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/* 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)
{
unsigned char ch = sig; /* use char, avoid dealing with partial writes */
if (write(signal_pipe[1], &ch, 1) != 1)
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)
{
/* was socketpair, but it needs AF_UNIX in kernel */
xpipe(signal_pipe);
fcntl(signal_pipe[0], F_SETFD, FD_CLOEXEC);
fcntl(signal_pipe[1], F_SETFD, FD_CLOEXEC);
fcntl(signal_pipe[1], F_SETFL, O_NONBLOCK);
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)
{
unsigned char sig;
if (!FD_ISSET(signal_pipe[0], rfds))
return 0;
if (read(signal_pipe[0], &sig, 1) != 1)
return -1;
return sig;
}
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