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 *             59 Temple Place - Suite 330,
21 *             Boston,  MA  02111-1307, 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#include "auto-host.h"
49
50#include "ansidecl.h"
51#include "system.h"
52#include <signal.h>
53
54#include "server.h"
55
56#if !defined(volatile) && !defined(HAVE_VOLATILE)
57# define volatile
58#endif
59
60STATIC volatile enum t_bool read_pipe_timeout;
61STATIC pid_t server_master_pid = NOPROCESS;
62
63tSCC* def_args[] =
64{ (char *) NULL, (char *) NULL };
65STATIC t_pf_pair server_pair =
66{ (FILE *) NULL, (FILE *) NULL };
67STATIC pid_t server_id = NULLPROCESS;
68/*
69 *  Arbitrary text that should not be found in the shell output.
70 *  It must be a single line and appear verbatim at the start of
71 *  the terminating output line.
72 */
73tSCC z_done[] = "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd";
74tSCC* p_cur_dir = (char *) NULL;
75
76/*
77 *  load_data
78 *
79 *  Read data from a file pointer (a pipe to a process in this context)
80 *  until we either get EOF or we get a marker line back.
81 *  The read data are stored in a malloc-ed string that is truncated
82 *  to size at the end.  Input is assumed to be an ASCII string.
83 */
84static char *load_data PARAMS ((FILE *));
85static char *
86load_data (fp)
87     FILE *fp;
88{
89  char *pz_text;
90  size_t text_size;
91  char *pz_scan;
92  char z_line[1024];
93  t_bool got_done = BOOL_FALSE;
94
95  text_size = sizeof (z_line) * 2;
96  pz_scan = pz_text = xmalloc (text_size);
97
98  for (;;)
99    {
100      size_t used_ct;
101
102      alarm (10);
103      read_pipe_timeout = BOOL_FALSE;
104      if (fgets (z_line, sizeof (z_line), fp) == (char *) NULL)
105        break;
106
107      if (strncmp (z_line, z_done, sizeof (z_done) - 1) == 0)
108	{
109	  got_done = BOOL_TRUE;
110	  break;
111	}
112
113      strcpy (pz_scan, z_line);
114      pz_scan += strlen (z_line);
115      used_ct = (size_t) (pz_scan - pz_text);
116
117      if (text_size - used_ct < sizeof (z_line))
118        {
119          size_t off = (size_t) (pz_scan - pz_text);
120
121          text_size += 4096;
122          pz_text = xrealloc ((void *) pz_text, text_size);
123          pz_scan = pz_text + off;
124        }
125    }
126
127  alarm (0);
128  if (read_pipe_timeout || ! got_done)
129    {
130      free ((void *) pz_text);
131      return (char *) NULL;
132    }
133
134  while ((pz_scan > pz_text) && ISSPACE (pz_scan[-1]))
135    pz_scan--;
136  *pz_scan = NUL;
137  return xrealloc ((void *) pz_text, strlen (pz_text) + 1);
138}
139
140
141/*
142 *  close_server
143 *
144 *  Make certain the server process is dead, close the
145 *  pipes to it and from it, finally NULL out the file pointers
146 */
147void
148close_server ()
149{
150  if (  (server_id != NULLPROCESS)
151     && (server_master_pid == getpid ()))
152    {
153      kill ((pid_t) server_id, SIGKILL);
154      server_id = NULLPROCESS;
155      server_master_pid = NOPROCESS;
156      fclose (server_pair.pf_read);
157      fclose (server_pair.pf_write);
158      server_pair.pf_read = server_pair.pf_write = (FILE *) NULL;
159    }
160}
161
162/*
163 *  sig_handler really only handles the timeout and pipe signals.
164 *  This ensures that we do not wait forever on a request
165 *  to our server, and also that if the server dies, we do not
166 *  die from a sigpipe problem.
167 */
168static void sig_handler PARAMS ((int));
169static void
170sig_handler (signo)
171     int signo ATTRIBUTE_UNUSED;
172{
173#ifdef DEBUG
174  /* FIXME: this is illegal to do in a signal handler.  */
175  fprintf (stderr,
176          "fixincl ERROR:  sig_handler: killed pid %ld due to %s\n",
177          (long) server_id, signo == SIGPIPE ? "SIGPIPE" : "SIGALRM");
178#endif
179  close_server ();
180  read_pipe_timeout = BOOL_TRUE;
181}
182
183
184/*
185 *  server_setup  Establish the signal handler for PIPE and ALARM.
186 *  Also establishes the current directory to give to the
187 *  server process at the start of every server command.
188 */
189static void server_setup PARAMS ((void));
190static void
191server_setup ()
192{
193  static int atexit_done = 0;
194
195  if (atexit_done++ == 0)
196    atexit (close_server);
197  else
198    fputs ("NOTE: server restarted\n", stderr);
199
200  server_master_pid = getpid ();
201
202  signal (SIGPIPE, sig_handler);
203  signal (SIGALRM, sig_handler);
204
205  fputs ("trap : 1\n", server_pair.pf_write);
206  fflush (server_pair.pf_write);
207  p_cur_dir = getcwd ((char *) NULL, MAXPATHLEN + 1);
208}
209
210/*
211 *  find_shell
212 *
213 *  Locate a shell suitable for use.  For various reasons
214 *  (like the use of "trap" in server_setup(), it must be a
215 *  Bourne-like shell.
216 *
217 *  Most of the time, /bin/sh is preferred, but sometimes
218 *  it's quite broken (like on Ultrix).  autoconf lets you
219 *  override with $CONFIG_SHELL, so we do the same.
220 */
221
222static const char *find_shell PARAMS ((void));
223static const char *
224find_shell ()
225{
226  char * shell = getenv ("CONFIG_SHELL");
227  if (shell)
228    return shell;
229
230  return "/bin/sh";
231}
232
233
234/*
235 *  run_shell
236 *
237 *  Run a shell command on the server.  The command string
238 *  passed in is wrapped inside the sequence:
239 *
240 *     cd <original directory>
241 *     <command string>
242 *     echo
243 *     echo <end-of-command-marker>
244 *
245 *  This ensures that all commands start at a known place in
246 *  the directory structure, that any incomplete output lines
247 *  are completed and that our special marker sequence appears on
248 *  a line by itself.  We have chosen a marker that is
249 *  excessively unlikely to be reproduced in normal output:
250 *
251 *     "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd"
252 */
253char *
254run_shell (pz_cmd)
255     const char *pz_cmd;
256{
257  tSCC zNoServer[] = "Server not running, cannot run:\n%s\n\n";
258  t_bool retry = BOOL_TRUE;
259
260 do_retry:
261  /*  IF the shell server process is not running yet,
262      THEN try to start it.  */
263  if (server_id == NULLPROCESS)
264    {
265      def_args[0] = find_shell ();
266
267      server_id = proc2_fopen (&server_pair, def_args);
268      if (server_id > 0)
269        server_setup ();
270    }
271
272  /*  IF it is still not running, THEN return the nil string.  */
273  if (server_id <= 0)
274    {
275      fprintf (stderr, zNoServer, pz_cmd);
276      return xcalloc (1, 1);
277    }
278
279  /*  Make sure the process will pay attention to us, send the
280     supplied command, and then have it output a special marker that
281     we can find.  */
282  fprintf (server_pair.pf_write, "cd %s\n%s\n\necho\necho %s\n",
283           p_cur_dir, pz_cmd, z_done);
284  fflush (server_pair.pf_write);
285
286  /*  IF the server died and we received a SIGPIPE,
287      THEN return an empty string.  */
288  if (server_id == NULLPROCESS)
289    {
290      fprintf (stderr, zNoServer, pz_cmd);
291      return xcalloc (1, 1);
292    }
293
294  /*  Now try to read back all the data.  If we fail due to either a
295     sigpipe or sigalrm (timeout), we will return the nil string.  */
296  {
297    char *pz = load_data (server_pair.pf_read);
298
299    if (pz == (char *) NULL)
300      {
301	close_server ();
302
303	if (retry)
304	  {
305	    retry = BOOL_FALSE;
306	    goto do_retry;
307	  }
308
309        fprintf (stderr, "CLOSING SHELL SERVER - command failure:\n\t%s\n",
310                 pz_cmd);
311        pz = xcalloc (1, 1);
312      }
313#ifdef DEBUG
314    fprintf( stderr, "run_shell command success:  %s\n", pz );
315#endif
316    return pz;
317  }
318}
319