adb.h
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/* * 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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