refactor(netx): extract tlsdialer from dialer

internal/engine/netx/tlsdialer/saver.go

@@ -0,0 +1,49 @@
+package tlsdialer
+
+import (
+	"context"
+	"crypto/tls"
+	"net"
+	"time"
+
+	"github.com/ooni/probe-cli/v3/internal/engine/internal/tlsx"
+	"github.com/ooni/probe-cli/v3/internal/engine/netx/trace"
+)
+
+// SaverTLSHandshaker saves events occurring during the handshake
+type SaverTLSHandshaker struct {
+	TLSHandshaker
+	Saver *trace.Saver
+}
+
+// Handshake implements TLSHandshaker.Handshake
+func (h SaverTLSHandshaker) Handshake(
+	ctx context.Context, conn net.Conn, config *tls.Config,
+) (net.Conn, tls.ConnectionState, error) {
+	start := time.Now()
+	h.Saver.Write(trace.Event{
+		Name:          "tls_handshake_start",
+		NoTLSVerify:   config.InsecureSkipVerify,
+		TLSNextProtos: config.NextProtos,
+		TLSServerName: config.ServerName,
+		Time:          start,
+	})
+	tlsconn, state, err := h.TLSHandshaker.Handshake(ctx, conn, config)
+	stop := time.Now()
+	h.Saver.Write(trace.Event{
+		Duration:           stop.Sub(start),
+		Err:                err,
+		Name:               "tls_handshake_done",
+		NoTLSVerify:        config.InsecureSkipVerify,
+		TLSCipherSuite:     tlsx.CipherSuiteString(state.CipherSuite),
+		TLSNegotiatedProto: state.NegotiatedProtocol,
+		TLSNextProtos:      config.NextProtos,
+		TLSPeerCerts:       trace.PeerCerts(state, err),
+		TLSServerName:      config.ServerName,
+		TLSVersion:         tlsx.VersionString(state.Version),
+		Time:               stop,
+	})
+	return tlsconn, state, err
+}
+
+var _ TLSHandshaker = SaverTLSHandshaker{}