/*
* Copyright (C) Internet Systems Consortium, Inc. ("ISC")
*
* 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.
*/
#ifndef DNS_ADB_H
#define DNS_ADB_H 1
/*****
***** Module Info
*****/
/*! \file dns/adb.h
*\brief
* DNS Address Database
*
* This module implements an address database (ADB) for mapping a name
* to an isc_sockaddr_t. It also provides statistical information on
* how good that address might be.
*
* A client will pass in a dns_name_t, and the ADB will walk through
* the rdataset looking up addresses associated with the name. If it
* is found on the internal lists, a structure is filled in with the
* address information and stats for found addresses.
*
* If the name cannot be found on the internal lists, a new entry will
* be created for a name if all the information needed can be found
* in the zone table or cache. This new address will then be returned.
*
* If a request must be made to remote servers to satisfy a name lookup,
* this module will start fetches to try to complete these addresses. When
* at least one more completes, an event is sent to the caller. If none of
* them resolve before the fetch times out, an event indicating this is
* sent instead.
*
* Records are stored internally until a timer expires. The timer is the
* smaller of the TTL or signature validity period.
*
* Lameness is stored per <qname,qtype> tuple, and this data hangs off each
* address field. When an address is marked lame for a given tuple the address
* will not be returned to a caller.
*
*
* MP:
*
*\li The ADB takes care of all necessary locking.
*
*\li Only the task which initiated the name lookup can cancel the lookup.
*
*
* Security:
*
*\li None, since all data stored is required to be pre-filtered.
* (Cache needs to be sane, fetches return bounds-checked and sanity-
* checked data, caller passes a good dns_name_t for the zone, etc)
*/
/***
*** Imports
***/
#include <inttypes.h>
#include <stdbool.h>
#include <isc/lang.h>
#include <isc/magic.h>
#include <isc/mem.h>
#include <isc/sockaddr.h>
#include <dns/types.h>
#include <dns/view.h>
ISC_LANG_BEGINDECLS
/***
*** Magic number checks
***/
#define DNS_ADBFIND_MAGIC ISC_MAGIC('a','d','b','H')
#define DNS_ADBFIND_VALID(x) ISC_MAGIC_VALID(x, DNS_ADBFIND_MAGIC)
#define DNS_ADBADDRINFO_MAGIC ISC_MAGIC('a','d','A','I')
#define DNS_ADBADDRINFO_VALID(x) ISC_MAGIC_VALID(x, DNS_ADBADDRINFO_MAGIC)
/***
*** TYPES
***/
typedef struct dns_adbname dns_adbname_t;
/*!
*\brief
* Represents a lookup for a single name.
*
* On return, the client can safely use "list", and can reorder the list.
* Items may not be _deleted_ from this list, however, or added to it
* other than by using the dns_adb_*() API.
*/
struct dns_adbfind {
/* Public */
unsigned int magic; /*%< RO: magic */
dns_adbaddrinfolist_t list; /*%< RO: list of addrs */
unsigned int query_pending; /*%< RO: partial list */
unsigned int partial_result; /*%< RO: addrs missing */
unsigned int options; /*%< RO: options */
isc_result_t result_v4; /*%< RO: v4 result */
isc_result_t result_v6; /*%< RO: v6 result */
ISC_LINK(dns_adbfind_t) publink; /*%< RW: client use */
/* Private */
isc_mutex_t lock; /* locks all below */
in_port_t port;
int name_bucket;
unsigned int flags;
dns_adbname_t *adbname;
dns_adb_t *adb;
isc_event_t event;
ISC_LINK(dns_adbfind_t) plink;
};
/*
* _INET:
* _INET6:
* return addresses of that type.
*
* _EMPTYEVENT:
* Only schedule an event if no addresses are known.
* Must set _WANTEVENT for this to be meaningful.
*
* _WANTEVENT:
* An event is desired. Check this bit in the returned find to see
* if one will actually be generated.
*
* _AVOIDFETCHES:
* If set, fetches will not be generated unless no addresses are
* available in any of the address families requested.
*
* _STARTATZONE:
* Fetches will start using the closest zone data or use the root servers.
* This is useful for reestablishing glue that has expired.
*
* _GLUEOK:
* _HINTOK:
* Glue or hints are ok. These are used when matching names already
* in the adb, and when dns databases are searched.
*
* _RETURNLAME:
* Return lame servers in a find, so that all addresses are returned.
*
* _LAMEPRUNED:
* At least one address was omitted from the list because it was lame.
* This bit will NEVER be set if _RETURNLAME is set in the createfind().
*/
/*% Return addresses of type INET. */
#define DNS_ADBFIND_INET 0x00000001
/*% Return addresses of type INET6. */
#define DNS_ADBFIND_INET6 0x00000002
#define DNS_ADBFIND_ADDRESSMASK 0x00000003
/*%
* Only schedule an event if no addresses are known.
* Must set _WANTEVENT for this to be meaningful.
*/
#define DNS_ADBFIND_EMPTYEVENT 0x00000004
/*%
* An event is desired. Check this bit in the returned find to see
* if one will actually be generated.
*/
#define DNS_ADBFIND_WANTEVENT 0x00000008
/*%
* If set, fetches will not be generated unless no addresses are
* available in any of the address families requested.
*/
#define DNS_ADBFIND_AVOIDFETCHES 0x00000010
/*%
* Fetches will start using the closest zone data or use the root servers.
* This is useful for reestablishing glue that has expired.
*/
#define DNS_ADBFIND_STARTATZONE 0x00000020
/*%
* Glue or hints are ok. These are used when matching names already
* in the adb, and when dns databases are searched.
*/
#define DNS_ADBFIND_GLUEOK 0x00000040
/*%
* Glue or hints are ok. These are used when matching names already
* in the adb, and when dns databases are searched.
*/
#define DNS_ADBFIND_HINTOK 0x00000080
/*%
* Return lame servers in a find, so that all addresses are returned.
*/
#define DNS_ADBFIND_RETURNLAME 0x00000100
/*%
* Only schedule an event if no addresses are known.
* Must set _WANTEVENT for this to be meaningful.
*/
#define DNS_ADBFIND_LAMEPRUNED 0x00000200
/*%
* The server's fetch quota is exceeded; it will be treated as
* lame for this query.
*/
#define DNS_ADBFIND_OVERQUOTA 0x00000400
/*%
* Don't perform a fetch even if there are no address records available.
*/
#define DNS_ADBFIND_NOFETCH 0x00000800
/*%
* The answers to queries come back as a list of these.
*/
struct dns_adbaddrinfo {
unsigned int magic; /*%< private */
isc_sockaddr_t sockaddr; /*%< [rw] */
unsigned int srtt; /*%< [rw] microsecs */
isc_dscp_t dscp;
unsigned int flags; /*%< [rw] */
dns_adbentry_t *entry; /*%< private */
ISC_LINK(dns_adbaddrinfo_t) publink;
};
/*!<
* The event sent to the caller task is just a plain old isc_event_t. It
* contains no data other than a simple status, passed in the "type" field
* to indicate that another address resolved, or all partially resolved
* addresses have failed to resolve.
*
* "sender" is the dns_adbfind_t used to issue this query.
*
* This is simply a standard event, with the "type" set to:
*
*\li #DNS_EVENT_ADBMOREADDRESSES -- another address resolved.
*\li #DNS_EVENT_ADBNOMOREADDRESSES -- all pending addresses failed,
* were canceled, or otherwise will
* not be usable.
*\li #DNS_EVENT_ADBCANCELED -- The request was canceled by a
* 3rd party.
*\li #DNS_EVENT_ADBNAMEDELETED -- The name was deleted, so this request
* was canceled.
*
* In each of these cases, the addresses returned by the initial call
* to dns_adb_createfind() can still be used until they are no longer needed.
*/
/****
**** FUNCTIONS
****/
isc_result_t
dns_adb_create(isc_mem_t *mem, dns_view_t *view, isc_timermgr_t *tmgr,
isc_taskmgr_t *taskmgr, dns_adb_t **newadb);
/*%<
* Create a new ADB.
*
* Notes:
*
*\li Generally, applications should not create an ADB directly, but
* should instead call dns_view_createresolver().
*
* Requires:
*
*\li 'mem' must be a valid memory context.
*
*\li 'view' be a pointer to a valid view.
*
*\li 'tmgr' be a pointer to a valid timer manager.
*
*\li 'taskmgr' be a pointer to a valid task manager.
*
*\li 'newadb' != NULL && '*newadb' == NULL.
*
* Returns:
*
*\li #ISC_R_SUCCESS after happiness.
*\li #ISC_R_NOMEMORY after resource allocation failure.
*/
void
dns_adb_attach(dns_adb_t *adb, dns_adb_t **adbp);
/*%
* Attach to an 'adb' to 'adbp'.
*
* Requires:
*\li 'adb' to be a valid dns_adb_t, created via dns_adb_create().
*\li 'adbp' to be a valid pointer to a *dns_adb_t which is initialized
* to NULL.
*/
void
dns_adb_detach(dns_adb_t **adb);
/*%
* Delete the ADB. Sets *ADB to NULL. Cancels any outstanding requests.
*
* Requires:
*
*\li 'adb' be non-NULL and '*adb' be a valid dns_adb_t, created via
* dns_adb_create().
*/
void
dns_adb_whenshutdown(dns_adb_t *adb, isc_task_t *task, isc_event_t **eventp);
/*%
* Send '*eventp' to 'task' when 'adb' has shutdown.
*
* Requires:
*
*\li '*adb' is a valid dns_adb_t.
*
*\li eventp != NULL && *eventp is a valid event.
*
* Ensures:
*
*\li *eventp == NULL
*
*\li The event's sender field is set to the value of adb when the event
* is sent.
*/
void
dns_adb_shutdown(dns_adb_t *adb);
/*%<
* Shutdown 'adb'.
*
* Requires:
*
* \li '*adb' is a valid dns_adb_t.
*/
isc_result_t
dns_adb_createfind(dns_adb_t *adb, isc_task_t *task, isc_taskaction_t action,
void *arg, dns_name_t *name, dns_name_t *qname,
dns_rdatatype_t qtype, unsigned int options,
isc_stdtime_t now, dns_name_t *target,
in_port_t port, dns_adbfind_t **find);
isc_result_t
dns_adb_createfind2(dns_adb_t *adb, isc_task_t *task, isc_taskaction_t action,
void *arg, dns_name_t *name, dns_name_t *qname,
dns_rdatatype_t qtype, unsigned int options,
isc_stdtime_t now, dns_name_t *target, in_port_t port,
unsigned int depth, isc_counter_t *qc,
dns_adbfind_t **find);
/*%<
* Main interface for clients. The adb will look up the name given in
* "name" and will build up a list of found addresses, and perhaps start
* internal fetches to resolve names that are unknown currently.
*
* If other addresses resolve after this call completes, an event will
* be sent to the <task, taskaction, arg> with the sender of that event
* set to a pointer to the dns_adbfind_t returned by this function.
*
* If no events will be generated, the *find->result_v4 and/or result_v6
* members may be examined for address lookup status. The usual #ISC_R_SUCCESS,
* #ISC_R_FAILURE, #DNS_R_NXDOMAIN, and #DNS_R_NXRRSET are returned, along with
* #ISC_R_NOTFOUND meaning the ADB has not _yet_ found the values. In this
* latter case, retrying may produce more addresses.
*
* If events will be returned, the result_v[46] members are only valid
* when that event is actually returned.
*
* The list of addresses returned is unordered. The caller must impose
* any ordering required. The list will not contain "known bad" addresses,
* however. For instance, it will not return hosts that are known to be
* lame for the zone in question.
*
* The caller cannot (directly) modify the contents of the address list's
* fields other than the "link" field. All values can be read at any
* time, however.
*
* The "now" parameter is used only for determining which entries that
* have a specific time to live or expire time should be removed from
* the running database. If specified as zero, the current time will
* be retrieved and used.
*
* If 'target' is not NULL and 'name' is an alias (i.e. the name is
* CNAME'd or DNAME'd to another name), then 'target' will be updated with
* the domain name that 'name' is aliased to.
*
* All addresses returned will have the sockaddr's port set to 'port.'
* The caller may change them directly in the dns_adbaddrinfo_t since
* they are copies of the internal address only.
*
* XXXMLG Document options, especially the flags which control how
* events are sent.
*
* Requires:
*
*\li *adb be a valid isc_adb_t object.
*
*\li If events are to be sent, *task be a valid task,
* and isc_taskaction_t != NULL.
*
*\li *name is a valid dns_name_t.
*
*\li qname != NULL and *qname be a valid dns_name_t.
*
*\li target == NULL or target is a valid name with a buffer.
*
*\li find != NULL && *find == NULL.
*
* Returns:
*
*\li #ISC_R_SUCCESS Addresses might have been returned, and events will be
* delivered for unresolved addresses.
*\li #ISC_R_NOMORE Addresses might have been returned, but no events
* will ever be posted for this context. This is only
* returned if task != NULL.
*\li #ISC_R_NOMEMORY insufficient resources
*\li #DNS_R_ALIAS 'name' is an alias for another name.
*
* Calls, and returns error codes from:
*
*\li isc_stdtime_get()
*
* Notes:
*
*\li No internal reference to "name" exists after this function
* returns.
*/
void
dns_adb_cancelfind(dns_adbfind_t *find);
/*%<
* Cancels the find, and sends the event off to the caller.
*
* It is an error to call dns_adb_cancelfind() on a find where
* no event is wanted, or will ever be sent.
*
* Note:
*
*\li It is possible that the real completion event was posted just
* before the dns_adb_cancelfind() call was made. In this case,
* dns_adb_cancelfind() will do nothing. The event callback needs
* to be prepared to find this situation (i.e. result is valid but
* the caller expects it to be canceled).
*
* Requires:
*
*\li 'find' be a valid dns_adbfind_t pointer.
*
*\li events would have been posted to the task. This can be checked
* with (find->options & DNS_ADBFIND_WANTEVENT).
*
* Ensures:
*
*\li The event was posted to the task.
*/
void
dns_adb_destroyfind(dns_adbfind_t **find);
/*%<
* Destroys the find reference.
*
* Note:
*
*\li This can only be called after the event was delivered for a
* find. Additionally, the event MUST have been freed via
* isc_event_free() BEFORE this function is called.
*
* Requires:
*
*\li 'find' != NULL and *find be valid dns_adbfind_t pointer.
*
* Ensures:
*
*\li No "address found" events will be posted to the originating task
* after this function returns.
*/
void
dns_adb_dump(dns_adb_t *adb, FILE *f);
/*%<
* This function is only used for debugging. It will dump as much of the
* state of the running system as possible.
*
* Requires:
*
*\li adb be valid.
*
*\li f != NULL, and is a file open for writing.
*/
void
dns_adb_dumpfind(dns_adbfind_t *find, FILE *f);
/*%<
* This function is only used for debugging. Dump the data associated
* with a find.
*
* Requires:
*
*\li find is valid.
*
* \li f != NULL, and is a file open for writing.
*/
isc_result_t
dns_adb_marklame(dns_adb_t *adb, dns_adbaddrinfo_t *addr, dns_name_t *qname,
dns_rdatatype_t type, isc_stdtime_t expire_time);
/*%<
* Mark the given address as lame for the <qname,qtype>. expire_time should
* be set to the time when the entry should expire. That is, if it is to
* expire 10 minutes in the future, it should set it to (now + 10 * 60).
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*
*\li qname be the qname used in the dns_adb_createfind() call.
*
* Returns:
*
*\li #ISC_R_SUCCESS -- all is well.
*\li #ISC_R_NOMEMORY -- could not mark address as lame.
*/
/*
* Reasonable defaults for RTT adjustments
*
* (Note: these values function both as scaling factors and as
* indicators of the type of RTT adjustment operation taking place.
* Adjusting the scaling factors is fine, as long as they all remain
* unique values.)
*/
#define DNS_ADB_RTTADJDEFAULT 7 /*%< default scale */
#define DNS_ADB_RTTADJREPLACE 0 /*%< replace with our rtt */
#define DNS_ADB_RTTADJAGE 10 /*%< age this rtt */
void
dns_adb_adjustsrtt(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
unsigned int rtt, unsigned int factor);
/*%<
* Mix the round trip time into the existing smoothed rtt.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*
*\li 0 <= factor <= 10
*
* Note:
*
*\li The srtt in addr will be updated to reflect the new global
* srtt value. This may include changes made by others.
*/
void
dns_adb_agesrtt(dns_adb_t *adb, dns_adbaddrinfo_t *addr, isc_stdtime_t now);
/*
* dns_adb_agesrtt is equivalent to dns_adb_adjustsrtt with factor
* equal to DNS_ADB_RTTADJAGE and the current time passed in.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*
* Note:
*
*\li The srtt in addr will be updated to reflect the new global
* srtt value. This may include changes made by others.
*/
void
dns_adb_changeflags(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
unsigned int bits, unsigned int mask);
/*%
* Change Flags.
*
* Set the flags as given by:
*
*\li newflags = (oldflags & ~mask) | (bits & mask);
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
void
dns_adb_setudpsize(dns_adb_t *adb, dns_adbaddrinfo_t *addr, unsigned int size);
/*%
* Update seen UDP response size. The largest seen will be returned by
* dns_adb_getudpsize().
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
unsigned int
dns_adb_getudpsize(dns_adb_t *adb, dns_adbaddrinfo_t *addr);
/*%
* Return the largest seen UDP response size.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
unsigned int
dns_adb_probesize(dns_adb_t *adb, dns_adbaddrinfo_t *addr);
unsigned int
dns_adb_probesize2(dns_adb_t *adb, dns_adbaddrinfo_t *addr, int lookups);
/*%
* Return suggested EDNS UDP size based on observed responses / failures.
* 'lookups' is the number of times the current lookup has been attempted.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
void
dns_adb_plainresponse(dns_adb_t *adb, dns_adbaddrinfo_t *addr);
/*%
* Record a successful plain DNS response.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
void
dns_adb_timeout(dns_adb_t *adb, dns_adbaddrinfo_t *addr);
/*%
* Record a plain DNS UDP query failed.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
void
dns_adb_ednsto(dns_adb_t *adb, dns_adbaddrinfo_t *addr, unsigned int size);
/*%
* Record a failed EDNS UDP response and the advertised EDNS UDP buffer size
* used.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
bool
dns_adb_noedns(dns_adb_t *adb, dns_adbaddrinfo_t *addr);
/*%
* Return whether EDNS should be disabled for this server.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
isc_result_t
dns_adb_findaddrinfo(dns_adb_t *adb, isc_sockaddr_t *sa,
dns_adbaddrinfo_t **addrp, isc_stdtime_t now);
/*%<
* Return a dns_adbaddrinfo_t that is associated with address 'sa'.
*
* Requires:
*
*\li adb is valid.
*
*\li sa is valid.
*
*\li addrp != NULL && *addrp == NULL
*
* Returns:
*\li #ISC_R_SUCCESS
*\li #ISC_R_NOMEMORY
*\li #ISC_R_SHUTTINGDOWN
*/
void
dns_adb_freeaddrinfo(dns_adb_t *adb, dns_adbaddrinfo_t **addrp);
/*%<
* Free a dns_adbaddrinfo_t allocated by dns_adb_findaddrinfo().
*
* Requires:
*
*\li adb is valid.
*
*\li *addrp is a valid dns_adbaddrinfo_t *.
*/
void
dns_adb_flush(dns_adb_t *adb);
/*%<
* Flushes all cached data from the adb.
*
* Requires:
*\li adb is valid.
*/
void
dns_adb_setadbsize(dns_adb_t *adb, size_t size);
/*%<
* Set a target memory size. If memory usage exceeds the target
* size entries will be removed before they would have expired on
* a random basis.
*
* If 'size' is 0 then memory usage is unlimited.
*
* Requires:
*\li 'adb' is valid.
*/
void
dns_adb_flushname(dns_adb_t *adb, dns_name_t *name);
/*%<
* Flush 'name' from the adb cache.
*
* Requires:
*\li 'adb' is valid.
*\li 'name' is valid.
*/
void
dns_adb_flushnames(dns_adb_t *adb, dns_name_t *name);
/*%<
* Flush 'name' and all subdomains from the adb cache.
*
* Requires:
*\li 'adb' is valid.
*\li 'name' is valid.
*/
void
dns_adb_setcookie(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
const unsigned char *cookie, size_t len);
/*%<
* Record the COOKIE associated with this address. If
* cookie is NULL or len is zero the recorded COOKIE is cleared.
*
* Requires:
*\li 'adb' is valid.
*\li 'addr' is valid.
*/
size_t
dns_adb_getcookie(dns_adb_t *adb, dns_adbaddrinfo_t *addr,
unsigned char *cookie, size_t len);
/*
* Retrieve the saved COOKIE value and store it in 'cookie' which has
* size 'len'.
*
* Requires:
*\li 'adb' is valid.
*\li 'addr' is valid.
*
* Returns:
* The size of the cookie or zero if it doesn't fit in the buffer
* or it doesn't exist.
*/
void
dns_adb_setquota(dns_adb_t *adb, uint32_t quota, uint32_t freq,
double low, double high, double discount);
/*%<
* Set the baseline ADB quota, and configure parameters for the
* quota adjustment algorithm.
*
* If the number of fetches currently waiting for responses from this
* address exceeds the current quota, then additional fetches are spilled.
*
* 'quota' is the highest permissible quota; it will adjust itself
* downward in response to detected congestion.
*
* After every 'freq' fetches have either completed or timed out, an
* exponentially weighted moving average of the ratio of timeouts
* to responses is calculated. If the EWMA goes above a 'high'
* threshold, then the quota is adjusted down one step; if it drops
* below a 'low' threshold, then the quota is adjusted back up one
* step.
*
* The quota adjustment is based on the function (1 / 1 + (n/10)^(3/2)),
* for values of n from 0 to 99. It starts at 100% of the baseline
* quota, and descends after 100 steps to 2%.
*
* 'discount' represents the discount rate of the moving average. Higher
* values cause older values to be discounted sooner, providing a faster
* response to changes in the timeout ratio.
*
* Requires:
*\li 'adb' is valid.
*/
bool
dns_adbentry_overquota(dns_adb_t *adb, dns_adbentry_t *entry);
/*%<
* Returns true if the specified ADB has too many active fetches.
*
* Requires:
*\li 'entry' is valid.
*/
void
dns_adb_beginudpfetch(dns_adb_t *adb, dns_adbaddrinfo_t *addr);
void
dns_adb_endudpfetch(dns_adb_t *adb, dns_adbaddrinfo_t *addr);
/*%
* Begin/end a UDP fetch on a particular address.
*
* These functions increment or decrement the fetch counter for
* the ADB entry so that the fetch quota can be enforced.
*
* Requires:
*
*\li adb be valid.
*
*\li addr be valid.
*/
ISC_LANG_ENDDECLS
#endif /* DNS_ADB_H */
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