package input import ( "context" "errors" "fmt" "sync" "time" fedapi "github.com/matrix-org/dendrite/federationapi/api" "github.com/matrix-org/dendrite/internal" "github.com/matrix-org/dendrite/roomserver/api" "github.com/matrix-org/dendrite/roomserver/state" "github.com/matrix-org/dendrite/roomserver/storage" "github.com/matrix-org/dendrite/roomserver/types" "github.com/matrix-org/gomatrixserverlib" "github.com/matrix-org/util" "github.com/sirupsen/logrus" ) type parsedRespState struct { AuthEvents []*gomatrixserverlib.Event StateEvents []*gomatrixserverlib.Event } func (p *parsedRespState) Events() []*gomatrixserverlib.Event { eventsByID := make(map[string]*gomatrixserverlib.Event, len(p.AuthEvents)+len(p.StateEvents)) for i, event := range p.AuthEvents { eventsByID[event.EventID()] = p.AuthEvents[i] } for i, event := range p.StateEvents { eventsByID[event.EventID()] = p.StateEvents[i] } allEvents := make([]*gomatrixserverlib.Event, 0, len(eventsByID)) for _, event := range eventsByID { allEvents = append(allEvents, event) } return gomatrixserverlib.ReverseTopologicalOrdering(allEvents, gomatrixserverlib.TopologicalOrderByAuthEvents) } type missingStateReq struct { origin gomatrixserverlib.ServerName db storage.Database roomInfo *types.RoomInfo inputer *Inputer keys gomatrixserverlib.JSONVerifier federation fedapi.FederationInternalAPI roomsMu *internal.MutexByRoom servers []gomatrixserverlib.ServerName hadEvents map[string]bool hadEventsMutex sync.Mutex haveEvents map[string]*gomatrixserverlib.Event haveEventsMutex sync.Mutex } // processEventWithMissingState is the entrypoint for a missingStateReq // request, as called from processRoomEvent. // nolint:gocyclo func (t *missingStateReq) processEventWithMissingState( ctx context.Context, e *gomatrixserverlib.Event, roomVersion gomatrixserverlib.RoomVersion, ) (*parsedRespState, error) { // We are missing the previous events for this events. // This means that there is a gap in our view of the history of the // room. There two ways that we can handle such a gap: // 1) We can fill in the gap using /get_missing_events // 2) We can leave the gap and request the state of the room at // this event from the remote server using either /state_ids // or /state. // Synapse will attempt to do 1 and if that fails or if the gap is // too large then it will attempt 2. // Synapse will use /state_ids if possible since usually the state // is largely unchanged and it is more efficient to fetch a list of // event ids and then use /event to fetch the individual events. // However not all version of synapse support /state_ids so you may // need to fallback to /state. logger := util.GetLogger(ctx).WithFields(map[string]interface{}{ "txn_event": e.EventID(), "room_id": e.RoomID(), "txn_prev_events": e.PrevEventIDs(), }) // Attempt to fill in the gap using /get_missing_events // This will either: // - fill in the gap completely then process event `e` returning no backwards extremity // - fail to fill in the gap and tell us to terminate the transaction err=not nil // - fail to fill in the gap and tell us to fetch state at the new backwards extremity, and to not terminate the transaction newEvents, isGapFilled, prevStatesKnown, err := t.getMissingEvents(ctx, e, roomVersion) if err != nil { return nil, fmt.Errorf("t.getMissingEvents: %w", err) } if len(newEvents) == 0 { return nil, fmt.Errorf("expected to find missing events but didn't") } if isGapFilled { logger.Infof("Gap filled by /get_missing_events, injecting %d new events", len(newEvents)) // we can just inject all the newEvents as new as we may have only missed 1 or 2 events and have filled // in the gap in the DAG for _, newEvent := range newEvents { err = t.inputer.processRoomEvent(ctx, &api.InputRoomEvent{ Kind: api.KindOld, Event: newEvent.Headered(roomVersion), Origin: t.origin, SendAsServer: api.DoNotSendToOtherServers, }) if err != nil { if _, ok := err.(types.RejectedError); !ok { return nil, fmt.Errorf("t.inputer.processRoomEvent (filling gap): %w", err) } } } } // If we filled the gap *and* we know the state before the prev events // then there's nothing else to do, we have everything we need to deal // with the new event. if isGapFilled && prevStatesKnown { logger.Infof("Gap filled and state found for all prev events") return nil, nil } // Otherwise, if we've reached this point, it's possible that we've // either not closed the gap, or we did but we still don't seem to // know the events before the new event. Start by looking up the // state at the event at the back of the gap and we'll try to roll // forward the state first. backwardsExtremity := newEvents[0] newEvents = newEvents[1:] resolvedState, err := t.lookupResolvedStateBeforeEvent(ctx, backwardsExtremity, roomVersion) if err != nil { return nil, fmt.Errorf("t.lookupState (backwards extremity): %w", err) } hadEvents := map[string]bool{} t.hadEventsMutex.Lock() for k, v := range t.hadEvents { hadEvents[k] = v } t.hadEventsMutex.Unlock() sendOutliers := func(resolvedState *parsedRespState) error { outliers := resolvedState.Events() outlierRoomEvents := make([]api.InputRoomEvent, 0, len(outliers)) for _, outlier := range outliers { if hadEvents[outlier.EventID()] { continue } outlierRoomEvents = append(outlierRoomEvents, api.InputRoomEvent{ Kind: api.KindOutlier, Event: outlier.Headered(roomVersion), Origin: t.origin, }) } for _, ire := range outlierRoomEvents { if err = t.inputer.processRoomEvent(ctx, &ire); err != nil { if _, ok := err.(types.RejectedError); !ok { return fmt.Errorf("t.inputer.processRoomEvent (outlier): %w", err) } } } return nil } // Send outliers first so we can send the state along with the new backwards // extremity without any missing auth events. if err = sendOutliers(resolvedState); err != nil { return nil, fmt.Errorf("sendOutliers: %w", err) } // Now send the backward extremity into the roomserver with the // newly resolved state. This marks the "oldest" point in the backfill and // sets the baseline state for any new events after this. stateIDs := make([]string, 0, len(resolvedState.StateEvents)) for _, event := range resolvedState.StateEvents { stateIDs = append(stateIDs, event.EventID()) } err = t.inputer.processRoomEvent(ctx, &api.InputRoomEvent{ Kind: api.KindOld, Event: backwardsExtremity.Headered(roomVersion), Origin: t.origin, HasState: true, StateEventIDs: stateIDs, SendAsServer: api.DoNotSendToOtherServers, }) if err != nil { if _, ok := err.(types.RejectedError); !ok { return nil, fmt.Errorf("t.inputer.processRoomEvent (backward extremity): %w", err) } } // Then send all of the newer backfilled events, of which will all be newer // than the backward extremity, into the roomserver without state. This way // they will automatically fast-forward based on the room state at the // extremity in the last step. for _, newEvent := range newEvents { err = t.inputer.processRoomEvent(ctx, &api.InputRoomEvent{ Kind: api.KindOld, Event: newEvent.Headered(roomVersion), Origin: t.origin, SendAsServer: api.DoNotSendToOtherServers, }) if err != nil { if _, ok := err.(types.RejectedError); !ok { return nil, fmt.Errorf("t.inputer.processRoomEvent (fast forward): %w", err) } } } // Finally, check again if we know everything we need to know in order to // make forward progress. If the prev state is known then we consider the // rolled forward state to be sufficient — we now know all of the state // before the prev events. If we don't then we need to look up the state // before the new event as well, otherwise we will never make any progress. if t.isPrevStateKnown(ctx, e) { return nil, nil } // If we still haven't got the state for the prev events then we'll go and // ask the federation for it if needed. resolvedState, err = t.lookupResolvedStateBeforeEvent(ctx, e, roomVersion) if err != nil { return nil, fmt.Errorf("t.lookupState (new event): %w", err) } // Send the outliers for the retrieved state. if err = sendOutliers(resolvedState); err != nil { return nil, fmt.Errorf("sendOutliers: %w", err) } // Then return the resolved state, for which the caller can replace the // HasState with the event IDs to create a new state snapshot when we // process the new event. return resolvedState, nil } func (t *missingStateReq) lookupResolvedStateBeforeEvent(ctx context.Context, e *gomatrixserverlib.Event, roomVersion gomatrixserverlib.RoomVersion) (*parsedRespState, error) { type respState struct { // A snapshot is considered trustworthy if it came from our own roomserver. // That's because the state will have been through state resolution once // already in QueryStateAfterEvent. trustworthy bool *parsedRespState } // at this point we know we're going to have a gap: we need to work out the room state at the new backwards extremity. // Therefore, we cannot just query /state_ids with this event to get the state before. Instead, we need to query // the state AFTER all the prev_events for this event, then apply state resolution to that to get the state before the event. var states []*respState for _, prevEventID := range e.PrevEventIDs() { // Look up what the state is after the backward extremity. This will either // come from the roomserver, if we know all the required events, or it will // come from a remote server via /state_ids if not. prevState, trustworthy, err := t.lookupStateAfterEvent(ctx, roomVersion, e.RoomID(), prevEventID) if err != nil { return nil, fmt.Errorf("t.lookupStateAfterEvent: %w", err) } // Append the state onto the collected state. We'll run this through the // state resolution next. states = append(states, &respState{trustworthy, prevState}) } // Now that we have collected all of the state from the prev_events, we'll // run the state through the appropriate state resolution algorithm for the // room if needed. This does a couple of things: // 1. Ensures that the state is deduplicated fully for each state-key tuple // 2. Ensures that we pick the latest events from both sets, in the case that // one of the prev_events is quite a bit older than the others resolvedState := &parsedRespState{} switch len(states) { case 0: extremityIsCreate := e.Type() == gomatrixserverlib.MRoomCreate && e.StateKeyEquals("") if !extremityIsCreate { // There are no previous states and this isn't the beginning of the // room - this is an error condition! return nil, fmt.Errorf("expected %d states but got %d", len(e.PrevEventIDs()), len(states)) } case 1: // There's only one previous state - if it's trustworthy (came from a // local state snapshot which will already have been through state res), // use it as-is. There's no point in resolving it again. Only trust a // trustworthy state snapshot if it actually contains some state for all // non-create events, otherwise we need to resolve what came from federation. isCreate := e.Type() == gomatrixserverlib.MRoomCreate && e.StateKeyEquals("") if states[0].trustworthy && (isCreate || len(states[0].StateEvents) > 0) { resolvedState = states[0].parsedRespState break } // Otherwise, if it isn't trustworthy (came from federation), run it through // state resolution anyway for safety, in case there are duplicates. fallthrough default: respStates := make([]*parsedRespState, len(states)) for i := range states { respStates[i] = states[i].parsedRespState } // There's more than one previous state - run them all through state res var err error t.roomsMu.Lock(e.RoomID()) resolvedState, err = t.resolveStatesAndCheck(ctx, roomVersion, respStates, e) t.roomsMu.Unlock(e.RoomID()) if err != nil { return nil, fmt.Errorf("t.resolveStatesAndCheck: %w", err) } } return resolvedState, nil } // lookupStateAfterEvent returns the room state after `eventID`, which is the state before eventID with the state of `eventID` (if it's a state event) // added into the mix. func (t *missingStateReq) lookupStateAfterEvent(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, roomID, eventID string) (*parsedRespState, bool, error) { // try doing all this locally before we resort to querying federation respState := t.lookupStateAfterEventLocally(ctx, roomID, eventID) if respState != nil { return respState, true, nil } respState, err := t.lookupStateBeforeEvent(ctx, roomVersion, roomID, eventID) if err != nil { return nil, false, fmt.Errorf("t.lookupStateBeforeEvent: %w", err) } // fetch the event we're missing and add it to the pile h, err := t.lookupEvent(ctx, roomVersion, roomID, eventID, false) switch err.(type) { case verifySigError: return respState, false, nil case nil: // do nothing default: return nil, false, fmt.Errorf("t.lookupEvent: %w", err) } h = t.cacheAndReturn(h) if h.StateKey() != nil { addedToState := false for i := range respState.StateEvents { se := respState.StateEvents[i] if se.Type() == h.Type() && se.StateKeyEquals(*h.StateKey()) { respState.StateEvents[i] = h addedToState = true break } } if !addedToState { respState.StateEvents = append(respState.StateEvents, h) } } return respState, false, nil } func (t *missingStateReq) cacheAndReturn(ev *gomatrixserverlib.Event) *gomatrixserverlib.Event { t.haveEventsMutex.Lock() defer t.haveEventsMutex.Unlock() if cached, exists := t.haveEvents[ev.EventID()]; exists { return cached } t.haveEvents[ev.EventID()] = ev return ev } func (t *missingStateReq) lookupStateAfterEventLocally(ctx context.Context, roomID, eventID string) *parsedRespState { var res parsedRespState roomInfo, err := t.db.RoomInfo(ctx, roomID) if err != nil { return nil } roomState := state.NewStateResolution(t.db, roomInfo) stateAtEvents, err := t.db.StateAtEventIDs(ctx, []string{eventID}) if err != nil { util.GetLogger(ctx).WithField("room_id", roomID).WithError(err).Warnf("failed to get state after %s locally", eventID) return nil } stateEntries, err := roomState.LoadCombinedStateAfterEvents(ctx, stateAtEvents) if err != nil { util.GetLogger(ctx).WithField("room_id", roomID).WithError(err).Warnf("failed to load combined state after %s locally", eventID) return nil } stateEventNIDs := make([]types.EventNID, 0, len(stateEntries)) for _, entry := range stateEntries { stateEventNIDs = append(stateEventNIDs, entry.EventNID) } stateEvents, err := t.db.Events(ctx, stateEventNIDs) if err != nil { util.GetLogger(ctx).WithField("room_id", roomID).WithError(err).Warnf("failed to load state events locally") return nil } res.StateEvents = make([]*gomatrixserverlib.Event, 0, len(stateEvents)) for _, ev := range stateEvents { // set the event from the haveEvents cache - this means we will share pointers with other prev_event branches for this // processEvent request, which is better for memory. res.StateEvents = append(res.StateEvents, t.cacheAndReturn(ev.Event)) t.hadEvent(ev.EventID()) } // encourage GC stateEvents, stateEventNIDs, stateEntries, stateAtEvents = nil, nil, nil, nil // nolint:ineffassign missingAuthEvents := map[string]bool{} res.AuthEvents = make([]*gomatrixserverlib.Event, 0, len(stateEvents)*3) for _, ev := range stateEvents { t.haveEventsMutex.Lock() for _, ae := range ev.AuthEventIDs() { if aev, ok := t.haveEvents[ae]; ok { res.AuthEvents = append(res.AuthEvents, aev) } else { missingAuthEvents[ae] = true } } t.haveEventsMutex.Unlock() } // QueryStateAfterEvents does not return the auth events, so fetch them now. We know the roomserver has them else it wouldn't // have stored the event. if len(missingAuthEvents) > 0 { var missingEventList []string for evID := range missingAuthEvents { missingEventList = append(missingEventList, evID) } util.GetLogger(ctx).WithField("count", len(missingEventList)).Debugf("Fetching missing auth events") events, err := t.db.EventsFromIDs(ctx, missingEventList) if err != nil { return nil } for i, ev := range events { res.AuthEvents = append(res.AuthEvents, t.cacheAndReturn(events[i].Event)) t.hadEvent(ev.EventID()) } } return &res } // lookuptStateBeforeEvent returns the room state before the event e, which is just /state_ids and/or /state depending on what // the server supports. func (t *missingStateReq) lookupStateBeforeEvent(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, roomID, eventID string) ( *parsedRespState, error) { // Attempt to fetch the missing state using /state_ids and /events return t.lookupMissingStateViaStateIDs(ctx, roomID, eventID, roomVersion) } func (t *missingStateReq) resolveStatesAndCheck(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, states []*parsedRespState, backwardsExtremity *gomatrixserverlib.Event) (*parsedRespState, error) { var authEventList []*gomatrixserverlib.Event var stateEventList []*gomatrixserverlib.Event for _, state := range states { authEventList = append(authEventList, state.AuthEvents...) stateEventList = append(stateEventList, state.StateEvents...) } resolvedStateEvents, err := gomatrixserverlib.ResolveConflicts(roomVersion, stateEventList, authEventList) if err != nil { return nil, err } // apply the current event retryAllowedState: if err = checkAllowedByState(backwardsExtremity, resolvedStateEvents); err != nil { switch missing := err.(type) { case gomatrixserverlib.MissingAuthEventError: h, err2 := t.lookupEvent(ctx, roomVersion, backwardsExtremity.RoomID(), missing.AuthEventID, true) switch err2.(type) { case verifySigError: return &parsedRespState{ AuthEvents: authEventList, StateEvents: resolvedStateEvents, }, nil case nil: // do nothing default: return nil, fmt.Errorf("missing auth event %s and failed to look it up: %w", missing.AuthEventID, err2) } util.GetLogger(ctx).Tracef("fetched event %s", missing.AuthEventID) resolvedStateEvents = append(resolvedStateEvents, h) goto retryAllowedState default: } return nil, err } return &parsedRespState{ AuthEvents: authEventList, StateEvents: resolvedStateEvents, }, nil } // get missing events for `e`. If `isGapFilled`=true then `newEvents` contains all the events to inject, // without `e`. If `isGapFilled=false` then `newEvents` contains the response to /get_missing_events func (t *missingStateReq) getMissingEvents(ctx context.Context, e *gomatrixserverlib.Event, roomVersion gomatrixserverlib.RoomVersion) (newEvents []*gomatrixserverlib.Event, isGapFilled, prevStateKnown bool, err error) { logger := util.GetLogger(ctx).WithField("event_id", e.EventID()).WithField("room_id", e.RoomID()) latest, _, _, err := t.db.LatestEventIDs(ctx, t.roomInfo.RoomNID) if err != nil { return nil, false, false, fmt.Errorf("t.DB.LatestEventIDs: %w", err) } latestEvents := make([]string, len(latest)) for i, ev := range latest { latestEvents[i] = ev.EventID t.hadEvent(ev.EventID) } var missingResp *gomatrixserverlib.RespMissingEvents for _, server := range t.servers { var m gomatrixserverlib.RespMissingEvents if m, err = t.federation.LookupMissingEvents(ctx, server, e.RoomID(), gomatrixserverlib.MissingEvents{ Limit: 20, // The latest event IDs that the sender already has. These are skipped when retrieving the previous events of latest_events. EarliestEvents: latestEvents, // The event IDs to retrieve the previous events for. LatestEvents: []string{e.EventID()}, }, roomVersion); err == nil { missingResp = &m break } else { logger.WithError(err).Warnf("%s pushed us an event but %q did not respond to /get_missing_events", t.origin, server) if errors.Is(err, context.DeadlineExceeded) { select { case <-ctx.Done(): // the parent request context timed out return nil, false, false, context.DeadlineExceeded default: // this request exceed its own timeout continue } } } } if missingResp == nil { logger.WithError(err).Warnf( "%s pushed us an event but %d server(s) couldn't give us details about prev_events via /get_missing_events - dropping this event until it can", t.origin, len(t.servers), ) return nil, false, false, missingPrevEventsError{ eventID: e.EventID(), err: err, } } // Make sure events from the missingResp are using the cache - missing events // will be added and duplicates will be removed. logger.Debugf("get_missing_events returned %d events", len(missingResp.Events)) missingEvents := make([]*gomatrixserverlib.Event, 0, len(missingResp.Events)) for _, ev := range missingResp.Events.UntrustedEvents(roomVersion) { missingEvents = append(missingEvents, t.cacheAndReturn(ev)) } // topologically sort and sanity check that we are making forward progress newEvents = gomatrixserverlib.ReverseTopologicalOrdering(missingEvents, gomatrixserverlib.TopologicalOrderByPrevEvents) shouldHaveSomeEventIDs := e.PrevEventIDs() hasPrevEvent := false Event: for _, pe := range shouldHaveSomeEventIDs { for _, ev := range newEvents { if ev.EventID() == pe { hasPrevEvent = true break Event } } } if !hasPrevEvent { err = fmt.Errorf("called /get_missing_events but server %s didn't return any prev_events with IDs %v", t.origin, shouldHaveSomeEventIDs) logger.WithError(err).Warnf( "%s pushed us an event but couldn't give us details about prev_events via /get_missing_events - dropping this event until it can", t.origin, ) return nil, false, false, missingPrevEventsError{ eventID: e.EventID(), err: err, } } if len(newEvents) == 0 { return nil, false, false, nil // TODO: error instead? } earliestNewEvent := newEvents[0] // If we retrieved back to the beginning of the room then there's nothing else // to do - we closed the gap. if len(earliestNewEvent.PrevEventIDs()) == 0 && earliestNewEvent.Type() == gomatrixserverlib.MRoomCreate && earliestNewEvent.StateKeyEquals("") { return newEvents, true, t.isPrevStateKnown(ctx, e), nil } // If our backward extremity was not a known event to us then we obviously didn't // close the gap. if state, err := t.db.StateAtEventIDs(ctx, []string{earliestNewEvent.EventID()}); err != nil || len(state) == 0 && state[0].BeforeStateSnapshotNID == 0 { return newEvents, false, false, nil } // At this point we are satisfied that we know the state both at the earliest // retrieved event and at the prev events of the new event. return newEvents, true, t.isPrevStateKnown(ctx, e), nil } func (t *missingStateReq) isPrevStateKnown(ctx context.Context, e *gomatrixserverlib.Event) bool { expected := len(e.PrevEventIDs()) state, err := t.db.StateAtEventIDs(ctx, e.PrevEventIDs()) if err != nil || len(state) != expected { // We didn't get as many state snapshots as we expected, or there was an error, // so we haven't completely solved the problem for the new event. return false } // Check to see if we have a populated state snapshot for all of the prev events. for _, stateAtEvent := range state { if stateAtEvent.BeforeStateSnapshotNID == 0 { // One of the prev events still has unknown state, so we haven't really // solved the problem. return false } } return true } func (t *missingStateReq) lookupMissingStateViaState( ctx context.Context, roomID, eventID string, roomVersion gomatrixserverlib.RoomVersion, ) (respState *parsedRespState, err error) { state, err := t.federation.LookupState(ctx, t.origin, roomID, eventID, roomVersion) if err != nil { return nil, err } // Check that the returned state is valid. authEvents, stateEvents, err := state.Check(ctx, roomVersion, t.keys, nil) if err != nil { return nil, err } parsedState := &parsedRespState{ AuthEvents: authEvents, StateEvents: stateEvents, } // Cache the results of this state lookup and deduplicate anything we already // have in the cache, freeing up memory. // We load these as trusted as we called state.Check before which loaded them as untrusted. for i, evJSON := range state.AuthEvents { ev, _ := gomatrixserverlib.NewEventFromTrustedJSON(evJSON, false, roomVersion) parsedState.AuthEvents[i] = t.cacheAndReturn(ev) } for i, evJSON := range state.StateEvents { ev, _ := gomatrixserverlib.NewEventFromTrustedJSON(evJSON, false, roomVersion) parsedState.StateEvents[i] = t.cacheAndReturn(ev) } return parsedState, nil } func (t *missingStateReq) lookupMissingStateViaStateIDs(ctx context.Context, roomID, eventID string, roomVersion gomatrixserverlib.RoomVersion) ( *parsedRespState, error) { util.GetLogger(ctx).WithField("room_id", roomID).Infof("lookupMissingStateViaStateIDs %s", eventID) // fetch the state event IDs at the time of the event stateIDs, err := t.federation.LookupStateIDs(ctx, t.origin, roomID, eventID) if err != nil { return nil, err } // work out which auth/state IDs are missing wantIDs := append(stateIDs.StateEventIDs, stateIDs.AuthEventIDs...) missing := make(map[string]bool) var missingEventList []string t.haveEventsMutex.Lock() for _, sid := range wantIDs { if _, ok := t.haveEvents[sid]; !ok { if !missing[sid] { missing[sid] = true missingEventList = append(missingEventList, sid) } } } t.haveEventsMutex.Unlock() events, err := t.db.EventsFromIDs(ctx, missingEventList) if err != nil { return nil, fmt.Errorf("t.db.EventsFromIDs: %w", err) } for i, ev := range events { events[i].Event = t.cacheAndReturn(events[i].Event) t.hadEvent(ev.EventID()) evID := events[i].EventID() if missing[evID] { delete(missing, evID) } } // encourage GC events = nil // nolint:ineffassign concurrentRequests := 8 missingCount := len(missing) util.GetLogger(ctx).WithField("room_id", roomID).WithField("event_id", eventID).Debugf("lookupMissingStateViaStateIDs missing %d/%d events", missingCount, len(wantIDs)) // If over 50% of the auth/state events from /state_ids are missing // then we'll just call /state instead, otherwise we'll just end up // hammering the remote side with /event requests unnecessarily. if missingCount > concurrentRequests && missingCount > len(wantIDs)/2 { util.GetLogger(ctx).WithFields(logrus.Fields{ "missing": missingCount, "event_id": eventID, "room_id": roomID, "total_state": len(stateIDs.StateEventIDs), "total_auth_events": len(stateIDs.AuthEventIDs), }).Debug("Fetching all state at event") return t.lookupMissingStateViaState(ctx, roomID, eventID, roomVersion) } if missingCount > 0 { util.GetLogger(ctx).WithFields(logrus.Fields{ "missing": missingCount, "event_id": eventID, "room_id": roomID, "total_state": len(stateIDs.StateEventIDs), "total_auth_events": len(stateIDs.AuthEventIDs), "concurrent_requests": concurrentRequests, }).Debug("Fetching missing state at event") // Create a queue containing all of the missing event IDs that we want // to retrieve. pending := make(chan string, missingCount) for missingEventID := range missing { pending <- missingEventID } close(pending) // Define how many workers we should start to do this. if missingCount < concurrentRequests { concurrentRequests = missingCount } // Create the wait group. var fetchgroup sync.WaitGroup fetchgroup.Add(concurrentRequests) // This is the only place where we'll write to t.haveEvents from // multiple goroutines, and everywhere else is blocked on this // synchronous function anyway. var haveEventsMutex sync.Mutex // Define what we'll do in order to fetch the missing event ID. fetch := func(missingEventID string) { var h *gomatrixserverlib.Event h, err = t.lookupEvent(ctx, roomVersion, roomID, missingEventID, false) switch err.(type) { case verifySigError: return case nil: break default: util.GetLogger(ctx).WithFields(logrus.Fields{ "event_id": missingEventID, "room_id": roomID, }).Warn("Failed to fetch missing event") return } haveEventsMutex.Lock() t.cacheAndReturn(h) haveEventsMutex.Unlock() } // Create the worker. worker := func(ch <-chan string) { defer fetchgroup.Done() for missingEventID := range ch { fetch(missingEventID) } } // Start the workers. for i := 0; i < concurrentRequests; i++ { go worker(pending) } // Wait for the workers to finish. fetchgroup.Wait() } resp, err := t.createRespStateFromStateIDs(stateIDs) return resp, err } func (t *missingStateReq) createRespStateFromStateIDs( stateIDs gomatrixserverlib.RespStateIDs, ) (*parsedRespState, error) { // nolint:unparam t.haveEventsMutex.Lock() defer t.haveEventsMutex.Unlock() // create a RespState response using the response to /state_ids as a guide respState := parsedRespState{} for i := range stateIDs.StateEventIDs { ev, ok := t.haveEvents[stateIDs.StateEventIDs[i]] if !ok { logrus.Tracef("Missing state event in createRespStateFromStateIDs: %s", stateIDs.StateEventIDs[i]) continue } respState.StateEvents = append(respState.StateEvents, ev) } for i := range stateIDs.AuthEventIDs { ev, ok := t.haveEvents[stateIDs.AuthEventIDs[i]] if !ok { logrus.Tracef("Missing auth event in createRespStateFromStateIDs: %s", stateIDs.AuthEventIDs[i]) continue } respState.AuthEvents = append(respState.AuthEvents, ev) } // We purposefully do not do auth checks on the returned events, as they will still // be processed in the exact same way, just as a 'rejected' event // TODO: Add a field to HeaderedEvent to indicate if the event is rejected. return &respState, nil } func (t *missingStateReq) lookupEvent(ctx context.Context, roomVersion gomatrixserverlib.RoomVersion, _, missingEventID string, localFirst bool) (*gomatrixserverlib.Event, error) { if localFirst { // fetch from the roomserver events, err := t.db.EventsFromIDs(ctx, []string{missingEventID}) if err != nil { util.GetLogger(ctx).Warnf("Failed to query roomserver for missing event %s: %s - falling back to remote", missingEventID, err) } else if len(events) == 1 { return events[0].Event, nil } } var event *gomatrixserverlib.Event found := false for _, serverName := range t.servers { reqctx, cancel := context.WithTimeout(ctx, time.Second*30) defer cancel() txn, err := t.federation.GetEvent(reqctx, serverName, missingEventID) if err != nil || len(txn.PDUs) == 0 { util.GetLogger(ctx).WithError(err).WithField("event_id", missingEventID).Warn("Failed to get missing /event for event ID") if errors.Is(err, context.DeadlineExceeded) { select { case <-reqctx.Done(): // this server took too long continue case <-ctx.Done(): // the input request timed out return nil, context.DeadlineExceeded } } continue } event, err = gomatrixserverlib.NewEventFromUntrustedJSON(txn.PDUs[0], roomVersion) if err != nil { util.GetLogger(ctx).WithError(err).WithField("event_id", missingEventID).Warnf("Failed to parse event JSON of event returned from /event") continue } found = true break } if !found { util.GetLogger(ctx).WithField("event_id", missingEventID).Warnf("Failed to get missing /event for event ID from %d server(s)", len(t.servers)) return nil, fmt.Errorf("wasn't able to find event via %d server(s)", len(t.servers)) } if err := event.VerifyEventSignatures(ctx, t.keys); err != nil { util.GetLogger(ctx).WithError(err).Warnf("Couldn't validate signature of event %q from /event", event.EventID()) return nil, verifySigError{event.EventID(), err} } return t.cacheAndReturn(event), nil } func checkAllowedByState(e *gomatrixserverlib.Event, stateEvents []*gomatrixserverlib.Event) error { authUsingState := gomatrixserverlib.NewAuthEvents(nil) for i := range stateEvents { err := authUsingState.AddEvent(stateEvents[i]) if err != nil { return err } } return gomatrixserverlib.Allowed(e, &authUsingState) } func (t *missingStateReq) hadEvent(eventID string) { t.hadEventsMutex.Lock() defer t.hadEventsMutex.Unlock() t.hadEvents[eventID] = true } type verifySigError struct { eventID string err error } type missingPrevEventsError struct { eventID string err error } func (e verifySigError) Error() string { return fmt.Sprintf("unable to verify signature of event %q: %s", e.eventID, e.err) } func (e missingPrevEventsError) Error() string { return fmt.Sprintf("unable to get prev_events for event %q: %s", e.eventID, e.err) }