channeldb: add TheirDustLimit and OurDustLimit fields in OpenChannel

channeldb/channel.go

@@ -57,14 +57,16 @@ var (
 	// sequential prefix scans, and second to eliminate write amplification
 	// caused by serializing/deserializing the *entire* struct with each
 	// update.
-	chanCapacityPrefix = []byte("ccp")
-	selfBalancePrefix  = []byte("sbp")
-	theirBalancePrefix = []byte("tbp")
-	minFeePerKbPrefix  = []byte("mfp")
-	updatePrefix       = []byte("uup")
-	satSentPrefix      = []byte("ssp")
-	satReceivedPrefix  = []byte("srp")
-	netFeesPrefix      = []byte("ntp")
+	chanCapacityPrefix   = []byte("ccp")
+	selfBalancePrefix    = []byte("sbp")
+	theirBalancePrefix   = []byte("tbp")
+	minFeePerKbPrefix    = []byte("mfp")
+	theirDustLimitPrefix = []byte("tdlp")
+	ourDustLimitPrefix   = []byte("odlp")
+	updatePrefix         = []byte("uup")
+	satSentPrefix        = []byte("ssp")
+	satReceivedPrefix    = []byte("srp")
+	netFeesPrefix        = []byte("ntp")
 
 	// chanIDKey stores the node, and channelID for an active channel.
 	chanIDKey = []byte("cik")
@@ -138,6 +140,16 @@ type OpenChannel struct {
 	// channel as on-chain conditions change.
 	MinFeePerKb btcutil.Amount
 
+	// TheirDustLimit is the threshold below which no HTLC output should be
+	// generated for their commitment transaction; ie. HTLCs below
+	// this amount are not enforceable onchain from their point of view.
+	TheirDustLimit btcutil.Amount
+
+	// OurDustLimit is the threshold below which no HTLC output should be
+	// generated for our commitment transaction; ie. HTLCs below
+	// this amount are not enforceable onchain from out point of view.
+	OurDustLimit btcutil.Amount
+
 	// OurCommitKey is the key to be used within our commitment transaction
 	// to generate the scripts for outputs paying to ourself, and
 	// revocation clauses.
@@ -674,6 +686,12 @@ func putOpenChannel(openChanBucket *bolt.Bucket, nodeChanBucket *bolt.Bucket,
 	if err := putChanMinFeePerKb(openChanBucket, channel); err != nil {
 		return err
 	}
+	if err := putChanTheirDustLimit(openChanBucket, channel); err != nil {
+		return err
+	}
+	if err := putChanOurDustLimit(openChanBucket, channel); err != nil {
+		return err
+	}
 	if err := putChanNumUpdates(openChanBucket, channel); err != nil {
 		return err
 	}
@@ -751,6 +769,12 @@ func fetchOpenChannel(openChanBucket *bolt.Bucket, nodeChanBucket *bolt.Bucket,
 	if err = fetchChanMinFeePerKb(openChanBucket, channel); err != nil {
 		return nil, err
 	}
+	if err = fetchChanTheirDustLimit(openChanBucket, channel); err != nil {
+		return nil, err
+	}
+	if err = fetchChanOurDustLimit(openChanBucket, channel); err != nil {
+		return nil, err
+	}
 	if err = fetchChanNumUpdates(openChanBucket, channel); err != nil {
 		return nil, err
 	}
@@ -893,6 +917,38 @@ func putChanMinFeePerKb(openChanBucket *bolt.Bucket, channel *OpenChannel) error
 	return openChanBucket.Put(keyPrefix, scratch)
 }
 
+func putChanTheirDustLimit(openChanBucket *bolt.Bucket, channel *OpenChannel) error {
+	scratch := make([]byte, 8)
+	byteOrder.PutUint64(scratch, uint64(channel.TheirDustLimit))
+
+	var b bytes.Buffer
+	if err := writeOutpoint(&b, channel.ChanID); err != nil {
+		return err
+	}
+
+	keyPrefix := make([]byte, 3+b.Len())
+	copy(keyPrefix, theirDustLimitPrefix)
+	copy(keyPrefix[3:], b.Bytes())
+
+	return openChanBucket.Put(keyPrefix, scratch)
+}
+
+func putChanOurDustLimit(openChanBucket *bolt.Bucket, channel *OpenChannel) error {
+	scratch := make([]byte, 8)
+	byteOrder.PutUint64(scratch, uint64(channel.OurDustLimit))
+
+	var b bytes.Buffer
+	if err := writeOutpoint(&b, channel.ChanID); err != nil {
+		return err
+	}
+
+	keyPrefix := make([]byte, 3+b.Len())
+	copy(keyPrefix, ourDustLimitPrefix)
+	copy(keyPrefix[3:], b.Bytes())
+
+	return openChanBucket.Put(keyPrefix, scratch)
+}
+
 func deleteChanMinFeePerKb(openChanBucket *bolt.Bucket, chanID []byte) error {
 	keyPrefix := make([]byte, 3+len(chanID))
 	copy(keyPrefix, minFeePerKbPrefix)
@@ -916,6 +972,38 @@ func fetchChanMinFeePerKb(openChanBucket *bolt.Bucket, channel *OpenChannel) err
 	return nil
 }
 
+func fetchChanTheirDustLimit(openChanBucket *bolt.Bucket, channel *OpenChannel) error {
+	var b bytes.Buffer
+	if err := writeOutpoint(&b, channel.ChanID); err != nil {
+		return err
+	}
+
+	keyPrefix := make([]byte, 3+b.Len())
+	copy(keyPrefix, theirDustLimitPrefix)
+	copy(keyPrefix[3:], b.Bytes())
+
+	dustLimitBytes := openChanBucket.Get(keyPrefix)
+	channel.TheirDustLimit = btcutil.Amount(byteOrder.Uint64(dustLimitBytes))
+
+	return nil
+}
+
+func fetchChanOurDustLimit(openChanBucket *bolt.Bucket, channel *OpenChannel)error {
+	var b bytes.Buffer
+	if err := writeOutpoint(&b, channel.ChanID); err != nil {
+		return err
+	}
+
+	keyPrefix := make([]byte, 3+b.Len())
+	copy(keyPrefix, ourDustLimitPrefix)
+	copy(keyPrefix[3:], b.Bytes())
+
+	dustLimitBytes := openChanBucket.Get(keyPrefix)
+	channel.OurDustLimit = btcutil.Amount(byteOrder.Uint64(dustLimitBytes))
+
+	return nil
+}
+
 func putChanNumUpdates(openChanBucket *bolt.Bucket, channel *OpenChannel) error {
 	scratch := make([]byte, 8)
 	byteOrder.PutUint64(scratch, channel.NumUpdates)

channeldb/channel_test.go

@@ -140,6 +140,8 @@ func createTestChannelState(cdb *DB) (*OpenChannel, error) {
 		IdentityPub:                pubKey,
 		ChanID:                     id,
 		MinFeePerKb:                btcutil.Amount(5000),
+		TheirDustLimit:             btcutil.Amount(200),
+		OurDustLimit:               btcutil.Amount(200),
 		OurCommitKey:               privKey.PubKey(),
 		TheirCommitKey:             pubKey,
 		Capacity:                   btcutil.Amount(10000),
@@ -182,7 +184,7 @@ func TestOpenChannelPutGetDelete(t *testing.T) {
 		t.Fatalf("unable to create channel state: %v", err)
 	}
 	state.Htlcs = []*HTLC{
-		&HTLC{
+		{
 			Incoming:        true,
 			Amt:             10,
 			RHash:           key,
@@ -212,6 +214,12 @@ func TestOpenChannelPutGetDelete(t *testing.T) {
 	if state.MinFeePerKb != newState.MinFeePerKb {
 		t.Fatalf("fee/kb doesn't match")
 	}
+	if state.TheirDustLimit != newState.TheirDustLimit {
+		t.Fatalf("their dust limit doesn't match")
+	}
+	if state.OurDustLimit != newState.OurDustLimit {
+		t.Fatalf("our dust limit doesn't match")
+	}
 	if state.IsInitiator != newState.IsInitiator {
 		t.Fatalf("initiator status doesn't match")
 	}

lnwallet/parameters.go

@@ -0,0 +1,12 @@
+package lnwallet
+
+import (
+	"github.com/roasbeef/btcwallet/wallet/txrules"
+	"github.com/roasbeef/btcutil"
+)
+
+// DefaultDustLimit is used to calculate the dust HTLC amount which will be
+// proposed to other node during channel creation.
+func DefaultDustLimit() btcutil.Amount {
+	return txrules.GetDustThreshold(P2WSHSize, txrules.DefaultRelayFeePerKb)
+}