DnsMessage Class Reference

DNS message. More...

List of all members.

Public Member Functions
	DnsMessage ()
	constructor
	~DnsMessage ()
	destructor
	stl_list (DnsQuestion) questions
	question section
	stl_list (DnsRR) answers
	answer section
	stl_list (DnsRR) authority
	authority section
	stl_list (DnsRR) additional
	additional section
void	read_from_data (char *data, int len)
	read DNS message
message_buff	compile (int maxlen)
	compile DNS message
Public Attributes
u_int16	ID
	message ID
bool	QR
	query bit
u_int4	OPCODE
	operation
bool	AA
	authoritative answer
bool	TC
	truncated
bool	RD
	recursion desired
bool	RA
	recursion available
u_int3	Z
	reserved bits
u_int4	RCODE
	return code
Protected Member Functions
void	write_section (stl_list(DnsRR)§ion, int lenpos, stl_string &message, stl_slist(dom_compr_info)&comprinfo, int maxlen, bool is_additional=false)
void	read_section (stl_list(DnsRR)§ion, int count, message_buff &buff, int &pos)

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Detailed Description

DNS message.

This structure holds a DNS message, the message type with which DNS servers talk to each other. It has member functions for reading data from binary DNS messages, and to create a binary DNS message from the structure.

Definition at line 314 of file dnsmessage.h.

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Constructor & Destructor Documentation

DnsMessage::DnsMessage (   )

constructor This constructs an empty DNS message, with all fields set to defaults.

DnsMessage::~DnsMessage (   )

destructor This destroys the DNS message.

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Member Function Documentation

message_buff DnsMessage::compile (  int  maxlen  )

compile DNS message This function will compile the DNS message into the binary format sent over UDP or TCP connections. Parameters: maxlen  Maximum length. If the message exceeds this limit, it will be cut off and the TC bit will be set. This should be 65535 for TCP messages and 512 for UDP messages. Returns: The compiled DNS message

void DnsMessage::read_from_data (  char *  data, int  len )

read DNS message This function will read DNS message information from the binary DNS message pointed to by data. Parameters: data  Binary DNS message len  Length of message

DnsMessage::stl_list (  DnsRR   )

additional section This section contains additional information that might be interesting for the client, for example addresses for NS or MX records in the answer or authority sections.

DnsMessage::stl_list (  DnsRR   )

authority section This section contains pointers to authoritative sources for the information. Most nameservers put the nameserver list for the domain names in the section here.

DnsMessage::stl_list (  DnsRR   )

answer section This section, filled by the server, contains the Resource Records that form a direct answer to the query.

DnsMessage::stl_list (  DnsQuestion   )

question section This section should contain exactly one DnsQuestion object for common DNS queries. This query is usually copied into the response by the server.

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Member Data Documentation

bool DnsMessage::AA

authoritative answer This is set to true by the server if it was authoritative for the zone the query was in. Note that, if the answer contains CNAMEs, this does not nessecarily mean the server was also authoritative for the domain the CNAME pointed to. Definition at line 365 of file dnsmessage.h.

u_int16 DnsMessage::ID

message ID This is the message ID field of the DNS message. This number is set by client software, and is copied into the response by the server in order for clients to be able to track queries. Note that the Posadis resolver sets this value for you, so there's no need to do that yourself in client applications. Definition at line 339 of file dnsmessage.h.

u_int4 DnsMessage::OPCODE

operation This is the type of operation the query is. The most common are OPCODE_QUERY for queries, OPCODE_UPDATE for dynamic updates, and OPCODE_NOTIFY for DNS notifications. Possible values are in dnsdefs.h. Definition at line 355 of file dnsmessage.h.

bool DnsMessage::QR

query bit This bit is set to false for queries, and true for answers. Definition at line 346 of file dnsmessage.h.

bool DnsMessage::RA

recursion available Set to the server indicating whether it is willing to provide recursive service. Note that, even if recursion was not desired (see RD), this value might still be set. Definition at line 392 of file dnsmessage.h.

u_int4 DnsMessage::RCODE

return code Code indicating whether the query was succesful. Some famous RCODEs, which are #defined in dnsdefs.h, are: RCODE_NOERROR to indicate success, RCODE_NXDOMAIN if the domain name queried for didn't exist, or RCODE_SERVFAIL in case of a server failure. Definition at line 411 of file dnsmessage.h.

bool DnsMessage::RD

recursion desired Set this to true to instruct the server to do recursive operation (e.g. consult other nameservers to find the right answer). Note that servers may refuse to do this, and will set the RA field accordingly. Definition at line 383 of file dnsmessage.h.

bool DnsMessage::TC

truncated Set to true by the server if the answer was cut off because it didn't fit in a UDP packet. Unless you instruct it not to, the Posadis resolver will automatically retry using TCP to get the complete answer. Definition at line 374 of file dnsmessage.h.

u_int3 DnsMessage::Z

reserved bits This the value of three currently reserved bits in the DNS message. Though these bits currently have no meaning and servers might require them to be zero, Poslib is able to read and write them. Definition at line 401 of file dnsmessage.h.

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The documentation for this class was generated from the following file:

• poslib/dnsmessage.h

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