feature: add new feature pkg to manage feature sets

This commit introduces a feature.Manager, which derives feature vectors
for various contexts within the daemon. The sets can be described via a
staticly compiled format, which makes any runtime adjustments to the
feature sets when the manager is initialized.

feature/manager_internal_test.go

@@ -0,0 +1,128 @@
+package feature
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+type managerTest struct {
+	name string
+	cfg  Config
+}
+
+const unknownFeature lnwire.FeatureBit = 30
+
+var testSetDesc = setDesc{
+	lnwire.DataLossProtectRequired: {
+		SetNodeAnn: {}, // I
+	},
+	lnwire.TLVOnionPayloadOptional: {
+		SetInit:    {}, // I
+		SetNodeAnn: {}, // N
+	},
+	lnwire.StaticRemoteKeyOptional: {
+		SetInit:    {}, // I
+		SetNodeAnn: {}, // N
+	},
+}
+
+var managerTests = []managerTest{
+	{
+		name: "default",
+		cfg:  Config{},
+	},
+	{
+		name: "no tlv",
+		cfg: Config{
+			NoTLVOnion: true,
+		},
+	},
+	{
+		name: "no static remote key",
+		cfg: Config{
+			NoStaticRemoteKey: true,
+		},
+	},
+	{
+		name: "no tlv or static remote key",
+		cfg: Config{
+			NoTLVOnion:        true,
+			NoStaticRemoteKey: true,
+		},
+	},
+}
+
+// TestManager asserts basic initialazation and operation of a feature manager,
+// including that the proper features are removed in response to config changes.
+func TestManager(t *testing.T) {
+	for _, test := range managerTests {
+		test := test
+		t.Run(test.name, func(t *testing.T) {
+			testManager(t, test)
+		})
+	}
+}
+
+func testManager(t *testing.T, test managerTest) {
+	m, err := newManager(test.cfg, testSetDesc)
+	if err != nil {
+		t.Fatalf("unable to create feature manager: %v", err)
+	}
+
+	sets := []Set{
+		SetInit,
+		SetLegacyGlobal,
+		SetNodeAnn,
+		SetInvoice,
+	}
+
+	for _, set := range sets {
+		raw := m.GetRaw(set)
+		fv := m.Get(set)
+
+		fv2 := lnwire.NewFeatureVector(raw, lnwire.Features)
+
+		if !reflect.DeepEqual(fv, fv2) {
+			t.Fatalf("mismatch Get vs GetRaw, raw: %v vs fv: %v",
+				fv2, fv)
+		}
+
+		assertUnset := func(bit lnwire.FeatureBit) {
+			hasBit := fv.HasFeature(bit) || fv.HasFeature(bit^1)
+			if hasBit {
+				t.Fatalf("bit %v or %v is set", bit, bit^1)
+			}
+		}
+
+		// Assert that the manager properly unset the configured feature
+		// bits from all sets.
+		if test.cfg.NoTLVOnion {
+			assertUnset(lnwire.TLVOnionPayloadOptional)
+		}
+		if test.cfg.NoStaticRemoteKey {
+			assertUnset(lnwire.StaticRemoteKeyOptional)
+		}
+
+		assertUnset(unknownFeature)
+	}
+
+	// Do same basic sanity checks on features that are always present.
+	nodeFeatures := m.Get(SetNodeAnn)
+
+	assertSet := func(bit lnwire.FeatureBit) {
+		has := nodeFeatures.HasFeature(bit)
+		if !has {
+			t.Fatalf("node features don't advertised %v", bit)
+		}
+	}
+
+	assertSet(lnwire.DataLossProtectOptional)
+	if !test.cfg.NoTLVOnion {
+		assertSet(lnwire.TLVOnionPayloadRequired)
+	}
+	if !test.cfg.NoStaticRemoteKey {
+		assertSet(lnwire.StaticRemoteKeyOptional)
+	}
+}