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/*
* Copyright (c) 1997
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that: (1) source code distributions
* retain the above copyright notice and this paragraph in its entirety, (2)
* distributions including binary code include the above copyright notice and
* this paragraph in its entirety in the documentation or other materials
* provided with the distribution, and (3) all advertising materials mentioning
* features or use of this software display the following acknowledgement:
* ``This product includes software developed by the University of California,
* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
* the University nor the names of its contributors may be used to endorse
* or promote products derived from this software without specific prior
* written permission.
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
*/
#ifndef lint
static const char rcsid[] _U_ =
"@(#) $Header: /tcpdump/master/tcpdump/setsignal.c,v 1.11 2003-11-16 09:36:42 guy Exp $ (LBL)";
#endif
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <tcpdump-stdinc.h>
#include <signal.h>
#ifdef HAVE_SIGACTION
#include <string.h>
#endif
#ifdef HAVE_OS_PROTO_H
#include "os-proto.h"
#endif
#ifdef HAVE_SIGSET
void *sigset(int signum, void (*handler)(int));
#endif
#include "setsignal.h"
/*
* An OS-independent signal() with, whenever possible, partial BSD
* semantics, i.e. the signal handler is restored following service
* of the signal, but system calls are *not* restarted, so that if
* "pcap_breakloop()" is called in a signal handler in a live capture,
* the read/recvfrom/whatever in the live capture doesn't get restarted,
* it returns -1 and sets "errno" to EINTR, so we can break out of the
* live capture loop.
*
* We use "sigaction()" if available. We don't specify that the signal
* should restart system calls, so that should always do what we want.
*
* Otherwise, if "sigset()" is available, it probably has BSD semantics
* while "signal()" has traditional semantics, so we use "sigset()"; it
* might cause system calls to be restarted for the signal, however.
* I don't know whether, in any systems where it did cause system calls to
* be restarted, there was a way to ask it not to do so; there may no
* longer be any interesting systems without "sigaction()", however,
* and, if there are, they might have "sigvec()" with SV_INTERRUPT
* (which I think first appeared in 4.3BSD).
*
* Otherwise, we use "signal()" - which means we might get traditional
* semantics, wherein system calls don't get restarted *but* the
* signal handler is reset to SIG_DFL and the signal is not blocked,
* so that a subsequent signal would kill the process immediately.
*
* Did I mention that signals suck? At least in POSIX-compliant systems
* they suck far less, as those systems have "sigaction()".
*/
RETSIGTYPE
(*setsignal (int sig, RETSIGTYPE (*func)(int)))(int)
{
#ifdef HAVE_SIGACTION
struct sigaction old, new;
memset(&new, 0, sizeof(new));
new.sa_handler = func;
if (sigaction(sig, &new, &old) < 0)
return (SIG_ERR);
return (old.sa_handler);
#else
#ifdef HAVE_SIGSET
return (sigset(sig, func));
#else
return (signal(sig, func));
#endif
#endif
}
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