1 /*
2 * This code is mainly taken from Doug Potter's page
3 *
4 * http://www-theorie.physik.unizh.ch/~dpotter/howto/daemonize
5 *
6 * I contacted him 2007-04-16 about the license for the original code,
7 * he replied it is Public Domain. Use the URL above to get the original
8 * Public Domain version if you want it.
9 *
10 * This version is MIT like the rest of libwebsockets and is
11 * Copyright (c)2006 - 2013 Andy Green <andy@warmcat.com>
12 *
13 *
14 * You're much better advised to use systemd to daemonize stuff without needing
15 * this kind of support in the app itself.
16 */
17
18 #include <stdlib.h>
19 #include <string.h>
20 #include <stdio.h>
21 #include <signal.h>
22 #include <sys/types.h>
23 #include <sys/stat.h>
24 #include <fcntl.h>
25 #include <limits.h>
26 #include <unistd.h>
27 #include <errno.h>
28
29 #include <libwebsockets.h>
30 #include "private-lib-core.h"
31
32 pid_t pid_daemon;
33 static char *lock_path;
34
get_daemonize_pid()35 pid_t get_daemonize_pid()
36 {
37 return pid_daemon;
38 }
39
40 static void
child_handler(int signum)41 child_handler(int signum)
42 {
43 int len, sent, fd;
44 char sz[20];
45
46 switch (signum) {
47
48 case SIGALRM: /* timed out daemonizing */
49 exit(0);
50 break;
51
52 case SIGUSR1: /* positive confirmation we daemonized well */
53
54 if (!lock_path)
55 exit(0);
56
57 /* Create the lock file as the current user */
58
59 fd = lws_open(lock_path, O_TRUNC | O_RDWR | O_CREAT, 0640);
60 if (fd < 0) {
61 fprintf(stderr,
62 "unable to create lock file %s, code=%d (%s)\n",
63 lock_path, errno, strerror(errno));
64 exit(0);
65 }
66 len = sprintf(sz, "%u", (unsigned int)pid_daemon);
67 sent = (int)write(fd, sz, (size_t)len);
68 if (sent != len)
69 fprintf(stderr,
70 "unable to write pid to lock file %s, code=%d (%s)\n",
71 lock_path, errno, strerror(errno));
72
73 close(fd);
74
75 exit(0);
76 //!!(sent == len));
77
78 case SIGCHLD: /* daemonization failed */
79 exit(0);
80 break;
81 }
82 }
83
lws_daemon_closing(int sigact)84 static void lws_daemon_closing(int sigact)
85 {
86 if (getpid() == pid_daemon)
87 if (lock_path) {
88 unlink(lock_path);
89 lws_free_set_NULL(lock_path);
90 }
91
92 kill(getpid(), SIGKILL);
93 }
94
95 /*
96 * You just need to call this from your main(), when it
97 * returns you are all set "in the background" decoupled
98 * from the console you were started from.
99 *
100 * The process context you called from has been terminated then.
101 */
102
103 int
lws_daemonize(const char * _lock_path)104 lws_daemonize(const char *_lock_path)
105 {
106 struct sigaction act;
107 pid_t sid, parent;
108
109 /* already a daemon */
110 // if (getppid() == 1)
111 // return 1;
112
113 if (_lock_path) {
114 int n;
115
116 int fd = lws_open(_lock_path, O_RDONLY);
117 if (fd >= 0) {
118 char buf[10];
119
120 n = (int)read(fd, buf, sizeof(buf));
121 close(fd);
122 if (n) {
123 int ret;
124 n = atoi(buf);
125 ret = kill(n, 0);
126 if (ret >= 0) {
127 fprintf(stderr,
128 "Daemon already running pid %d\n",
129 n);
130 exit(1);
131 }
132 fprintf(stderr,
133 "Removing stale lock %s from dead pid %d\n",
134 _lock_path, n);
135 unlink(lock_path);
136 }
137 }
138
139 n = (int)strlen(_lock_path) + 1;
140 lock_path = lws_malloc((unsigned int)n, "daemonize lock");
141 if (!lock_path) {
142 fprintf(stderr, "Out of mem in lws_daemonize\n");
143 return 1;
144 }
145 strcpy(lock_path, _lock_path);
146 }
147
148 /* Trap signals that we expect to receive */
149 signal(SIGCHLD, child_handler); /* died */
150 signal(SIGUSR1, child_handler); /* was happy */
151 signal(SIGALRM, child_handler); /* timeout daemonizing */
152
153 /* Fork off the parent process */
154 pid_daemon = fork();
155 if ((int)pid_daemon < 0) {
156 fprintf(stderr, "unable to fork daemon, code=%d (%s)",
157 errno, strerror(errno));
158 exit(9);
159 }
160
161 /* If we got a good PID, then we can exit the parent process. */
162 if (pid_daemon > 0) {
163
164 /*
165 * Wait for confirmation signal from the child via
166 * SIGCHILD / USR1, or for two seconds to elapse
167 * (SIGALRM). pause() should not return.
168 */
169 alarm(2);
170
171 pause();
172 /* should not be reachable */
173 exit(1);
174 }
175
176 /* At this point we are executing as the child process */
177 parent = getppid();
178 pid_daemon = getpid();
179
180 /* Cancel certain signals */
181 signal(SIGCHLD, SIG_DFL); /* A child process dies */
182 signal(SIGTSTP, SIG_IGN); /* Various TTY signals */
183 signal(SIGTTOU, SIG_IGN);
184 signal(SIGTTIN, SIG_IGN);
185 signal(SIGHUP, SIG_IGN); /* Ignore hangup signal */
186
187 /* Change the file mode mask */
188 umask(0);
189
190 /* Create a new SID for the child process */
191 sid = setsid();
192 if (sid < 0) {
193 fprintf(stderr,
194 "unable to create a new session, code %d (%s)",
195 errno, strerror(errno));
196 exit(2);
197 }
198
199 /*
200 * Change the current working directory. This prevents the current
201 * directory from being locked; hence not being able to remove it.
202 */
203 if (chdir("/tmp") < 0) {
204 fprintf(stderr,
205 "unable to change directory to %s, code %d (%s)",
206 "/", errno, strerror(errno));
207 exit(3);
208 }
209
210 /* Redirect standard files to /dev/null */
211 if (!freopen("/dev/null", "r", stdin))
212 fprintf(stderr, "unable to freopen() stdin, code %d (%s)",
213 errno, strerror(errno));
214
215 if (!freopen("/dev/null", "w", stdout))
216 fprintf(stderr, "unable to freopen() stdout, code %d (%s)",
217 errno, strerror(errno));
218
219 if (!freopen("/dev/null", "w", stderr))
220 fprintf(stderr, "unable to freopen() stderr, code %d (%s)",
221 errno, strerror(errno));
222
223 /* Tell the parent process that we are A-okay */
224 kill(parent, SIGUSR1);
225
226 act.sa_handler = lws_daemon_closing;
227 sigemptyset(&act.sa_mask);
228 act.sa_flags = 0;
229
230 sigaction(SIGTERM, &act, NULL);
231
232 /* return to continue what is now "the daemon" */
233
234 return 0;
235 }
236
237