server/captive.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 <sys/types.h>
  41 #include <sys/wait.h>
  42 #include <signal.h>
  43
  44 #include "utils.h"
  45
  46 #include "internal.h"
  47
  48 /* Handle the --run option.  If run is NULL, does nothing.  If run is
  49  * not NULL then run nbdkit as a captive subprocess of the command.
  50  */
  51 void
  52 run_command (void)
  53 {
  54   FILE *fp;
  55   char *cmd = NULL;
  56   size_t len = 0;
  57   int r;
  58   pid_t pid;
  59
  60   if (!run)
  61     return;
  62
  63   fp = open_memstream (&cmd, &len);
  64   if (fp == NULL) {
  65     perror ("open_memstream");
  66     exit (EXIT_FAILURE);
  67   }
  68
  69   /* Construct $uri. */
  70   fprintf (fp, "uri=");
  71   if (port) {
  72     fprintf (fp, "nbd://localhost:");
  73     shell_quote (port, fp);
  74   }
  75   else if (unixsocket) {
  76     fprintf (fp, "nbd+unix://\\?socket=");
  77     uri_quote (unixsocket, fp);
  78   }
  79   fprintf (fp, "\n");
  80
  81   /* Construct older $nbd "URL".  Unfortunately guestfish and qemu take
  82    * different syntax, so try to guess which one we need.
  83    */
  84   fprintf (fp, "nbd=");
  85   if (strstr (run, "guestfish")) {
  86     if (port) {
  87       fprintf (fp, "nbd://localhost:");
  88       shell_quote (port, fp);
  89     }
  90     else if (unixsocket) {
  91       fprintf (fp, "nbd://\\?socket=");
  92       shell_quote (unixsocket, fp);
  93     }
  94     else
  95       abort ();
  96   }
  97   else /* qemu */ {
  98     if (port) {
  99       fprintf (fp, "nbd:localhost:");
 100       shell_quote (port, fp);
 101     }
 102     else if (unixsocket) {
 103       fprintf (fp, "nbd:unix:");
 104       shell_quote (unixsocket, fp);
 105     }
 106     else
 107       abort ();
 108   }
 109   fprintf (fp, "\n");
 110
 111   /* Construct $port and $unixsocket. */
 112   fprintf (fp, "port=");
 113   if (port)
 114     shell_quote (port, fp);
 115   fprintf (fp, "\n");
 116   fprintf (fp, "unixsocket=");
 117   if (unixsocket)
 118     shell_quote (unixsocket, fp);
 119   fprintf (fp, "\n");
 120
 121   /* Add the --run command.  Note we don't have to quote this. */
 122   fprintf (fp, "%s", run);
 123
 124   if (fclose (fp) == EOF) {
 125     perror ("memstream failed");
 126     exit (EXIT_FAILURE);
 127   }
 128
 129   /* Fork.  Captive nbdkit runs as the child process. */
 130   pid = fork ();
 131   if (pid == -1) {
 132     perror ("fork");
 133     exit (EXIT_FAILURE);
 134   }
 135
 136   if (pid > 0) {              /* Parent process is the run command. */
 137     r = system (cmd);
 138     if (WIFEXITED (r))
 139       r = WEXITSTATUS (r);
 140     else if (WIFSIGNALED (r)) {
 141       fprintf (stderr, "%s: external command was killed by signal %d\n",
 142                program_name, WTERMSIG (r));
 143       r = 1;
 144     }
 145     else if (WIFSTOPPED (r)) {
 146       fprintf (stderr, "%s: external command was stopped by signal %d\n",
 147                program_name, WSTOPSIG (r));
 148       r = 1;
 149     }
 150
 151     kill (pid, SIGTERM);        /* Kill captive nbdkit. */
 152
 153     _exit (r);
 154   }
 155
 156   free (cmd);
 157
 158   debug ("forked into background (new pid = %d)", getpid ());
 159 }