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/*
* vi: ft=c
*/
/* 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
enum dns_record {
A = 1,
NS = 2,
CNAME = 5,
SOA = 6,
MX = 15,
TXT = 16,
AAAA = 28,
SRV = 33
};
/* Record Classes */
#define CL_IN 1 /* Internet */
#define CL_CS 2 /* CSNET (Obsolete) */
#define CL_CH 3 /* CHAOS */
#define CL_HS 4 /* Hesiod */
enum dns_record_class {
IN = 1,
CS = 2,
CH = 3,
HS = 4
};
/* OPCODES */
#define OP_QUERY 0 /* Query */
#define OP_IQUERY 1 /* Inverse Query */
#define OP_STATUS 2 /* Status request */
enum dns_opcode {
QUERY = 0,
INVERSE = 1,
STATUS = 2
};
/* Responsecode */
#define RCODE_NOERR 0
#define RCODE_FORMAT 1
#define RCODE_SERVFAIL 2
#define RCODE_NAMEERR 3
#define RCODE_NOTIMPL 4
#define RCODE_REFUSED 5
enum dns_responsecode {
NOERR = 0,
FORMAT = 1,
SERVFAIL= 2,
NAMEERR = 3,
NOTIMPL = 4,
REFUSED = 5
};
#define DNS_HEADER_LEN 12
#define FLIP_BYTES(u) (((0x00FF & u) << 8) | ((0xFF00 & u) >> 8))
/**
* Data is COPIED
* */
typedef struct dns_header dns_header_t;
/**
* QNAME is REFERENCED
* */
typedef struct dns_question dns_question_t;
/**
* NAME is REFERENCED
* */
typedef struct dns_answer dns_answer_t;
/**
* DNS Message struct
*
* An initialized instance is only valid as long as
* the buffer used to create it remains unchanged as
* some values are referenced, not copied.
* */
typedef struct dns_message dns_message_t;
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;
int qname_len;
uint16_t qtype;
uint16_t qclass;
};
struct dns_answer {
const char* qname;
int qname_len;
uint16_t type;
uint16_t class;
uint32_t ttl;
uint16_t rdlength;
char* rdata;
};
struct dns_message {
struct dns_header header;
int question_count;
dns_question_t* question;
int answer_count;
dns_answer_t* answer;
};
int dns_construct_header (
char* _buffer,
int _bufflen,
dns_header_t* _header
);
int dns_construct_answer (
char* _buffer,
int _bufflen,
dns_answer_t* _answer
);
int dns_construct_questoin (
char* _buffer,
int _bufflen,
dns_question_t* _question
);
/* Question and answer count come from header */
int dns_construct_packet (
char* _buffer,
int _bufflen,
dns_message_t* _message
);
/**
* Frees all malloced memory
* */
int dns_destroy_struct ( dns_message_t* _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, dns_message_t* _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 );
/**
* Check FQDN validity
* Returns: 0 when valid, <0 for string errors, position > 0 of invalid character
*/
int fqdn_check ( char* _source, int _sourcelen );
/**
* 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
* accepts only ASCII alphanumeric characters
* returns: length of QNAME including NULL-byte at the end, < 0 on error
* */
int qname_check( char* _source, int _sourcelen );
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