Current File : //usr/lib/python3/dist-packages/dns/node.py
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
# Copyright (C) 2001-2017 Nominum, Inc.
#
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"""DNS nodes. A node is a set of rdatasets."""
import enum
import io
from typing import Any, Dict, Optional
import dns.immutable
import dns.name
import dns.rdataclass
import dns.rdataset
import dns.rdatatype
import dns.renderer
import dns.rrset
_cname_types = {
dns.rdatatype.CNAME,
}
# "neutral" types can coexist with a CNAME and thus are not "other data"
_neutral_types = {
dns.rdatatype.NSEC, # RFC 4035 section 2.5
dns.rdatatype.NSEC3, # This is not likely to happen, but not impossible!
dns.rdatatype.KEY, # RFC 4035 section 2.5, RFC 3007
}
def _matches_type_or_its_signature(rdtypes, rdtype, covers):
return rdtype in rdtypes or (rdtype == dns.rdatatype.RRSIG and covers in rdtypes)
@enum.unique
class NodeKind(enum.Enum):
"""Rdatasets in nodes"""
REGULAR = 0 # a.k.a "other data"
NEUTRAL = 1
CNAME = 2
@classmethod
def classify(
cls, rdtype: dns.rdatatype.RdataType, covers: dns.rdatatype.RdataType
) -> "NodeKind":
if _matches_type_or_its_signature(_cname_types, rdtype, covers):
return NodeKind.CNAME
elif _matches_type_or_its_signature(_neutral_types, rdtype, covers):
return NodeKind.NEUTRAL
else:
return NodeKind.REGULAR
@classmethod
def classify_rdataset(cls, rdataset: dns.rdataset.Rdataset) -> "NodeKind":
return cls.classify(rdataset.rdtype, rdataset.covers)
class Node:
"""A Node is a set of rdatasets.
A node is either a CNAME node or an "other data" node. A CNAME
node contains only CNAME, KEY, NSEC, and NSEC3 rdatasets along with their
covering RRSIG rdatasets. An "other data" node contains any
rdataset other than a CNAME or RRSIG(CNAME) rdataset. When
changes are made to a node, the CNAME or "other data" state is
always consistent with the update, i.e. the most recent change
wins. For example, if you have a node which contains a CNAME
rdataset, and then add an MX rdataset to it, then the CNAME
rdataset will be deleted. Likewise if you have a node containing
an MX rdataset and add a CNAME rdataset, the MX rdataset will be
deleted.
"""
__slots__ = ["rdatasets"]
def __init__(self):
# the set of rdatasets, represented as a list.
self.rdatasets = []
def to_text(self, name: dns.name.Name, **kw: Dict[str, Any]) -> str:
"""Convert a node to text format.
Each rdataset at the node is printed. Any keyword arguments
to this method are passed on to the rdataset's to_text() method.
*name*, a ``dns.name.Name``, the owner name of the
rdatasets.
Returns a ``str``.
"""
s = io.StringIO()
for rds in self.rdatasets:
if len(rds) > 0:
s.write(rds.to_text(name, **kw)) # type: ignore[arg-type]
s.write("\n")
return s.getvalue()[:-1]
def __repr__(self):
return "<DNS node " + str(id(self)) + ">"
def __eq__(self, other):
#
# This is inefficient. Good thing we don't need to do it much.
#
for rd in self.rdatasets:
if rd not in other.rdatasets:
return False
for rd in other.rdatasets:
if rd not in self.rdatasets:
return False
return True
def __ne__(self, other):
return not self.__eq__(other)
def __len__(self):
return len(self.rdatasets)
def __iter__(self):
return iter(self.rdatasets)
def _append_rdataset(self, rdataset):
"""Append rdataset to the node with special handling for CNAME and
other data conditions.
Specifically, if the rdataset being appended has ``NodeKind.CNAME``,
then all rdatasets other than KEY, NSEC, NSEC3, and their covering
RRSIGs are deleted. If the rdataset being appended has
``NodeKind.REGULAR`` then CNAME and RRSIG(CNAME) are deleted.
"""
# Make having just one rdataset at the node fast.
if len(self.rdatasets) > 0:
kind = NodeKind.classify_rdataset(rdataset)
if kind == NodeKind.CNAME:
self.rdatasets = [
rds
for rds in self.rdatasets
if NodeKind.classify_rdataset(rds) != NodeKind.REGULAR
]
elif kind == NodeKind.REGULAR:
self.rdatasets = [
rds
for rds in self.rdatasets
if NodeKind.classify_rdataset(rds) != NodeKind.CNAME
]
# Otherwise the rdataset is NodeKind.NEUTRAL and we do not need to
# edit self.rdatasets.
self.rdatasets.append(rdataset)
def find_rdataset(
self,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
create: bool = False,
) -> dns.rdataset.Rdataset:
"""Find an rdataset matching the specified properties in the
current node.
*rdclass*, a ``dns.rdataclass.RdataClass``, the class of the rdataset.
*rdtype*, a ``dns.rdatatype.RdataType``, the type of the rdataset.
*covers*, a ``dns.rdatatype.RdataType``, 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.
*create*, a ``bool``. If True, create the rdataset if it is not found.
Raises ``KeyError`` if an rdataset of the desired type and class does
not exist and *create* is not ``True``.
Returns a ``dns.rdataset.Rdataset``.
"""
for rds in self.rdatasets:
if rds.match(rdclass, rdtype, covers):
return rds
if not create:
raise KeyError
rds = dns.rdataset.Rdataset(rdclass, rdtype, covers)
self._append_rdataset(rds)
return rds
def get_rdataset(
self,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
create: bool = False,
) -> Optional[dns.rdataset.Rdataset]:
"""Get an rdataset matching the specified properties in the
current node.
None is returned if an rdataset of the specified type and
class does not exist and *create* is not ``True``.
*rdclass*, an ``int``, the class of the rdataset.
*rdtype*, an ``int``, the type of the rdataset.
*covers*, an ``int``, 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.
*create*, a ``bool``. If True, create the rdataset if it is not found.
Returns a ``dns.rdataset.Rdataset`` or ``None``.
"""
try:
rds = self.find_rdataset(rdclass, rdtype, covers, create)
except KeyError:
rds = None
return rds
def delete_rdataset(
self,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
) -> None:
"""Delete the rdataset matching the specified properties in the
current node.
If a matching rdataset does not exist, it is not an error.
*rdclass*, an ``int``, the class of the rdataset.
*rdtype*, an ``int``, the type of the rdataset.
*covers*, an ``int``, the covered type.
"""
rds = self.get_rdataset(rdclass, rdtype, covers)
if rds is not None:
self.rdatasets.remove(rds)
def replace_rdataset(self, replacement: dns.rdataset.Rdataset) -> None:
"""Replace an rdataset.
It is not an error if there is no rdataset matching *replacement*.
Ownership of the *replacement* object is transferred to the node;
in other words, this method does not store a copy of *replacement*
at the node, it stores *replacement* itself.
*replacement*, a ``dns.rdataset.Rdataset``.
Raises ``ValueError`` if *replacement* is not a
``dns.rdataset.Rdataset``.
"""
if not isinstance(replacement, dns.rdataset.Rdataset):
raise ValueError("replacement is not an rdataset")
if isinstance(replacement, dns.rrset.RRset):
# RRsets are not good replacements as the match() method
# is not compatible.
replacement = replacement.to_rdataset()
self.delete_rdataset(
replacement.rdclass, replacement.rdtype, replacement.covers
)
self._append_rdataset(replacement)
def classify(self) -> NodeKind:
"""Classify a node.
A node which contains a CNAME or RRSIG(CNAME) is a
``NodeKind.CNAME`` node.
A node which contains only "neutral" types, i.e. types allowed to
co-exist with a CNAME, is a ``NodeKind.NEUTRAL`` node. The neutral
types are NSEC, NSEC3, KEY, and their associated RRSIGS. An empty node
is also considered neutral.
A node which contains some rdataset which is not a CNAME, RRSIG(CNAME),
or a neutral type is a a ``NodeKind.REGULAR`` node. Regular nodes are
also commonly referred to as "other data".
"""
for rdataset in self.rdatasets:
kind = NodeKind.classify(rdataset.rdtype, rdataset.covers)
if kind != NodeKind.NEUTRAL:
return kind
return NodeKind.NEUTRAL
def is_immutable(self) -> bool:
return False
@dns.immutable.immutable
class ImmutableNode(Node):
def __init__(self, node):
super().__init__()
self.rdatasets = tuple(
[dns.rdataset.ImmutableRdataset(rds) for rds in node.rdatasets]
)
def find_rdataset(
self,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
create: bool = False,
) -> dns.rdataset.Rdataset:
if create:
raise TypeError("immutable")
return super().find_rdataset(rdclass, rdtype, covers, False)
def get_rdataset(
self,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
create: bool = False,
) -> Optional[dns.rdataset.Rdataset]:
if create:
raise TypeError("immutable")
return super().get_rdataset(rdclass, rdtype, covers, False)
def delete_rdataset(
self,
rdclass: dns.rdataclass.RdataClass,
rdtype: dns.rdatatype.RdataType,
covers: dns.rdatatype.RdataType = dns.rdatatype.NONE,
) -> None:
raise TypeError("immutable")
def replace_rdataset(self, replacement: dns.rdataset.Rdataset) -> None:
raise TypeError("immutable")
def is_immutable(self) -> bool:
return True
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