resolv/getaddrinfo_a.c

   1 /* Copyright (C) 2001-2020 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2001.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <netdb.h>
  21 #include <pthread.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24
  25 #include <gai_misc.h>
  26
  27
  28 /* We need this special structure to handle asynchronous I/O.  */
  29 struct async_waitlist
  30   {
  31     unsigned int counter;
  32     struct sigevent sigev;
  33     struct waitlist list[0];
  34   };
  35
  36
  37 int
  38 getaddrinfo_a (int mode, struct gaicb *list[], int ent, struct sigevent *sig)
  39 {
  40   struct sigevent defsigev;
  41   struct requestlist *requests[ent];
  42   int cnt;
  43   volatile unsigned int total = 0;
  44   int result = 0;
  45
  46   /* Check arguments.  */
  47   if (mode != GAI_WAIT && mode != GAI_NOWAIT)
  48     {
  49       __set_errno (EINVAL);
  50       return EAI_SYSTEM;
  51     }
  52
  53   if (sig == NULL)
  54     {
  55       defsigev.sigev_notify = SIGEV_NONE;
  56       sig = &defsigev;
  57     }
  58
  59   /* Request the mutex.  */
  60   pthread_mutex_lock (&__gai_requests_mutex);
  61
  62   /* Now we can enqueue all requests.  Since we already acquired the
  63      mutex the enqueue function need not do this.  */
  64   for (cnt = 0; cnt < ent; ++cnt)
  65     if (list[cnt] != NULL)
  66       {
  67         requests[cnt] = __gai_enqueue_request (list[cnt]);
  68
  69         if (requests[cnt] != NULL)
  70           /* Successfully enqueued.  */
  71           ++total;
  72         else
  73           /* Signal that we've seen an error.  `errno' and the error code
  74              of the gaicb will tell more.  */
  75           result = EAI_SYSTEM;
  76       }
  77     else
  78       requests[cnt] = NULL;
  79
  80   if (total == 0)
  81     {
  82       /* We don't have anything to do except signalling if we work
  83          asynchronously.  */
  84
  85       /* Release the mutex.  We do this before raising a signal since the
  86          signal handler might do a `siglongjmp' and then the mutex is
  87          locked forever.  */
  88       pthread_mutex_unlock (&__gai_requests_mutex);
  89
  90       if (mode == GAI_NOWAIT)
  91         __gai_notify_only (sig,
  92                            sig->sigev_notify == SIGEV_SIGNAL ? getpid () : 0);
  93
  94       return result;
  95     }
  96   else if (mode == GAI_WAIT)
  97     {
  98 #ifndef DONT_NEED_GAI_MISC_COND
  99       pthread_cond_t cond = PTHREAD_COND_INITIALIZER;
 100 #endif
 101       struct waitlist waitlist[ent];
 102       int oldstate;
 103
 104       total = 0;
 105       for (cnt = 0; cnt < ent; ++cnt)
 106         if (requests[cnt] != NULL)
 107           {
 108 #ifndef DONT_NEED_GAI_MISC_COND
 109             waitlist[cnt].cond = &cond;
 110 #endif
 111             waitlist[cnt].next = requests[cnt]->waiting;
 112             waitlist[cnt].counterp = &total;
 113             waitlist[cnt].sigevp = NULL;
 114             waitlist[cnt].caller_pid = 0;       /* Not needed.  */
 115             requests[cnt]->waiting = &waitlist[cnt];
 116             ++total;
 117           }
 118
 119       /* Since `pthread_cond_wait'/`pthread_cond_timedwait' are cancelation
 120          points we must be careful.  We added entries to the waiting lists
 121          which we must remove.  So defer cancelation for now.  */
 122       pthread_setcancelstate (PTHREAD_CANCEL_DISABLE, &oldstate);
 123
 124       while (total > 0)
 125         {
 126 #ifdef DONT_NEED_GAI_MISC_COND
 127           int not_used __attribute__ ((unused));
 128           GAI_MISC_WAIT (not_used, total, NULL, 1);
 129 #else
 130           pthread_cond_wait (&cond, &__gai_requests_mutex);
 131 #endif
 132         }
 133
 134       /* Now it's time to restore the cancelation state.  */
 135       pthread_setcancelstate (oldstate, NULL);
 136
 137 #ifndef DONT_NEED_GAI_MISC_COND
 138       /* Release the conditional variable.  */
 139       if (pthread_cond_destroy (&cond) != 0)
 140         /* This must never happen.  */
 141         abort ();
 142 #endif
 143     }
 144   else
 145     {
 146       struct async_waitlist *waitlist;
 147
 148       waitlist = (struct async_waitlist *)
 149         malloc (sizeof (struct async_waitlist)
 150                 + (ent * sizeof (struct waitlist)));
 151
 152       if (waitlist == NULL)
 153         result = EAI_AGAIN;
 154       else
 155         {
 156           pid_t caller_pid = sig->sigev_notify == SIGEV_SIGNAL ? getpid () : 0;
 157           total = 0;
 158
 159           for (cnt = 0; cnt < ent; ++cnt)
 160             if (requests[cnt] != NULL)
 161               {
 162 #ifndef DONT_NEED_GAI_MISC_COND
 163                 waitlist->list[cnt].cond = NULL;
 164 #endif
 165                 waitlist->list[cnt].next = requests[cnt]->waiting;
 166                 waitlist->list[cnt].counterp = &waitlist->counter;
 167                 waitlist->list[cnt].sigevp = &waitlist->sigev;
 168                 waitlist->list[cnt].caller_pid = caller_pid;
 169                 requests[cnt]->waiting = &waitlist->list[cnt];
 170                 ++total;
 171               }
 172
 173           waitlist->counter = total;
 174           waitlist->sigev = *sig;
 175         }
 176     }
 177
 178   /* Release the mutex.  */
 179   pthread_mutex_unlock (&__gai_requests_mutex);
 180
 181   return result;
 182 }