File: //usr/include/bind9/dns/resolver.h
/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* SPDX-License-Identifier: MPL-2.0
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, you can obtain one at https://mozilla.org/MPL/2.0/.
*
* See the COPYRIGHT file distributed with this work for additional
* information regarding copyright ownership.
*/
#pragma once
/*****
***** Module Info
*****/
/*! \file dns/resolver.h
*
* \brief
* This is the BIND 9 resolver, the module responsible for resolving DNS
* requests by iteratively querying authoritative servers and following
* referrals. This is a "full resolver", not to be confused with
* the stub resolvers most people associate with the word "resolver".
* The full resolver is part of the caching name server or resolver
* daemon the stub resolver talks to.
*
* MP:
*\li The module ensures appropriate synchronization of data structures it
* creates and manipulates.
*
* Reliability:
*\li No anticipated impact.
*
* Resources:
*\li TBS
*
* Security:
*\li No anticipated impact.
*
* Standards:
*\li RFCs: 1034, 1035, 2181, TBS
*\li Drafts: TBS
*/
#include <inttypes.h>
#include <stdbool.h>
#include <isc/event.h>
#include <isc/lang.h>
#include <isc/stats.h>
#include <dns/fixedname.h>
#include <dns/types.h>
ISC_LANG_BEGINDECLS
/*%
* A dns_fetchevent_t is sent when a 'fetch' completes. Any of 'db',
* 'node', 'rdataset', and 'sigrdataset' may be bound. It is the
* receiver's responsibility to detach before freeing the event.
* \brief
* 'rdataset', 'sigrdataset', 'client' and 'id' are the values that were
* supplied when dns_resolver_createfetch() was called. They are returned
* to the caller so that they may be freed.
*/
typedef struct dns_fetchevent {
ISC_EVENT_COMMON(struct dns_fetchevent);
dns_fetch_t *fetch;
isc_result_t result;
dns_rdatatype_t qtype;
dns_db_t *db;
dns_dbnode_t *node;
dns_rdataset_t *rdataset;
dns_rdataset_t *sigrdataset;
dns_fixedname_t fname;
dns_name_t *foundname;
const isc_sockaddr_t *client;
dns_messageid_t id;
isc_result_t vresult;
} dns_fetchevent_t;
/*%
* The two quota types (fetches-per-zone and fetches-per-server)
*/
typedef enum { dns_quotatype_zone = 0, dns_quotatype_server } dns_quotatype_t;
/*
* Options that modify how a 'fetch' is done.
*/
enum {
DNS_FETCHOPT_TCP = 1 << 0, /*%< Use TCP. */
DNS_FETCHOPT_UNSHARED = 1 << 1, /*%< See below. */
DNS_FETCHOPT_RECURSIVE = 1 << 2, /*%< Set RD? */
DNS_FETCHOPT_NOEDNS0 = 1 << 3, /*%< Do not use EDNS. */
DNS_FETCHOPT_FORWARDONLY = 1 << 4, /*%< Only use forwarders. */
DNS_FETCHOPT_NOVALIDATE = 1 << 5, /*%< Disable validation. */
DNS_FETCHOPT_WANTNSID = 1 << 6, /*%< Request NSID */
DNS_FETCHOPT_PREFETCH = 1 << 7, /*%< Do prefetch */
DNS_FETCHOPT_NOCDFLAG = 1 << 8, /*%< Don't set CD flag. */
DNS_FETCHOPT_NONTA = 1 << 9, /*%< Ignore NTA table. */
DNS_FETCHOPT_NOCACHED = 1 << 10, /*%< Force cache update. */
DNS_FETCHOPT_QMINIMIZE = 1 << 11, /*%< Use qname minimization. */
DNS_FETCHOPT_NOFOLLOW = 1 << 12, /*%< Don't retrieve the NS RRset
* from the child zone when a
* delegation is returned in
* response to a NS query. */
DNS_FETCHOPT_QMIN_STRICT = 1 << 13, /*%< Do not work around servers
* that return errors on
* non-empty terminals. */
DNS_FETCHOPT_QMIN_SKIP_IP6A = 1 << 14, /*%< Skip some labels when
* doing qname minimization
* on ip6.arpa. */
DNS_FETCHOPT_NOFORWARD = 1 << 15, /*%< Do not use forwarders if
* possible. */
DNS_FETCHOPT_TRYSTALE_ONTIMEOUT = 1 << 16,
/*% EDNS version bits: */
DNS_FETCHOPT_EDNSVERSIONSET = 1 << 23,
DNS_FETCHOPT_EDNSVERSIONSHIFT = 24,
DNS_FETCHOPT_EDNSVERSIONMASK = 0xff000000,
};
/*
* Upper bounds of class of query RTT (ms). Corresponds to
* dns_resstatscounter_queryrttX statistics counters.
*/
#define DNS_RESOLVER_QRYRTTCLASS0 10
#define DNS_RESOLVER_QRYRTTCLASS0STR "10"
#define DNS_RESOLVER_QRYRTTCLASS1 100
#define DNS_RESOLVER_QRYRTTCLASS1STR "100"
#define DNS_RESOLVER_QRYRTTCLASS2 500
#define DNS_RESOLVER_QRYRTTCLASS2STR "500"
#define DNS_RESOLVER_QRYRTTCLASS3 800
#define DNS_RESOLVER_QRYRTTCLASS3STR "800"
#define DNS_RESOLVER_QRYRTTCLASS4 1600
#define DNS_RESOLVER_QRYRTTCLASS4STR "1600"
/*
* XXXRTH Should this API be made semi-private? (I.e.
* _dns_resolver_create()).
*/
#define DNS_RESOLVER_CHECKNAMES 0x01
#define DNS_RESOLVER_CHECKNAMESFAIL 0x02
#define DNS_QMIN_MAXLABELS 7
#define DNS_QMIN_MAX_NO_DELEGATION 3
#define DNS_MAX_LABELS 127
isc_result_t
dns_resolver_create(dns_view_t *view, isc_taskmgr_t *taskmgr,
unsigned int ntasks, unsigned int ndisp, isc_nm_t *nm,
isc_timermgr_t *timermgr, unsigned int options,
dns_dispatchmgr_t *dispatchmgr, dns_dispatch_t *dispatchv4,
dns_dispatch_t *dispatchv6, dns_resolver_t **resp);
/*%<
* Create a resolver.
*
* Notes:
*
*\li Generally, applications should not create a resolver directly, but
* should instead call dns_view_createresolver().
*
* Requires:
*
*\li 'view' is a valid view.
*
*\li 'taskmgr' is a valid task manager.
*
*\li 'ntasks' > 0.
*
*\li 'nm' is a valid network manager.
*
*\li 'timermgr' is a valid timer manager.
*
*\li 'dispatchv4' is a dispatch with an IPv4 UDP socket, or is NULL.
* If not NULL, 'ndisp' clones of it will be created by the resolver.
*
*\li 'dispatchv6' is a dispatch with an IPv6 UDP socket, or is NULL.
* If not NULL, 'ndisp' clones of it will be created by the resolver.
*
*\li resp != NULL && *resp == NULL.
*
* Returns:
*
*\li #ISC_R_SUCCESS On success.
*
*\li Anything else Failure.
*/
void
dns_resolver_freeze(dns_resolver_t *res);
/*%<
* Freeze resolver.
*
* Notes:
*
*\li Certain configuration changes cannot be made after the resolver
* is frozen. Fetches cannot be created until the resolver is frozen.
*
* Requires:
*
*\li 'res' is a valid resolver.
*
* Ensures:
*
*\li 'res' is frozen.
*/
void
dns_resolver_prime(dns_resolver_t *res);
/*%<
* Prime resolver.
*
* Notes:
*
*\li Resolvers which have a forwarding policy other than dns_fwdpolicy_only
* need to be primed with the root nameservers, otherwise the root
* nameserver hints data may be used indefinitely. This function requests
* that the resolver start a priming fetch, if it isn't already priming.
*
* Requires:
*
*\li 'res' is a valid, frozen resolver.
*/
void
dns_resolver_whenshutdown(dns_resolver_t *res, isc_task_t *task,
isc_event_t **eventp);
/*%<
* Send '*eventp' to 'task' when 'res' has completed shutdown.
*
* Notes:
*
*\li It is not safe to detach the last reference to 'res' until
* shutdown is complete.
*
* Requires:
*
*\li 'res' is a valid resolver.
*
*\li 'task' is a valid task.
*
*\li *eventp is a valid event.
*
* Ensures:
*
*\li *eventp == NULL.
*/
void
dns_resolver_shutdown(dns_resolver_t *res);
/*%<
* Start the shutdown process for 'res'.
*
* Notes:
*
*\li This call has no effect if the resolver is already shutting down.
*
* Requires:
*
*\li 'res' is a valid resolver.
*/
void
dns_resolver_attach(dns_resolver_t *source, dns_resolver_t **targetp);
void
dns_resolver_detach(dns_resolver_t **resp);
isc_result_t
dns_resolver_createfetch(dns_resolver_t *res, const dns_name_t *name,
dns_rdatatype_t type, const dns_name_t *domain,
dns_rdataset_t *nameservers,
dns_forwarders_t *forwarders,
const isc_sockaddr_t *client, dns_messageid_t id,
unsigned int options, unsigned int depth,
isc_counter_t *qc, isc_counter_t *gqc,
isc_task_t *task, isc_taskaction_t action, void *arg,
dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset,
dns_fetch_t **fetchp);
/*%<
* Recurse to answer a question.
*
* Notes:
*
*\li This call starts a query for 'name', type 'type'.
*
*\li The 'domain' is a parent domain of 'name' for which
* a set of name servers 'nameservers' is known. If no
* such name server information is available, set
* 'domain' and 'nameservers' to NULL.
*
*\li 'forwarders' is unimplemented, and subject to change when
* we figure out how selective forwarding will work.
*
*\li When the fetch completes (successfully or otherwise), a
* #DNS_EVENT_FETCHDONE event with action 'action' and arg 'arg' will be
* posted to 'task'.
*
*\li The values of 'rdataset' and 'sigrdataset' will be returned in
* the FETCHDONE event.
*
*\li 'client' and 'id' are used for duplicate query detection. '*client'
* must remain stable until after 'action' has been called or
* dns_resolver_cancelfetch() is called.
*
* Requires:
*
*\li 'res' is a valid resolver that has been frozen.
*
*\li 'name' is a valid name.
*
*\li 'type' is not a meta type other than ANY.
*
*\li 'domain' is a valid name or NULL.
*
*\li 'nameservers' is a valid NS rdataset (whose owner name is 'domain')
* iff. 'domain' is not NULL.
*
*\li 'forwarders' is NULL.
*
*\li 'client' is a valid sockaddr or NULL.
*
*\li 'options' contains valid options.
*
*\li 'rdataset' is a valid, disassociated rdataset.
*
*\li 'sigrdataset' is NULL, or is a valid, disassociated rdataset.
*
*\li fetchp != NULL && *fetchp == NULL.
*
* Returns:
*
*\li #ISC_R_SUCCESS Success
*\li #DNS_R_DUPLICATE
*\li #DNS_R_DROP
*
*\li Many other values are possible, all of which indicate failure.
*/
void
dns_resolver_cancelfetch(dns_fetch_t *fetch);
/*%<
* Cancel 'fetch'.
*
* Notes:
*
*\li If 'fetch' has not completed, post its FETCHDONE event with a
* result code of #ISC_R_CANCELED.
*
* Requires:
*
*\li 'fetch' is a valid fetch.
*/
void
dns_resolver_destroyfetch(dns_fetch_t **fetchp);
/*%<
* Destroy 'fetch'.
*
* Requires:
*
*\li '*fetchp' is a valid fetch.
*
*\li The caller has received the FETCHDONE event (either because the
* fetch completed or because dns_resolver_cancelfetch() was called).
*
* Ensures:
*
*\li *fetchp == NULL.
*/
void
dns_resolver_logfetch(dns_fetch_t *fetch, isc_log_t *lctx,
isc_logcategory_t *category, isc_logmodule_t *module,
int level, bool duplicateok);
/*%<
* Dump a log message on internal state at the completion of given 'fetch'.
* 'lctx', 'category', 'module', and 'level' are used to write the log message.
* By default, only one log message is written even if the corresponding fetch
* context serves multiple clients; if 'duplicateok' is true the suppression
* is disabled and the message can be written every time this function is
* called.
*
* Requires:
*
*\li 'fetch' is a valid fetch, and has completed.
*/
dns_dispatchmgr_t *
dns_resolver_dispatchmgr(dns_resolver_t *resolver);
dns_dispatch_t *
dns_resolver_dispatchv4(dns_resolver_t *resolver);
dns_dispatch_t *
dns_resolver_dispatchv6(dns_resolver_t *resolver);
isc_taskmgr_t *
dns_resolver_taskmgr(dns_resolver_t *resolver);
uint32_t
dns_resolver_getlamettl(dns_resolver_t *resolver);
/*%<
* Get the resolver's lame-ttl. zero => no lame processing.
*
* Requires:
*\li 'resolver' to be valid.
*/
void
dns_resolver_setlamettl(dns_resolver_t *resolver, uint32_t lame_ttl);
/*%<
* Set the resolver's lame-ttl. zero => no lame processing.
*
* Requires:
*\li 'resolver' to be valid.
*/
void
dns_resolver_addalternate(dns_resolver_t *resolver, const isc_sockaddr_t *alt,
const dns_name_t *name, in_port_t port);
/*%<
* Add alternate addresses to be tried in the event that the nameservers
* for a zone are not available in the address families supported by the
* operating system.
*
* Require:
* \li only one of 'name' or 'alt' to be valid.
*/
void
dns_resolver_setudpsize(dns_resolver_t *resolver, uint16_t udpsize);
/*%<
* Set the EDNS UDP buffer size advertised by the server.
*/
uint16_t
dns_resolver_getudpsize(dns_resolver_t *resolver);
/*%<
* Get the current EDNS UDP buffer size.
*/
void
dns_resolver_reset_algorithms(dns_resolver_t *resolver);
/*%<
* Clear the disabled DNSSEC algorithms.
*/
void
dns_resolver_reset_ds_digests(dns_resolver_t *resolver);
/*%<
* Clear the disabled DS digest types.
*/
isc_result_t
dns_resolver_disable_algorithm(dns_resolver_t *resolver, const dns_name_t *name,
unsigned int alg);
/*%<
* Mark the given DNSSEC algorithm as disabled and below 'name'.
* Valid algorithms are less than 256.
*
* Returns:
*\li #ISC_R_SUCCESS
*\li #ISC_R_RANGE
*\li #ISC_R_NOMEMORY
*/
isc_result_t
dns_resolver_disable_ds_digest(dns_resolver_t *resolver, const dns_name_t *name,
unsigned int digest_type);
/*%<
* Mark the given DS digest type as disabled and below 'name'.
* Valid types are less than 256.
*
* Returns:
*\li #ISC_R_SUCCESS
*\li #ISC_R_RANGE
*\li #ISC_R_NOMEMORY
*/
bool
dns_resolver_algorithm_supported(dns_resolver_t *resolver,
const dns_name_t *name, unsigned int alg);
/*%<
* Check if the given algorithm is supported by this resolver.
* This checks whether the algorithm has been disabled via
* dns_resolver_disable_algorithm(), then checks the underlying
* crypto libraries if it was not specifically disabled.
*/
bool
dns_resolver_ds_digest_supported(dns_resolver_t *resolver,
const dns_name_t *name,
unsigned int digest_type);
/*%<
* Check if the given digest type is supported by this resolver.
* This checks whether the digest type has been disabled via
* dns_resolver_disable_ds_digest(), then checks the underlying
* crypto libraries if it was not specifically disabled.
*/
void
dns_resolver_resetmustbesecure(dns_resolver_t *resolver);
isc_result_t
dns_resolver_setmustbesecure(dns_resolver_t *resolver, const dns_name_t *name,
bool value);
bool
dns_resolver_getmustbesecure(dns_resolver_t *resolver, const dns_name_t *name);
void
dns_resolver_settimeout(dns_resolver_t *resolver, unsigned int timeout);
/*%<
* Set the length of time the resolver will work on a query, in milliseconds.
*
* 'timeout' was originally defined in seconds, and later redefined to be in
* milliseconds. Values less than or equal to 300 are treated as seconds.
*
* If timeout is 0, the default timeout will be applied.
*
* Requires:
* \li resolver to be valid.
*/
unsigned int
dns_resolver_gettimeout(dns_resolver_t *resolver);
/*%<
* Get the current length of time the resolver will work on a query,
* in milliseconds.
*
* Requires:
* \li resolver to be valid.
*/
void
dns_resolver_setclientsperquery(dns_resolver_t *resolver, uint32_t min,
uint32_t max);
void
dns_resolver_setfetchesperzone(dns_resolver_t *resolver, uint32_t clients);
void
dns_resolver_getclientsperquery(dns_resolver_t *resolver, uint32_t *cur,
uint32_t *min, uint32_t *max);
bool
dns_resolver_getzeronosoattl(dns_resolver_t *resolver);
void
dns_resolver_setzeronosoattl(dns_resolver_t *resolver, bool state);
unsigned int
dns_resolver_getretryinterval(dns_resolver_t *resolver);
void
dns_resolver_setretryinterval(dns_resolver_t *resolver, unsigned int interval);
/*%<
* Sets the amount of time, in milliseconds, that is waited for a reply
* to a server before another server is tried. Interacts with the
* value of dns_resolver_getnonbackofftries() by trying that number of times
* at this interval, before doing exponential backoff and doubling the interval
* on each subsequent try, to a maximum of 10 seconds. Defaults to 800 ms;
* silently capped at 2000 ms.
*
* Requires:
* \li resolver to be valid.
* \li interval > 0.
*/
unsigned int
dns_resolver_getnonbackofftries(dns_resolver_t *resolver);
void
dns_resolver_setnonbackofftries(dns_resolver_t *resolver, unsigned int tries);
/*%<
* Sets the number of failures of getting a reply from remote servers for
* a query before backing off by doubling the retry interval for each
* subsequent request sent. Defaults to 3.
*
* Requires:
* \li resolver to be valid.
* \li tries > 0.
*/
unsigned int
dns_resolver_getoptions(dns_resolver_t *resolver);
/*%<
* Get the resolver options.
*
* Requires:
* \li resolver to be valid.
*/
void
dns_resolver_addbadcache(dns_resolver_t *resolver, const dns_name_t *name,
dns_rdatatype_t type, isc_time_t *expire);
/*%<
* Add a entry to the bad cache for <name,type> that will expire at 'expire'.
*
* Requires:
* \li resolver to be valid.
* \li name to be valid.
*/
bool
dns_resolver_getbadcache(dns_resolver_t *resolver, const dns_name_t *name,
dns_rdatatype_t type, isc_time_t *now);
/*%<
* Check to see if there is a unexpired entry in the bad cache for
* <name,type>.
*
* Requires:
* \li resolver to be valid.
* \li name to be valid.
*/
void
dns_resolver_flushbadcache(dns_resolver_t *resolver, const dns_name_t *name);
/*%<
* Flush the bad cache of all entries at 'name' if 'name' is non NULL.
* Flush the entire bad cache if 'name' is NULL.
*
* Requires:
* \li resolver to be valid.
*/
void
dns_resolver_flushbadnames(dns_resolver_t *resolver, const dns_name_t *name);
/*%<
* Flush the bad cache of all entries at or below 'name'.
*
* Requires:
* \li resolver to be valid.
* \li name != NULL
*/
void
dns_resolver_printbadcache(dns_resolver_t *resolver, FILE *fp);
/*%
* Print out the contents of the bad cache to 'fp'.
*
* Requires:
* \li resolver to be valid.
*/
void
dns_resolver_setmaxdepth(dns_resolver_t *resolver, unsigned int maxdepth);
unsigned int
dns_resolver_getmaxdepth(dns_resolver_t *resolver);
/*%
* Get and set how many NS indirections will be followed when looking for
* nameserver addresses.
*
* Requires:
* \li resolver to be valid.
*/
void
dns_resolver_setmaxqueries(dns_resolver_t *resolver, unsigned int queries);
unsigned int
dns_resolver_getmaxqueries(dns_resolver_t *resolver);
/*%
* Get and set how many iterative queries will be allowed before
* terminating a recursive query.
*
* Requires:
* \li resolver to be valid.
*/
void
dns_resolver_setquotaresponse(dns_resolver_t *resolver, dns_quotatype_t which,
isc_result_t resp);
isc_result_t
dns_resolver_getquotaresponse(dns_resolver_t *resolver, dns_quotatype_t which);
/*%
* Get and set the result code that will be used when quotas
* are exceeded. If 'which' is set to quotatype "zone", then the
* result specified in 'resp' will be used when the fetches-per-zone
* quota is exceeded by a fetch. If 'which' is set to quotatype "server",
* then the result specified in 'resp' will be used when the
* fetches-per-server quota has been exceeded for all the
* authoritative servers for a zone. Valid choices are
* DNS_R_DROP or DNS_R_SERVFAIL.
*
* Requires:
* \li 'resolver' to be valid.
* \li 'which' to be dns_quotatype_zone or dns_quotatype_server
* \li 'resp' to be DNS_R_DROP or DNS_R_SERVFAIL.
*/
void
dns_resolver_dumpfetches(dns_resolver_t *resolver, isc_statsformat_t format,
FILE *fp);
#ifdef ENABLE_AFL
/*%
* Enable fuzzing of resolver, changes behaviour and eliminates retries
*/
void
dns_resolver_setfuzzing(void);
#endif /* ifdef ENABLE_AFL */
ISC_LANG_ENDDECLS