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 /* Define some functions that go int libc.so.  */
  19
  20 #if defined(LIBC_SCCS) && !defined(lint)
  21 static const char rcsid[] = "$Id$";
  22 #endif /* LIBC_SCCS and not lint */
  23
  24 #include <sys/types.h>
  25 #include <sys/param.h>
  26 #include <sys/socket.h>
  27 #include <sys/time.h>
  28
  29 #include <netinet/in.h>
  30 #include <arpa/inet.h>
  31 #include <arpa/nameser.h>
  32
  33 #include <ctype.h>
  34 #include <netdb.h>
  35 #include <resolv.h>
  36 #include <stdio.h>
  37 #include <stdlib.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40
  41
  42 /* This is the old res_init function.  It has been moved from
  43    res_data.c to this file since res_init should go into libc.so but
  44    the rest of res_data not.  */
  45
  46
  47 int
  48 res_init(void) {
  49         extern int __res_vinit(res_state, int);
  50
  51         /*
  52          * These three fields used to be statically initialized.  This made
  53          * it hard to use this code in a shared library.  It is necessary,
  54          * now that we're doing dynamic initialization here, that we preserve
  55          * the old semantics: if an application modifies one of these three
  56          * fields of _res before res_init() is called, res_init() will not
  57          * alter them.  Of course, if an application is setting them to
  58          * _zero_ before calling res_init(), hoping to override what used
  59          * to be the static default, we can't detect it and unexpected results
  60          * will follow.  Zero for any of these fields would make no sense,
  61          * so one can safely assume that the applications were already getting
  62          * unexpected results.
  63          *
  64          * _res.options is tricky since some apps were known to diddle the bits
  65          * before res_init() was first called. We can't replicate that semantic
  66          * with dynamic initialization (they may have turned bits off that are
  67          * set in RES_DEFAULT).  Our solution is to declare such applications
  68          * "broken".  They could fool us by setting RES_INIT but none do (yet).
  69          */
  70         if (!_res.retrans)
  71                 _res.retrans = RES_TIMEOUT;
  72         if (!_res.retry)
  73                 _res.retry = 4;
  74         if (!(_res.options & RES_INIT))
  75                 _res.options = RES_DEFAULT;
  76
  77         /*
  78          * This one used to initialize implicitly to zero, so unless the app
  79          * has set it to something in particular, we can randomize it now.
  80          */
  81         if (!_res.id)
  82                 _res.id = res_randomid();
  83
  84         return (__res_vinit(&_res, 1));
  85 }
  86
  87 /* We need a resolver context - in unthreaded apps, this weak function
  88    provides it.  */
  89
  90 #undef _res
  91
  92 struct __res_state _res;
  93
  94
  95 struct __res_state *
  96 weak_const_function
  97 __res_state(void)
  98 {
  99   return &_res;
 100 }