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
38 #define _REALLY_INCLUDE_SYS__SYSTEM_PROPERTIES_H_
39 #include <sys/_system_properties.h>
40
41 /* Set to 1 to enable debug traces */
42 #define DEBUG 0
43
44 #if DEBUG
45 # include "libc_logging.h"
46 # include <unistd.h> /* for gettid() */
47 # define D(...) __libc_format_log(ANDROID_LOG_DEBUG,"libc", __VA_ARGS__)
48 #else
49 # define D(...) do{}while(0)
50 #endif
51
52 static pthread_key_t _res_key;
53 static pthread_once_t _res_once = PTHREAD_ONCE_INIT;
54
55 typedef struct {
56 int _h_errno;
57 struct __res_state _nres[1];
58 unsigned _serial;
59 struct prop_info* _pi;
60 struct res_static _rstatic[1];
61 } _res_thread;
62
63 static _res_thread*
_res_thread_alloc(void)64 _res_thread_alloc(void)
65 {
66 _res_thread* rt = calloc(1, sizeof(*rt));
67
68 if (rt) {
69 rt->_h_errno = 0;
70 /* Special system property which tracks any changes to 'net.*'. */
71 rt->_serial = 0;
72 rt->_pi = (struct prop_info*) __system_property_find("net.change");
73 if (rt->_pi) {
74 rt->_serial = rt->_pi->serial;
75 }
76 memset(rt->_rstatic, 0, sizeof rt->_rstatic);
77 }
78 return rt;
79 }
80
81 static void
_res_static_done(res_static rs)82 _res_static_done( res_static rs )
83 {
84 /* fortunately, there is nothing to do here, since the
85 * points in h_addr_ptrs and host_aliases should all
86 * point to 'hostbuf'
87 */
88 if (rs->hostf) { /* should not happen in theory, but just be safe */
89 fclose(rs->hostf);
90 rs->hostf = NULL;
91 }
92 free(rs->servent.s_aliases);
93 }
94
95 static void
_res_thread_free(void * _rt)96 _res_thread_free( void* _rt )
97 {
98 _res_thread* rt = _rt;
99
100 D("%s: rt=%p for thread=%d", __FUNCTION__, rt, gettid());
101
102 _res_static_done(rt->_rstatic);
103 res_ndestroy(rt->_nres);
104 free(rt);
105 }
106
107 static void
_res_init_key(void)108 _res_init_key( void )
109 {
110 pthread_key_create( &_res_key, _res_thread_free );
111 }
112
113 static _res_thread*
_res_thread_get(void)114 _res_thread_get(void)
115 {
116 _res_thread* rt;
117 pthread_once( &_res_once, _res_init_key );
118 rt = pthread_getspecific( _res_key );
119
120 if (rt != NULL) {
121 /* We already have one thread-specific DNS state object.
122 * Check the serial value for any changes to net.* properties */
123 D("%s: Called for tid=%d rt=%p rt->pi=%p rt->serial=%d",
124 __FUNCTION__, gettid(), rt, rt->_pi, rt->_serial);
125 if (rt->_pi == NULL) {
126 /* The property wasn't created when _res_thread_get() was
127 * called the last time. This should only happen very
128 * early during the boot sequence. First, let's try to see if it
129 * is here now. */
130 rt->_pi = (struct prop_info*) __system_property_find("net.change");
131 if (rt->_pi == NULL) {
132 /* Still nothing, return current state */
133 D("%s: exiting for tid=%d rt=%d since system property not found",
134 __FUNCTION__, gettid(), rt);
135 return rt;
136 }
137 }
138 if (rt->_serial == rt->_pi->serial) {
139 /* Nothing changed, so return the current state */
140 D("%s: tid=%d rt=%p nothing changed, returning",
141 __FUNCTION__, gettid(), rt);
142 return rt;
143 }
144 /* Update the recorded serial number, and go reset the state */
145 rt->_serial = rt->_pi->serial;
146 goto RESET_STATE;
147 }
148
149 /* It is the first time this function is called in this thread,
150 * we need to create a new thread-specific DNS resolver state. */
151 rt = _res_thread_alloc();
152 if (rt == NULL) {
153 return NULL;
154 }
155 pthread_setspecific( _res_key, rt );
156 D("%s: tid=%d Created new DNS state rt=%p",
157 __FUNCTION__, gettid(), rt);
158
159 RESET_STATE:
160 /* Reset the state, note that res_ninit() can now properly reset
161 * an existing state without leaking memory.
162 */
163 D("%s: tid=%d, rt=%p, resetting DNS state (options RES_INIT=%d)",
164 __FUNCTION__, gettid(), rt, (rt->_nres->options & RES_INIT) != 0);
165 if ( res_ninit( rt->_nres ) < 0 ) {
166 /* This should not happen */
167 D("%s: tid=%d rt=%p, woot, res_ninit() returned < 0",
168 __FUNCTION__, gettid(), rt);
169 _res_thread_free(rt);
170 pthread_setspecific( _res_key, NULL );
171 return NULL;
172 }
173 return rt;
174 }
175
176 __LIBC_HIDDEN__
177 struct __res_state _nres;
178
179 #if 0
180 struct resolv_cache*
181 __get_res_cache(void)
182 {
183 _res_thread* rt = _res_thread_get();
184
185 if (!rt)
186 return NULL;
187
188 if (!rt->_cache) {
189 rt->_cache = _resolv_cache_create();
190 }
191 return rt->_cache;
192 }
193 #endif
194
195 int*
__get_h_errno(void)196 __get_h_errno(void)
197 {
198 _res_thread* rt = _res_thread_get();
199 static int panic = NETDB_INTERNAL;
200
201 return rt ? &rt->_h_errno : &panic;
202 }
203
204 res_state
__res_get_state(void)205 __res_get_state(void)
206 {
207 _res_thread* rt = _res_thread_get();
208
209 return rt ? rt->_nres : NULL;
210 }
211
212 void
__res_put_state(res_state res)213 __res_put_state(res_state res)
214 {
215 /* nothing to do */
216 res=res;
217 }
218
219 res_static
__res_get_static(void)220 __res_get_static(void)
221 {
222 _res_thread* rt = _res_thread_get();
223
224 return rt ? rt->_rstatic : NULL;
225 }
226