refactor: merge psiphonx and torx into tunnel (#287)

* refactor: merge psiphonx and torx into tunnel

This is a case where it seems that merging these three packages into
a single package will enable us to better the implementation.

The goal is still https://github.com/ooni/probe/issues/985.

The roadblock I'm trying to overcome is
https://github.com/ooni/probe-cli/pull/286#pullrequestreview-627460104.

* avoid duplicating logger for now

internal/engine/internal/torx/torx.go

@@ -1,137 +0,0 @@
-// Package torx contains code to control tor.
-package torx
-
-import (
-	"context"
-	"fmt"
-	"net/url"
-	"path"
-	"strings"
-	"time"
-
-	"github.com/cretz/bine/control"
-	"github.com/cretz/bine/tor"
-)
-
-// Session is the way in which this package sees a Session.
-type Session interface {
-	TempDir() string
-	TorArgs() []string
-	TorBinary() string
-}
-
-// TorProcess is a running tor process
-type TorProcess interface {
-	Close() error
-}
-
-// Tunnel is the Tor tunnel
-type Tunnel struct {
-	bootstrapTime time.Duration
-	instance      TorProcess
-	proxy         *url.URL
-}
-
-// BootstrapTime is the bootstrsap time
-func (tt *Tunnel) BootstrapTime() (duration time.Duration) {
-	if tt != nil {
-		duration = tt.bootstrapTime
-	}
-	return
-}
-
-// SOCKS5ProxyURL returns the URL of the SOCKS5 proxy
-func (tt *Tunnel) SOCKS5ProxyURL() (url *url.URL) {
-	if tt != nil {
-		url = tt.proxy
-	}
-	return
-}
-
-// Stop stops the Tor tunnel
-func (tt *Tunnel) Stop() {
-	if tt != nil {
-		tt.instance.Close()
-	}
-}
-
-// StartConfig contains the configuration for StartWithConfig
-type StartConfig struct {
-	Sess          Session
-	Start         func(ctx context.Context, conf *tor.StartConf) (*tor.Tor, error)
-	EnableNetwork func(ctx context.Context, tor *tor.Tor, wait bool) error
-	GetInfo       func(ctrl *control.Conn, keys ...string) ([]*control.KeyVal, error)
-}
-
-// Start starts the tor tunnel
-func Start(ctx context.Context, sess Session) (*Tunnel, error) {
-	return StartWithConfig(ctx, StartConfig{
-		Sess: sess,
-		Start: func(ctx context.Context, conf *tor.StartConf) (*tor.Tor, error) {
-			return tor.Start(ctx, conf)
-		},
-		EnableNetwork: func(ctx context.Context, tor *tor.Tor, wait bool) error {
-			return tor.EnableNetwork(ctx, wait)
-		},
-		GetInfo: func(ctrl *control.Conn, keys ...string) ([]*control.KeyVal, error) {
-			return ctrl.GetInfo(keys...)
-		},
-	})
-}
-
-// StartWithConfig is a configurable Start for testing
-func StartWithConfig(ctx context.Context, config StartConfig) (*Tunnel, error) {
-	select {
-	case <-ctx.Done():
-		return nil, ctx.Err() // allows to write unit tests using this code
-	default:
-	}
-	logfile := LogFile(config.Sess)
-	extraArgs := append([]string{}, config.Sess.TorArgs()...)
-	extraArgs = append(extraArgs, "Log")
-	extraArgs = append(extraArgs, "notice stderr")
-	extraArgs = append(extraArgs, "Log")
-	extraArgs = append(extraArgs, fmt.Sprintf(`notice file %s`, logfile))
-	instance, err := config.Start(ctx, &tor.StartConf{
-		DataDir:   path.Join(config.Sess.TempDir(), "tor"),
-		ExtraArgs: extraArgs,
-		ExePath:   config.Sess.TorBinary(),
-		NoHush:    true,
-	})
-	if err != nil {
-		return nil, err
-	}
-	instance.StopProcessOnClose = true
-	start := time.Now()
-	if err := config.EnableNetwork(ctx, instance, true); err != nil {
-		instance.Close()
-		return nil, err
-	}
-	stop := time.Now()
-	// Adapted from <https://git.io/Jfc7N>
-	info, err := config.GetInfo(instance.Control, "net/listeners/socks")
-	if err != nil {
-		instance.Close()
-		return nil, err
-	}
-	if len(info) != 1 || info[0].Key != "net/listeners/socks" {
-		instance.Close()
-		return nil, fmt.Errorf("unable to get socks proxy address")
-	}
-	proxyAddress := info[0].Val
-	if strings.HasPrefix(proxyAddress, "unix:") {
-		instance.Close()
-		return nil, fmt.Errorf("tor returned unsupported proxy")
-	}
-	return &Tunnel{
-		bootstrapTime: stop.Sub(start),
-		instance:      instance,
-		proxy:         &url.URL{Scheme: "socks5", Host: proxyAddress},
-	}, nil
-}
-
-// LogFile returns the name of tor logs given a specific session. The file
-// is always located somewhere inside the sess.TempDir() directory.
-func LogFile(sess Session) string {
-	return path.Join(sess.TempDir(), "tor.log")
-}