Add candidate_number dial stat field

psiphon/controller.go

@@ -1468,7 +1468,8 @@ func (controller *Controller) doFetchTactics(
 		canReplay,
 		selectProtocol,
 		serverEntry,
-		true)
+		true,
+		0)
 	if dialParams == nil {
 		// MakeDialParameters may return nil, nil when the server entry can't
 		// satisfy protocol selection criteria. This case in not expected
@@ -1808,7 +1809,8 @@ loop:
 			canReplay,
 			selectProtocol,
 			candidateServerEntry.serverEntry,
-			false)
+			false,
+			controller.establishConnectTunnelCount)
 		if dialParams == nil || err != nil {
 
 			controller.concurrentEstablishTunnelsMutex.Unlock()

psiphon/dialParameters.go

@@ -54,9 +54,10 @@ import (
 //
 // DialParameters is not safe for concurrent use.
 type DialParameters struct {
-	ServerEntry *protocol.ServerEntry `json:"-"`
-	NetworkID   string                `json:"-"`
-	IsReplay    bool                  `json:"-"`
+	ServerEntry     *protocol.ServerEntry `json:"-"`
+	NetworkID       string                `json:"-"`
+	IsReplay        bool                  `json:"-"`
+	CandidateNumber int                   `json:"-"`
 
 	LastUsedTimestamp       time.Time
 	LastUsedConfigStateHash []byte
@@ -131,7 +132,8 @@ func MakeDialParameters(
 	canReplay func(serverEntry *protocol.ServerEntry, replayProtocol string) bool,
 	selectProtocol func(serverEntry *protocol.ServerEntry) (string, bool),
 	serverEntry *protocol.ServerEntry,
-	isTactics bool) (*DialParameters, error) {
+	isTactics bool,
+	candidateNumber int) (*DialParameters, error) {
 
 	networkID := config.GetNetworkID()
 
@@ -217,6 +219,7 @@ func MakeDialParameters(
 	dialParams.ServerEntry = serverEntry
 	dialParams.NetworkID = networkID
 	dialParams.IsReplay = isReplay
+	dialParams.CandidateNumber = candidateNumber
 
 	// Even when replaying, LastUsedTimestamp is updated to extend the TTL of
 	// replayed dial parameters which will be updated in the datastore upon

psiphon/dialParameters_test.go

@@ -111,7 +111,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 
 	// Test: expected dial parameter fields set
 
-	dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -196,7 +196,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 
 	dialParams.Failed()
 
-	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -211,7 +211,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 
 	testNetworkID = prng.HexString(8)
 
-	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -228,7 +228,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 
 	dialParams.Succeeded()
 
-	replayDialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	replayDialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -314,7 +314,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 		t.Fatalf("SetClientParameters failed: %s", err)
 	}
 
-	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -329,7 +329,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 
 	time.Sleep(1 * time.Second)
 
-	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -344,7 +344,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 
 	serverEntries[0].ConfigurationVersion += 1
 
-	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -368,14 +368,14 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 		t.Fatalf("SetClientParameters failed: %s", err)
 	}
 
-	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	dialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
 
 	dialParams.Succeeded()
 
-	replayDialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false)
+	replayDialParams, err = MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntries[0], false, 0)
 	if err != nil {
 		t.Fatalf("MakeDialParameters failed: %s", err)
 	}
@@ -423,7 +423,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 
 		if i%10 == 0 {
 
-			dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntry, false)
+			dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntry, false, 0)
 			if err != nil {
 				t.Fatalf("MakeDialParameters failed: %s", err)
 			}
@@ -452,7 +452,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 				t.Fatalf("ServerEntryIterator.Next failed: %s", err)
 			}
 
-			dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntry, false)
+			dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntry, false, 0)
 			if err != nil {
 				t.Fatalf("MakeDialParameters failed: %s", err)
 			}
@@ -474,7 +474,7 @@ func runDialParametersAndReplay(t *testing.T, tunnelProtocol string) {
 				t.Fatalf("ServerEntryIterator.Next failed: %s", err)
 			}
 
-			dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntry, false)
+			dialParams, err := MakeDialParameters(clientConfig, canReplay, selectProtocol, serverEntry, false, 0)
 			if err != nil {
 				t.Fatalf("MakeDialParameters failed: %s", err)
 			}

psiphon/server/api.go

@@ -632,16 +632,17 @@ var baseRequestParams = []requestParamSpec{
 	{"dial_port_number", isIntString, requestParamOptional | requestParamLogStringAsInt},
 	{"quic_version", isAnyString, requestParamOptional},
 	{"quic_dial_sni_address", isAnyString, requestParamOptional},
-	{"padding", isAnyString, requestParamOptional | requestParamLogStringLengthAsInt},
-	{"pad_response", isIntString, requestParamOptional | requestParamLogStringAsInt},
-	{"is_replay", isBooleanFlag, requestParamOptional | requestParamLogFlagAsBool},
-	{"egress_region", isRegionCode, requestParamOptional},
-	{"dial_duration", isIntString, requestParamOptional | requestParamLogStringAsInt},
 	{"upstream_bytes_fragmented", isIntString, requestParamOptional | requestParamLogStringAsInt},
 	{"upstream_min_bytes_written", isIntString, requestParamOptional | requestParamLogStringAsInt},
 	{"upstream_max_bytes_written", isIntString, requestParamOptional | requestParamLogStringAsInt},
 	{"upstream_min_delayed", isIntString, requestParamOptional | requestParamLogStringAsInt},
 	{"upstream_max_delayed", isIntString, requestParamOptional | requestParamLogStringAsInt},
+	{"padding", isAnyString, requestParamOptional | requestParamLogStringLengthAsInt},
+	{"pad_response", isIntString, requestParamOptional | requestParamLogStringAsInt},
+	{"is_replay", isBooleanFlag, requestParamOptional | requestParamLogFlagAsBool},
+	{"egress_region", isRegionCode, requestParamOptional},
+	{"dial_duration", isIntString, requestParamOptional | requestParamLogStringAsInt},
+	{"candidate_number", isIntString, requestParamOptional | requestParamLogStringAsInt},
 }
 
 func validateRequestParams(

psiphon/serverApi.go

@@ -821,6 +821,8 @@ func getBaseAPIParameters(
 	// dialParams.DialDuration is nanoseconds; divide to get to milliseconds
 	params["dial_duration"] = fmt.Sprintf("%d", dialParams.DialDuration/1000000)
 
+	params["candidate_number"] = strconv.Itoa(dialParams.CandidateNumber)
+
 	if dialParams.DialConnMetrics != nil {
 		metrics := dialParams.DialConnMetrics.GetMetrics()
 		for name, value := range metrics {