resolv/res_libc.c

   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 <sys/types.h>
  19 #include <netinet/in.h>
  20 #include <arpa/nameser.h>
  21 #include <resolv.h>
  22
  23
  24 /* The following bit is copied from res_data.c (where it is #ifdef'ed
  25    out) since res_init() should go into libc.so but the rest of that
  26    file should not.  */
  27
  28 int
  29 res_init(void) {
  30         extern int __res_vinit(res_state, int);
  31
  32         /*
  33          * These three fields used to be statically initialized.  This made
  34          * it hard to use this code in a shared library.  It is necessary,
  35          * now that we're doing dynamic initialization here, that we preserve
  36          * the old semantics: if an application modifies one of these three
  37          * fields of _res before res_init() is called, res_init() will not
  38          * alter them.  Of course, if an application is setting them to
  39          * _zero_ before calling res_init(), hoping to override what used
  40          * to be the static default, we can't detect it and unexpected results
  41          * will follow.  Zero for any of these fields would make no sense,
  42          * so one can safely assume that the applications were already getting
  43          * unexpected results.
  44          *
  45          * _res.options is tricky since some apps were known to diddle the bits
  46          * before res_init() was first called. We can't replicate that semantic
  47          * with dynamic initialization (they may have turned bits off that are
  48          * set in RES_DEFAULT).  Our solution is to declare such applications
  49          * "broken".  They could fool us by setting RES_INIT but none do (yet).
  50          */
  51         if (!_res.retrans)
  52                 _res.retrans = RES_TIMEOUT;
  53         if (!_res.retry)
  54                 _res.retry = 4;
  55         if (!(_res.options & RES_INIT))
  56                 _res.options = RES_DEFAULT;
  57
  58         /*
  59          * This one used to initialize implicitly to zero, so unless the app
  60          * has set it to something in particular, we can randomize it now.
  61          */
  62         if (!_res.id)
  63                 _res.id = res_randomid();
  64
  65         return (__res_vinit(&_res, 1));
  66 }
  67 \f
  68 /* This needs to be after the use of _res in res_init, above.  */
  69 #undef _res
  70
  71 #include <tls.h>
  72
  73 #if USE___THREAD
  74 /* With __thread support, this per-thread variable is used in all cases.  */
  75 __thread struct __res_state _res;
  76 extern __thread struct __res_state __libc_res __attribute__ ((alias ("_res")))
  77   attribute_hidden;
  78 # define _res __libc_res
  79 #else
  80 /* The resolver state for use by single-threaded programs.
  81    This differs from plain `struct __res_state _res;' in that it doesn't
  82    create a common definition, but a plain symbol that resides in .bss,
  83    which can have an alias.  */
  84 struct __res_state _res __attribute__((section (".bss")));
  85
  86 /* We declare this with compat_symbol so that it's not
  87    visible at link time.  Programs must use the accessor functions.  */
  88 # if defined HAVE_ELF && defined SHARED && defined DO_VERSIONING
  89 #  include <shlib-compat.h>
  90 compat_symbol (libc, _res, _res, GLIBC_2_0);
  91 # endif
  92 #endif
  93
  94 #include <shlib-compat.h>
  95
  96 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_2)
  97 # undef res_init
  98 extern int __res_init_weak (void);
  99 weak_extern (__res_init_weak);
 100 strong_alias (__res_init, __res_init_weak);
 101 compat_symbol (libc, __res_init_weak, res_init, GLIBC_2_0);
 102 #endif