94 lines
3.4 KiB
C
94 lines
3.4 KiB
C
/*
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* Copyright (c) 1997
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that: (1) source code distributions
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* retain the above copyright notice and this paragraph in its entirety, (2)
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* distributions including binary code include the above copyright notice and
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* this paragraph in its entirety in the documentation or other materials
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* provided with the distribution, and (3) all advertising materials mentioning
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* features or use of this software display the following acknowledgement:
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* ``This product includes software developed by the University of California,
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* Lawrence Berkeley Laboratory and its contributors.'' Neither the name of
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* the University nor the names of its contributors may be used to endorse
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* or promote products derived from this software without specific prior
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* written permission.
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* THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
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* WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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*/
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#ifndef lint
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static const char rcsid[] _U_ =
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"@(#) $Header: /tcpdump/master/tcpdump/setsignal.c,v 1.9.2.2 2003/11/16 08:51:56 guy Exp $ (LBL)";
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#endif
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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include <tcpdump-stdinc.h>
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#include <signal.h>
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#ifdef HAVE_SIGACTION
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#include <string.h>
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#endif
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#ifdef HAVE_OS_PROTO_H
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#include "os-proto.h"
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#endif
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#include "setsignal.h"
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/*
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* An OS-independent signal() with, whenever possible, partial BSD
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* semantics, i.e. the signal handler is restored following service
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* of the signal, but system calls are *not* restarted, so that if
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* "pcap_breakloop()" is called in a signal handler in a live capture,
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* the read/recvfrom/whatever in the live capture doesn't get restarted,
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* it returns -1 and sets "errno" to EINTR, so we can break out of the
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* live capture loop.
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*
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* We use "sigaction()" if available. We don't specify that the signal
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* should restart system calls, so that should always do what we want.
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*
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* Otherwise, if "sigset()" is available, it probably has BSD semantics
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* while "signal()" has traditional semantics, so we use "sigset()"; it
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* might cause system calls to be restarted for the signal, however.
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* I don't know whether, in any systems where it did cause system calls to
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* be restarted, there was a way to ask it not to do so; there may no
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* longer be any interesting systems without "sigaction()", however,
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* and, if there are, they might have "sigvec()" with SV_INTERRUPT
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* (which I think first appeared in 4.3BSD).
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*
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* Otherwise, we use "signal()" - which means we might get traditional
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* semantics, wherein system calls don't get restarted *but* the
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* signal handler is reset to SIG_DFL and the signal is not blocked,
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* so that a subsequent signal would kill the process immediately.
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*
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* Did I mention that signals suck? At least in POSIX-compliant systems
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* they suck far less, as those systems have "sigaction()".
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*/
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RETSIGTYPE
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(*setsignal (int sig, RETSIGTYPE (*func)(int)))(int)
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{
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#ifdef HAVE_SIGACTION
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struct sigaction old, new;
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memset(&new, 0, sizeof(new));
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new.sa_handler = func;
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if (sigaction(sig, &new, &old) < 0)
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return (SIG_ERR);
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return (old.sa_handler);
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#else
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#ifdef HAVE_SIGSET
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return (sigset(sig, func));
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#else
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return (signal(sig, func));
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#endif
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#endif
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}
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