95 lines
2.5 KiB
C
95 lines
2.5 KiB
C
/* vi: set sw=4 ts=4: */
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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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#define READ_FD 3
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#define WRITE_FD 4
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static void signal_handler(int sig)
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{
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int sv = errno;
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unsigned char ch = sig; /* use char, avoid dealing with partial writes */
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if (write(WRITE_FD, &ch, 1) != 1)
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bb_perror_msg("can't send signal");
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errno = sv;
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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 FAST_FUNC udhcp_sp_setup(void)
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{
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struct fd_pair signal_pipe;
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/* All callers also want this, so... */
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bb_sanitize_stdio();
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/* was socketpair, but it needs AF_UNIX in kernel */
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xpiped_pair(signal_pipe);
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/* usually we get fds 3 and 4, but if we get higher ones... */
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if (signal_pipe.rd != READ_FD)
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xmove_fd(signal_pipe.rd, READ_FD);
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if (signal_pipe.wr != WRITE_FD)
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xmove_fd(signal_pipe.wr, WRITE_FD);
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close_on_exec_on(READ_FD);
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close_on_exec_on(WRITE_FD);
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ndelay_on(READ_FD);
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ndelay_on(WRITE_FD);
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bb_signals(0
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+ (1 << SIGUSR1)
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+ (1 << SIGUSR2)
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+ (1 << SIGTERM)
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, signal_handler);
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}
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/* Quick little function to setup the pfds.
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* Limited in that you can only pass one extra fd.
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*/
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void FAST_FUNC udhcp_sp_fd_set(struct pollfd pfds[2], int extra_fd)
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{
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pfds[0].fd = READ_FD;
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pfds[0].events = POLLIN;
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pfds[1].fd = -1;
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if (extra_fd >= 0) {
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close_on_exec_on(extra_fd);
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pfds[1].fd = extra_fd;
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pfds[1].events = POLLIN;
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}
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/* this simplifies "is extra_fd ready?" tests elsewhere: */
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pfds[1].revents = 0;
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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 FAST_FUNC udhcp_sp_read(void)
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{
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unsigned char sig;
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/* Can't block here, fd is in nonblocking mode */
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if (safe_read(READ_FD, &sig, 1) != 1)
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return 0;
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return sig;
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}
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