Unit DNS
From Ultibo.org
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Contents
Description
Ultibo DNS Client unit
Note: DNS Client is IPv4 based, for IPv6 see new Winsock2 functions
See RFC 1035 Section 4 for details
Constants
DNS specific constants
DNS_* DNS_TIMEOUT = 5000;
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We wait for 5 seconds for a DNS reply |
DNS_RETRIES = 4;
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Try the request 4 times |
DNS_HEADER_SIZE = 12;
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SizeOf(TDNSHeader); |
DNS_QUESTION_SIZE = 4;
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SizeOf(TDNSQuestion); |
DNS_RESOURCE_SIZE = 10;
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SizeOf(TDNSResource); Not including Record Data |
MAX_DNS_NAME = 255;
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MAX_DNS_LABEL = 63;
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MAX_DNS_MESSAGE = 512;
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Maximum Size of DNS Message |
DNS flag
DNS_FLAG_* DNS_FLAG_RESPONSE = $8000;
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query = 0, response = 1 |
DNS_FLAG_AUTHORITY = $0400;
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Authoritative answer |
DNS_FLAG_TRUNCATED = $0200;
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Truncation, response was cut off at 512 |
DNS_FLAG_DO_RECURSE = $0100;
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Recursion desired |
DNS_FLAG_CAN_RECURSE = $0080;
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Recursion available |
DNS field masks
DNS_OPCODE_* DNS_OPCODE_MASK = $7800;
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Opcode |
DNS_RESPONSE_MASK = $000F;
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Response code |
DNS query code
DNS_QUERY* DNS_QUERY = 0;
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A standard query |
DNS_INV_QUERY = 1;
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An inverse query |
DNS_COMP_QUERY_MULTI = 2;
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A completion query, multiple reply (Obsolete) |
DNS_COMP_QUERY_SINGLE = 3;
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A completion query, single reply (Obsolete) |
DNS response code
DNS_NO_* DNS_NO_ERROR = 0;
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DNS_FORMAT_ERROR = 1;
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DNS_SERVER_FAILURE = 2;
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DNS_NAME_ERROR = 3;
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DNS_NOT_IMPLEMENTED = 4;
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DNS_REFUSED = 5;
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DNS record type
DNS_TYPE_* DNS_TYPE_A = 1;
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Host address resource record (RR) |
DNS_TYPE_NS = 2;
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DNS_TYPE_MD = 3;
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DNS_TYPE_MF = 4;
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DNS_TYPE_CNAME = 5;
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DNS_TYPE_SOA = 6;
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DNS_TYPE_MB = 7;
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DNS_TYPE_MG = 8;
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DNS_TYPE_MR = 9;
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DNS_TYPE_RT_NULL = 10;
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DNS_TYPE_WKS = 11;
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DNS_TYPE_PTR = 12;
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A domain name ptr |
DNS_TYPE_HINFO = 13;
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DNS_TYPE_MINFO = 14;
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DNS_TYPE_MX = 15;
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Mail exchange |
DNS address class
DNS_CLASS_* DNS_CLASS_IN = 1;
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ARPA internet class |
DNS_CLASS_CS = 2;
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DNS_CLASS_WILD = 255;
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Wildcard for several of the classifications |
DNS message compression
DNS_POINTER_* DNS_POINTER_MASK = $C0;
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Mask to indicate pointer to previously used name |
Type definitions
DNS specific types
PDNSHeader = ^TDNSHeader;
TDNSHeader = packed record
| Note: All Network Order | |
Identifier:Word;
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unique identifier |
Flags:Word;
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QD/Opcode/AA/TC/RD/RA/RCODE |
QuestionCount:Word;
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question section, number of entries |
AnswerCount:Word;
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answers, how many |
AuthorityCount:Word;
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count of name server RRs |
AdditionalCount:Word;
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number of "additional" records |
DNS message
PDNSMessage = ^TDNSMessage;
TDNSMessage = packed record
DNS:TDNSHeader;
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Data:array[0..(MAX_DNS_MESSAGE - DNS_HEADER_SIZE) - 1] of Byte;
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DNS name
PDNSName = ^TDNSName;
TDNSName = array[0..MAX_DNS_NAME - 1] of Char;
DNS question
PDNSQuestion = ^TDNSQuestion;
TDNSQuestion = packed record
| Note: All Network Order | |
Name:TDNSName;
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variable length question name |
QuestionType:Word;
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question type (eg DNS_TYPE_A) |
QuestionClass:Word;
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question class (eg DNS_CLASS_IN) |
DNS resource
PDNSResource = ^TDNSResource;
TDNSResource = packed record
| Note: All Network Order | |
Name:TDNSName;
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variable length resource name |
RecordType:Word;
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resource record type (eg DNS_TYPE_A) |
RecordClass:Word;
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resource record class (eg DNS_CLASS_IN) |
Ttl:LongWord;
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time-to-live, changed to 32 bits |
DataLength:Word;
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length of data field |
RecordData:array[0..MAX_DNS_MESSAGE - 1] of Byte;
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data field |
DNS client data
PDNSClientData = ^TDNSClientData;
TDNSClientData = record
| Note: Used for TLS Data | |
| Host Ent | |
HostEnt:THostEnt;
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HostEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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HostAliasesPtr:PChar;
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HostAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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HostAddrListPtr:PChar;
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HostAddrList:array[0..MAX_HOST_ALIASES - 1] of TInAddr;
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| Net Ent | |
NetEnt:TNetEnt;
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NetEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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NetAliasesPtr:PChar;
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NetAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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| Serv Ent | |
ServEnt:TServEnt;
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ServEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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ServAliasesPtr:PChar;
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ServAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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ServEntProto:array[0..MAX_NAME_SIZE - 1] of Char;
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| Proto Ent | |
ProtoEnt:TProtoEnt;
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ProtoEntName:array[0..MAX_NAME_SIZE - 1] of Char;
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ProtoAliasesPtr:PChar;
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ProtoAliases:array[0..(MAX_NAME_SIZE * MAX_NAME_ALIASES) - 1] of Char;
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Class definitions
DNS specific classes
TDNSClient = class(TNetworkClient)
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Public variables
None defined
Function declarations
Initialization functions
procedure DNSInit;
Description: To be documented
| Note | None documented |
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function DNSStart:LongWord;
Description: To be documented
| Note | None documented |
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function DNSStop:LongWord;
Description: To be documented
| Note | None documented |
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