1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
|
# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
import collections
import dns.exception
import dns.name
import dns.rdataclass
import dns.rdataset
import dns.rdatatype
import dns.rrset
import dns.serial
import dns.ttl
class TransactionManager:
def reader(self):
"""Begin a read-only transaction."""
raise NotImplementedError # pragma: no cover
def writer(self, replacement=False):
"""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):
"""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):
"""The class of the transaction manager.
"""
raise NotImplementedError # pragma: no cover
def from_wire_origin(self):
"""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)
class Transaction:
def __init__(self, manager, replacement=False, read_only=False):
self.manager = manager
self.replacement = replacement
self.read_only = read_only
self._ended = False
self._check_put_rdataset = []
self._check_delete_rdataset = []
self._check_delete_name = []
#
# This is the high level API
#
def get(self, name, rdtype, covers=dns.rdatatype.NONE):
"""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)
rdataset = self._get_rdataset(name, rdtype, covers)
return _ensure_immutable_rdataset(rdataset)
def get_node(self, name):
"""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):
if self.read_only:
raise ReadOnly
def add(self, *args):
"""Add records.
The arguments may be:
- rrset
- name, rdataset...
- name, ttl, rdata...
"""
self._check_ended()
self._check_read_only()
return self._add(False, args)
def replace(self, *args):
"""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()
return self._add(True, args)
def delete(self, *args):
"""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, rdataclass, rdatatype, [covers]
- name, rdataset...
- name, rdata...
"""
self._check_ended()
self._check_read_only()
return self._delete(False, args)
def delete_exact(self, *args):
"""Delete records.
The arguments may be:
- rrset
- name
- name, rdataclass, 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()
return self._delete(True, args)
def name_exists(self, name):
"""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=1, relative=True, name=dns.name.empty):
"""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):
"""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):
"""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):
"""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):
"""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):
"""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):
"""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)
#
# 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._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()
if self._ended:
raise AlreadyEnded
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 _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()
|