/*
* util/module.h - DNS handling module interface
*
* 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
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/**
* \file
*
* This file contains the interface for DNS handling modules.
*
* The module interface uses the DNS modules as state machines. The
* state machines are activated in sequence to operate on queries. Once
* they are done, the reply is passed back. In the usual setup the mesh
* is the caller of the state machines and once things are done sends replies
* and invokes result callbacks.
*
* The module provides a number of functions, listed in the module_func_block.
* The module is inited and destroyed and memory usage queries, for the
* module as a whole, for entire-module state (such as a cache). And per-query
* functions are called, operate to move the state machine and cleanup of
* the per-query state.
*
* Most per-query state should simply be allocated in the query region.
* This is destroyed at the end of the query.
*
* The module environment contains services and information and caches
* shared by the modules and the rest of the system. It also contains
* function pointers for module-specific tasks (like sending queries).
*
* *** Example module calls for a normal query
*
* In this example, the query does not need recursion, all the other data
* can be found in the cache. This makes the example shorter.
*
* At the start of the program the iterator module is initialised.
* The iterator module sets up its global state, such as donotquery lists
* and private address trees.
*
* A query comes in, and a mesh entry is created for it. The mesh
* starts the resolution process. The validator module is the first
* in the list of modules, and it is started on this new query. The
* operate() function is called. The validator decides it needs not do
* anything yet until there is a result and returns wait_module, that
* causes the next module in the list to be started.
*
* The next module is the iterator. It is started on the passed query and
* decides to perform a lookup. For this simple example, the delegation
* point information is available, and all the iterator wants to do is
* send a UDP query. The iterator uses env.send_query() to send the
* query. Then the iterator suspends (returns from the operate call).
*
* When the UDP reply comes back (and on errors and timeouts), the
* operate function is called for the query, on the iterator module,
* with the event that there is a reply. The iterator decides that this
* is enough, the work is done. It returns the value finished from the
* operate call, which causes the previous module to be started.
*
* The previous module, the validator module, is started with the event
* that the iterator module is done. The validator decides to validate
* the query. Once it is done (which could take recursive lookups, but
* in this example no recursive lookups are needed), it returns from the
* operate function with finished.
*
* There is no previous module from the validator module, and the mesh
* takes this to mean that the query is finally done. The mesh invokes
* callbacks and sends packets to queriers.
*
* If other modules had been waiting (recursively) on the answer to this
* query, then the mesh will tell them about it. It calls the inform_super
* routine on all the waiting modules, and once that is done it calls all of
* them with the operate() call. During inform_super the query that is done
* still exists and information can be copied from it (but the module should
* not really re-entry codepoints and services). During the operate call
* the modules can use stored state to continue operation with the results.
* (network buffers are used to contain the answer packet during the
* inform_super phase, but after that the network buffers will be cleared
* of their contents so that other tasks can be performed).
*
* *** Example module calls for recursion
*
* A module is called in operate, and it decides that it wants to perform
* recursion. That is, it wants the full state-machine-list to operate on
* a different query. It calls env.attach_sub() to create a new query state.
* The routine returns the newly created state, and potentially the module
* can edit the module-states for the newly created query (i.e. pass along
* some information, like delegation points). The module then suspends,
* returns from the operate routine.
*
* The mesh meanwhile will have the newly created query (or queries) on
* a waiting list, and will call operate() on this query (or queries).
* It starts again at the start of the module list for them. The query
* (or queries) continue to operate their state machines, until they are
* done. When they are done the mesh calls inform_super on the module that
* wanted the recursion. After that the mesh calls operate() on the module
* that wanted to do the recursion, and during this phase the module could,
* for example, decide to create more recursions.
*
* If the module decides it no longer wants the recursive information
* it can call detach_subs. Those queries will still run to completion,
* potentially filling the cache with information. Inform_super is not
* called any more.
*
* The iterator module will fetch items from the cache, so a recursion
* attempt may complete very quickly if the item is in cache. The calling
* module has to wait for completion or eventual timeout. A recursive query
* that times out returns a servfail rcode (servfail is also returned for
* other errors during the lookup).
*
* Results are passed in the qstate, the rcode member is used to pass
* errors without requiring memory allocation, so that the code can continue
* in out-of-memory conditions. If the rcode member is 0 (NOERROR) then
* the dns_msg entry contains a filled out message. This message may
* also contain an rcode that is nonzero, but in this case additional
* information (query, additional) can be passed along.
*
* The rcode and dns_msg are used to pass the result from the the rightmost
* module towards the leftmost modules and then towards the user.
*
* If you want to avoid recursion-cycles where queries need other queries
* that need the first one, use detect_cycle() to see if that will happen.
*
*/
#ifndef UTIL_MODULE_H
#define UTIL_MODULE_H
#include "util/storage/lruhash.h"
#include "util/data/msgreply.h"
#include "util/data/msgparse.h"
struct sldns_buffer;
struct alloc_cache;
struct rrset_cache;
struct key_cache;
struct config_file;
struct slabhash;
struct query_info;
struct edns_data;
struct regional;
struct worker;
struct module_qstate;
struct ub_randstate;
struct mesh_area;
struct mesh_state;
struct val_anchors;
struct val_neg_cache;
struct iter_forwards;
struct iter_hints;
/** Maximum number of modules in operation */
#define MAX_MODULE 5
/**
* Module environment.
* Services and data provided to the module.
*/
struct module_env {
/* --- data --- */
/** config file with config options */
struct config_file* cfg;
/** shared message cache */
struct slabhash* msg_cache;
/** shared rrset cache */
struct rrset_cache* rrset_cache;
/** shared infrastructure cache (edns, lameness) */
struct infra_cache* infra_cache;
/** shared key cache */
struct key_cache* key_cache;
/* --- services --- */
/**
* Send serviced DNS query to server. UDP/TCP and EDNS is handled.
* operate() should return with wait_reply. Later on a callback
* will cause operate() to be called with event timeout or reply.
* The time until a timeout is calculated from roundtrip timing,
* several UDP retries are attempted.
* @param qname: query name. (host order)
* @param qnamelen: length in bytes of qname, including trailing 0.
* @param qtype: query type. (host order)
* @param qclass: query class. (host order)
* @param flags: host order flags word, with opcode and CD bit.
* @param dnssec: if set, EDNS record will have bits set.
* If EDNS_DO bit is set, DO bit is set in EDNS records.
* If BIT_CD is set, CD bit is set in queries with EDNS records.
* @param want_dnssec: if set, the validator wants DNSSEC. Without
* EDNS, the answer is likely to be useless for this domain.
* @param nocaps: do not use caps_for_id, use the qname as given.
* (ignored if caps_for_id is disabled).
* @param addr: where to.
* @param addrlen: length of addr.
* @param zone: delegation point name.
* @param zonelen: length of zone name.
* @param q: wich query state to reactivate upon return.
* @return: false on failure (memory or socket related). no query was
* sent. Or returns an outbound entry with qsent and qstate set.
* This outbound_entry will be used on later module invocations
* that involve this query (timeout, error or reply).
*/
struct outbound_entry* (*send_query)(uint8_t* qname, size_t qnamelen,
uint16_t qtype, uint16_t qclass, uint16_t flags, int dnssec,
int want_dnssec, int nocaps, struct sockaddr_storage* addr,
socklen_t addrlen, uint8_t* zone, size_t zonelen,
struct module_qstate* q);
/**
* Detach-subqueries.
* Remove all sub-query references from this query state.
* Keeps super-references of those sub-queries correct.
* Updates stat items in mesh_area structure.
* @param qstate: used to find mesh state.
*/
void (*detach_subs)(struct module_qstate* qstate);
/**
* Attach subquery.
* Creates it if it does not exist already.
* Keeps sub and super references correct.
* Updates stat items in mesh_area structure.
* Pass if it is priming query or not.
* return:
* o if error (malloc) happened.
* o need to initialise the new state (module init; it is a new state).
* so that the next run of the query with this module is successful.
* o no init needed, attachment successful.
*
* @param qstate: the state to find mesh state, and that wants to
* receive the results from the new subquery.
* @param qinfo: what to query for (copied).
* @param qflags: what flags to use (RD, CD flag or not).
* @param prime: if it is a (stub) priming query.
* @param valrec: validation lookup recursion, does not need validation
* @param newq: If the new subquery needs initialisation, it is
* returned, otherwise NULL is returned.
* @return: false on error, true if success (and init may be needed).
*/
int (*attach_sub)(struct module_qstate* qstate,
struct query_info* qinfo, uint16_t qflags, int prime,
int valrec, struct module_qstate** newq);
/**
* Kill newly attached sub. If attach_sub returns newq for
* initialisation, but that fails, then this routine will cleanup and
* delete the fresly created sub.
* @param newq: the new subquery that is no longer needed.
* It is removed.
*/
void (*kill_sub)(struct module_qstate* newq);
/**
* Detect if adding a dependency for qstate on name,type,class will
* create a dependency cycle.
* @param qstate: given mesh querystate.
* @param qinfo: query info for dependency.
* @param flags: query flags of dependency, RD/CD flags.
* @param prime: if dependency is a priming query or not.
* @param valrec: validation lookup recursion, does not need validation
* @return true if the name,type,class exists and the given
* qstate mesh exists as a dependency of that name. Thus
* if qstate becomes dependent on name,type,class then a
* cycle is created.
*/
int (*detect_cycle)(struct module_qstate* qstate,
struct query_info* qinfo, uint16_t flags, int prime,
int valrec);
/** region for temporary usage. May be cleared after operate() call. */
struct regional* scratch;
/** buffer for temporary usage. May be cleared after operate() call. */
struct sldns_buffer* scratch_buffer;
/** internal data for daemon - worker thread. */
struct worker* worker;
/** mesh area with query state dependencies */
struct mesh_area* mesh;
/** allocation service */
struct alloc_cache* alloc;
/** random table to generate random numbers */
struct ub_randstate* rnd;
/** time in seconds, converted to integer */
time_t* now;
/** time in microseconds. Relatively recent. */
struct timeval* now_tv;
/** is validation required for messages, controls client-facing
* validation status (AD bits) and servfails */
int need_to_validate;
/** trusted key storage; these are the configured keys, if not NULL,
* otherwise configured by validator. These are the trust anchors,
* and are not primed and ready for validation, but on the bright
* side, they are read only memory, thus no locks and fast. */
struct val_anchors* anchors;
/** negative cache, configured by the validator. if not NULL,
* contains NSEC record lookup trees. */
struct val_neg_cache* neg_cache;
/** the 5011-probe timer (if any) */
struct comm_timer* probe_timer;
/** Mapping of forwarding zones to targets.
* iterator forwarder information. per-thread, created by worker */
struct iter_forwards* fwds;
/**
* iterator forwarder information. per-thread, created by worker.
* The hints -- these aren't stored in the cache because they don't
* expire. The hints are always used to "prime" the cache. Note
* that both root hints and stub zone "hints" are stored in this
* data structure.
*/
struct iter_hints* hints;
/** module specific data. indexed by module id. */
void* modinfo[MAX_MODULE];
};
/**
* External visible states of the module state machine
* Modules may also have an internal state.
* Modules are supposed to run to completion or until blocked.
*/
enum module_ext_state {
/** initial state - new query */
module_state_initial = 0,
/** waiting for reply to outgoing network query */
module_wait_reply,
/** module is waiting for another module */
module_wait_module,
/** module is waiting for another module; that other is restarted */
module_restart_next,
/** module is waiting for sub-query */
module_wait_subquery,
/** module could not finish the query */
module_error,
/** module is finished with query */
module_finished
};
/**
* Events that happen to modules, that start or wakeup modules.
*/
enum module_ev {
/** new query */
module_event_new = 0,
/** query passed by other module */
module_event_pass,
/** reply inbound from server */
module_event_reply,
/** no reply, timeout or other error */
module_event_noreply,
/** reply is there, but capitalisation check failed */
module_event_capsfail,
/** next module is done, and its reply is awaiting you */
module_event_moddone,
/** error */
module_event_error
};
/**
* Linked list of sockaddrs
* May be allocated such that only 'len' bytes of addr exist for the structure.
*/
struct sock_list {
/** next in list */
struct sock_list* next;
/** length of addr */
socklen_t len;
/** sockaddr */
struct sockaddr_storage addr;
};
/**
* Module state, per query.
*/
struct module_qstate {
/** which query is being answered: name, type, class */
struct query_info qinfo;
/** flags uint16 from query */
uint16_t query_flags;
/** if this is a (stub or root) priming query (with hints) */
int is_priming;
/** if this is a validation recursion query that does not get
* validation itself */
int is_valrec;
/** comm_reply contains server replies */
struct comm_reply* reply;
/** the reply message, with message for client and calling module */
struct dns_msg* return_msg;
/** the rcode, in case of error, instead of a reply message */
int return_rcode;
/** origin of the reply (can be NULL from cache, list for cnames) */
struct sock_list* reply_origin;
/** IP blacklist for queries */
struct sock_list* blacklist;
/** region for this query. Cleared when query process finishes. */
struct regional* region;
/** failure reason information if val-log-level is high */
struct config_strlist* errinf;
/** which module is executing */
int curmod;
/** module states */
enum module_ext_state ext_state[MAX_MODULE];
/** module specific data for query. indexed by module id. */
void* minfo[MAX_MODULE];
/** environment for this query */
struct module_env* env;
/** mesh related information for this query */
struct mesh_state* mesh_info;
/** how many seconds before expiry is this prefetched (0 if not) */
time_t prefetch_leeway;
};
/**
* Module functionality block
*/
struct module_func_block {
/** text string name of module */
const char* name;
/**
* init the module. Called once for the global state.
* This is the place to apply settings from the config file.
* @param env: module environment.
* @param id: module id number.
* return: 0 on error
*/
int (*init)(struct module_env* env, int id);
/**
* de-init, delete, the module. Called once for the global state.
* @param env: module environment.
* @param id: module id number.
*/
void (*deinit)(struct module_env* env, int id);
/**
* accept a new query, or work further on existing query.
* Changes the qstate->ext_state to be correct on exit.
* @param ev: event that causes the module state machine to
* (re-)activate.
* @param qstate: the query state.
* Note that this method is not allowed to change the
* query state 'identity', that is query info, qflags,
* and priming status.
* Attach a subquery to get results to a different query.
* @param id: module id number that operate() is called on.
* @param outbound: if not NULL this event is due to the reply/timeout
* or error on this outbound query.
* @return: if at exit the ext_state is:
* o wait_module: next module is started. (with pass event).
* o error or finished: previous module is resumed.
* o otherwise it waits until that event happens (assumes
* the service routine to make subrequest or send message
* have been called.
*/
void (*operate)(struct module_qstate* qstate, enum module_ev event,
int id, struct outbound_entry* outbound);
/**
* inform super querystate about the results from this subquerystate.
* Is called when the querystate is finished. The method invoked is
* the one from the current module active in the super querystate.
* @param qstate: the query state that is finished.
* Examine return_rcode and return_reply in the qstate.
* @param id: module id for this module.
* This coincides with the current module for the super qstate.
* @param super: the super querystate that needs to be informed.
*/
void (*inform_super)(struct module_qstate* qstate, int id,
struct module_qstate* super);
/**
* clear module specific data
*/
void (*clear)(struct module_qstate* qstate, int id);
/**
* How much memory is the module specific data using.
* @param env: module environment.
* @param id: the module id.
* @return the number of bytes that are alloced.
*/
size_t (*get_mem)(struct module_env* env, int id);
};
/**
* Debug utility: module external qstate to string
* @param s: the state value.
* @return descriptive string.
*/
const char* strextstate(enum module_ext_state s);
/**
* Debug utility: module event to string
* @param e: the module event value.
* @return descriptive string.
*/
const char* strmodulevent(enum module_ev e);
#endif /* UTIL_MODULE_H */
