Attempt to find missing auth events over federation (this shouldn't happen but I am guessing there is a synapse bug involved where we don't get all of the auth events)

clientapi/routing/joinroom.go

@@ -365,9 +365,47 @@ func (r joinRoomReq) joinRoomUsingServer(roomID string, server gomatrixserverlib
 		return nil, fmt.Errorf("r.federation.SendJoin: %w", err)
 	}
 
+	// A list of events that we have retried, if they were not included in
+	// the auth events supplied in the send_join.
+	retries := map[string]bool{}
+
+retryCheck:
+	fmt.Println("STATE EVENTS:")
+	for _, e := range respSendJoin.StateEvents {
+		fmt.Println("*", e.EventID())
+	}
+	fmt.Println("AUTH EVENTS:")
+	for _, e := range respSendJoin.AuthEvents {
+		fmt.Println("*", e.EventID())
+	}
 	if err = respSendJoin.Check(r.req.Context(), r.keyRing, event); err != nil {
+		switch e := err.(type) {
+		case gomatrixserverlib.MissingAuthEventError:
+			// Check that we haven't already retried for this event, prevents
+			// us from ending up in endless loops
+			if _, ok := retries[e.AuthEventID]; !ok {
+				// Ask the server that we're talking to right now for the event
+				tx, txerr := r.federation.GetEvent(r.req.Context(), server, e.AuthEventID)
+				if txerr != nil {
+					return nil, fmt.Errorf("r.federation.GetEvent: %w", txerr)
+				}
+				// For each event returned, add it to the auth events.
+				for _, pdu := range tx.PDUs {
+					ev, everr := gomatrixserverlib.NewEventFromUntrustedJSON(pdu, respMakeJoin.RoomVersion)
+					if everr != nil {
+						return nil, fmt.Errorf("gomatrixserverlib.NewEventFromUntrustedJSON: %w", everr)
+					}
+					respSendJoin.AuthEvents = append(respSendJoin.AuthEvents, ev)
+				}
+				// Mark the event as retried and then give the check another go.
+				retries[e.AuthEventID] = true
+				goto retryCheck
+			}
+			return nil, fmt.Errorf("respSendJoin (after retries): %w", e)
+		default:
 			return nil, fmt.Errorf("respSendJoin: %w", err)
 		}
+	}
 
 	if err = r.producer.SendEventWithState(
 		r.req.Context(),

go.mod

@@ -17,7 +17,7 @@ require (
 	github.com/matrix-org/go-http-js-libp2p v0.0.0-20200318135427-31631a9ef51f
 	github.com/matrix-org/go-sqlite3-js v0.0.0-20200325174927-327088cdef10
 	github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26
-	github.com/matrix-org/gomatrixserverlib v0.0.0-20200417121920-a7a5d963b596
+	github.com/matrix-org/gomatrixserverlib v0.0.0-20200417154207-c38787065567
 	github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1
 	github.com/matrix-org/util v0.0.0-20190711121626-527ce5ddefc7
 	github.com/mattn/go-sqlite3 v2.0.3+incompatible

go.sum

@@ -364,8 +364,8 @@ github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26 h1:Hr3zjRsq2bh
 github.com/matrix-org/gomatrix v0.0.0-20190528120928-7df988a63f26/go.mod h1:3fxX6gUjWyI/2Bt7J1OLhpCzOfO/bB3AiX0cJtEKud0=
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200124100636-0c2ec91d1df5 h1:kmRjpmFOenVpOaV/DRlo9p6z/IbOKlUC+hhKsAAh8Qg=
 github.com/matrix-org/gomatrixserverlib v0.0.0-20200124100636-0c2ec91d1df5/go.mod h1:FsKa2pWE/bpQql9H7U4boOPXFoJX/QcqaZZ6ijLkaZI=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20200417121920-a7a5d963b596 h1:+FBAOVJgB4BWbiBOYM96A1SqI+rUHVPRc0NlyTmp2oI=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200417154207-c38787065567 h1:IjnhrozHJ4yzj52GLI98O3GnVL7BBxR0kr4yS93yfQw=
-github.com/matrix-org/gomatrixserverlib v0.0.0-20200417121920-a7a5d963b596/go.mod h1:FsKa2pWE/bpQql9H7U4boOPXFoJX/QcqaZZ6ijLkaZI=
+github.com/matrix-org/gomatrixserverlib v0.0.0-20200417154207-c38787065567/go.mod h1:FsKa2pWE/bpQql9H7U4boOPXFoJX/QcqaZZ6ijLkaZI=
 github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1 h1:osLoFdOy+ChQqVUn2PeTDETFftVkl4w9t/OW18g3lnk=
 github.com/matrix-org/naffka v0.0.0-20200127221512-0716baaabaf1/go.mod h1:cXoYQIENbdWIQHt1SyCo6Bl3C3raHwJ0wgVrXHSqf+A=
 github.com/matrix-org/util v0.0.0-20171127121716-2e2df66af2f5 h1:W7l5CP4V7wPyPb4tYE11dbmeAOwtFQBTW0rf4OonOS8=