1  /* BZ #17977 _res_hconf_reorder_addrs test.
       2  
       3     Copyright (C) 2015-2023 Free Software Foundation, Inc.
       4     This file is part of the GNU C Library.
       5  
       6     The GNU C Library is free software; you can redistribute it and/or
       7     modify it under the terms of the GNU Lesser General Public
       8     License as published by the Free Software Foundation; either
       9     version 2.1 of the License, or (at your option) any later version.
      10  
      11     The GNU C Library is distributed in the hope that it will be useful,
      12     but WITHOUT ANY WARRANTY; without even the implied warranty of
      13     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      14     Lesser General Public License for more details.
      15  
      16     You should have received a copy of the GNU Lesser General Public
      17     License along with the GNU C Library; if not, see
      18     <https://www.gnu.org/licenses/>.  */
      19  
      20  #include <errno.h>
      21  #include <stdio.h>
      22  #include <stdlib.h>
      23  #include <string.h>
      24  #include <time.h>
      25  #include <dlfcn.h>
      26  #include <pthread.h>
      27  #include <netdb.h>
      28  #include <netinet/in.h>
      29  #include <sys/socket.h>
      30  
      31  static struct timespec ts;
      32  
      33  /* The first thread that gets a lock in _res_hconf_reorder_addrs()
      34     should hold the lock long enough to make two other threads blocked.
      35     This is achieved by slowing down realloc(3) that is called several times
      36     by _res_hconf_reorder_addrs().  */
      37  
      38  void *
      39  realloc (void *ptr, size_t len)
      40  {
      41    static void *(*fun) (void *, size_t);
      42  
      43    if (!fun)
      44      fun = dlsym (RTLD_NEXT, "realloc");
      45  
      46    if (ts.tv_nsec)
      47      nanosleep (&ts, NULL);
      48  
      49    return (*fun) (ptr, len);
      50  }
      51  
      52  static void *
      53  resolve (void *arg)
      54  {
      55    struct in_addr addr;
      56    struct hostent ent;
      57    struct hostent *result;
      58    int err;
      59    char buf[1024];
      60  
      61    addr.s_addr = htonl (INADDR_LOOPBACK);
      62    (void) gethostbyaddr_r ((void *) &addr, sizeof (addr), AF_INET,
      63  		          &ent, buf, sizeof (buf), &result, &err);
      64    return arg;
      65  }
      66  
      67  static int
      68  do_test (void)
      69  {
      70    #define N 3
      71    pthread_t thr[N];
      72    unsigned int i;
      73    int result = 0;
      74  
      75    /* turn on realloc slowdown */
      76    ts.tv_nsec = 100000000;
      77  
      78    for (i = 0; i < N; ++i)
      79      {
      80        int rc = pthread_create (&thr[i], NULL, resolve, NULL);
      81  
      82        if (rc)
      83  	{
      84  	  printf ("pthread_create: %s\n", strerror(rc));
      85  	  exit (1);
      86  	}
      87      }
      88  
      89    for (i = 0; i < N; ++i)
      90      {
      91        void *retval;
      92        int rc = pthread_join (thr[i], &retval);
      93  
      94        if (rc)
      95  	{
      96  	  printf ("pthread_join: %s\n", strerror(rc));
      97  	  exit (1);
      98  	}
      99        if (retval)
     100  	{
     101  	  printf ("thread %u exit status %p\n", i, retval);
     102  	  result = 1;
     103  	}
     104      }
     105  
     106    /* turn off realloc slowdown, no longer needed */
     107    ts.tv_nsec = 0;
     108  
     109    return result;
     110  }
     111  
     112  #define TEST_FUNCTION do_test ()
     113  #include "../test-skeleton.c"