Net::DNS::Header(3) User Contributed Perl Documentation Net::DNS::Header(3)
NAME
Net::DNS::Header - DNS packet header
SYNOPSIS
use Net::DNS;
$packet = Net::DNS::Packet->new();
$header = $packet->header;
DESCRIPTION
"Net::DNS::Header" represents the header portion of a DNS packet.
METHODS
$packet->header
$packet = Net::DNS::Packet->new();
$header = $packet->header;
Net::DNS::Header objects emanate from the Net::DNS::Packet header()
method, and contain an opaque reference to the parent Packet object.
Header objects may be assigned to suitably scoped lexical variables.
They should never be stored in global variables or persistent data
structures.
string
print $packet->header->string;
Returns a string representation of the packet header.
print
$packet->header->print;
Prints the string representation of the packet header.
id
print "query id = ", $packet->header->id, "\n";
$packet->header->id(1234);
Gets or sets the query identification number.
opcode
print "query opcode = ", $packet->header->opcode, "\n";
$packet->header->opcode("UPDATE");
Gets or sets the query opcode (the purpose of the query).
rcode
print "query response code = ", $packet->header->rcode, "\n";
$packet->header->rcode("SERVFAIL");
Gets or sets the query response code (the status of the query).
qr
print "query response flag = ", $packet->header->qr, "\n";
$packet->header->qr(0);
Gets or sets the query response flag.
aa
print "response is ", $packet->header->aa ? "" : "non-", "authoritative\n";
$packet->header->aa(0);
Gets or sets the authoritative answer flag.
tc
print "packet is ", $packet->header->tc ? "" : "not ", "truncated\n";
$packet->header->tc(0);
Gets or sets the truncated packet flag.
rd
print "recursion was ", $packet->header->rd ? "" : "not ", "desired\n";
$packet->header->rd(0);
Gets or sets the recursion desired flag.
ra
print "recursion is ", $packet->header->ra ? "" : "not ", "available\n";
$packet->header->ra(0);
Gets or sets the recursion available flag.
z
Unassigned bit, should always be zero.
ad
print "The response has ", $packet->header->ad ? "" : "not", "been verified\n";
Relevant in DNSSEC context.
(The AD bit is only set on a response where signatures have been
cryptographically verified or the server is authoritative for the data
and is allowed to set the bit by policy.)
cd
print "checking was ", $packet->header->cd ? "not" : "", "desired\n";
$packet->header->cd(0);
Gets or sets the checking disabled flag.
qdcount, zocount
print "# of question records: ", $packet->header->qdcount, "\n";
Returns the number of records in the question section of the packet.
In dynamic update packets, this field is known as "zocount" and refers
to the number of RRs in the zone section.
ancount, prcount
print "# of answer records: ", $packet->header->ancount, "\n";
Returns the number of records in the answer section of the packet which
may, in the case of corrupt packets, differ from the actual number of
records. In dynamic update packets, this field is known as "prcount"
and refers to the number of RRs in the prerequisite section.
nscount, upcount
print "# of authority records: ", $packet->header->nscount, "\n";
Returns the number of records in the authority section of the packet
which may, in the case of corrupt packets, differ from the actual
number of records. In dynamic update packets, this field is known as
"upcount" and refers to the number of RRs in the update section.
arcount, adcount
print "# of additional records: ", $packet->header->arcount, "\n";
Returns the number of records in the additional section of the packet
which may, in the case of corrupt packets, differ from the actual
number of records. In dynamic update packets, this field is known as
"adcount".
EDNS Protocol Extensions
do, co
print "DNSSEC_OK flag was ", $packet->header->do ? "not" : "", "set\n";
$packet->header->do(1);
Gets or sets the named EDNS flag.
Extended rcode
EDNS extended rcodes are handled transparently by
$packet->header->rcode().
UDP packet size
$udp_max = $packet->edns->UDPsize;
EDNS offers a mechanism to advertise the maximum UDP packet size which
can be assembled by the local network stack.
edns
$header = $packet->header;
$version = $header->edns->version;
@options = $header->edns->options;
$option = $header->edns->option(n);
$udp_max = $packet->edns->UDPsize;
Auxiliary function which provides access to the EDNS protocol extension
OPT RR.
COPYRIGHT
Copyright (c)1997 Michael Fuhr.
Portions Copyright (c)2002,2003 Chris Reinhardt.
Portions Copyright (c)2012,2022 Dick Franks.
All rights reserved.
LICENSE
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the original copyright notices appear in all copies and
that both copyright notice and this permission notice appear in
supporting documentation, and that the name of the author not be used
in advertising or publicity pertaining to distribution of the software
without specific prior written permission.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
SEE ALSO
perl(1), Net::DNS(3), Net::DNS::Packet(3), Net::DNS::RR::OPT(3),
RFC1035(4.1.1) <https://iana.org/go/rfc1035#section-4.1.1>
perl v5.34.3 2025-02-22 Net::DNS::Header(3)
net-dns 1.500.0 - Generated Sat Feb 22 08:15:18 CST 2025