fixincludes/server.c

   1
   2 /*
   3  *  server.c  Set up and handle communications with a server process.
   4  *
   5  *  Server Handling copyright 1992-1999, 2001 The Free Software Foundation
   6  *
   7  *  Server Handling is free software.
   8  *  You may redistribute it and/or modify it under the terms of the
   9  *  GNU General Public License, as published by the Free Software
  10  *  Foundation; either version 2, or (at your option) any later version.
  11  *
  12  *  Server Handling is distributed in the hope that it will be useful,
  13  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  *  GNU General Public License for more details.
  16  *
  17  *  You should have received a copy of the GNU General Public License
  18  *  along with Server Handling.  See the file "COPYING".  If not,
  19  *  write to:  The Free Software Foundation, Inc.,
  20  *             51 Franklin Street, Fifth Floor,
  21  *             Boston,  MA  02110-1301, USA.
  22  *
  23  * As a special exception, The Free Software Foundation gives
  24  * permission for additional uses of the text contained in his release
  25  * of ServerHandler.
  26  *
  27  * The exception is that, if you link the ServerHandler library with other
  28  * files to produce an executable, this does not by itself cause the
  29  * resulting executable to be covered by the GNU General Public License.
  30  * Your use of that executable is in no way restricted on account of
  31  * linking the ServerHandler library code into it.
  32  *
  33  * This exception does not however invalidate any other reasons why
  34  * the executable file might be covered by the GNU General Public License.
  35  *
  36  * This exception applies only to the code released by The Free
  37  * Software Foundation under the name ServerHandler.  If you copy code
  38  * from other sources under the General Public License into a copy of
  39  * ServerHandler, as the General Public License permits, the exception
  40  * does not apply to the code that you add in this way.  To avoid
  41  * misleading anyone as to the status of such modified files, you must
  42  * delete this exception notice from them.
  43  *
  44  * If you write modifications of your own for ServerHandler, it is your
  45  * choice whether to permit this exception to apply to your modifications.
  46  * If you do not wish that, delete this exception notice.
  47  */
  48
  49 #include "fixlib.h"
  50 #include "server.h"
  51
  52 STATIC volatile enum t_bool read_pipe_timeout;
  53 STATIC pid_t server_master_pid = NOPROCESS;
  54
  55 tSCC* def_args[] =
  56 { (char *) NULL, (char *) NULL };
  57 STATIC t_pf_pair server_pair =
  58 { (FILE *) NULL, (FILE *) NULL };
  59 STATIC pid_t server_id = NULLPROCESS;
  60 /*
  61  *  Arbitrary text that should not be found in the shell output.
  62  *  It must be a single line and appear verbatim at the start of
  63  *  the terminating output line.
  64  */
  65 tSCC z_done[] = "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd";
  66 tSCC* p_cur_dir = (char *) NULL;
  67
  68 /*
  69  *  load_data
  70  *
  71  *  Read data from a file pointer (a pipe to a process in this context)
  72  *  until we either get EOF or we get a marker line back.
  73  *  The read data are stored in a malloc-ed string that is truncated
  74  *  to size at the end.  Input is assumed to be an ASCII string.
  75  */
  76 static char *
  77 load_data (FILE* fp)
  78 {
  79   char *pz_text;
  80   size_t text_size;
  81   char *pz_scan;
  82   char z_line[1024];
  83   t_bool got_done = BOOL_FALSE;
  84
  85   text_size = sizeof (z_line) * 2;
  86   pz_scan = pz_text = XNEWVEC (char, text_size);
  87
  88   for (;;)
  89     {
  90       size_t used_ct;
  91
  92       alarm (10);
  93       read_pipe_timeout = BOOL_FALSE;
  94       if (fgets (z_line, sizeof (z_line), fp) == (char *) NULL)
  95         break;
  96
  97       if (strncmp (z_line, z_done, sizeof (z_done) - 1) == 0)
  98         {
  99           got_done = BOOL_TRUE;
 100           break;
 101         }
 102
 103       strcpy (pz_scan, z_line);
 104       pz_scan += strlen (z_line);
 105       used_ct = (size_t) (pz_scan - pz_text);
 106
 107       if (text_size - used_ct < sizeof (z_line))
 108         {
 109           size_t off = (size_t) (pz_scan - pz_text);
 110
 111           text_size += 4096;
 112           pz_text = XRESIZEVEC (char, pz_text, text_size);
 113           pz_scan = pz_text + off;
 114         }
 115     }
 116
 117   alarm (0);
 118   if (read_pipe_timeout || ! got_done)
 119     {
 120       free ((void *) pz_text);
 121       return (char *) NULL;
 122     }
 123
 124   while ((pz_scan > pz_text) && ISSPACE (pz_scan[-1]))
 125     pz_scan--;
 126   *pz_scan = NUL;
 127   return XRESIZEVEC (char, pz_text, strlen (pz_text) + 1);
 128 }
 129
 130
 131 /*
 132  *  close_server
 133  *
 134  *  Make certain the server process is dead, close the
 135  *  pipes to it and from it, finally NULL out the file pointers
 136  */
 137 void
 138 close_server (void)
 139 {
 140   if (  (server_id != NULLPROCESS)
 141      && (server_master_pid == getpid ()))
 142     {
 143       kill ((pid_t) server_id, SIGKILL);
 144       server_id = NULLPROCESS;
 145       server_master_pid = NOPROCESS;
 146       fclose (server_pair.pf_read);
 147       fclose (server_pair.pf_write);
 148       server_pair.pf_read = server_pair.pf_write = (FILE *) NULL;
 149     }
 150 }
 151
 152 /*
 153  *  sig_handler really only handles the timeout and pipe signals.
 154  *  This ensures that we do not wait forever on a request
 155  *  to our server, and also that if the server dies, we do not
 156  *  die from a sigpipe problem.
 157  */
 158 static void
 159 sig_handler (int signo ATTRIBUTE_UNUSED)
 160 {
 161 #ifdef DEBUG
 162   /* FIXME: this is illegal to do in a signal handler.  */
 163   fprintf (stderr,
 164           "fixincl ERROR:  sig_handler: killed pid %ld due to %s\n",
 165           (long) server_id, signo == SIGPIPE ? "SIGPIPE" : "SIGALRM");
 166 #endif
 167   close_server ();
 168   read_pipe_timeout = BOOL_TRUE;
 169 }
 170
 171
 172 /*
 173  *  server_setup  Establish the signal handler for PIPE and ALARM.
 174  *  Also establishes the current directory to give to the
 175  *  server process at the start of every server command.
 176  */
 177 static void
 178 server_setup (void)
 179 {
 180   static int atexit_done = 0;
 181   char buff [MAXPATHLEN + 1];
 182
 183   if (atexit_done++ == 0)
 184     atexit (close_server);
 185   else
 186     fputs ("NOTE: server restarted\n", stderr);
 187
 188   server_master_pid = getpid ();
 189
 190   signal (SIGPIPE, sig_handler);
 191   signal (SIGALRM, sig_handler);
 192
 193   fputs ("trap : 1\n", server_pair.pf_write);
 194   fflush (server_pair.pf_write);
 195   getcwd (buff, MAXPATHLEN + 1);
 196   p_cur_dir = xstrdup (buff);
 197 }
 198
 199 /*
 200  *  find_shell
 201  *
 202  *  Locate a shell suitable for use.  For various reasons
 203  *  (like the use of "trap" in server_setup(), it must be a
 204  *  Bourne-like shell.
 205  *
 206  *  Most of the time, /bin/sh is preferred, but sometimes
 207  *  it's quite broken (like on Ultrix).  autoconf lets you
 208  *  override with $CONFIG_SHELL, so we do the same.
 209  */
 210
 211 static const char *
 212 find_shell (void)
 213 {
 214   char * shell = getenv ("CONFIG_SHELL");
 215   if (shell)
 216     return shell;
 217
 218   return "/bin/sh";
 219 }
 220
 221
 222 /*
 223  *  run_shell
 224  *
 225  *  Run a shell command on the server.  The command string
 226  *  passed in is wrapped inside the sequence:
 227  *
 228  *     cd <original directory>
 229  *     <command string>
 230  *     echo
 231  *     echo <end-of-command-marker>
 232  *
 233  *  This ensures that all commands start at a known place in
 234  *  the directory structure, that any incomplete output lines
 235  *  are completed and that our special marker sequence appears on
 236  *  a line by itself.  We have chosen a marker that is
 237  *  excessively unlikely to be reproduced in normal output:
 238  *
 239  *     "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd"
 240  */
 241 char *
 242 run_shell (const char* pz_cmd)
 243 {
 244   tSCC zNoServer[] = "Server not running, cannot run:\n%s\n\n";
 245   t_bool retry = BOOL_TRUE;
 246
 247  do_retry:
 248   /*  IF the shell server process is not running yet,
 249       THEN try to start it.  */
 250   if (server_id == NULLPROCESS)
 251     {
 252       def_args[0] = find_shell ();
 253
 254       server_id = proc2_fopen (&server_pair, def_args);
 255       if (server_id > 0)
 256         server_setup ();
 257     }
 258
 259   /*  IF it is still not running, THEN return the nil string.  */
 260   if (server_id <= 0)
 261     {
 262       fprintf (stderr, zNoServer, pz_cmd);
 263       return XCNEW (char);
 264     }
 265
 266   /*  Make sure the process will pay attention to us, send the
 267      supplied command, and then have it output a special marker that
 268      we can find.  */
 269   fprintf (server_pair.pf_write, "cd %s\n%s\n\necho\necho %s\n",
 270            p_cur_dir, pz_cmd, z_done);
 271   fflush (server_pair.pf_write);
 272
 273   /*  IF the server died and we received a SIGPIPE,
 274       THEN return an empty string.  */
 275   if (server_id == NULLPROCESS)
 276     {
 277       fprintf (stderr, zNoServer, pz_cmd);
 278       return XCNEW (char);
 279     }
 280
 281   /*  Now try to read back all the data.  If we fail due to either a
 282      sigpipe or sigalrm (timeout), we will return the nil string.  */
 283   {
 284     char *pz = load_data (server_pair.pf_read);
 285
 286     if (pz == (char *) NULL)
 287       {
 288         close_server ();
 289
 290         if (retry)
 291           {
 292             retry = BOOL_FALSE;
 293             goto do_retry;
 294           }
 295
 296         fprintf (stderr, "CLOSING SHELL SERVER - command failure:\n\t%s\n",
 297                  pz_cmd);
 298         pz = XCNEW (char);
 299       }
 300 #ifdef DEBUG
 301     fprintf( stderr, "run_shell command success:  %s\n", pz );
 302 #endif
 303     return pz;
 304   }
 305 }