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 <bits/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: 
   31: extern 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: 
   44: int
   45: res_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.  */
   94: int
   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:                 }
  104:                 return 0;
  105:         } else if (preinit) {
  106:                 if (!resp->retrans)
  107:                         resp->retrans = RES_TIMEOUT;
  108:                 if (!resp->retry)
  109:                         resp->retry = 4;
  110:                 resp->options = RES_DEFAULT;
  111:                 if (!resp->id)
  112:                         resp->id = res_randomid ();
  113:                 return __res_vinit (resp, 1);
  114:         } else
  115:                 return __res_ninit (resp);
  116: }
  117: libc_hidden_def (__res_maybe_init)
  118: ^L
  119: /* This needs to be after the use of _res in res_init, above.  */
  120: #undef _res
  121: 
  122: /* The resolver state for use by single-threaded programs.
  123:    This differs from plain `struct __res_state _res;' in that it doesn't
  124:    create a common definition, but a plain symbol that resides in .bss,
  125:    which can have an alias.  */
  126: struct __res_state _res __attribute__((section (".bss")));
  127: 
  128: #include <tls.h>
  129: 
  130: #if USE___THREAD
  131: #undef __resp
  132: __thread struct __res_state *__resp = &_res;
  133: extern __thread struct __res_state *__libc_resp
  134:   __attribute__ ((alias ("__resp"))) attribute_hidden;
  135: #endif
  136: 
  137: /* We declare this with compat_symbol so that it's not
  138:    visible at link time.  Programs must use the accessor functions.  */
  139: #if defined HAVE_ELF && defined SHARED && defined DO_VERSIONING
  140: # include <shlib-compat.h>
  141: compat_symbol (libc, _res, _res, GLIBC_2_0);
  142: #endif
  143: 
  144: #include <shlib-compat.h>
  145: 
  146: #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_2)
  147: # undef res_init
  148: extern int __res_init_weak (void);
  149: weak_extern (__res_init_weak);
  150: strong_alias (__res_init, __res_init_weak);
  151: compat_symbol (libc, __res_init_weak, res_init, GLIBC_2_0);
  152: #endif