/* signalpipe.c * * Signal pipe infrastructure. A reliable way of delivering signals. * * Russ Dill <Russ.Dill@asu.edu> December 2003 * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */#include <unistd.h>#include <fcntl.h>#include <signal.h>#include <sys/types.h>#include <sys/socket.h>#include <sys/select.h>#include "signalpipe.h"#include "common.h"static int signal_pipe[2];static void signal_handler(int sig){	if (send(signal_pipe[1], &sig, sizeof(sig), MSG_DONTWAIT) < 0)		DEBUG(LOG_ERR, "Could not send signal: %m");}/* Call this before doing anything else. Sets up the socket pair * and installs the signal handler */void udhcp_sp_setup(void){	socketpair(AF_UNIX, SOCK_STREAM, 0, signal_pipe);	fcntl(signal_pipe[0], F_SETFD, FD_CLOEXEC);	fcntl(signal_pipe[1], F_SETFD, FD_CLOEXEC);	signal(SIGUSR1, signal_handler);	signal(SIGUSR2, signal_handler);	signal(SIGTERM, signal_handler);}/* Quick little function to setup the rfds. Will return the * max_fd for use with select. Limited in that you can only pass * one extra fd */int udhcp_sp_fd_set(fd_set *rfds, int extra_fd){	FD_ZERO(rfds);	FD_SET(signal_pipe[0], rfds);	if (extra_fd >= 0) {		fcntl(extra_fd, F_SETFD, FD_CLOEXEC);		FD_SET(extra_fd, rfds);	}	return signal_pipe[0] > extra_fd ? signal_pipe[0] : extra_fd;}/* Read a signal from the signal pipe. Returns 0 if there is * no signal, -1 on error (and sets errno appropriately), and * your signal on success */int udhcp_sp_read(fd_set *rfds){	int sig;	if (!FD_ISSET(signal_pipe[0], rfds))		return 0;	if (read(signal_pipe[0], &sig, sizeof(sig)) < 0)		return -1;	return sig;}