# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
import collections
from typing import Any, Callable, Iterator, List, Optional, Tuple, Union
import dns.exception
import dns.name
import dns.node
import dns.rdataclass
import dns.rdataset
import dns.rdatatype
import dns.rrset
import dns.serial
import dns.ttl
[docs]
class TransactionManager:
[docs]
def reader(self) -> "Transaction":
"""Begin a read-only transaction."""
raise NotImplementedError # pragma: no cover
[docs]
def writer(self, replacement: bool = False) -> "Transaction":
"""Begin a writable transaction.
*replacement*, a ``bool``. If `True`, the content of the
transaction completely replaces any prior content. If False,
the default, then the content of the transaction updates the
existing content.
"""
raise NotImplementedError # pragma: no cover
[docs]
def get_class(self) -> dns.rdataclass.RdataClass:
"""The class of the transaction manager."""
raise NotImplementedError # pragma: no cover
[docs]
def from_wire_origin(self) -> Optional[dns.name.Name]:
"""Origin to use in from_wire() calls."""
(absolute_origin, relativize, _) = self.origin_information()
if relativize:
return absolute_origin
else:
return None
class DeleteNotExact(dns.exception.DNSException):
"""Existing data did not match data specified by an exact delete."""
class ReadOnly(dns.exception.DNSException):
"""Tried to write to a read-only transaction."""
class AlreadyEnded(dns.exception.DNSException):
"""Tried to use an already-ended transaction."""
def _ensure_immutable_rdataset(rdataset):
if rdataset is None or isinstance(rdataset, dns.rdataset.ImmutableRdataset):
return rdataset
return dns.rdataset.ImmutableRdataset(rdataset)
def _ensure_immutable_node(node):
if node is None or node.is_immutable():
return node
return dns.node.ImmutableNode(node)
CheckPutRdatasetType = Callable[
["Transaction", dns.name.Name, dns.rdataset.Rdataset], None
]
CheckDeleteRdatasetType = Callable[
["Transaction", dns.name.Name, dns.rdatatype.RdataType, dns.rdatatype.RdataType],
None,
]
CheckDeleteNameType = Callable[["Transaction", dns.name.Name], None]
[docs]
class Transaction:
def __init__(
self,
manager: TransactionManager,
replacement: bool = False,
read_only: bool = False,
):
self.manager = manager
self.replacement = replacement
self.read_only = read_only
self._ended = False
self._check_put_rdataset: List[CheckPutRdatasetType] = []
self._check_delete_rdataset: List[CheckDeleteRdatasetType] = []
self._check_delete_name: List[CheckDeleteNameType] = []
#
# This is the high level API
#
# Note that we currently use non-immutable types in the return type signature to
# avoid covariance problems, e.g. if the caller has a List[Rdataset], mypy will be
# unhappy if we return an ImmutableRdataset.
[docs]
def get(
self,
name: Optional[Union[dns.name.Name, str]],
rdtype: Union[dns.rdatatype.RdataType, str],
covers: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.NONE,
) -> dns.rdataset.Rdataset:
"""Return the rdataset associated with *name*, *rdtype*, and *covers*,
or `None` if not found.
Note that the returned rdataset is immutable.
"""
self._check_ended()
if isinstance(name, str):
name = dns.name.from_text(name, None)
rdtype = dns.rdatatype.RdataType.make(rdtype)
covers = dns.rdatatype.RdataType.make(covers)
rdataset = self._get_rdataset(name, rdtype, covers)
return _ensure_immutable_rdataset(rdataset)
[docs]
def get_node(self, name: dns.name.Name) -> Optional[dns.node.Node]:
"""Return the node at *name*, if any.
Returns an immutable node or ``None``.
"""
return _ensure_immutable_node(self._get_node(name))
def _check_read_only(self) -> None:
if self.read_only:
raise ReadOnly
[docs]
def add(self, *args: Any) -> None:
"""Add records.
The arguments may be:
- rrset
- name, rdataset...
- name, ttl, rdata...
"""
self._check_ended()
self._check_read_only()
self._add(False, args)
[docs]
def replace(self, *args: Any) -> None:
"""Replace the existing rdataset at the name with the specified
rdataset, or add the specified rdataset if there was no existing
rdataset.
The arguments may be:
- rrset
- name, rdataset...
- name, ttl, rdata...
Note that if you want to replace the entire node, you should do
a delete of the name followed by one or more calls to add() or
replace().
"""
self._check_ended()
self._check_read_only()
self._add(True, args)
[docs]
def delete(self, *args: Any) -> None:
"""Delete records.
It is not an error if some of the records are not in the existing
set.
The arguments may be:
- rrset
- name
- name, rdatatype, [covers]
- name, rdataset...
- name, rdata...
"""
self._check_ended()
self._check_read_only()
self._delete(False, args)
[docs]
def delete_exact(self, *args: Any) -> None:
"""Delete records.
The arguments may be:
- rrset
- name
- name, rdatatype, [covers]
- name, rdataset...
- name, rdata...
Raises dns.transaction.DeleteNotExact if some of the records
are not in the existing set.
"""
self._check_ended()
self._check_read_only()
self._delete(True, args)
[docs]
def name_exists(self, name: Union[dns.name.Name, str]) -> bool:
"""Does the specified name exist?"""
self._check_ended()
if isinstance(name, str):
name = dns.name.from_text(name, None)
return self._name_exists(name)
[docs]
def update_serial(
self,
value: int = 1,
relative: bool = True,
name: dns.name.Name = dns.name.empty,
) -> None:
"""Update the serial number.
*value*, an `int`, is an increment if *relative* is `True`, or the
actual value to set if *relative* is `False`.
Raises `KeyError` if there is no SOA rdataset at *name*.
Raises `ValueError` if *value* is negative or if the increment is
so large that it would cause the new serial to be less than the
prior value.
"""
self._check_ended()
if value < 0:
raise ValueError("negative update_serial() value")
if isinstance(name, str):
name = dns.name.from_text(name, None)
rdataset = self._get_rdataset(name, dns.rdatatype.SOA, dns.rdatatype.NONE)
if rdataset is None or len(rdataset) == 0:
raise KeyError
if relative:
serial = dns.serial.Serial(rdataset[0].serial) + value
else:
serial = dns.serial.Serial(value)
serial = serial.value # convert back to int
if serial == 0:
serial = 1
rdata = rdataset[0].replace(serial=serial)
new_rdataset = dns.rdataset.from_rdata(rdataset.ttl, rdata)
self.replace(name, new_rdataset)
def __iter__(self):
self._check_ended()
return self._iterate_rdatasets()
[docs]
def changed(self) -> bool:
"""Has this transaction changed anything?
For read-only transactions, the result is always `False`.
For writable transactions, the result is `True` if at some time
during the life of the transaction, the content was changed.
"""
self._check_ended()
return self._changed()
[docs]
def commit(self) -> None:
"""Commit the transaction.
Normally transactions are used as context managers and commit
or rollback automatically, but it may be done explicitly if needed.
A ``dns.transaction.Ended`` exception will be raised if you try
to use a transaction after it has been committed or rolled back.
Raises an exception if the commit fails (in which case the transaction
is also rolled back.
"""
self._end(True)
[docs]
def rollback(self) -> None:
"""Rollback the transaction.
Normally transactions are used as context managers and commit
or rollback automatically, but it may be done explicitly if needed.
A ``dns.transaction.AlreadyEnded`` exception will be raised if you try
to use a transaction after it has been committed or rolled back.
Rollback cannot otherwise fail.
"""
self._end(False)
[docs]
def check_put_rdataset(self, check: CheckPutRdatasetType) -> None:
"""Call *check* before putting (storing) an rdataset.
The function is called with the transaction, the name, and the rdataset.
The check function may safely make non-mutating transaction method
calls, but behavior is undefined if mutating transaction methods are
called. The check function should raise an exception if it objects to
the put, and otherwise should return ``None``.
"""
self._check_put_rdataset.append(check)
[docs]
def check_delete_rdataset(self, check: CheckDeleteRdatasetType) -> None:
"""Call *check* before deleting an rdataset.
The function is called with the transaction, the name, the rdatatype,
and the covered rdatatype.
The check function may safely make non-mutating transaction method
calls, but behavior is undefined if mutating transaction methods are
called. The check function should raise an exception if it objects to
the put, and otherwise should return ``None``.
"""
self._check_delete_rdataset.append(check)
[docs]
def check_delete_name(self, check: CheckDeleteNameType) -> None:
"""Call *check* before putting (storing) an rdataset.
The function is called with the transaction and the name.
The check function may safely make non-mutating transaction method
calls, but behavior is undefined if mutating transaction methods are
called. The check function should raise an exception if it objects to
the put, and otherwise should return ``None``.
"""
self._check_delete_name.append(check)
[docs]
def iterate_rdatasets(
self,
) -> Iterator[Tuple[dns.name.Name, dns.rdataset.Rdataset]]:
"""Iterate all the rdatasets in the transaction, returning
(`dns.name.Name`, `dns.rdataset.Rdataset`) tuples.
Note that as is usual with python iterators, adding or removing items
while iterating will invalidate the iterator and may raise `RuntimeError`
or fail to iterate over all entries."""
self._check_ended()
return self._iterate_rdatasets()
[docs]
def iterate_names(self) -> Iterator[dns.name.Name]:
"""Iterate all the names in the transaction.
Note that as is usual with python iterators, adding or removing names
while iterating will invalidate the iterator and may raise `RuntimeError`
or fail to iterate over all entries."""
self._check_ended()
return self._iterate_names()
#
# Helper methods
#
def _raise_if_not_empty(self, method, args):
if len(args) != 0:
raise TypeError(f"extra parameters to {method}")
def _rdataset_from_args(self, method, deleting, args):
try:
arg = args.popleft()
if isinstance(arg, dns.rrset.RRset):
rdataset = arg.to_rdataset()
elif isinstance(arg, dns.rdataset.Rdataset):
rdataset = arg
else:
if deleting:
ttl = 0
else:
if isinstance(arg, int):
ttl = arg
if ttl > dns.ttl.MAX_TTL:
raise ValueError(f"{method}: TTL value too big")
else:
raise TypeError(f"{method}: expected a TTL")
arg = args.popleft()
if isinstance(arg, dns.rdata.Rdata):
rdataset = dns.rdataset.from_rdata(ttl, arg)
else:
raise TypeError(f"{method}: expected an Rdata")
return rdataset
except IndexError:
if deleting:
return None
else:
# reraise
raise TypeError(f"{method}: expected more arguments")
def _add(self, replace, args):
try:
args = collections.deque(args)
if replace:
method = "replace()"
else:
method = "add()"
arg = args.popleft()
if isinstance(arg, str):
arg = dns.name.from_text(arg, None)
if isinstance(arg, dns.name.Name):
name = arg
rdataset = self._rdataset_from_args(method, False, args)
elif isinstance(arg, dns.rrset.RRset):
rrset = arg
name = rrset.name
# rrsets are also rdatasets, but they don't print the
# same and can't be stored in nodes, so convert.
rdataset = rrset.to_rdataset()
else:
raise TypeError(
f"{method} requires a name or RRset as the first argument"
)
if rdataset.rdclass != self.manager.get_class():
raise ValueError(f"{method} has objects of wrong RdataClass")
if rdataset.rdtype == dns.rdatatype.SOA:
(_, _, origin) = self._origin_information()
if name != origin:
raise ValueError(f"{method} has non-origin SOA")
self._raise_if_not_empty(method, args)
if not replace:
existing = self._get_rdataset(name, rdataset.rdtype, rdataset.covers)
if existing is not None:
if isinstance(existing, dns.rdataset.ImmutableRdataset):
trds = dns.rdataset.Rdataset(
existing.rdclass, existing.rdtype, existing.covers
)
trds.update(existing)
existing = trds
rdataset = existing.union(rdataset)
self._checked_put_rdataset(name, rdataset)
except IndexError:
raise TypeError(f"not enough parameters to {method}")
def _delete(self, exact, args):
try:
args = collections.deque(args)
if exact:
method = "delete_exact()"
else:
method = "delete()"
arg = args.popleft()
if isinstance(arg, str):
arg = dns.name.from_text(arg, None)
if isinstance(arg, dns.name.Name):
name = arg
if len(args) > 0 and (
isinstance(args[0], int) or isinstance(args[0], str)
):
# deleting by type and (optionally) covers
rdtype = dns.rdatatype.RdataType.make(args.popleft())
if len(args) > 0:
covers = dns.rdatatype.RdataType.make(args.popleft())
else:
covers = dns.rdatatype.NONE
self._raise_if_not_empty(method, args)
existing = self._get_rdataset(name, rdtype, covers)
if existing is None:
if exact:
raise DeleteNotExact(f"{method}: missing rdataset")
else:
self._checked_delete_rdataset(name, rdtype, covers)
return
else:
rdataset = self._rdataset_from_args(method, True, args)
elif isinstance(arg, dns.rrset.RRset):
rdataset = arg # rrsets are also rdatasets
name = rdataset.name
else:
raise TypeError(
f"{method} requires a name or RRset as the first argument"
)
self._raise_if_not_empty(method, args)
if rdataset:
if rdataset.rdclass != self.manager.get_class():
raise ValueError(f"{method} has objects of wrong RdataClass")
existing = self._get_rdataset(name, rdataset.rdtype, rdataset.covers)
if existing is not None:
if exact:
intersection = existing.intersection(rdataset)
if intersection != rdataset:
raise DeleteNotExact(f"{method}: missing rdatas")
rdataset = existing.difference(rdataset)
if len(rdataset) == 0:
self._checked_delete_rdataset(
name, rdataset.rdtype, rdataset.covers
)
else:
self._checked_put_rdataset(name, rdataset)
elif exact:
raise DeleteNotExact(f"{method}: missing rdataset")
else:
if exact and not self._name_exists(name):
raise DeleteNotExact(f"{method}: name not known")
self._checked_delete_name(name)
except IndexError:
raise TypeError(f"not enough parameters to {method}")
def _check_ended(self):
if self._ended:
raise AlreadyEnded
def _end(self, commit):
self._check_ended()
try:
self._end_transaction(commit)
finally:
self._ended = True
def _checked_put_rdataset(self, name, rdataset):
for check in self._check_put_rdataset:
check(self, name, rdataset)
self._put_rdataset(name, rdataset)
def _checked_delete_rdataset(self, name, rdtype, covers):
for check in self._check_delete_rdataset:
check(self, name, rdtype, covers)
self._delete_rdataset(name, rdtype, covers)
def _checked_delete_name(self, name):
for check in self._check_delete_name:
check(self, name)
self._delete_name(name)
#
# Transactions are context managers.
#
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
if not self._ended:
if exc_type is None:
self.commit()
else:
self.rollback()
return False
#
# This is the low level API, which must be implemented by subclasses
# of Transaction.
#
def _get_rdataset(self, name, rdtype, covers):
"""Return the rdataset associated with *name*, *rdtype*, and *covers*,
or `None` if not found.
"""
raise NotImplementedError # pragma: no cover
def _put_rdataset(self, name, rdataset):
"""Store the rdataset."""
raise NotImplementedError # pragma: no cover
def _delete_name(self, name):
"""Delete all data associated with *name*.
It is not an error if the name does not exist.
"""
raise NotImplementedError # pragma: no cover
def _delete_rdataset(self, name, rdtype, covers):
"""Delete all data associated with *name*, *rdtype*, and *covers*.
It is not an error if the rdataset does not exist.
"""
raise NotImplementedError # pragma: no cover
def _name_exists(self, name):
"""Does name exist?
Returns a bool.
"""
raise NotImplementedError # pragma: no cover
def _changed(self):
"""Has this transaction changed anything?"""
raise NotImplementedError # pragma: no cover
def _end_transaction(self, commit):
"""End the transaction.
*commit*, a bool. If ``True``, commit the transaction, otherwise
roll it back.
If committing and the commit fails, then roll back and raise an
exception.
"""
raise NotImplementedError # pragma: no cover
def _set_origin(self, origin):
"""Set the origin.
This method is called when reading a possibly relativized
source, and an origin setting operation occurs (e.g. $ORIGIN
in a zone file).
"""
raise NotImplementedError # pragma: no cover
def _iterate_rdatasets(self):
"""Return an iterator that yields (name, rdataset) tuples."""
raise NotImplementedError # pragma: no cover
def _iterate_names(self):
"""Return an iterator that yields a name."""
raise NotImplementedError # pragma: no cover
def _get_node(self, name):
"""Return the node at *name*, if any.
Returns a node or ``None``.
"""
raise NotImplementedError # pragma: no cover
#
# Low-level API with a default implementation, in case a subclass needs
# to override.
#
def _origin_information(self):
# This is only used by _add()
return self.manager.origin_information()