2 * Copyright (C) 2004-2008 Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (C) 1999-2003 Internet Software Consortium.
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.
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
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15 * PERFORMANCE OF THIS SOFTWARE.
18 /* $Id: adb.h,v 1.85 2008/04/03 06:09:04 tbox Exp $ */
29 * DNS Address Database
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.
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.
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.
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
50 * Records are stored internally until a timer expires. The timer is the
51 * smaller of the TTL or signature validity period.
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.
60 *\li The ADB takes care of all necessary locking.
62 *\li Only the task which initiated the name lookup can cancel the lookup.
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)
77 #include <isc/magic.h>
79 #include <isc/sockaddr.h>
81 #include <dns/types.h>
87 *** Magic number checks
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)
100 typedef struct dns_adbname dns_adbname_t;
104 * Represents a lookup for a single name.
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.
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 */
122 isc_mutex_t lock; /* locks all below */
126 dns_adbname_t *adbname;
129 ISC_LINK(dns_adbfind_t) plink;
135 * return addresses of that type.
138 * Only schedule an event if no addresses are known.
139 * Must set _WANTEVENT for this to be meaningful.
142 * An event is desired. Check this bit in the returned find to see
143 * if one will actually be generated.
146 * If set, fetches will not be generated unless no addresses are
147 * available in any of the address families requested.
150 * Fetches will start using the closest zone data or use the root servers.
151 * This is useful for reestablishing glue that has expired.
155 * Glue or hints are ok. These are used when matching names already
156 * in the adb, and when dns databases are searched.
159 * Return lame servers in a find, so that all addresses are returned.
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().
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
171 * Only schedule an event if no addresses are known.
172 * Must set _WANTEVENT for this to be meaningful.
174 #define DNS_ADBFIND_EMPTYEVENT 0x00000004
176 * An event is desired. Check this bit in the returned find to see
177 * if one will actually be generated.
179 #define DNS_ADBFIND_WANTEVENT 0x00000008
181 * If set, fetches will not be generated unless no addresses are
182 * available in any of the address families requested.
184 #define DNS_ADBFIND_AVOIDFETCHES 0x00000010
186 * Fetches will start using the closest zone data or use the root servers.
187 * This is useful for reestablishing glue that has expired.
189 #define DNS_ADBFIND_STARTATZONE 0x00000020
191 * Glue or hints are ok. These are used when matching names already
192 * in the adb, and when dns databases are searched.
194 #define DNS_ADBFIND_GLUEOK 0x00000040
196 * Glue or hints are ok. These are used when matching names already
197 * in the adb, and when dns databases are searched.
199 #define DNS_ADBFIND_HINTOK 0x00000080
201 * Return lame servers in a find, so that all addresses are returned.
203 #define DNS_ADBFIND_RETURNLAME 0x00000100
205 * Only schedule an event if no addresses are known.
206 * Must set _WANTEVENT for this to be meaningful.
208 #define DNS_ADBFIND_LAMEPRUNED 0x00000200
211 * The answers to queries come back as a list of these.
213 struct dns_adbaddrinfo {
214 unsigned int magic; /*%< private */
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;
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.
229 * "sender" is the dns_adbfind_t used to issue this query.
231 * This is simply a standard event, with the "type" set to:
233 *\li #DNS_EVENT_ADBMOREADDRESSES -- another address resolved.
234 *\li #DNS_EVENT_ADBNOMOREADDRESSES -- all pending addresses failed,
235 * were canceled, or otherwise will
237 *\li #DNS_EVENT_ADBCANCELED -- The request was canceled by a
239 *\li #DNS_EVENT_ADBNAMEDELETED -- The name was deleted, so this request
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.
252 dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *tmgr,
253 isc_taskmgr_t *taskmgr, dns_adb_t **newadb);
259 *\li Generally, applications should not create an ADB directly, but
260 * should instead call dns_view_createresolver().
264 *\li 'mem' must be a valid memory context.
266 *\li 'view' be a pointer to a valid view.
268 *\li 'tmgr' be a pointer to a valid timer manager.
270 *\li 'taskmgr' be a pointer to a valid task manager.
272 *\li 'newadb' != NULL && '*newadb' == NULL.
276 *\li #ISC_R_SUCCESS after happiness.
277 *\li #ISC_R_NOMEMORY after resource allocation failure.
281 dns_adb_attach(dns_adb_t *adb, dns_adb_t **adbp);
283 * Attach to an 'adb' to 'adbp'.
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
292 dns_adb_detach(dns_adb_t **adb);
294 * Delete the ADB. Sets *ADB to NULL. Cancels any outstanding requests.
298 *\li 'adb' be non-NULL and '*adb' be a valid dns_adb_t, created via
303 dns_adb_whenshutdown(dns_adb_t *adb, isc_task_t *task, isc_event_t **eventp);
305 * Send '*eventp' to 'task' when 'adb' has shutdown.
309 *\li '*adb' is a valid dns_adb_t.
311 *\li eventp != NULL && *eventp is a valid event.
317 *\li The event's sender field is set to the value of adb when the event
322 dns_adb_shutdown(dns_adb_t *adb);
328 * \li '*adb' is a valid dns_adb_t.
332 dns_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);
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.
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.
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.
352 * If events will be returned, the result_v[46] members are only valid
353 * when that event is actually returned.
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.
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
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.
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.
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.
377 * XXXMLG Document options, especially the flags which control how
382 *\li *adb be a valid isc_adb_t object.
384 *\li If events are to be sent, *task be a valid task,
385 * and isc_taskaction_t != NULL.
387 *\li *name is a valid dns_name_t.
389 *\li qname != NULL and *qname be a valid dns_name_t.
391 *\li target == NULL or target is a valid name with a buffer.
393 *\li find != NULL && *find == NULL.
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.
405 * Calls, and returns error codes from:
407 *\li isc_stdtime_get()
411 *\li No internal reference to "name" exists after this function
416 dns_adb_cancelfind(dns_adbfind_t *find);
418 * Cancels the find, and sends the event off to the caller.
420 * It is an error to call dns_adb_cancelfind() on a find where
421 * no event is wanted, or will ever be sent.
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).
433 *\li 'find' be a valid dns_adbfind_t pointer.
435 *\li events would have been posted to the task. This can be checked
436 * with (find->options & DNS_ADBFIND_WANTEVENT).
440 *\li The event was posted to the task.
444 dns_adb_destroyfind(dns_adbfind_t **find);
446 * Destroys the find reference.
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.
456 *\li 'find' != NULL and *find be valid dns_adbfind_t pointer.
460 *\li No "address found" events will be posted to the originating task
461 * after this function returns.
465 dns_adb_dump(dns_adb_t *adb, FILE *f);
467 * This function is only used for debugging. It will dump as much of the
468 * state of the running system as possible.
474 *\li f != NULL, and is a file open for writing.
478 dns_adb_dumpfind(dns_adbfind_t *find, FILE *f);
480 * This function is only used for debugging. Dump the data associated
487 * \li f != NULL, and is a file open for writing.
491 dns_adb_marklame(dns_adb_t *adb, dns_adbaddrinfo_t *addr, dns_name_t *qname,
492 dns_rdatatype_t type, isc_stdtime_t expire_time);
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).
504 *\li qname be the qname used in the dns_adb_createfind() call.
508 *\li #ISC_R_SUCCESS -- all is well.
509 *\li #ISC_R_NOMEMORY -- could not mark address as lame.
513 * A reasonable default for RTT adjustments
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 */
520 dns_adb_adjustsrtt(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
521 unsigned int rtt, unsigned int factor);
523 * Mix the round trip time into the existing smoothed rtt.
526 * (where srtt is the existing rtt value, and rtt and factor are arguments to
530 * new_srtt = (old_srtt / 10 * factor) + (rtt / 10 * (10 - factor));
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
543 *\li 0 <= factor <= 10
547 *\li The srtt in addr will be updated to reflect the new global
548 * srtt value. This may include changes made by others.
552 dns_adb_changeflags(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
553 unsigned int bits, unsigned int mask);
557 * Set the flags as given by:
559 *\li newflags = (oldflags & ~mask) | (bits & mask);
569 dns_adb_findaddrinfo(dns_adb_t *adb, isc_sockaddr_t *sa,
570 dns_adbaddrinfo_t **addrp, isc_stdtime_t now);
572 * Return a dns_adbaddrinfo_t that is associated with address 'sa'.
580 *\li addrp != NULL && *addrp == NULL
585 *\li #ISC_R_SHUTTINGDOWN
589 dns_adb_freeaddrinfo(dns_adb_t *adb, dns_adbaddrinfo_t **addrp);
591 * Free a dns_adbaddrinfo_t allocated by dns_adb_findaddrinfo().
597 *\li *addrp is a valid dns_adbaddrinfo_t *.
601 dns_adb_flush(dns_adb_t *adb);
603 * Flushes all cached data from the adb.
610 dns_adb_setadbsize(dns_adb_t *adb, isc_uint32_t size);
612 * Set a target memory size. If memory usage exceeds the target
613 * size entries will be removed before they would have expired on
616 * If 'size' is 0 then memory usage is unlimited.
623 dns_adb_flushname(dns_adb_t *adb, dns_name_t *name);
625 * Flush 'name' from the adb cache.
629 *\li 'name' is valid.
634 #endif /* DNS_ADB_H */