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 #include <assert.h>
  44
  45 #include "utils.h"
  46
  47 #include "internal.h"
  48
  49 /* Handle the --run option.  If run is NULL, does nothing.  If run is
  50  * not NULL then run nbdkit as a captive subprocess of the command.
  51  */
  52 void
  53 run_command (void)
  54 {
  55   FILE *fp;
  56   char *cmd = NULL;
  57   size_t len = 0;
  58   int r, status;
  59   pid_t pid;
  60
  61   if (!run)
  62     return;
  63
  64   assert (exportname != NULL);
  65
  66   fp = open_memstream (&cmd, &len);
  67   if (fp == NULL) {
  68     perror ("open_memstream");
  69     exit (EXIT_FAILURE);
  70   }
  71
  72   /* Construct $uri. */
  73   fprintf (fp, "uri=");
  74   if (port) {
  75     fprintf (fp, "nbd://localhost:");
  76     shell_quote (port, fp);
  77     if (strcmp (exportname, "") != 0) {
  78       putc ('/', fp);
  79       uri_quote (exportname, fp);
  80     }
  81   }
  82   else if (unixsocket) {
  83     fprintf (fp, "nbd+unix://");
  84     if (strcmp (exportname, "") != 0) {
  85       putc ('/', fp);
  86       uri_quote (exportname, fp);
  87     }
  88     fprintf (fp, "\\?socket=");
  89     uri_quote (unixsocket, fp);
  90   }
  91   putc ('\n', fp);
  92
  93   /* Expose $exportname. */
  94   fprintf (fp, "exportname=");
  95   shell_quote (exportname, fp);
  96   putc ('\n', fp);
  97
  98   /* Construct older $nbd "URL".  Unfortunately guestfish and qemu take
  99    * different syntax, so try to guess which one we need.
 100    */
 101   fprintf (fp, "nbd=");
 102   if (strstr (run, "guestfish")) {
 103     if (port) {
 104       fprintf (fp, "nbd://localhost:");
 105       shell_quote (port, fp);
 106     }
 107     else if (unixsocket) {
 108       fprintf (fp, "nbd://\\?socket=");
 109       shell_quote (unixsocket, fp);
 110     }
 111     else
 112       abort ();
 113   }
 114   else /* qemu */ {
 115     if (port) {
 116       fprintf (fp, "nbd:localhost:");
 117       shell_quote (port, fp);
 118     }
 119     else if (unixsocket) {
 120       fprintf (fp, "nbd:unix:");
 121       shell_quote (unixsocket, fp);
 122     }
 123     else
 124       abort ();
 125   }
 126   putc ('\n', fp);
 127
 128   /* Construct $port and $unixsocket. */
 129   fprintf (fp, "port=");
 130   if (port)
 131     shell_quote (port, fp);
 132   putc ('\n', fp);
 133   fprintf (fp, "unixsocket=");
 134   if (unixsocket)
 135     shell_quote (unixsocket, fp);
 136   fprintf (fp, "\n");
 137
 138   /* Add the --run command.  Note we don't have to quote this. */
 139   fprintf (fp, "%s", run);
 140
 141   if (fclose (fp) == EOF) {
 142     perror ("memstream failed");
 143     exit (EXIT_FAILURE);
 144   }
 145
 146   /* Fork.  Captive nbdkit runs as the child process. */
 147   pid = fork ();
 148   if (pid == -1) {
 149     perror ("fork");
 150     exit (EXIT_FAILURE);
 151   }
 152
 153   if (pid > 0) {              /* Parent process is the run command. */
 154     r = system (cmd);
 155     if (r == -1) {
 156       nbdkit_error ("failure to execute external command: %m");
 157       r = EXIT_FAILURE;
 158     }
 159     else if (WIFEXITED (r))
 160       r = WEXITSTATUS (r);
 161     else {
 162       assert (WIFSIGNALED (r));
 163       fprintf (stderr, "%s: external command was killed by signal %d\n",
 164                program_name, WTERMSIG (r));
 165       r = WTERMSIG (r) + 128;
 166     }
 167
 168     switch (waitpid (pid, &status, WNOHANG)) {
 169     case -1:
 170       nbdkit_error ("waitpid: %m");
 171       r = EXIT_FAILURE;
 172       break;
 173     case 0:
 174       /* Captive nbdkit still running; kill it, but no need to wait
 175        * for it, as the --run program's exit status is good enough (if
 176        * the captive nbdkit fails to exit after SIGTERM, we have a
 177        * bigger bug to fix).
 178        */
 179       kill (pid, SIGTERM);
 180       break;
 181     default:
 182       /* Captive nbdkit exited unexpectedly; update the exit status. */
 183       if (WIFEXITED (status)) {
 184         if (r == 0)
 185           r = WEXITSTATUS (status);
 186       }
 187       else {
 188         assert (WIFSIGNALED (status));
 189         fprintf (stderr, "%s: nbdkit command was killed by signal %d\n",
 190                  program_name, WTERMSIG (status));
 191         r = WTERMSIG (status) + 128;
 192       }
 193     }
 194
 195     exit (r);
 196   }
 197
 198   free (cmd);
 199
 200   debug ("forked into background (new pid = %d)", getpid ());
 201 }