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/* dns.h
* (c) Jonas Gunz, 2019
* License: MIT
* */
#pragma once
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
//TODO remove
#include <stdio.h>
//Resource Records
#define RR_A 1
#define RR_NS 2
#define RR_CNAME 5
#define RR_SOA 6
#define RR_MX 15
#define RR_TXT 16
#define RR_AAAA 28
#define RR_SRV 33
//Record Classes
#define CL_IN 1 //Internet
#define CL_CS 2 //CSNET (Onsolete)
#define CL_CH 3 //CHAOS
#define CL_HS 4 //Hesiod
//OPCODES
#define OP_Q 0 //Query
#define OP_IQ 1 //Inverse Query
#define OP_STAT 2 //Status request
//Responsecode
#define RCODE_NOERR 0
#define RCODE_FORMAT 1
#define RCODE_SERVFAIL 2
#define RCODE_NAMEERR 3
#define RCODE_NI 4 //Not implemented
#define RCODE_REFUSED 5
#define FLIP_BYTES(u) (((0x00FF & u) << 8) | ((0xFF00 & u) >> 8))
/**
* Data is COPIED
* */
struct dns_header;
/**
* QNAME is REFERENCED
* */
struct dns_question;
/**
* NAME is REFERENCED
* */
struct dns_answer;
/**
* DNS Message struct
*
* A initialized instance is only valid as long as
* the buffer used to create it remains unchanged
* */
struct dns_message;
struct dns_header {
uint16_t id;
uint8_t QR; //Query:0 Reply:1
uint8_t OPCODE; //Query:0 Iquery:1 Status:2
uint8_t AA; //Authorative answer
uint8_t TC; //Truncation
uint8_t RD; //Recursion Desired
uint8_t RA; //Recursion Available
uint8_t Z; //Unused
uint8_t RCODE; //Response Code
uint16_t question_count;
uint16_t answer_count;
uint16_t authorative_count;
uint16_t additional_count;
};
struct dns_question {
const char* qname;
uint16_t qtype;
uint16_t qclass;
};
struct dns_answer {
char* name; //in qname format
uint16_t type;
uint16_t class;
uint32_t ttl;
uint16_t rdlength;
char* rdata;
};
struct dns_message {
struct dns_header header;
int question_count;
struct dns_question* question;
int answer_count;
struct dns_answer* answer;
};
int dns_construct_header (
struct dns_header* _header,
char* _buffer,
int _bufflen
);
/**
* Frees all malloced memory
* */
int dns_destroy_struct ( struct dns_message* _msg );
/**
* Parse the packet in _buffer and populate the dns_message struct
* Struct may still be written to on failure but contents are invalid
* returns: 0 on success, !=0 on failure
*
* ONLY WRITES QUESTION SECTION. ALL OTHER ARE IGNORED
*
* */
int dns_parse_packet ( char* _buffer, int _bufflen, struct dns_message* _msg );
/**
* Convert a null terminated string containing a
* fqdn (eg server.example.com) to the binary format used by DNS records
* ( [6]server[7]example[3]com[0] )
* returns: length of string in _sink, < 0 on failure
* _sink might not be terminated on error.
* */
int fqdn_to_qname( char* _source, int _sourcelen, char* _sink, int _sinklen );
/**
* Convert a QNAME back to a FQDN, reversing fqdn_to_qname( )
* returns: length of string in _sink, < 0 on failure
* _sink may still be altered in failed attempts, but not terminated.
* */
int qname_to_fqdn( char* _source, int _sourcelen, char* _sink, int _sinklen );
/**
* Check a QNAME and get length
* returns: length of QNAME including NULL-byte at the end, < 0 on error
* */
int qname_check( char* _source, int _sourcelen );
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