Optimize configuration, and add blacklist ip features

src/util.c

@@ -155,6 +155,11 @@ int set_fd_nonblock(int fd, int nonblock)
 char *reverse_string(char *output, char *input, int len)
 {
 	char *begin = output;
+	if (len <= 0) {
+		*output = 0;
+		return output;
+	}
+	
 	len--;
 	while (len >= 0) {
 		*output = *(input + len);