chore: merge probe-engine into probe-cli (#201)

This is how I did it:

1. `git clone https://github.com/ooni/probe-engine internal/engine`

2. ```
(cd internal/engine && git describe --tags)
v0.23.0
```

3. `nvim go.mod` (merging `go.mod` with `internal/engine/go.mod`

4. `rm -rf internal/.git internal/engine/go.{mod,sum}`

5. `git add internal/engine`

6. `find . -type f -name \*.go -exec sed -i 's@/ooni/probe-engine@/ooni/probe-cli/v3/internal/engine@g' {} \;`

7. `go build ./...` (passes)

8. `go test -race ./...` (temporary failure on RiseupVPN)

9. `go mod tidy`

10. this commit message

Once this piece of work is done, we can build a new version of `ooniprobe` that
is using `internal/engine` directly. We need to do more work to ensure all the
other functionality in `probe-engine` (e.g. making mobile packages) are still WAI.

Part of https://github.com/ooni/probe/issues/1335

internal/engine/netx/dialer/emitter_test.go

@@ -0,0 +1,166 @@
+package dialer_test
+
+import (
+	"context"
+	"errors"
+	"io"
+	"testing"
+	"time"
+
+	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/dialid"
+	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/handlers"
+	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/modelx"
+	"github.com/ooni/probe-cli/v3/internal/engine/legacy/netx/transactionid"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/dialer"
+)
+
+func TestEmitterFailure(t *testing.T) {
+	ctx := dialid.WithDialID(context.Background())
+	saver := &handlers.SavingHandler{}
+	ctx = modelx.WithMeasurementRoot(ctx, &modelx.MeasurementRoot{
+		Beginning: time.Now(),
+		Handler:   saver,
+	})
+	ctx = transactionid.WithTransactionID(ctx)
+	d := dialer.EmitterDialer{Dialer: dialer.EOFDialer{}}
+	conn, err := d.DialContext(ctx, "tcp", "www.google.com:443")
+	if !errors.Is(err, io.EOF) {
+		t.Fatal("not the error we expected")
+	}
+	if conn != nil {
+		t.Fatal("expected a nil conn here")
+	}
+	events := saver.Read()
+	if len(events) != 1 {
+		t.Fatal("unexpected number of events saved")
+	}
+	if events[0].Connect == nil {
+		t.Fatal("expected non nil Connect")
+	}
+	conninfo := events[0].Connect
+	if conninfo.ConnID != 0 {
+		t.Fatal("unexpected ConnID value")
+	}
+	emitterCheckConnectEventCommon(t, conninfo, io.EOF)
+}
+
+func emitterCheckConnectEventCommon(
+	t *testing.T, conninfo *modelx.ConnectEvent, err error) {
+	if conninfo.DialID == 0 {
+		t.Fatal("unexpected DialID value")
+	}
+	if conninfo.DurationSinceBeginning == 0 {
+		t.Fatal("unexpected DurationSinceBeginning value")
+	}
+	if !errors.Is(conninfo.Error, err) {
+		t.Fatal("unexpected Error value")
+	}
+	if conninfo.Network != "tcp" {
+		t.Fatal("unexpected Network value")
+	}
+	if conninfo.RemoteAddress != "www.google.com:443" {
+		t.Fatal("unexpected Network value")
+	}
+	if conninfo.SyscallDuration == 0 {
+		t.Fatal("unexpected SyscallDuration value")
+	}
+	if conninfo.TransactionID == 0 {
+		t.Fatal("unexpected TransactionID value")
+	}
+}
+
+func TestEmitterSuccess(t *testing.T) {
+	ctx := dialid.WithDialID(context.Background())
+	saver := &handlers.SavingHandler{}
+	ctx = modelx.WithMeasurementRoot(ctx, &modelx.MeasurementRoot{
+		Beginning: time.Now(),
+		Handler:   saver,
+	})
+	ctx = transactionid.WithTransactionID(ctx)
+	d := dialer.EmitterDialer{Dialer: dialer.EOFConnDialer{}}
+	conn, err := d.DialContext(ctx, "tcp", "www.google.com:443")
+	if err != nil {
+		t.Fatal("we expected no error")
+	}
+	if conn == nil {
+		t.Fatal("expected a non-nil conn here")
+	}
+	conn.Read(nil)
+	conn.Write(nil)
+	conn.Close()
+	events := saver.Read()
+	if len(events) != 4 {
+		t.Fatal("unexpected number of events saved")
+	}
+	if events[0].Connect == nil {
+		t.Fatal("expected non nil Connect")
+	}
+	conninfo := events[0].Connect
+	if conninfo.ConnID == 0 {
+		t.Fatal("unexpected ConnID value")
+	}
+	emitterCheckConnectEventCommon(t, conninfo, nil)
+	if events[1].Read == nil {
+		t.Fatal("expected non nil Read")
+	}
+	emitterCheckReadEvent(t, events[1].Read)
+	if events[2].Write == nil {
+		t.Fatal("expected non nil Write")
+	}
+	emitterCheckWriteEvent(t, events[2].Write)
+	if events[3].Close == nil {
+		t.Fatal("expected non nil Close")
+	}
+	emitterCheckCloseEvent(t, events[3].Close)
+}
+
+func emitterCheckReadEvent(t *testing.T, ev *modelx.ReadEvent) {
+	if ev.ConnID == 0 {
+		t.Fatal("unexpected ConnID")
+	}
+	if ev.DurationSinceBeginning == 0 {
+		t.Fatal("unexpected DurationSinceBeginning")
+	}
+	if !errors.Is(ev.Error, io.EOF) {
+		t.Fatal("unexpected Error")
+	}
+	if ev.NumBytes != 0 {
+		t.Fatal("unexpected NumBytes")
+	}
+	if ev.SyscallDuration == 0 {
+		t.Fatal("unexpected SyscallDuration")
+	}
+}
+
+func emitterCheckWriteEvent(t *testing.T, ev *modelx.WriteEvent) {
+	if ev.ConnID == 0 {
+		t.Fatal("unexpected ConnID")
+	}
+	if ev.DurationSinceBeginning == 0 {
+		t.Fatal("unexpected DurationSinceBeginning")
+	}
+	if !errors.Is(ev.Error, io.EOF) {
+		t.Fatal("unexpected Error")
+	}
+	if ev.NumBytes != 0 {
+		t.Fatal("unexpected NumBytes")
+	}
+	if ev.SyscallDuration == 0 {
+		t.Fatal("unexpected SyscallDuration")
+	}
+}
+
+func emitterCheckCloseEvent(t *testing.T, ev *modelx.CloseEvent) {
+	if ev.ConnID == 0 {
+		t.Fatal("unexpected ConnID")
+	}
+	if ev.DurationSinceBeginning == 0 {
+		t.Fatal("unexpected DurationSinceBeginning")
+	}
+	if !errors.Is(ev.Error, io.EOF) {
+		t.Fatal("unexpected Error")
+	}
+	if ev.SyscallDuration == 0 {
+		t.Fatal("unexpected SyscallDuration")
+	}
+}