Initial Store & Forward Implementation (#2917)

This adds store & forward relays into dendrite for p2p.
A few things have changed:
- new relay api serves new http endpoints for s&f federation
- updated outbound federation queueing which will attempt to forward
using s&f if appropriate
- database entries to track s&f relays for other nodes

relayapi/routing/sendrelay.go

@@ -0,0 +1,77 @@
+// Copyright 2022 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package routing
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/matrix-org/dendrite/clientapi/jsonerror"
+	"github.com/matrix-org/dendrite/relayapi/api"
+	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
+	"github.com/sirupsen/logrus"
+)
+
+// SendTransactionToRelay implements PUT /_matrix/federation/v1/relay_txn/{txnID}/{userID}
+// This endpoint can be extracted into a separate relay server service.
+func SendTransactionToRelay(
+	httpReq *http.Request,
+	fedReq *gomatrixserverlib.FederationRequest,
+	relayAPI api.RelayInternalAPI,
+	txnID gomatrixserverlib.TransactionID,
+	userID gomatrixserverlib.UserID,
+) util.JSONResponse {
+	var txnEvents struct {
+		PDUs []json.RawMessage       `json:"pdus"`
+		EDUs []gomatrixserverlib.EDU `json:"edus"`
+	}
+
+	if err := json.Unmarshal(fedReq.Content(), &txnEvents); err != nil {
+		logrus.Info("The request body could not be decoded into valid JSON." + err.Error())
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.NotJSON("The request body could not be decoded into valid JSON." + err.Error()),
+		}
+	}
+
+	// Transactions are limited in size; they can have at most 50 PDUs and 100 EDUs.
+	// https://matrix.org/docs/spec/server_server/latest#transactions
+	if len(txnEvents.PDUs) > 50 || len(txnEvents.EDUs) > 100 {
+		return util.JSONResponse{
+			Code: http.StatusBadRequest,
+			JSON: jsonerror.BadJSON("max 50 pdus / 100 edus"),
+		}
+	}
+
+	t := gomatrixserverlib.Transaction{}
+	t.PDUs = txnEvents.PDUs
+	t.EDUs = txnEvents.EDUs
+	t.Origin = fedReq.Origin()
+	t.TransactionID = txnID
+	t.Destination = userID.Domain()
+
+	util.GetLogger(httpReq.Context()).Warnf("Received transaction %q from %q containing %d PDUs, %d EDUs", txnID, fedReq.Origin(), len(t.PDUs), len(t.EDUs))
+
+	err := relayAPI.PerformStoreTransaction(httpReq.Context(), t, userID)
+	if err != nil {
+		return util.JSONResponse{
+			Code: http.StatusInternalServerError,
+			JSON: jsonerror.BadJSON("could not store the transaction for forwarding"),
+		}
+	}
+
+	return util.JSONResponse{Code: 200}
+}