diff options
| -rw-r--r-- | src/ulogd.c | 132 |
1 files changed, 125 insertions, 7 deletions
diff --git a/src/ulogd.c b/src/ulogd.c index 958c30a..c8d9376 100644 --- a/src/ulogd.c +++ b/src/ulogd.c @@ -90,6 +90,29 @@ static int info_mode = 0; static int verbose = 0; static int created_pidfile = 0; +/* + * Using self-pipe trick to handle signals safely. + * (To avoid calling Async-Signal-Unsafe functions in signal handler.) + * + * cf. https://lwn.net/Articles/177897/ + * + * Capacity of pipe(2) buffer is >= 4096. + */ +static int signal_channel[2] = { -1, -1 }; /* initialize with invalid fd */ +#define SIGNAL_RX_FD (signal_channel[0]) /* main thread select() this fd */ +#define SIGNAL_TX_FD (signal_channel[1]) /* signal handler writes to this fd */ + +static void signal_handler(int signal); +static void sigterm_handler_task(int signal); +static void signal_handler_task(int signal); + +static int signal_channel_callback(int fd, unsigned int what, void *data); +static struct ulogd_fd signal_channel_ulogfd = { + .when = ULOGD_FD_READ, + .cb = &signal_channel_callback, + .data = &signal_channel_ulogfd, +}; + /* linked list for all registered plugins */ static LLIST_HEAD(ulogd_plugins); /* linked list for all plugins handle */ @@ -387,6 +410,80 @@ void ulogd_register_plugin(struct ulogd_plugin *me) } /*********************************************************************** + * UTILITY FUNCTIONS FOR SIGNAL HANDLING + ***********************************************************************/ +static void call_signal_handler_tasks(int sig) +{ + /* Deliver signals */ + switch (sig) { + case SIGTERM: + case SIGINT: + sigterm_handler_task(sig); + break; + case SIGHUP: + case SIGALRM: + case SIGUSR1: + case SIGUSR2: + signal_handler_task(sig); + break; + default: + break; + } +} + +static int signal_channel_callback(int fd, unsigned int what, void *data) +{ + int ret; + unsigned char c; + + while ((ret = read(fd, &c, 1)) > 0) { + call_signal_handler_tasks((int)c); + } + return 0; +} + +static int create_signal_channel(void) +{ + int ret; + long flags; + + if ((ret = pipe(signal_channel)) < 0) + return ret; + + /* SIGNAL_RX_FD, channel[0] */ + if ((flags = fcntl(SIGNAL_RX_FD, F_GETFL)) < 0) + goto err_exit; + flags |= O_NONBLOCK; + if ( fcntl(SIGNAL_RX_FD, F_SETFL, flags) < 0 ) + goto err_exit; + + /* SIGNAL_TX_FD, channel[1] */ + if ((flags = fcntl(SIGNAL_TX_FD, F_GETFL)) < 0) + goto err_exit; + flags |= O_NONBLOCK; + if ( fcntl(SIGNAL_TX_FD, F_SETFL, flags) < 0 ) + goto err_exit; + + /* register SIGNAL_RX_FD to ulogd */ + signal_channel_ulogfd.fd = SIGNAL_RX_FD; + ulogd_register_fd(&signal_channel_ulogfd); + + return 0; + +err_exit: + if (SIGNAL_RX_FD >= 0) { + (void)close(SIGNAL_RX_FD); + SIGNAL_RX_FD = -1; + } + if (SIGNAL_TX_FD >= 0) { + (void)close(SIGNAL_TX_FD); + SIGNAL_TX_FD = -1; + } + return -1; +} + + +/*********************************************************************** * MAIN PROGRAM ***********************************************************************/ @@ -925,7 +1022,6 @@ static void ulogd_main_loop(void) struct timeval *next = NULL; while (1) { - /* XXX: signal blocking? */ if (next != NULL && !timerisset(next)) next = ulogd_do_timer_run(&next_alarm); else @@ -1225,7 +1321,19 @@ static void stop_stack() } -static void sigterm_handler(int signal) +/* This is a real SIGTERM, SIGINT, SIGHUP, SIGALRM, SIGUSR1, SIGUSR2 handler */ +static void signal_handler(int signal) +{ + unsigned char c = (unsigned char)signal; + + (void)write(SIGNAL_TX_FD, &c, 1); +} + +/* This is NOT a real signal handler. + * It is called in ulogd_main_loop() to avoid + * calling Async-Signal-UnSafe functions in signal handler. + */ +static void sigterm_handler_task(int signal) { ulogd_log(ULOGD_NOTICE, "Terminal signal received, exiting\n"); @@ -1255,7 +1363,12 @@ static void sigterm_handler(int signal) exit(0); } -static void signal_handler(int signal) + +/* This is NOT a real signal handler. + * It is called in ulogd_main_loop() to avoid + * calling Async-Signal-UnSafe functions in signal handler. + */ +static void signal_handler_task(int signal) { ulogd_log(ULOGD_NOTICE, "signal received, calling pluginstances\n"); @@ -1269,7 +1382,7 @@ static void signal_handler(int signal) fprintf(stderr, "ERROR: can't open logfile %s: %s\n", ulogd_logfile, strerror(errno)); - sigterm_handler(signal); + sigterm_handler_task(signal); } } @@ -1464,8 +1577,13 @@ int main(int argc, char* argv[]) } } - signal(SIGTERM, &sigterm_handler); - signal(SIGINT, &sigterm_handler); + if (create_signal_channel() < 0) { + ulogd_log(ULOGD_FATAL, "can't create signal channel\n"); + warn_and_exit(daemonize); + } + + signal(SIGTERM, &signal_handler); + signal(SIGINT, &signal_handler); signal(SIGHUP, &signal_handler); signal(SIGALRM, &signal_handler); signal(SIGUSR1, &signal_handler); @@ -1477,6 +1595,6 @@ int main(int argc, char* argv[]) ulogd_main_loop(); /* hackish, but result is the same */ - sigterm_handler(SIGTERM); + sigterm_handler_task(SIGTERM); return(0); } |