh will tell them about it. It calls the inform_super
100 * routine on all the waiting modules, and once that is done it calls all of
101 * them with the operate() call. During inform_super the query that is done
102 * still exists and information can be copied from it (but the module should
103 * not really re-entry codepoints and services). During the operate call
104 * the modules can use stored state to continue operation with the results.
105 * (network buffers are used to contain the answer packet during the
106 * inform_super phase, but after that the network buffers will be cleared
107 * of their contents so that other tasks can be performed).
109 * *** Example module calls for recursion
111 * A module is called in operate, and it decides that it wants to perform
112 * recursion. That is, it wants the full state-machine-list to operate on
113 * a different query. It calls env.attach_sub() to create a new query state.
114 * The routine returns the newly created state, and potentially the module
115 * can edit the module-states for the newly created query (i.e. pass along
116 * some information, like delegation points). The module then suspends,
117 * returns from the operate routine.
119 * The mesh meanwhile will have the newly created query (or queries) on
120 * a waiting list, and will call operate() on this query (or queries).
121 * It starts again at the start of the module list for them. The query
122 * (or queries) continue to operate their state machines, until they are
123 * done. When they are done the mesh calls inform_super on the module that
124 * wanted the recursion. After that the mesh calls operate() on the module
125 * that wanted to do the recursion, and during this phase the module could,
126 * for example, decide to create more recursions.
128 * If the module decides it no longer wants the recursive information
129 * it can call detach_subs. Those queries will still run to completion,
130 * potentially filling the cache with information. Inform_super is not
133 * The iterator module will fetch items from the cache, so a recursion
134 * attempt may complete very quickly if the item is in cache. The calling
135 * module has to wait for completion or eventual timeout. A recursive query
136 * that times out returns a servfail rcode (servfail is also returned for
137 * other errors during the lookup).
139 * Results are passed in the qstate, the rcode member is used to pass
140 * errors without requiring memory allocation, so that the code can continue
141 * in out-of-memory conditions. If the rcode member is 0 (NOERROR) then
142 * the dns_msg entry contains a filled out message. This message may
143 * also contain an rcode that is nonzero, but in this case additional
144 * information (query, additional) can be passed along.
146 * The rcode and dns_msg are used to pass the result from the the rightmost
147 * module towards the leftmost modules and then towards the user.
149 * If you want to avoid recursion-cycles where queries need other queries
150 * that need the first one, use detect_cycle() to see if that will happen.
154 #ifndef UTIL_MODULE_H
155 #define UTIL_MODULE_H
156 #include "util/storage/lruhash.h"
157 #include "util/data/msgreply.h"
158 #include "util/data/msgparse.h"
169 struct module_qstate;
174 struct val_neg_cache;
175 struct iter_forwards;
178 /** Maximum number of modules in operation */
182 * Module environment.
183 * Services and data provided to the module.
187 /** config file with config options */
188 struct config_file* cfg;
189 /** shared message cache */
190 struct slabhash* msg_cache;
191 /** shared rrset cache */
192 struct rrset_cache* rrset_cache;
193 /** shared infrastructure cache (edns, lameness) */
194 struct infra_cache* infra_cache;
195 /** shared key cache */
196 struct key_cache* key_cache;
198 /* --- services --- */
200 * Send serviced DNS query to server. UDP/TCP and EDNS is handled.
201 * operate() should return with wait_reply. Later on a callback
202 * will cause operate() to be called with event timeout or reply.
203 * The time until a timeout is calculated from roundtrip timing,
204 * several UDP retries are attempted.
205 * @param qname: query name. (host order)
206 * @param qnamelen: length in bytes of qname, including trailing 0.
207 * @param qtype: query type. (host order)
208 * @param qclass: query class. (host order)
209 * @param flags: host order flags word, with opcode and CD bit.
210 * @param dnssec: if set, EDNS record will have bits set.
211 * If EDNS_DO bit is set, DO bit is set in EDNS records.
212 * If BIT_CD is set, CD bit is set in queries with EDNS records.
213 * @param want_dnssec: if set, the validator wants DNSSEC. Without
214 * EDNS, the answer is likely to be useless for this domain.
215 * @param addr: where to.
216 * @param addrlen: length of addr.
217 * @param zone: delegation point name.
218 * @param zonelen: length of zone name.
219 * @param q: wich query state to reactivate upon return.
220 * @return: false on failure (memory or socket related). no query was
221 * sent. Or returns an outbound entry with qsent and qstate set.
222 * This outbound_entry will be used on later module invocations
223 * that involve this query (timeout, error or reply).
225 struct outbound_entry* (*send_query)(uint8_t* qname, size_t qnamelen,
226 uint16_t qtype, uint16_t qclass, uint16_t flags, int dnssec,
227 int want_dnssec, struct sockaddr_storage* addr,
228 socklen_t addrlen, uint8_t* zone, size_t zonelen,
229 struct module_qstate* q);
233 * Remove all sub-query references from this query state.
234 * Keeps super-references of those sub-queries correct.
235 * Updates stat items in mesh_area structure.
236 * @param qstate: used to find mesh state.
238 void (*detach_subs)(struct module_qstate* qstate);
242 * Creates it if it does not exist already.
243 * Keeps sub and super references correct.
244 * Updates stat items in mesh_area structure.
245 * Pass if it is priming query or not.
247 * o if error (malloc) happened.
248 * o need to initialise the new state (module init; it is a new state).
249 * so that the next run of the query with this module is successful.
250 * o no init needed, attachment successful.
252 * @param qstate: the state to find mesh state, and that wants to
253 * receive the results from the new subquery.
254 * @param qinfo: what to query for (copied).
255 * @param qflags: what flags to use (RD, CD flag or not).
256 * @param prime: if it is a (stub) priming query.
257 * @param newq: If the new subquery needs initialisation, it is
258 * returned, otherwise NULL is returned.
259 * @return: false on error, true if success (and init may be needed).
261 int (*attach_sub)(struct module_qstate* qstate,
262 struct query_info* qinfo, uint16_t qflags, int prime,
263 struct module_qstate** newq);
266 * Kill newly attached sub. If attach_sub returns newq for
267 * initialisation, but that fails, then this routine will cleanup and
268 * delete the fresly created sub.
269 * @param newq: the new subquery that is no longer needed.
272 void (*kill_sub)(struct module_qstate* newq);
275 * Detect if adding a dependency for qstate on name,type,class will
276 * create a dependency cycle.
277 * @param qstate: given mesh querystate.
278 * @param qinfo: query info for dependency.
279 * @param flags: query flags of dependency, RD/CD flags.
280 * @param prime: if dependency is a priming query or not.
281 * @return true if the name,type,class exists and the given
282 * qstate mesh exists as a dependency of that name. Thus
283 * if qstate becomes dependent on name,type,class then a
286 int (*detect_cycle)(struct module_qstate* qstate,
287 struct query_info* qinfo, uint16_t flags, int prime);
289 /** region for temporary usage. May be cleared after operate() call. */
290 struct regional* scratch;
291 /** buffer for temporary usage. May be cleared after operate() call. */
292 struct sldns_buffer* scratch_buffer;
293 /** internal data for daemon - worker thread. */
294 struct worker* worker;
295 /** mesh area with query state dependencies */
296 struct mesh_area* mesh;
297 /** allocation service */
298 struct alloc_cache* alloc;
299 /** random table to generate random numbers */
300 struct ub_randstate* rnd;
301 /** time in seconds, converted to integer */
303 /** time in microseconds. Relatively recent. */
304 struct timeval* now_tv;
305 /** is validation required for messages, controls client-facing
306 * validation status (AD bits) and servfails */
307 int need_to_validate;
308 /** trusted key storage; these are the configured keys, if not NULL,
309 * otherwise configured by validator. These are the trust anchors,
310 * and are not primed and ready for validation, but on the bright
311 * side, they are read only memory, thus no locks and fast. */
312 struct val_anchors* anchors;
313 /** negative cache, configured by the validator. if not NULL,
314 * contains NSEC record lookup trees. */
315 struct val_neg_cache* neg_cache;
316 /** the 5011-probe timer (if any) */
317 struct comm_timer* probe_timer;
318 /** Mapping of forwarding zones to targets.
319 * iterator forwarder information. per-thread, created by worker */
320 struct iter_forwards* fwds;
322 * iterator forwarder information. per-thread, created by worker.
323 * The hints -- these aren't stored in the cache because they don't
324 * expire. The hints are always used to "prime" the cache. Note
325 * that both root hints and stub zone "hints" are stored in this
328 struct iter_hints* hints;
329 /** module specific data. indexed by module id. */
330 void* modinfo[MAX_MODULE];
334 * External visible states of the module state machine
335 * Modules may also have an internal state.
336 * Modules are supposed to run to completion or until blocked.
338 enum module_ext_state {
339 /** initial state - new query */
340 module_state_initial = 0,
341 /** waiting for reply to outgoing network query */
343 /** module is waiting for another module */
345 /** module is waiting for another module; that other is restarted */
347 /** module is waiting for sub-query */
348 module_wait_subquery,
349 /** module could not finish the query */
351 /** module is finished with query */
356 * Events that happen to modules, that start or wakeup modules.
360 module_event_new = 0,
361 /** query passed by other module */
363 /** reply inbound from server */
365 /** no reply, timeout or other error */
366 module_event_noreply,
367 /** reply is there, but capitalisation check failed */
368 module_event_capsfail,
369 /** next module is done, and its reply is awaiting you */
370 module_event_moddone,
376 * Linked list of sockaddrs
377 * May be allocated such that only 'len' bytes of addr exist for the structure.
381 struct sock_list* next;
382 /** length of addr */
385 struct sockaddr_storage addr;
389 * Module state, per query.
391 struct module_qstate {
392 /** which query is being answered: name, type, class */
393 struct query_info qinfo;
394 /** flags uint16 from query */
395 uint16_t query_flags;
396 /** if this is a (stub or root) priming query (with hints) */
399 /** comm_reply contains server replies */
400 struct comm_reply* reply;
401 /** the reply message, with message for client and calling module */
402 struct dns_msg* return_msg;
403 /** the rcode, in case of error, instead of a reply message */
405 /** origin of the reply (can be NULL from cache, list for cnames) */
406 struct sock_list* reply_origin;
407 /** IP blacklist for queries */
408 struct sock_list* blacklist;
409 /** region for this query. Cleared when query process finishes. */
410 struct regional* region;
411 /** failure reason information if val-log-level is high */
412 struct config_strlist* errinf;
414 /** which module is executing */
417 enum module_ext_state ext_state[MAX_MODULE];
418 /** module specific data for query. indexed by module id. */
419 void* minfo[MAX_MODULE];
420 /** environment for this query */
421 struct module_env* env;
422 /** mesh related information for this query */
423 struct mesh_state* mesh_info;
424 /** how many seconds before expiry is this prefetched (0 if not) */
425 time_t prefetch_leeway;
429 * Module functionality block
431 struct module_func_block {
432 /** text string name of module */
436 * init the module. Called once for the global state.
437 * This is the place to apply settings from the config file.
438 * @param env: module environment.
439 * @param id: module id number.
442 int (*init)(struct module_env* env, int id);
445 * de-init, delete, the module. Called once for the global state.
446 * @param env: module environment.
447 * @param id: module id number.
449 void (*deinit)(struct module_env* env, int id);
452 * accept a new query, or work further on existing query.
453 * Changes the qstate->ext_state to be correct on exit.
454 * @param ev: event that causes the module state machine to
456 * @param qstate: the query state.
457 * Note that this method is not allowed to change the
458 * query state 'identity', that is query info, qflags,
459 * and priming status.
460 * Attach a subquery to get results to a different query.
461 * @param id: module id number that operate() is called on.
462 * @param outbound: if not NULL this event is due to the reply/timeout
463 * or error on this outbound query.
464 * @return: if at exit the ext_state is:
465 * o wait_module: next module is started. (with pass event).
466 * o error or finished: previous module is resumed.
467 * o otherwise it waits until that event happens (assumes
468 * the service routine to make subrequest or send message
471 void (*operate)(struct module_qstate* qstate, enum module_ev event,
472 int id, struct outbound_entry* outbound);
475 * inform super querystate about the results from this subquerystate.
476 * Is called when the querystate is finished. The method invoked is
477 * the one from the current module active in the super querystate.
478 * @param qstate: the query state that is finished.
479 * Examine return_rcode and return_reply in the qstate.
480 * @param id: module id for this module.
481 * This coincides with the current module for the super qstate.
482 * @param super: the super querystate that needs to be informed.
484 void (*inform_super)(struct module_qstate* qstate, int id,
485 struct module_qstate* super);
488 * clear module specific data
490 void (*clear)(struct module_qstate* qstate, int id);
493 * How much memory is the module specific data using.
494 * @param env: module environment.
495 * @param id: the module id.
496 * @return the number of bytes that are alloced.
498 size_t (*get_mem)(struct module_env* env, int id);
502 * Debug utility: module external qstate to string
503 * @param s: the state value.
504 * @return descriptive string.
506 const char* strextstate(enum module_ext_state s);
509 * Debug utility: module event to string
510 * @param e: the module event value.
511 * @return descriptive string.
513 const char* strmodulevent(enum module_ev e);
515 #endif /* UTIL_MODULE_H */