1 files changed, 100 insertions, 0 deletions
diff --git a/src/contrib/conn_pool.h b/src/contrib/conn_pool.h
new file mode 100644
index 0000000..f1f2c6c
--- /dev/null
+++ b/src/contrib/conn_pool.h
@@ -0,0 +1,100 @@
+/*  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/>.
+ */
+
+#pragma once
+
+#include <pthread.h>
+#include <stdbool.h>
+#include <sys/socket.h>
+
+#include "contrib/time.h"
+
+typedef struct {
+	struct sockaddr_storage src;
+	struct sockaddr_storage dst;
+	int fd;
+	knot_time_t last_active;
+} conn_pool_memb_t;
+
+typedef struct {
+	size_t capacity;
+	size_t usage;
+	knot_timediff_t timeout;
+	pthread_mutex_t mutex;
+	pthread_t closing_thread;
+	conn_pool_memb_t conns[];
+} conn_pool_t;
+
+extern conn_pool_t *global_conn_pool;
+
+/*!
+ * \brief Allocate connection pool.
+ *
+ * \param capacity  Connection pool capacity (must be positive number).
+ * \param timeout   Connection timeout (must be positive number).
+ *
+ * \return Connection pool or NULL if error.
+ */
+conn_pool_t *conn_pool_init(size_t capacity, knot_timediff_t timeout);
+
+/*!
+ * \brief Deallocate the pool, close all connections, terminate closing thread.
+ *
+ * \param pool  Connection pool.
+ */
+void conn_pool_deinit(conn_pool_t *pool);
+
+/*!
+ * \brief Get and/or set connection timeout.
+ *
+ * \param pool         Connection pool.
+ * \param new_timeout  Optional: set new timeout (if positive number).
+ *
+ * \return Previous value of timeout.
+ */
+knot_timediff_t conn_pool_timeout(conn_pool_t *pool,
+                                  knot_timediff_t new_timeout);
+
+/*!
+ * \brief Try to get an open connection if present, check if alive.
+ *
+ * \param pool   Pool to search in.
+ * \param src    Connection source address.
+ * \param dst    Connection destination address.
+ *
+ * \retval -1    If error (no such connection).
+ * \return >= 0  File descriptor of the connection.
+ */
+int conn_pool_get(conn_pool_t *pool,
+                  struct sockaddr_storage *src,
+                  struct sockaddr_storage *dst);
+
+/*!
+ * \brief Put an open connection to the pool, possibly displacing the oldest one there.
+ *
+ * \param pool   Pool to insert into.
+ * \param src    Connestion source address.
+ * \param dst    Connection destination adress.
+ * \param fd     Connection file descriptor.
+ *
+ * \retval -1    If connection stored to free slot.
+ * \retval fd    If not able to store connection.
+ * \return >= 0  File descriptor of the displaced old connection.
+ */
+int conn_pool_put(conn_pool_t *pool,
+                  struct sockaddr_storage *src,
+                  struct sockaddr_storage *dst,
+                  int fd);