1/*
2 * Copyright (c) 1995-1999 by Internet Software Consortium.
3 *
4 * Permission to use, copy, modify, and distribute this software for any
5 * purpose with or without fee is hereby granted, provided that the above
6 * copyright notice and this permission notice appear in all copies.
7 *
8 * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
9 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
10 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
11 * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
12 * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
13 * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
14 * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
15 * SOFTWARE.
16 */
17
18#include <atomic.h>
19#include <limits.h>
20#include <sys/types.h>
21#include <netinet/in.h>
22#include <arpa/nameser.h>
23#include <resolv.h>
24#include <libc-lock.h>
25
26
27/* The following bit is copied from res_data.c (where it is #ifdef'ed
28 out) since res_init() should go into libc.so but the rest of that
29 file should not. */
30
31extern unsigned long long int __res_initstamp attribute_hidden;
32/* We have atomic increment operations on 64-bit platforms. */
33#if __WORDSIZE == 64
34# define atomicinclock(lock) (void) 0
35# define atomicincunlock(lock) (void) 0
36# define atomicinc(var) catomic_increment (&(var))
37#else
38__libc_lock_define_initialized (static, lock);
39# define atomicinclock(lock) __libc_lock_lock (lock)
40# define atomicincunlock(lock) __libc_lock_unlock (lock)
41# define atomicinc(var) ++var
42#endif
43
44int
45res_init(void) {
46 extern int __res_vinit(res_state, int);
47
48 /*
49 * These three fields used to be statically initialized. This made
50 * it hard to use this code in a shared library. It is necessary,
51 * now that we're doing dynamic initialization here, that we preserve
52 * the old semantics: if an application modifies one of these three
53 * fields of _res before res_init() is called, res_init() will not
54 * alter them. Of course, if an application is setting them to
55 * _zero_ before calling res_init(), hoping to override what used
56 * to be the static default, we can't detect it and unexpected results
57 * will follow. Zero for any of these fields would make no sense,
58 * so one can safely assume that the applications were already getting
59 * unexpected results.
60 *
61 * _res.options is tricky since some apps were known to diddle the bits
62 * before res_init() was first called. We can't replicate that semantic
63 * with dynamic initialization (they may have turned bits off that are
64 * set in RES_DEFAULT). Our solution is to declare such applications
65 * "broken". They could fool us by setting RES_INIT but none do (yet).
66 */
67 if (!_res.retrans)
68 _res.retrans = RES_TIMEOUT;
69 if (!_res.retry)
70 _res.retry = 4;
71 if (!(_res.options & RES_INIT))
72 _res.options = RES_DEFAULT;
73 else if (_res.nscount > 0)
74 __res_iclose (&_res, true); /* Close any VC sockets. */
75
76 /*
77 * This one used to initialize implicitly to zero, so unless the app
78 * has set it to something in particular, we can randomize it now.
79 */
80 if (!_res.id)
81 _res.id = res_randomid();
82
83 atomicinclock (lock);
84 /* Request all threads to re-initialize their resolver states,
85 resolv.conf might have changed. */
86 atomicinc (__res_initstamp);
87 atomicincunlock (lock);
88
89 return (__res_vinit(&_res, 1));
90}
91
92/* Initialize resp if RES_INIT is not yet set or if res_init in some other
93 thread requested re-initializing. */
94int
95__res_maybe_init (res_state resp, int preinit)
96{
97 if (resp->options & RES_INIT) {
98 if (__res_initstamp != resp->_u._ext.initstamp) {
99 if (resp->nscount > 0)
100 __res_iclose (resp, true);
101 return __res_vinit (resp, 1);
102 }
103 return 0;
104 } else if (preinit) {
105 if (!resp->retrans)
106 resp->retrans = RES_TIMEOUT;
107 if (!resp->retry)
108 resp->retry = 4;
109 resp->options = RES_DEFAULT;
110 if (!resp->id)
111 resp->id = res_randomid ();
112 return __res_vinit (resp, 1);
113 } else
114 return __res_ninit (resp);
115}
116libc_hidden_def (__res_maybe_init)
117
118/* This needs to be after the use of _res in res_init, above. */
119#undef _res
120
121/* The resolver state for use by single-threaded programs.
122 This differs from plain `struct __res_state _res;' in that it doesn't
123 create a common definition, but a plain symbol that resides in .bss,
124 which can have an alias. */
125struct __res_state _res __attribute__ ((nocommon));
126
127#undef __resp
128__thread struct __res_state *__resp = &_res;
129extern __thread struct __res_state *__libc_resp
130 __attribute__ ((alias ("__resp"))) attribute_hidden;
131
132/* We declare this with compat_symbol so that it's not
133 visible at link time. Programs must use the accessor functions. */
134#ifdef SHARED
135# include <shlib-compat.h>
136compat_symbol (libc, _res, _res, GLIBC_2_0);
137#endif
138
139#include <shlib-compat.h>
140
141#if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_2)
142# undef res_init
143extern int __res_init_weak (void);
144weak_extern (__res_init_weak);
145strong_alias (__res_init, __res_init_weak);
146compat_symbol (libc, __res_init_weak, res_init, GLIBC_2_0);
147#endif
148