routing: prune channels with disabled bit set on both edges

In this commit, we add an additional heuristic when running with
AssumeChannelValid. Since AssumeChannelValid being present assumes that
we're not able to quickly determine whether channels are valid, we also
assume that any channels with the disabled bit set on both sides are
considered zombie. This should be relatively safe to do, since the
disabled bits are usually set when the channel is closed on-chain. In
the case that they aren't, we'll have to wait until both edges haven't
had a new update within two weeks to prune them.

routing/pathfind_test.go

@@ -305,6 +305,7 @@ type testChannelPolicy struct {
 	FeeBaseMsat lnwire.MilliSatoshi
 	FeeRate     lnwire.MilliSatoshi
 	LastUpdate  time.Time
+	Disabled    bool
 }
 
 type testChannelEnd struct {
@@ -322,6 +323,7 @@ func defaultTestChannelEnd(alias string, capacity btcutil.Amount) *testChannelEn
 			FeeBaseMsat: lnwire.MilliSatoshi(1000),
 			FeeRate:     lnwire.MilliSatoshi(1),
 			LastUpdate:  testTime,
+			Disabled:    false,
 		},
 	}
 }
@@ -496,12 +498,16 @@ func createTestGraphFromChannels(testChannels []*testChannel) (*testGraphInstanc
 		if testChannel.Node1.testChannelPolicy != nil {
 			var msgFlags lnwire.ChanUpdateMsgFlags
 			if testChannel.Node1.MaxHTLC != 0 {
-				msgFlags = 1
+				msgFlags |= lnwire.ChanUpdateOptionMaxHtlc
+			}
+			var channelFlags lnwire.ChanUpdateChanFlags
+			if testChannel.Node1.Disabled {
+				channelFlags |= lnwire.ChanUpdateDisabled
 			}
 			edgePolicy := &channeldb.ChannelEdgePolicy{
 				SigBytes:                  testSig.Serialize(),
 				MessageFlags:              msgFlags,
-				ChannelFlags:              0,
+				ChannelFlags:              channelFlags,
 				ChannelID:                 channelID,
 				LastUpdate:                testChannel.Node1.LastUpdate,
 				TimeLockDelta:             testChannel.Node1.Expiry,
@@ -518,12 +524,16 @@ func createTestGraphFromChannels(testChannels []*testChannel) (*testGraphInstanc
 		if testChannel.Node2.testChannelPolicy != nil {
 			var msgFlags lnwire.ChanUpdateMsgFlags
 			if testChannel.Node2.MaxHTLC != 0 {
-				msgFlags = 1
+				msgFlags |= lnwire.ChanUpdateOptionMaxHtlc
+			}
+			channelFlags := lnwire.ChanUpdateDirection
+			if testChannel.Node2.Disabled {
+				channelFlags |= lnwire.ChanUpdateDisabled
 			}
 			edgePolicy := &channeldb.ChannelEdgePolicy{
 				SigBytes:                  testSig.Serialize(),
 				MessageFlags:              msgFlags,
-				ChannelFlags:              lnwire.ChanUpdateDirection,
+				ChannelFlags:              channelFlags,
 				ChannelID:                 channelID,
 				LastUpdate:                testChannel.Node2.LastUpdate,
 				TimeLockDelta:             testChannel.Node2.Expiry,