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Diffstat (limited to 'pjsip/include/pjsip/sip_resolve.h')
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diff --git a/pjsip/include/pjsip/sip_resolve.h b/pjsip/include/pjsip/sip_resolve.h new file mode 100644 index 0000000..6f578a1 --- /dev/null +++ b/pjsip/include/pjsip/sip_resolve.h @@ -0,0 +1,291 @@ +/* $Id: sip_resolve.h 3553 2011-05-05 06:14:19Z nanang $ */ +/* + * Copyright (C) 2008-2011 Teluu Inc. (http://www.teluu.com) + * Copyright (C) 2003-2008 Benny Prijono <benny@prijono.org> + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + */ +#ifndef __PJSIP_SIP_RESOLVE_H__ +#define __PJSIP_SIP_RESOLVE_H__ + +/** + * @file sip_resolve.h + * @brief + * This module contains the mechanism to resolve server address as specified by + * RFC 3263 - Locating SIP Servers + */ + +#include <pjsip/sip_types.h> +#include <pjlib-util/resolver.h> +#include <pj/sock.h> + +PJ_BEGIN_DECL + +/** + * @defgroup PJSIP_RESOLVE SIP SRV Server Resolution (RFC 3263 - Locating SIP Servers) + * @ingroup PJSIP_TRANSPORT + * @brief Framework to resolve SIP servers based on RFC 3263. + * @{ + * \section PJSIP_RESOLVE_FEATURES Features + * + * This is the SIP server resolution framework, which is modelled after + * RFC 3263 - Locating SIP Servers document. The SIP server resolution + * framework is asynchronous; callback will be called once the server + * address has been resolved (successfully or with errors). + * + * \subsection PJSIP_RESOLVE_CONFORMANT Conformance to RFC 3263 + * + * The SIP server resolution framework is modelled after RFC 3263 (Locating + * SIP Servers) document, and it provides a single function (#pjsip_resolve()) + * to resolve a domain into actual IP addresses of the servers, by querying + * DNS SRV record and DNS A record where necessary. + * + * The #pjsip_resolve() function performs the server resolution according + * to RFC 3263 with some additional fallback mechanisms, as follows: + * - if the target name is an IP address, the callback will be called + * immediately with the IP address. If port number was specified, this + * port number will be used, otherwise the default port number for the + * transport will be used (5060 for TCP/UDP, 5061 for TLS) if the transport + * is specified. If the transport is not specified, UDP with port number + * 5060 will be used. + * - if target name is not an IP address but it contains port number, + * then the target name is resolved with DNS A (or AAAA, when IPv6 is + * supported in the future) query, and the port is taken from the + * port number argument. The callback will be called once the DNS A + * resolution completes. If the DNS A resolution returns multiple IP + * addresses, these IP addresses will be returned to the caller. + * - if target name is not an IP address and port number is not specified, + * DNS SRV resolution will be performed for the specified name and + * transport type (or UDP when transport is not specified), + * then followed by DNS A (or AAAA, when IPv6 is supported) + * resolution for each target in the SRV record. If DNS SRV + * resolution returns error, DNS A (or AAAA) resolution will be + * performed for the original target (it is assumed that the target domain + * does not support SRV records). Upon successful completion, + * application callback will be called with each IP address of the + * target selected based on the load-balancing and fail-over criteria + * below. + * + * The above server resolution procedure differs from RFC 3263 in these + * regards: + * - currently #pjsip_resolve() doesn't support DNS NAPTR record. + * - if transport is not specified, it is assumed to be UDP (the proper + * behavior is to query the NAPTR record, but we don't support this + * yet). + * + * + * \subsection PJSIP_SIP_RESOLVE_FAILOVER_LOADBALANCE Load-Balancing and Fail-Over + * + * When multiple targets are returned in the DNS SRV response, server entries + * are selected based on the following rule (which is described in RFC 2782): + * - targets will be sorted based on the priority first. + * - for targets with the same priority, #pjsip_resolve() will select + * only one target according to its weight. To select this one target, + * the function associates running-sum for all targets, and generates + * a random number between zero and the total running-sum (inclusive). + * The target selected is the first target with running-sum greater than + * or equal to this random number. + * + * The above procedure will select one target for each priority, allowing + * application to fail-over to the next target when the previous target fails. + * These targets are returned in the #pjsip_server_addresses structure + * argument of the callback. + * + * \subsection PJSIP_SIP_RESOLVE_SIP_FEATURES SIP SRV Resolver Features + * + * Some features of the SIP resolver: + * - DNS SRV entries are returned on sorted order based on priority + * to allow failover to the next appropriate server. + * - The procedure in RFC 2782 is used to select server with the same + * priority to load-balance the servers load. + * - A single function (#pjsip_resolve()) performs all server resolution + * works, from resolving the SRV records to getting the actual IP addresses + * of the servers with DNS A (or AAAA) resolution. + * - When multiple DNS SRV records are returned, parallel DNS A (or AAAA) + * queries will be issued simultaneously. + * - The PJLIB-UTIL DNS resolver provides additional functionality such as + * response caching, query aggregation, parallel nameservers, fallback + * nameserver, etc., which will be described below. + * + * + * \subsection PJSIP_RESOLVE_DNS_FEATURES DNS Resolver Features + * + * The PJSIP server resolution framework uses PJLIB-UTIL DNS resolver engine + * for performing the asynchronous DNS request. The PJLIB-UTIL DNS resolver + * has some useful features, such as: + * - queries are asynchronous with configurable timeout, + * - query aggregation to combine multiple pending queries to the same + * DNS target into a single DNS request (to save message round-trip and + * processing), + * - response caching with TTL negotiated between the minimum TTL found in + * the response and the maximum TTL allowed in the configuration, + * - multiple nameservers, with active nameserver is selected from nameserver + * which provides the best response time, + * - fallback nameserver, with periodic detection of which name servers are + * active or down. + * - etc. + * + * Please consult PJLIB-UTIL DNS resolver documentation for more details. + * + * + * \section PJSIP_RESOLVE_USING Using the Resolver + * + * To maintain backward compatibility, the resolver MUST be enabled manually. + * With the default settings, the resolver WILL NOT perform DNS SRV resolution, + * as it will just resolve the name with standard pj_gethostbyname() function. + * + * Application can enable the SRV resolver by creating the PJLIB-UTIL DNS + * resolver with #pjsip_endpt_create_resolver(), configure the + * nameservers of the PJLIB-UTIL DNS resolver object by calling + * pj_dns_resolver_set_ns() function, and pass the DNS resolver object to + * #pjsip_resolver_set_resolver() function. + * + * Once the resolver is set, it will be used automatically by PJSIP everytime + * PJSIP needs to send SIP request/response messages. + * + * + * \section PJSIP_RESOLVE_REFERENCE Reference + * + * Reference: + * - RFC 2782: A DNS RR for specifying the location of services (DNS SRV) + * - RFC 3263: Locating SIP Servers + */ + +/** + * The server addresses returned by the resolver. + */ +typedef struct pjsip_server_addresses +{ + /** Number of address records. */ + unsigned count; + + /** Address records. */ + struct + { + /** Preferable transport to be used to contact this address. */ + pjsip_transport_type_e type; + + /** Server priority (the lower the higher the priority). */ + unsigned priority; + + /** Server weight (the higher the more load it can handle). */ + unsigned weight; + + /** The server's address. */ + pj_sockaddr addr; + + /** Address length. */ + int addr_len; + + } entry[PJSIP_MAX_RESOLVED_ADDRESSES]; + +} pjsip_server_addresses; + + +/** + * The type of callback function to be called when resolver finishes the job. + * + * @param status The status of the operation, which is zero on success. + * @param token The token that was associated with the job when application + * call the resolve function. + * @param addr The addresses resolved by the operation. + */ +typedef void pjsip_resolver_callback(pj_status_t status, + void *token, + const struct pjsip_server_addresses *addr); + +/** + * Create SIP resolver engine. Note that this function is normally called + * internally by pjsip_endpoint instance. + * + * @param pool Pool to allocate memory from. + * @param p_res Pointer to receive SIP resolver instance. + * + * @return PJ_SUCCESS when resolver can be successfully created. + */ +PJ_DECL(pj_status_t) pjsip_resolver_create(pj_pool_t *pool, + pjsip_resolver_t **p_res); + +/** + * Set the DNS resolver instance of the SIP resolver engine. Before the + * DNS resolver is set, the SIP resolver will use standard pj_gethostbyname() + * to resolve addresses. + * + * Note that application normally will use #pjsip_endpt_set_resolver() instead + * since it does not normally have access to the SIP resolver instance. + * + * @param res The SIP resolver engine. + * @param dns_res The DNS resolver instance to be used by the SIP resolver. + * This argument can be NULL to reset the internal DNS + * instance. + * + * @return PJ_SUCCESS on success, or the appropriate error code. + */ +PJ_DECL(pj_status_t) pjsip_resolver_set_resolver(pjsip_resolver_t *res, + pj_dns_resolver *dns_res); + + +/** + * Get the DNS resolver instance of the SIP resolver engine. + * + * Note that application normally will use #pjsip_endpt_get_resolver() instead + * since it does not normally have access to the SIP resolver instance. + * + * @param res The SIP resolver engine. + * + * @return The DNS resolver instance (may be NULL) + */ +PJ_DECL(pj_dns_resolver*) pjsip_resolver_get_resolver(pjsip_resolver_t *res); + +/** + * Destroy resolver engine. Note that this will also destroy the internal + * DNS resolver inside the engine. If application doesn't want the internal + * DNS resolver to be destroyed, it should set the internal DNS resolver + * to NULL before calling this function. + * + * Note that this function will normally called by the SIP endpoint instance + * when the SIP endpoint instance is destroyed. + * + * @param resolver The resolver. + */ +PJ_DECL(void) pjsip_resolver_destroy(pjsip_resolver_t *resolver); + +/** + * Asynchronously resolve a SIP target host or domain according to rule + * specified in RFC 3263 (Locating SIP Servers). When the resolving operation + * has completed, the callback will be called. + * + * Note that application normally will use #pjsip_endpt_resolve() instead + * since it does not normally have access to the SIP resolver instance. + * + * @param resolver The resolver engine. + * @param pool The pool to allocate resolver job. + * @param target The target specification to be resolved. + * @param token A user defined token to be passed back to callback function. + * @param cb The callback function. + */ +PJ_DECL(void) pjsip_resolve( pjsip_resolver_t *resolver, + pj_pool_t *pool, + const pjsip_host_info *target, + void *token, + pjsip_resolver_callback *cb); + +/** + * @} + */ + +PJ_END_DECL + +#endif /* __PJSIP_SIP_RESOLVE_H__ */ |