First draft of response structure.

refs #143

src/dnslib/response.h

@@ -11,11 +11,66 @@
  * \addtogroup dnslib
  * @{
  */
-
 #ifndef _CUTEDNS_DNSLIB_RESPONSE_H_
 #define _CUTEDNS_DNSLIB_RESPONSE_H_
 
+#include <stdint.h>
+#include <string.h>
+
+#include "dname.h"
+#include "rrset.h"
+
+/*!
+ * MTU <= 4500B
+ * IP header has 24 B
+ * DNS header has 12 B
+ * DNS question is at least 5 B long (2 bytes TYPE, 2 bytes CLASS, 1 byte QNAME)
+ * Each DNS RR is at least 11 B long:
+ *   TYPE: 2 B
+ *   CLASS: 2 B
+ *   TTL: 4 B
+ *   RDLENGTH: 2 B
+ *   OWNER: at least 1 B (root label)
+ *   RDATA: may be 0 B (theoretically)
+ *
+ * (4500 - 24 - 12 - 5) / 11 = 405
+ */
+static const size_t MAX_RRS_IN_RESPONSE = 405;
+
+/*!
+ * \note Current size of the structure:
+ *         32bit machine: 18 + 405 x 3 x 4 = 4878 B
+ *         64bit machine: 34 + 405 x 3 x 8 = 9754 B
+ *
+ * \todo Consider dynamically resizing the arrays for RRSets. With well picked
+ *       default sizes we could avoid much reallocations (or any at all) and
+ *       keep the space reasonably small.
+ * \todo Structures for compressing domain names.
+ * \todo Structure for EDNS information parsed from the query.
+ */
+struct dnslib_response {
+	/*!
+	 * \brief Normalized QNAME.
+	 *
+	 * \note Only one Question is supported!
+	 */
+	dnslib_dname_t *qname;
+	uint16_t qtype;
+
+	size_t max_size;  /*!< Maximum allowed size of the response. */
+
+	uint8_t *resp_wire;
+	size_t resp_size;
+
+	/*! \todo Consider using one array. It would save space but cause
+	 *        more difficult converting to wire format.
+	 */
+	dnslib_rrset_t *answer[MAX_RRS_IN_RESPONSE];
+	dnslib_rrset_t *authority[MAX_RRS_IN_RESPONSE];
+	dnslib_rrset_t *additional[MAX_RRS_IN_RESPONSE];
+};
 
+typedef struct dnslib_response dnslib_response_t;
 
 #endif /* _CUTEDNS_DNSLIB_RESPONSE_H_ */