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/*
* server.c Set up and handle communications with a server process.
*
* Server Handling copyright 1992-1999, 2001 The Free Software Foundation
*
* Server Handling is free software.
* You may redistribute it and/or modify it under the terms of the
* GNU General Public License, as published by the Free Software
* Foundation; either version 2, or (at your option) any later version.
*
* Server Handling is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Server Handling. See the file "COPYING". If not,
* write to: The Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor,
* Boston, MA 02110-1301, USA.
*
* As a special exception, The Free Software Foundation gives
* permission for additional uses of the text contained in his release
* of ServerHandler.
*
* The exception is that, if you link the ServerHandler library with other
* files to produce an executable, this does not by itself cause the
* resulting executable to be covered by the GNU General Public License.
* Your use of that executable is in no way restricted on account of
* linking the ServerHandler library code into it.
*
* This exception does not however invalidate any other reasons why
* the executable file might be covered by the GNU General Public License.
*
* This exception applies only to the code released by The Free
* Software Foundation under the name ServerHandler. If you copy code
* from other sources under the General Public License into a copy of
* ServerHandler, as the General Public License permits, the exception
* does not apply to the code that you add in this way. To avoid
* misleading anyone as to the status of such modified files, you must
* delete this exception notice from them.
*
* If you write modifications of your own for ServerHandler, it is your
* choice whether to permit this exception to apply to your modifications.
* If you do not wish that, delete this exception notice.
*/
#include "fixlib.h"
#include "server.h"
STATIC volatile enum t_bool read_pipe_timeout;
STATIC pid_t server_master_pid = NOPROCESS;
tSCC* def_args[] =
{ (char *) NULL, (char *) NULL };
STATIC t_pf_pair server_pair =
{ (FILE *) NULL, (FILE *) NULL };
STATIC pid_t server_id = NULLPROCESS;
/*
* Arbitrary text that should not be found in the shell output.
* It must be a single line and appear verbatim at the start of
* the terminating output line.
*/
tSCC z_done[] = "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd";
tSCC* p_cur_dir = (char *) NULL;
/*
* load_data
*
* Read data from a file pointer (a pipe to a process in this context)
* until we either get EOF or we get a marker line back.
* The read data are stored in a malloc-ed string that is truncated
* to size at the end. Input is assumed to be an ASCII string.
*/
static char *
load_data (FILE* fp)
{
char *pz_text;
size_t text_size;
char *pz_scan;
char z_line[1024];
t_bool got_done = BOOL_FALSE;
text_size = sizeof (z_line) * 2;
pz_scan = pz_text = XNEWVEC (char, text_size);
for (;;)
{
size_t used_ct;
alarm (10);
read_pipe_timeout = BOOL_FALSE;
if (fgets (z_line, sizeof (z_line), fp) == (char *) NULL)
break;
if (strncmp (z_line, z_done, sizeof (z_done) - 1) == 0)
{
got_done = BOOL_TRUE;
break;
}
strcpy (pz_scan, z_line);
pz_scan += strlen (z_line);
used_ct = (size_t) (pz_scan - pz_text);
if (text_size - used_ct < sizeof (z_line))
{
size_t off = (size_t) (pz_scan - pz_text);
text_size += 4096;
pz_text = XRESIZEVEC (char, pz_text, text_size);
pz_scan = pz_text + off;
}
}
alarm (0);
if (read_pipe_timeout || ! got_done)
{
free ((void *) pz_text);
return (char *) NULL;
}
while ((pz_scan > pz_text) && ISSPACE (pz_scan[-1]))
pz_scan--;
*pz_scan = NUL;
return XRESIZEVEC (char, pz_text, strlen (pz_text) + 1);
}
/*
* close_server
*
* Make certain the server process is dead, close the
* pipes to it and from it, finally NULL out the file pointers
*/
void
close_server (void)
{
if ( (server_id != NULLPROCESS)
&& (server_master_pid == getpid ()))
{
kill ((pid_t) server_id, SIGKILL);
server_id = NULLPROCESS;
server_master_pid = NOPROCESS;
fclose (server_pair.pf_read);
fclose (server_pair.pf_write);
server_pair.pf_read = server_pair.pf_write = (FILE *) NULL;
}
}
/*
* sig_handler really only handles the timeout and pipe signals.
* This ensures that we do not wait forever on a request
* to our server, and also that if the server dies, we do not
* die from a sigpipe problem.
*/
static void
sig_handler (int signo ATTRIBUTE_UNUSED)
{
#ifdef DEBUG
/* FIXME: this is illegal to do in a signal handler. */
fprintf (stderr,
"fixincl ERROR: sig_handler: killed pid %ld due to %s\n",
(long) server_id, signo == SIGPIPE ? "SIGPIPE" : "SIGALRM");
#endif
close_server ();
read_pipe_timeout = BOOL_TRUE;
}
/*
* server_setup Establish the signal handler for PIPE and ALARM.
* Also establishes the current directory to give to the
* server process at the start of every server command.
*/
static void
server_setup (void)
{
static int atexit_done = 0;
char buff [MAXPATHLEN + 1];
if (atexit_done++ == 0)
atexit (close_server);
else
fputs ("NOTE: server restarted\n", stderr);
server_master_pid = getpid ();
signal (SIGPIPE, sig_handler);
signal (SIGALRM, sig_handler);
fputs ("trap : 1\n", server_pair.pf_write);
fflush (server_pair.pf_write);
getcwd (buff, MAXPATHLEN + 1);
p_cur_dir = xstrdup (buff);
}
/*
* find_shell
*
* Locate a shell suitable for use. For various reasons
* (like the use of "trap" in server_setup(), it must be a
* Bourne-like shell.
*
* Most of the time, /bin/sh is preferred, but sometimes
* it's quite broken (like on Ultrix). autoconf lets you
* override with $CONFIG_SHELL, so we do the same.
*/
static const char *
find_shell (void)
{
char * shell = getenv ("CONFIG_SHELL");
if (shell)
return shell;
return "/bin/sh";
}
/*
* run_shell
*
* Run a shell command on the server. The command string
* passed in is wrapped inside the sequence:
*
* cd <original directory>
* <command string>
* echo
* echo <end-of-command-marker>
*
* This ensures that all commands start at a known place in
* the directory structure, that any incomplete output lines
* are completed and that our special marker sequence appears on
* a line by itself. We have chosen a marker that is
* excessively unlikely to be reproduced in normal output:
*
* "ShElL-OuTpUt-HaS-bEeN-cOmPlEtEd"
*/
char *
run_shell (const char* pz_cmd)
{
tSCC zNoServer[] = "Server not running, cannot run:\n%s\n\n";
t_bool retry = BOOL_TRUE;
do_retry:
/* IF the shell server process is not running yet,
THEN try to start it. */
if (server_id == NULLPROCESS)
{
def_args[0] = find_shell ();
server_id = proc2_fopen (&server_pair, def_args);
if (server_id > 0)
server_setup ();
}
/* IF it is still not running, THEN return the nil string. */
if (server_id <= 0)
{
fprintf (stderr, zNoServer, pz_cmd);
return XCNEW (char);
}
/* Make sure the process will pay attention to us, send the
supplied command, and then have it output a special marker that
we can find. */
fprintf (server_pair.pf_write, "cd %s\n%s\n\necho\necho %s\n",
p_cur_dir, pz_cmd, z_done);
fflush (server_pair.pf_write);
/* IF the server died and we received a SIGPIPE,
THEN return an empty string. */
if (server_id == NULLPROCESS)
{
fprintf (stderr, zNoServer, pz_cmd);
return XCNEW (char);
}
/* Now try to read back all the data. If we fail due to either a
sigpipe or sigalrm (timeout), we will return the nil string. */
{
char *pz = load_data (server_pair.pf_read);
if (pz == (char *) NULL)
{
close_server ();
if (retry)
{
retry = BOOL_FALSE;
goto do_retry;
}
fprintf (stderr, "CLOSING SHELL SERVER - command failure:\n\t%s\n",
pz_cmd);
pz = XCNEW (char);
}
#ifdef DEBUG
fprintf( stderr, "run_shell command success: %s\n", pz );
#endif
return pz;
}
}
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