1 /*
2 * Copyright (C) 2008 The Android Open Source Project
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * * Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * * Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in
12 * the documentation and/or other materials provided with the
13 * distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28 #include <sys/cdefs.h>
29 #include <sys/types.h>
30 #include <arpa/inet.h>
31 #include <arpa/nameser.h>
32 #include <netdb.h>
33 #include "resolv_private.h"
34 #include "resolv_cache.h"
35 #include <pthread.h>
36 #include <stdlib.h>
37 #include <string.h>
38
39 #define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
40 #include <sys/_system_properties.h>
41
42 /* Set to 1 to enable debug traces */
43 #define DEBUG 0
44
45 #if DEBUG
46 # include "private/libc_logging.h"
47 # include <unistd.h> /* for gettid() */
48 # define D(...) __libc_format_log(ANDROID_LOG_DEBUG,"libc", __VA_ARGS__)
49 #else
50 # define D(...) do{}while(0)
51 #endif
52
53 typedef struct {
54 int _h_errno;
55 // TODO: Have one __res_state per network so we don't have to repopulate frequently.
56 struct __res_state _nres[1];
57 unsigned _serial;
58 struct prop_info* _pi;
59 struct res_static _rstatic[1];
60 } _res_thread;
61
62 static _res_thread*
_res_thread_alloc(void)63 _res_thread_alloc(void)
64 {
65 _res_thread* rt = calloc(1, sizeof(*rt));
66
67 if (rt) {
68 rt->_h_errno = 0;
69 /* Special system property which tracks any changes to 'net.*'. */
70 rt->_serial = 0;
71 rt->_pi = (struct prop_info*) __system_property_find("net.change");
72 if (rt->_pi) {
73 rt->_serial = __system_property_serial(rt->_pi);
74 }
75 memset(rt->_rstatic, 0, sizeof rt->_rstatic);
76 }
77 return rt;
78 }
79
80 static void
_res_static_done(res_static rs)81 _res_static_done( res_static rs )
82 {
83 /* fortunately, there is nothing to do here, since the
84 * points in h_addr_ptrs and host_aliases should all
85 * point to 'hostbuf'
86 */
87 if (rs->hostf) { /* should not happen in theory, but just be safe */
88 fclose(rs->hostf);
89 rs->hostf = NULL;
90 }
91 free(rs->servent.s_aliases);
92 }
93
94 static void
_res_thread_free(void * _rt)95 _res_thread_free( void* _rt )
96 {
97 _res_thread* rt = _rt;
98
99 D("%s: rt=%p for thread=%d", __FUNCTION__, rt, gettid());
100
101 _res_static_done(rt->_rstatic);
102 res_ndestroy(rt->_nres);
103 free(rt);
104 }
105
106 static pthread_key_t _res_key;
107
__res_key_init()108 __attribute__((constructor)) static void __res_key_init() {
109 pthread_key_create(&_res_key, _res_thread_free);
110 }
111
112 static _res_thread*
_res_thread_get(void)113 _res_thread_get(void)
114 {
115 _res_thread* rt;
116 rt = pthread_getspecific( _res_key );
117
118 if (rt != NULL) {
119 /* We already have one thread-specific DNS state object.
120 * Check the serial value for any changes to net.* properties */
121 D("%s: Called for tid=%d rt=%p rt->pi=%p rt->serial=%d",
122 __FUNCTION__, gettid(), rt, rt->_pi, rt->_serial);
123 if (rt->_pi == NULL) {
124 /* The property wasn't created when _res_thread_get() was
125 * called the last time. This should only happen very
126 * early during the boot sequence. First, let's try to see if it
127 * is here now. */
128 rt->_pi = (struct prop_info*) __system_property_find("net.change");
129 if (rt->_pi == NULL) {
130 /* Still nothing, return current state */
131 D("%s: exiting for tid=%d rt=%d since system property not found",
132 __FUNCTION__, gettid(), rt);
133 return rt;
134 }
135 }
136 if (rt->_serial == __system_property_serial(rt->_pi)) {
137 /* Nothing changed, so return the current state */
138 D("%s: tid=%d rt=%p nothing changed, returning",
139 __FUNCTION__, gettid(), rt);
140 return rt;
141 }
142 /* Update the recorded serial number, and go reset the state */
143 rt->_serial = __system_property_serial(rt->_pi);
144 goto RESET_STATE;
145 }
146
147 /* It is the first time this function is called in this thread,
148 * we need to create a new thread-specific DNS resolver state. */
149 rt = _res_thread_alloc();
150 if (rt == NULL) {
151 return NULL;
152 }
153 pthread_setspecific( _res_key, rt );
154 D("%s: tid=%d Created new DNS state rt=%p",
155 __FUNCTION__, gettid(), rt);
156
157 RESET_STATE:
158 /* Reset the state, note that res_ninit() can now properly reset
159 * an existing state without leaking memory.
160 */
161 D("%s: tid=%d, rt=%p, resetting DNS state (options RES_INIT=%d)",
162 __FUNCTION__, gettid(), rt, (rt->_nres->options & RES_INIT) != 0);
163 if ( res_ninit( rt->_nres ) < 0 ) {
164 /* This should not happen */
165 D("%s: tid=%d rt=%p, woot, res_ninit() returned < 0",
166 __FUNCTION__, gettid(), rt);
167 _res_thread_free(rt);
168 pthread_setspecific( _res_key, NULL );
169 return NULL;
170 }
171 return rt;
172 }
173
174 __LIBC_HIDDEN__
175 struct __res_state _nres;
176
177 #if 0
178 struct resolv_cache*
179 __get_res_cache(void)
180 {
181 _res_thread* rt = _res_thread_get();
182
183 if (!rt)
184 return NULL;
185
186 if (!rt->_cache) {
187 rt->_cache = _resolv_cache_create();
188 }
189 return rt->_cache;
190 }
191 #endif
192
193 int*
__get_h_errno(void)194 __get_h_errno(void)
195 {
196 _res_thread* rt = _res_thread_get();
197 static int panic = NETDB_INTERNAL;
198
199 return rt ? &rt->_h_errno : &panic;
200 }
201
202 res_state
__res_get_state(void)203 __res_get_state(void)
204 {
205 _res_thread* rt = _res_thread_get();
206
207 return rt ? rt->_nres : NULL;
208 }
209
210 void
__res_put_state(res_state res __unused)211 __res_put_state(res_state res __unused)
212 {
213 /* nothing to do */
214 }
215
216 res_static
__res_get_static(void)217 __res_get_static(void)
218 {
219 _res_thread* rt = _res_thread_get();
220
221 return rt ? rt->_rstatic : NULL;
222 }
223