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/**
* mds — A micro-display server
* Copyright © 2014 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "mds-base.h"
#include <libmdsserver/config.h>
#include <libmdsserver/macros.h>
#include <libmdsserver/util.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#include <signal.h>
#define try(INSTRUCTION) if ((r = INSTRUCTION)) return r
int argc;
char** argv;
int is_respawn = 0;
int is_reexec = 0;
int socket_fd = -1;
/**
* Parse command line arguments
*
* @return Non-zero on error
*/
static int parse_cmdline(void)
{
#if (LIBEXEC_ARGC_EXTRA_LIMIT < 2)
# error LIBEXEC_ARGC_EXTRA_LIMIT is too small, need at least 2.
#endif
int i;
for (i = 1; i < argc; i++)
{
char* arg = argv[i];
int v;
if ((v = strequals(arg, "--initial-spawn")) || /* Initial spawn? */
strequals(arg, "--respawn")) /* Respawning after crash? */
{
exit_if (is_respawn == v,
eprintf("conflicting arguments %s and %s cannot be combined.",
"--initial-spawn", "--respawn"););
is_respawn = !v;
}
else if (strequals(arg, "--re-exec")) /* Re-exec state-marshal. */
is_reexec = 1;
else if (startswith(arg, "--alarm=")) /* Schedule an alarm signal for forced abort. */
alarm((unsigned)min(atoi(arg + strlen("--alarm=")), 60)); /* At most 1 minute. */
}
if (is_reexec)
{
is_respawn = 1;
eprint("re-exec performed.");
}
return 0;
}
/**
* Connect to the display
*
* @return Non-zero on error
*/
static int connect_to_display(void)
{
char* display;
char pathname[PATH_MAX];
struct sockaddr_un address;
display = getenv("MDS_DISPLAY");
exit_if ((display == NULL) || (strchr(display, ':') == NULL),
eprint("MDS_DISPLAY has not set."););
exit_if (display[0] != ':',
eprint("Remote mds sessions are not supported."););
xsnprintf(pathname, "%s/%s.socket", MDS_RUNTIME_ROOT_DIRECTORY, display + 1);
address.sun_family = AF_UNIX;
strcpy(address.sun_path, pathname);
fail_if ((socket_fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0);
fail_if (connect(socket_fd, (struct sockaddr*)(&address), sizeof(address)) < 0);
return 0;
pfail:
perror(*argv);
if (socket_fd >= 0)
close(socket_fd);
return 1;
}
/**
* Entry point of the server
*
* @param argc_ Number of elements in `argv_`
* @param argv_ Command line arguments
* @return Non-zero on error
*/
int main(int argc_, char** argv_)
{
int r;
argc = argc_;
argv = argv_;
if (server_characteristics.require_privileges == 0)
/* Drop privileges like it's hot. */
fail_if (drop_privileges());
/* Sanity check the number of command line arguments. */
exit_if (argc > ARGC_LIMIT + LIBEXEC_ARGC_EXTRA_LIMIT,
eprint("that number of arguments is ridiculous, I will not allow it."););
/* Parse command line arguments. */
try (parse_cmdline());
/* Set up signal traps for all especially handled signals. */
trap_signals();
/* Connect to the display. */
if (is_reexec == 0)
try (connect_to_display());
close(socket_fd);
return 0;
pfail:
perror(*argv);
if (socket_fd >= 0)
close(socket_fd);
return 1;
}
/**
* Set up signal traps for all especially handled signals
*
* @return Non-zero on error
*/
int trap_signals(void)
{
/* Make the server update without all slaves dying on SIGUSR1. */
fail_if (xsigaction(SIGUSR1, received_reexec) < 0);
/* Implement clean exit on SIGTERM. */
fail_if (xsigaction(SIGTERM, received_terminate) < 0);
/* Implement clean exit on SIGINT. */
fail_if (xsigaction(SIGINT, received_terminate) < 0);
return 0;
pfail:
return 1;
}
#undef try
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