xref: /minix3/external/bsd/tcpdump/dist/setsignal.c (revision b636d99d91c3d54204248f643c14627405d4afd1)
1*b636d99dSDavid van Moolenbroek /*
2*b636d99dSDavid van Moolenbroek  * Copyright (c) 1997
3*b636d99dSDavid van Moolenbroek  *	The Regents of the University of California.  All rights reserved.
4*b636d99dSDavid van Moolenbroek  *
5*b636d99dSDavid van Moolenbroek  * Redistribution and use in source and binary forms, with or without
6*b636d99dSDavid van Moolenbroek  * modification, are permitted provided that: (1) source code distributions
7*b636d99dSDavid van Moolenbroek  * retain the above copyright notice and this paragraph in its entirety, (2)
8*b636d99dSDavid van Moolenbroek  * distributions including binary code include the above copyright notice and
9*b636d99dSDavid van Moolenbroek  * this paragraph in its entirety in the documentation or other materials
10*b636d99dSDavid van Moolenbroek  * provided with the distribution, and (3) all advertising materials mentioning
11*b636d99dSDavid van Moolenbroek  * features or use of this software display the following acknowledgement:
12*b636d99dSDavid van Moolenbroek  * ``This product includes software developed by the University of California,
13*b636d99dSDavid van Moolenbroek  * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
14*b636d99dSDavid van Moolenbroek  * the University nor the names of its contributors may be used to endorse
15*b636d99dSDavid van Moolenbroek  * or promote products derived from this software without specific prior
16*b636d99dSDavid van Moolenbroek  * written permission.
17*b636d99dSDavid van Moolenbroek  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
18*b636d99dSDavid van Moolenbroek  * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
19*b636d99dSDavid van Moolenbroek  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
20*b636d99dSDavid van Moolenbroek  */
21*b636d99dSDavid van Moolenbroek 
22*b636d99dSDavid van Moolenbroek #include <sys/cdefs.h>
23*b636d99dSDavid van Moolenbroek #ifndef lint
24*b636d99dSDavid van Moolenbroek __RCSID("$NetBSD: setsignal.c,v 1.5 2014/11/20 03:05:03 christos Exp $");
25*b636d99dSDavid van Moolenbroek #endif
26*b636d99dSDavid van Moolenbroek 
27*b636d99dSDavid van Moolenbroek #ifdef HAVE_CONFIG_H
28*b636d99dSDavid van Moolenbroek #include "config.h"
29*b636d99dSDavid van Moolenbroek #endif
30*b636d99dSDavid van Moolenbroek 
31*b636d99dSDavid van Moolenbroek #include <tcpdump-stdinc.h>
32*b636d99dSDavid van Moolenbroek 
33*b636d99dSDavid van Moolenbroek #include <signal.h>
34*b636d99dSDavid van Moolenbroek #ifdef HAVE_SIGACTION
35*b636d99dSDavid van Moolenbroek #include <string.h>
36*b636d99dSDavid van Moolenbroek #endif
37*b636d99dSDavid van Moolenbroek 
38*b636d99dSDavid van Moolenbroek #ifdef HAVE_OS_PROTO_H
39*b636d99dSDavid van Moolenbroek #include "os-proto.h"
40*b636d99dSDavid van Moolenbroek #endif
41*b636d99dSDavid van Moolenbroek 
42*b636d99dSDavid van Moolenbroek #include "setsignal.h"
43*b636d99dSDavid van Moolenbroek 
44*b636d99dSDavid van Moolenbroek /*
45*b636d99dSDavid van Moolenbroek  * An OS-independent signal() with, whenever possible, partial BSD
46*b636d99dSDavid van Moolenbroek  * semantics, i.e. the signal handler is restored following service
47*b636d99dSDavid van Moolenbroek  * of the signal, but system calls are *not* restarted, so that if
48*b636d99dSDavid van Moolenbroek  * "pcap_breakloop()" is called in a signal handler in a live capture,
49*b636d99dSDavid van Moolenbroek  * the read/recvfrom/whatever in the live capture doesn't get restarted,
50*b636d99dSDavid van Moolenbroek  * it returns -1 and sets "errno" to EINTR, so we can break out of the
51*b636d99dSDavid van Moolenbroek  * live capture loop.
52*b636d99dSDavid van Moolenbroek  *
53*b636d99dSDavid van Moolenbroek  * We use "sigaction()" if available.  We don't specify that the signal
54*b636d99dSDavid van Moolenbroek  * should restart system calls, so that should always do what we want.
55*b636d99dSDavid van Moolenbroek  *
56*b636d99dSDavid van Moolenbroek  * Otherwise, if "sigset()" is available, it probably has BSD semantics
57*b636d99dSDavid van Moolenbroek  * while "signal()" has traditional semantics, so we use "sigset()"; it
58*b636d99dSDavid van Moolenbroek  * might cause system calls to be restarted for the signal, however.
59*b636d99dSDavid van Moolenbroek  * I don't know whether, in any systems where it did cause system calls to
60*b636d99dSDavid van Moolenbroek  * be restarted, there was a way to ask it not to do so; there may no
61*b636d99dSDavid van Moolenbroek  * longer be any interesting systems without "sigaction()", however,
62*b636d99dSDavid van Moolenbroek  * and, if there are, they might have "sigvec()" with SV_INTERRUPT
63*b636d99dSDavid van Moolenbroek  * (which I think first appeared in 4.3BSD).
64*b636d99dSDavid van Moolenbroek  *
65*b636d99dSDavid van Moolenbroek  * Otherwise, we use "signal()" - which means we might get traditional
66*b636d99dSDavid van Moolenbroek  * semantics, wherein system calls don't get restarted *but* the
67*b636d99dSDavid van Moolenbroek  * signal handler is reset to SIG_DFL and the signal is not blocked,
68*b636d99dSDavid van Moolenbroek  * so that a subsequent signal would kill the process immediately.
69*b636d99dSDavid van Moolenbroek  *
70*b636d99dSDavid van Moolenbroek  * Did I mention that signals suck?  At least in POSIX-compliant systems
71*b636d99dSDavid van Moolenbroek  * they suck far less, as those systems have "sigaction()".
72*b636d99dSDavid van Moolenbroek  */
73*b636d99dSDavid van Moolenbroek RETSIGTYPE
setsignal(int sig,RETSIGTYPE (* func)(int))74*b636d99dSDavid van Moolenbroek (*setsignal (int sig, RETSIGTYPE (*func)(int)))(int)
75*b636d99dSDavid van Moolenbroek {
76*b636d99dSDavid van Moolenbroek #ifdef HAVE_SIGACTION
77*b636d99dSDavid van Moolenbroek 	struct sigaction old, new;
78*b636d99dSDavid van Moolenbroek 
79*b636d99dSDavid van Moolenbroek 	memset(&new, 0, sizeof(new));
80*b636d99dSDavid van Moolenbroek 	new.sa_handler = func;
81*b636d99dSDavid van Moolenbroek 	if (sig == SIGCHLD)
82*b636d99dSDavid van Moolenbroek 		new.sa_flags = SA_RESTART;
83*b636d99dSDavid van Moolenbroek 	if (sigaction(sig, &new, &old) < 0)
84*b636d99dSDavid van Moolenbroek 		return (SIG_ERR);
85*b636d99dSDavid van Moolenbroek 	return (old.sa_handler);
86*b636d99dSDavid van Moolenbroek 
87*b636d99dSDavid van Moolenbroek #else
88*b636d99dSDavid van Moolenbroek #ifdef HAVE_SIGSET
89*b636d99dSDavid van Moolenbroek 	return (sigset(sig, func));
90*b636d99dSDavid van Moolenbroek #else
91*b636d99dSDavid van Moolenbroek 	return (signal(sig, func));
92*b636d99dSDavid van Moolenbroek #endif
93*b636d99dSDavid van Moolenbroek #endif
94*b636d99dSDavid van Moolenbroek }
95*b636d99dSDavid van Moolenbroek 
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