server/socket-activation.c

   1 /* nbdkit
   2  * Copyright (C) 2019 Red Hat Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdarg.h>
  38 #include <string.h>
  39 #include <unistd.h>
  40 #include <fcntl.h>
  41 #include <errno.h>
  42
  43 #include "internal.h"
  44
  45 /* Handle socket activation.  This is controlled through special
  46  * environment variables inherited by nbdkit.  Returns 0 if no socket
  47  * activation.  Otherwise returns the number of FDs.  See also
  48  * virGetListenFDs in libvirt.org:src/util/virutil.c
  49  */
  50 unsigned int
  51 get_socket_activation (void)
  52 {
  53   const char *s;
  54   unsigned int pid;
  55   unsigned int nr_fds;
  56   unsigned int i;
  57   int fd;
  58
  59   s = getenv ("LISTEN_PID");
  60   if (s == NULL)
  61     return 0;
  62   if (sscanf (s, "%u", &pid) != 1) {
  63     fprintf (stderr, "%s: malformed %s environment variable (ignored)\n",
  64              program_name, "LISTEN_PID");
  65     return 0;
  66   }
  67   if (pid != getpid ()) {
  68     fprintf (stderr, "%s: %s was not for us (ignored)\n",
  69              program_name, "LISTEN_PID");
  70     return 0;
  71   }
  72
  73   s = getenv ("LISTEN_FDS");
  74   if (s == NULL)
  75     return 0;
  76   if (sscanf (s, "%u", &nr_fds) != 1) {
  77     fprintf (stderr, "%s: malformed %s environment variable (ignored)\n",
  78              program_name, "LISTEN_FDS");
  79     return 0;
  80   }
  81
  82   /* So these are not passed to any child processes we might start. */
  83   unsetenv ("LISTEN_FDS");
  84   unsetenv ("LISTEN_PID");
  85
  86   /* So the file descriptors don't leak into child processes. */
  87   for (i = 0; i < nr_fds; ++i) {
  88     fd = FIRST_SOCKET_ACTIVATION_FD + i;
  89     if (fcntl (fd, F_SETFD, FD_CLOEXEC) == -1) {
  90       /* If we cannot set FD_CLOEXEC then it probably means the file
  91        * descriptor is invalid, so socket activation has gone wrong
  92        * and we should exit.
  93        */
  94       fprintf (stderr, "%s: socket activation: "
  95                "invalid file descriptor fd = %d: %s\n",
  96                program_name, fd, strerror(errno));
  97       exit (EXIT_FAILURE);
  98     }
  99   }
 100
 101   return nr_fds;
 102 }