dendrite/setup/mscs/msc2836/msc2836.go

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// Copyright 2020 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 msc2836 'Threading' implements https://github.com/matrix-org/matrix-doc/pull/2836
package msc2836
import (
"bytes"
"context"
"crypto/sha256"
"encoding/json"
"fmt"
"io"
"net/http"
"sort"
"strings"
"time"
"github.com/matrix-org/dendrite/clientapi/jsonerror"
fs "github.com/matrix-org/dendrite/federationsender/api"
"github.com/matrix-org/dendrite/internal/hooks"
"github.com/matrix-org/dendrite/internal/httputil"
roomserver "github.com/matrix-org/dendrite/roomserver/api"
"github.com/matrix-org/dendrite/setup"
userapi "github.com/matrix-org/dendrite/userapi/api"
"github.com/matrix-org/gomatrixserverlib"
"github.com/matrix-org/util"
)
const (
constRelType = "m.reference"
)
type EventRelationshipRequest struct {
EventID string `json:"event_id"`
RoomID string `json:"room_id"`
MaxDepth int `json:"max_depth"`
MaxBreadth int `json:"max_breadth"`
Limit int `json:"limit"`
DepthFirst bool `json:"depth_first"`
RecentFirst bool `json:"recent_first"`
IncludeParent bool `json:"include_parent"`
IncludeChildren bool `json:"include_children"`
Direction string `json:"direction"`
Batch string `json:"batch"`
}
func NewEventRelationshipRequest(body io.Reader) (*EventRelationshipRequest, error) {
var relation EventRelationshipRequest
relation.Defaults()
if err := json.NewDecoder(body).Decode(&relation); err != nil {
return nil, err
}
return &relation, nil
}
func (r *EventRelationshipRequest) Defaults() {
r.Limit = 100
r.MaxBreadth = 10
r.MaxDepth = 3
r.DepthFirst = false
r.RecentFirst = true
r.IncludeParent = false
r.IncludeChildren = false
r.Direction = "down"
}
type EventRelationshipResponse struct {
Events []gomatrixserverlib.ClientEvent `json:"events"`
NextBatch string `json:"next_batch"`
Limited bool `json:"limited"`
}
func toClientResponse(res *gomatrixserverlib.MSC2836EventRelationshipsResponse) *EventRelationshipResponse {
out := &EventRelationshipResponse{
Events: gomatrixserverlib.ToClientEvents(res.Events, gomatrixserverlib.FormatAll),
Limited: res.Limited,
NextBatch: res.NextBatch,
}
return out
}
// Enable this MSC
func Enable(
base *setup.BaseDendrite, rsAPI roomserver.RoomserverInternalAPI, fsAPI fs.FederationSenderInternalAPI,
userAPI userapi.UserInternalAPI, keyRing gomatrixserverlib.JSONVerifier,
) error {
db, err := NewDatabase(&base.Cfg.MSCs.Database)
if err != nil {
return fmt.Errorf("Cannot enable MSC2836: %w", err)
}
hooks.Enable()
hooks.Attach(hooks.KindNewEventPersisted, func(headeredEvent interface{}) {
he := headeredEvent.(*gomatrixserverlib.HeaderedEvent)
hookErr := db.StoreRelation(context.Background(), he)
if hookErr != nil {
util.GetLogger(context.Background()).WithError(hookErr).WithField("event_id", he.EventID()).Error(
"failed to StoreRelation",
)
}
// we need to update child metadata here as well as after doing remote /event_relationships requests
// so we catch child metadata originating from /send transactions
hookErr = db.UpdateChildMetadata(context.Background(), he)
if hookErr != nil {
util.GetLogger(context.Background()).WithError(err).WithField("event_id", he.EventID()).Warn(
"failed to update child metadata for event",
)
}
})
base.PublicClientAPIMux.Handle("/unstable/event_relationships",
httputil.MakeAuthAPI("eventRelationships", userAPI, eventRelationshipHandler(db, rsAPI, fsAPI)),
).Methods(http.MethodPost, http.MethodOptions)
base.PublicFederationAPIMux.Handle("/unstable/event_relationships", httputil.MakeExternalAPI(
"msc2836_event_relationships", func(req *http.Request) util.JSONResponse {
fedReq, errResp := gomatrixserverlib.VerifyHTTPRequest(
req, time.Now(), base.Cfg.Global.ServerName, keyRing,
)
if fedReq == nil {
return errResp
}
return federatedEventRelationship(req.Context(), fedReq, db, rsAPI, fsAPI)
},
)).Methods(http.MethodPost, http.MethodOptions)
return nil
}
type reqCtx struct {
ctx context.Context
rsAPI roomserver.RoomserverInternalAPI
db Database
req *EventRelationshipRequest
userID string
roomVersion gomatrixserverlib.RoomVersion
// federated request args
isFederatedRequest bool
serverName gomatrixserverlib.ServerName
fsAPI fs.FederationSenderInternalAPI
}
func eventRelationshipHandler(db Database, rsAPI roomserver.RoomserverInternalAPI, fsAPI fs.FederationSenderInternalAPI) func(*http.Request, *userapi.Device) util.JSONResponse {
return func(req *http.Request, device *userapi.Device) util.JSONResponse {
relation, err := NewEventRelationshipRequest(req.Body)
if err != nil {
util.GetLogger(req.Context()).WithError(err).Error("failed to decode HTTP request as JSON")
return util.JSONResponse{
Code: 400,
JSON: jsonerror.BadJSON(fmt.Sprintf("invalid json: %s", err)),
}
}
rc := reqCtx{
ctx: req.Context(),
req: relation,
userID: device.UserID,
rsAPI: rsAPI,
fsAPI: fsAPI,
isFederatedRequest: false,
db: db,
}
res, resErr := rc.process()
if resErr != nil {
return *resErr
}
return util.JSONResponse{
Code: 200,
JSON: toClientResponse(res),
}
}
}
func federatedEventRelationship(
ctx context.Context, fedReq *gomatrixserverlib.FederationRequest, db Database, rsAPI roomserver.RoomserverInternalAPI, fsAPI fs.FederationSenderInternalAPI,
) util.JSONResponse {
relation, err := NewEventRelationshipRequest(bytes.NewBuffer(fedReq.Content()))
if err != nil {
util.GetLogger(ctx).WithError(err).Error("failed to decode HTTP request as JSON")
return util.JSONResponse{
Code: 400,
JSON: jsonerror.BadJSON(fmt.Sprintf("invalid json: %s", err)),
}
}
rc := reqCtx{
ctx: ctx,
req: relation,
rsAPI: rsAPI,
db: db,
// federation args
isFederatedRequest: true,
fsAPI: fsAPI,
serverName: fedReq.Origin(),
}
res, resErr := rc.process()
if resErr != nil {
return *resErr
}
// add auth chain information
requiredAuthEventsSet := make(map[string]bool)
var requiredAuthEvents []string
for _, ev := range res.Events {
for _, a := range ev.AuthEventIDs() {
if requiredAuthEventsSet[a] {
continue
}
requiredAuthEvents = append(requiredAuthEvents, a)
requiredAuthEventsSet[a] = true
}
}
var queryRes roomserver.QueryAuthChainResponse
err = rsAPI.QueryAuthChain(ctx, &roomserver.QueryAuthChainRequest{
EventIDs: requiredAuthEvents,
}, &queryRes)
if err != nil {
// they may already have the auth events so don't fail this request
util.GetLogger(ctx).WithError(err).Error("Failed to QueryAuthChain")
}
res.AuthChain = make([]*gomatrixserverlib.Event, len(queryRes.AuthChain))
for i := range queryRes.AuthChain {
res.AuthChain[i] = queryRes.AuthChain[i].Unwrap()
}
return util.JSONResponse{
Code: 200,
JSON: res,
}
}
// nolint:gocyclo
func (rc *reqCtx) process() (*gomatrixserverlib.MSC2836EventRelationshipsResponse, *util.JSONResponse) {
var res gomatrixserverlib.MSC2836EventRelationshipsResponse
var returnEvents []*gomatrixserverlib.HeaderedEvent
// Can the user see (according to history visibility) event_id? If no, reject the request, else continue.
event := rc.getLocalEvent(rc.req.EventID)
if event == nil {
event = rc.fetchUnknownEvent(rc.req.EventID, rc.req.RoomID)
}
if rc.req.RoomID == "" && event != nil {
rc.req.RoomID = event.RoomID()
}
if event == nil || !rc.authorisedToSeeEvent(event) {
return nil, &util.JSONResponse{
Code: 403,
JSON: jsonerror.Forbidden("Event does not exist or you are not authorised to see it"),
}
}
rc.roomVersion = event.Version()
// Retrieve the event. Add it to response array.
returnEvents = append(returnEvents, event)
if rc.req.IncludeParent {
if parentEvent := rc.includeParent(event); parentEvent != nil {
returnEvents = append(returnEvents, parentEvent)
}
}
if rc.req.IncludeChildren {
remaining := rc.req.Limit - len(returnEvents)
if remaining > 0 {
children, resErr := rc.includeChildren(rc.db, event.EventID(), remaining, rc.req.RecentFirst)
if resErr != nil {
return nil, resErr
}
returnEvents = append(returnEvents, children...)
}
}
remaining := rc.req.Limit - len(returnEvents)
var walkLimited bool
if remaining > 0 {
included := make(map[string]bool, len(returnEvents))
for _, ev := range returnEvents {
included[ev.EventID()] = true
}
var events []*gomatrixserverlib.HeaderedEvent
events, walkLimited = walkThread(
rc.ctx, rc.db, rc, included, remaining,
)
returnEvents = append(returnEvents, events...)
}
res.Events = make([]*gomatrixserverlib.Event, len(returnEvents))
for i, ev := range returnEvents {
// for each event, extract the children_count | hash and add it as unsigned data.
rc.addChildMetadata(ev)
res.Events[i] = ev.Unwrap()
}
res.Limited = remaining == 0 || walkLimited
return &res, nil
}
// fetchUnknownEvent retrieves an unknown event from the room specified. This server must
// be joined to the room in question. This has the side effect of injecting surround threaded
// events into the roomserver.
func (rc *reqCtx) fetchUnknownEvent(eventID, roomID string) *gomatrixserverlib.HeaderedEvent {
if rc.isFederatedRequest || roomID == "" {
// we don't do fed hits for fed requests, and we can't ask servers without a room ID!
return nil
}
logger := util.GetLogger(rc.ctx).WithField("room_id", roomID)
// if they supplied a room_id, check the room exists.
var queryVerRes roomserver.QueryRoomVersionForRoomResponse
err := rc.rsAPI.QueryRoomVersionForRoom(rc.ctx, &roomserver.QueryRoomVersionForRoomRequest{
RoomID: roomID,
}, &queryVerRes)
if err != nil {
logger.WithError(err).Warn("failed to query room version for room, does this room exist?")
return nil
}
// check the user is joined to that room
var queryMemRes roomserver.QueryMembershipForUserResponse
err = rc.rsAPI.QueryMembershipForUser(rc.ctx, &roomserver.QueryMembershipForUserRequest{
RoomID: roomID,
UserID: rc.userID,
}, &queryMemRes)
if err != nil {
logger.WithError(err).Warn("failed to query membership for user in room")
return nil
}
if !queryMemRes.IsInRoom {
return nil
}
// ask one of the servers in the room for the event
var queryRes fs.QueryJoinedHostServerNamesInRoomResponse
err = rc.fsAPI.QueryJoinedHostServerNamesInRoom(rc.ctx, &fs.QueryJoinedHostServerNamesInRoomRequest{
RoomID: roomID,
}, &queryRes)
if err != nil {
logger.WithError(err).Error("failed to QueryJoinedHostServerNamesInRoom")
return nil
}
// query up to 5 servers
serversToQuery := queryRes.ServerNames
if len(serversToQuery) > 5 {
serversToQuery = serversToQuery[:5]
}
// fetch the event, along with some of the surrounding thread (if it's threaded) and the auth chain.
// Inject the response into the roomserver to remember the event across multiple calls and to set
// unexplored flags correctly.
for _, srv := range serversToQuery {
res, err := rc.MSC2836EventRelationships(eventID, srv, queryVerRes.RoomVersion)
if err != nil {
continue
}
rc.injectResponseToRoomserver(res)
for _, ev := range res.Events {
if ev.EventID() == eventID {
return ev.Headered(ev.Version())
}
}
}
logger.WithField("servers", serversToQuery).Warn("failed to query event relationships")
return nil
}
// If include_parent: true and there is a valid m.relationship field in the event,
// retrieve the referenced event. Apply history visibility check to that event and if it passes, add it to the response array.
func (rc *reqCtx) includeParent(childEvent *gomatrixserverlib.HeaderedEvent) (parent *gomatrixserverlib.HeaderedEvent) {
parentID, _, _ := parentChildEventIDs(childEvent)
if parentID == "" {
return nil
}
return rc.lookForEvent(parentID)
}
// If include_children: true, lookup all events which have event_id as an m.relationship
// Apply history visibility checks to all these events and add the ones which pass into the response array,
// honouring the recent_first flag and the limit.
func (rc *reqCtx) includeChildren(db Database, parentID string, limit int, recentFirst bool) ([]*gomatrixserverlib.HeaderedEvent, *util.JSONResponse) {
if rc.hasUnexploredChildren(parentID) {
// we need to do a remote request to pull in the children as we are missing them locally.
serversToQuery := rc.getServersForEventID(parentID)
var result *gomatrixserverlib.MSC2836EventRelationshipsResponse
for _, srv := range serversToQuery {
res, err := rc.fsAPI.MSC2836EventRelationships(rc.ctx, srv, gomatrixserverlib.MSC2836EventRelationshipsRequest{
EventID: parentID,
Direction: "down",
Limit: 100,
MaxBreadth: -1,
MaxDepth: 1, // we just want the children from this parent
RecentFirst: true,
}, rc.roomVersion)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).WithField("server", srv).Error("includeChildren: failed to call MSC2836EventRelationships")
} else {
result = &res
break
}
}
if result != nil {
rc.injectResponseToRoomserver(result)
}
// fallthrough to pull these new events from the DB
}
children, err := db.ChildrenForParent(rc.ctx, parentID, constRelType, recentFirst)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("failed to get ChildrenForParent")
resErr := jsonerror.InternalServerError()
return nil, &resErr
}
var childEvents []*gomatrixserverlib.HeaderedEvent
for _, child := range children {
childEvent := rc.lookForEvent(child.EventID)
if childEvent != nil {
childEvents = append(childEvents, childEvent)
}
}
if len(childEvents) > limit {
return childEvents[:limit], nil
}
return childEvents, nil
}
// Begin to walk the thread DAG in the direction specified, either depth or breadth first according to the depth_first flag,
// honouring the limit, max_depth and max_breadth values according to the following rules
func walkThread(
ctx context.Context, db Database, rc *reqCtx, included map[string]bool, limit int,
) ([]*gomatrixserverlib.HeaderedEvent, bool) {
var result []*gomatrixserverlib.HeaderedEvent
eventWalker := walker{
ctx: ctx,
req: rc.req,
db: db,
fn: func(wi *walkInfo) bool {
// If already processed event, skip.
if included[wi.EventID] {
return false
}
// If the response array is >= limit, stop.
if len(result) >= limit {
return true
}
// Process the event.
// if event is not found, use remoteEventRelationships to explore that part of the thread remotely.
// This will probably be easiest if the event relationships response is directly pumped into the database
// so the next walk will do the right thing. This requires those events to be authed and likely injected as
// outliers into the roomserver DB, which will de-dupe appropriately.
event := rc.lookForEvent(wi.EventID)
if event != nil {
result = append(result, event)
}
included[wi.EventID] = true
return false
},
}
limited, err := eventWalker.WalkFrom(rc.req.EventID)
if err != nil {
util.GetLogger(ctx).WithError(err).Errorf("Failed to WalkFrom %s", rc.req.EventID)
}
return result, limited
}
// MSC2836EventRelationships performs an /event_relationships request to a remote server
func (rc *reqCtx) MSC2836EventRelationships(eventID string, srv gomatrixserverlib.ServerName, ver gomatrixserverlib.RoomVersion) (*gomatrixserverlib.MSC2836EventRelationshipsResponse, error) {
res, err := rc.fsAPI.MSC2836EventRelationships(rc.ctx, srv, gomatrixserverlib.MSC2836EventRelationshipsRequest{
EventID: eventID,
DepthFirst: rc.req.DepthFirst,
Direction: rc.req.Direction,
Limit: rc.req.Limit,
MaxBreadth: rc.req.MaxBreadth,
MaxDepth: rc.req.MaxDepth,
RecentFirst: rc.req.RecentFirst,
}, ver)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("Failed to call MSC2836EventRelationships")
return nil, err
}
return &res, nil
}
// authorisedToSeeEvent checks that the user or server is allowed to see this event. Returns true if allowed to
// see this request. This only needs to be done once per room at present as we just check for joined status.
func (rc *reqCtx) authorisedToSeeEvent(event *gomatrixserverlib.HeaderedEvent) bool {
if rc.isFederatedRequest {
// make sure the server is in this room
var res fs.QueryJoinedHostServerNamesInRoomResponse
err := rc.fsAPI.QueryJoinedHostServerNamesInRoom(rc.ctx, &fs.QueryJoinedHostServerNamesInRoomRequest{
RoomID: event.RoomID(),
}, &res)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("authorisedToSeeEvent: failed to QueryJoinedHostServerNamesInRoom")
return false
}
for _, srv := range res.ServerNames {
if srv == rc.serverName {
return true
}
}
return false
}
// make sure the user is in this room
// Allow events if the member is in the room
// TODO: This does not honour history_visibility
// TODO: This does not honour m.room.create content
var queryMembershipRes roomserver.QueryMembershipForUserResponse
err := rc.rsAPI.QueryMembershipForUser(rc.ctx, &roomserver.QueryMembershipForUserRequest{
RoomID: event.RoomID(),
UserID: rc.userID,
}, &queryMembershipRes)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("authorisedToSeeEvent: failed to QueryMembershipForUser")
return false
}
return queryMembershipRes.IsInRoom
}
func (rc *reqCtx) getServersForEventID(eventID string) []gomatrixserverlib.ServerName {
if rc.req.RoomID == "" {
util.GetLogger(rc.ctx).WithField("event_id", eventID).Error(
"getServersForEventID: event exists in unknown room",
)
return nil
}
if rc.roomVersion == "" {
util.GetLogger(rc.ctx).WithField("event_id", eventID).Errorf(
"getServersForEventID: event exists in %s with unknown room version", rc.req.RoomID,
)
return nil
}
var queryRes fs.QueryJoinedHostServerNamesInRoomResponse
err := rc.fsAPI.QueryJoinedHostServerNamesInRoom(rc.ctx, &fs.QueryJoinedHostServerNamesInRoomRequest{
RoomID: rc.req.RoomID,
}, &queryRes)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("getServersForEventID: failed to QueryJoinedHostServerNamesInRoom")
return nil
}
// query up to 5 servers
serversToQuery := queryRes.ServerNames
if len(serversToQuery) > 5 {
serversToQuery = serversToQuery[:5]
}
return serversToQuery
}
func (rc *reqCtx) remoteEventRelationships(eventID string) *gomatrixserverlib.MSC2836EventRelationshipsResponse {
if rc.isFederatedRequest {
return nil // we don't query remote servers for remote requests
}
serversToQuery := rc.getServersForEventID(eventID)
var res *gomatrixserverlib.MSC2836EventRelationshipsResponse
var err error
for _, srv := range serversToQuery {
res, err = rc.MSC2836EventRelationships(eventID, srv, rc.roomVersion)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).WithField("server", srv).Error("remoteEventRelationships: failed to call MSC2836EventRelationships")
} else {
break
}
}
return res
}
// lookForEvent returns the event for the event ID given, by trying to query remote servers
// if the event ID is unknown via /event_relationships.
func (rc *reqCtx) lookForEvent(eventID string) *gomatrixserverlib.HeaderedEvent {
event := rc.getLocalEvent(eventID)
if event == nil {
queryRes := rc.remoteEventRelationships(eventID)
if queryRes != nil {
// inject all the events into the roomserver then return the event in question
rc.injectResponseToRoomserver(queryRes)
for _, ev := range queryRes.Events {
if ev.EventID() == eventID && rc.req.RoomID == ev.RoomID() {
return ev.Headered(ev.Version())
}
}
}
} else if rc.hasUnexploredChildren(eventID) {
// we have the local event but we may need to do a remote hit anyway if we are exploring the thread and have unknown children.
// If we don't do this then we risk never fetching the children.
queryRes := rc.remoteEventRelationships(eventID)
if queryRes != nil {
rc.injectResponseToRoomserver(queryRes)
err := rc.db.MarkChildrenExplored(context.Background(), eventID)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Warnf("failed to mark children of %s as explored", eventID)
}
}
}
if rc.req.RoomID == event.RoomID() {
return event
}
return nil
}
func (rc *reqCtx) getLocalEvent(eventID string) *gomatrixserverlib.HeaderedEvent {
var queryEventsRes roomserver.QueryEventsByIDResponse
err := rc.rsAPI.QueryEventsByID(rc.ctx, &roomserver.QueryEventsByIDRequest{
EventIDs: []string{eventID},
}, &queryEventsRes)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("getLocalEvent: failed to QueryEventsByID")
return nil
}
if len(queryEventsRes.Events) == 0 {
util.GetLogger(rc.ctx).WithField("event_id", eventID).Infof("getLocalEvent: event does not exist")
return nil // event does not exist
}
return queryEventsRes.Events[0]
}
// injectResponseToRoomserver injects the events
// into the roomserver as KindOutlier, with auth chains.
func (rc *reqCtx) injectResponseToRoomserver(res *gomatrixserverlib.MSC2836EventRelationshipsResponse) {
var stateEvents []*gomatrixserverlib.Event
var messageEvents []*gomatrixserverlib.Event
for _, ev := range res.Events {
if ev.StateKey() != nil {
stateEvents = append(stateEvents, ev)
} else {
messageEvents = append(messageEvents, ev)
}
}
respState := gomatrixserverlib.RespState{
AuthEvents: res.AuthChain,
StateEvents: stateEvents,
}
eventsInOrder, err := respState.Events()
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("failed to calculate order to send events in MSC2836EventRelationshipsResponse")
return
}
// everything gets sent as an outlier because auth chain events may be disjoint from the DAG
// as may the threaded events.
var ires []roomserver.InputRoomEvent
for _, outlier := range append(eventsInOrder, messageEvents...) {
ires = append(ires, roomserver.InputRoomEvent{
Kind: roomserver.KindOutlier,
Event: outlier.Headered(outlier.Version()),
AuthEventIDs: outlier.AuthEventIDs(),
})
}
// we've got the data by this point so use a background context
err = roomserver.SendInputRoomEvents(context.Background(), rc.rsAPI, ires)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Error("failed to inject MSC2836EventRelationshipsResponse into the roomserver")
}
// update the child count / hash columns for these nodes. We need to do this here because not all events will make it
// through to the KindNewEventPersisted hook because the roomserver will ignore duplicates. Duplicates have meaning though
// as the `unsigned` field may differ (if the number of children changes).
for _, ev := range ires {
err = rc.db.UpdateChildMetadata(context.Background(), ev.Event)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).WithField("event_id", ev.Event.EventID()).Warn("failed to update child metadata for event")
}
}
}
func (rc *reqCtx) addChildMetadata(ev *gomatrixserverlib.HeaderedEvent) {
count, hash := rc.getChildMetadata(ev.EventID())
if count == 0 {
return
}
err := ev.SetUnsignedField("children_hash", gomatrixserverlib.Base64Bytes(hash))
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Warn("Failed to set children_hash")
}
err = ev.SetUnsignedField("children", map[string]int{
constRelType: count,
})
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Warn("Failed to set children count")
}
}
func (rc *reqCtx) getChildMetadata(eventID string) (count int, hash []byte) {
children, err := rc.db.ChildrenForParent(rc.ctx, eventID, constRelType, false)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).Warn("Failed to get ChildrenForParent for getting child metadata")
return
}
if len(children) == 0 {
return
}
// sort it lexiographically
sort.Slice(children, func(i, j int) bool {
return children[i].EventID < children[j].EventID
})
// hash it
var eventIDs strings.Builder
for _, c := range children {
_, _ = eventIDs.WriteString(c.EventID)
}
hashValBytes := sha256.Sum256([]byte(eventIDs.String()))
count = len(children)
hash = hashValBytes[:]
return
}
// hasUnexploredChildren returns true if this event has unexplored children.
// "An event has unexplored children if the `unsigned` child count on the parent does not match
// how many children the server believes the parent to have. In addition, if the counts match but
// the hashes do not match, then the event is unexplored."
func (rc *reqCtx) hasUnexploredChildren(eventID string) bool {
if rc.isFederatedRequest {
return false // we only explore children for clients, not servers.
}
// extract largest child count from event
eventCount, eventHash, explored, err := rc.db.ChildMetadata(rc.ctx, eventID)
if err != nil {
util.GetLogger(rc.ctx).WithError(err).WithField("event_id", eventID).Warn(
"failed to get ChildMetadata from db",
)
return false
}
// if there are no recorded children then we know we have >= children.
// if the event has already been explored (read: we hit /event_relationships successfully)
// then don't do it again. We'll only re-do this if we get an even bigger children count,
// see Database.UpdateChildMetadata
if eventCount == 0 || explored {
return false // short-circuit
}
// calculate child count for event
calcCount, calcHash := rc.getChildMetadata(eventID)
if eventCount < calcCount {
return false // we have more children
} else if eventCount > calcCount {
return true // the event has more children than we know about
}
// we have the same count, so a mismatched hash means some children are different
return !bytes.Equal(eventHash, calcHash)
}
type walkInfo struct {
eventInfo
SiblingNumber int
Depth int
}
type walker struct {
ctx context.Context
req *EventRelationshipRequest
db Database
fn func(wi *walkInfo) bool // callback invoked for each event walked, return true to terminate the walk
}
// WalkFrom the event ID given
func (w *walker) WalkFrom(eventID string) (limited bool, err error) {
children, err := w.childrenForParent(eventID)
if err != nil {
util.GetLogger(w.ctx).WithError(err).Error("WalkFrom() childrenForParent failed, cannot walk")
return false, err
}
var next *walkInfo
toWalk := w.addChildren(nil, children, 1)
next, toWalk = w.nextChild(toWalk)
for next != nil {
stop := w.fn(next)
if stop {
return true, nil
}
// find the children's children
children, err = w.childrenForParent(next.EventID)
if err != nil {
util.GetLogger(w.ctx).WithError(err).Error("WalkFrom() childrenForParent failed, cannot walk")
return false, err
}
toWalk = w.addChildren(toWalk, children, next.Depth+1)
next, toWalk = w.nextChild(toWalk)
}
return false, nil
}
// addChildren adds an event's children to the to walk data structure
func (w *walker) addChildren(toWalk []walkInfo, children []eventInfo, depthOfChildren int) []walkInfo {
// Check what number child this event is (ordered by recent_first) compared to its parent, does it exceed (greater than) max_breadth? If yes, skip.
if len(children) > w.req.MaxBreadth {
children = children[:w.req.MaxBreadth]
}
// Check how deep the event is compared to event_id, does it exceed (greater than) max_depth? If yes, skip.
if depthOfChildren > w.req.MaxDepth {
return toWalk
}
if w.req.DepthFirst {
// the slice is a stack so push them in reverse order so we pop them in the correct order
// e.g [3,2,1] => [3,2] , 1 => [3] , 2 => [] , 3
for i := len(children) - 1; i >= 0; i-- {
toWalk = append(toWalk, walkInfo{
eventInfo: children[i],
SiblingNumber: i + 1, // index from 1
Depth: depthOfChildren,
})
}
} else {
// the slice is a queue so push them in normal order to we dequeue them in the correct order
// e.g [1,2,3] => 1, [2, 3] => 2 , [3] => 3, []
for i := range children {
toWalk = append(toWalk, walkInfo{
eventInfo: children[i],
SiblingNumber: i + 1, // index from 1
Depth: depthOfChildren,
})
}
}
return toWalk
}
func (w *walker) nextChild(toWalk []walkInfo) (*walkInfo, []walkInfo) {
if len(toWalk) == 0 {
return nil, nil
}
var child walkInfo
if w.req.DepthFirst {
// toWalk is a stack so pop the child off
child, toWalk = toWalk[len(toWalk)-1], toWalk[:len(toWalk)-1]
return &child, toWalk
}
// toWalk is a queue so shift the child off
child, toWalk = toWalk[0], toWalk[1:]
return &child, toWalk
}
// childrenForParent returns the children events for this event ID, honouring the direction: up|down flags
// meaning this can actually be returning the parent for the event instead of the children.
func (w *walker) childrenForParent(eventID string) ([]eventInfo, error) {
if w.req.Direction == "down" {
return w.db.ChildrenForParent(w.ctx, eventID, constRelType, w.req.RecentFirst)
}
// find the event to pull out the parent
ei, err := w.db.ParentForChild(w.ctx, eventID, constRelType)
if err != nil {
return nil, err
}
if ei != nil {
return []eventInfo{*ei}, nil
}
return nil, nil
}