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/**
* Copyright © 2015 Mattias Andrée <maandree@member.fsf.org>
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include <unistd.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/socket.h>
/**
* The file descriptor for the socket.
*/
#define SOCK_FILENO 3
/**
* The file descriptor for the state file.
*/
#define STATE_FILENO 4
/**
* The file descriptor for connection to the current client.
*/
#define CONN_FILENO 5
/**
* Command: queue a job.
*/
#define SAT_QUEUE 0
/**
* Command: remove jobs.
*/
#define SAT_REMOVE 1
/**
* Command: print job queue.
*/
#define SAT_PRINT 2
/**
* Command: run jobs.
*/
#define SAT_RUN 3
/**
* The common beginning of for all daemon pathnames.
*/
#define DAEMON_PREFIX LIBEXEC "/" PACKAGE "/satd-"
/**
* Signal that has been received, 0 if none.
*/
static volatile sig_atomic_to received_signo = 0;
/**
* Invoked when a signal is received.
*
* @param int The signal.
*/
static void sighandler(int signo)
{
int saved_errno = errno;
switch (signo) {
case SIGCHLD:
waitpid(-1, NULL, WNOHANG);
break;
default:
received_signo = (sig_atomic_to)signo;
break;
}
errno = saved_errno;
}
/**
* The sat daemon.
*
* @param argc Should be 4.
* @param argv The name of the process, the pathname of the socket,
* the pathname to the state file, and $SAT_HOOK_PATH
* (the pathname of the hook-script.)
* @param envp The environment.
* @return 0 The process was successful.
* @return 1 The process failed queuing the job.
*/
int
main(int argc, char *argv[], char *envp[])
{
int fd = -1, rc = 0;
pid_t pid;
char type;
const char *image;
struct stat _attr;
/* Set up signal handlers. */
if (signal(SIGHUP, sighandler) == SIG_ERR) goto fail;
if (signal(SIGCHLD, sighandler) == SIG_ERR) goto fail;
/* Pick-up where we left off. */
if (!fstat(CONN_FILENO, &_attr)) {
fd = CONN_FILENO;
goto peek_again;
} else if (errno != EBADF) {
goto fail;
}
/* The magnificent loop. */
accept_again:
if (received_signo == SIGHUP) {
execve(DAEMON_PREFIX "diminished", argv, envp);
perror(argv[0]);
}
received_signo = 0;
fd = accept(SOCK_FILENO, NULL, NULL);
if (fd == -1) {
switch (errno) {
case ECONNABORTED:
case EINTR:
goto accept_again;
default:
/* Including EMFILE, ENFILE, and ENOMEM
* because of potential resource leak. */
goto fail;
}
}
if (fd != CONN_FILENO) {
if (dup2(fd, CONN_FILENO) == -1)
goto fail;
close(fd), fd = CONN_FILENO;
}
peek_again:
if (recv(fd, &type, sizeof(char), MSG_PEEK /* Just peek in case we fail! */) <= 0) {
perror(argv[0]);
goto connection_done;
}
fork_again:
switch ((pid = fork())) {
case -1:
if (errno != EAGAIN)
goto fail;
(void) sleep(1); /* Possibly shorter because of SIGCHLD. */
goto fork_again;
case 0:
switch (type) {
case SAT_QUEUE: image = DAEMON_PREFIX "add"; break;
case SAT_REMOVE: image = DAEMON_PREFIX "rm"; break;
case SAT_PRINT: image = DAEMON_PREFIX "list"; break;
case SAT_RUN: image = DAEMON_PREFIX "run"; break;
default:
fprintf(stderr, "%s: invalid command received.\n", argv[0]);
exit(1);
}
if (dup2(fd, SOCK_FILENO) != -1)
close(fd), fd = SOCK_FILENO, execve(image, argv, envp);
perror(argv[0]);
close(fd);
exit(1);
default:
break;
}
connection_done:
close(fd), fd = -1;
goto accept_again;
done:
unlink(argv[1]);
if (!rc)
unlink(argv[2]);
close(SOCK_FILENO);
close(STATE_FILENO);
return 0;
fail:
perror(argv[0]);
if (fd >= 0)
close(fd);
rc = 1;
goto done;
(void) argc;
}
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