srv.c

   1 /*
   2  * Asterisk -- An open source telephony toolkit.
   3  *
   4  * Copyright (C) 1999 - 2005, Digium, Inc.
   5  *
   6  * Mark Spencer <markster@digium.com>
   7  *
   8  * Funding provided by nic.at
   9  *
  10  * See http://www.asterisk.org for more information about
  11  * the Asterisk project. Please do not directly contact
  12  * any of the maintainers of this project for assistance;
  13  * the project provides a web site, mailing lists and IRC
  14  * channels for your use.
  15  *
  16  * This program is free software, distributed under the terms of
  17  * the GNU General Public License Version 2. See the LICENSE file
  18  * at the top of the source tree.
  19  */
  20
  21 /*! \file
  22  *
  23  * \brief DNS SRV Record Lookup Support for Asterisk
  24  *
  25  * \author Mark Spencer <markster@digium.com>
  26  *
  27  * \arg See also \ref AstENUM
  28  *
  29  * \note Funding provided by nic.at
  30  */
  31
  32 #include "asterisk.h"
  33
  34 ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
  35
  36 #include <sys/types.h>
  37 #include <netinet/in.h>
  38 #include <arpa/nameser.h>
  39 #if __APPLE_CC__ >= 1495
  40 #include <arpa/nameser_compat.h>
  41 #endif
  42 #include <resolv.h>
  43 #include <stdio.h>
  44 #include <string.h>
  45 #include <unistd.h>
  46
  47 #include "asterisk/channel.h"
  48 #include "asterisk/logger.h"
  49 #include "asterisk/srv.h"
  50 #include "asterisk/dns.h"
  51 #include "asterisk/options.h"
  52 #include "asterisk/utils.h"
  53
  54 #ifdef __APPLE__
  55 #undef T_SRV
  56 #define T_SRV 33
  57 #endif
  58
  59 struct srv {
  60         unsigned short priority;
  61         unsigned short weight;
  62         unsigned short portnum;
  63 } __attribute__ ((__packed__));
  64
  65 static int parse_srv(char *host, int hostlen, int *portno, unsigned char *answer, int len, unsigned char *msg)
  66 {
  67         int res = 0;
  68         struct srv *srv = (struct srv *)answer;
  69         char repl[256] = "";
  70
  71         if (len < sizeof(struct srv)) {
  72                 printf("Length too short\n");
  73                 return -1;
  74         }
  75         answer += sizeof(struct srv);
  76         len -= sizeof(struct srv);
  77
  78         if ((res = dn_expand(msg, answer + len, answer, repl, sizeof(repl) - 1)) < 0) {
  79                 ast_log(LOG_WARNING, "Failed to expand hostname\n");
  80                 return -1;
  81         }
  82         if (res && strcmp(repl, ".")) {
  83                 if (option_verbose > 3)
  84                         ast_verbose( VERBOSE_PREFIX_3 "parse_srv: SRV mapped to host %s, port %d\n", repl, ntohs(srv->portnum));
  85                 if (host) {
  86                         ast_copy_string(host, repl, hostlen);
  87                         host[hostlen-1] = '\0';
  88                 }
  89                 if (portno)
  90                         *portno = ntohs(srv->portnum);
  91                 return 0;
  92         }
  93         return -1;
  94 }
  95
  96 struct srv_context {
  97         char *host;
  98         int hostlen;
  99         int *port;
 100 };
 101
 102 static int srv_callback(void *context, unsigned char *answer, int len, unsigned char *fullanswer)
 103 {
 104         struct srv_context *c = (struct srv_context *)context;
 105
 106         if (parse_srv(c->host, c->hostlen, c->port, answer, len, fullanswer)) {
 107                 ast_log(LOG_WARNING, "Failed to parse srv\n");
 108                 return -1;
 109         }
 110
 111         if (!ast_strlen_zero(c->host))
 112                 return 1;
 113
 114         return 0;
 115 }
 116
 117 int ast_get_srv(struct ast_channel *chan, char *host, int hostlen, int *port, const char *service)
 118 {
 119         struct srv_context context;
 120         int ret;
 121
 122         context.host = host;
 123         context.hostlen = hostlen;
 124         context.port = port;
 125
 126         if (chan && ast_autoservice_start(chan) < 0)
 127                 return -1;
 128
 129         ret = ast_search_dns(&context, service, C_IN, T_SRV, srv_callback);
 130
 131         if (chan)
 132                 ret |= ast_autoservice_stop(chan);
 133
 134         if (ret <= 0) {
 135                 host[0] = '\0';
 136                 *port = -1;
 137                 return ret;
 138         }
 139         return ret;
 140 }