cloexec_detect.c

   1 /*
   2  * Copyright (C) 2012-2020 all contributors <cmogstored-public@yhbt.net>
   3  * License: GPL-3.0+ <https://www.gnu.org/licenses/gpl-3.0.txt>
   4  */
   5 #include "cmogstored.h"
   6 bool mog_cloexec_atomic;
   7
   8 /*
   9  * The presence of O_CLOEXEC in headers doesn't mean the kernel supports it
  10  */
  11 #if defined(O_CLOEXEC) && (O_CLOEXEC != 0) && \
  12     defined(SOCK_CLOEXEC) && \
  13     defined(HAVE_ACCEPT4)
  14 __attribute__((constructor)) static void cloexec_detect(void)
  15 {
  16         int flags;
  17         int fd = open("/dev/null", O_RDONLY|O_CLOEXEC);
  18
  19         if (fd < 0) {
  20                 if (errno == EINVAL) goto out;
  21                 die_errno("open(/dev/null) failed");
  22         }
  23
  24         flags = fcntl(fd, F_GETFD);
  25         if (flags != -1)
  26                 mog_cloexec_atomic = ((flags & FD_CLOEXEC) == FD_CLOEXEC);
  27         mog_close(fd);
  28
  29         if (! mog_cloexec_atomic) goto out;
  30
  31         /* try to ensure sockets are sane, too */
  32         fd = socket(AF_INET, SOCK_STREAM|SOCK_CLOEXEC, 0);
  33         if (fd < 0) {
  34                 if (errno == EINVAL) goto out;
  35                 die_errno("socket(AF_INET, ...) failed");
  36         }
  37         flags = fcntl(fd, F_GETFD);
  38         if (flags != -1)
  39                 mog_cloexec_atomic = ((flags & FD_CLOEXEC) == FD_CLOEXEC);
  40         mog_close(fd);
  41
  42 out:
  43         if (mog_cloexec_atomic)
  44                 mog_cloexec_works();
  45         else
  46                 warn("close-on-exec is NOT atomic");
  47 }
  48 #endif /* no O_CLOEXEC at all */