/contrib/bind9/lib/dns/include/dns/adb.h

  1/*
  2 * Copyright (C) 2004-2008, 2011, 2012  Internet Systems Consortium, Inc. ("ISC")
  3 * Copyright (C) 1999-2003  Internet Software Consortium.
  4 *
  5 * Permission to use, copy, modify, and/or distribute this software for any
  6 * purpose with or without fee is hereby granted, provided that the above
  7 * copyright notice and this permission notice appear in all copies.
  8 *
  9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
 10 * REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 11 * AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
 12 * INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
 13 * LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
 14 * OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 15 * PERFORMANCE OF THIS SOFTWARE.
 16 */
 17
 18/* $Id$ */
 19
 20#ifndef DNS_ADB_H
 21#define DNS_ADB_H 1
 22
 23/*****
 24 ***** Module Info
 25 *****/
 26
 27/*! \file dns/adb.h
 28 *\brief
 29 * DNS Address Database
 30 *
 31 * This module implements an address database (ADB) for mapping a name
 32 * to an isc_sockaddr_t. It also provides statistical information on
 33 * how good that address might be.
 34 *
 35 * A client will pass in a dns_name_t, and the ADB will walk through
 36 * the rdataset looking up addresses associated with the name.  If it
 37 * is found on the internal lists, a structure is filled in with the
 38 * address information and stats for found addresses.
 39 *
 40 * If the name cannot be found on the internal lists, a new entry will
 41 * be created for a name if all the information needed can be found
 42 * in the zone table or cache.  This new address will then be returned.
 43 *
 44 * If a request must be made to remote servers to satisfy a name lookup,
 45 * this module will start fetches to try to complete these addresses.  When
 46 * at least one more completes, an event is sent to the caller.  If none of
 47 * them resolve before the fetch times out, an event indicating this is
 48 * sent instead.
 49 *
 50 * Records are stored internally until a timer expires. The timer is the
 51 * smaller of the TTL or signature validity period.
 52 *
 53 * Lameness is stored per <qname,qtype> tuple, and this data hangs off each
 54 * address field.  When an address is marked lame for a given tuple the address
 55 * will not be returned to a caller.
 56 *
 57 *
 58 * MP:
 59 *
 60 *\li	The ADB takes care of all necessary locking.
 61 *
 62 *\li	Only the task which initiated the name lookup can cancel the lookup.
 63 *
 64 *
 65 * Security:
 66 *
 67 *\li	None, since all data stored is required to be pre-filtered.
 68 *	(Cache needs to be sane, fetches return bounds-checked and sanity-
 69 *       checked data, caller passes a good dns_name_t for the zone, etc)
 70 */
 71
 72/***
 73 *** Imports
 74 ***/
 75
 76#include <isc/lang.h>
 77#include <isc/magic.h>
 78#include <isc/mem.h>
 79#include <isc/sockaddr.h>
 80
 81#include <dns/types.h>
 82#include <dns/view.h>
 83
 84ISC_LANG_BEGINDECLS
 85
 86/***
 87 *** Magic number checks
 88 ***/
 89
 90#define DNS_ADBFIND_MAGIC	  ISC_MAGIC('a','d','b','H')
 91#define DNS_ADBFIND_VALID(x)	  ISC_MAGIC_VALID(x, DNS_ADBFIND_MAGIC)
 92#define DNS_ADBADDRINFO_MAGIC	  ISC_MAGIC('a','d','A','I')
 93#define DNS_ADBADDRINFO_VALID(x)  ISC_MAGIC_VALID(x, DNS_ADBADDRINFO_MAGIC)
 94
 95
 96/***
 97 *** TYPES
 98 ***/
 99
100typedef struct dns_adbname		dns_adbname_t;
101
102/*!
103 *\brief
104 * Represents a lookup for a single name.
105 *
106 * On return, the client can safely use "list", and can reorder the list.
107 * Items may not be _deleted_ from this list, however, or added to it
108 * other than by using the dns_adb_*() API.
109 */
110struct dns_adbfind {
111	/* Public */
112	unsigned int			magic;		/*%< RO: magic */
113	dns_adbaddrinfolist_t		list;		/*%< RO: list of addrs */
114	unsigned int			query_pending;	/*%< RO: partial list */
115	unsigned int			partial_result;	/*%< RO: addrs missing */
116	unsigned int			options;	/*%< RO: options */
117	isc_result_t			result_v4;	/*%< RO: v4 result */
118	isc_result_t			result_v6;	/*%< RO: v6 result */
119	ISC_LINK(dns_adbfind_t)		publink;	/*%< RW: client use */
120
121	/* Private */
122	isc_mutex_t			lock;		/* locks all below */
123	in_port_t			port;
124	int				name_bucket;
125	unsigned int			flags;
126	dns_adbname_t		       *adbname;
127	dns_adb_t		       *adb;
128	isc_event_t			event;
129	ISC_LINK(dns_adbfind_t)		plink;
130};
131
132/*
133 * _INET:
134 * _INET6:
135 *	return addresses of that type.
136 *
137 * _EMPTYEVENT:
138 *	Only schedule an event if no addresses are known.
139 *	Must set _WANTEVENT for this to be meaningful.
140 *
141 * _WANTEVENT:
142 *	An event is desired.  Check this bit in the returned find to see
143 *	if one will actually be generated.
144 *
145 * _AVOIDFETCHES:
146 *	If set, fetches will not be generated unless no addresses are
147 *	available in any of the address families requested.
148 *
149 * _STARTATZONE:
150 *	Fetches will start using the closest zone data or use the root servers.
151 *	This is useful for reestablishing glue that has expired.
152 *
153 * _GLUEOK:
154 * _HINTOK:
155 *	Glue or hints are ok.  These are used when matching names already
156 *	in the adb, and when dns databases are searched.
157 *
158 * _RETURNLAME:
159 *	Return lame servers in a find, so that all addresses are returned.
160 *
161 * _LAMEPRUNED:
162 *	At least one address was omitted from the list because it was lame.
163 *	This bit will NEVER be set if _RETURNLAME is set in the createfind().
164 */
165/*% Return addresses of type INET. */
166#define DNS_ADBFIND_INET		0x00000001
167/*% Return addresses of type INET6. */
168#define DNS_ADBFIND_INET6		0x00000002
169#define DNS_ADBFIND_ADDRESSMASK		0x00000003
170/*%
171 *      Only schedule an event if no addresses are known.
172 *      Must set _WANTEVENT for this to be meaningful.
173 */
174#define DNS_ADBFIND_EMPTYEVENT		0x00000004
175/*%
176 *	An event is desired.  Check this bit in the returned find to see
177 *	if one will actually be generated.
178 */
179#define DNS_ADBFIND_WANTEVENT		0x00000008
180/*%
181 *	If set, fetches will not be generated unless no addresses are
182 *	available in any of the address families requested.
183 */
184#define DNS_ADBFIND_AVOIDFETCHES	0x00000010
185/*%
186 *	Fetches will start using the closest zone data or use the root servers.
187 *	This is useful for reestablishing glue that has expired.
188 */
189#define DNS_ADBFIND_STARTATZONE		0x00000020
190/*%
191 *	Glue or hints are ok.  These are used when matching names already
192 *	in the adb, and when dns databases are searched.
193 */
194#define DNS_ADBFIND_GLUEOK		0x00000040
195/*%
196 *	Glue or hints are ok.  These are used when matching names already
197 *	in the adb, and when dns databases are searched.
198 */
199#define DNS_ADBFIND_HINTOK		0x00000080
200/*%
201 *	Return lame servers in a find, so that all addresses are returned.
202 */
203#define DNS_ADBFIND_RETURNLAME		0x00000100
204/*%
205 *      Only schedule an event if no addresses are known.
206 *      Must set _WANTEVENT for this to be meaningful.
207 */
208#define DNS_ADBFIND_LAMEPRUNED		0x00000200
209
210/*%
211 * The answers to queries come back as a list of these.
212 */
213struct dns_adbaddrinfo {
214	unsigned int			magic;		/*%< private */
215
216	isc_sockaddr_t			sockaddr;	/*%< [rw] */
217	unsigned int			srtt;		/*%< [rw] microseconds */
218	unsigned int			flags;		/*%< [rw] */
219	dns_adbentry_t		       *entry;		/*%< private */
220	ISC_LINK(dns_adbaddrinfo_t)	publink;
221};
222
223/*!<
224 * The event sent to the caller task is just a plain old isc_event_t.  It
225 * contains no data other than a simple status, passed in the "type" field
226 * to indicate that another address resolved, or all partially resolved
227 * addresses have failed to resolve.
228 *
229 * "sender" is the dns_adbfind_t used to issue this query.
230 *
231 * This is simply a standard event, with the "type" set to:
232 *
233 *\li	#DNS_EVENT_ADBMOREADDRESSES   -- another address resolved.
234 *\li	#DNS_EVENT_ADBNOMOREADDRESSES -- all pending addresses failed,
235 *					were canceled, or otherwise will
236 *					not be usable.
237 *\li	#DNS_EVENT_ADBCANCELED	     -- The request was canceled by a
238 *					3rd party.
239 *\li	#DNS_EVENT_ADBNAMEDELETED     -- The name was deleted, so this request
240 *					was canceled.
241 *
242 * In each of these cases, the addresses returned by the initial call
243 * to dns_adb_createfind() can still be used until they are no longer needed.
244 */
245
246/****
247 **** FUNCTIONS
248 ****/
249
250
251isc_result_t
252dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *tmgr,
253	       isc_taskmgr_t *taskmgr, dns_adb_t **newadb);
254/*%<
255 * Create a new ADB.
256 *
257 * Notes:
258 *
259 *\li	Generally, applications should not create an ADB directly, but
260 *	should instead call dns_view_createresolver().
261 *
262 * Requires:
263 *
264 *\li	'mem' must be a valid memory context.
265 *
266 *\li	'view' be a pointer to a valid view.
267 *
268 *\li	'tmgr' be a pointer to a valid timer manager.
269 *
270 *\li	'taskmgr' be a pointer to a valid task manager.
271 *
272 *\li	'newadb' != NULL && '*newadb' == NULL.
273 *
274 * Returns:
275 *
276 *\li	#ISC_R_SUCCESS	after happiness.
277 *\li	#ISC_R_NOMEMORY	after resource allocation failure.
278 */
279
280void
281dns_adb_attach(dns_adb_t *adb, dns_adb_t **adbp);
282/*%
283 * Attach to an 'adb' to 'adbp'.
284 *
285 * Requires:
286 *\li	'adb' to be a valid dns_adb_t, created via dns_adb_create().
287 *\li	'adbp' to be a valid pointer to a *dns_adb_t which is initialized
288 *	to NULL.
289 */
290
291void
292dns_adb_detach(dns_adb_t **adb);
293/*%
294 * Delete the ADB. Sets *ADB to NULL. Cancels any outstanding requests.
295 *
296 * Requires:
297 *
298 *\li	'adb' be non-NULL and '*adb' be a valid dns_adb_t, created via
299 *	dns_adb_create().
300 */
301
302void
303dns_adb_whenshutdown(dns_adb_t *adb, isc_task_t *task, isc_event_t **eventp);
304/*%
305 * Send '*eventp' to 'task' when 'adb' has shutdown.
306 *
307 * Requires:
308 *
309 *\li	'*adb' is a valid dns_adb_t.
310 *
311 *\li	eventp != NULL && *eventp is a valid event.
312 *
313 * Ensures:
314 *
315 *\li	*eventp == NULL
316 *
317 *\li	The event's sender field is set to the value of adb when the event
318 *	is sent.
319 */
320
321void
322dns_adb_shutdown(dns_adb_t *adb);
323/*%<
324 * Shutdown 'adb'.
325 *
326 * Requires:
327 *
328 * \li	'*adb' is a valid dns_adb_t.
329 */
330
331isc_result_t
332dns_adb_createfind(dns_adb_t *adb, isc_task_t *task, isc_taskaction_t action,
333		   void *arg, dns_name_t *name, dns_name_t *qname,
334		   dns_rdatatype_t qtype, unsigned int options,
335		   isc_stdtime_t now, dns_name_t *target,
336		   in_port_t port, dns_adbfind_t **find);
337/*%<
338 * Main interface for clients. The adb will look up the name given in
339 * "name" and will build up a list of found addresses, and perhaps start
340 * internal fetches to resolve names that are unknown currently.
341 *
342 * If other addresses resolve after this call completes, an event will
343 * be sent to the <task, taskaction, arg> with the sender of that event
344 * set to a pointer to the dns_adbfind_t returned by this function.
345 *
346 * If no events will be generated, the *find->result_v4 and/or result_v6
347 * members may be examined for address lookup status.  The usual #ISC_R_SUCCESS,
348 * #ISC_R_FAILURE, #DNS_R_NXDOMAIN, and #DNS_R_NXRRSET are returned, along with
349 * #ISC_R_NOTFOUND meaning the ADB has not _yet_ found the values.  In this
350 * latter case, retrying may produce more addresses.
351 *
352 * If events will be returned, the result_v[46] members are only valid
353 * when that event is actually returned.
354 *
355 * The list of addresses returned is unordered.  The caller must impose
356 * any ordering required.  The list will not contain "known bad" addresses,
357 * however.  For instance, it will not return hosts that are known to be
358 * lame for the zone in question.
359 *
360 * The caller cannot (directly) modify the contents of the address list's
361 * fields other than the "link" field.  All values can be read at any
362 * time, however.
363 *
364 * The "now" parameter is used only for determining which entries that
365 * have a specific time to live or expire time should be removed from
366 * the running database.  If specified as zero, the current time will
367 * be retrieved and used.
368 *
369 * If 'target' is not NULL and 'name' is an alias (i.e. the name is
370 * CNAME'd or DNAME'd to another name), then 'target' will be updated with
371 * the domain name that 'name' is aliased to.
372 *
373 * All addresses returned will have the sockaddr's port set to 'port.'
374 * The caller may change them directly in the dns_adbaddrinfo_t since
375 * they are copies of the internal address only.
376 *
377 * XXXMLG  Document options, especially the flags which control how
378 *         events are sent.
379 *
380 * Requires:
381 *
382 *\li	*adb be a valid isc_adb_t object.
383 *
384 *\li	If events are to be sent, *task be a valid task,
385 *	and isc_taskaction_t != NULL.
386 *
387 *\li	*name is a valid dns_name_t.
388 *
389 *\li	qname != NULL and *qname be a valid dns_name_t.
390 *
391 *\li	target == NULL or target is a valid name with a buffer.
392 *
393 *\li	find != NULL && *find == NULL.
394 *
395 * Returns:
396 *
397 *\li	#ISC_R_SUCCESS	Addresses might have been returned, and events will be
398 *			delivered for unresolved addresses.
399 *\li	#ISC_R_NOMORE	Addresses might have been returned, but no events
400 *			will ever be posted for this context.  This is only
401 *			returned if task != NULL.
402 *\li	#ISC_R_NOMEMORY	insufficient resources
403 *\li	#DNS_R_ALIAS	'name' is an alias for another name.
404 *
405 * Calls, and returns error codes from:
406 *
407 *\li	isc_stdtime_get()
408 *
409 * Notes:
410 *
411 *\li	No internal reference to "name" exists after this function
412 *	returns.
413 */
414
415void
416dns_adb_cancelfind(dns_adbfind_t *find);
417/*%<
418 * Cancels the find, and sends the event off to the caller.
419 *
420 * It is an error to call dns_adb_cancelfind() on a find where
421 * no event is wanted, or will ever be sent.
422 *
423 * Note:
424 *
425 *\li	It is possible that the real completion event was posted just
426 *	before the dns_adb_cancelfind() call was made.  In this case,
427 *	dns_adb_cancelfind() will do nothing.  The event callback needs
428 *	to be prepared to find this situation (i.e. result is valid but
429 *	the caller expects it to be canceled).
430 *
431 * Requires:
432 *
433 *\li	'find' be a valid dns_adbfind_t pointer.
434 *
435 *\li	events would have been posted to the task.  This can be checked
436 *	with (find->options & DNS_ADBFIND_WANTEVENT).
437 *
438 * Ensures:
439 *
440 *\li	The event was posted to the task.
441 */
442
443void
444dns_adb_destroyfind(dns_adbfind_t **find);
445/*%<
446 * Destroys the find reference.
447 *
448 * Note:
449 *
450 *\li	This can only be called after the event was delivered for a
451 *	find.  Additionally, the event MUST have been freed via
452 *	isc_event_free() BEFORE this function is called.
453 *
454 * Requires:
455 *
456 *\li	'find' != NULL and *find be valid dns_adbfind_t pointer.
457 *
458 * Ensures:
459 *
460 *\li	No "address found" events will be posted to the originating task
461 *	after this function returns.
462 */
463
464void
465dns_adb_dump(dns_adb_t *adb, FILE *f);
466/*%<
467 * This function is only used for debugging.  It will dump as much of the
468 * state of the running system as possible.
469 *
470 * Requires:
471 *
472 *\li	adb be valid.
473 *
474 *\li	f != NULL, and is a file open for writing.
475 */
476
477void
478dns_adb_dumpfind(dns_adbfind_t *find, FILE *f);
479/*%<
480 * This function is only used for debugging.  Dump the data associated
481 * with a find.
482 *
483 * Requires:
484 *
485 *\li	find is valid.
486 *
487 * \li	f != NULL, and is a file open for writing.
488 */
489
490isc_result_t
491dns_adb_marklame(dns_adb_t *adb, dns_adbaddrinfo_t *addr, dns_name_t *qname,
492		 dns_rdatatype_t type, isc_stdtime_t expire_time);
493/*%<
494 * Mark the given address as lame for the <qname,qtype>.  expire_time should
495 * be set to the time when the entry should expire.  That is, if it is to
496 * expire 10 minutes in the future, it should set it to (now + 10 * 60).
497 *
498 * Requires:
499 *
500 *\li	adb be valid.
501 *
502 *\li	addr be valid.
503 *
504 *\li	qname be the qname used in the dns_adb_createfind() call.
505 *
506 * Returns:
507 *
508 *\li	#ISC_R_SUCCESS		-- all is well.
509 *\li	#ISC_R_NOMEMORY		-- could not mark address as lame.
510 */
511
512/*
513 * A reasonable default for RTT adjustments
514 */
515#define DNS_ADB_RTTADJDEFAULT		7	/*%< default scale */
516#define DNS_ADB_RTTADJREPLACE		0	/*%< replace with our rtt */
517#define DNS_ADB_RTTADJAGE		10	/*%< age this rtt */
518
519void
520dns_adb_adjustsrtt(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
521		   unsigned int rtt, unsigned int factor);
522/*%<
523 * Mix the round trip time into the existing smoothed rtt.
524
525 * The formula used
526 * (where srtt is the existing rtt value, and rtt and factor are arguments to
527 * this function):
528 *
529 *\code
530 *	new_srtt = (old_srtt / 10 * factor) + (rtt / 10 * (10 - factor));
531 *\endcode
532 *
533 * XXXRTH  Do we want to publish the formula?  What if we want to change how
534 *         this works later on?  Recommend/require that the units are
535 *	   microseconds?
536 *
537 * Requires:
538 *
539 *\li	adb be valid.
540 *
541 *\li	addr be valid.
542 *
543 *\li	0 <= factor <= 10
544 *
545 * Note:
546 *
547 *\li	The srtt in addr will be updated to reflect the new global
548 *	srtt value.  This may include changes made by others.
549 */
550
551void
552dns_adb_changeflags(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
553		    unsigned int bits, unsigned int mask);
554/*%
555 * Change Flags.
556 *
557 * Set the flags as given by:
558 *
559 *\li	newflags = (oldflags & ~mask) | (bits & mask);
560 *
561 * Requires:
562 *
563 *\li	adb be valid.
564 *
565 *\li	addr be valid.
566 */
567
568isc_result_t
569dns_adb_findaddrinfo(dns_adb_t *adb, isc_sockaddr_t *sa,
570		     dns_adbaddrinfo_t **addrp, isc_stdtime_t now);
571/*%<
572 * Return a dns_adbaddrinfo_t that is associated with address 'sa'.
573 *
574 * Requires:
575 *
576 *\li	adb is valid.
577 *
578 *\li	sa is valid.
579 *
580 *\li	addrp != NULL && *addrp == NULL
581 *
582 * Returns:
583 *\li	#ISC_R_SUCCESS
584 *\li	#ISC_R_NOMEMORY
585 *\li	#ISC_R_SHUTTINGDOWN
586 */
587
588void
589dns_adb_freeaddrinfo(dns_adb_t *adb, dns_adbaddrinfo_t **addrp);
590/*%<
591 * Free a dns_adbaddrinfo_t allocated by dns_adb_findaddrinfo().
592 *
593 * Requires:
594 *
595 *\li	adb is valid.
596 *
597 *\li	*addrp is a valid dns_adbaddrinfo_t *.
598 */
599
600void
601dns_adb_flush(dns_adb_t *adb);
602/*%<
603 * Flushes all cached data from the adb.
604 *
605 * Requires:
606 *\li 	adb is valid.
607 */
608
609void
610dns_adb_setadbsize(dns_adb_t *adb, isc_uint32_t size);
611/*%<
612 * Set a target memory size.  If memory usage exceeds the target
613 * size entries will be removed before they would have expired on
614 * a random basis.
615 *
616 * If 'size' is 0 then memory usage is unlimited.
617 *
618 * Requires:
619 *\li	'adb' is valid.
620 */
621
622void
623dns_adb_flushname(dns_adb_t *adb, dns_name_t *name);
624/*%<
625 * Flush 'name' from the adb cache.
626 *
627 * Requires:
628 *\li	'adb' is valid.
629 *\li	'name' is valid.
630 */
631
632ISC_LANG_ENDDECLS
633
634#endif /* DNS_ADB_H */