refactor(tlstool): make space for several splitting techniques

Part of #622

experiment/tlstool/internal/fake_test.go → experiment/tlstool/internal/patternsplitter/fake_test.go

@@ -1,4 +1,4 @@
-package internal
+package patternsplitter
 
 import (
 	"context"

experiment/tlstool/internal/split.go → experiment/tlstool/internal/patternsplitter/split.go

@@ -1,4 +1,6 @@
-package internal
+// Package patternsplitter contains code to split TCP segments in
+// the middle of a specific byte pattern.
+package patternsplitter
 
 import (
 	"bytes"
@@ -9,8 +11,9 @@ import (
 	"github.com/ooni/probe-engine/netx"
 )
 
-// SplitDialer is a dialer that splits writes according to a
-// pattern and may delay the second write of delay milliseconds.
+// SplitDialer is a dialer that splits TCP segments in the middle of
+// a specific byte pattern and may optionally delay writing the second
+// half of the segment by a specific number of milliseconds.
 type SplitDialer struct {
 	netx.Dialer
 	Delay   int64
@@ -26,7 +29,13 @@ func (d SplitDialer) DialContext(ctx context.Context, network, address string) (
 	return SplitConn{Conn: conn, Delay: d.Delay, Pattern: []byte(d.Pattern)}, nil
 }
 
-// SplitConn is a conn that splits writes.
+// SplitConn is the net.Conn generated by SplitDialer.
+//
+// Caveat
+//
+// The connection will keep splitting segments when it sees the
+// specified byte pattern. This behaviour is fine as long as we're
+// just checking whether the TLS handshake works.
 type SplitConn struct {
 	net.Conn
 	BeforeSecondWrite func() // for testing

experiment/tlstool/internal/split_test.go → experiment/tlstool/internal/patternsplitter/split_test.go

@@ -1,17 +1,17 @@
-package internal_test
+package patternsplitter_test
 
 import (
 	"context"
 	"errors"
 	"testing"
 
 	"github.com/google/go-cmp/cmp"
-	"github.com/ooni/probe-engine/experiment/tlstool/internal"
+	"github.com/ooni/probe-engine/experiment/tlstool/internal/patternsplitter"
 )
 
 func TestSplitDialerFailure(t *testing.T) {
 	expected := errors.New("mocked error")
-	d := internal.SplitDialer{Dialer: internal.FakeDialer{Err: expected}}
+	d := patternsplitter.SplitDialer{Dialer: patternsplitter.FakeDialer{Err: expected}}
 	conn, err := d.DialContext(context.Background(), "tcp", "1.1.1.1:853")
 	if !errors.Is(err, expected) {
 		t.Fatalf("not the error we expected: %+v", err)
@@ -22,19 +22,19 @@ func TestSplitDialerFailure(t *testing.T) {
 }
 
 func TestSplitDialerSuccess(t *testing.T) {
-	innerconn := &internal.FakeConn{}
-	d := internal.SplitDialer{
-		Dialer:  internal.FakeDialer{Conn: innerconn},
+	innerconn := &patternsplitter.FakeConn{}
+	d := patternsplitter.SplitDialer{
+		Dialer:  patternsplitter.FakeDialer{Conn: innerconn},
 		Delay:   1234,
 		Pattern: "abcdef",
 	}
 	conn, err := d.DialContext(context.Background(), "tcp", "1.1.1.1:853")
 	if err != nil {
 		t.Fatal(err)
 	}
-	realconn, ok := conn.(internal.SplitConn)
+	realconn, ok := conn.(patternsplitter.SplitConn)
 	if !ok {
-		t.Fatal("cannot cast conn to internal.SplitConn")
+		t.Fatal("cannot cast conn to patternsplitter.SplitConn")
 	}
 	if realconn.Delay != 1234 {
 		t.Fatal("invalid Delay value")
@@ -52,8 +52,8 @@ func TestWriteSuccessNoSplit(t *testing.T) {
 		pattern = "abc.def"
 		data    = "deadbeefdeafbeef"
 	)
-	innerconn := &internal.FakeConn{}
-	conn := internal.SplitConn{
+	innerconn := &patternsplitter.FakeConn{}
+	conn := patternsplitter.SplitConn{
 		Conn:    innerconn,
 		Pattern: []byte(pattern),
 	}
@@ -78,10 +78,10 @@ func TestWriteFailureNoSplit(t *testing.T) {
 		data    = "deadbeefdeafbeef"
 	)
 	expected := errors.New("mocked error")
-	innerconn := &internal.FakeConn{
+	innerconn := &patternsplitter.FakeConn{
 		WriteError: expected,
 	}
-	conn := internal.SplitConn{
+	conn := patternsplitter.SplitConn{
 		Conn:    innerconn,
 		Pattern: []byte(pattern),
 	}
@@ -99,8 +99,8 @@ func TestWriteSuccessSplit(t *testing.T) {
 		pattern = "abc.def"
 		data    = "deadbeefabc.defdeafbeef"
 	)
-	innerconn := &internal.FakeConn{}
-	conn := internal.SplitConn{
+	innerconn := &patternsplitter.FakeConn{}
+	conn := patternsplitter.SplitConn{
 		Conn:    innerconn,
 		Pattern: []byte(pattern),
 	}
@@ -128,10 +128,10 @@ func TestWriteFailureSplitFirstWrite(t *testing.T) {
 		data    = "deadbeefabc.defdeafbeef"
 	)
 	expected := errors.New("mocked error")
-	innerconn := &internal.FakeConn{
+	innerconn := &patternsplitter.FakeConn{
 		WriteError: expected,
 	}
-	conn := internal.SplitConn{
+	conn := patternsplitter.SplitConn{
 		Conn:    innerconn,
 		Pattern: []byte(pattern),
 	}
@@ -153,8 +153,8 @@ func TestWriteFailureSplitSecondWrite(t *testing.T) {
 		data    = "deadbeefabc.defdeafbeef"
 	)
 	expected := errors.New("mocked error")
-	innerconn := &internal.FakeConn{}
-	conn := internal.SplitConn{
+	innerconn := &patternsplitter.FakeConn{}
+	conn := patternsplitter.SplitConn{
 		BeforeSecondWrite: func() {
 			innerconn.WriteError = expected // second write will then fail
 		},

experiment/tlstool/tlstool.go

@@ -14,7 +14,7 @@ import (
 	"fmt"
 	"net"
 
-	"github.com/ooni/probe-engine/experiment/tlstool/internal"
+	"github.com/ooni/probe-engine/experiment/tlstool/internal/patternsplitter"
 	"github.com/ooni/probe-engine/internal/runtimex"
 	"github.com/ooni/probe-engine/model"
 	"github.com/ooni/probe-engine/netx"
@@ -29,13 +29,13 @@ const (
 // Config contains the experiment configuration.
 type Config struct {
 	Delay int64  `ooni:"Milliseconds to wait between writes"`
-	SNI   string `ooni:"Set the specified SNI"`
+	SNI   string `ooni:"Force using the specified SNI"`
 }
 
 // TestKeys contains the experiment results.
 type TestKeys struct {
-	VanillaFailure *string `json:"vanilla_failure"`
-	SplitFailure   *string `json:"split_failure"`
+	VanillaFailure  *string `json:"vanilla_failure"`
+	SNISplitFailure *string `json:"sni_split_failure"`
 }
 
 // Measurer performs the measurement.
@@ -66,9 +66,9 @@ func (m Measurer) Run(
 	err := m.vanillaRun(ctx, sess.Logger(), address)
 	callbacks.OnProgress(0.5, fmt.Sprintf("vanilla: %+v", err))
 	tk.VanillaFailure = archival.NewFailure(err)
-	err = m.splitRun(ctx, sess.Logger(), address)
+	err = m.sniSplitRun(ctx, sess.Logger(), address)
 	callbacks.OnProgress(1.0, fmt.Sprintf("split: %+v", err))
-	tk.SplitFailure = archival.NewFailure(err)
+	tk.SNISplitFailure = archival.NewFailure(err)
 	return nil
 }
 
@@ -96,8 +96,8 @@ func (m Measurer) vanillaRun(ctx context.Context, logger model.Logger, address s
 	return nil
 }
 
-func (m Measurer) splitRun(ctx context.Context, logger model.Logger, address string) error {
-	dialer := &internal.SplitDialer{
+func (m Measurer) sniSplitRun(ctx context.Context, logger model.Logger, address string) error {
+	dialer := &patternsplitter.SplitDialer{
 		Dialer:  m.newDialer(logger),
 		Delay:   m.config.Delay,
 		Pattern: m.pattern(address),