dns_cache: Replace cache timeout mechanism with time wheel algorithm to reduce CPU usage

src/timer.c

@@ -0,0 +1,70 @@
+/*************************************************************************
+ *
+ * Copyright (C) 2018-2023 Ruilin Peng (Nick) <pymumu@gmail.com>.
+ *
+ * smartdns is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * smartdns is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "timer.h"
+#include "timer_wheel.h"
+
+static struct tw_base *dns_timer_base = NULL;
+
+int dns_timer_init(void)
+{
+	struct tw_base *tw = tw_init_timers();
+	if (tw == NULL) {
+		return -1;
+	}
+
+	dns_timer_base = tw;
+
+	return 0;
+}
+
+void dns_timer_destroy(void)
+{
+	if (dns_timer_base != NULL) {
+		tw_cleanup_timers(dns_timer_base);
+		dns_timer_base = NULL;
+	}
+}
+
+void dns_timer_add(struct tw_timer_list *timer)
+{
+	if (dns_timer_base == NULL) {
+		return;
+	}
+
+	tw_add_timer(dns_timer_base, timer);
+}
+
+int dns_timer_del(struct tw_timer_list *timer)
+{
+	if (dns_timer_base == NULL) {
+		return 0;
+	}
+
+	return tw_del_timer(dns_timer_base, timer);
+}
+
+int dns_timer_mod(struct tw_timer_list *timer, unsigned long expires)
+{
+	if (dns_timer_base == NULL) {
+		return 0;
+	}
+
+	return tw_mod_timer(dns_timer_base, timer, expires);
+}
+