1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
|
/* dns.h
* (c) Jonas Gunz, 2019
* License: MIT
* */
#pragma once
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
//TODO remove
#include <stdio.h>
//TODO remove defines
//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 //Not implemented
#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; //in qname format
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 );
/**
* 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 );
|