MSC2836 threading: part 2 (#1596)

* Update GMSL

* Add MSC2836EventRelationships to fedsender

* Call MSC2836EventRelationships in reqCtx

* auth remote servers

* Extract room ID and servers from previous events; refactor a bit

* initial cut of federated threading

* Use the right client/fed struct in the response

* Add QueryAuthChain for use with MSC2836

* Add auth chain to federated response

* Fix pointers

* under CI: more logging and enable mscs, nil fix

* Handle direction: up

* Actually send message events to the roomserver..

* Add children and children_hash to unsigned, with tests

* Add logic for exploring threads and tracking children; missing storage functions

* Implement storage functions for children

* Add fetchUnknownEvent

* Do federated hits for include_children if we have unexplored children

* Use /ev_rel rather than /event as the former includes child metadata

* Remove cross-room threading impl

* Enable MSC2836 in the p2p demo

* Namespace mscs db

* Enable msc2836 for ygg

Co-authored-by: Neil Alexander <neilalexander@users.noreply.github.com>

4 files changed, 80 insertions, 9 deletions

diff --git a/federationsender/api/api.go b/federationsender/api/api.go
index a4d15f1f..e4d176b1 100644
--- a/federationsender/api/api.go
+++ b/federationsender/api/api.go
@@ -21,6 +21,7 @@ type FederationClient interface {
 	QueryKeys(ctx context.Context, s gomatrixserverlib.ServerName, keys map[string][]string) (res gomatrixserverlib.RespQueryKeys, err error)
 	GetEvent(ctx context.Context, s gomatrixserverlib.ServerName, eventID string) (res gomatrixserverlib.Transaction, err error)
 	GetServerKeys(ctx context.Context, matrixServer gomatrixserverlib.ServerName) (gomatrixserverlib.ServerKeys, error)
+	MSC2836EventRelationships(ctx context.Context, dst gomatrixserverlib.ServerName, r gomatrixserverlib.MSC2836EventRelationshipsRequest, roomVersion gomatrixserverlib.RoomVersion) (res gomatrixserverlib.MSC2836EventRelationshipsResponse, err error)
 	LookupServerKeys(ctx context.Context, s gomatrixserverlib.ServerName, keyRequests map[gomatrixserverlib.PublicKeyLookupRequest]gomatrixserverlib.Timestamp) ([]gomatrixserverlib.ServerKeys, error)
 }
 
diff --git a/federationsender/internal/api.go b/federationsender/internal/api.go
index a14cf3ca..407e7ffe 100644
--- a/federationsender/internal/api.go
+++ b/federationsender/internal/api.go
@@ -229,3 +229,18 @@ func (a *FederationSenderInternalAPI) LookupServerKeys(
 	}
 	return ires.([]gomatrixserverlib.ServerKeys), nil
 }
+
+func (a *FederationSenderInternalAPI) MSC2836EventRelationships(
+	ctx context.Context, s gomatrixserverlib.ServerName, r gomatrixserverlib.MSC2836EventRelationshipsRequest,
+	roomVersion gomatrixserverlib.RoomVersion,
+) (res gomatrixserverlib.MSC2836EventRelationshipsResponse, err error) {
+	ctx, cancel := context.WithTimeout(ctx, time.Minute)
+	defer cancel()
+	ires, err := a.doRequest(s, func() (interface{}, error) {
+		return a.federation.MSC2836EventRelationships(ctx, s, r, roomVersion)
+	})
+	if err != nil {
+		return res, err
+	}
+	return ires.(gomatrixserverlib.MSC2836EventRelationshipsResponse), nil
+}
diff --git a/federationsender/inthttp/client.go b/federationsender/inthttp/client.go
index e0783ee1..fe98ff33 100644
--- a/federationsender/inthttp/client.go
+++ b/federationsender/inthttp/client.go
@@ -23,15 +23,16 @@ const (
 	FederationSenderPerformServersAlivePath           = "/federationsender/performServersAlive"
 	FederationSenderPerformBroadcastEDUPath           = "/federationsender/performBroadcastEDU"
 
-	FederationSenderGetUserDevicesPath   = "/federationsender/client/getUserDevices"
-	FederationSenderClaimKeysPath        = "/federationsender/client/claimKeys"
-	FederationSenderQueryKeysPath        = "/federationsender/client/queryKeys"
-	FederationSenderBackfillPath         = "/federationsender/client/backfill"
-	FederationSenderLookupStatePath      = "/federationsender/client/lookupState"
-	FederationSenderLookupStateIDsPath   = "/federationsender/client/lookupStateIDs"
-	FederationSenderGetEventPath         = "/federationsender/client/getEvent"
-	FederationSenderGetServerKeysPath    = "/federationsender/client/getServerKeys"
-	FederationSenderLookupServerKeysPath = "/federationsender/client/lookupServerKeys"
+	FederationSenderGetUserDevicesPath     = "/federationsender/client/getUserDevices"
+	FederationSenderClaimKeysPath          = "/federationsender/client/claimKeys"
+	FederationSenderQueryKeysPath          = "/federationsender/client/queryKeys"
+	FederationSenderBackfillPath           = "/federationsender/client/backfill"
+	FederationSenderLookupStatePath        = "/federationsender/client/lookupState"
+	FederationSenderLookupStateIDsPath     = "/federationsender/client/lookupStateIDs"
+	FederationSenderGetEventPath           = "/federationsender/client/getEvent"
+	FederationSenderGetServerKeysPath      = "/federationsender/client/getServerKeys"
+	FederationSenderLookupServerKeysPath   = "/federationsender/client/lookupServerKeys"
+	FederationSenderEventRelationshipsPath = "/federationsender/client/msc2836eventRelationships"
 )
 
 // NewFederationSenderClient creates a FederationSenderInternalAPI implemented by talking to a HTTP POST API.
@@ -416,3 +417,35 @@ func (h *httpFederationSenderInternalAPI) LookupServerKeys(
 	}
 	return response.ServerKeys, nil
 }
+
+type eventRelationships struct {
+	S       gomatrixserverlib.ServerName
+	Req     gomatrixserverlib.MSC2836EventRelationshipsRequest
+	RoomVer gomatrixserverlib.RoomVersion
+	Res     gomatrixserverlib.MSC2836EventRelationshipsResponse
+	Err     *api.FederationClientError
+}
+
+func (h *httpFederationSenderInternalAPI) MSC2836EventRelationships(
+	ctx context.Context, s gomatrixserverlib.ServerName, r gomatrixserverlib.MSC2836EventRelationshipsRequest,
+	roomVersion gomatrixserverlib.RoomVersion,
+) (res gomatrixserverlib.MSC2836EventRelationshipsResponse, err error) {
+	span, ctx := opentracing.StartSpanFromContext(ctx, "MSC2836EventRelationships")
+	defer span.Finish()
+
+	request := eventRelationships{
+		S:       s,
+		Req:     r,
+		RoomVer: roomVersion,
+	}
+	var response eventRelationships
+	apiURL := h.federationSenderURL + FederationSenderEventRelationshipsPath
+	err = httputil.PostJSON(ctx, span, h.httpClient, apiURL, &request, &response)
+	if err != nil {
+		return res, err
+	}
+	if response.Err != nil {
+		return res, response.Err
+	}
+	return response.Res, nil
+}
diff --git a/federationsender/inthttp/server.go b/federationsender/inthttp/server.go
index 53e1183e..293fb420 100644
--- a/federationsender/inthttp/server.go
+++ b/federationsender/inthttp/server.go
@@ -307,4 +307,26 @@ func AddRoutes(intAPI api.FederationSenderInternalAPI, internalAPIMux *mux.Route
 			return util.JSONResponse{Code: http.StatusOK, JSON: request}
 		}),
 	)
+	internalAPIMux.Handle(
+		FederationSenderEventRelationshipsPath,
+		httputil.MakeInternalAPI("MSC2836EventRelationships", func(req *http.Request) util.JSONResponse {
+			var request eventRelationships
+			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
+				return util.MessageResponse(http.StatusBadRequest, err.Error())
+			}
+			res, err := intAPI.MSC2836EventRelationships(req.Context(), request.S, request.Req, request.RoomVer)
+			if err != nil {
+				ferr, ok := err.(*api.FederationClientError)
+				if ok {
+					request.Err = ferr
+				} else {
+					request.Err = &api.FederationClientError{
+						Err: err.Error(),
+					}
+				}
+			}
+			request.Res = res
+			return util.JSONResponse{Code: http.StatusOK, JSON: request}
+		}),
+	)
 }