channeldb: store an enum indicating channel type in OpenChannel

This commit modifies the OpenChannel struct along with all related
persistent to additional store a single byte which indicates the exact
type of the channel. This may be useful in the future as higher level
behavior may change depending on the precise type of the channel.

channeldb/channel.go

@@ -95,6 +95,24 @@ var (
 	deliveryScriptsKey = []byte("dsk")
 )
 
+// ChannelType is an enum-like type that describes one of several possible
+// channel types. Each open channel is associated with a particular type as the
+// channel type may determine how higher level operations are conducted such as
+// fee negotiation, channel closing, the format of HTLC's, etc.
+// TODO(roasbeef): split up per-chain?
+type ChannelType uint8
+
+const (
+	// SingleFunder represents a channel wherein one party solely funds the
+	// entire capacity of the channel.
+	SingleFunder = iota
+
+	// DualFunder represents a channel wherein both parties contribute
+	// funds towards the total capacity of the channel. The channel may be
+	// funded symmetrically or asymmetrically.
+	DualFunder
+)
+
 // OpenChannel encapsulates the persistent and dynamic state of an open channel
 // with a remote node. An open channel supports several options for on-disk
 // serialization depending on the exact context. Full (upon channel creation)
@@ -127,6 +145,8 @@ type OpenChannel struct {
 	OurCommitSig []byte
 
 	// The outpoint of the final funding transaction.
+	// ChanType denotes which type of channel this is.
+	ChanType ChannelType
 	FundingOutpoint *wire.OutPoint
 
 	OurMultiSigKey       *btcec.PublicKey
@@ -1164,6 +1184,10 @@ func putChanFundingInfo(nodeChanBucket *bolt.Bucket, channel *OpenChannel) error
 		return err
 	}
 
+	if _, err := b.Write([]byte{uint8(channel.ChanType)}); err != nil {
+		return err
+	}
+
 	return nodeChanBucket.Put(fundTxnKey, b.Bytes())
 }
 
@@ -1221,6 +1245,12 @@ func fetchChanFundingInfo(nodeChanBucket *bolt.Bucket, channel *OpenChannel) err
 	unixSecs := byteOrder.Uint64(scratch)
 	channel.CreationTime = time.Unix(int64(unixSecs), 0)
 
+	var chanType [1]byte
+	if _, err := io.ReadFull(infoBytes, chanType[:]); err != nil {
+		return err
+	}
+	channel.ChanType = ChannelType(chanType[0])
+
 	return nil
 }
 

channeldb/channel_test.go

@@ -133,6 +133,7 @@ func createTestChannelState(cdb *DB) (*OpenChannel, error) {
 	}
 
 	return &OpenChannel{
+		ChanType:                   SingleFunder,
 		IdentityPub:                pubKey,
 		ChanID:                     id,
 		MinFeePerKb:                btcutil.Amount(5000),
@@ -207,6 +208,8 @@ func TestOpenChannelPutGetDelete(t *testing.T) {
 	}
 	if state.MinFeePerKb != newState.MinFeePerKb {
 		t.Fatalf("fee/kb doens't match")
+	if state.ChanType != newState.ChanType {
+		t.Fatalf("channel type doesn't match")
 	}
 
 	if !bytes.Equal(state.OurCommitKey.SerializeCompressed(),