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
40 /* Set to 1 to enable debug traces */
41 #define DEBUG 0
42
43 #if DEBUG
44 # include <async_safe/log.h>
45 # include <unistd.h> /* for gettid() */
46 # define D(...) async_safe_format_log(ANDROID_LOG_DEBUG,"libc", __VA_ARGS__)
47 #else
48 # define D(...) do{}while(0)
49 #endif
50
51 typedef struct {
52 int _h_errno;
53 // TODO: Have one __res_state per network so we don't have to repopulate frequently.
54 struct __res_state _nres[1];
55 struct res_static _rstatic[1];
56 } _res_thread;
57
58 static _res_thread*
_res_thread_alloc(void)59 _res_thread_alloc(void)
60 {
61 _res_thread* rt = calloc(1, sizeof(*rt));
62
63 if (rt) {
64 rt->_h_errno = 0;
65 memset(rt->_rstatic, 0, sizeof rt->_rstatic);
66 }
67 return rt;
68 }
69
70 static void
_res_static_done(struct res_static * rs)71 _res_static_done(struct res_static* rs)
72 {
73 /* fortunately, there is nothing to do here, since the
74 * points in h_addr_ptrs and host_aliases should all
75 * point to 'hostbuf'
76 */
77 if (rs->hostf) { /* should not happen in theory, but just be safe */
78 fclose(rs->hostf);
79 rs->hostf = NULL;
80 }
81 free(rs->servent.s_aliases);
82 }
83
84 static void
_res_thread_free(void * _rt)85 _res_thread_free( void* _rt )
86 {
87 _res_thread* rt = _rt;
88
89 D("%s: rt=%p for thread=%d", __FUNCTION__, rt, gettid());
90
91 _res_static_done(rt->_rstatic);
92 res_ndestroy(rt->_nres);
93 free(rt);
94 }
95
96 static pthread_key_t _res_key;
97
__res_key_init()98 __attribute__((constructor)) static void __res_key_init() {
99 pthread_key_create(&_res_key, _res_thread_free);
100 }
101
102 static _res_thread*
_res_thread_get(void)103 _res_thread_get(void)
104 {
105 _res_thread* rt;
106 rt = pthread_getspecific( _res_key );
107
108 if (rt != NULL) {
109 return rt;
110 }
111
112 /* It is the first time this function is called in this thread,
113 * we need to create a new thread-specific DNS resolver state. */
114 rt = _res_thread_alloc();
115 if (rt == NULL) {
116 return NULL;
117 }
118 pthread_setspecific( _res_key, rt );
119 D("%s: tid=%d Created new DNS state rt=%p",
120 __FUNCTION__, gettid(), rt);
121
122 /* Reset the state, note that res_ninit() can now properly reset
123 * an existing state without leaking memory.
124 */
125 D("%s: tid=%d, rt=%p, setting DNS state (options RES_INIT=%d)",
126 __FUNCTION__, gettid(), rt, (rt->_nres->options & RES_INIT) != 0);
127 if ( res_ninit( rt->_nres ) < 0 ) {
128 /* This should not happen */
129 D("%s: tid=%d rt=%p, woot, res_ninit() returned < 0",
130 __FUNCTION__, gettid(), rt);
131 _res_thread_free(rt);
132 pthread_setspecific( _res_key, NULL );
133 return NULL;
134 }
135 return rt;
136 }
137
138 int*
__get_h_errno(void)139 __get_h_errno(void)
140 {
141 _res_thread* rt = _res_thread_get();
142 static int panic = NETDB_INTERNAL;
143
144 return rt ? &rt->_h_errno : &panic;
145 }
146
147 res_state
__res_get_state(void)148 __res_get_state(void)
149 {
150 _res_thread* rt = _res_thread_get();
151
152 return rt ? rt->_nres : NULL;
153 }
154
155 void
__res_put_state(res_state res __unused)156 __res_put_state(res_state res __unused)
157 {
158 /* nothing to do */
159 }
160
__res_get_static(void)161 struct res_static* __res_get_static(void) {
162 _res_thread* rt = _res_thread_get();
163
164 return rt ? rt->_rstatic : NULL;
165 }
166