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