81 lines
2.2 KiB
C
81 lines
2.2 KiB
C
/* vi: set sw=4 ts=4: */
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/* signalpipe.c
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*
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* Signal pipe infrastructure. A reliable way of delivering signals.
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*
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* Russ Dill <Russ.Dill@asu.edu> December 2003
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#include "common.h"
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static int signal_pipe[2];
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static void signal_handler(int sig)
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{
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unsigned char ch = sig; /* use char, avoid dealing with partial writes */
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if (write(signal_pipe[1], &ch, 1) != 1)
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bb_perror_msg("cannot send signal");
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}
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/* Call this before doing anything else. Sets up the socket pair
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* and installs the signal handler */
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void udhcp_sp_setup(void)
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{
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/* was socketpair, but it needs AF_UNIX in kernel */
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xpipe(signal_pipe);
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close_on_exec_on(signal_pipe[0]);
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close_on_exec_on(signal_pipe[1]);
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ndelay_on(signal_pipe[1]);
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signal(SIGUSR1, signal_handler);
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signal(SIGUSR2, signal_handler);
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signal(SIGTERM, signal_handler);
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}
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/* Quick little function to setup the rfds. Will return the
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* max_fd for use with select. Limited in that you can only pass
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* one extra fd */
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int udhcp_sp_fd_set(fd_set *rfds, int extra_fd)
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{
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FD_ZERO(rfds);
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FD_SET(signal_pipe[0], rfds);
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if (extra_fd >= 0) {
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close_on_exec_on(extra_fd);
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FD_SET(extra_fd, rfds);
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}
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return signal_pipe[0] > extra_fd ? signal_pipe[0] : extra_fd;
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}
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/* Read a signal from the signal pipe. Returns 0 if there is
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* no signal, -1 on error (and sets errno appropriately), and
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* your signal on success */
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int udhcp_sp_read(const fd_set *rfds)
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{
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unsigned char sig;
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if (!FD_ISSET(signal_pipe[0], rfds))
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return 0;
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if (read(signal_pipe[0], &sig, 1) != 1)
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return -1;
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return sig;
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}
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