fix(traffic): keep client accounting independent of outbound counters

The traffic poll read every Xray counter in one QueryStats reply under
gRPC's default 4 MiB receive limit; past it the whole poll failed and
no client was counted, so quotas stopped being enforced. Outbound
counters carry tags derived from third-party link remarks, so one long
remark was enough.

Poll the user, inbound and outbound families separately with a 64 MiB
limit, keep counting the families that answer, and cap a subscription
link's slug at 64 runes so the tag stays small to begin with.

internal/xray/api_traffic_test.go

@@ -3,10 +3,13 @@ package xray
 import (
 	"context"
 	"net"
+	"strings"
 	"testing"
 
 	statsService "github.com/xtls/xray-core/app/stats/command"
 	"google.golang.org/grpc"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
 )
 
 // fakeStatsServer serves a scripted sequence of QueryStats responses, one per
@@ -14,16 +17,28 @@ import (
 type fakeStatsServer struct {
 	statsService.UnimplementedStatsServiceServer
 	rounds [][]*statsService.Stat
-	calls  int
+	calls  map[string]int
+	fail   map[string]error
 }
 
-func (f *fakeStatsServer) QueryStats(context.Context, *statsService.QueryStatsRequest) (*statsService.QueryStatsResponse, error) {
-	round := f.calls
-	f.calls++
+// QueryStats answers each pattern from its own round counter and, like the core, matches
+// the pattern anywhere in the name.
+func (f *fakeStatsServer) QueryStats(_ context.Context, req *statsService.QueryStatsRequest) (*statsService.QueryStatsResponse, error) {
+	if err := f.fail[req.Pattern]; err != nil {
+		return nil, err
+	}
+	round := f.calls[req.Pattern]
+	f.calls[req.Pattern]++
 	if round >= len(f.rounds) {
 		round = len(f.rounds) - 1
 	}
-	return &statsService.QueryStatsResponse{Stat: f.rounds[round]}, nil
+	var matched []*statsService.Stat
+	for _, s := range f.rounds[round] {
+		if strings.Contains(s.Name, req.Pattern) {
+			matched = append(matched, s)
+		}
+	}
+	return &statsService.QueryStatsResponse{Stat: matched}, nil
 }
 
 func stat(name string, value int64) *statsService.Stat {
@@ -34,12 +49,18 @@ func stat(name string, value int64) *statsService.Stat {
 // to it.
 func startFakeStats(t *testing.T, rounds [][]*statsService.Stat) *XrayAPI {
 	t.Helper()
+	return startFakeStatsServer(t, &fakeStatsServer{rounds: rounds})
+}
+
+func startFakeStatsServer(t *testing.T, fake *fakeStatsServer) *XrayAPI {
+	t.Helper()
+	fake.calls = map[string]int{}
 	lis, err := net.Listen("tcp", "127.0.0.1:0")
 	if err != nil {
 		t.Fatal(err)
 	}
 	srv := grpc.NewServer()
-	statsService.RegisterStatsServiceServer(srv, &fakeStatsServer{rounds: rounds})
+	statsService.RegisterStatsServiceServer(srv, fake)
 	go func() { _ = srv.Serve(lis) }()
 	t.Cleanup(srv.Stop)
 
@@ -190,3 +211,29 @@ func TestGetTrafficSkipsAPIInboundAndPrunes(t *testing.T) {
 		t.Fatal("baselines for stats that no longer exist were not pruned")
 	}
 }
+
+// Outbound counters are named after subscription tags a third party chooses; however
+// large that family's reply grows, the clients' counters must still be counted.
+func TestGetTrafficCountsClientsPastAnOversizedOutboundFamily(t *testing.T) {
+	huge := stat("outbound>>>"+strings.Repeat("x", 5<<20)+">>>traffic>>>uplink", 1)
+	rounds := [][]*statsService.Stat{
+		{stat("user>>>alice>>>traffic>>>uplink", 100), huge},
+		{stat("user>>>alice>>>traffic>>>uplink", 400), huge},
+	}
+	for name, fake := range map[string]*fakeStatsServer{
+		"reply over gRPC's default limit": {rounds: rounds},
+		"family that fails":               {rounds: rounds, fail: map[string]error{"outbound>>>": status.Error(codes.ResourceExhausted, "too large")}},
+	} {
+		api := startFakeStatsServer(t, fake)
+		if _, _, err := api.GetTraffic(); err != nil {
+			t.Fatalf("%s: GetTraffic (baseline): %v", name, err)
+		}
+		_, clients, err := api.GetTraffic()
+		if err != nil {
+			t.Fatalf("%s: GetTraffic: %v", name, err)
+		}
+		if alice := clientTrafficByEmail(t, clients)["alice"]; alice == nil || alice.Up != 300 {
+			t.Fatalf("%s: alice = %+v, want 300 bytes up", name, alice)
+		}
+	}
+}