Replies¶

Replies are represented by Reply objects, which hold the flags, RCODE, and three sets of returned RRs (answers, authorities and additional).

class Reply¶

flags¶

The flags returned by the server. These are as follows:

Constant Value Meaning

AA 0x0400 Authoritative Answer

TC 0x0200 Truncated Response

RD 0x0100 Recursion Desired

RA 0x0080 Recursion Allowed

Z 0x0040 Reserved

AD 0x0020 Authentic Data (DNSSEC)

CD 0x0010 Checking Disabled (DNSSEC)

rcode¶

The RCODE returned by the server. Possible values are:

Constant Value Meaning

NOERROR 0 Successful query

FORMERR 1 Format failure

SERVFAIL 2 Server failure

NXDOMAIN 3 Non-existent domain

NOTIMP 4 Not implemented

REFUSED 5 Query refursed

YXDOMAIN 6 Name exists when it should not

YXRRSET 7 RR set exists when it should not

NXRRSET 8 RR set that should exist does not

NOTAUTH 9 Server not authoritative OR Not authorized

NOTZONE 10 Name not contained in zone

BADVERS 16 Bad OPT version

BADSIG 16 TSIG signature failure

BADKEY 17 Key not recognized

BADTIME 18 Signature out of time window

BADMODE 19 Bad TKEY mode

BADNAME 20 Duplicate key name

BADALG 21 Algorithm not supported

BADTRUNC 22 Bad truncation

BADCOOKIE 23 Bad/missing server cookie

answers¶: A list of rr.RR returned by the server in the Answers section of the reply.

authorities¶: A list of rr.RR returned by the server in the Authorities section of the reply.

additional¶: A list of additional rr.RR returned by the server.

RRs¶

RRs are represented by subclasses of rr.RR; a handful of common RR types have special subclasses that decode the RDATA field in the DNS reply for you. If you are using some other type of RR, you can create your own subclass and register it using rr.RR.register(), or you can just decode the data in your own code.

class rr.RR(name, rr_type, rr_class, ttl)¶

The base class of all RRs. You won’t get a raw rr.RR in a Reply - RRs that we don’t understand are mapped to rr.Unknown.

name¶: The associated domain name, in the form given in the DNS packet (a bytes).

unicode_name¶: The associated domain name, after IDNA processing (a str)

rr_type¶: The RR type (see query for a list).

rr_class¶: The RR class (see query for a list).

ttl¶: The remaining time to live for this RR, in seconds. Note that this field is only updated

register(rr_type, rr_class, pyclass)¶

Register a subclass of rr.RR; when we decode a response from the DNS server, we will create an instance of the specified class to represent RRs of the specified type and class.

Parameters:	rr_type (int) – The RR type to map. rr_class (int) – The RR class to map, or `ANY` if the mapping should operate for any class. pyclass – The Python class we should use for RRs of the specified type and class.

decode(name, rr_type, rr_class, ttl, packet, ptr, rdlen)¶

Decode an RR from a DNS packet, returning a new rr.RR instance representing it. The implementation in rr.RR looks up the correct Python class and calls its decode() method; if it doesn’t find a class registered for the RR type with which it’s presented, it will use rr.Unknown.

Parameters:	name (bytes) – The domain name. rr_type (int) – The RR type. rr_class (int) – The RR class. ttl (int) – The remaining time to live for this RR. packet (bytes) – The entire DNS response packet. ptr (int) – The current offset within the DNS packet. rdlen (int) – The length of the RR’s data, starting from ptr.

class rr.A(name, ttl, address)¶

address¶: The IPv4 address (an ipaddress.IPv4Address).

class rr.AAAA(name, ttl, address)¶

address¶: The IPv6 address (an ipaddress.IPv6Address).

class rr.CNAME(name, ttl, address)¶

cname¶: The aliased name, in the form given in the DNS packet (a bytes).

unicode_cname¶: The aliased name after IDNA processing (a str)

class rr.HINFO(name, ttl, cpu, os)¶

cpu¶: The CPU model (as a string).

os¶: The operating system (as a string).

Note that the RFC does not specify the encoding of either string, so for maximum robustness we decode the data as ISO Latin 1. In most cases we would expect the two fields to be ASCII; if they are not, each code point in the resulting string with have the same value as the byte in the byte string.

class rr.MB(name, ttl, host)¶

host¶: The host specified in the record.

unicode_host¶: The host name after IDNA processing.

class rr.MF(name, ttl, host)¶

host¶: The host specified in the record.

unicode_host¶: The host name after IDNA processing.

class rr.MG(name, ttl, mailbox)¶

mailbox¶: The mailbox specified in the record.

unicode_mailbox¶: The mailbox name after IDNA processing.

class rr.MINFO(name, ttl, mailbox)¶

rmailbox¶

emailbox¶: The mailboxes specified in the record.

unicode_rmailbox¶

unicode_emailbox¶: The mailbox names after IDNA processing.

class rr.MR(name, ttl, mailbox)¶

mailbox¶: The mailbox specified in the record.

unicode_mailbox¶: The mailbox name after IDNA processing.

class rr.MX(name, ttl, preference, exchange)¶

preference¶: The mail exchanger priority from the DNS record.

exchange¶: The mail exchanger hostname as found in the DNS packet.

unicode_exchange¶: The mail exchanger hostname after IDNA processing.

class rr.NUL(name, ttl, data)¶

data¶: The RDATA from the record.

class rr.NS(name, ttl, host)¶

host¶: The hostname of the nameserver.

unicode_host¶: The hostname of the nameserver after IDNA processing.

class rr.PTR(name, ttl, dname)¶

address¶: The IPv4 or IPv6 address, decoded from name, or None if no address could be decoded.

dname¶: The name pointed to by this record.

unicode_host¶: The name poitned to by this record, after IDNA processing.

rr.SOA(name, ttl, mname, rname, serial, refresh, retry, expire,

minimum)

mname¶: The name of the primary mailserver for the zone.

unicode_mname¶: Same as above, but after IDNA processing.

rname¶: The mailbox name of the person responsible for the zone.

unicode_rname¶: As above, but after IDNA processing.

serial¶: The zone’s serial number; this is used to detect changes to a zone (it must be incremented every time a zone is changed).

refresh¶: The number of seconds for which a secondary nameserver may assume the zone data has not changed - controls how often the secondary checks the zone serial number.

retry¶: The number of seconds a secondary should wait to retry a refresh if the primary nameserver is busy.

expire¶: The number of seconds a secondary nameserver can cache the data before it is no longer authoritative.

minimum¶: The minimum time to live for RRs in the zone.

class rr.TXT(name, ttl, text)¶

text¶: The stored text. Since no encoding is specified, this is decoded as ISO Latin 1 (since that is the most robust option).

class rr.WKS(name, ttl, address, protocol, bitmap)¶

address¶: The IPv4 address for this record.

protocol¶: The IP protocol number for this record (typically 6, for TCP, or 17, for UDP).

bitmap¶: A bytes holding the port bitmap.

class rr.Unknown(name, ttl, rr_type, rr_class, ttl, data)¶

This subclass of rr.RR is used when we don’t know how to decode the RR found in the data packet.

data¶: The RDATA from the record.