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 #ifdef HAVE_CONFIG_H 23 #include "config.h" 24 #endif 25 26 #include <tcpdump-stdinc.h> 27 28 #include <signal.h> 29 #ifdef HAVE_SIGACTION 30 #include <string.h> 31 #endif 32 33 #ifdef HAVE_OS_PROTO_H 34 #include "os-proto.h" 35 #endif 36 37 #include "setsignal.h" 38 39 /* 40 * An OS-independent signal() with, whenever possible, partial BSD 41 * semantics, i.e. the signal handler is restored following service 42 * of the signal, but system calls are *not* restarted, so that if 43 * "pcap_breakloop()" is called in a signal handler in a live capture, 44 * the read/recvfrom/whatever in the live capture doesn't get restarted, 45 * it returns -1 and sets "errno" to EINTR, so we can break out of the 46 * live capture loop. 47 * 48 * We use "sigaction()" if available. We don't specify that the signal 49 * should restart system calls, so that should always do what we want. 50 * 51 * Otherwise, if "sigset()" is available, it probably has BSD semantics 52 * while "signal()" has traditional semantics, so we use "sigset()"; it 53 * might cause system calls to be restarted for the signal, however. 54 * I don't know whether, in any systems where it did cause system calls to 55 * be restarted, there was a way to ask it not to do so; there may no 56 * longer be any interesting systems without "sigaction()", however, 57 * and, if there are, they might have "sigvec()" with SV_INTERRUPT 58 * (which I think first appeared in 4.3BSD). 59 * 60 * Otherwise, we use "signal()" - which means we might get traditional 61 * semantics, wherein system calls don't get restarted *but* the 62 * signal handler is reset to SIG_DFL and the signal is not blocked, 63 * so that a subsequent signal would kill the process immediately. 64 * 65 * Did I mention that signals suck? At least in POSIX-compliant systems 66 * they suck far less, as those systems have "sigaction()". 67 */ 68 RETSIGTYPE 69 (*setsignal (int sig, RETSIGTYPE (*func)(int)))(int) 70 { 71 #ifdef HAVE_SIGACTION 72 struct sigaction old, new; 73 74 memset(&new, 0, sizeof(new)); 75 new.sa_handler = func; 76 if (sig == SIGCHLD) 77 new.sa_flags = SA_RESTART; 78 if (sigaction(sig, &new, &old) < 0) 79 return (SIG_ERR); 80 return (old.sa_handler); 81 82 #else 83 #ifdef HAVE_SIGSET 84 return (sigset(sig, func)); 85 #else 86 return (signal(sig, func)); 87 #endif 88 #endif 89 } 90 91
