Fix crash when announcing unloaded torrent to websocket

client.go

@@ -247,10 +247,14 @@ func NewClient(cfg *ClientConfig) (cl *Client, err error) {
 	cl.websocketTrackers = websocketTrackers{
 		PeerId: cl.peerID,
 		Logger: cl.logger,
-		GetAnnounceRequest: func(event tracker.AnnounceEvent, infoHash [20]byte) tracker.AnnounceRequest {
+		GetAnnounceRequest: func(event tracker.AnnounceEvent, infoHash [20]byte) (tracker.AnnounceRequest, error) {
 			cl.lock()
 			defer cl.unlock()
-			return cl.torrents[infoHash].announceRequest(event)
+			t, ok := cl.torrents[infoHash]
+			if !ok {
+				return tracker.AnnounceRequest{}, errors.New("torrent not tracked by client")
+			}
+			return t.announceRequest(event), nil
 		},
 		OnConn: func(dc datachannel.ReadWriteCloser, dcc webtorrent.DataChannelContext) {
 			cl.lock()

webtorrent/tracker_client.go

@@ -24,7 +24,7 @@ type TrackerClientStats struct {
 // Client represents the webtorrent client
 type TrackerClient struct {
 	Url                string
-	GetAnnounceRequest func(_ tracker.AnnounceEvent, infoHash [20]byte) tracker.AnnounceRequest
+	GetAnnounceRequest func(_ tracker.AnnounceEvent, infoHash [20]byte) (tracker.AnnounceRequest, error)
 	PeerId             [20]byte
 	OnConn             onDataChannelOpen
 	Logger             log.Logger
@@ -135,7 +135,10 @@ func (tc *TrackerClient) Announce(event tracker.AnnounceEvent, infoHash [20]byte
 		return fmt.Errorf("creating offer: %w", err)
 	}
 
-	request := tc.GetAnnounceRequest(event, infoHash)
+	request, err := tc.GetAnnounceRequest(event, infoHash)
+	if err != nil {
+		return fmt.Errorf("getting announce parameters: %w", err)
+	}
 
 	req := AnnounceRequest{
 		Numwant:    1, // If higher we need to create equal amount of offers.

wstracker.go

@@ -33,7 +33,7 @@ type refCountedWebtorrentTrackerClient struct {
 type websocketTrackers struct {
 	PeerId             [20]byte
 	Logger             log.Logger
-	GetAnnounceRequest func(event tracker.AnnounceEvent, infoHash [20]byte) tracker.AnnounceRequest
+	GetAnnounceRequest func(event tracker.AnnounceEvent, infoHash [20]byte) (tracker.AnnounceRequest, error)
 	OnConn             func(datachannel.ReadWriteCloser, webtorrent.DataChannelContext)
 	mu                 sync.Mutex
 	clients            map[string]*refCountedWebtorrentTrackerClient