refactor: only use shaping dialer for ndt7 and dash (#754)

See https://github.com/ooni/probe/issues/2112 for context.

While there, run `go fix -fix buildtag ./...`

internal/netxlite/shaping.go

@@ -0,0 +1,15 @@
+package netxlite
+
+import "github.com/ooni/probe-cli/v3/internal/model"
+
+// NewMaybeShapingDialer takes in input a model.Dialer and returns in output another
+// model.Dialer that MAY dial connections with I/O shaping, depending on whether
+// the user builds with or without the `-tags shaping` CLI flag.
+//
+// We typically use `-tags shaping` when running integration tests for dash and ndt7 to
+// avoiod hammering m-lab servers from the very-fast GitHub CI servers.
+//
+// See https://github.com/ooni/probe/issues/2112 for extra context.
+func NewMaybeShapingDialer(dialer model.Dialer) model.Dialer {
+	return newMaybeShapingDialer(dialer)
+}

internal/netxlite/shaping_otherwise.go

@@ -0,0 +1,11 @@
+//go:build !shaping
+
+package netxlite
+
+import (
+	"github.com/ooni/probe-cli/v3/internal/model"
+)
+
+func newMaybeShapingDialer(dialer model.Dialer) model.Dialer {
+	return dialer
+}

internal/netxlite/shaping_otherwise_test.go

@@ -0,0 +1,17 @@
+//go:build !shaping
+
+package netxlite
+
+import (
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
+)
+
+func TestNewShapingDialer(t *testing.T) {
+	in := &mocks.Dialer{}
+	out := NewMaybeShapingDialer(in)
+	if in != out {
+		t.Fatal("expected to see the same pointer")
+	}
+}

internal/netxlite/shaping_shaping.go

@@ -0,0 +1,43 @@
+//go:build shaping
+
+package netxlite
+
+import (
+	"context"
+	"net"
+	"time"
+
+	"github.com/ooni/probe-cli/v3/internal/model"
+)
+
+func newMaybeShapingDialer(dialer model.Dialer) model.Dialer {
+	return &shapingDialer{dialer}
+}
+
+type shapingDialer struct {
+	model.Dialer
+}
+
+// DialContext implements Dialer.DialContext
+func (d *shapingDialer) DialContext(
+	ctx context.Context, network, address string) (net.Conn, error) {
+	conn, err := d.Dialer.DialContext(ctx, network, address)
+	if err != nil {
+		return nil, err
+	}
+	return &shapingConn{Conn: conn}, nil
+}
+
+type shapingConn struct {
+	net.Conn
+}
+
+func (c *shapingConn) Read(p []byte) (int, error) {
+	time.Sleep(100 * time.Millisecond)
+	return c.Conn.Read(p)
+}
+
+func (c *shapingConn) Write(p []byte) (int, error) {
+	time.Sleep(100 * time.Millisecond)
+	return c.Conn.Write(p)
+}

internal/netxlite/shaping_shaping_test.go

@@ -0,0 +1,66 @@
+//go:build shaping
+
+package netxlite
+
+import (
+	"context"
+	"errors"
+	"net"
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/model/mocks"
+)
+
+func TestNewShapingDialerx(t *testing.T) {
+	t.Run("failure", func(t *testing.T) {
+		expected := errors.New("mocked error")
+		d := &mocks.Dialer{
+			MockDialContext: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return nil, expected
+			},
+		}
+		shd := NewMaybeShapingDialer(d)
+		conn, err := shd.DialContext(context.Background(), "tcp", "8.8.8.8:443")
+		if !errors.Is(err, expected) {
+			t.Fatal("unexpected err", err)
+		}
+		if conn != nil {
+			t.Fatal("expected nil conn")
+		}
+	})
+
+	t.Run("success", func(t *testing.T) {
+		expected := errors.New("mocked error")
+		uc := &mocks.Conn{
+			MockRead: func(b []byte) (int, error) {
+				return 0, expected
+			},
+			MockWrite: func(b []byte) (int, error) {
+				return 0, expected
+			},
+		}
+		d := &mocks.Dialer{
+			MockDialContext: func(ctx context.Context, network, address string) (net.Conn, error) {
+				return uc, nil
+			},
+		}
+		shd := NewMaybeShapingDialer(d)
+		conn, err := shd.DialContext(context.Background(), "tcp", "8.8.8.8:443")
+		if err != nil {
+			t.Fatal(err)
+		}
+		if _, ok := conn.(*shapingConn); !ok {
+			t.Fatal("not shapingConn")
+		}
+		validateCountAndErr := func(count int, err error) {
+			if !errors.Is(err, expected) {
+				t.Fatal("unexpected err", err)
+			}
+			if count != 0 {
+				t.Fatal("expected zero")
+			}
+		}
+		validateCountAndErr(conn.Read(make([]byte, 16)))
+		validateCountAndErr(conn.Write(make([]byte, 16)))
+	})
+}