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# Copyright (C) 2001-2007, 2009-2011 Nominum, Inc.
#
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"""DNS rdatasets (an rdataset is a set of rdatas of a given type and class)"""
import random
import StringIO
import struct
import dns.exception
import dns.rdatatype
import dns.rdataclass
import dns.rdata
import dns.set
# define SimpleSet here for backwards compatibility
SimpleSet = dns.set.Set
class DifferingCovers(dns.exception.DNSException):
"""Raised if an attempt is made to add a SIG/RRSIG whose covered type
is not the same as that of the other rdatas in the rdataset."""
pass
class IncompatibleTypes(dns.exception.DNSException):
"""Raised if an attempt is made to add rdata of an incompatible type."""
pass
class Rdataset(dns.set.Set):
"""A DNS rdataset.
@ivar rdclass: The class of the rdataset
@type rdclass: int
@ivar rdtype: The type of the rdataset
@type rdtype: int
@ivar covers: The covered type. Usually this value is
dns.rdatatype.NONE, but if the rdtype is dns.rdatatype.SIG or
dns.rdatatype.RRSIG, then the covers value will be the rdata
type the SIG/RRSIG covers. The library treats the SIG and RRSIG
types as if they were a family of
types, e.g. RRSIG(A), RRSIG(NS), RRSIG(SOA). This makes RRSIGs much
easier to work with than if RRSIGs covering different rdata
types were aggregated into a single RRSIG rdataset.
@type covers: int
@ivar ttl: The DNS TTL (Time To Live) value
@type ttl: int
"""
__slots__ = ['rdclass', 'rdtype', 'covers', 'ttl']
def __init__(self, rdclass, rdtype, covers=dns.rdatatype.NONE):
"""Create a new rdataset of the specified class and type.
@see: the description of the class instance variables for the
meaning of I{rdclass} and I{rdtype}"""
super(Rdataset, self).__init__()
self.rdclass = rdclass
self.rdtype = rdtype
self.covers = covers
self.ttl = 0
def _clone(self):
obj = super(Rdataset, self)._clone()
obj.rdclass = self.rdclass
obj.rdtype = self.rdtype
obj.covers = self.covers
obj.ttl = self.ttl
return obj
def update_ttl(self, ttl):
"""Set the TTL of the rdataset to be the lesser of the set's current
TTL or the specified TTL. If the set contains no rdatas, set the TTL
to the specified TTL.
@param ttl: The TTL
@type ttl: int"""
if len(self) == 0:
self.ttl = ttl
elif ttl < self.ttl:
self.ttl = ttl
def add(self, rd, ttl=None):
"""Add the specified rdata to the rdataset.
If the optional I{ttl} parameter is supplied, then
self.update_ttl(ttl) will be called prior to adding the rdata.
@param rd: The rdata
@type rd: dns.rdata.Rdata object
@param ttl: The TTL
@type ttl: int"""
#
# If we're adding a signature, do some special handling to
# check that the signature covers the same type as the
# other rdatas in this rdataset. If this is the first rdata
# in the set, initialize the covers field.
#
if self.rdclass != rd.rdclass or self.rdtype != rd.rdtype:
raise IncompatibleTypes
if not ttl is None:
self.update_ttl(ttl)
if self.rdtype == dns.rdatatype.RRSIG or \
self.rdtype == dns.rdatatype.SIG:
covers = rd.covers()
if len(self) == 0 and self.covers == dns.rdatatype.NONE:
self.covers = covers
elif self.covers != covers:
raise DifferingCovers
if dns.rdatatype.is_singleton(rd.rdtype) and len(self) > 0:
self.clear()
super(Rdataset, self).add(rd)
def union_update(self, other):
self.update_ttl(other.ttl)
super(Rdataset, self).union_update(other)
def intersection_update(self, other):
self.update_ttl(other.ttl)
super(Rdataset, self).intersection_update(other)
def update(self, other):
"""Add all rdatas in other to self.
@param other: The rdataset from which to update
@type other: dns.rdataset.Rdataset object"""
self.update_ttl(other.ttl)
super(Rdataset, self).update(other)
def __repr__(self):
if self.covers == 0:
ctext = ''
else:
ctext = '(' + dns.rdatatype.to_text(self.covers) + ')'
return '<DNS ' + dns.rdataclass.to_text(self.rdclass) + ' ' + \
dns.rdatatype.to_text(self.rdtype) + ctext + ' rdataset>'
def __str__(self):
return self.to_text()
def __eq__(self, other):
"""Two rdatasets are equal if they have the same class, type, and
covers, and contain the same rdata.
@rtype: bool"""
if not isinstance(other, Rdataset):
return False
if self.rdclass != other.rdclass or \
self.rdtype != other.rdtype or \
self.covers != other.covers:
return False
return super(Rdataset, self).__eq__(other)
def __ne__(self, other):
return not self.__eq__(other)
def to_text(self, name=None, origin=None, relativize=True,
override_rdclass=None, **kw):
"""Convert the rdataset into DNS master file format.
@see: L{dns.name.Name.choose_relativity} for more information
on how I{origin} and I{relativize} determine the way names
are emitted.
Any additional keyword arguments are passed on to the rdata
to_text() method.
@param name: If name is not None, emit a RRs with I{name} as
the owner name.
@type name: dns.name.Name object
@param origin: The origin for relative names, or None.
@type origin: dns.name.Name object
@param relativize: True if names should names be relativized
@type relativize: bool"""
if not name is None:
name = name.choose_relativity(origin, relativize)
ntext = str(name)
pad = ' '
else:
ntext = ''
pad = ''
s = StringIO.StringIO()
if not override_rdclass is None:
rdclass = override_rdclass
else:
rdclass = self.rdclass
if len(self) == 0:
#
# Empty rdatasets are used for the question section, and in
# some dynamic updates, so we don't need to print out the TTL
# (which is meaningless anyway).
#
print >> s, '%s%s%s %s' % (ntext, pad,
dns.rdataclass.to_text(rdclass),
dns.rdatatype.to_text(self.rdtype))
else:
for rd in self:
print >> s, '%s%s%d %s %s %s' % \
(ntext, pad, self.ttl, dns.rdataclass.to_text(rdclass),
dns.rdatatype.to_text(self.rdtype),
rd.to_text(origin=origin, relativize=relativize, **kw))
#
# We strip off the final \n for the caller's convenience in printing
#
return s.getvalue()[:-1]
def to_wire(self, name, file, compress=None, origin=None,
override_rdclass=None, want_shuffle=True):
"""Convert the rdataset to wire format.
@param name: The owner name of the RRset that will be emitted
@type name: dns.name.Name object
@param file: The file to which the wire format data will be appended
@type file: file
@param compress: The compression table to use; the default is None.
@type compress: dict
@param origin: The origin to be appended to any relative names when
they are emitted. The default is None.
@returns: the number of records emitted
@rtype: int
"""
if not override_rdclass is None:
rdclass = override_rdclass
want_shuffle = False
else:
rdclass = self.rdclass
file.seek(0, 2)
if len(self) == 0:
name.to_wire(file, compress, origin)
stuff = struct.pack("!HHIH", self.rdtype, rdclass, 0, 0)
file.write(stuff)
return 1
else:
if want_shuffle:
l = list(self)
random.shuffle(l)
else:
l = self
for rd in l:
name.to_wire(file, compress, origin)
stuff = struct.pack("!HHIH", self.rdtype, rdclass,
self.ttl, 0)
file.write(stuff)
start = file.tell()
rd.to_wire(file, compress, origin)
end = file.tell()
assert end - start < 65536
file.seek(start - 2)
stuff = struct.pack("!H", end - start)
file.write(stuff)
file.seek(0, 2)
return len(self)
def match(self, rdclass, rdtype, covers):
"""Returns True if this rdataset matches the specified class, type,
and covers"""
if self.rdclass == rdclass and \
self.rdtype == rdtype and \
self.covers == covers:
return True
return False
def from_text_list(rdclass, rdtype, ttl, text_rdatas):
"""Create an rdataset with the specified class, type, and TTL, and with
the specified list of rdatas in text format.
@rtype: dns.rdataset.Rdataset object
"""
if isinstance(rdclass, (str, unicode)):
rdclass = dns.rdataclass.from_text(rdclass)
if isinstance(rdtype, (str, unicode)):
rdtype = dns.rdatatype.from_text(rdtype)
r = Rdataset(rdclass, rdtype)
r.update_ttl(ttl)
for t in text_rdatas:
rd = dns.rdata.from_text(r.rdclass, r.rdtype, t)
r.add(rd)
return r
def from_text(rdclass, rdtype, ttl, *text_rdatas):
"""Create an rdataset with the specified class, type, and TTL, and with
the specified rdatas in text format.
@rtype: dns.rdataset.Rdataset object
"""
return from_text_list(rdclass, rdtype, ttl, text_rdatas)
def from_rdata_list(ttl, rdatas):
"""Create an rdataset with the specified TTL, and with
the specified list of rdata objects.
@rtype: dns.rdataset.Rdataset object
"""
if len(rdatas) == 0:
raise ValueError("rdata list must not be empty")
r = None
for rd in rdatas:
if r is None:
r = Rdataset(rd.rdclass, rd.rdtype)
r.update_ttl(ttl)
first_time = False
r.add(rd)
return r
def from_rdata(ttl, *rdatas):
"""Create an rdataset with the specified TTL, and with
the specified rdata objects.
@rtype: dns.rdataset.Rdataset object
"""
return from_rdata_list(ttl, rdatas)