summary refs log tree commit diff
path: root/synapse/federation/federation_server.py
blob: 341965047a338846f1ec2ed517b5b82ca706d9f4 (plain) (blame)
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
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
# Copyright 2015, 2016 OpenMarket Ltd
# Copyright 2018 New Vector Ltd
# Copyright 2019 Matrix.org Federation C.I.C
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
import random
from typing import (
    TYPE_CHECKING,
    Any,
    Awaitable,
    Callable,
    Dict,
    Iterable,
    List,
    Optional,
    Tuple,
    Union,
)

from prometheus_client import Counter, Gauge, Histogram

from twisted.internet import defer
from twisted.internet.abstract import isIPAddress
from twisted.python import failure

from synapse.api.constants import EduTypes, EventTypes, Membership
from synapse.api.errors import (
    AuthError,
    Codes,
    FederationError,
    IncompatibleRoomVersionError,
    NotFoundError,
    SynapseError,
    UnsupportedRoomVersionError,
)
from synapse.api.room_versions import KNOWN_ROOM_VERSIONS
from synapse.events import EventBase
from synapse.events.snapshot import EventContext
from synapse.federation.federation_base import FederationBase, event_from_pdu_json
from synapse.federation.persistence import TransactionActions
from synapse.federation.units import Edu, Transaction
from synapse.http.servlet import assert_params_in_dict
from synapse.logging.context import (
    make_deferred_yieldable,
    nested_logging_context,
    run_in_background,
)
from synapse.logging.opentracing import log_kv, start_active_span_from_edu, trace
from synapse.logging.utils import log_function
from synapse.replication.http.federation import (
    ReplicationFederationSendEduRestServlet,
    ReplicationGetQueryRestServlet,
)
from synapse.types import JsonDict
from synapse.util import glob_to_regex, json_decoder, unwrapFirstError
from synapse.util.async_helpers import Linearizer, concurrently_execute
from synapse.util.caches.response_cache import ResponseCache
from synapse.util.stringutils import parse_server_name

if TYPE_CHECKING:
    from synapse.server import HomeServer

# when processing incoming transactions, we try to handle multiple rooms in
# parallel, up to this limit.
TRANSACTION_CONCURRENCY_LIMIT = 10

logger = logging.getLogger(__name__)

received_pdus_counter = Counter("synapse_federation_server_received_pdus", "")

received_edus_counter = Counter("synapse_federation_server_received_edus", "")

received_queries_counter = Counter(
    "synapse_federation_server_received_queries", "", ["type"]
)

pdu_process_time = Histogram(
    "synapse_federation_server_pdu_process_time",
    "Time taken to process an event",
)

last_pdu_ts_metric = Gauge(
    "synapse_federation_last_received_pdu_time",
    "The timestamp of the last PDU which was successfully received from the given domain",
    labelnames=("server_name",),
)


class FederationServer(FederationBase):
    def __init__(self, hs: "HomeServer"):
        super().__init__(hs)

        self.auth = hs.get_auth()
        self.handler = hs.get_federation_handler()
        self.state = hs.get_state_handler()

        self.device_handler = hs.get_device_handler()

        # Ensure the following handlers are loaded since they register callbacks
        # with FederationHandlerRegistry.
        hs.get_directory_handler()

        self._server_linearizer = Linearizer("fed_server")

        # origins that we are currently processing a transaction from.
        # a dict from origin to txn id.
        self._active_transactions = {}  # type: Dict[str, str]

        # We cache results for transaction with the same ID
        self._transaction_resp_cache = ResponseCache(
            hs.get_clock(), "fed_txn_handler", timeout_ms=30000
        )  # type: ResponseCache[Tuple[str, str]]

        self.transaction_actions = TransactionActions(self.store)

        self.registry = hs.get_federation_registry()

        # We cache responses to state queries, as they take a while and often
        # come in waves.
        self._state_resp_cache = ResponseCache(
            hs.get_clock(), "state_resp", timeout_ms=30000
        )  # type: ResponseCache[Tuple[str, Optional[str]]]
        self._state_ids_resp_cache = ResponseCache(
            hs.get_clock(), "state_ids_resp", timeout_ms=30000
        )  # type: ResponseCache[Tuple[str, str]]

        self._federation_metrics_domains = (
            hs.config.federation.federation_metrics_domains
        )

        self._room_prejoin_state_types = hs.config.api.room_prejoin_state

    async def on_backfill_request(
        self, origin: str, room_id: str, versions: List[str], limit: int
    ) -> Tuple[int, Dict[str, Any]]:
        with (await self._server_linearizer.queue((origin, room_id))):
            origin_host, _ = parse_server_name(origin)
            await self.check_server_matches_acl(origin_host, room_id)

            pdus = await self.handler.on_backfill_request(
                origin, room_id, versions, limit
            )

            res = self._transaction_from_pdus(pdus).get_dict()

        return 200, res

    async def on_incoming_transaction(
        self, origin: str, transaction_data: JsonDict
    ) -> Tuple[int, Dict[str, Any]]:
        # keep this as early as possible to make the calculated origin ts as
        # accurate as possible.
        request_time = self._clock.time_msec()

        transaction = Transaction(**transaction_data)
        transaction_id = transaction.transaction_id  # type: ignore

        if not transaction_id:
            raise Exception("Transaction missing transaction_id")

        logger.debug("[%s] Got transaction", transaction_id)

        # Reject malformed transactions early: reject if too many PDUs/EDUs
        if len(transaction.pdus) > 50 or (  # type: ignore
            hasattr(transaction, "edus") and len(transaction.edus) > 100  # type: ignore
        ):
            logger.info("Transaction PDU or EDU count too large. Returning 400")
            return 400, {}

        # we only process one transaction from each origin at a time. We need to do
        # this check here, rather than in _on_incoming_transaction_inner so that we
        # don't cache the rejection in _transaction_resp_cache (so that if the txn
        # arrives again later, we can process it).
        current_transaction = self._active_transactions.get(origin)
        if current_transaction and current_transaction != transaction_id:
            logger.warning(
                "Received another txn %s from %s while still processing %s",
                transaction_id,
                origin,
                current_transaction,
            )
            return 429, {
                "errcode": Codes.UNKNOWN,
                "error": "Too many concurrent transactions",
            }

        # CRITICAL SECTION: we must now not await until we populate _active_transactions
        # in _on_incoming_transaction_inner.

        # We wrap in a ResponseCache so that we de-duplicate retried
        # transactions.
        return await self._transaction_resp_cache.wrap(
            (origin, transaction_id),
            self._on_incoming_transaction_inner,
            origin,
            transaction,
            request_time,
        )

    async def _on_incoming_transaction_inner(
        self, origin: str, transaction: Transaction, request_time: int
    ) -> Tuple[int, Dict[str, Any]]:
        # CRITICAL SECTION: the first thing we must do (before awaiting) is
        # add an entry to _active_transactions.
        assert origin not in self._active_transactions
        self._active_transactions[origin] = transaction.transaction_id  # type: ignore

        try:
            result = await self._handle_incoming_transaction(
                origin, transaction, request_time
            )
            return result
        finally:
            del self._active_transactions[origin]

    async def _handle_incoming_transaction(
        self, origin: str, transaction: Transaction, request_time: int
    ) -> Tuple[int, Dict[str, Any]]:
        """Process an incoming transaction and return the HTTP response

        Args:
            origin: the server making the request
            transaction: incoming transaction
            request_time: timestamp that the HTTP request arrived at

        Returns:
            HTTP response code and body
        """
        response = await self.transaction_actions.have_responded(origin, transaction)

        if response:
            logger.debug(
                "[%s] We've already responded to this request",
                transaction.transaction_id,  # type: ignore
            )
            return response

        logger.debug("[%s] Transaction is new", transaction.transaction_id)  # type: ignore

        # We process PDUs and EDUs in parallel. This is important as we don't
        # want to block things like to device messages from reaching clients
        # behind the potentially expensive handling of PDUs.
        pdu_results, _ = await make_deferred_yieldable(
            defer.gatherResults(
                [
                    run_in_background(
                        self._handle_pdus_in_txn, origin, transaction, request_time
                    ),
                    run_in_background(self._handle_edus_in_txn, origin, transaction),
                ],
                consumeErrors=True,
            ).addErrback(unwrapFirstError)
        )

        response = {"pdus": pdu_results}

        logger.debug("Returning: %s", str(response))

        await self.transaction_actions.set_response(origin, transaction, 200, response)
        return 200, response

    async def _handle_pdus_in_txn(
        self, origin: str, transaction: Transaction, request_time: int
    ) -> Dict[str, dict]:
        """Process the PDUs in a received transaction.

        Args:
            origin: the server making the request
            transaction: incoming transaction
            request_time: timestamp that the HTTP request arrived at

        Returns:
            A map from event ID of a processed PDU to any errors we should
            report back to the sending server.
        """

        received_pdus_counter.inc(len(transaction.pdus))  # type: ignore

        origin_host, _ = parse_server_name(origin)

        pdus_by_room = {}  # type: Dict[str, List[EventBase]]

        newest_pdu_ts = 0

        for p in transaction.pdus:  # type: ignore
            # FIXME (richardv): I don't think this works:
            #  https://github.com/matrix-org/synapse/issues/8429
            if "unsigned" in p:
                unsigned = p["unsigned"]
                if "age" in unsigned:
                    p["age"] = unsigned["age"]
            if "age" in p:
                p["age_ts"] = request_time - int(p["age"])
                del p["age"]

            # We try and pull out an event ID so that if later checks fail we
            # can log something sensible. We don't mandate an event ID here in
            # case future event formats get rid of the key.
            possible_event_id = p.get("event_id", "<Unknown>")

            # Now we get the room ID so that we can check that we know the
            # version of the room.
            room_id = p.get("room_id")
            if not room_id:
                logger.info(
                    "Ignoring PDU as does not have a room_id. Event ID: %s",
                    possible_event_id,
                )
                continue

            try:
                room_version = await self.store.get_room_version(room_id)
            except NotFoundError:
                logger.info("Ignoring PDU for unknown room_id: %s", room_id)
                continue
            except UnsupportedRoomVersionError as e:
                # this can happen if support for a given room version is withdrawn,
                # so that we still get events for said room.
                logger.info("Ignoring PDU: %s", e)
                continue

            event = event_from_pdu_json(p, room_version)
            pdus_by_room.setdefault(room_id, []).append(event)

            if event.origin_server_ts > newest_pdu_ts:
                newest_pdu_ts = event.origin_server_ts

        pdu_results = {}

        # we can process different rooms in parallel (which is useful if they
        # require callouts to other servers to fetch missing events), but
        # impose a limit to avoid going too crazy with ram/cpu.

        async def process_pdus_for_room(room_id: str):
            with nested_logging_context(room_id):
                logger.debug("Processing PDUs for %s", room_id)

                try:
                    await self.check_server_matches_acl(origin_host, room_id)
                except AuthError as e:
                    logger.warning(
                        "Ignoring PDUs for room %s from banned server", room_id
                    )
                    for pdu in pdus_by_room[room_id]:
                        event_id = pdu.event_id
                        pdu_results[event_id] = e.error_dict()
                    return

                for pdu in pdus_by_room[room_id]:
                    pdu_results[pdu.event_id] = await process_pdu(pdu)

        async def process_pdu(pdu: EventBase) -> JsonDict:
            event_id = pdu.event_id
            with pdu_process_time.time():
                with nested_logging_context(event_id):
                    try:
                        await self._handle_received_pdu(origin, pdu)
                        return {}
                    except FederationError as e:
                        logger.warning("Error handling PDU %s: %s", event_id, e)
                        return {"error": str(e)}
                    except Exception as e:
                        f = failure.Failure()
                        logger.error(
                            "Failed to handle PDU %s",
                            event_id,
                            exc_info=(f.type, f.value, f.getTracebackObject()),  # type: ignore
                        )
                        return {"error": str(e)}

        await concurrently_execute(
            process_pdus_for_room, pdus_by_room.keys(), TRANSACTION_CONCURRENCY_LIMIT
        )

        if newest_pdu_ts and origin in self._federation_metrics_domains:
            last_pdu_ts_metric.labels(server_name=origin).set(newest_pdu_ts / 1000)

        return pdu_results

    async def _handle_edus_in_txn(self, origin: str, transaction: Transaction):
        """Process the EDUs in a received transaction."""

        async def _process_edu(edu_dict):
            received_edus_counter.inc()

            edu = Edu(
                origin=origin,
                destination=self.server_name,
                edu_type=edu_dict["edu_type"],
                content=edu_dict["content"],
            )
            await self.registry.on_edu(edu.edu_type, origin, edu.content)

        await concurrently_execute(
            _process_edu,
            getattr(transaction, "edus", []),
            TRANSACTION_CONCURRENCY_LIMIT,
        )

    async def on_room_state_request(
        self, origin: str, room_id: str, event_id: Optional[str]
    ) -> Tuple[int, Dict[str, Any]]:
        origin_host, _ = parse_server_name(origin)
        await self.check_server_matches_acl(origin_host, room_id)

        in_room = await self.auth.check_host_in_room(room_id, origin)
        if not in_room:
            raise AuthError(403, "Host not in room.")

        # we grab the linearizer to protect ourselves from servers which hammer
        # us. In theory we might already have the response to this query
        # in the cache so we could return it without waiting for the linearizer
        # - but that's non-trivial to get right, and anyway somewhat defeats
        # the point of the linearizer.
        with (await self._server_linearizer.queue((origin, room_id))):
            resp = dict(
                await self._state_resp_cache.wrap(
                    (room_id, event_id),
                    self._on_context_state_request_compute,
                    room_id,
                    event_id,
                )
            )

        room_version = await self.store.get_room_version_id(room_id)
        resp["room_version"] = room_version

        return 200, resp

    async def on_state_ids_request(
        self, origin: str, room_id: str, event_id: str
    ) -> Tuple[int, Dict[str, Any]]:
        if not event_id:
            raise NotImplementedError("Specify an event")

        origin_host, _ = parse_server_name(origin)
        await self.check_server_matches_acl(origin_host, room_id)

        in_room = await self.auth.check_host_in_room(room_id, origin)
        if not in_room:
            raise AuthError(403, "Host not in room.")

        resp = await self._state_ids_resp_cache.wrap(
            (room_id, event_id),
            self._on_state_ids_request_compute,
            room_id,
            event_id,
        )

        return 200, resp

    async def _on_state_ids_request_compute(self, room_id, event_id):
        state_ids = await self.handler.get_state_ids_for_pdu(room_id, event_id)
        auth_chain_ids = await self.store.get_auth_chain_ids(room_id, state_ids)
        return {"pdu_ids": state_ids, "auth_chain_ids": auth_chain_ids}

    async def _on_context_state_request_compute(
        self, room_id: str, event_id: Optional[str]
    ) -> Dict[str, list]:
        if event_id:
            pdus = await self.handler.get_state_for_pdu(
                room_id, event_id
            )  # type: Iterable[EventBase]
        else:
            pdus = (await self.state.get_current_state(room_id)).values()

        auth_chain = await self.store.get_auth_chain(
            room_id, [pdu.event_id for pdu in pdus]
        )

        return {
            "pdus": [pdu.get_pdu_json() for pdu in pdus],
            "auth_chain": [pdu.get_pdu_json() for pdu in auth_chain],
        }

    async def on_pdu_request(
        self, origin: str, event_id: str
    ) -> Tuple[int, Union[JsonDict, str]]:
        pdu = await self.handler.get_persisted_pdu(origin, event_id)

        if pdu:
            return 200, self._transaction_from_pdus([pdu]).get_dict()
        else:
            return 404, ""

    async def on_query_request(
        self, query_type: str, args: Dict[str, str]
    ) -> Tuple[int, Dict[str, Any]]:
        received_queries_counter.labels(query_type).inc()
        resp = await self.registry.on_query(query_type, args)
        return 200, resp

    async def on_make_join_request(
        self, origin: str, room_id: str, user_id: str, supported_versions: List[str]
    ) -> Dict[str, Any]:
        origin_host, _ = parse_server_name(origin)
        await self.check_server_matches_acl(origin_host, room_id)

        room_version = await self.store.get_room_version_id(room_id)
        if room_version not in supported_versions:
            logger.warning(
                "Room version %s not in %s", room_version, supported_versions
            )
            raise IncompatibleRoomVersionError(room_version=room_version)

        pdu = await self.handler.on_make_join_request(origin, room_id, user_id)
        time_now = self._clock.time_msec()
        return {"event": pdu.get_pdu_json(time_now), "room_version": room_version}

    async def on_invite_request(
        self, origin: str, content: JsonDict, room_version_id: str
    ) -> Dict[str, Any]:
        room_version = KNOWN_ROOM_VERSIONS.get(room_version_id)
        if not room_version:
            raise SynapseError(
                400,
                "Homeserver does not support this room version",
                Codes.UNSUPPORTED_ROOM_VERSION,
            )

        pdu = event_from_pdu_json(content, room_version)
        origin_host, _ = parse_server_name(origin)
        await self.check_server_matches_acl(origin_host, pdu.room_id)
        pdu = await self._check_sigs_and_hash(room_version, pdu)
        ret_pdu = await self.handler.on_invite_request(origin, pdu, room_version)
        time_now = self._clock.time_msec()
        return {"event": ret_pdu.get_pdu_json(time_now)}

    async def on_send_join_request(
        self, origin: str, content: JsonDict, room_id: str
    ) -> Dict[str, Any]:
        context = await self._on_send_membership_event(
            origin, content, Membership.JOIN, room_id
        )

        prev_state_ids = await context.get_prev_state_ids()
        state_ids = list(prev_state_ids.values())
        auth_chain = await self.store.get_auth_chain(room_id, state_ids)
        state = await self.store.get_events(state_ids)

        time_now = self._clock.time_msec()
        return {
            "state": [p.get_pdu_json(time_now) for p in state.values()],
            "auth_chain": [p.get_pdu_json(time_now) for p in auth_chain],
        }

    async def on_make_leave_request(
        self, origin: str, room_id: str, user_id: str
    ) -> Dict[str, Any]:
        origin_host, _ = parse_server_name(origin)
        await self.check_server_matches_acl(origin_host, room_id)
        pdu = await self.handler.on_make_leave_request(origin, room_id, user_id)

        room_version = await self.store.get_room_version_id(room_id)

        time_now = self._clock.time_msec()
        return {"event": pdu.get_pdu_json(time_now), "room_version": room_version}

    async def on_send_leave_request(
        self, origin: str, content: JsonDict, room_id: str
    ) -> dict:
        logger.debug("on_send_leave_request: content: %s", content)
        await self._on_send_membership_event(origin, content, Membership.LEAVE, room_id)
        return {}

    async def on_make_knock_request(
        self, origin: str, room_id: str, user_id: str, supported_versions: List[str]
    ) -> Dict[str, Union[EventBase, str]]:
        """We've received a /make_knock/ request, so we create a partial knock
        event for the room and hand that back, along with the room version, to the knocking
        homeserver. We do *not* persist or process this event until the other server has
        signed it and sent it back.

        Args:
            origin: The (verified) server name of the requesting server.
            room_id: The room to create the knock event in.
            user_id: The user to create the knock for.
            supported_versions: The room versions supported by the requesting server.

        Returns:
            The partial knock event.
        """
        origin_host, _ = parse_server_name(origin)
        await self.check_server_matches_acl(origin_host, room_id)

        room_version = await self.store.get_room_version(room_id)

        # Check that this room version is supported by the remote homeserver
        if room_version.identifier not in supported_versions:
            logger.warning(
                "Room version %s not in %s", room_version.identifier, supported_versions
            )
            raise IncompatibleRoomVersionError(room_version=room_version.identifier)

        # Check that this room supports knocking as defined by its room version
        if not room_version.msc2403_knocking:
            raise SynapseError(
                403,
                "This room version does not support knocking",
                errcode=Codes.FORBIDDEN,
            )

        pdu = await self.handler.on_make_knock_request(origin, room_id, user_id)
        time_now = self._clock.time_msec()
        return {
            "event": pdu.get_pdu_json(time_now),
            "room_version": room_version.identifier,
        }

    async def on_send_knock_request(
        self,
        origin: str,
        content: JsonDict,
        room_id: str,
    ) -> Dict[str, List[JsonDict]]:
        """
        We have received a knock event for a room. Verify and send the event into the room
        on the knocking homeserver's behalf. Then reply with some stripped state from the
        room for the knockee.

        Args:
            origin: The remote homeserver of the knocking user.
            content: The content of the request.
            room_id: The ID of the room to knock on.

        Returns:
            The stripped room state.
        """
        event_context = await self._on_send_membership_event(
            origin, content, Membership.KNOCK, room_id
        )

        # Retrieve stripped state events from the room and send them back to the remote
        # server. This will allow the remote server's clients to display information
        # related to the room while the knock request is pending.
        stripped_room_state = (
            await self.store.get_stripped_room_state_from_event_context(
                event_context, self._room_prejoin_state_types
            )
        )
        return {"knock_state_events": stripped_room_state}

    async def _on_send_membership_event(
        self, origin: str, content: JsonDict, membership_type: str, room_id: str
    ) -> EventContext:
        """Handle an on_send_{join,leave,knock} request

        Does some preliminary validation before passing the request on to the
        federation handler.

        Args:
            origin: The (authenticated) requesting server
            content: The body of the send_* request - a complete membership event
            membership_type: The expected membership type (join or leave, depending
                on the endpoint)
            room_id: The room_id from the request, to be validated against the room_id
                in the event

        Returns:
            The context of the event after inserting it into the room graph.

        Raises:
            SynapseError if there is a problem with the request, including things like
               the room_id not matching or the event not being authorized.
        """
        assert_params_in_dict(content, ["room_id"])
        if content["room_id"] != room_id:
            raise SynapseError(
                400,
                "Room ID in body does not match that in request path",
                Codes.BAD_JSON,
            )

        room_version = await self.store.get_room_version(room_id)

        if membership_type == Membership.KNOCK and not room_version.msc2403_knocking:
            raise SynapseError(
                403,
                "This room version does not support knocking",
                errcode=Codes.FORBIDDEN,
            )

        event = event_from_pdu_json(content, room_version)

        if event.type != EventTypes.Member or not event.is_state():
            raise SynapseError(400, "Not an m.room.member event", Codes.BAD_JSON)

        if event.content.get("membership") != membership_type:
            raise SynapseError(400, "Not a %s event" % membership_type, Codes.BAD_JSON)

        origin_host, _ = parse_server_name(origin)
        await self.check_server_matches_acl(origin_host, event.room_id)

        logger.debug("_on_send_membership_event: pdu sigs: %s", event.signatures)

        event = await self._check_sigs_and_hash(room_version, event)

        return await self.handler.on_send_membership_event(origin, event)

    async def on_event_auth(
        self, origin: str, room_id: str, event_id: str
    ) -> Tuple[int, Dict[str, Any]]:
        with (await self._server_linearizer.queue((origin, room_id))):
            origin_host, _ = parse_server_name(origin)
            await self.check_server_matches_acl(origin_host, room_id)

            time_now = self._clock.time_msec()
            auth_pdus = await self.handler.on_event_auth(event_id)
            res = {"auth_chain": [a.get_pdu_json(time_now) for a in auth_pdus]}
        return 200, res

    @log_function
    async def on_query_client_keys(
        self, origin: str, content: Dict[str, str]
    ) -> Tuple[int, Dict[str, Any]]:
        return await self.on_query_request("client_keys", content)

    async def on_query_user_devices(
        self, origin: str, user_id: str
    ) -> Tuple[int, Dict[str, Any]]:
        keys = await self.device_handler.on_federation_query_user_devices(user_id)
        return 200, keys

    @trace
    async def on_claim_client_keys(
        self, origin: str, content: JsonDict
    ) -> Dict[str, Any]:
        query = []
        for user_id, device_keys in content.get("one_time_keys", {}).items():
            for device_id, algorithm in device_keys.items():
                query.append((user_id, device_id, algorithm))

        log_kv({"message": "Claiming one time keys.", "user, device pairs": query})
        results = await self.store.claim_e2e_one_time_keys(query)

        json_result = {}  # type: Dict[str, Dict[str, dict]]
        for user_id, device_keys in results.items():
            for device_id, keys in device_keys.items():
                for key_id, json_str in keys.items():
                    json_result.setdefault(user_id, {})[device_id] = {
                        key_id: json_decoder.decode(json_str)
                    }

        logger.info(
            "Claimed one-time-keys: %s",
            ",".join(
                (
                    "%s for %s:%s" % (key_id, user_id, device_id)
                    for user_id, user_keys in json_result.items()
                    for device_id, device_keys in user_keys.items()
                    for key_id, _ in device_keys.items()
                )
            ),
        )

        return {"one_time_keys": json_result}

    async def on_get_missing_events(
        self,
        origin: str,
        room_id: str,
        earliest_events: List[str],
        latest_events: List[str],
        limit: int,
    ) -> Dict[str, list]:
        with (await self._server_linearizer.queue((origin, room_id))):
            origin_host, _ = parse_server_name(origin)
            await self.check_server_matches_acl(origin_host, room_id)

            logger.debug(
                "on_get_missing_events: earliest_events: %r, latest_events: %r,"
                " limit: %d",
                earliest_events,
                latest_events,
                limit,
            )

            missing_events = await self.handler.on_get_missing_events(
                origin, room_id, earliest_events, latest_events, limit
            )

            if len(missing_events) < 5:
                logger.debug(
                    "Returning %d events: %r", len(missing_events), missing_events
                )
            else:
                logger.debug("Returning %d events", len(missing_events))

            time_now = self._clock.time_msec()

        return {"events": [ev.get_pdu_json(time_now) for ev in missing_events]}

    @log_function
    async def on_openid_userinfo(self, token: str) -> Optional[str]:
        ts_now_ms = self._clock.time_msec()
        return await self.store.get_user_id_for_open_id_token(token, ts_now_ms)

    def _transaction_from_pdus(self, pdu_list: List[EventBase]) -> Transaction:
        """Returns a new Transaction containing the given PDUs suitable for
        transmission.
        """
        time_now = self._clock.time_msec()
        pdus = [p.get_pdu_json(time_now) for p in pdu_list]
        return Transaction(
            origin=self.server_name,
            pdus=pdus,
            origin_server_ts=int(time_now),
            destination=None,
        )

    async def _handle_received_pdu(self, origin: str, pdu: EventBase) -> None:
        """Process a PDU received in a federation /send/ transaction.

        If the event is invalid, then this method throws a FederationError.
        (The error will then be logged and sent back to the sender (which
        probably won't do anything with it), and other events in the
        transaction will be processed as normal).

        It is likely that we'll then receive other events which refer to
        this rejected_event in their prev_events, etc.  When that happens,
        we'll attempt to fetch the rejected event again, which will presumably
        fail, so those second-generation events will also get rejected.

        Eventually, we get to the point where there are more than 10 events
        between any new events and the original rejected event. Since we
        only try to backfill 10 events deep on received pdu, we then accept the
        new event, possibly introducing a discontinuity in the DAG, with new
        forward extremities, so normal service is approximately returned,
        until we try to backfill across the discontinuity.

        Args:
            origin: server which sent the pdu
            pdu: received pdu

        Raises: FederationError if the signatures / hash do not match, or
            if the event was unacceptable for any other reason (eg, too large,
            too many prev_events, couldn't find the prev_events)
        """

        # We've already checked that we know the room version by this point
        room_version = await self.store.get_room_version(pdu.room_id)

        # Check signature.
        try:
            pdu = await self._check_sigs_and_hash(room_version, pdu)
        except SynapseError as e:
            raise FederationError("ERROR", e.code, e.msg, affected=pdu.event_id)

        await self.handler.on_receive_pdu(origin, pdu, sent_to_us_directly=True)

    def __str__(self) -> str:
        return "<ReplicationLayer(%s)>" % self.server_name

    async def exchange_third_party_invite(
        self, sender_user_id: str, target_user_id: str, room_id: str, signed: Dict
    ) -> None:
        await self.handler.exchange_third_party_invite(
            sender_user_id, target_user_id, room_id, signed
        )

    async def on_exchange_third_party_invite_request(self, event_dict: Dict) -> None:
        await self.handler.on_exchange_third_party_invite_request(event_dict)

    async def check_server_matches_acl(self, server_name: str, room_id: str) -> None:
        """Check if the given server is allowed by the server ACLs in the room

        Args:
            server_name: name of server, *without any port part*
            room_id: ID of the room to check

        Raises:
            AuthError if the server does not match the ACL
        """
        state_ids = await self.store.get_current_state_ids(room_id)
        acl_event_id = state_ids.get((EventTypes.ServerACL, ""))

        if not acl_event_id:
            return

        acl_event = await self.store.get_event(acl_event_id)
        if server_matches_acl_event(server_name, acl_event):
            return

        raise AuthError(code=403, msg="Server is banned from room")


def server_matches_acl_event(server_name: str, acl_event: EventBase) -> bool:
    """Check if the given server is allowed by the ACL event

    Args:
        server_name: name of server, without any port part
        acl_event: m.room.server_acl event

    Returns:
        True if this server is allowed by the ACLs
    """
    logger.debug("Checking %s against acl %s", server_name, acl_event.content)

    # first of all, check if literal IPs are blocked, and if so, whether the
    # server name is a literal IP
    allow_ip_literals = acl_event.content.get("allow_ip_literals", True)
    if not isinstance(allow_ip_literals, bool):
        logger.warning("Ignoring non-bool allow_ip_literals flag")
        allow_ip_literals = True
    if not allow_ip_literals:
        # check for ipv6 literals. These start with '['.
        if server_name[0] == "[":
            return False

        # check for ipv4 literals. We can just lift the routine from twisted.
        if isIPAddress(server_name):
            return False

    # next,  check the deny list
    deny = acl_event.content.get("deny", [])
    if not isinstance(deny, (list, tuple)):
        logger.warning("Ignoring non-list deny ACL %s", deny)
        deny = []
    for e in deny:
        if _acl_entry_matches(server_name, e):
            # logger.info("%s matched deny rule %s", server_name, e)
            return False

    # then the allow list.
    allow = acl_event.content.get("allow", [])
    if not isinstance(allow, (list, tuple)):
        logger.warning("Ignoring non-list allow ACL %s", allow)
        allow = []
    for e in allow:
        if _acl_entry_matches(server_name, e):
            # logger.info("%s matched allow rule %s", server_name, e)
            return True

    # everything else should be rejected.
    # logger.info("%s fell through", server_name)
    return False


def _acl_entry_matches(server_name: str, acl_entry: Any) -> bool:
    if not isinstance(acl_entry, str):
        logger.warning(
            "Ignoring non-str ACL entry '%s' (is %s)", acl_entry, type(acl_entry)
        )
        return False
    regex = glob_to_regex(acl_entry)
    return bool(regex.match(server_name))


class FederationHandlerRegistry:
    """Allows classes to register themselves as handlers for a given EDU or
    query type for incoming federation traffic.
    """

    def __init__(self, hs: "HomeServer"):
        self.config = hs.config
        self.clock = hs.get_clock()
        self._instance_name = hs.get_instance_name()

        # These are safe to load in monolith mode, but will explode if we try
        # and use them. However we have guards before we use them to ensure that
        # we don't route to ourselves, and in monolith mode that will always be
        # the case.
        self._get_query_client = ReplicationGetQueryRestServlet.make_client(hs)
        self._send_edu = ReplicationFederationSendEduRestServlet.make_client(hs)

        self.edu_handlers = (
            {}
        )  # type: Dict[str, Callable[[str, dict], Awaitable[None]]]
        self.query_handlers = (
            {}
        )  # type: Dict[str, Callable[[dict], Awaitable[JsonDict]]]

        # Map from type to instance names that we should route EDU handling to.
        # We randomly choose one instance from the list to route to for each new
        # EDU received.
        self._edu_type_to_instance = {}  # type: Dict[str, List[str]]

    def register_edu_handler(
        self, edu_type: str, handler: Callable[[str, JsonDict], Awaitable[None]]
    ) -> None:
        """Sets the handler callable that will be used to handle an incoming
        federation EDU of the given type.

        Args:
            edu_type: The type of the incoming EDU to register handler for
            handler: A callable invoked on incoming EDU
                of the given type. The arguments are the origin server name and
                the EDU contents.
        """
        if edu_type in self.edu_handlers:
            raise KeyError("Already have an EDU handler for %s" % (edu_type,))

        logger.info("Registering federation EDU handler for %r", edu_type)

        self.edu_handlers[edu_type] = handler

    def register_query_handler(
        self, query_type: str, handler: Callable[[dict], Awaitable[JsonDict]]
    ) -> None:
        """Sets the handler callable that will be used to handle an incoming
        federation query of the given type.

        Args:
            query_type: Category name of the query, which should match
                the string used by make_query.
            handler: Invoked to handle
                incoming queries of this type. The return will be yielded
                on and the result used as the response to the query request.
        """
        if query_type in self.query_handlers:
            raise KeyError("Already have a Query handler for %s" % (query_type,))

        logger.info("Registering federation query handler for %r", query_type)

        self.query_handlers[query_type] = handler

    def register_instance_for_edu(self, edu_type: str, instance_name: str) -> None:
        """Register that the EDU handler is on a different instance than master."""
        self._edu_type_to_instance[edu_type] = [instance_name]

    def register_instances_for_edu(
        self, edu_type: str, instance_names: List[str]
    ) -> None:
        """Register that the EDU handler is on multiple instances."""
        self._edu_type_to_instance[edu_type] = instance_names

    async def on_edu(self, edu_type: str, origin: str, content: dict) -> None:
        if not self.config.use_presence and edu_type == EduTypes.Presence:
            return

        # Check if we have a handler on this instance
        handler = self.edu_handlers.get(edu_type)
        if handler:
            with start_active_span_from_edu(content, "handle_edu"):
                try:
                    await handler(origin, content)
                except SynapseError as e:
                    logger.info("Failed to handle edu %r: %r", edu_type, e)
                except Exception:
                    logger.exception("Failed to handle edu %r", edu_type)
            return

        # Check if we can route it somewhere else that isn't us
        instances = self._edu_type_to_instance.get(edu_type, ["master"])
        if self._instance_name not in instances:
            # Pick an instance randomly so that we don't overload one.
            route_to = random.choice(instances)

            try:
                await self._send_edu(
                    instance_name=route_to,
                    edu_type=edu_type,
                    origin=origin,
                    content=content,
                )
            except SynapseError as e:
                logger.info("Failed to handle edu %r: %r", edu_type, e)
            except Exception:
                logger.exception("Failed to handle edu %r", edu_type)
            return

        # Oh well, let's just log and move on.
        logger.warning("No handler registered for EDU type %s", edu_type)

    async def on_query(self, query_type: str, args: dict) -> JsonDict:
        handler = self.query_handlers.get(query_type)
        if handler:
            return await handler(args)

        # Check if we can route it somewhere else that isn't us
        if self._instance_name == "master":
            return await self._get_query_client(query_type=query_type, args=args)

        # Uh oh, no handler! Let's raise an exception so the request returns an
        # error.
        logger.warning("No handler registered for query type %s", query_type)
        raise NotFoundError("No handler for Query type '%s'" % (query_type,))