1 /* 2 * Copyright (c) 1997 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that: (1) source code distributions 7 * retain the above copyright notice and this paragraph in its entirety, (2) 8 * distributions including binary code include the above copyright notice and 9 * this paragraph in its entirety in the documentation or other materials 10 * provided with the distribution, and (3) all advertising materials mentioning 11 * features or use of this software display the following acknowledgement: 12 * ``This product includes software developed by the University of California, 13 * Lawrence Berkeley Laboratory and its contributors.'' Neither the name of 14 * the University nor the names of its contributors may be used to endorse 15 * or promote products derived from this software without specific prior 16 * written permission. 17 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED 18 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF 19 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. 20 */ 21 22 #ifndef lint 23 static const char rcsid[] _U_ = 24 "@(#) $Header: /tcpdump/master/tcpdump/setsignal.c,v 1.11 2003-11-16 09:36:42 guy Exp $ (LBL)"; 25 #endif 26 27 #ifdef HAVE_CONFIG_H 28 #include "config.h" 29 #endif 30 31 #include <tcpdump-stdinc.h> 32 33 #include <signal.h> 34 #ifdef HAVE_SIGACTION 35 #include <string.h> 36 #endif 37 38 #ifdef HAVE_OS_PROTO_H 39 #include "os-proto.h" 40 #endif 41 42 #include "setsignal.h" 43 44 /* 45 * An OS-independent signal() with, whenever possible, partial BSD 46 * semantics, i.e. the signal handler is restored following service 47 * of the signal, but system calls are *not* restarted, so that if 48 * "pcap_breakloop()" is called in a signal handler in a live capture, 49 * the read/recvfrom/whatever in the live capture doesn't get restarted, 50 * it returns -1 and sets "errno" to EINTR, so we can break out of the 51 * live capture loop. 52 * 53 * We use "sigaction()" if available. We don't specify that the signal 54 * should restart system calls, so that should always do what we want. 55 * 56 * Otherwise, if "sigset()" is available, it probably has BSD semantics 57 * while "signal()" has traditional semantics, so we use "sigset()"; it 58 * might cause system calls to be restarted for the signal, however. 59 * I don't know whether, in any systems where it did cause system calls to 60 * be restarted, there was a way to ask it not to do so; there may no 61 * longer be any interesting systems without "sigaction()", however, 62 * and, if there are, they might have "sigvec()" with SV_INTERRUPT 63 * (which I think first appeared in 4.3BSD). 64 * 65 * Otherwise, we use "signal()" - which means we might get traditional 66 * semantics, wherein system calls don't get restarted *but* the 67 * signal handler is reset to SIG_DFL and the signal is not blocked, 68 * so that a subsequent signal would kill the process immediately. 69 * 70 * Did I mention that signals suck? At least in POSIX-compliant systems 71 * they suck far less, as those systems have "sigaction()". 72 */ 73 RETSIGTYPE 74 (*setsignal (int sig, RETSIGTYPE (*func)(int)))(int) 75 { 76 #ifdef HAVE_SIGACTION 77 struct sigaction old, new; 78 79 memset(&new, 0, sizeof(new)); 80 new.sa_handler = func; 81 if (sig == SIGCHLD) 82 new.sa_flags = SA_RESTART; 83 if (sigaction(sig, &new, &old) < 0) 84 return (SIG_ERR); 85 return (old.sa_handler); 86 87 #else 88 #ifdef HAVE_SIGSET 89 return (sigset(sig, func)); 90 #else 91 return (signal(sig, func)); 92 #endif 93 #endif 94 } 95 96
