Package dns :: Module rdataset |
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# Source Code for Module dns.rdataset

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     15
     16  """DNS rdatasets (an rdataset is a set of rdatas of a given type and class)"""
     17
     18  import random
     19  import StringIO
     20  import struct
     21
     22  import dns.exception
     23  import dns.rdatatype
     24  import dns.rdataclass
     25  import dns.rdata
     26  import dns.set
     27
     28  # define SimpleSet here for backwards compatibility
     29  SimpleSet = dns.set.Set
     30
     31 -class DifferingCovers(dns.exception.DNSException):
     32      """Raised if an attempt is made to add a SIG/RRSIG whose covered type
     33      is not the same as that of the other rdatas in the rdataset."""
     34      pass
     35
     36 -class IncompatibleTypes(dns.exception.DNSException):
     37      """Raised if an attempt is made to add rdata of an incompatible type."""
     38      pass
     39
     40 -class Rdataset(dns.set.Set):
     41      """A DNS rdataset.
     42
     43      @ivar rdclass: The class of the rdataset
     44      @type rdclass: int
     45      @ivar rdtype: The type of the rdataset
     46      @type rdtype: int
     47      @ivar covers: The covered type.  Usually this value is
     48      dns.rdatatype.NONE, but if the rdtype is dns.rdatatype.SIG or
     49      dns.rdatatype.RRSIG, then the covers value will be the rdata
     50      type the SIG/RRSIG covers.  The library treats the SIG and RRSIG
     51      types as if they were a family of
     52      types, e.g. RRSIG(A), RRSIG(NS), RRSIG(SOA).  This makes RRSIGs much
     53      easier to work with than if RRSIGs covering different rdata
     54      types were aggregated into a single RRSIG rdataset.
     55      @type covers: int
     56      @ivar ttl: The DNS TTL (Time To Live) value
     57      @type ttl: int
     58      """
     59
     60      __slots__ = ['rdclass', 'rdtype', 'covers', 'ttl']
     61
     62 -    def __init__(self, rdclass, rdtype, covers=dns.rdatatype.NONE):
     63          """Create a new rdataset of the specified class and type.
     64
     65          @see: the description of the class instance variables for the
     66          meaning of I{rdclass} and I{rdtype}"""
     67
     68          super(Rdataset, self).__init__()
     69          self.rdclass = rdclass
     70          self.rdtype = rdtype
     71          self.covers = covers
     72          self.ttl = 0
     73
     74 -    def _clone(self):
     75          obj = super(Rdataset, self)._clone()
     76          obj.rdclass = self.rdclass
     77          obj.rdtype = self.rdtype
     78          obj.covers = self.covers
     79          obj.ttl = self.ttl
     80          return obj
     81
     82 -    def update_ttl(self, ttl):
     83          """Set the TTL of the rdataset to be the lesser of the set's current
     84          TTL or the specified TTL.  If the set contains no rdatas, set the TTL
     85          to the specified TTL.
     86          @param ttl: The TTL
     87          @type ttl: int"""
     88
     89          if len(self) == 0:
     90              self.ttl = ttl
     91          elif ttl < self.ttl:
     92              self.ttl = ttl
     93
     94 -    def add(self, rd, ttl=None):
     95          """Add the specified rdata to the rdataset.
     96
     97          If the optional I{ttl} parameter is supplied, then
     98          self.update_ttl(ttl) will be called prior to adding the rdata.
     99
    100          @param rd: The rdata
    101          @type rd: dns.rdata.Rdata object
    102          @param ttl: The TTL
    103          @type ttl: int"""
    104
    105          #
    106          # If we're adding a signature, do some special handling to
    107          # check that the signature covers the same type as the
    108          # other rdatas in this rdataset.  If this is the first rdata
    109          # in the set, initialize the covers field.
    110          #
    111          if self.rdclass != rd.rdclass or self.rdtype != rd.rdtype:
    112              raise IncompatibleTypes
    113          if not ttl is None:
    114              self.update_ttl(ttl)
    115          if self.rdtype == dns.rdatatype.RRSIG or \
    116             self.rdtype == dns.rdatatype.SIG:
    117              covers = rd.covers()
    118              if len(self) == 0 and self.covers == dns.rdatatype.NONE:
    119                  self.covers = covers
    120              elif self.covers != covers:
    121                  raise DifferingCovers
    122          if dns.rdatatype.is_singleton(rd.rdtype) and len(self) > 0:
    123              self.clear()
    124          super(Rdataset, self).add(rd)
    125
    126 -    def union_update(self, other):
    127          self.update_ttl(other.ttl)
    128          super(Rdataset, self).union_update(other)
    129
    130 -    def intersection_update(self, other):
    131          self.update_ttl(other.ttl)
    132          super(Rdataset, self).intersection_update(other)
    133
    134 -    def update(self, other):
    135          """Add all rdatas in other to self.
    136
    137          @param other: The rdataset from which to update
    138          @type other: dns.rdataset.Rdataset object"""
    139
    140          self.update_ttl(other.ttl)
    141          super(Rdataset, self).update(other)
    142
    143 -    def __repr__(self):
    144          if self.covers == 0:
    145              ctext = ''
    146          else:
    147              ctext = '(' + dns.rdatatype.to_text(self.covers) + ')'
    148          return '<DNS ' + dns.rdataclass.to_text(self.rdclass) + ' ' + \
    149                 dns.rdatatype.to_text(self.rdtype) + ctext + ' rdataset>'
    150
    151 -    def __str__(self):
    152          return self.to_text()
    153
    154 -    def __eq__(self, other):
    155          """Two rdatasets are equal if they have the same class, type, and
    156          covers, and contain the same rdata.
    157          @rtype: bool"""
    158
    159          if not isinstance(other, Rdataset):
    160              return False
    161          if self.rdclass != other.rdclass or \
    162             self.rdtype != other.rdtype or \
    163             self.covers != other.covers:
    164              return False
    165          return super(Rdataset, self).__eq__(other)
    166
    167 -    def __ne__(self, other):
    168          return not self.__eq__(other)
    169
    170 -    def to_text(self, name=None, origin=None, relativize=True,
    171                  override_rdclass=None, **kw):
    172          """Convert the rdataset into DNS master file format.
    173
    174          @see: L{dns.name.Name.choose_relativity} for more information
    175          on how I{origin} and I{relativize} determine the way names
    176          are emitted.
    177
    178          Any additional keyword arguments are passed on to the rdata
    179          to_text() method.
    180
    181          @param name: If name is not None, emit a RRs with I{name} as
    182          the owner name.
    183          @type name: dns.name.Name object
    184          @param origin: The origin for relative names, or None.
    185          @type origin: dns.name.Name object
    186          @param relativize: True if names should names be relativized
    187          @type relativize: bool"""
    188          if not name is None:
    189              name = name.choose_relativity(origin, relativize)
    190              ntext = str(name)
    191              pad = ' '
    192          else:
    193              ntext = ''
    194              pad = ''
    195          s = StringIO.StringIO()
    196          if not override_rdclass is None:
    197              rdclass = override_rdclass
    198          else:
    199              rdclass = self.rdclass
    200          if len(self) == 0:
    201              #
    202              # Empty rdatasets are used for the question section, and in
    203              # some dynamic updates, so we don't need to print out the TTL
    204              # (which is meaningless anyway).
    205              #
    206              print >> s, '%s%s%s %s' % (ntext, pad,
    207                                         dns.rdataclass.to_text(rdclass),
    208                                         dns.rdatatype.to_text(self.rdtype))
    209          else:
    210              for rd in self:
    211                  print >> s, '%s%s%d %s %s %s' % \
    212                        (ntext, pad, self.ttl, dns.rdataclass.to_text(rdclass),
    213                         dns.rdatatype.to_text(self.rdtype),
    214                         rd.to_text(origin=origin, relativize=relativize, **kw))
    215          #
    216          # We strip off the final \n for the caller's convenience in printing
    217          #
    218          return s.getvalue()[:-1]
    219
    220 -    def to_wire(self, name, file, compress=None, origin=None,
    221                  override_rdclass=None, want_shuffle=True):
    222          """Convert the rdataset to wire format.
    223
    224          @param name: The owner name of the RRset that will be emitted
    225          @type name: dns.name.Name object
    226          @param file: The file to which the wire format data will be appended
    227          @type file: file
    228          @param compress: The compression table to use; the default is None.
    229          @type compress: dict
    230          @param origin: The origin to be appended to any relative names when
    231          they are emitted.  The default is None.
    232          @returns: the number of records emitted
    233          @rtype: int
    234          """
    235
    236          if not override_rdclass is None:
    237              rdclass =  override_rdclass
    238              want_shuffle = False
    239          else:
    240              rdclass = self.rdclass
    241          file.seek(0, 2)
    242          if len(self) == 0:
    243              name.to_wire(file, compress, origin)
    244              stuff = struct.pack("!HHIH", self.rdtype, rdclass, 0, 0)
    245              file.write(stuff)
    246              return 1
    247          else:
    248              if want_shuffle:
    249                  l = list(self)
    250                  random.shuffle(l)
    251              else:
    252                  l = self
    253              for rd in l:
    254                  name.to_wire(file, compress, origin)
    255                  stuff = struct.pack("!HHIH", self.rdtype, rdclass,
    256                                      self.ttl, 0)
    257                  file.write(stuff)
    258                  start = file.tell()
    259                  rd.to_wire(file, compress, origin)
    260                  end = file.tell()
    261                  assert end - start < 65536
    262                  file.seek(start - 2)
    263                  stuff = struct.pack("!H", end - start)
    264                  file.write(stuff)
    265                  file.seek(0, 2)
    266              return len(self)
    267
    268 -    def match(self, rdclass, rdtype, covers):
    269          """Returns True if this rdataset matches the specified class, type,
    270          and covers"""
    271          if self.rdclass == rdclass and \
    272             self.rdtype == rdtype and \
    273             self.covers == covers:
    274              return True
    275          return False
    276
    277 -def from_text_list(rdclass, rdtype, ttl, text_rdatas):
    278      """Create an rdataset with the specified class, type, and TTL, and with
    279      the specified list of rdatas in text format.
    280
    281      @rtype: dns.rdataset.Rdataset object
    282      """
    283
    284      if isinstance(rdclass, (str, unicode)):
    285          rdclass = dns.rdataclass.from_text(rdclass)
    286      if isinstance(rdtype, (str, unicode)):
    287          rdtype = dns.rdatatype.from_text(rdtype)
    288      r = Rdataset(rdclass, rdtype)
    289      r.update_ttl(ttl)
    290      for t in text_rdatas:
    291          rd = dns.rdata.from_text(r.rdclass, r.rdtype, t)
    292          r.add(rd)
    293      return r
    294
    295 -def from_text(rdclass, rdtype, ttl, *text_rdatas):
    296      """Create an rdataset with the specified class, type, and TTL, and with
    297      the specified rdatas in text format.
    298
    299      @rtype: dns.rdataset.Rdataset object
    300      """
    301
    302      return from_text_list(rdclass, rdtype, ttl, text_rdatas)
    303
    304 -def from_rdata_list(ttl, rdatas):
    305      """Create an rdataset with the specified TTL, and with
    306      the specified list of rdata objects.
    307
    308      @rtype: dns.rdataset.Rdataset object
    309      """
    310
    311      if len(rdatas) == 0:
    312          raise ValueError("rdata list must not be empty")
    313      r = None
    314      for rd in rdatas:
    315          if r is None:
    316              r = Rdataset(rd.rdclass, rd.rdtype)
    317              r.update_ttl(ttl)
    318              first_time = False
    319          r.add(rd)
    320      return r
    321
    322 -def from_rdata(ttl, *rdatas):
    323      """Create an rdataset with the specified TTL, and with
    324      the specified rdata objects.
    325
    326      @rtype: dns.rdataset.Rdataset object
    327      """
    328
    329      return from_rdata_list(ttl, rdatas)
    330