-
Notifications
You must be signed in to change notification settings - Fork 0
/
daemonize.c
222 lines (185 loc) · 4.89 KB
/
daemonize.c
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
/*
* This code is mainly taken from Doug Potter's page
*
* http://www-theorie.physik.unizh.ch/~dpotter/howto/daemonize
*
* I contacted him 2007-04-16 about the license for the original code,
* he replied it is Public Domain. Use the URL above to get the original
* Public Domain version if you want it.
*
* This version is LGPL2 and is (c)2006 - 2013 Andy Green <andy@warmcat.com>
*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <limits.h>
#include <unistd.h>
#include <errno.h>
#include "private-libwebsockets.h"
int pid_daemon;
static char *lock_path;
int get_daemonize_pid()
{
return pid_daemon;
}
static void
child_handler(int signum)
{
int fd;
int len;
int sent;
char sz[20];
switch (signum) {
case SIGALRM: /* timedout daemonizing */
exit(1);
break;
case SIGUSR1: /* positive confirmation we daemonized well */
/* Create the lock file as the current user */
fd = open(lock_path, O_TRUNC | O_RDWR | O_CREAT, 0640);
if (fd < 0) {
fprintf(stderr,
"unable to create lock file %s, code=%d (%s)\n",
lock_path, errno, strerror(errno));
exit(1);
}
len = sprintf(sz, "%u", pid_daemon);
sent = write(fd, sz, len);
if (sent != len)
fprintf(stderr,
"unable write pid to lock file %s, code=%d (%s)\n",
lock_path, errno, strerror(errno));
close(fd);
exit(!!(sent == len));
case SIGCHLD: /* daemonization failed */
exit(1);
break;
}
}
static void lws_daemon_closing(int sigact)
{
if (getpid() == pid_daemon)
if (lock_path) {
unlink(lock_path);
free(lock_path);
lock_path = NULL;
}
kill(getpid(), SIGKILL);
}
/*
* You just need to call this from your main(), when it
* returns you are all set "in the background" decoupled
* from the console you were started from.
*
* The process context you called from has been terminated then.
*/
LWS_VISIBLE int
lws_daemonize(const char *_lock_path)
{
pid_t sid, parent;
int fd;
char buf[10];
int n, ret;
struct sigaction act;
/* already a daemon */
if (getppid() == 1)
return 1;
fd = open(_lock_path, O_RDONLY);
if (fd > 0) {
n = read(fd, buf, sizeof(buf));
close(fd);
if (n) {
n = atoi(buf);
ret = kill(n, 0);
if (ret >= 0) {
fprintf(stderr,
"Daemon already running from pid %d\n", n);
exit(1);
}
fprintf(stderr,
"Removing stale lock file %s from dead pid %d\n",
_lock_path, n);
unlink(lock_path);
}
}
n = strlen(_lock_path) + 1;
lock_path = malloc(n);
if (!lock_path) {
fprintf(stderr, "Out of mem in lws_daemonize\n");
return 1;
}
strcpy(lock_path, _lock_path);
/* Trap signals that we expect to recieve */
signal(SIGCHLD, child_handler); /* died */
signal(SIGUSR1, child_handler); /* was happy */
signal(SIGALRM, child_handler); /* timeout daemonizing */
/* Fork off the parent process */
pid_daemon = fork();
if (pid_daemon < 0) {
fprintf(stderr, "unable to fork daemon, code=%d (%s)",
errno, strerror(errno));
exit(1);
}
/* If we got a good PID, then we can exit the parent process. */
if (pid_daemon > 0) {
/*
* Wait for confirmation signal from the child via
* SIGCHILD / USR1, or for two seconds to elapse
* (SIGALRM). pause() should not return.
*/
alarm(2);
pause();
/* should not be reachable */
exit(1);
}
/* At this point we are executing as the child process */
parent = getppid();
pid_daemon = getpid();
/* Cancel certain signals */
signal(SIGCHLD, SIG_DFL); /* A child process dies */
signal(SIGTSTP, SIG_IGN); /* Various TTY signals */
signal(SIGTTOU, SIG_IGN);
signal(SIGTTIN, SIG_IGN);
signal(SIGHUP, SIG_IGN); /* Ignore hangup signal */
/* Change the file mode mask */
umask(0);
/* Create a new SID for the child process */
sid = setsid();
if (sid < 0) {
fprintf(stderr,
"unable to create a new session, code %d (%s)",
errno, strerror(errno));
exit(1);
}
/*
* Change the current working directory. This prevents the current
* directory from being locked; hence not being able to remove it.
*/
if (chdir("/") < 0) {
fprintf(stderr,
"unable to change directory to %s, code %d (%s)",
"/", errno, strerror(errno));
exit(1);
}
/* Redirect standard files to /dev/null */
if (!freopen("/dev/null", "r", stdin))
fprintf(stderr, "unable to freopen() stdin, code %d (%s)",
errno, strerror(errno));
if (!freopen("/dev/null", "w", stdout))
fprintf(stderr, "unable to freopen() stdout, code %d (%s)",
errno, strerror(errno));
if (!freopen("/dev/null", "w", stderr))
fprintf(stderr, "unable to freopen() stderr, code %d (%s)",
errno, strerror(errno));
/* Tell the parent process that we are A-okay */
kill(parent, SIGUSR1);
act.sa_handler = lws_daemon_closing;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;
sigaction(SIGTERM, &act, NULL);
/* return to continue what is now "the daemon" */
return 0;
}