1 files changed, 90 insertions, 0 deletions
diff --git a/setsignal.c b/setsignal.c
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+++ b/setsignal.c
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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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <netdissect-stdinc.h>
+
+#include <signal.h>
+#ifdef HAVE_SIGACTION
+#include <string.h>
+#endif
+
+#ifdef HAVE_OS_PROTO_H
+#include "os-proto.h"
+#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 (sig == SIGCHLD)
+		new.sa_flags = SA_RESTART;
+	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
+}
+