dns.th

#ifndef __DNS_RESOLVER_INCLUDED__
#define __DNS_RESOLVER_INCLUDED__


#include "global.th"


#define DEFAULT_DNS_TIMEOUT		20


/* Current resolver state
 */
enum dns_state {
	DNS_IDLE,
	DNS_AWAITING_RESPONSE
};


/* DNS opcodes for hdr.opcode field
 */
enum {
	DNS_OPC_QUERY = 0,
	DNS_OPC_IQUERY = 1,
	DNS_OPC_STATUS = 2
};


/* Error codes for hdr.rcode field
 */
enum dns_error {
	DNS_ERR_SUCCESS = 0,
	DNS_ERR_FORMAT = 1,
	DNS_ERR_FAILURE = 2,
	DNS_ERR_NAME = 3,
	DNS_ERR_NOT_IMPLEMENTED = 4,
	DNS_ERR_REFUSED = 5
};


/* Resource records
 */
enum dns_record_type {
	RR_A             = 1, // A host address
	RR_NS            = 2, // An authoritative name server
	RR_MD            = 3, // A mail destination (Obsolete - use MX)
	RR_MF            = 4, // A mail forwarder (Obsolete - use MX)
	RR_CNAME         = 5, // The canonical name for an alias
	RR_SOA           = 6, // Marks the start of a zone of authority
	RR_MB            = 7, // A mailbox domain name (EXPERIMENTAL)
	RR_MG            = 8, // A mail group member (EXPERIMENTAL)
	RR_MR            = 9, // A mail rename domain name (EXPERIMENTAL)
	RR_NULL          = 10, // A null RR (EXPERIMENTAL)
	RR_WKS           = 11, // A well known service description
	RR_PTR           = 12, // A domain name pointer
	RR_HINFO         = 13, // Host information
	RR_MINFO         = 14, // Mailbox or mail list information
	RR_MX            = 15, // Mail exchange
	RR_TXT           = 16  // Text strings
};


struct dns_record {
	word type;
	word cls;
	dword ttl;
	word rdlen;
};


struct dns_hdr {
#if 0
	// word 0: request ID
	word id: 16;
	
	// word 1: bit fields in REVERSED order, because TibboC compiler allocates bits from LSB to MSB
	
	word qr: 1;
	word opcode: 4;
	word aa: 1;
	word tc: 1;
	word rd: 1;
	word ra: 1;
	word z: 3;
	word rcode: 4;
	
	// words 2, 3, 4 and 5
	word qdcount: 16;
	word ancount: 16;
	word nscount: 16;
	word arcount: 16;
#else
	word id;
	word flags;
	word qdcount;
	word ancount;
	word nscount;
	word arcount;
#endif
};


extern bool dns_init();
extern bool dns_resolve(string&, dns_record_type);
extern void dns_process_packet();
extern void dns_wait();
extern void dns_timer();

extern void on_dns_resolved(dns_error, dns_record_type, string&);

#endif