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292 lines
6.4 KiB
292 lines
6.4 KiB
2 months ago
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/*
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* UCW Library -- Daemonization
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*
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* (c) 2012--2014 Martin Mares <mj@ucw.cz>
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* (c) 2014 Pavel Charvat <pchar@ucw.cz>
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*
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* This software may be freely distributed and used according to the terms
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* of the GNU Lesser General Public License.
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*/
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#include <ucw/lib.h>
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#include <ucw/daemon.h>
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#include <ucw/strtonum.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <pwd.h>
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#include <grp.h>
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#include <errno.h>
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#include <string.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <sys/file.h>
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void
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daemon_resolve_ugid(struct daemon_params *dp)
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{
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// Resolve user name
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const char *u = dp->run_as_user;
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struct passwd *pw = NULL;
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if (u)
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{
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if (u[0] == '#')
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{
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uint id;
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const char *err = str_to_uint(&id, u, NULL, 10 | STN_WHOLE);
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if (err)
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die("Cannot parse user `%s': %s", u, err);
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dp->run_as_uid = id;
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dp->want_setuid = 1;
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}
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else
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{
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pw = getpwnam(u);
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if (!pw)
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die("No such user `%s'", u);
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dp->run_as_uid = pw->pw_uid;
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dp->want_setuid = 1;
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}
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}
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// Resolve group name
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const char *g = dp->run_as_group;
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struct group *gr;
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if (g)
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{
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if (g[0] == '#')
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{
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uint id;
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const char *err = str_to_uint(&id, g, NULL, 10 | STN_WHOLE);
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if (err)
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die("Cannot parse group `%s': %s", g, err);
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dp->run_as_gid = id;
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dp->want_setgid = 1;
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}
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else
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{
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gr = getgrnam(g);
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if (!gr)
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die("No such group `%s'", g);
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dp->run_as_gid = gr->gr_gid;
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dp->want_setgid = 1;
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}
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}
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else if (pw)
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{
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dp->run_as_gid = pw->pw_gid;
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dp->want_setgid = 2;
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}
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}
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void
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daemon_switch_ugid(struct daemon_params *dp)
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{
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if (dp->want_setgid && setresgid(dp->run_as_gid, dp->run_as_gid, dp->run_as_gid) < 0)
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die("Cannot set GID to %d: %m", (int) dp->run_as_gid);
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if (dp->want_setgid > 1 && initgroups(dp->run_as_user, dp->run_as_gid) < 0)
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die("Cannot initialize groups: %m");
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if (dp->want_setuid && setresuid(dp->run_as_uid, dp->run_as_uid, dp->run_as_uid) < 0)
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die("Cannot set UID to %d: %m", (int) dp->run_as_uid);
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}
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void
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daemon_init(struct daemon_params *dp)
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{
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daemon_resolve_ugid(dp);
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if (dp->flags & DAEMON_FLAG_SIMULATE)
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return;
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if (dp->pid_file)
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{
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// Check that PID file path is absolute
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if (!(dp->flags & DAEMON_FLAG_PRESERVE_CWD) && dp->pid_file[0] != '/')
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die("Path to PID file `%s' must be absolute", dp->pid_file);
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// Open PID file
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dp->pid_fd = open(dp->pid_file, O_RDWR | O_CREAT, 0666);
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if (dp->pid_fd < 0)
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die("Cannot open `%s': %m", dp->pid_file);
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int fl = fcntl(dp->pid_fd, F_GETFD);
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if (fl < 0 || fcntl(dp->pid_fd, F_SETFD, fl | FD_CLOEXEC))
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die("Cannot set FD_CLOEXEC: %m");
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// Try to lock it with an exclusive lock
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if (flock(dp->pid_fd, LOCK_EX | LOCK_NB) < 0)
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{
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if (errno == EINTR || errno == EWOULDBLOCK)
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die("Daemon is already running (`%s' locked)", dp->pid_file);
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else
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die("Cannot lock `%s': %m", dp->pid_file);
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}
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// Make a note that the daemon is starting
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if (ftruncate(dp->pid_fd, 0) < 0 ||
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write(dp->pid_fd, "(starting)\n", 11) != 11)
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die("Error writing `%s': %m", dp->pid_file);
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}
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}
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void
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daemon_run(struct daemon_params *dp, void (*body)(struct daemon_params *dp))
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{
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if (dp->flags & DAEMON_FLAG_SIMULATE)
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{
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body(dp);
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return;
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}
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// Switch GID and UID
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daemon_switch_ugid(dp);
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// Create a new session and close stdio
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setsid();
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close(0);
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if (open("/dev/null", O_RDWR, 0) < 0 ||
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dup2(0, 1) < 0)
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die("Cannot redirect stdio to `/dev/null': %m");
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// Set umask to a reasonable value
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umask(022);
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// Do not hold the current working directory
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if (!(dp->flags & DAEMON_FLAG_PRESERVE_CWD))
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{
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if (chdir("/") < 0)
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die("Cannot chdir to root: %m");
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}
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// Create pipe to synchronize child process with master and avoid possible
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// collision between writing of PID and daemon_exit()
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int pipe_fd[2];
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if (dp->pid_file && pipe(pipe_fd) < 0)
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die("Cannot create pipe: %m");
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// Fork
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pid_t pid = fork();
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if (pid < 0)
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die("Cannot fork: %m");
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if (!pid)
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{
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// Wait for master process to finish writing of PID
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if (dp->pid_file)
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{
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byte pipe_buf[1];
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close(pipe_fd[1]);
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if (read(pipe_fd[0], pipe_buf, 1) < 0)
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die("Cannot read pipe: %m");
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close(pipe_fd[0]);
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}
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// We still keep the PID file open and thus locked
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body(dp);
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exit(0);
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}
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// Write PID
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if (dp->pid_file)
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{
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char buf[32];
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int c = snprintf(buf, sizeof(buf), "%d\n", (int) pid);
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ASSERT(c <= (int) sizeof(buf));
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if (lseek(dp->pid_fd, 0, SEEK_SET) < 0 ||
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write(dp->pid_fd, buf, c) != c ||
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ftruncate(dp->pid_fd, c) ||
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close(dp->pid_fd) < 0)
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die("Cannot write PID to `%s': %m", dp->pid_file);
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close(pipe_fd[0]);
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close(pipe_fd[1]);
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}
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}
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void
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daemon_exit(struct daemon_params *dp)
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{
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if (dp->flags & DAEMON_FLAG_SIMULATE)
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return;
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if (dp->pid_file)
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{
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if (ftruncate(dp->pid_fd, 0))
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die("Error truncating `%s': %m", dp->pid_file);
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close(dp->pid_fd);
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}
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}
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#ifdef TEST
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#include <signal.h>
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static volatile sig_atomic_t terminate;
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static void term_handler(int sig UNUSED)
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{
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msg(L_INFO | L_SIGHANDLER, "SIGTERM received, terminating in a while");
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terminate = 1;
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}
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static void hup_handler(int sig UNUSED)
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{
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msg(L_INFO | L_SIGHANDLER, "SIGHUP received");
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}
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static void body(struct daemon_params *dp)
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{
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log_fork();
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msg(L_INFO, "Daemon is running");
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msg(L_INFO, "uid=%d/%d gid=%d/%d", (int) getuid(), (int) geteuid(), (int) getgid(), (int) getegid());
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struct sigaction sa_term = { .sa_handler = term_handler };
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struct sigaction sa_hup = { .sa_handler = hup_handler };
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if (sigaction(SIGTERM, &sa_term, NULL) < 0 ||
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sigaction(SIGHUP, &sa_hup, NULL) < 0)
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ASSERT(0);
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while (!terminate)
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{
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if (!sleep(60))
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{
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msg(L_INFO, "Timeout elapsed, terminating in a while");
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break;
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}
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}
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sleep(2);
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msg(L_INFO, "Daemon is shutting down");
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daemon_exit(dp);
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}
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int main(int argc, char **argv)
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{
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struct daemon_params dp = {
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.pid_file = "/tmp/123",
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};
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int opt;
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while ((opt = getopt(argc, argv, "p:u:g:")) >= 0)
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switch (opt)
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{
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case 'p':
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dp.pid_file = optarg;
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break;
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case 'u':
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dp.run_as_user = optarg;
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break;
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case 'g':
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dp.run_as_group = optarg;
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break;
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default:
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die("Invalid arguments");
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}
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daemon_init(&dp);
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daemon_run(&dp, body);
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msg(L_INFO, "Main program has ended");
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return 0;
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}
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#endif
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