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