Mon May 14 04:43:01 2007

Asterisk developer's documentation


srv.c

Go to the documentation of this file.
00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2005, Digium, Inc.
00005  *
00006  * Mark Spencer <markster@digium.com>
00007  *
00008  * Funding provided by nic.at
00009  *
00010  * See http://www.asterisk.org for more information about
00011  * the Asterisk project. Please do not directly contact
00012  * any of the maintainers of this project for assistance;
00013  * the project provides a web site, mailing lists and IRC
00014  * channels for your use.
00015  *
00016  * This program is free software, distributed under the terms of
00017  * the GNU General Public License Version 2. See the LICENSE file
00018  * at the top of the source tree.
00019  */
00020 
00021 /*! \file
00022  *
00023  * \brief DNS SRV Record Lookup Support for Asterisk
00024  *
00025  * \author Mark Spencer <markster@digium.com>
00026  * 
00027  * \arg See also \ref AstENUM
00028  *
00029  * \note Funding provided by nic.at
00030  */
00031 
00032 #include "asterisk.h"
00033 
00034 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
00035 
00036 #include <sys/types.h>
00037 #include <netinet/in.h>
00038 #include <arpa/nameser.h>
00039 #if __APPLE_CC__ >= 1495
00040 #include <arpa/nameser_compat.h>
00041 #endif
00042 #include <resolv.h>
00043 #include <stdio.h>
00044 #include <string.h>
00045 #include <unistd.h>
00046 
00047 #include "asterisk/channel.h"
00048 #include "asterisk/logger.h"
00049 #include "asterisk/srv.h"
00050 #include "asterisk/dns.h"
00051 #include "asterisk/options.h"
00052 #include "asterisk/utils.h"
00053 
00054 #ifdef __APPLE__
00055 #undef T_SRV
00056 #define T_SRV 33
00057 #endif
00058 
00059 struct srv {
00060    unsigned short priority;
00061    unsigned short weight;
00062    unsigned short portnum;
00063 } __attribute__ ((__packed__));
00064 
00065 static int parse_srv(char *host, int hostlen, int *portno, unsigned char *answer, int len, unsigned char *msg)
00066 {
00067    int res = 0;
00068    struct srv *srv = (struct srv *)answer;
00069    char repl[256] = "";
00070 
00071    if (len < sizeof(struct srv)) {
00072       printf("Length too short\n");
00073       return -1;
00074    }
00075    answer += sizeof(struct srv);
00076    len -= sizeof(struct srv);
00077 
00078    if ((res = dn_expand(msg, answer + len, answer, repl, sizeof(repl) - 1)) < 0) {
00079       ast_log(LOG_WARNING, "Failed to expand hostname\n");
00080       return -1;
00081    }
00082    if (res && strcmp(repl, ".")) {
00083       if (option_verbose > 3)
00084          ast_verbose( VERBOSE_PREFIX_3 "parse_srv: SRV mapped to host %s, port %d\n", repl, ntohs(srv->portnum));
00085       if (host) {
00086          ast_copy_string(host, repl, hostlen);
00087          host[hostlen-1] = '\0';
00088       }
00089       if (portno)
00090          *portno = ntohs(srv->portnum);
00091       return 0;
00092    }
00093    return -1;
00094 }
00095 
00096 struct srv_context {
00097    char *host;
00098    int hostlen;
00099    int *port;
00100 };
00101 
00102 static int srv_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer)
00103 {
00104    struct srv_context *c = (struct srv_context *)context;
00105 
00106    if (parse_srv(c->host, c->hostlen, c->port, answer, len, fullanswer)) {
00107       ast_log(LOG_WARNING, "Failed to parse srv\n");
00108       return -1;
00109    }
00110 
00111    if (!ast_strlen_zero(c->host))
00112       return 1;
00113 
00114    return 0;
00115 }
00116 
00117 int ast_get_srv(struct ast_channel *chan, char *host, int hostlen, int *port, const char *service)
00118 {
00119    struct srv_context context;
00120    int ret;
00121 
00122    context.host = host;
00123    context.hostlen = hostlen;
00124    context.port = port;
00125 
00126    if (chan && ast_autoservice_start(chan) < 0)
00127       return -1;
00128 
00129    ret = ast_search_dns(&context, service, C_IN, T_SRV, srv_callback);
00130 
00131    if (chan)
00132       ret |= ast_autoservice_stop(chan);
00133 
00134    if (ret <= 0) {
00135       host[0] = '\0';
00136       *port = -1;
00137       return ret;
00138    }
00139    return ret;
00140 }

Generated on Mon May 14 04:43:01 2007 for Asterisk - the Open Source PBX by  doxygen 1.5.1