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      1 /*
      2  * dhcpcd - DHCP client daemon
      3  * Copyright 2006-2008 Roy Marples <roy (at) marples.name>
      4  * All rights reserved
      5 
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     25  * SUCH DAMAGE.
     26  */
     27 
     28 #include <sys/types.h>
     29 #include <sys/socket.h>
     30 
     31 #include <errno.h>
     32 #include <signal.h>
     33 #include <string.h>
     34 #include <syslog.h>
     35 #include <unistd.h>
     36 
     37 #include "common.h"
     38 #include "signals.h"
     39 
     40 static int signal_pipe[2];
     41 
     42 static const int handle_sigs[] = {
     43 	SIGHUP,
     44 	SIGALRM,
     45 	SIGTERM,
     46 	SIGINT
     47 };
     48 
     49 static void
     50 signal_handler(int sig)
     51 {
     52 	int serrno = errno;
     53 
     54 	if (write(signal_pipe[1], &sig, sizeof(sig)) != sizeof(sig))
     55 		syslog(LOG_ERR, "write signal %d: %s", sig, strerror(errno));
     56 	/* Restore errno */
     57 	errno = serrno;
     58 }
     59 
     60 int
     61 signal_fd(void)
     62 {
     63 	return (signal_pipe[0]);
     64 }
     65 
     66 /* Read a signal from the signal pipe. Returns 0 if there is
     67  * no signal, -1 on error (and sets errno appropriately), and
     68  * your signal on success */
     69 int
     70 signal_read(void)
     71 {
     72 	int sig = -1;
     73 	char buf[16];
     74 	ssize_t bytes;
     75 
     76 	memset(buf, 0, sizeof(buf));
     77 	bytes = read(signal_pipe[0], buf, sizeof(buf));
     78 	if (bytes >= 0 && (size_t)bytes >= sizeof(sig))
     79 		memcpy(&sig, buf, sizeof(sig));
     80 	return sig;
     81 }
     82 
     83 /* Call this before doing anything else. Sets up the socket pair
     84  * and installs the signal handler */
     85 int
     86 signal_init(void)
     87 {
     88 	if (pipe(signal_pipe) == -1)
     89 		return -1;
     90 	/* Don't block on read */
     91 	if (set_nonblock(signal_pipe[0]) == -1)
     92 		return -1;
     93 	/* Stop any scripts from inheriting us */
     94 	if (set_cloexec(signal_pipe[0]) == -1)
     95 		return -1;
     96 	if (set_cloexec(signal_pipe[1]) == -1)
     97 		return -1;
     98 	return 0;
     99 }
    100 
    101 static int
    102 signal_handle(void (*func)(int))
    103 {
    104 	unsigned int i;
    105 	struct sigaction sa;
    106 
    107 	memset(&sa, 0, sizeof(sa));
    108 	sa.sa_handler = func;
    109 	sigemptyset(&sa.sa_mask);
    110 
    111 	for (i = 0; i < sizeof(handle_sigs) / sizeof(handle_sigs[0]); i++)
    112 		if (sigaction(handle_sigs[i], &sa, NULL) == -1)
    113 			return -1;
    114 	return 0;
    115 }
    116 
    117 int
    118 signal_setup(void)
    119 {
    120 	return signal_handle(signal_handler);
    121 }
    122 
    123 int
    124 signal_reset(void)
    125 {
    126 	return signal_handle(SIG_DFL);
    127 }
    128