p2p: make mconn transport test less flaky (#7973)

The previous implementation of the *test* was flaky, and this irons
out some of those problems. The primary assertion that was failing
(less than 1% of the time) was an error on close that I think we
shouldn't care about.

internal/p2p/transport_memory.go

@@ -94,17 +94,23 @@ type MemoryTransport struct {
 	bufferSize int
 
 	acceptCh chan *MemoryConnection
+	closeCh  chan struct{}
+	closeFn  func()
 }
 
 // newMemoryTransport creates a new MemoryTransport. This is for internal use by
 // MemoryNetwork, use MemoryNetwork.CreateTransport() instead.
 func newMemoryTransport(network *MemoryNetwork, nodeID types.NodeID) *MemoryTransport {
+	once := &sync.Once{}
+	closeCh := make(chan struct{})
 	return &MemoryTransport{
 		logger:     network.logger.With("local", nodeID),
 		network:    network,
 		nodeID:     nodeID,
 		bufferSize: network.bufferSize,
 		acceptCh:   make(chan *MemoryConnection),
+		closeCh:    closeCh,
+		closeFn:    func() { once.Do(func() { close(closeCh) }) },
 	}
 }
 
@@ -141,6 +147,8 @@ func (t *MemoryTransport) Endpoints() []Endpoint {
 // Accept implements Transport.
 func (t *MemoryTransport) Accept(ctx context.Context) (Connection, error) {
 	select {
+	case <-t.closeCh:
+		return nil, io.EOF
 	case conn := <-t.acceptCh:
 		t.logger.Info("accepted connection", "remote", conn.RemoteEndpoint().Path)
 		return conn, nil
@@ -197,6 +205,7 @@ func (t *MemoryTransport) Dial(ctx context.Context, endpoint Endpoint) (Connecti
 // Close implements Transport.
 func (t *MemoryTransport) Close() error {
 	t.network.RemoveTransport(t.nodeID)
+	t.closeFn()
 	return nil
 }
 

internal/p2p/transport_test.go

@@ -46,23 +46,22 @@ func TestTransport_AcceptClose(t *testing.T) {
 
 	withTransports(ctx, t, func(ctx context.Context, t *testing.T, makeTransport transportFactory) {
 		a := makeTransport(t)
-		opctx, opcancel := context.WithCancel(ctx)
-
-		// In-progress Accept should error on concurrent close.
-		errCh := make(chan error, 1)
-		go func() {
-			time.Sleep(200 * time.Millisecond)
-			opcancel()
-			errCh <- a.Close()
-		}()
+		opctx, opcancel := context.WithTimeout(ctx, 200*time.Millisecond)
+		defer opcancel()
 
 		_, err := a.Accept(opctx)
 		require.Error(t, err)
 		require.Equal(t, io.EOF, err)
-		require.NoError(t, <-errCh)
 
-		// Closed transport should return error immediately.
-		_, err = a.Accept(opctx)
+		<-opctx.Done()
+		_ = a.Close()
+
+		// Closed transport should return error immediately,
+		// because the transport is closed. We use the base
+		// context (ctx) rather than the operation context
+		// (opctx) because using the later would mean this
+		// could error because the context was canceled.
+		_, err = a.Accept(ctx)
 		require.Error(t, err)
 		require.Equal(t, io.EOF, err)
 	})