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Exclude OOB memberships from the federation sender (#12570)

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As the comment says, there is no need to process such events, and indeed we
need to avoid doing so.

Fixes #12509.
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Richard van der Hoff 2022-05-03 13:47:56 +01:00 committed by GitHub
parent 13e4386710
commit db2edf5a65
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3 changed files with 51 additions and 4 deletions
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1
changelog.d/12570.bugfix Normal file
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@ -0,0 +1 @@
Fix a bug introduced in Synapse 1.57 which could cause `Failed to calculate hosts in room` errors to be logged for outbound federation.

15
synapse/events/__init__.py
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@ -213,10 +213,17 @@ class _EventInternalMetadata:
return self.outlier
def is_out_of_band_membership(self) -> bool:
"""Whether this is an out of band membership, like an invite or an invite
rejection. This is needed as those events are marked as outliers, but
they still need to be processed as if they're new events (e.g. updating
invite state in the database, relaying to clients, etc).
"""Whether this event is an out-of-band membership.
OOB memberships are a special case of outlier events: they are membership events
for federated rooms that we aren't full members. Examples include invites
received over federation, and rejections for such invites.
The concept of an OOB membership is needed because these events need to be
processed as if they're new regular events (e.g. updating membership state in
the database, relaying to clients via /sync, etc) despite being outliers.
See also https://matrix-org.github.io/synapse/develop/development/room-dag-concepts.html#out-of-band-membership-events.
(Added in synapse 0.99.0, so may be unreliable for events received before that)
"""

39
synapse/federation/sender/__init__.py
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@ -355,6 +355,45 @@ class FederationSender(AbstractFederationSender):
if not is_mine and send_on_behalf_of is None:
return
# We also want to not send out-of-band membership events.
#
# OOB memberships are used in three (and a half) situations:
#
# (1) invite events which we have received over federation. Those
# will have a `sender` on a different server, so will be
# skipped by the "is_mine" test above anyway.
#
# (2) rejections of invites to federated rooms - either remotely
# or locally generated. (Such rejections are normally
# created via federation, in which case the remote server is
# responsible for sending out the rejection. If that fails,
# we'll create a leave event locally, but that's only really
# for the benefit of the invited user - we don't have enough
# information to send it out over federation).
#
# (2a) rescinded knocks. These are identical to rejected invites.
#
# (3) knock events which we have sent over federation. As with
# invite rejections, the remote server should send them out to
# the federation.
#
# So, in all the above cases, we want to ignore such events.
#
# OOB memberships are always(?) outliers anyway, so if we *don't*
# ignore them, we'll get an exception further down when we try to
# fetch the membership list for the room.
#
# Arguably, we could equivalently ignore all outliers here, since
# in theory the only way for an outlier with a local `sender` to
# exist is by being an OOB membership (via one of (2), (2a) or (3)
# above).
#
if event.internal_metadata.is_out_of_band_membership():
return
# Finally, there are some other events that we should not send out
# until someone asks for them. They are explicitly flagged as such
# with `proactively_send: False`.
if not event.internal_metadata.should_proactively_send():
return