usbip: close pre-promotion conns on shutdown

Tie accepted conns to s.ctx via closeConnOnContextDone and wait for
dispatch goroutines in Close so handshake reads/writes can no longer
leak goroutines or fds past service shutdown.

service/usbip/server.go

@@ -36,6 +36,8 @@ type ServerService struct {
 	sessions       map[DataSession]struct{}
 	sessionsClosed bool
 	sessionsWG     sync.WaitGroup
+
+	pendingConnsWG sync.WaitGroup
 }
 
 func NewServerService(ctx context.Context, logger log.ContextLogger, tag string, options option.USBIPServerServiceOptions) (adapter.Service, error) {
@@ -126,6 +128,7 @@ func (s *ServerService) Close() error {
 	for _, session := range sessions {
 		_ = session.Close()
 	}
+	s.pendingConnsWG.Wait()
 	s.sessionsWG.Wait()
 
 	s.reconcileAccess.Lock()

service/usbip/server_shared.go

@@ -34,11 +34,15 @@ func (s *ServerService) acceptLoop(ln net.Listener) {
 			s.logger.Error("accept: ", err)
 			return
 		}
+		s.pendingConnsWG.Add(1)
 		go s.dispatchConn(conn)
 	}
 }
 
 func (s *ServerService) dispatchConn(conn net.Conn) {
+	defer s.pendingConnsWG.Done()
+	cancelClose := closeConnOnContextDone(s.ctx, conn)
+	defer cancelClose()
 	var prefix [controlPrefaceSize]byte
 	_, err := io.ReadFull(conn, prefix[:])
 	if err != nil {