syslogd: Add generic timer API to replace exising buggy one

This patch adds a alarm()/SIGALRM based generic timer API to syslogd.
The API takes care to wrap SIGALRM and serialize all timer events to
a standard UNIX pipe(2) which syslogd can poll() for like any other
incoming event.

Signed-off-by: Joachim Nilsson <troglobit@gmail.com>

src/Makefile.am

@@ -34,7 +34,7 @@ AM_CFLAGS            += -Wno-unused-result -Wno-unused-parameter -fno-strict-ali
 AM_CPPFLAGS           = -DSYSCONFDIR=\"@sysconfdir@\" -DRUNSTATEDIR=\"@runstatedir@\"
 AM_CPPFLAGS          += -D_BSD_SOURCE -D_DEFAULT_SOURCE
 
-syslogd_SOURCES       = syslogd.c syslogd.h socket.c socket.h syslog.h queue.h compat.h
+syslogd_SOURCES       = syslogd.c syslogd.h socket.c socket.h syslog.h timer.c timer.h queue.h compat.h
 syslogd_CPPFLAGS      = $(AM_CPPFLAGS) -D_XOPEN_SOURCE=600
 syslogd_LDADD         = $(LIBS) $(LIBOBJS)
 

src/timer.c

@@ -0,0 +1,221 @@
+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (C) 2017-2019  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. 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 BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <err.h>
+#include <signal.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "queue.h"
+#include "socket.h"
+
+struct timer {
+	LIST_ENTRY(timer) tmr_link;
+
+	int      tmr_period;	/* period time in seconds */
+	time_t   tmr_timeout;
+
+	void   (*tmr_cb)(void *arg);
+	void    *tmr_arg;
+};
+
+static LIST_HEAD(, timer) tmr_head = LIST_HEAD_INITIALIZER();
+
+static struct timespec now;
+static int timer_fd[2];
+
+/*
+ * what time is it?
+ */
+int timer_update(void)
+{
+	return clock_gettime(CLOCK_MONOTONIC, &now);
+}
+
+time_t timer_now(void)
+{
+	return now.tv_sec;
+}
+
+/*
+ * create periodic timer (seconds)
+ */
+int timer_add(int period, void (*cb)(void *), void *arg)
+{
+	struct timer *tmr;
+
+	tmr = calloc(1, sizeof(*tmr));
+	if (!tmr)
+		return -1;
+
+	tmr->tmr_period = period;
+	tmr->tmr_cb     = cb;
+	tmr->tmr_arg    = arg;
+
+	LIST_INSERT_HEAD(&tmr_head, tmr, tmr_link);
+
+	return 0;
+}
+
+static int __timer_start(void)
+{
+	struct timer *next, *tmr;
+	time_t sec;
+
+	LIST_FOREACH(tmr, &tmr_head, tmr_link) {
+		if (tmr->tmr_timeout == 0)
+			tmr->tmr_timeout = timer_now() + tmr->tmr_period;
+	}
+
+	next = LIST_FIRST(&tmr_head);
+	LIST_FOREACH(tmr, &tmr_head, tmr_link) {
+		if (next->tmr_timeout > tmr->tmr_timeout)
+			next = tmr;
+	}
+
+	sec = next->tmr_timeout - timer_now();
+	if (sec <= 0)
+		sec = 1;
+
+	return alarm(sec);
+}
+
+/*
+ * start timers
+ */
+int timer_start(void)
+{
+	if (LIST_EMPTY(&tmr_head))
+		return -1;
+
+	timer_update();
+
+	return __timer_start();
+}
+
+/*
+ * callback for activity on pipe
+ */
+static void timer_cb(int sd, void *arg)
+{
+	struct timer *tmr;
+	char dummy;
+
+	(void)read(sd, &dummy, 1);
+
+	timer_update();
+
+	LIST_FOREACH(tmr, &tmr_head, tmr_link) {
+		if (tmr->tmr_timeout > timer_now())
+			continue;
+
+		if (tmr->tmr_cb)
+			tmr->tmr_cb(tmr->tmr_arg);
+		tmr->tmr_timeout = 0;
+	}
+
+	__timer_start();
+}
+
+/*
+ * Write to pipe to create an event on SIGALRM
+ */
+static void sigalarm_handler(int signo)
+{
+	(void)signo;
+	(void)write(timer_fd[1], "!", 1);
+}
+
+/*
+ * register signal pipe and callback
+ */
+int timer_init(void)
+{
+	static int initialized = 0;
+	struct sigaction sa;
+	int rc;
+
+	if (initialized)
+		return 0;
+
+	if (pipe(timer_fd)) {
+		warn("pipe()");
+		return -1;
+	}
+
+	sa.sa_handler = sigalarm_handler;
+	sa.sa_flags = SA_RESTART;
+	sigemptyset(&sa.sa_mask);
+	if (sigaction(SIGALRM, &sa, NULL)) {
+		warn("sigaction()");
+		goto err;
+	}
+
+	rc = socket_register(timer_fd[0], NULL, timer_cb, NULL);
+	if (rc < 0) {
+		warn("socket_register()");
+		goto err;
+	}
+
+	initialized = 1;
+
+	return 0;
+err:
+	close(timer_fd[0]);
+	close(timer_fd[1]);
+
+	return -1;
+}
+
+/*
+ * deregister signal pipe and callbacks
+ */
+void timer_exit(void)
+{
+	struct timer *tmr, *tmp;
+
+	alarm(0);
+
+	close(timer_fd[0]);
+	close(timer_fd[1]);
+
+	LIST_FOREACH_SAFE(tmr, &tmr_head, tmr_link, tmp) {
+		LIST_REMOVE(tmr, tmr_link);
+		free(tmr);
+	}
+}
+
+/**
+ * Local Variables:
+ *  indent-tabs-mode: t
+ *  c-file-style: "linux"
+ * End:
+ */

src/timer.h

@@ -0,0 +1,44 @@
+/*-
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (C) 2017-2019  Joachim Nilsson <troglobit@gmail.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. 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 BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef SYSKLOGD_TIMER_H_
+#define SYSKLOGD_TIMER_H_
+
+int    timer_add    (int period, void (*cb)(void *), void *arg);
+
+int    timer_start  (void);
+
+int    timer_update (void);
+time_t timer_now    (void);
+
+int    timer_init   (void);
+void   timer_exit   (void);
+
+#endif /* SYSKLOGD_TIMER_H_ */