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
|
/*
* daemon.c -- turn a process into a daemon under POSIX, SYSV, BSD.
*
* For license terms, see the file COPYING in this directory.
*/
#include "config.h"
#include "fetchmail.h"
#include <stdio.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <sys/stat.h> /* get umask(2) prototyped */
#include <unistd.h>
#include <stdlib.h>
#include <termios.h> /* for TIOCNOTTY under Linux */
/* BSD portability hack */
#if !defined(SIGCHLD) && defined(SIGCLD)
#define SIGCHLD SIGCLD
#endif
#include "tunable.h"
static void
sigchld_handler (int sig)
/* process SIGCHLD to obtain the exit code of the terminating process */
{
int status;
while (waitpid(-1, &status, WNOHANG) > 0)
continue; /* swallow 'em up. */
lastsig = SIGCHLD;
(void)sig;
}
void null_signal_handler(int sig) { (void)sig; }
SIGHANDLERTYPE set_signal_handler(int sig, SIGHANDLERTYPE handler)
/*
* This function is called by other parts of the program to
* setup the signal handler after a change to the signal context.
* This is done to improve robustness of the signal handling code.
* It has the same prototype as signal(2).
*/
{
SIGHANDLERTYPE rethandler;
struct sigaction sa_new, sa_old;
memset (&sa_new, 0, sizeof sa_new);
sigemptyset (&sa_new.sa_mask);
sa_new.sa_handler = handler;
sa_new.sa_flags = 0;
/* system call should restart on all signals except SIGALRM */
if (sig != SIGALRM)
sa_new.sa_flags |= SA_RESTART;
if (sig == SIGCHLD)
sa_new.sa_flags |= SA_NOCLDSTOP;
sigaction(sig, &sa_new, &sa_old);
rethandler = sa_old.sa_handler;
#if defined(SIGPWR)
if (sig == SIGCHLD)
sigaction(SIGPWR, &sa_new, NULL);
#endif
return rethandler;
}
void deal_with_sigchld(void)
{
set_signal_handler(SIGCHLD, sigchld_handler);
}
int
daemonize (const char *logfile)
/* detach from control TTY, become process group leader, catch SIGCHLD */
{
int fd, logfd;
pid_t childpid;
/* if we are started by init (process 1) via /etc/inittab we needn't
bother to detach from our process group context */
if (getppid() == 1)
goto nottyDetach;
/* Ignore BSD terminal stop signals */
#ifdef SIGTTOU
set_signal_handler(SIGTTOU, SIG_IGN);
#endif
#ifdef SIGTTIN
set_signal_handler(SIGTTIN, SIG_IGN);
#endif
#ifdef SIGTSTP
set_signal_handler(SIGTSTP, SIG_IGN);
#endif
/* In case we were not started in the background, fork and let
the parent exit. Guarantees that the child is not a process
group leader */
if ((childpid = fork()) < 0) {
report(stderr, "fork (%s)\n", strerror(errno));
return(PS_IOERR);
}
else if (childpid > 0)
exit(0); /* parent */
/* Make ourselves the leader of a new process group with no
controlling terminal */
/* POSIX makes this soooo easy to do */
if (setsid() < 0) {
report(stderr, "setsid (%s)\n", strerror(errno));
return(PS_IOERR);
}
nottyDetach:
(void)close(0);
/* Reopen stdin descriptor on /dev/null */
if (open("/dev/null", O_RDWR) < 0) { /* stdin */
report(stderr, "cannot open /dev/null: %s\n", strerror(errno));
return(PS_IOERR);
}
if (logfile)
{
if ((logfd = open(logfile, O_CREAT|O_WRONLY|O_APPEND, 0666)) < 0) { /* stdout */
report(stderr, "cannot open %s: %s\n", logfile, strerror(errno));
return PS_IOERR;
}
} else
logfd = 0; /* else use /dev/null */
/* Close any/all open file descriptors */
fd = sysconf(_SC_OPEN_MAX);
while (fd >= 1) {
if (fd != logfd)
close(fd); /* not checking this should be safe, no writes */
-- fd;
}
if (dup(logfd) < 0 /* stdout */
|| ((logfd == 0 || logfd >= 3) && dup(logfd) < 0)) { /* stderr */
report(stderr, "dup(): %s\n", strerror(errno));
return(PS_IOERR);
}
/* move to root directory, so we don't prevent filesystem unmounts */
if (chdir("/")) {
report(stderr, "chdir(\"/\"): %s\n", strerror(errno));
return PS_IOERR;
}
/* set our umask to something reasonable (we hope) */
#if defined(DEF_UMASK)
umask(DEF_UMASK);
#else
umask(022);
#endif
deal_with_sigchld();
return(0);
}
flag is_a_file(int fd)
/* is the given fd attached to a file? (used to control logging) */
{
struct stat stbuf;
/*
* We'd like just to return 1 on (S_IFREG | S_IFBLK),
* but weirdly enough, Linux ptys seem to have S_IFBLK
* so this test would fail when run on an xterm.
*/
if (isatty(fd) || fstat(fd, &stbuf))
return(0);
else if (stbuf.st_mode & (S_IFREG))
return(1);
return(0);
}
/* daemon.c ends here */
|
