/* vi: set sw=4 ts=4: */ /* 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 "common.h" static int signal_pipe[2]; static void signal_handler(int sig) { if (send(signal_pipe[1], &sig, sizeof(sig), MSG_DONTWAIT) < 0) bb_perror_msg("cannot send signal"); } /* 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; }