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 <logd.h>
46#  include <unistd.h>  /* for gettid() */
47#  define D(...)  __libc_android_log_print(ANDROID_LOG_DEBUG,"libc", __VA_ARGS__)
48#else
49#  define D(...)  do{}while(0)
50#endif
51
52static pthread_key_t   _res_key;
53static pthread_once_t  _res_once;
54
55typedef 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
63static _res_thread*
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
81static void
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
95static void
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
107static void
108_res_init_key( void )
109{
110    pthread_key_create( &_res_key, _res_thread_free );
111}
112
113static _res_thread*
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
159RESET_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__
177struct __res_state _nres;
178
179#if 0
180struct 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
195int*
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
204res_state
205__res_get_state(void)
206{
207    _res_thread*  rt = _res_thread_get();
208
209    return rt ? rt->_nres : NULL;
210}
211
212void
213__res_put_state(res_state res)
214{
215    /* nothing to do */
216    res=res;
217}
218
219res_static
220__res_get_static(void)
221{
222    _res_thread*  rt = _res_thread_get();
223
224    return rt ? rt->_rstatic : NULL;
225}
226