networking/udhcp/signalpipe.c

/* 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 struct fd_pair signal_pipe;

static void signal_handler(int sig)
{
	unsigned char ch = sig; /* use char, avoid dealing with partial writes */
	if (write(signal_pipe.wr, &ch, 1) != 1)
		bb_perror_msg("can't send signal");
}


/* Call this before doing anything else. Sets up the socket pair
 * and installs the signal handler */
void FAST_FUNC udhcp_sp_setup(void)
{
	/* was socketpair, but it needs AF_UNIX in kernel */
	xpiped_pair(signal_pipe);
	close_on_exec_on(signal_pipe.rd);
	close_on_exec_on(signal_pipe.wr);
	ndelay_on(signal_pipe.wr);
	bb_signals(0
		+ (1 << SIGUSR1)
		+ (1 << SIGUSR2)
		+ (1 << 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 FAST_FUNC udhcp_sp_fd_set(fd_set *rfds, int extra_fd)
{
	FD_ZERO(rfds);
	FD_SET(signal_pipe.rd, rfds);
	if (extra_fd >= 0) {
		close_on_exec_on(extra_fd);
		FD_SET(extra_fd, rfds);
	}
	return signal_pipe.rd > extra_fd ? signal_pipe.rd : 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 FAST_FUNC udhcp_sp_read(const fd_set *rfds)
{
	unsigned char sig;

	if (!FD_ISSET(signal_pipe.rd, rfds))
		return 0;

	if (safe_read(signal_pipe.rd, &sig, 1) != 1)
		return -1;

	return sig;
}
1	/* vi: set sw=4 ts=4: */
2	/* signalpipe.c
3	*
4	* Signal pipe infrastructure. A reliable way of delivering signals.
5	*
6	* Russ Dill <Russ.Dill@asu.edu> December 2003
7	*
8	* This program is free software; you can redistribute it and/or modify
9	* it under the terms of the GNU General Public License as published by
10	* the Free Software Foundation; either version 2 of the License, or
11	* (at your option) any later version.
12	*
13	* This program is distributed in the hope that it will be useful,
14	* but WITHOUT ANY WARRANTY; without even the implied warranty of
15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16	* GNU General Public License for more details.
17	*
18	* You should have received a copy of the GNU General Public License
19	* along with this program; if not, write to the Free Software
20	* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21	*/
22
23	#include "common.h"
24
25
26	static struct fd_pair signal_pipe;
27
28	static void signal_handler(int sig)
29	{
30	unsigned char ch = sig; /* use char, avoid dealing with partial writes */
31	if (write(signal_pipe.wr, &ch, 1) != 1)
32	bb_perror_msg("can't send signal");
33	}
34
35
36	/* Call this before doing anything else. Sets up the socket pair
37	* and installs the signal handler */
38	void FAST_FUNC udhcp_sp_setup(void)
39	{
40	/* was socketpair, but it needs AF_UNIX in kernel */
41	xpiped_pair(signal_pipe);
42	close_on_exec_on(signal_pipe.rd);
43	close_on_exec_on(signal_pipe.wr);
44	ndelay_on(signal_pipe.wr);
45	bb_signals(0
46	+ (1 << SIGUSR1)
47	+ (1 << SIGUSR2)
48	+ (1 << SIGTERM)
49	, signal_handler);
50	}
51
52
53	/* Quick little function to setup the rfds. Will return the
54	* max_fd for use with select. Limited in that you can only pass
55	* one extra fd */
56	int FAST_FUNC udhcp_sp_fd_set(fd_set *rfds, int extra_fd)
57	{
58	FD_ZERO(rfds);
59	FD_SET(signal_pipe.rd, rfds);
60	if (extra_fd >= 0) {
61	close_on_exec_on(extra_fd);
62	FD_SET(extra_fd, rfds);
63	}
64	return signal_pipe.rd > extra_fd ? signal_pipe.rd : extra_fd;
65	}
66
67
68	/* Read a signal from the signal pipe. Returns 0 if there is
69	* no signal, -1 on error (and sets errno appropriately), and
70	* your signal on success */
71	int FAST_FUNC udhcp_sp_read(const fd_set *rfds)
72	{
73	unsigned char sig;
74
75	if (!FD_ISSET(signal_pipe.rd, rfds))
76	return 0;
77
78	if (safe_read(signal_pipe.rd, &sig, 1) != 1)
79	return -1;
80
81	return sig;
82	}