1 files changed, 148 insertions, 0 deletions
diff --git a/src/knot/common/unreachable.c b/src/knot/common/unreachable.c
new file mode 100644
index 0000000..e137f3d
--- /dev/null
+++ b/src/knot/common/unreachable.c
@@ -0,0 +1,148 @@
+/*  Copyright (C) 2021 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program 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.
+
+    This program 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 <https://www.gnu.org/licenses/>.
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+#include <time.h>
+
+#include "unreachable.h"
+
+knot_unreachables_t *global_unreachables = NULL;
+
+static uint32_t get_timestamp(void)
+{
+	struct timespec t;
+	clock_gettime(CLOCK_MONOTONIC, &t);
+	uint64_t res = (uint64_t)t.tv_sec * 1000;
+	res += (uint64_t)t.tv_nsec / 1000000;
+	return res & 0xffffffff; // overflow does not matter since we are working with differences
+}
+
+knot_unreachables_t *knot_unreachables_init(uint32_t ttl_ms)
+{
+	knot_unreachables_t *res = calloc(1, sizeof(*res));
+	if (res != NULL) {
+		pthread_mutex_init(&res->mutex, NULL);
+		res->ttl_ms = ttl_ms;
+		init_list(&res->urs);
+	}
+	return res;
+}
+
+uint32_t knot_unreachables_ttl(knot_unreachables_t *urs, uint32_t new_ttl_ms)
+{
+	if (urs == NULL) {
+		return 0;
+	}
+
+	pthread_mutex_lock(&urs->mutex);
+
+	uint32_t prev = urs->ttl_ms;
+	urs->ttl_ms = new_ttl_ms;
+
+	pthread_mutex_unlock(&urs->mutex);
+
+	return prev;
+}
+
+void knot_unreachables_deinit(knot_unreachables_t **urs)
+{
+	if (urs != NULL && *urs != NULL) {
+		knot_unreachable_t *ur, *nxt;
+		WALK_LIST_DELSAFE(ur, nxt, (*urs)->urs) {
+			rem_node((node_t *)ur);
+			free(ur);
+		}
+		pthread_mutex_destroy(&(*urs)->mutex);
+		free(*urs);
+		*urs = NULL;
+	}
+}
+
+static bool clear_old(knot_unreachable_t *ur, uint32_t now, uint32_t ttl_ms)
+{
+	if (ur->time_ms != 0 && now - ur->time_ms > ttl_ms) {
+		rem_node((node_t *)ur);
+		free(ur);
+		return true;
+	}
+	return false;
+}
+
+// also clears up (some) expired unreachables
+static knot_unreachable_t *get_ur(knot_unreachables_t *urs,
+                                  const struct sockaddr_storage *addr,
+                                  const struct sockaddr_storage *via)
+{
+	assert(urs != NULL);
+
+	uint32_t now = get_timestamp();
+	knot_unreachable_t *ur, *nxt;
+	WALK_LIST_DELSAFE(ur, nxt, urs->urs) {
+		if (clear_old(ur, now, urs->ttl_ms)) {
+			continue;
+		}
+
+		if (sockaddr_cmp(&ur->addr, addr, false) == 0 &&
+		    sockaddr_cmp(&ur->via, via, true) == 0) {
+			return ur;
+		}
+	}
+
+	return NULL;
+}
+
+bool knot_unreachable_is(knot_unreachables_t *urs,
+                         const struct sockaddr_storage *addr,
+                         const struct sockaddr_storage *via)
+{
+	if (urs == NULL) {
+		return false;
+	}
+	assert(addr);
+	assert(via);
+
+	pthread_mutex_lock(&urs->mutex);
+
+	bool res = (get_ur(urs, addr, via) != NULL);
+
+	pthread_mutex_unlock(&urs->mutex);
+
+	return res;
+}
+
+void knot_unreachable_add(knot_unreachables_t *urs,
+                          const struct sockaddr_storage *addr,
+                          const struct sockaddr_storage *via)
+{
+	if (urs == NULL) {
+		return;
+	}
+	assert(addr);
+	assert(via);
+
+	pthread_mutex_lock(&urs->mutex);
+
+	knot_unreachable_t *ur = malloc(sizeof(*ur));
+	if (ur != NULL) {
+		memcpy(&ur->addr, addr, sizeof(ur->addr));
+		memcpy(&ur->via, via, sizeof(ur->via));
+		ur->time_ms = get_timestamp();
+		add_head(&urs->urs, (node_t *)ur);
+	}
+
+	pthread_mutex_unlock(&urs->mutex);
+}