1 /*
2 * This file is part of the Sofia-SIP package
3 *
4 * Copyright (C) 2006 Nokia Corporation.
5 *
6 * Contact: Pekka Pessi <pekka.pessi@nokia.com>
7 *
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public License
10 * as published by the Free Software Foundation; either version 2.1 of
11 * the License, or (at your option) any later version.
12 *
13 * This library is distributed in the hope that it will be useful, but
14 * WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with this library; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
21 * 02110-1301 USA
22 *
23 */
24
25 /**@internal
26 * @file stun_dns.c
27 * @brief Functins to discover STUN server address using DNS-SRV.
28 *
29 * Refs:
30 * - RFC3489/3489bis
31 * - RFC2782
32 *
33 * @author Kai Vehmanen <kai.vehmanen@nokia.com>
34 */
35
36 #include "config.h"
37
38 #define STUN_SRV_SERVICE_TCP "_stun._tcp"
39 #define STUN_SRV_SERVICE_UDP "_stun._udp"
40
41 #include <sofia-sip/stun.h>
42 #include <sofia-sip/su.h>
43 #include <sofia-sip/su_alloc.h>
44 #include <sofia-sip/su_wait.h>
45 #define SRES_CONTEXT_T stun_dns_lookup_t
46 #include <sofia-sip/sresolv.h>
47
48 #if HAVE_FUNC
49 #elif HAVE_FUNCTION
50 #define __func__ __FUNCTION__
51 #else
52 static char const __func__[] = "stun_dns";
53 #endif
54
55 #include "stun_internal.h"
56
57 #include <string.h>
58
59 struct stun_dns_lookup_s {
60 su_home_t stun_home[1];
61 su_root_t *stun_root;
62 stun_magic_t *stun_magic;
63 sres_resolver_t *stun_sres;
64 su_socket_t stun_socket;
65 stun_dns_lookup_f stun_cb;
66 char *stun_tcp_target;
67 char *stun_udp_target;
68 uint16_t stun_tcp_port;
69 uint16_t stun_udp_port;
70 unsigned stun_state:2; /**< bit0:udp, bit1:tcp */
71 };
72
73 enum stun_dns_state {
74 stun_dns_udp = 1,
75 stun_dns_tls = 2,
76 stun_dns_done = stun_dns_udp | stun_dns_tls
77 };
78
79 /**
80 * Internal callback used for gathering DNS replies.
81 */
priv_sres_cb(stun_dns_lookup_t * self,sres_query_t * q,sres_record_t ** answer)82 static void priv_sres_cb(stun_dns_lookup_t *self,
83 sres_query_t *q,
84 sres_record_t **answer)
85 {
86 int i;
87
88 sres_sort_answers(self->stun_sres, answer);
89
90 /* note: picks the first ones (sort puts records with most
91 * weight at start */
92
93 for (i = 0; answer && answer[i] != NULL; i++) {
94 sres_srv_record_t *rr = (sres_srv_record_t *) answer[i]->sr_srv;
95 if (rr && rr->srv_record && rr->srv_record->r_type == sres_type_srv) {
96 const char *tcp_name = STUN_SRV_SERVICE_TCP;
97 const char *udp_name = STUN_SRV_SERVICE_UDP;
98 if ((self->stun_state & stun_dns_tls) == 0 &&
99 strncmp(rr->srv_record->r_name, tcp_name, strlen(tcp_name)) == 0) {
100 self->stun_tcp_target = su_strdup(self->stun_home, rr->srv_target);
101 self->stun_tcp_port = rr->srv_port;
102 self->stun_state |= stun_dns_tls;
103 SU_DEBUG_5(("%s: stun (tcp) for domain %s is at %s:%u.\n",
104 __func__, rr->srv_record->r_name, self->stun_tcp_target, self->stun_tcp_port));
105 }
106 else if ((self->stun_state & stun_dns_udp) == 0 &&
107 strncmp(rr->srv_record->r_name, udp_name, strlen(udp_name)) == 0) {
108 self->stun_udp_target = su_strdup(self->stun_home, rr->srv_target);
109 self->stun_udp_port = rr->srv_port;
110 self->stun_state |= stun_dns_udp;
111 SU_DEBUG_5(("%s: stun (udp) for domain %s is at %s:%u.\n",
112 __func__, rr->srv_record->r_name, self->stun_udp_target, self->stun_udp_port));
113 }
114 }
115 }
116
117 if (self->stun_state == stun_dns_done) {
118 self->stun_cb(self, self->stun_magic);
119
120 sres_resolver_timer(self->stun_sres, -1);
121 }
122
123 sres_free_answers(self->stun_sres, answer);
124 }
125
126 /**
127 * Performs a DNS-SRV check for STUN 'stun' (tcp) and
128 * 'stun' (udp) services for 'domain'.
129 *
130 * The result will be delivered asynchronously in the
131 * 'func' callback. 'root' will be used as the event loop.
132 */
stun_dns_lookup(stun_magic_t * magic,su_root_t * root,stun_dns_lookup_f func,const char * domain)133 stun_dns_lookup_t *stun_dns_lookup(stun_magic_t *magic,
134 su_root_t *root,
135 stun_dns_lookup_f func,
136 const char *domain)
137 {
138 stun_dns_lookup_t *self;
139 sres_query_t *query;
140
141 if (!domain ||
142 strlen(domain) + strlen(STUN_SRV_SERVICE_UDP ".") + 1>= SRES_MAXDNAME)
143 return NULL;
144
145 self = su_home_new(sizeof(stun_dns_lookup_t));
146
147 /* see nta.c:outgoing_answer_srv() */
148 self->stun_magic = magic;
149 self->stun_cb = func;
150 self->stun_root = root;
151 self->stun_sres = sres_resolver_create(root, NULL, TAG_END());
152 if (self->stun_sres) {
153 char srvname[SRES_MAXDNAME + 1];
154
155 snprintf(srvname, sizeof srvname, "%s.%s", STUN_SRV_SERVICE_UDP, domain);
156
157 query = sres_query(self->stun_sres, priv_sres_cb, self,
158 sres_type_srv,
159 srvname);
160
161 snprintf(srvname, sizeof srvname, "%s.%s", STUN_SRV_SERVICE_TCP, domain);
162
163 query = sres_query(self->stun_sres, priv_sres_cb, self,
164 sres_type_srv,
165 srvname);
166 if (query) {
167 /* TODO Just so compiler doesn't give error */
168 }
169 }
170 else {
171 su_free(NULL, self), self = NULL;
172 }
173
174 return self;
175 }
176
177 /**
178 * Destroys the 'self' object created by stun_dns_lookup_destroy().
179 */
stun_dns_lookup_destroy(stun_dns_lookup_t * self)180 void stun_dns_lookup_destroy(stun_dns_lookup_t *self)
181 {
182 if (self->stun_sres)
183 sres_resolver_destroy(self->stun_sres);
184
185 su_home_unref(self->stun_home);
186 }
187
188 /**
189 * Fetches the results of a completed STUN DNS-SRV lookup
190 * for "_stun._udp" service (RFC3489/3489bis).
191 *
192 * @param self context pointer
193 * @param target location where to stored the 'target'
194 * SRV field for stun service
195 * @param port location where to store port number
196 *
197 * @return 0 on success, non-zero otherwise
198 */
stun_dns_lookup_udp_addr(stun_dns_lookup_t * self,const char ** target,uint16_t * port)199 int stun_dns_lookup_udp_addr(stun_dns_lookup_t *self, const char **target, uint16_t *port)
200 {
201 int result = -1;
202 if (self->stun_state == stun_dns_done) {
203 if (target) *target = self->stun_udp_target;
204 if (port) *port = self->stun_udp_port;
205 result = 0;
206 }
207
208 return result;
209 }
210
211 /**
212 * Fetches the results of a completed STUN DNS-SRV lookup
213 * for "_stun._tcp" service (RFC3489).
214 *
215 * @param self context pointer
216 * @param target location where to stored the 'target'
217 * SRV field for stun service
218 * @param port location where to store port number
219 *
220 * @return 0 on success, non-zero otherwise
221 */
stun_dns_lookup_tcp_addr(stun_dns_lookup_t * self,const char ** target,uint16_t * port)222 int stun_dns_lookup_tcp_addr(stun_dns_lookup_t *self, const char **target, uint16_t *port)
223 {
224 int result = -1;
225 if (self->stun_state == stun_dns_done) {
226 if (target) *target = self->stun_tcp_target;
227 if (port) *port = self->stun_tcp_port;
228 result = 0;
229 }
230
231 return result;
232 }
233
234 /**
235 * Fetches the results of a completed STUN DNS-SRV lookup
236 * for "_stun._udp" service (3489bis, "Short-Term Password").
237 *
238 * @param self context pointer
239 * @param target location where to stored the 'target'
240 * SRV field for stun service
241 * @param port location where to store port number
242 *
243 * @return 0 on success, non-zero otherwise
244 */
stun_dns_lookup_stp_addr(stun_dns_lookup_t * self,const char ** target,uint16_t * port)245 int stun_dns_lookup_stp_addr(stun_dns_lookup_t *self, const char **target, uint16_t *port)
246 {
247 /* XXX: not implemented */
248 return -1;
249 }
250
251
252