Pass optional dialer to constructor instead of mutating internal fields from tests

client/internal/netflow/conntrack/conntrack.go

@@ -47,19 +47,36 @@ type ConnTrack struct {
 	sysctlModified bool
 }
 
+// DialFunc is a constructor for netlink conntrack connections.
+type DialFunc func() (listener, error)
+
+// Option configures a ConnTrack instance.
+type Option func(*ConnTrack)
+
+// WithDialer overrides the default netlink dialer, primarily for testing.
+func WithDialer(dial DialFunc) Option {
+	return func(c *ConnTrack) {
+		c.dial = dial
+	}
+}
+
 func defaultDial() (listener, error) {
 	return nfct.Dial(nil)
 }
 
 // New creates a new connection tracker that interfaces with the kernel's conntrack system
-func New(flowLogger nftypes.FlowLogger, iface nftypes.IFaceMapper) *ConnTrack {
+func New(flowLogger nftypes.FlowLogger, iface nftypes.IFaceMapper, opts ...Option) *ConnTrack {
-	return &ConnTrack{
+	ct := &ConnTrack{
 		flowLogger: flowLogger,
 		iface:      iface,
 		instanceID: uuid.New(),
 		dial:       defaultDial,
 		done:       make(chan struct{}, 1),
 	}
+	for _, opt := range opts {
+		opt(ct)
+	}
+	return ct
 }
 
 // Start begins tracking connections by listening for conntrack events. This method is idempotent.

client/internal/netflow/conntrack/conntrack_test.go

@@ -40,18 +40,14 @@ func (m *mockListener) Close() error {
 func TestReconnectAfterError(t *testing.T) {
 	first := newMockListener()
 	second := newMockListener()
+	third := newMockListener()
+	listeners := []*mockListener{first, second, third}
 	callCount := atomic.Int32{}
 
-	ct := &ConnTrack{
+	ct := New(nil, nil, WithDialer(func() (listener, error) {
-		dial: func() (listener, error) {
+		n := int(callCount.Add(1)) - 1
-			n := callCount.Add(1)
+		return listeners[n], nil
-			if n == 1 {
+	}))
-				return first, nil
-			}
-			return second, nil
-		},
-		done: make(chan struct{}, 1),
-	}
 
 	err := ct.Start(false)
 	require.NoError(t, err)
@@ -72,15 +68,6 @@ func TestReconnectAfterError(t *testing.T) {
 	}
 
 	// Verify the receiver is still running by injecting and handling a second error.
-	third := newMockListener()
-	callCount.Store(2)
-	ct.mux.Lock()
-	ct.dial = func() (listener, error) {
-		callCount.Add(1)
-		return third, nil
-	}
-	ct.mux.Unlock()
-
 	second.errChan <- assert.AnError
 
 	require.Eventually(t, func() bool {
@@ -93,12 +80,9 @@ func TestReconnectAfterError(t *testing.T) {
 func TestStopDuringReconnectBackoff(t *testing.T) {
 	mock := newMockListener()
 
-	ct := &ConnTrack{
+	ct := New(nil, nil, WithDialer(func() (listener, error) {
-		dial: func() (listener, error) {
+		return mock, nil
-			return mock, nil
+	}))
-		},
-		done: make(chan struct{}, 1),
-	}
 
 	err := ct.Start(false)
 	require.NoError(t, err)
@@ -129,19 +113,16 @@ func TestStopRaceWithReconnectDial(t *testing.T) {
 	second := newMockListener()
 	callCount := atomic.Int32{}
 
-	ct := &ConnTrack{
+	ct := New(nil, nil, WithDialer(func() (listener, error) {
-		dial: func() (listener, error) {
+		n := callCount.Add(1)
-			n := callCount.Add(1)
+		if n == 1 {
-			if n == 1 {
+			return first, nil
-				return first, nil
+		}
-			}
+		// Second dial: signal that we're in progress, wait for test to call Stop.
-			// Second dial: signal that we're in progress, wait for test to call Stop.
+		close(dialStarted)
-			close(dialStarted)
+		<-dialProceed
-			<-dialProceed
+		return second, nil
-			return second, nil
+	}))
-		},
-		done: make(chan struct{}, 1),
-	}
 
 	err := ct.Start(false)
 	require.NoError(t, err)
@@ -182,18 +163,15 @@ func TestCloseRaceWithReconnectDial(t *testing.T) {
 	second := newMockListener()
 	callCount := atomic.Int32{}
 
-	ct := &ConnTrack{
+	ct := New(nil, nil, WithDialer(func() (listener, error) {
-		dial: func() (listener, error) {
+		n := callCount.Add(1)
-			n := callCount.Add(1)
+		if n == 1 {
-			if n == 1 {
+			return first, nil
-				return first, nil
+		}
-			}
+		close(dialStarted)
-			close(dialStarted)
+		<-dialProceed
-			<-dialProceed
+		return second, nil
-			return second, nil
+	}))
-		},
-		done: make(chan struct{}, 1),
-	}
 
 	err := ct.Start(false)
 	require.NoError(t, err)
@@ -228,13 +206,10 @@ func TestStartIsIdempotent(t *testing.T) {
 	mock := newMockListener()
 	callCount := atomic.Int32{}
 
-	ct := &ConnTrack{
+	ct := New(nil, nil, WithDialer(func() (listener, error) {
-		dial: func() (listener, error) {
+		callCount.Add(1)
-			callCount.Add(1)
+		return mock, nil
-			return mock, nil
+	}))
-		},
-		done: make(chan struct{}, 1),
-	}
 
 	err := ct.Start(false)
 	require.NoError(t, err)