feat: tlsmiddlebox experiment (#817)

See https://github.com/ooni/probe/issues/2124

internal/engine/experiment/tlsmiddlebox/trace.go

@@ -0,0 +1,54 @@
+package tlsmiddlebox
+
+import (
+	"sync"
+
+	"github.com/ooni/probe-cli/v3/internal/model"
+	"github.com/ooni/probe-cli/v3/internal/tracex"
+)
+
+// CompleteTrace records the result of the network trace
+// using a control SNI and a target SNI
+type CompleteTrace struct {
+	Address      string          `json:"address"`
+	ControlTrace *IterativeTrace `json:"control_trace"`
+	TargetTrace  *IterativeTrace `json:"target_trace"`
+}
+
+// Trace is an iterative trace for the corresponding servername and address
+type IterativeTrace struct {
+	SNI        string       `json:"server_name"`
+	Iterations []*Iteration `json:"iterations"`
+
+	mu sync.Mutex
+}
+
+// Iteration is a single network iteration with variable TTL
+type Iteration struct {
+	TTL       int                                     `json:"ttl"`
+	Handshake *model.ArchivalTLSOrQUICHandshakeResult `json:"handshake"`
+}
+
+// NewIterationFromHandshake returns a new iteration from a model.ArchivalTLSOrQUICHandshakeResult
+func newIterationFromHandshake(ttl int, err error, soErr error, handshake *model.ArchivalTLSOrQUICHandshakeResult) *Iteration {
+	if err != nil {
+		return &Iteration{
+			TTL: ttl,
+			Handshake: &model.ArchivalTLSOrQUICHandshakeResult{
+				Failure: tracex.NewFailure(err),
+			},
+		}
+	}
+	handshake.SoError = tracex.NewFailure(soErr)
+	return &Iteration{
+		TTL:       ttl,
+		Handshake: handshake,
+	}
+}
+
+// addIterations adds iterations to the trace
+func (t *IterativeTrace) addIterations(ev ...*Iteration) {
+	t.mu.Lock()
+	t.Iterations = append(t.Iterations, ev...)
+	t.mu.Unlock()
+}