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transaction.py
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# 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 class TransactionManager: def reader(self) -> "Transaction": """Begin a read-only transaction.""" raise NotImplementedError # pragma: no cover 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 def origin_information( self, ) -> Tuple[Optional[dns.name.Name], bool, Optional[dns.name.Name]]: """Returns a tuple (absolute_origin, relativize, effective_origin) giving the absolute name of the default origin for any relative domain names, the "effective origin", and whether names should be relativized. The "effective origin" is the absolute origin if relativize is False, and the empty name if relativize is true. (The effective origin is provided even though it can be computed from the absolute_origin and relativize setting because it avoids a lot of code duplication.) If the returned names are `None`, then no origin information is available. This information is used by code working with transactions to allow it to coordinate relativization. The transaction code itself takes what it gets (i.e. does not change name relativity). """ raise NotImplementedError # pragma: no cover def get_class(self) -> dns.rdataclass.RdataClass: """The class of the transaction manager.""" raise NotImplementedError # pragma: no cover 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] 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. 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) 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 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) 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) 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) 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) 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) 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() 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() 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) 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) 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) 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) 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) 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() 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()