server/captive.c

   1 /* nbdkit
   2  * Copyright Red Hat
   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 <signal.h>
  42 #include <assert.h>
  43
  44 #ifdef HAVE_SYS_WAIT_H
  45 #include <sys/wait.h>
  46 #endif
  47
  48 #include "utils.h"
  49
  50 #include "internal.h"
  51
  52 #ifndef WIN32
  53
  54 /* Handle the --run option.  If run is NULL, does nothing.  If run is
  55  * not NULL then run nbdkit as a captive subprocess of the command.
  56  */
  57 void
  58 run_command (void)
  59 {
  60   FILE *fp;
  61   char *cmd = NULL;
  62   size_t len = 0;
  63   int r, status;
  64   pid_t pid;
  65
  66   if (!run)
  67     return;
  68
  69   if (!export_name)
  70     export_name = "";
  71
  72   fp = open_memstream (&cmd, &len);
  73   if (fp == NULL) {
  74     perror ("open_memstream");
  75     exit (EXIT_FAILURE);
  76   }
  77
  78   /* Construct $uri. */
  79   fprintf (fp, "uri=");
  80   if (tls == 2)                 /* --tls=require */
  81     fprintf (fp, "nbds");
  82   else
  83     fprintf (fp, "nbd");
  84   if (port) {
  85     if (!vsock) {
  86       fprintf (fp, "://localhost:");
  87       shell_quote (port, fp);
  88       if (strcmp (export_name, "") != 0) {
  89         putc ('/', fp);
  90         uri_quote (export_name, fp);
  91       }
  92     }
  93     else {
  94       fprintf (fp, "+vsock://1:"); /* 1 = VMADDR_CID_LOCAL */
  95       shell_quote (port, fp);
  96       if (strcmp (export_name, "") != 0) {
  97         putc ('/', fp);
  98         uri_quote (export_name, fp);
  99       }
 100     }
 101   }
 102   else if (unixsocket) {
 103     fprintf (fp, "+unix://");
 104     if (strcmp (export_name, "") != 0) {
 105       putc ('/', fp);
 106       uri_quote (export_name, fp);
 107     }
 108     fprintf (fp, "\\?socket=");
 109     uri_quote (unixsocket, fp);
 110   }
 111   putc ('\n', fp);
 112
 113   /* Since nbdkit 1.24, $nbd is a synonym for $uri. */
 114   fprintf (fp, "nbd=\"$uri\"\n");
 115
 116   /* Expose $exportname. */
 117   fprintf (fp, "exportname=");
 118   shell_quote (export_name, fp);
 119   putc ('\n', fp);
 120
 121   /* Construct $tls, $port and $unixsocket. */
 122   if (tls > 0)
 123     fprintf (fp, "tls=%d\n", tls);
 124   fprintf (fp, "port=");
 125   if (port)
 126     shell_quote (port, fp);
 127   putc ('\n', fp);
 128   fprintf (fp, "unixsocket=");
 129   if (unixsocket)
 130     shell_quote (unixsocket, fp);
 131   fprintf (fp, "\n");
 132
 133   /* Add the --run command.  Note we don't have to quote this. */
 134   fprintf (fp, "%s", run);
 135
 136   if (fclose (fp) == EOF) {
 137     perror ("memstream failed");
 138     exit (EXIT_FAILURE);
 139   }
 140
 141   /* Fork.  Captive nbdkit runs as the child process. */
 142   pid = fork ();
 143   if (pid == -1) {
 144     perror ("fork");
 145     exit (EXIT_FAILURE);
 146   }
 147
 148   if (pid > 0) {              /* Parent process is the run command. */
 149     /* Restore original stdin/out */
 150     if (dup2 (saved_stdin, STDIN_FILENO) == -1 ||
 151         dup2 (saved_stdout, STDOUT_FILENO) == -1) {
 152       r = -1;
 153     }
 154     else
 155       r = system (cmd);
 156     if (r == -1) {
 157       nbdkit_error ("failure to execute external command: %m");
 158       r = EXIT_FAILURE;
 159     }
 160     else if (WIFEXITED (r))
 161       r = WEXITSTATUS (r);
 162     else {
 163       assert (WIFSIGNALED (r));
 164       fprintf (stderr, "%s: external command was killed by signal %d\n",
 165                program_name, WTERMSIG (r));
 166       r = WTERMSIG (r) + 128;
 167     }
 168
 169     switch (waitpid (pid, &status, WNOHANG)) {
 170     case -1:
 171       nbdkit_error ("waitpid: %m");
 172       r = EXIT_FAILURE;
 173       break;
 174     case 0:
 175       /* Captive nbdkit is still running; kill it.  We want to wait
 176        * for nbdkit to exit since that ensures all cleanup is done in
 177        * the plugin before we return.  However we don't care if nbdkit
 178        * returns an error, the exit code we return always comes from
 179        * the --run command.
 180        */
 181       kill (pid, SIGTERM);
 182       waitpid (pid, NULL, 0);
 183       break;
 184     default:
 185       /* Captive nbdkit exited unexpectedly; update the exit status. */
 186       if (WIFEXITED (status)) {
 187         if (r == 0)
 188           r = WEXITSTATUS (status);
 189       }
 190       else {
 191         assert (WIFSIGNALED (status));
 192         fprintf (stderr, "%s: nbdkit command was killed by signal %d\n",
 193                  program_name, WTERMSIG (status));
 194         r = WTERMSIG (status) + 128;
 195       }
 196     }
 197
 198     exit (r);
 199   }
 200
 201   free (cmd);
 202
 203   debug ("forked into background (new pid = %d)", getpid ());
 204 }
 205
 206 #else /* WIN32 */
 207
 208 void
 209 run_command (void)
 210 {
 211   if (!run)
 212     return;
 213
 214   NOT_IMPLEMENTED_ON_WINDOWS ("--run");
 215 }
 216
 217 #endif /* WIN32 */