/* * unbound.h - unbound validating resolver public API * * 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 REGENTS 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 functions to resolve DNS queries and * validate the answers. Synchonously and asynchronously. * * Several ways to use this interface from an application wishing * to perform (validated) DNS lookups. * * All start with * ctx = ub_ctx_create(); * err = ub_ctx_add_ta(ctx, "..."); * err = ub_ctx_add_ta(ctx, "..."); * ... some lookups * ... call ub_ctx_delete(ctx); when you want to stop. * * Application not threaded. Blocking. * int err = ub_resolve(ctx, "www.example.com", ... * if(err) fprintf(stderr, "lookup error: %s\n", ub_strerror(err)); * ... use the answer * * Application not threaded. Non-blocking ('asynchronous'). * err = ub_resolve_async(ctx, "www.example.com", ... my_callback); * ... application resumes processing ... * ... and when either ub_poll(ctx) is true * ... or when the file descriptor ub_fd(ctx) is readable, * ... or whenever, the app calls ... * ub_process(ctx); * ... if no result is ready, the app resumes processing above, * ... or process() calls my_callback() with results. * * ... if the application has nothing more to do, wait for answer * ub_wait(ctx); * * Application threaded. Blocking. * Blocking, same as above. The current thread does the work. * Multiple threads can use the *same context*, each does work and uses * shared cache data from the context. * * Application threaded. Non-blocking ('asynchronous'). * ... setup threaded-asynchronous config option * err = ub_ctx_async(ctx, 1); * ... same as async for non-threaded * ... the callbacks are called in the thread that calls process(ctx) * * If no threading is compiled in, the above async example uses fork(2) to * create a process to perform the work. The forked process exits when the * calling process exits, or ctx_delete() is called. * Otherwise, for asynchronous with threading, a worker thread is created. * * The blocking calls use shared ctx-cache when threaded. Thus * ub_resolve() and ub_resolve_async() && ub_wait() are * not the same. The first makes the current thread do the work, setting * up buffers, etc, to perform the work (but using shared cache data). * The second calls another worker thread (or process) to perform the work. * And no buffers need to be set up, but a context-switch happens. */ #ifndef _UB_UNBOUND_H #define _UB_UNBOUND_H #ifdef __cplusplus extern "C" { #endif /** * The validation context is created to hold the resolver status, * validation keys and a small cache (containing messages, rrsets, * roundtrip times, trusted keys, lameness information). * * Its contents are internally defined. */ struct ub_ctx; /** * The validation and resolution results. * Allocated by the resolver, and need to be freed by the application * with ub_resolve_free(). */ struct ub_result { /** The original question, name text string. */ char* qname; /** the type asked for */ int qtype; /** the class asked for */ int qclass; /** * a list of network order DNS rdata items, terminated with a * NULL pointer, so that data[0] is the first result entry, * data[1] the second, and the last entry is NULL. * If there was no data, data[0] is NULL. */ char** data; /** the length in bytes of the data items, len[i] for data[i] */ int* len; /** * canonical name for the result (the final cname). * zero terminated string. * May be NULL if no canonical name exists. */ char* canonname; /** * DNS RCODE for the result. May contain additional error code if * there was no data due to an error. 0 (NOERROR) if okay. */ int rcode; /** * The DNS answer packet. Network formatted. Can contain DNSSEC types. */ void* answer_packet; /** length of the answer packet in octets. */ int answer_len; /** * If there is any data, this is true. * If false, there was no data (nxdomain may be true, rcode can be set). */ int havedata; /** * If there was no data, and the domain did not exist, this is true. * If it is false, and there was no data, then the domain name * is purported to exist, but the requested data type is not available. */ int nxdomain; /** * True, if the result is validated securely. * False, if validation failed or domain queried has no security info. * * It is possible to get a result with no data (havedata is false), * and secure is true. This means that the non-existance of the data * was cryptographically proven (with signatures). */ int secure; /** * If the result was not secure (secure==0), and this result is due * to a security failure, bogus is true. * This means the data has been actively tampered with, signatures * failed, expected signatures were not present, timestamps on * signatures were out of date and so on. * * If !secure and !bogus, this can happen if the data is not secure * because security is disabled for that domain name. * This means the data is from a domain where data is not signed. */ int bogus; /** * If the result is bogus this contains a string (zero terminated) * that describes the failure. There may be other errors as well * as the one described, the description may not be perfectly accurate. * Is NULL if the result is not bogus. */ char* why_bogus; /** * TTL for the result, in seconds. If the security is bogus, then * you also cannot trust this value. */ int ttl; }; /** * Callback for results of async queries. * The readable function definition looks like: * void my_callback(void* my_arg, int err, struct ub_result* result); * It is called with * void* my_arg: your pointer to a (struct of) data of your choice, * or NULL. * int err: if 0 all is OK, otherwise an error occured and no results * are forthcoming. * struct result: pointer to more detailed result structure. * This structure is allocated on the heap and needs to be * freed with ub_resolve_free(result); */ typedef void (*ub_callback_t)(void*, int, struct ub_result*); /** * Create a resolving and validation context. * The information from /etc/resolv.conf and /etc/hosts is not utilised by * default. Use ub_ctx_resolvconf and ub_ctx_hosts to read them. * @return a new context. default initialisation. * returns NULL on error. */ struct ub_ctx* ub_ctx_create(void); /** * Destroy a validation context and free all its resources. * Outstanding async queries are killed and callbacks are not called for them. * @param ctx: context to delete. */ void ub_ctx_delete(struct ub_ctx* ctx); /** * Set an option for the context. * @param ctx: context. * @param opt: option name from the unbound.conf config file format. * (not all settings applicable). The name includes the trailing ':' * for example ub_ctx_set_option(ctx, "logfile:", "mylog.txt"); * This is a power-users interface that lets you specify all sorts * of options. * For some specific options, such as adding trust anchors, special * routines exist. * @param val: value of the option. * @return: 0 if OK, else error. */ int ub_ctx_set_option(struct ub_ctx* ctx, const char* opt, const char* val); /** * Get an option from the context. * @param ctx: context. * @param opt: option name from the unbound.conf config file format. * (not all settings applicable). The name excludes the trailing ':' * for example ub_ctx_get_option(ctx, "logfile", &result); * This is a power-users interface that lets you specify all sorts * of options. * @param str: the string is malloced and returned here. NULL on error. * The caller must free() the string. In cases with multiple * entries (auto-trust-anchor-file), a newline delimited list is * returned in the string. * @return 0 if OK else an error code (malloc failure, syntax error). */ int ub_ctx_get_option(struct ub_ctx* ctx, const char* opt, char** str); /** * setup configuration for the given context. * @param ctx: context. * @param fname: unbound config file (not all settings applicable). * This is a power-users interface that lets you specify all sorts * of options. * For some specific options, such as adding trust anchors, special * routines exist. * @return: 0 if OK, else error. */ int ub_ctx_config(struct ub_ctx* ctx, const char* fname); /** * Set machine to forward DNS queries to, the caching resolver to use. * IP4 or IP6 address. Forwards all DNS requests to that machine, which * is expected to run a recursive resolver. If the proxy is not * DNSSEC-capable, validation may fail. Can be called several times, in * that case the addresses are used as backup servers. * * To read the list of nameservers from /etc/resolv.conf (from DHCP or so), * use the call ub_ctx_resolvconf. * * @param ctx: context. * At this time it is only possible to set configuration before the * first resolve is done. * @param addr: address, IP4 or IP6 in string format. * If the addr is NULL, forwarding is disabled. * @return 0 if OK, else error. */ int ub_ctx_set_fwd(struct ub_ctx* ctx, const char* addr); /** * Read list of nameservers to use from the filename given. * Usually "/etc/resolv.conf". Uses those nameservers as caching proxies. * If they do not support DNSSEC, validation may fail. * * Only nameservers are picked up, the searchdomain, ndots and other * settings from resolv.conf(5) are ignored. * * @param ctx: context. * At this time it is only possible to set configuration before the * first resolve is done. * @param fname: file name string. If NULL "/etc/resolv.conf" is used. * @return 0 if OK, else error. */ int ub_ctx_resolvconf(struct ub_ctx* ctx, const char* fname); /** * Read list of hosts from the filename given. * Usually "/etc/hosts". * These addresses are not flagged as DNSSEC secure when queried for. * * @param ctx: context. * At this time it is only possible to set configuration before the * first resolve is done. * @param fname: file name string. If NULL "/etc/hosts" is used. * @return 0 if OK, else error. */ int ub_ctx_hosts(struct ub_ctx* ctx, const char* fname); /** * Add a trust anchor to the given context. * The trust anchor is a string, on one line, that holds a valid DNSKEY or * DS RR. * @param ctx: context. * At this time it is only possible to add trusted keys before the * first resolve is done. * @param ta: string, with zone-format RR on one line. * [domainname] [TTL optional] [type] [class optional] [rdata contents] * @return 0 if OK, else error. */ int ub_ctx_add_ta(struct ub_ctx* ctx, const char* ta); /** * Add trust anchors to the given context. * Pass name of a file with DS and DNSKEY records (like from dig or drill). * @param ctx: context. * At this time it is only possible to add trusted keys before the * first resolve is done. * @param fname: filename of file with keyfile with trust anchors. * @return 0 if OK, else error. */ int ub_ctx_add_ta_file(struct ub_ctx* ctx, const char* fname); /** * Add trust anchors to the given context. * Pass the name of a bind-style config file with trusted-keys{}. * @param ctx: context. * At this time it is only possible to add trusted keys before the * first resolve is done. * @param fname: filename of file with bind-style config entries with trust * anchors. * @return 0 if OK, else error. */ int ub_ctx_trustedkeys(struct ub_ctx* ctx, const char* fname); /** * Set debug output (and error output) to the specified stream. * Pass NULL to disable. Default is stderr. * @param ctx: context. * @param out: FILE* out file stream to log to. * Type void* to avoid stdio dependency of this header file. * @return 0 if OK, else error. */ int ub_ctx_debugout(struct ub_ctx* ctx, void* out); /** * Set debug verbosity for the context * Output is directed to stderr. * @param ctx: context. * @param d: debug level, 0 is off, 1 is very minimal, 2 is detailed, * and 3 is lots. * @return 0 if OK, else error. */ int ub_ctx_debuglevel(struct ub_ctx* ctx, int d); /** * Set a context behaviour for asynchronous action. * @param ctx: context. * @param dothread: if true, enables threading and a call to resolve_async() * creates a thread to handle work in the background. * If false, a process is forked to handle work in the background. * Changes to this setting after async() calls have been made have * no effect (delete and re-create the context to change). * @return 0 if OK, else error. */ int ub_ctx_async(struct ub_ctx* ctx, int dothread); /** * Poll a context to see if it has any new results * Do not poll in a loop, instead extract the fd below to poll for readiness, * and then check, or wait using the wait routine. * @param ctx: context. * @return: 0 if nothing to read, or nonzero if a result is available. * If nonzero, call ctx_process() to do callbacks. */ int ub_poll(struct ub_ctx* ctx); /** * Wait for a context to finish with results. Calls ub_process() after * the wait for you. After the wait, there are no more outstanding * asynchronous queries. * @param ctx: context. * @return: 0 if OK, else error. */ int ub_wait(struct ub_ctx* ctx); /** * Get file descriptor. Wait for it to become readable, at this point * answers are returned from the asynchronous validating resolver. * Then call the ub_process to continue processing. * This routine works immediately after context creation, the fd * does not change. * @param ctx: context. * @return: -1 on error, or file descriptor to use select(2) with. */ int ub_fd(struct ub_ctx* ctx); /** * Call this routine to continue processing results from the validating * resolver (when the fd becomes readable). * Will perform necessary callbacks. * @param ctx: context * @return: 0 if OK, else error. */ int ub_process(struct ub_ctx* ctx); /** * Perform resolution and validation of the target name. * @param ctx: context. * The context is finalized, and can no longer accept config changes. * @param name: domain name in text format (a zero terminated text string). * @param rrtype: type of RR in host order, 1 is A (address). * @param rrclass: class of RR in host order, 1 is IN (for internet). * @param result: the result data is returned in a newly allocated result * structure. May be NULL on return, return value is set to an error * in that case (out of memory). * @return 0 if OK, else error. */ int ub_resolve(struct ub_ctx* ctx, const char* name, int rrtype, int rrclass, struct ub_result** result); /** * Perform resolution and validation of the target name. * Asynchronous, after a while, the callback will be called with your * data and the result. * @param ctx: context. * If no thread or process has been created yet to perform the * work in the background, it is created now. * The context is finalized, and can no longer accept config changes. * @param name: domain name in text format (a string). * @param rrtype: type of RR in host order, 1 is A. * @param rrclass: class of RR in host order, 1 is IN (for internet). * @param mydata: this data is your own data (you can pass NULL), * and is passed on to the callback function. * @param callback: this is called on completion of the resolution. * It is called as: * void callback(void* mydata, int err, struct ub_result* result) * with mydata: the same as passed here, you may pass NULL, * with err: is 0 when a result has been found. * with result: a newly allocated result structure. * The result may be NULL, in that case err is set. * * If an error happens during processing, your callback will be called * with error set to a nonzero value (and result==NULL). * @param async_id: if you pass a non-NULL value, an identifier number is * returned for the query as it is in progress. It can be used to * cancel the query. * @return 0 if OK, else error. */ int ub_resolve_async(struct ub_ctx* ctx, const char* name, int rrtype, int rrclass, void* mydata, ub_callback_t callback, int* async_id); /** * Cancel an async query in progress. * Its callback will not be called. * * @param ctx: context. * @param async_id: which query to cancel. * @return 0 if OK, else error. * This routine can return an error if the async_id passed does not exist * or has already been delivered. If another thread is processing results * at the same time, the result may be delivered at the same time and the * cancel fails with an error. Also the cancel can fail due to a system * error, no memory or socket failures. */ int ub_cancel(struct ub_ctx* ctx, int async_id); /** * Free storage associated with a result structure. * @param result: to free */ void ub_resolve_free(struct ub_result* result); /** * Convert error value to a human readable string. * @param err: error code from one of the ub_val* functions. * @return pointer to constant text string, zero terminated. */ const char* ub_strerror(int err); /** * Debug routine. Print the local zone information to debug output. * @param ctx: context. Is finalized by the routine. * @return 0 if OK, else error. */ int ub_ctx_print_local_zones(struct ub_ctx* ctx); /** * Add a new zone with the zonetype to the local authority info of the * library. * @param ctx: context. Is finalized by the routine. * @param zone_name: name of the zone in text, "example.com" * If it already exists, the type is updated. * @param zone_type: type of the zone (like for unbound.conf) in text. * @return 0 if OK, else error. */ int ub_ctx_zone_add(struct ub_ctx* ctx, char *zone_name, char *zone_type); /** * Remove zone from local authority info of the library. * @param ctx: context. Is finalized by the routine. * @param zone_name: name of the zone in text, "example.com" * If it does not exist, nothing happens. * @return 0 if OK, else error. */ int ub_ctx_zone_remove(struct ub_ctx* ctx, char *zone_name); /** * Add localdata to the library local authority info. * Similar to local-data config statement. * @param ctx: context. Is finalized by the routine. * @param data: the resource record in text format, for example * "www.example.com IN A 127.0.0.1" * @return 0 if OK, else error. */ int ub_ctx_data_add(struct ub_ctx* ctx, char *data); /** * Remove localdata from the library local authority info. * @param ctx: context. Is finalized by the routine. * @param data: the name to delete all data from, like "www.example.com". * @return 0 if OK, else error. */ int ub_ctx_data_remove(struct ub_ctx* ctx, char *data); /** * Get a version string from the libunbound implementation. * @return a static constant string with the version number. */ const char* ub_version(void); #ifdef __cplusplus } #endif #endif /* _UB_UNBOUND_H */