/* * iterator/iterator.h - iterative resolver DNS query response module * * Copyright (c) 2007, NLnet Labs. All rights reserved. * * This software is open source. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * Neither the name of the NLNET LABS nor the names of its contributors may * be used to endorse or promote products derived from this software without * specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ /** * \file * * This file contains a module that performs recusive iterative DNS query * processing. */ #ifndef ITERATOR_ITERATOR_H #define ITERATOR_ITERATOR_H #include "services/outbound_list.h" #include "util/data/msgreply.h" #include "util/module.h" struct delegpt; struct iter_hints; struct iter_forwards; struct iter_donotq; struct iter_prep_list; struct iter_priv; /** max number of targets spawned for a query and its subqueries */ #define MAX_TARGET_COUNT 32 /** max number of query restarts. Determines max number of CNAME chain. */ #define MAX_RESTART_COUNT 8 /** max number of referrals. Makes sure resolver does not run away */ #define MAX_REFERRAL_COUNT 130 /** max number of queries-sent-out. Make sure large NS set does not loop */ #define MAX_SENT_COUNT 32 /** at what query-sent-count to stop target fetch policy */ #define TARGET_FETCH_STOP 3 /** how nice is a server without further information, in msec * Equals rtt initial timeout value. */ #define UNKNOWN_SERVER_NICENESS 376 /** maximum timeout before a host is deemed unsuitable, in msec. * After host_ttl this will be timed out and the host will be tried again. * Equals RTT_MAX_TIMEOUT */ #define USEFUL_SERVER_TOP_TIMEOUT 120000 /** number of retries on outgoing queries */ #define OUTBOUND_MSG_RETRY 5 /** RTT band, within this amount from the best, servers are chosen randomly. * Chosen so that the UNKNOWN_SERVER_NICENESS falls within the band of a * fast server, this causes server exploration as a side benefit. msec. */ #define RTT_BAND 400 /** Start value for blacklisting a host, 2*USEFUL_SERVER_TOP_TIMEOUT in sec */ #define INFRA_BACKOFF_INITIAL 240 /** * Global state for the iterator. */ struct iter_env { /** A flag to indicate whether or not we have an IPv6 route */ int supports_ipv6; /** A flag to indicate whether or not we have an IPv4 route */ int supports_ipv4; /** A set of inetaddrs that should never be queried. */ struct iter_donotq* donotq; /** private address space and private domains */ struct iter_priv* priv; /** The maximum dependency depth that this resolver will pursue. */ int max_dependency_depth; /** * The target fetch policy for each dependency level. This is * described as a simple number (per dependency level): * negative numbers (usually just -1) mean fetch-all, * 0 means only fetch on demand, and * positive numbers mean to fetch at most that many targets. * array of max_dependency_depth+1 size. */ int* target_fetch_policy; }; /** * State of the iterator for a query. */ enum iter_state { /** * Externally generated queries start at this state. Query restarts are * reset to this state. */ INIT_REQUEST_STATE = 0, /** * Root priming events reactivate here, most other events pass * through this naturally as the 2nd part of the INIT_REQUEST_STATE. */ INIT_REQUEST_2_STATE, /** * Stub priming events reactivate here, most other events pass * through this naturally as the 3rd part of the INIT_REQUEST_STATE. */ INIT_REQUEST_3_STATE, /** * Each time a delegation point changes for a given query or a * query times out and/or wakes up, this state is (re)visited. * This state is reponsible for iterating through a list of * nameserver targets. */ QUERYTARGETS_STATE, /** * Responses to queries start at this state. This state handles * the decision tree associated with handling responses. */ QUERY_RESP_STATE, /** Responses to priming queries finish at this state. */ PRIME_RESP_STATE, /** Collecting query class information, for qclass=ANY, when * it spawns off queries for every class, it returns here. */ COLLECT_CLASS_STATE, /** Find NS record to resolve DS record from, walking to the right * NS spot until we find it */ DSNS_FIND_STATE, /** Responses that are to be returned upstream end at this state. * As well as responses to target queries. */ FINISHED_STATE }; /** * Per query state for the iterator module. */ struct iter_qstate { /** * State of the iterator module. * This is the state that event is in or should sent to -- all * requests should start with the INIT_REQUEST_STATE. All * responses should start with QUERY_RESP_STATE. Subsequent * processing of the event will change this state. */ enum iter_state state; /** * Final state for the iterator module. * This is the state that responses should be routed to once the * response is final. For externally initiated queries, this * will be FINISHED_STATE, locally initiated queries will have * different final states. */ enum iter_state final_state; /** * The depth of this query, this means the depth of recursion. * This address is needed for another query, which is an address * needed for another query, etc. Original client query has depth 0. */ int depth; /** * The response */ struct dns_msg* response; /** * This is a list of RRsets that must be prepended to the * ANSWER section of a response before being sent upstream. */ struct iter_prep_list* an_prepend_list; /** Last element of the prepend list */ struct iter_prep_list* an_prepend_last; /** * This is the list of RRsets that must be prepended to the * AUTHORITY section of the response before being sent upstream. */ struct iter_prep_list* ns_prepend_list; /** Last element of the authority prepend list */ struct iter_prep_list* ns_prepend_last; /** query name used for chasing the results. Initially the same as * the state qinfo, but after CNAMEs this will be different. * The query info used to elicit the results needed. */ struct query_info qchase; /** query flags to use when chasing the answer (i.e. RD flag) */ uint16_t chase_flags; /** true if we set RD bit because of last resort recursion lame query*/ int chase_to_rd; /** * This is the current delegation point for an in-progress query. This * object retains state as to which delegation targets need to be * (sub)queried for vs which ones have already been visited. */ struct delegpt* dp; /** state for 0x20 fallback when capsfail happens, 0 not a fallback */ int caps_fallback; /** state for capsfail: current server number to try */ size_t caps_server; /** state for capsfail: stored query for comparisons. Can be NULL if * no response had been seen prior to starting the fallback. */ struct reply_info* caps_reply; /** Current delegation message - returned for non-RD queries */ struct dns_msg* deleg_msg; /** number of outstanding target sub queries */ int num_target_queries; /** outstanding direct queries */ int num_current_queries; /** the number of times this query has been restarted. */ int query_restart_count; /** the number of times this query as followed a referral. */ int referral_count; /** number of queries fired off */ int sent_count; /** number of target queries spawned in [1], for this query and its * subqueries, the malloced-array is shared, [0] refcount. */ int* target_count; /** * The query must store NS records from referrals as parentside RRs * Enabled once it hits resolution problems, to throttle retries. * If enabled it is the pointer to the old delegation point with * the old retry counts for bad-nameserver-addresses. */ struct delegpt* store_parent_NS; /** * The query is for parent-side glue(A or AAAA) for a nameserver. * If the item is seen as glue in a referral, and pside_glue is NULL, * then it is stored in pside_glue for later. * If it was never seen, at the end, then a negative caching element * must be created. * The (data or negative) RR cache element then throttles retries. */ int query_for_pside_glue; /** the parent-side-glue element (NULL if none, its first match) */ struct ub_packed_rrset_key* pside_glue; /** If nonNULL we are walking upwards from DS query to find NS */ uint8_t* dsns_point; /** length of the dname in dsns_point */ size_t dsns_point_len; /** * expected dnssec information for this iteration step. * If dnssec rrsigs are expected and not given, the server is marked * lame (dnssec-lame). */ int dnssec_expected; /** * We are expecting dnssec information, but we also know the server * is DNSSEC lame. The response need not be marked dnssec-lame again. */ int dnssec_lame_query; /** * This is flag that, if true, means that this event is * waiting for a stub priming query. */ int wait_priming_stub; /** * This is a flag that, if true, means that this query is * for (re)fetching glue from a zone. Since the address should * have been glue, query again to the servers that should have * been returning it as glue. * The delegation point must be set to the one that should *not* * be used when creating the state. A higher one will be attempted. */ int refetch_glue; /** list of pending queries to authoritative servers. */ struct outbound_list outlist; }; /** * List of prepend items */ struct iter_prep_list { /** next in list */ struct iter_prep_list* next; /** rrset */ struct ub_packed_rrset_key* rrset; }; /** * Get the iterator function block. * @return: function block with function pointers to iterator methods. */ struct module_func_block* iter_get_funcblock(void); /** * Get iterator state as a string * @param state: to convert * @return constant string that is printable. */ const char* iter_state_to_string(enum iter_state state); /** * See if iterator state is a response state * @param s: to inspect * @return true if response state. */ int iter_state_is_responsestate(enum iter_state s); /** iterator init */ int iter_init(struct module_env* env, int id); /** iterator deinit */ void iter_deinit(struct module_env* env, int id); /** iterator operate on a query */ void iter_operate(struct module_qstate* qstate, enum module_ev event, int id, struct outbound_entry* outbound); /** * Return priming query results to interestes super querystates. * * Sets the delegation point and delegation message (not nonRD queries). * This is a callback from walk_supers. * * @param qstate: query state that finished. * @param id: module id. * @param super: the qstate to inform. */ void iter_inform_super(struct module_qstate* qstate, int id, struct module_qstate* super); /** iterator cleanup query state */ void iter_clear(struct module_qstate* qstate, int id); /** iterator alloc size routine */ size_t iter_get_mem(struct module_env* env, int id); #endif /* ITERATOR_ITERATOR_H */