Provided by: dnsjit_1.2.2-1_amd64 
NAME
dnsjit.core.object.dns - Container of a DNS message
SYNOPSIS
Parse DNS header and check if query or response
local dns = require("dnsjit.core.object.dns").new(payload)
if dns:parse_header() == 0 then
if dns.qr == 0 then
print(dns.id, dns.opcode_tostring(dns.opcode))
else
print(dns.id, dns.rcode_tostring(dns.rcode))
end
end
Print a DNS payload
local dns = require("dnsjit.core.object.dns").new(payload)
dns:print()
Parse a DNS payload
local dns = require("dnsjit.core.object.dns").new(payload)
local qs, q_labels, rrs, rr_labels = dns:parse()
if qs and q_labels then
...
if rrs and rr_labels then
...
end
end
DESCRIPTION
The object that describes a DNS message.
Attributes
includes_dnslen
If non-zero then this indicates that the DNS length is included in the payload (for example if the
transport is TCP) and will affect parsing of it.
have_dnslen
Set if the dnslen was included in the payload and could be read.
have_id
Set if there is a DNS ID.
have_qr
Set if there is a QR flag.
have_opcode
Set if there is an OPCODE.
have_aa
Set if there is a AA flag.
have_tc
Set if there is a TC flag.
have_rd
Set if there is a RD flag.
have_ra
Set if there is a RA flag.
have_z Set if there is a Z flag.
have_ad
Set if there is a AD flag.
have_cd
Set if there is a CD flag.
have_rcode
Set if there is a RCODE.
have_qdcount
Set if there is an QDCOUNT.
have_ancount
Set if there is an ANCOUNT.
have_nscount
Set if there is a NSCOUNT.
have_arcount
Set if there is an ARCOUNT.
dnslen The DNS length found in the payload.
id The DNS ID.
qr The QR flag.
opcode The OPCODE.
aa The AA flag.
tc The TC flag.
rd The RD flag.
ra The RA flag.
z The Z flag.
ad The AD flag.
cd The CD flag.
rcode The RCODE.
qdcount
The QDCOUNT.
ancount
The ANCOUNT.
nscount
The NSCOUNT.
arcount
The ARCOUNT.
Constants
The following tables exists for DNS parameters, taken from https://www.iana.org/assignments/dns-
parameters/dns-parameters.xhtml on the 2016-12-09.
CLASS, CLASS_STR, TYPE, TYPE_STR, OPCODE, OPCODE_STR, RCODE, RCODE_STR, AFSDB, AFSDB_STR, DHCID,
DHCID_STR, ENDS0, ENDS0_STR
The *_STR tables can be used to get a textual representation of the numbers, see also class_tostring(),
type_tostring(), opcode_tostring(), rcode_tostring(), afsdb_tostring(), dhcid_tostring() and
edns0_tostring().
Functions
Dns.new(obj)
Create a new DNS object, optionally on-top of another object.
Dns:type()
Return the textual type of the object.
Dns:prev()
Return the previous object.
Dns:cast()
Cast the object to the underlining object module and return it.
Dns:uncast()
Cast the object to the generic object module and return it.
Dns:copy()
Make a copy of the object and return it.
Dns:free()
Free the object, should only be used on copies or otherwise allocated.
Dns:log()
Return the Log object to control logging of this module.
Dns:parse_header()
Begin parsing the underlaying object, first the header is parsed then optionally continue calling
parse_q() for the number of questions (see qdcount). After that continue calling parse_rr() for
the number of answers, authorities and additionals resource records (see ancount, nscount and
arcount). Returns 0 on success or negative integer on error which can be for malformed or
truncated DNS (-2) or if more space for labels is needed (-3).
Dns:parse_q(q, labels, num_labels)
Parse the next resource record as a question. Returns 0 on success or negative integer on error
which can be for malformed or truncated DNS (-2) or if more space for labels is needed (-3).
Dns:parse_rr(rr, labels, num_labels)
Parse the next resource record. Returns 0 on success or negative integer on error which can be
for malformed or truncated DNS (-2) or if more space for labels is needed (-3).
Dns:parse(num_labels)
Begin parsing the underlaying object using parse_header(), parse_q() and parse_rr(). The optional
num_labels can be used to set a specific number of labels used for each question and resource
record (default 16). Returns result code, an array of questions, an array of question labels, an
array of resource records and an array of resource records labels. Result code is 0 on success or
negative integer on error which can be for malformed or truncated DNS (-2) or if more space for
labels is needed (-3).
Dns:print(num_labels)
Begin parsing the underlaying object using parse_header(), parse_q() and parse_rr(), and print
it's content. The optional num_labels can be used to set a specific number of labels used for
each question and resource record (default 16).
Dns.class_tostring(class)
Return the textual name for a class.
Dns.type_tostring(type)
Return the textual name for a type.
Dns.opcode_tostring(opcode)
Return the textual name for an opcode.
Dns.rcode_tostring(rcode)
Return the textual name for a rcode.
Dns.afsdb_tostring(afsdb)
Return the textual name for an afsdb subtype.
Dns.dhcid_tostring(dhcid)
Return the textual name for a dhcid type.
Dns.edns0_tostring(edns0)
Return the textual name for an EDNS0 OPT record.
SEE ALSO
dnsjit.core.object(3), dnsjit.core.object.payload(3), dnsjit.core.object.dns.label(3),
dnsjit.core.object.dns.q(3), dnsjit.core.object.dns.rr(3)
AUTHORS and CONTRIBUTORS
Jerry Lundström (DNS-OARC), Tomáš Křížek (CZ.NIC), Petr Špaček (ISC)
Maintained by DNS-OARC
https://www.dns-oarc.net/
BUGS
For issues and feature requests please use:
https://github.com/DNS-OARC/dnsjit/issues
For question and help please use:
admin@dns-oarc.net
dnsjit 1.2.2 dnsjit.core.object.dns(3)