| /* 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; |
| } |