* add skeleton of redis backend

configs/conf-available/10-backend-redis.conf

@@ -0,0 +1,7 @@
+[backend:redis]
+load = libf2b_backend_redis.so
+shared = no
+timeout = 2
+server = 127.0.0.1
+port   = 6379
+database = 0

src/backends/redis.c

@@ -0,0 +1,79 @@
+/* Copyright 2016 Alex 'AdUser' Z (ad_user@runbox.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <hiredis.h>
+
+#include "backend.h"
+
+struct _config {
+  char name[ID_MAX + 1];
+  char error[256];
+  bool shared;
+  struct timeval timeout;
+  uint8_t database;
+  char    server[32];
+  uint16_t port;
+  redisContext *conn;
+};
+
+/* handlers */
+cfg_t *
+create(const char *id) {
+}
+
+bool
+ready(cfg_t *cfg) {
+}
+
+char *
+error(cfg_t *cfg) {
+}
+
+bool
+start(cfg_t *cfg) {
+}
+
+bool
+stop(cfg_t *cfg) {
+}
+
+bool
+ban(cfg_t *cfg, const char *ip) {
+}
+
+bool
+unban(cfg_t *cfg, const char *ip) {
+}
+
+bool
+check(cfg_t *cfg, const char *ip) {
+}
+
+bool
+ping(cfg_t *cfg) {
+  assert(cfg != NULL);
+  redisReply *reply = redisCommand(cfg->conn, "PING");
+  if (reply) {
+    freeReplyObject(reply);
+    return true;
+  }
+  return false;
+}
+
+void
+destroy(cfg_t *cfg) {
+}