server: do not allow a client to change path name during PLAY or RECORD

pkg/liberrors/server.go

@@ -238,3 +238,14 @@ type ErrServerInvalidSession struct{}
 func (e ErrServerInvalidSession) Error() string {
 	return "invalid session"
 }
+
+// ErrServerPathHasChanged is an error that can be returned by a server.
+type ErrServerPathHasChanged struct {
+	Prev string
+	Cur  string
+}
+
+// Error implements the error interface.
+func (e ErrServerPathHasChanged) Error() string {
+	return fmt.Sprintf("path has changed, was '%s', now is '%s'", e.Prev, e.Cur)
+}

serversession.go

@@ -769,6 +769,13 @@ func (ss *ServerSession) handleRequest(sc *ServerConn, req *base.Request) (*base
 
 		path, query := base.PathSplitQuery(pathAndQuery)
 
+		if ss.State() == ServerSessionStatePrePlay &&
+			path != *ss.setuppedPath {
+			return &base.Response{
+				StatusCode: base.StatusBadRequest,
+			}, liberrors.ErrServerPathHasChanged{Prev: *ss.setuppedPath, Cur: path}
+		}
+
 		res, err := sc.s.Handler.(ServerHandlerOnPlay).OnPlay(&ServerHandlerOnPlayCtx{
 			Session: ss,
 			Conn:    sc,
@@ -884,6 +891,12 @@ func (ss *ServerSession) handleRequest(sc *ServerConn, req *base.Request) (*base
 			ss.tcpConn = sc
 		}
 
+		if path != *ss.setuppedPath {
+			return &base.Response{
+				StatusCode: base.StatusBadRequest,
+			}, liberrors.ErrServerPathHasChanged{Prev: *ss.setuppedPath, Cur: path}
+		}
+
 		res, err := ss.s.Handler.(ServerHandlerOnRecord).OnRecord(&ServerHandlerOnRecordCtx{
 			Session: ss,
 			Conn:    sc,