From 43cdba9a69674899a5900aee976ebc7add286914 Mon Sep 17 00:00:00 2001
From: Neil Alexander <neilalexander@users.noreply.github.com>
Date: Tue, 29 Sep 2020 14:07:59 +0100
Subject: [PATCH] Ignore depth in federation API (#1451)

---
 federationapi/routing/missingevents.go | 10 +++++-----
 federationapi/routing/send.go          |  9 +--------
 2 files changed, 6 insertions(+), 13 deletions(-)

diff --git a/federationapi/routing/missingevents.go b/federationapi/routing/missingevents.go
index f93e0eb4..5118b34e 100644
--- a/federationapi/routing/missingevents.go
+++ b/federationapi/routing/missingevents.go
@@ -26,7 +26,7 @@ type getMissingEventRequest struct {
 	EarliestEvents []string `json:"earliest_events"`
 	LatestEvents   []string `json:"latest_events"`
 	Limit          int      `json:"limit"`
-	MinDepth       int64    `json:"min_depth"`
+	MinDepth       int64    `json:"min_depth"` // not used
 }
 
 // GetMissingEvents returns missing events between earliest_events & latest_events.
@@ -59,7 +59,7 @@ func GetMissingEvents(
 		return jsonerror.InternalServerError()
 	}
 
-	eventsResponse.Events = filterEvents(eventsResponse.Events, gme.MinDepth, roomID)
+	eventsResponse.Events = filterEvents(eventsResponse.Events, roomID)
 
 	resp := gomatrixserverlib.RespMissingEvents{
 		Events: gomatrixserverlib.UnwrapEventHeaders(eventsResponse.Events),
@@ -71,13 +71,13 @@ func GetMissingEvents(
 	}
 }
 
-// filterEvents returns only those events with matching roomID and having depth greater than minDepth
+// filterEvents returns only those events with matching roomID
 func filterEvents(
-	events []gomatrixserverlib.HeaderedEvent, minDepth int64, roomID string,
+	events []gomatrixserverlib.HeaderedEvent, roomID string,
 ) []gomatrixserverlib.HeaderedEvent {
 	ref := events[:0]
 	for _, ev := range events {
-		if ev.Depth() >= minDepth && ev.RoomID() == roomID {
+		if ev.RoomID() == roomID {
 			ref = append(ref, ev)
 		}
 	}
diff --git a/federationapi/routing/send.go b/federationapi/routing/send.go
index 4a30f8d7..f8b8bcd6 100644
--- a/federationapi/routing/send.go
+++ b/federationapi/routing/send.go
@@ -656,7 +656,7 @@ retryAllowedState:
 // getMissingEvents returns a nil backwardsExtremity if missing events were fetched and handled, else returns the new backwards extremity which we should
 // begin from. Returns an error only if we should terminate the transaction which initiated /get_missing_events
 // This function recursively calls txnReq.processEvent with the missing events, which will be processed before this function returns.
-// This means that we may recursively call this function, as we spider back up prev_events to the min depth.
+// This means that we may recursively call this function, as we spider back up prev_events.
 // nolint:gocyclo
 func (t *txnReq) getMissingEvents(ctx context.Context, e gomatrixserverlib.Event, roomVersion gomatrixserverlib.RoomVersion, isInboundTxn bool) (backwardsExtremity *gomatrixserverlib.Event, err error) {
 	if !isInboundTxn {
@@ -679,11 +679,6 @@ func (t *txnReq) getMissingEvents(ctx context.Context, e gomatrixserverlib.Event
 	for i := range res.LatestEvents {
 		latestEvents[i] = res.LatestEvents[i].EventID
 	}
-	// this server just sent us an event for which we do not know its prev_events - ask that server for those prev_events.
-	minDepth := int(res.Depth) - 20
-	if minDepth < 0 {
-		minDepth = 0
-	}
 
 	servers := []gomatrixserverlib.ServerName{t.Origin}
 	serverReq := &api.QueryServerJoinedToRoomRequest{
@@ -700,8 +695,6 @@ func (t *txnReq) getMissingEvents(ctx context.Context, e gomatrixserverlib.Event
 		var m gomatrixserverlib.RespMissingEvents
 		if m, err = t.federation.LookupMissingEvents(ctx, server, e.RoomID(), gomatrixserverlib.MissingEvents{
 			Limit: 20,
-			// synapse uses the min depth they've ever seen in that room
-			MinDepth: minDepth,
 			// 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.