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-rw-r--r--networking/udhcp/signalpipe.c77
1 files changed, 77 insertions, 0 deletions
diff --git a/networking/udhcp/signalpipe.c b/networking/udhcp/signalpipe.c
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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
26static int signal_pipe[2];
27
28static void signal_handler(int sig)
29{
30 if (send(signal_pipe[1], &sig, sizeof(sig), MSG_DONTWAIT) < 0)
31 bb_perror_msg("cannot send signal");
32}
33
34
35/* Call this before doing anything else. Sets up the socket pair
36 * and installs the signal handler */
37void udhcp_sp_setup(void)
38{
39 socketpair(AF_UNIX, SOCK_STREAM, 0, signal_pipe);
40 fcntl(signal_pipe[0], F_SETFD, FD_CLOEXEC);
41 fcntl(signal_pipe[1], F_SETFD, FD_CLOEXEC);
42 signal(SIGUSR1, signal_handler);
43 signal(SIGUSR2, signal_handler);
44 signal(SIGTERM, signal_handler);
45}
46
47
48/* Quick little function to setup the rfds. Will return the
49 * max_fd for use with select. Limited in that you can only pass
50 * one extra fd */
51int udhcp_sp_fd_set(fd_set *rfds, int extra_fd)
52{
53 FD_ZERO(rfds);
54 FD_SET(signal_pipe[0], rfds);
55 if (extra_fd >= 0) {
56 fcntl(extra_fd, F_SETFD, FD_CLOEXEC);
57 FD_SET(extra_fd, rfds);
58 }
59 return signal_pipe[0] > extra_fd ? signal_pipe[0] : extra_fd;
60}
61
62
63/* Read a signal from the signal pipe. Returns 0 if there is
64 * no signal, -1 on error (and sets errno appropriately), and
65 * your signal on success */
66int udhcp_sp_read(fd_set *rfds)
67{
68 int sig;
69
70 if (!FD_ISSET(signal_pipe[0], rfds))
71 return 0;
72
73 if (read(signal_pipe[0], &sig, sizeof(sig)) < 0)
74 return -1;
75
76 return sig;
77}