path: root/src/lib/util/python/gen_wiredata.py.in

#!@PYTHON@

# Copyright (C) 2010  Internet Systems Consortium.
#
# Permission to use, copy, modify, and distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SYSTEMS CONSORTIUM
# DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
# INTERNET SYSTEMS CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
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# FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
# NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
# WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

"""
Generator of various types of DNS data in the hex format.

This script reads a human readable specification file (called "spec
file" hereafter) that defines some type of DNS data (an RDATA, an RR,
or a complete message) and dumps the defined data to a separate file
as a "wire format" sequence parsable by the
UnitTestUtil::readWireData() function (currently defined as part of
libdns++ tests).  Many DNS related tests involve wire format test
data, so it will be convenient if we can define the data in a more
intuitive way than writing the entire hex sequence by hand.

Here is a simple example.  Consider the following spec file:

  [custom]
  sections: a
  [a]
  as_rr: True

When the script reads this file, it detects the file specifies a single
component (called "section" here) that consists of a single A RDATA,
which must be dumped as an RR (not only the part of RDATA).  It then
dumps the following content:

  # A RR (QNAME=example.com Class=IN(1) TTL=86400 RDLEN=4)
  076578616d706c6503636f6d00 0001 0001 00015180 0004
  # Address=192.0.2.1
  c0000201

As can be seen, the script automatically completes all variable
parameters of RRs: owner name, class, TTL, RDATA length and data.  For
testing purposes many of these will be the same common one (like
"example.com" or 192.0.2.1), so it would be convenient if we only have
to specify non default parameters.  To change the RDATA (i.e., the
IPv4 address), we should add the following line at the end of the spec
file:

  address: 192.0.2.2

Then the last two lines of the output file will be as follows:

  # Address=192.0.2.2
  c0000202

In some cases we would rather specify malformed data for tests.  This
script has the ability to specify broken parameters for many types of
data.  For example, we can generate data that would look like an A RR
but the RDLEN is 3 by adding the following line to the spec file:

  rdlen: 3

Then the first two lines of the output file will be as follows:

  # A RR (QNAME=example.com Class=IN(1) TTL=86400 RDLEN=3)
  076578616d706c6503636f6d00 0001 0001 00015180 0003

** USAGE **

  gen_wiredata.py [-o output_file] spec_file

If the -o option is missing, and if the spec_file has a suffix (such as
in the form of "data.spec"), the output file name will be the prefix
part of it (as in "data"); if -o is missing and the spec_file does not
have a suffix, the script will fail.

** SPEC FILE SYNTAX **

A spec file accepted in this script should be in the form of a
configuration file that is parsable by the Python's standard
configparser module.  In short, it consists of sections; each section
is identified in the form of [section_name] followed by "name: value"
entries.  Lines beginning with # or ; will be treated as comments.
Refer to the configparser module documentation for further details of
the general syntax.

This script has two major modes: the custom mode and the DNS query
mode.  The former generates an arbitrary combination of DNS message
header, question section, RDATAs or RRs.  It is mainly intended to
generate a test data for a single type of RDATA or RR, or for
complicated complete DNS messages.  The DNS query mode is actually a
special case of the custom mode, which is a shortcut to generate a
simple DNS query message (with or without EDNS).

* Custom mode syntax *

By default this script assumes the DNS query mode.  To specify the
custom mode, there must be a special "custom" section in the spec
file, which should contain 'sections' entry.  This value of this
entryis colon-separated string fields, each of which is either
"header", "question", "edns", "name", or a string specifying an RR
type.  For RR types the string is lower-cased string mnemonic that
identifies the type: 'a' for type A, 'ns' for type NS, and so on
(note: in the current implementation it's case sensitive, and must be
lower cased).

Each of these fields is interpreted as a section name of the spec
(configuration), and in that section parameters specific to the
semantics of the field can be configured.

A "header" section specifies the content of a DNS message header.
See the documentation of the DNSHeader class of this module for
configurable parameters.

A "question" section specifies the content of a single question that
is normally to be placed in the Question section of a DNS message.
See the documentation of the DNSQuestion class of this module for
configurable parameters.

An "edns" section specifies the content of an EDNS OPT RR.  See the
documentation of the EDNS class of this module for configurable
parameters.

A "name" section specifies a domain name with or without compression.
This is specifically intended to be used for testing name related
functionalities and would rarely be used with other sections.  See the
documentation of the Name class of this module for configurable
parameters.

In a specific section for an RR or RDATA, possible entries depend on
the type.  But there are some common configurable entries.  See the
description of the RR class.  The most important one would be "as_rr".
It controls whether the entry should be treated as an RR (with name,
type, class and TTL) or only as an RDATA.  By default as_rr is
"False", so if an entry is to be interpreted as an RR, an as_rr entry
must be explicitly specified with a value of "True".

Another common entry is "rdlen".  It specifies the RDLEN field value
of the RR (note: this is included when the entry is interpreted as
RDATA, too).  By default this value is automatically determined by the
RR type and (it has a variable length) from other fields of RDATA, but
as shown in the above example, it can be explicitly set, possibly to a
bogus value for testing against invalid data.

For type specific entries (and their defaults when provided), see the
documentation of the corresponding Python class defined in this
module.  In general, there should be a class named the same mnemonic
of the corresponding RR type for each supported type, and they are a
subclass of the RR class.  For example, the "NS" class is defined for
RR type NS.

Look again at the A RR example shown at the beginning of this
description.  There's a "custom" section, which consists of a
"sections" entry whose value is a single "a", which means the data to
be generated is an A RR or RDATA.  There's a corresponding "a"
section, which only specifies that it should be interpreted as an RR
(all field values of the RR are derived from the default).

If you want to generate a data sequence for two ore more RRs or
RDATAs, you can specify them in the form of colon-separated fields for
the "sections" entry.  For example, to generate a sequence of A and NS
RRs in that order, the "custom" section would be something like this:

  [custom]
  sections: a:ns

and there must be an "ns" section in addtion to "a".

If a sequence of two or more RRs/RDATAs of the same RR type should be
generated, these should be uniquely indexed with the "/" separator.
For example, to generate two A RRs, the "custom" section would be as
follows:

  [custom]
  sections: a/1:a/2

and there must be "a/1" and "a/2" sections.

Another practical example that would be used for many tests is to
generate data for a complete DNS ressponse message.  The spec file of
such an example configuration would look like as follows:

  [custom]
  sections: header:question:a
  [header]
  qr: 1
  ancount: 1
  [question]
  [a]
  as_rr: True

With this configuration, this script will generate test data for a DNS
response to a query for example.com/IN/A containing one corresponding
A RR in the answer section.

* DNS query mode syntax *

If the spec file does not contain a "custom" section (that has a
"sections" entry), this script assumes the DNS query mode.  This mode
is actually a special case of custom mode; it implicitly assumes the
"sections" entry whose value is "header:question:edns".

In this mode it is expected that the spec file also contains at least
a "header" and "question" sections, and optionally an "edns" section.
But the script does not warn or fail even if the expected sections are
missing.

* Entry value types *

As described above, a section of the spec file accepts entries
specific to the semantics of the section.  They generally correspond
to DNS message or RR fields.

Many of them are expected to be integral values, for which either decimal or
hexadecimal representation is accepted, for example:

  rr_ttl: 3600
  tag: 0x1234

Some others are expected to be string.  A string value does not have
to be quated:

  address: 192.0.2.2

but can also be quoated with single quotes:

  address: '192.0.2.2'

Note 1: a string that can be interpreted as an integer must be quated.
For example, if you want to set a "string" entry to "3600", it should
be:

  string: '3600'

instead of

  string: 3600

Note 2: a string enclosed with double quotes is not accepted:

  # This doesn't work:
  address: "192.0.2.2"

In general, string values are converted to hexadecimal sequences
according to the semantics of the entry.  For instance, a textual IPv4
address in the above example will be converted to a hexadecimal
sequence corresponding to a 4-byte integer.  So, in many cases, the
acceptable syntax for a particular string entry value should be
obvious from the context.  There are still some exceptional cases
especially for complicated RR field values, for which the
corresponding class documentation should be referenced.

One special string syntax that would be worth noting is domain names,
which would natually be used in many kinds of entries.  The simplest
form of acceptable syntax is a textual representation of domain names
such as "example.com" (note: names are always assumed to be
"absolute", so the trailing dot can be omitted).  But a domain name in
the wire format can also contain a compression pointer.  This script
provides a simple support for name compression with a special notation
of "ptr=nn" where nn is the numeric pointer value (decimal).  For example,
if the NSDNAME field of an NS RDATA is specified as follows:

  nsname: ns.ptr=12

this script will generate the following output:

  # NS name=ns.ptr=12
  026e73c00c

** EXTEND THE SCRIPT **

This script is expected to be extended as we add more support for
various types of RR.  It is encouraged to add support for a new type
of RR to this script as we see the need for testing that type.  Here
is a simple instruction of how to do that.

Assume you are adding support for "FOO" RR.  Also assume that the FOO
RDATA contains a single field named "value".

What you are expected to do is as follows:

- Define a new class named "FOO" inherited from the RR class.  Also
  define a class variable named "value" for the FOO RDATA field (the
  variable name can be different from the field name, but it's
  convenient if it can be easily identifiable.) with an appropriate
  default value (if possible):

    class FOO(RR):
        value = 10

  The name of the variable will be (automatically) used as the
  corresponding entry name in the spec file.  So, a spec file that
  sets this field to 20 would look like this:

    [foo]
    value: 20

- Define the "dump()" method for class FOO.  It must call
  self.dump_header() (which is derived from class RR) at the
  beginning.  It then prints the RDATA field values in an appropriate
  way.  Assuming the value is a 16-bit integer field, a complete
  dump() method would look like this:

    def dump(self, f):
        if self.rdlen is None:
            self.rdlen = 2
        self.dump_header(f, self.rdlen)
        f.write('# Value=%d\\n' % (self.value))
        f.write('%04x\\n' % (self.value))

  The first f.write() call is not mandatory, but is encouraged to
  be provided so that the generated files will be more human readable.
  Depending on the complexity of the RDATA fields, the dump()
  implementation would be more complicated.  In particular, if the
  RDATA length is variable and the RDLEN field value is not specified
  in the spec file, the dump() method is normally expected to
  calculate the correct length and pass it to dump_header().  See the
  implementation of various derived classes of class RR for actual
  examples.
"""

import configparser, re, time, socket, sys, base64
from datetime import datetime
from optparse import OptionParser

re_hex = re.compile(r'^0x[0-9a-fA-F]+')
re_decimal = re.compile(r'^\d+$')
re_string = re.compile(r"\'(.*)\'$")

dnssec_timefmt = '%Y%m%d%H%M%S'

dict_qr = { 'query' : 0, 'response' : 1 }
dict_opcode = { 'query' : 0, 'iquery' : 1, 'status' : 2, 'notify' : 4,
                'update' : 5 }
rdict_opcode = dict([(dict_opcode[k], k.upper()) for k in dict_opcode.keys()])
dict_rcode = { 'noerror' : 0, 'formerr' : 1, 'servfail' : 2, 'nxdomain' : 3,
               'notimp' : 4, 'refused' : 5, 'yxdomain' : 6, 'yxrrset' : 7,
               'nxrrset' : 8, 'notauth' : 9, 'notzone' : 10 }
rdict_rcode = dict([(dict_rcode[k], k.upper()) for k in dict_rcode.keys()])
dict_rrtype = { 'none' : 0, 'a' : 1, 'ns' : 2, 'md' : 3, 'mf' : 4, 'cname' : 5,
                'soa' : 6, 'mb' : 7, 'mg' : 8, 'mr' : 9, 'null' : 10,
                'wks' : 11, 'ptr' : 12, 'hinfo' : 13, 'minfo' : 14, 'mx' : 15,
                'txt' : 16, 'rp' : 17, 'afsdb' : 18, 'x25' : 19, 'isdn' : 20,
                'rt' : 21, 'nsap' : 22, 'nsap_tr' : 23, 'sig' : 24, 'key' : 25,
                'px' : 26, 'gpos' : 27, 'aaaa' : 28, 'loc' : 29, 'nxt' : 30,
                'srv' : 33, 'naptr' : 35, 'kx' : 36, 'cert' : 37, 'a6' : 38,
                'dname' : 39, 'opt' : 41, 'apl' : 42, 'ds' : 43, 'sshfp' : 44,
                'ipseckey' : 45, 'rrsig' : 46, 'nsec' : 47, 'dnskey' : 48,
                'dhcid' : 49, 'nsec3' : 50, 'nsec3param' : 51, 'hip' : 55,
                'spf' : 99, 'unspec' : 103, 'tkey' : 249, 'tsig' : 250,
                'dlv' : 32769, 'ixfr' : 251, 'axfr' : 252, 'mailb' : 253,
                'maila' : 254, 'any' : 255 }
rdict_rrtype = dict([(dict_rrtype[k], k.upper()) for k in dict_rrtype.keys()])
dict_rrclass = { 'in' : 1, 'ch' : 3, 'hs' : 4, 'any' : 255 }
rdict_rrclass = dict([(dict_rrclass[k], k.upper()) for k in \
                          dict_rrclass.keys()])
dict_algorithm = { 'rsamd5' : 1, 'dh' : 2, 'dsa' : 3, 'ecc' : 4,
                   'rsasha1' : 5 }
dict_nsec3_algorithm = { 'reserved' : 0, 'sha1' : 1 }
rdict_algorithm = dict([(dict_algorithm[k], k.upper()) for k in \
                            dict_algorithm.keys()])
rdict_nsec3_algorithm = dict([(dict_nsec3_algorithm[k], k.upper()) for k in \
                                  dict_nsec3_algorithm.keys()])

header_xtables = { 'qr' : dict_qr, 'opcode' : dict_opcode,
                   'rcode' : dict_rcode }
question_xtables = { 'rrtype' : dict_rrtype, 'rrclass' : dict_rrclass }

def parse_value(value, xtable = {}):
    if re.search(re_hex, value):
        return int(value, 16)
    if re.search(re_decimal, value):
        return int(value)
    m = re.match(re_string, value)
    if m:
        return m.group(1)
    lovalue = value.lower()
    if lovalue in xtable:
        return xtable[lovalue]
    return value

def code_totext(code, dict):
    if code in dict.keys():
        return dict[code] + '(' + str(code) + ')'
    return str(code)

def encode_name(name, absolute=True):
    # make sure the name is dot-terminated.  duplicate dots will be ignored
    # below.
    name += '.'
    labels = name.split('.')
    wire = ''
    for l in labels:
        if len(l) > 4 and l[0:4] == 'ptr=':
            # special meta-syntax for compression pointer
            wire += '%04x' % (0xc000 | int(l[4:]))
            break
        if absolute or len(l) > 0:
            wire += '%02x' % len(l)
            wire += ''.join(['%02x' % ord(ch) for ch in l])
        if len(l) == 0:
            break
    return wire

def encode_string(name, len=None):
    if type(name) is int and len is not None:
        return '%0.*x' % (len * 2, name)
    return ''.join(['%02x' % ord(ch) for ch in name])

def encode_bytes(name, len=None):
    if type(name) is int and len is not None:
        return '%0.*x' % (len * 2, name)
    return ''.join(['%02x' % ch for ch in name])

def count_namelabels(name):
    if name == '.':             # special case
        return 0
    m = re.match('^(.*)\.$', name)
    if m:
        name = m.group(1)
    return len(name.split('.'))

def get_config(config, section, configobj, xtables = {}):
    try:
        for field in config.options(section):
            value = config.get(section, field)
            if field in xtables.keys():
                xtable = xtables[field]
            else:
                xtable = {}
            configobj.__dict__[field] = parse_value(value, xtable)
    except configparser.NoSectionError:
        return False
    return True

def print_header(f, input_file):
    f.write('''###
### This data file was auto-generated from ''' + input_file + '''
###
''')

class Name:
    '''Implements rendering a single domain name in the test data format.

    Configurable parameter is as follows (see the description of the
    same name of attribute for the default value):
    - name (string): A textual representation of the name, such as
      'example.com'.
    - pointer (int): If specified, compression pointer will be
      prepended to the generated data with the offset being the value
      of this parameter.
    '''

    name = 'example.com'
    pointer = None                # no compression by default
    def dump(self, f):
        name = self.name
        if self.pointer is not None:
            if len(name) > 0 and name[-1] != '.':
                name += '.'
            name += 'ptr=%d' % self.pointer
        name_wire = encode_name(name)
        f.write('\n# DNS Name: %s' % self.name)
        if self.pointer is not None:
            f.write(' + compression pointer: %d' % self.pointer)
        f.write('\n')
        f.write('%s' % name_wire)
        f.write('\n')

class DNSHeader:
    '''Implements rendering a DNS Header section in the test data format.

    Configurable parameter is as follows (see the description of the
    same name of attribute for the default value):
    - id (16-bit int):
    - qr, aa, tc, rd, ra, ad, cd (0 or 1): Standard header bits as
      defined in RFC1035 and RFC4035.  If set to 1, the corresponding
      bit will be set; if set to 0, it will be cleared.
    - mbz (0-3): The reserved field of the 3rd and 4th octets of the
      header.
    - rcode (4-bit int or string): The RCODE field.  If specified as a
      string, it must be the commonly used textual mnemonic of the RCODEs
      (NOERROR, FORMERR, etc, case insensitive).
    - opcode (4-bit int or string): The OPCODE field.  If specified as
      a string, it must be the commonly used textual mnemonic of the
      OPCODEs (QUERY, NOTIFY, etc, case insensitive).
    - qdcount, ancount, nscount, arcount (16-bit int): The QD/AN/NS/AR
      COUNT fields, respectively.
    '''

    id = 0x1035
    (qr, aa, tc, rd, ra, ad, cd) = 0, 0, 0, 0, 0, 0, 0
    mbz = 0
    rcode = 0                   # noerror
    opcode = 0                  # query
    (qdcount, ancount, nscount, arcount) = 1, 0, 0, 0

    def dump(self, f):
        f.write('\n# Header Section\n')
        f.write('# ID=' + str(self.id))
        f.write(' QR=' + ('Response' if self.qr else 'Query'))
        f.write(' Opcode=' + code_totext(self.opcode, rdict_opcode))
        f.write(' Rcode=' + code_totext(self.rcode, rdict_rcode))
        f.write('%s' % (' AA' if self.aa else ''))
        f.write('%s' % (' TC' if self.tc else ''))
        f.write('%s' % (' RD' if self.rd else ''))
        f.write('%s' % (' AD' if self.ad else ''))
        f.write('%s' % (' CD' if self.cd else ''))
        f.write('\n')
        f.write('%04x ' % self.id)
        flag_and_code = 0
        flag_and_code |= (self.qr << 15 | self.opcode << 14 | self.aa << 10 |
                          self.tc << 9 | self.rd << 8 | self.ra << 7 |
                          self.mbz << 6 | self.ad << 5 | self.cd << 4 |
                          self.rcode)
        f.write('%04x\n' % flag_and_code)
        f.write('# QDCNT=%d, ANCNT=%d, NSCNT=%d, ARCNT=%d\n' %
                (self.qdcount, self.ancount, self.nscount, self.arcount))
        f.write('%04x %04x %04x %04x\n' % (self.qdcount, self.ancount,
                                           self.nscount, self.arcount))

class DNSQuestion:
    '''Implements rendering a DNS question in the test data format.

    Configurable parameter is as follows (see the description of the
    same name of attribute for the default value):
    - name (string): The QNAME.  The string must be interpreted as a
      valid domain name.
    - rrtype (int or string): The question type.  If specified
      as an integer, it must be the 16-bit RR type value of the
      covered type.  If specifed as a string, it must be the textual
      mnemonic of the type.
    - rrclass (int or string): The question class.  If specified as an
      integer, it must be the 16-bit RR class value of the covered
      type.  If specifed as a string, it must be the textual mnemonic
      of the class.
    '''
    name = 'example.com.'
    rrtype = parse_value('A', dict_rrtype)
    rrclass = parse_value('IN', dict_rrclass)

    def dump(self, f):
        f.write('\n# Question Section\n')
        f.write('# QNAME=%s QTYPE=%s QCLASS=%s\n' %
                (self.name,
                 code_totext(self.rrtype, rdict_rrtype),
                 code_totext(self.rrclass, rdict_rrclass)))
        f.write(encode_name(self.name))
        f.write(' %04x %04x\n' % (self.rrtype, self.rrclass))

class EDNS:
    '''Implements rendering EDNS OPT RR in the test data format.

    Configurable parameter is as follows (see the description of the
    same name of attribute for the default value):
    - name (string): The owner name of the OPT RR.  The string must be
      interpreted as a valid domain name.
    - udpsize (16-bit int): The UDP payload size (set as the RR class)
    - extrcode (8-bit int): The upper 8 bits of the extended RCODE.
    - version (8-bit int): The EDNS version.
    - do (int): The DNSSEC DO bit.  The bit will be set if this value
      is 1; otherwise the bit will be unset.
    - mbz (15-bit int): The rest of the flags field.
    - rdlen (16-bit int): The RDLEN field.  Note: right now specifying
      a non 0 value (except for making bogus data) doesn't make sense
      because there is no way to configure RDATA.
    '''
    name = '.'
    udpsize = 4096
    extrcode = 0
    version = 0
    do = 0
    mbz = 0
    rdlen = 0
    def dump(self, f):
        f.write('\n# EDNS OPT RR\n')
        f.write('# NAME=%s TYPE=%s UDPSize=%d ExtRcode=%s Version=%s DO=%d\n' %
                (self.name, code_totext(dict_rrtype['opt'], rdict_rrtype),
                 self.udpsize, self.extrcode, self.version,
                 1 if self.do else 0))
        
        code_vers = (self.extrcode << 8) | (self.version & 0x00ff)
        extflags = (self.do << 15) | (self.mbz & ~0x8000)
        f.write('%s %04x %04x %04x %04x\n' %
                (encode_name(self.name), dict_rrtype['opt'], self.udpsize,
                 code_vers, extflags))
        f.write('# RDLEN=%d\n' % self.rdlen)
        f.write('%04x\n' % self.rdlen)

class RR:
    '''This is a base class for various types of RR test data.
    For each RR type (A, AAAA, NS, etc), we define a derived class of RR
    to dump type specific RDATA parameters.  This class defines parameters
    common to all types of RDATA, namely the owner name, RR class and TTL.
    The dump() method of derived classes are expected to call dump_header(),
    whose default implementation is provided in this class.  This method
    decides whether to dump the test data as an RR (with name, type, class)
    or only as RDATA (with its length), and dumps the corresponding data
    via the specified file object.

    By convention we assume derived classes are named after the common
    standard mnemonic of the corresponding RR types.  For example, the
    derived class for the RR type SOA should be named "SOA".

    Configurable parameters are as follows:
    - as_rr (bool): Whether or not the data is to be dumped as an RR.
      False by default.
    - rr_name (string): The owner name of the RR.  The string must be
      interpreted as a valid domain name (compression pointer can be
      contained).  Default is 'example.com.'
    - rr_class (string): The RR class of the data.  Only meaningful
      when the data is dumped as an RR.  Default is 'IN'.
    - rr_ttl (int): The TTL value of the RR.  Only meaningful when
      the data is dumped as an RR.  Default is 86400 (1 day).
    - rdlen (int): 16-bit RDATA length.  It can be None (i.e. omitted
      in the spec file), in which case the actual length of the
      generated RDATA is automatically determined and used; if
      negative, the RDLEN field will be omitted from the output data.
      (Note that omitting RDLEN with as_rr being True is mostly
      meaningless, although the script doesn't complain about it).
      Default is None.
    '''

    def __init__(self):
        self.as_rr = False
        # only when as_rr is True, same for class/TTL:
        self.rr_name = 'example.com'
        self.rr_class = 'IN'
        self.rr_ttl = 86400
        self.rdlen = None

    def dump_header(self, f, rdlen):
        type_txt = self.__class__.__name__
        type_code = parse_value(type_txt, dict_rrtype)
        rdlen_spec = ''
        rdlen_data = ''
        if rdlen >= 0:
            rdlen_spec = ', RDLEN=%d' % rdlen
            rdlen_data = '%04x' % rdlen
        if self.as_rr:
            rrclass = parse_value(self.rr_class, dict_rrclass)
            f.write('\n# %s RR (QNAME=%s Class=%s TTL=%d%s)\n' %
                    (type_txt, self.rr_name,
                     code_totext(rrclass, rdict_rrclass), self.rr_ttl,
                     rdlen_spec))
            f.write('%s %04x %04x %08x %s\n' %
                    (encode_name(self.rr_name), type_code, rrclass,
                     self.rr_ttl, rdlen_data))
        else:
            f.write('\n# %s RDATA%s\n' % (type_txt, rdlen_spec))
            f.write('%s\n' % rdlen_data)

class A(RR):
    '''Implements rendering A RDATA (of class IN) in the test data format.

    Configurable parameter is as follows (see the description of the
    same name of attribute for the default value):
    - address (string): The address field.  This must be a valid textual
      IPv4 address.
    '''
    RDLEN_DEFAULT = 4           # fixed by default
    address = '192.0.2.1'

    def dump(self, f):
        if self.rdlen is None:
            self.rdlen = self.RDLEN_DEFAULT
        self.dump_header(f, self.rdlen)
        f.write('# Address=%s\n' % (self.address))
        bin_address = socket.inet_aton(self.address)
        f.write('%02x%02x%02x%02x\n' % (bin_address[0], bin_address[1],
                                        bin_address[2], bin_address[3]))

class AAAA(RR):
    '''Implements rendering AAAA RDATA (of class IN) in the test data
    format.

    Configurable parameter is as follows (see the description of the
    same name of attribute for the default value):
    - address (string): The address field.  This must be a valid textual
      IPv6 address.
    '''
    RDLEN_DEFAULT = 16          # fixed by default
    address = '2001:db8::1'

    def dump(self, f):
        if self.rdlen is None:
            self.rdlen = self.RDLEN_DEFAULT
        self.dump_header(f, self.rdlen)
        f.write('# Address=%s\n' % (self.address))
        bin_address = socket.inet_pton(socket.AF_INET6, self.address)
        [f.write('%02x' % x) for x in bin_address]
        f.write('\n')

class NS(RR):
    '''Implements rendering NS RDATA in the test data format.

    Configurable parameter is as follows (see the description of the
    same name of attribute for the default value):
    - nsname (string): The NSDNAME field.  The string must be
      interpreted as a valid domain name.
    '''

    nsname = 'ns.example.com'

    def dump(self, f):
        nsname_wire = encode_name(self.nsname)
        if self.rdlen is None:
            self.rdlen = len(nsname_wire) / 2
        self.dump_header(f, self.rdlen)
        f.write('# NS name=%s\n' % (self.nsname))
        f.write('%s\n' % nsname_wire)

class SOA(RR):
    '''Implements rendering SOA RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - mname/rname (string): The MNAME/RNAME fields, respectively.  The
      string must be interpreted as a valid domain name.
    - serial (32-bit int): The SERIAL field
    - refresh (32-bit int): The REFRESH field
    - retry (32-bit int): The RETRY field
    - expire (32-bit int): The EXPIRE field
    - minimum (32-bit int): The MINIMUM field
    '''

    mname = 'ns.example.com'
    rname = 'root.example.com'
    serial = 2010012601
    refresh = 3600
    retry = 300
    expire = 3600000
    minimum = 1200
    def dump(self, f):
        mname_wire = encode_name(self.mname)
        rname_wire = encode_name(self.rname)
        if self.rdlen is None:
            self.rdlen = int(20 + len(mname_wire) / 2 + len(str(rname_wire)) / 2)
        self.dump_header(f, self.rdlen)
        f.write('# NNAME=%s RNAME=%s\n' % (self.mname, self.rname))
        f.write('%s %s\n' % (mname_wire, rname_wire))
        f.write('# SERIAL(%d) REFRESH(%d) RETRY(%d) EXPIRE(%d) MINIMUM(%d)\n' %
                (self.serial, self.refresh, self.retry, self.expire,
                 self.minimum))
        f.write('%08x %08x %08x %08x %08x\n' % (self.serial, self.refresh,
                                                self.retry, self.expire,
                                                self.minimum))

class TXT(RR):
    '''Implements rendering TXT RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - nstring (int): number of character-strings
    - stringlenN (int) (int, N = 0, ..., nstring-1): the length of the
      N-th character-string.
    - stringN (string, N = 0, ..., nstring-1): the N-th
      character-string.
    - stringlen (int): the default string.  If nstring >= 1 and the
      corresponding stringlenN isn't specified in the spec file, this
      value will be used.  If this parameter isn't specified either,
      the length of the string will be used.  Note that it means
      this parameter (or any stringlenN) doesn't have to be specified
      unless you want to intentionally build a broken character string.
    - string (string): the default string.  If nstring >= 1 and the
      corresponding stringN isn't specified in the spec file, this
      string will be used.
    '''

    nstring = 1
    stringlen = None
    string = 'Test-String'

    def dump(self, f):
        stringlen_list = []
        string_list = []
        wirestring_list = []
        for i in range(0, self.nstring):
            key_string = 'string' + str(i)
            if key_string in self.__dict__:
                string_list.append(self.__dict__[key_string])
            else:
                string_list.append(self.string)
            wirestring_list.append(encode_string(string_list[-1]))
            key_stringlen = 'stringlen' + str(i)
            if key_stringlen in self.__dict__:
                stringlen_list.append(self.__dict__[key_stringlen])
            else:
                stringlen_list.append(self.stringlen)
            if stringlen_list[-1] is None:
                stringlen_list[-1] = int(len(wirestring_list[-1]) / 2)
        if self.rdlen is None:
            self.rdlen = int(len(''.join(wirestring_list)) / 2) + self.nstring
        self.dump_header(f, self.rdlen)
        for i in range(0, self.nstring):
            f.write('# String Len=%d, String=\"%s\"\n' %
                    (stringlen_list[i], string_list[i]))
            f.write('%02x%s%s\n' % (stringlen_list[i],
                                    ' ' if len(wirestring_list[i]) > 0 else '',
                                    wirestring_list[i]))

class RP(RR):
    '''Implements rendering RP RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - mailbox (string): The mailbox field.
    - text (string): The text field.
    These strings must be interpreted as a valid domain name.
    '''
    mailbox = 'root.example.com'
    text = 'rp-text.example.com'
    def dump(self, f):
        mailbox_wire = encode_name(self.mailbox)
        text_wire = encode_name(self.text)
        if self.rdlen is None:
            self.rdlen = (len(mailbox_wire) + len(text_wire)) / 2
        else:
            self.rdlen = int(self.rdlen)
        self.dump_header(f, self.rdlen)
        f.write('# MAILBOX=%s TEXT=%s\n' % (self.mailbox, self.text))
        f.write('%s %s\n' % (mailbox_wire, text_wire))

class SSHFP(RR):
    '''Implements rendering SSHFP RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - algorithm (int): The algorithm number.
    - fingerprint_type (int): The fingerprint type.
    - fingerprint (string): The fingerprint.
    '''
    algorithm = 2
    fingerprint_type = 1
    fingerprint = '123456789abcdef67890123456789abcdef67890'
    def dump(self, f):
        if self.rdlen is None:
            self.rdlen = 2 + (len(self.fingerprint) / 2)
        else:
            self.rdlen = int(self.rdlen)
        self.dump_header(f, self.rdlen)
        f.write('# ALGORITHM=%d FINGERPRINT_TYPE=%d FINGERPRINT=%s\n' % (self.algorithm,
                                                                         self.fingerprint_type,
                                                                         self.fingerprint))
        f.write('%02x %02x %s\n' % (self.algorithm, self.fingerprint_type, self.fingerprint))

class MINFO(RR):
    '''Implements rendering MINFO RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - rmailbox (string): The rmailbox field.
    - emailbox (string): The emailbox field.
    These strings must be interpreted as a valid domain name.
    '''
    rmailbox = 'rmailbox.example.com'
    emailbox = 'emailbox.example.com'
    def dump(self, f):
        rmailbox_wire = encode_name(self.rmailbox)
        emailbox_wire = encode_name(self.emailbox)
        if self.rdlen is None:
            self.rdlen = (len(rmailbox_wire) + len(emailbox_wire)) / 2
        else:
            self.rdlen = int(self.rdlen)
        self.dump_header(f, self.rdlen)
        f.write('# RMAILBOX=%s EMAILBOX=%s\n' % (self.rmailbox, self.emailbox))
        f.write('%s %s\n' % (rmailbox_wire, emailbox_wire))

class AFSDB(RR):
    '''Implements rendering AFSDB RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - subtype (16 bit int): The subtype field.
    - server (string): The server field.
    The string must be interpreted as a valid domain name.
    '''
    subtype = 1
    server = 'afsdb.example.com'
    def dump(self, f):
        server_wire = encode_name(self.server)
        if self.rdlen is None:
            self.rdlen = 2 + len(server_wire) / 2
        else:
            self.rdlen = int(self.rdlen)
        self.dump_header(f, self.rdlen)
        f.write('# SUBTYPE=%d SERVER=%s\n' % (self.subtype, self.server))
        f.write('%04x %s\n' % (self.subtype, server_wire))

class DNSKEY(RR):
    '''Implements rendering DNSKEY RDATA in the test data format.

    Configurable parameters are as follows (see code below for the
    default values):
    - flags (16-bit int): The flags field.
    - protocol (8-bit int): The protocol field.
    - algorithm (8-bit int): The algorithm field.
    - digest (string): The key digest field.
    '''
    flags = 257
    protocol = 3
    algorithm = 5
    digest = 'AAECAwQFBgcICQoLDA0ODw=='

    def dump(self, f):
        decoded_digest = base64.b64decode(bytes(self.digest, 'ascii'))
        if self.rdlen is None:
            self.rdlen = 4 + len(decoded_digest)
        else:
            self.rdlen = int(self.rdlen)

        self.dump_header(f, self.rdlen)

        f.write('# FLAGS=%d\n' % (self.flags))
        f.write('%04x\n' % (self.flags))

        f.write('# PROTOCOL=%d\n' % (self.protocol))
        f.write('%02x\n' % (self.protocol))

        f.write('# ALGORITHM=%d\n' % (self.algorithm))
        f.write('%02x\n' % (self.algorithm))

        f.write('# DIGEST=%s\n' % (self.digest))
        f.write('%s\n' % (encode_bytes(decoded_digest)))

class NSECBASE(RR):
    '''Implements rendering NSEC/NSEC3 type bitmaps commonly used for
    these RRs.  The NSEC and NSEC3 classes will be inherited from this
    class.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - nbitmap (int): The number of type bitmaps.
    The following three define the bitmaps.  If suffixed with "N"
    (0 <= N < nbitmaps), it means the definition for the N-th bitmap.
    If there is no suffix (e.g., just "block", it means the default
    for any unspecified values)
    - block[N] (8-bit int): The Window Block.
    - maplen[N] (8-bit int): The Bitmap Length.  The default "maplen"
      can also be unspecified (with being set to None), in which case
      the corresponding length will be calculated from the bitmap.
    - bitmap[N] (string): The Bitmap.  This must be the hexadecimal
      representation of the bitmap field.  For example, for a bitmap
      where the 7th and 15th bits (and only these bits) are set, it
      must be '0101'.  Note also that the value must be quated with
      single quatations because it could also be interpreted as an
      integer.
    '''
    nbitmap = 1                 # number of bitmaps
    block = 0
    maplen = None              # default bitmap length, auto-calculate
    bitmap = '040000000003'     # an arbitrarily chosen bitmap sample
    def dump(self, f):
        # first, construct the bitmap data
        block_list = []
        maplen_list = []
        bitmap_list = []
        for i in range(0, self.nbitmap):
            key_bitmap = 'bitmap' + str(i)
            if key_bitmap in self.__dict__:
                bitmap_list.append(self.__dict__[key_bitmap])
            else:
                bitmap_list.append(self.bitmap)
            key_maplen = 'maplen' + str(i)
            if key_maplen in self.__dict__:
                maplen_list.append(self.__dict__[key_maplen])
            else:
                maplen_list.append(self.maplen)
            if maplen_list[-1] is None: # calculate it if not specified
                maplen_list[-1] = int(len(bitmap_list[-1]) / 2)
            key_block = 'block' + str(i)
            if key_block in self.__dict__:
               block_list.append(self.__dict__[key_block])
            else:
                block_list.append(self.block)

        # dump RR-type specific part (NSEC or NSEC3)
        self.dump_fixedpart(f, 2 * self.nbitmap + \
                                int(len(''.join(bitmap_list)) / 2))

        # dump the bitmap
        for i in range(0, self.nbitmap):
            f.write('# Bitmap: Block=%d, Length=%d\n' %
                    (block_list[i], maplen_list[i]))
            f.write('%02x %02x %s\n' %
                    (block_list[i], maplen_list[i], bitmap_list[i]))

class NSEC(NSECBASE):
    '''Implements rendering NSEC RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - Type bitmap related parameters: see class NSECBASE
    - nextname (string): The Next Domain Name field.  The string must be
      interpreted as a valid domain name.
    '''

    nextname = 'next.example.com'
    def dump_fixedpart(self, f, bitmap_totallen):
        name_wire = encode_name(self.nextname)
        if self.rdlen is None:
            # if rdlen needs to be calculated, it must be based on the bitmap
            # length, because the configured maplen can be fake.
            self.rdlen = int(len(name_wire) / 2) + bitmap_totallen
        self.dump_header(f, self.rdlen)
        f.write('# Next Name=%s (%d bytes)\n' % (self.nextname,
                                                 int(len(name_wire) / 2)))
        f.write('%s\n' % name_wire)

class NSEC3PARAM(RR):
    '''Implements rendering NSEC3PARAM RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - hashalg (8-bit int): The Hash Algorithm field.  Note that
      currently the only defined algorithm is SHA-1, for which a value
      of 1 will be used, and it's the default.  So this implementation
      does not support any string representation right now.
    - optout (bool): The Opt-Out flag of the Flags field.
    - mbz (7-bit int): The rest of the Flags field.  This value will
      be left shifted for 1 bit and then OR-ed with optout to
      construct the complete Flags field.
    - iterations (16-bit int): The Iterations field.
    - saltlen (int): The Salt Length field.
    - salt (string): The Salt field.  It is converted to a sequence of
      ascii codes and its hexadecimal representation will be used.
    '''

    hashalg = 1                 # SHA-1
    optout = False              # opt-out flag
    mbz = 0                     # other flag fields (none defined yet)
    iterations = 1
    saltlen = 5
    salt = 's' * saltlen

    def dump(self, f):
        if self.rdlen is None:
            self.rdlen = 4 + 1 + len(self.salt)
        self.dump_header(f, self.rdlen)
        self._dump_params(f)

    def _dump_params(self, f):
        '''This method is intended to be shared with NSEC3 class.

        '''

        optout_val = 1 if self.optout else 0
        f.write('# Hash Alg=%s, Opt-Out=%d, Other Flags=%0x, Iterations=%d\n' %
                (code_totext(self.hashalg, rdict_nsec3_algorithm),
                 optout_val, self.mbz, self.iterations))
        f.write('%02x %02x %04x\n' %
                (self.hashalg, (self.mbz << 1) | optout_val, self.iterations))
        f.write("# Salt Len=%d, Salt='%s'\n" % (self.saltlen, self.salt))
        f.write('%02x%s%s\n' % (self.saltlen,
                                ' ' if len(self.salt) > 0 else '',
                                encode_string(self.salt)))

class NSEC3(NSECBASE, NSEC3PARAM):
    '''Implements rendering NSEC3 RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - Type bitmap related parameters: see class NSECBASE
    - Hash parameter related parameters: see class NSEC3PARAM
    - hashlen (int): The Hash Length field.
    - hash (string): The Next Hashed Owner Name field.  This parameter
      is interpreted as "salt".
    '''

    hashlen = 20
    hash = 'h' * hashlen
    def dump_fixedpart(self, f, bitmap_totallen):
        if self.rdlen is None:
            # if rdlen needs to be calculated, it must be based on the bitmap
            # length, because the configured maplen can be fake.
            self.rdlen = 4 + 1 + len(self.salt) + 1 + len(self.hash) \
                + bitmap_totallen
        self.dump_header(f, self.rdlen)
        self._dump_params(f)
        f.write("# Hash Len=%d, Hash='%s'\n" % (self.hashlen, self.hash))
        f.write('%02x%s%s\n' % (self.hashlen,
                                ' ' if len(self.hash) > 0 else '',
                                encode_string(self.hash)))

class RRSIG(RR):
    '''Implements rendering RRSIG RDATA in the test data format.

    Configurable parameters are as follows (see the description of the
    same name of attribute for the default value):
    - covered (int or string): The Type Covered field.  If specified
      as an integer, it must be the 16-bit RR type value of the
      covered type.  If specifed as a string, it must be the textual
      mnemonic of the type.
    - algorithm (int or string): The Algorithm field.   If specified
      as an integer, it must be the 8-bit algorithm number as defined
      in RFC4034.  If specifed as a string, it must be one of the keys
      of dict_algorithm (case insensitive).
    - labels (int): The Labels field.  If omitted (the corresponding
      variable being set to None), the number of labels of "signer"
      (excluding the trailing null label as specified in RFC4034) will
      be used.
    - originalttl (32-bit int): The Original TTL field.
    - expiration (32-bit int): The Expiration TTL field.
    - inception (32-bit int): The Inception TTL field.
    - tag (16-bit int): The Key Tag field.
    - signer (string): The Signer's Name field.  The string must be
      interpreted as a valid domain name.
    - signature (int): The Signature field.  Right now only a simple
      integer form is supported.  A prefix of "0" will be prepended if
      the resulting hexadecimal representation consists of an odd
      number of characters.
    '''

    covered = 'A'
    algorithm = 'RSASHA1'
    labels = None                 # auto-calculate (#labels of signer)
    originalttl = 3600
    expiration = int(time.mktime(datetime.strptime('20100131120000',
                                                   dnssec_timefmt).timetuple()))
    inception = int(time.mktime(datetime.strptime('20100101120000',
                                                  dnssec_timefmt).timetuple()))
    tag = 0x1035
    signer = 'example.com'
    signature = 0x123456789abcdef123456789abcdef

    def dump(self, f):
        name_wire = encode_name(self.signer)
        sig_wire = '%x' % self.signature
        if len(sig_wire) % 2 != 0:
            sig_wire = '0' + sig_wire
        if self.rdlen is None:
            self.rdlen = int(18 + len(name_wire) / 2 + len(str(sig_wire)) / 2)
        self.dump_header(f, self.rdlen)

        if type(self.covered) is str:
            self.covered = dict_rrtype[self.covered.lower()]
        if type(self.algorithm) is str:
            self.algorithm = dict_algorithm[self.algorithm.lower()]
        if self.labels is None:
            self.labels = count_namelabels(self.signer)
        f.write('# Covered=%s Algorithm=%s Labels=%d OrigTTL=%d\n' %
                (code_totext(self.covered, rdict_rrtype),
                 code_totext(self.algorithm, rdict_algorithm), self.labels,
                 self.originalttl))
        f.write('%04x %02x %02x %08x\n' % (self.covered, self.algorithm,
                                           self.labels, self.originalttl))
        f.write('# Expiration=%s, Inception=%s\n' %
                (str(self.expiration), str(self.inception)))
        f.write('%08x %08x\n' % (self.expiration, self.inception))
        f.write('# Tag=%d Signer=%s and Signature\n' % (self.tag, self.signer))
        f.write('%04x %s %s\n' % (self.tag, name_wire, sig_wire))

class TSIG(RR):
    '''Implements rendering TSIG RDATA in the test data format.

    As a meta RR type TSIG uses some non common parameters.  This
    class overrides some of the default attributes of the RR class
    accordingly:
    - rr_class is set to 'ANY'
    - rr_ttl is set to 0
    Like other derived classes these can be overridden via the spec
    file.

    Other configurable parameters are as follows (see the description
    of the same name of attribute for the default value):
    - algorithm (string): The Algorithm Name field.  The value is
      generally interpreted as a domain name string, and will
      typically be one of the standard algorithm names defined in
      RFC4635.  For convenience, however, a shortcut value "hmac-md5"
      is allowed instead of the standard "hmac-md5.sig-alg.reg.int".
    - time_signed (48-bit int): The Time Signed field.
    - fudge (16-bit int): The Fudge field.
    - mac_size (int): The MAC Size field.  If omitted, the common value
      determined by the algorithm will be used.
    - mac (int or string): The MAC field.  If specified as an integer,
      the integer value is used as the MAC, possibly with prepended
      0's so that the total length will be mac_size.  If specifed as a
      string, it is converted to a sequence of ascii codes and its
      hexadecimal representation will be used.  So, for example, if
      "mac" is set to 'abc', it will be converted to '616263'.  Note
      that in this case the length of "mac" may not be equal to
      mac_size.  If unspecified, the mac_size number of '78' (ascii
      code of 'x') will be used.
    - original_id (16-bit int): The Original ID field.
    - error (16-bit int): The Error field.
    - other_len (int): The Other Len field.
    - other_data (int or string): The Other Data field.  This is
      interpreted just like "mac" except that other_len is used
      instead of mac_size.  If unspecified this will be empty unless
      the "error" is set to 18 (which means the "BADTIME" error), in
      which case a hexadecimal representation of "time_signed + fudge
      + 1" will be used.
    '''

    algorithm = 'hmac-sha256'
    time_signed = 1286978795    # arbitrarily chosen default
    fudge = 300
    mac_size = None             # use a common value for the algorithm
    mac = None                  # use 'x' * mac_size
    original_id = 2845          # arbitrarily chosen default
    error = 0
    other_len = None         # 6 if error is BADTIME; otherwise 0
    other_data = None        # use time_signed + fudge + 1 for BADTIME
    dict_macsize = { 'hmac-md5' : 16, 'hmac-sha1' : 20, 'hmac-sha256' : 32 }

    # TSIG has some special defaults
    def __init__(self):
        super().__init__()
        self.rr_class = 'ANY'
        self.rr_ttl = 0

    def dump(self, f):
        if str(self.algorithm) == 'hmac-md5':
            name_wire = encode_name('hmac-md5.sig-alg.reg.int')
        else:
            name_wire = encode_name(self.algorithm)
        mac_size = self.mac_size
        if mac_size is None:
            if self.algorithm in self.dict_macsize.keys():
                mac_size = self.dict_macsize[self.algorithm]
            else:
                raise RuntimeError('TSIG Mac Size cannot be determined')
        mac = encode_string('x' * mac_size) if self.mac is None else \
            encode_string(self.mac, mac_size)
        other_len = self.other_len
        if other_len is None:
            # 18 = BADTIME
            other_len = 6 if self.error == 18 else 0
        other_data = self.other_data
        if other_data is None:
            other_data = '%012x' % (self.time_signed + self.fudge + 1) \
                if self.error == 18 else ''
        else:
            other_data = encode_string(self.other_data, other_len)
        if self.rdlen is None:
            self.rdlen = int(len(name_wire) / 2 + 16 + len(mac) / 2 + \
                                 len(other_data) / 2)
        self.dump_header(f, self.rdlen)
        f.write('# Algorithm=%s Time-Signed=%d Fudge=%d\n' %
                (self.algorithm, self.time_signed, self.fudge))
        f.write('%s %012x %04x\n' % (name_wire, self.time_signed, self.fudge))
        f.write('# MAC Size=%d MAC=(see hex)\n' % mac_size)
        f.write('%04x%s\n' % (mac_size, ' ' + mac if len(mac) > 0 else ''))
        f.write('# Original-ID=%d Error=%d\n' % (self.original_id, self.error))
        f.write('%04x %04x\n' %  (self.original_id, self.error))
        f.write('# Other-Len=%d Other-Data=(see hex)\n' % other_len)
        f.write('%04x%s\n' % (other_len,
                              ' ' + other_data if len(other_data) > 0 else ''))

# Build section-class mapping
config_param = { 'name' : (Name, {}),
                 'header' : (DNSHeader, header_xtables),
                 'question' : (DNSQuestion, question_xtables),
                 'edns' : (EDNS, {}) }
for rrtype in dict_rrtype.keys():
    # For any supported RR types add the tuple of (RR_CLASS, {}).
    # We expect KeyError as not all the types are supported, and simply
    # ignore them.
    try:
        cur_mod = sys.modules[__name__]
        config_param[rrtype] = (cur_mod.__dict__[rrtype.upper()], {})
    except KeyError:
        pass

def get_config_param(section):
    s = section
    m = re.match('^([^:]+)/\d+$', section)
    if m:
        s = m.group(1)
    return config_param[s]

usage = '''usage: %prog [options] input_file'''

if __name__ == "__main__":
    parser = OptionParser(usage=usage)
    parser.add_option('-o', '--output', action='store', dest='output',
                      default=None, metavar='FILE',
                      help='output file name [default: prefix of input_file]')
    (options, args) = parser.parse_args()

    if len(args) == 0:
        parser.error('input file is missing')
    configfile = args[0]

    outputfile = options.output
    if not outputfile:
        m = re.match('(.*)\.[^.]+$', configfile)
        if m:
            outputfile = m.group(1)
        else:
            raise ValueError('output file is not specified and input file is not in the form of "output_file.suffix"')

    config = configparser.SafeConfigParser()
    config.read(configfile)

    output = open(outputfile, 'w')

    print_header(output, configfile)

    # First try the 'custom' mode; if it fails assume the query mode.
    try:
        sections = config.get('custom', 'sections').split(':')
    except configparser.NoSectionError:
        sections = ['header', 'question', 'edns']

    for s in sections:
        section_param = get_config_param(s)
        (obj, xtables) = (section_param[0](), section_param[1])
        if get_config(config, s, obj, xtables):
            obj.dump(output)

    output.close()