Rename struct rc4_context and stream cipher send/receive functions.
[paraslash.git] / signal.c
1 /*
2 * Copyright (C) 2004-2011 Andre Noll <maan@systemlinux.org>
3 *
4 * Licensed under the GPL v2. For licencing details see COPYING.
5 */
6 /** \file signal.c Signal handling functions. */
7
8 #include <signal.h>
9 #include <sys/types.h>
10 #include <dirent.h>
11
12 #include "para.h"
13 #include "error.h"
14 #include "fd.h"
15
16 static int signal_pipe[2];
17
18 /**
19 * Initialize the paraslash signal subsystem.
20 *
21 * This function creates a pipe, the signal pipe, to deliver pending
22 * signals to the application (Bernstein's trick). It should be called
23 * during the application's startup part, followed by subsequent calls
24 * to para_install_sighandler() for each signal that should be caught.
25 *
26 * para_signal_init() installs a generic signal handler which is used for all
27 * signals simultaneously. When a signal arrives, this generic signal handler
28 * writes the corresponding signal number to the signal pipe so that the
29 * application can test for pending signals simply by checking the signal pipe
30 * for reading, e.g. by using the select(2) system call.
31 *
32 * \return This function either succeeds or calls exit(2) to terminate
33 * the current process. On success, the file descriptor of the signal pipe is
34 * returned.
35 */
36 int para_signal_init(void)
37 {
38 int ret;
39 if (pipe(signal_pipe) < 0) {
40 ret = -ERRNO_TO_PARA_ERROR(errno);
41 goto err_out;
42 }
43 ret = mark_fd_nonblocking(signal_pipe[0]);
44 if (ret < 0)
45 goto err_out;
46 ret = mark_fd_nonblocking(signal_pipe[1]);
47 if (ret < 0)
48 goto err_out;
49 return signal_pipe[0];
50 err_out:
51 PARA_EMERG_LOG("%s\n", para_strerror(-ret));
52 exit(EXIT_FAILURE);
53 }
54
55 /*
56 * just write one integer to signal pipe
57 */
58 static void generic_signal_handler(int s)
59 {
60 ssize_t ret = write(signal_pipe[1], &s, sizeof(int));
61
62 if (ret == sizeof(int))
63 return;
64 if (ret < 0)
65 PARA_EMERG_LOG("%s\n", strerror(errno));
66 else
67 PARA_EMERG_LOG("short write to signal pipe\n");
68 exit(EXIT_FAILURE);
69 }
70
71 /**
72 * Reap one child.
73 *
74 * \param pid In case a child died, its pid is returned here.
75 *
76 * Call waitpid() and print a log message containing the pid and the cause of
77 * the child's death.
78 *
79 * \return A (negative) paraslash error code on errors, zero, if no child died,
80 * one otherwise. If and only if the function returns one, the content of \a
81 * pid is meaningful.
82 *
83 * \sa waitpid(2).
84 */
85 int para_reap_child(pid_t *pid)
86 {
87 int status;
88 *pid = waitpid(-1, &status, WNOHANG);
89
90 if (!*pid)
91 return 0;
92 if (*pid < 0)
93 return -ERRNO_TO_PARA_ERROR(errno);
94 if (WIFEXITED(status))
95 PARA_DEBUG_LOG("child %i exited. Exit status: %i\n", (int)*pid,
96 WEXITSTATUS(status));
97 else if (WIFSIGNALED(status))
98 PARA_DEBUG_LOG("child %i was killed by signal %i\n", (int)*pid,
99 WTERMSIG(status));
100 else
101 PARA_WARNING_LOG("child %i terminated abormally\n", (int)*pid);
102 return 1;
103 }
104
105 /**
106 * Install the given handler for the given signal.
107 *
108 * \param sig The number of the signal to catch.
109 * \param handler to be installed, \p SIG_IGN, or \p SIG_DFL.
110 *
111 * This either succeeds or calls exit(EXIT_FAILURE).
112 *
113 * \sa sigaction(2).
114 */
115 void para_sigaction(int sig, void (*handler)(int))
116 {
117 struct sigaction act;
118
119 PARA_DEBUG_LOG("catching signal %d\n", sig);
120 act.sa_handler = handler;
121 sigemptyset(&act.sa_mask);
122 act.sa_flags = 0;
123 if (sig == SIGALRM) {
124 #ifdef SA_INTERRUPT /* SunOS */
125 act.sa_flags |= SA_INTERRUPT;
126 #endif
127 } else {
128 #ifdef SA_RESTART /* BSD */
129 act.sa_flags |= SA_RESTART;
130 #endif
131 }
132 if (sigaction(sig, &act, NULL) >= 0)
133 return;
134 PARA_EMERG_LOG("failed to install signal handler for signal %d\n",
135 sig);
136 exit(EXIT_FAILURE);
137 }
138
139 /**
140 * Install the generic signal handler for the given signal number.
141 *
142 * \param sig The number of the signal to catch.
143 *
144 * \sa signal(2), sigaction(2).
145 */
146 void para_install_sighandler(int sig)
147 {
148 para_sigaction(sig, &generic_signal_handler);
149 }
150
151 /**
152 * Return the number of the next pending signal.
153 *
154 * \param rfds Th fd_set containing the signal pipe.
155 *
156 * \return On success, the number of the received signal is returned. If there
157 * is no signal currently pending, the function returns zero. On read errors
158 * from the signal pipe, the process is terminated.
159 */
160 int para_next_signal(fd_set *rfds)
161 {
162 size_t n;
163 int s, ret = read_nonblock(signal_pipe[0], &s, sizeof(s), rfds, &n);
164
165 if (ret < 0) {
166 PARA_EMERG_LOG("%s\n", para_strerror(-ret));
167 exit(EXIT_FAILURE);
168 }
169 if (n == 0)
170 return 0;
171 assert(n == sizeof(s));
172 PARA_DEBUG_LOG("next signal: %d\n", s);
173 return s;
174 }
175
176 /**
177 * Close the write end of the signal pipe.
178 */
179 void para_signal_shutdown(void)
180 {
181 close(signal_pipe[1]);
182 }