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Comments and interface cleanup for on_receive_pdu

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Add some informative comments about what's going on here.

Also, `sent_to_us_directly` and `get_missing` were doing the same thing (apart
from in `_handle_queued_pdus`, which looks like a bug), so let's get rid of
`get_missing` and use `sent_to_us_directly` consistently.
This commit is contained in:
Richard van der Hoff 2018-09-20 13:06:55 +01:00
parent 1f3f5fcf52
commit 703de4ec13
2 changed files with 47 additions and 24 deletions
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2
synapse/federation/federation_server.py
View File

@ -618,7 +618,7 @@ class FederationServer(FederationBase):
)
yield self.handler.on_receive_pdu(
origin, pdu, get_missing=True, sent_to_us_directly=True,
origin, pdu, sent_to_us_directly=True,
)
def __str__(self):

69
synapse/handlers/federation.py
View File

@ -136,7 +136,7 @@ class FederationHandler(BaseHandler):
@defer.inlineCallbacks
def on_receive_pdu(
self, origin, pdu, get_missing=True, sent_to_us_directly=False,
self, origin, pdu, sent_to_us_directly=False,
):
""" Process a PDU received via a federation /send/ transaction, or
via backfill of missing prev_events
@ -145,7 +145,8 @@ class FederationHandler(BaseHandler):
origin (str): server which initiated the /send/ transaction. Will
be used to fetch missing events or state.
pdu (FrozenEvent): received PDU
get_missing (bool): True if we should fetch missing prev_events
sent_to_us_directly (bool): True if this event was pushed to us; False if
we pulled it as the result of a missing prev_event.
Returns (Deferred): completes with None
"""
@ -250,7 +251,7 @@ class FederationHandler(BaseHandler):
pdu.internal_metadata.outlier = True
elif min_depth and pdu.depth > min_depth:
missing_prevs = prevs - seen
if get_missing and missing_prevs:
if sent_to_us_directly and missing_prevs:
# If we're missing stuff, ensure we only fetch stuff one
# at a time.
logger.info(
@ -282,24 +283,46 @@ class FederationHandler(BaseHandler):
room_id, event_id, len(missing_prevs), shortstr(missing_prevs),
)
if sent_to_us_directly and prevs - seen:
# If they have sent it to us directly, and the server
# isn't telling us about the auth events that it's
# made a message referencing, we explode
logger.warn(
"[%s %s] Failed to fetch %d prev events: rejecting",
room_id, event_id, len(prevs - seen),
)
raise FederationError(
"ERROR",
403,
(
"Your server isn't divulging details about prev_events "
"referenced in this event."
),
affected=pdu.event_id,
)
elif prevs - seen:
if prevs - seen:
# We've still not been able to get all of the prev_events for this event.
#
# In this case, we need to fall back to asking another server in the
# federation for the state at this event. That's ok provided we then
# resolve the state against other bits of the DAG before using it (which
# will ensure that you can't just take over a room by sending an event,
# withholding its prev_events, and declaring yourself to be an admin in
# the subsequent state request).
#
# Now, if we're pulling this event as a missing prev_event, then clearly
# this event is not going to become the only forward-extremity and we are
# guaranteed to resolve its state against our existing forward
# extremities, so that should be fine.
#
# On the other hand, if this event was pushed to us, it is possible for
# it to become the only forward-extremity in the room, and we would then
# trust its state to be the state for the whole room. This is very bad.
# Further, if the event was pushed to us, there is no excuse for us not to
# have all the prev_events. We therefore reject any such events.
#
# XXX this really feels like it could/should be merged with the above,
# but there is an interaction with min_depth that I'm not really
# following.
if sent_to_us_directly:
logger.warn(
"[%s %s] Failed to fetch %d prev events: rejecting",
room_id, event_id, len(prevs - seen),
)
raise FederationError(
"ERROR",
403,
(
"Your server isn't divulging details about prev_events "
"referenced in this event."
),
affected=pdu.event_id,
)
# Calculate the state of the previous events, and
# de-conflict them to find the current state.
state_groups = []
@ -464,7 +487,7 @@ class FederationHandler(BaseHandler):
yield self.on_receive_pdu(
origin,
ev,
get_missing=False
sent_to_us_directly=False,
)
except FederationError as e:
if e.code == 403:
@ -1112,7 +1135,7 @@ class FederationHandler(BaseHandler):
try:
logger.info("Processing queued PDU %s which was received "
"while we were joining %s", p.event_id, p.room_id)
yield self.on_receive_pdu(origin, p)
yield self.on_receive_pdu(origin, p, sent_to_us_directly=True)
except Exception as e:
logger.warn(
"Error handling queued PDU %s from %s: %s",