multi: expose local and remote spendable balance in listchannels

docs/release-notes/release-notes-0.20.1.md

@@ -103,6 +103,13 @@
    for conservative budgeting and includes griefing protection by limiting the
    number of probed LSPs. It enhances the previous LSP design by being more
    generic and more flexible.
+
+ * The `listchannels` RPC now [exposes the actual 
+   spendable balance](https://github.com/lightningnetwork/lnd/pull/10624)
+   by adding `local_spendable_balance` and `remote_spendable_balance` fields. 
+   This provides users with a precise view of their actionable liquidity by 
+   correctly accounting for channel reserves and funds currently tied up in 
+   in-flight HTLCs.
 
 ## lncli Updates
 

htlcswitch/interfaces.go

@@ -128,11 +128,17 @@ type ChannelUpdateHandler interface {
 
 	// Bandwidth returns the amount of milli-satoshis which current link
 	// might pass through channel link. The value returned from this method
-	// represents the up to date available flow through the channel. This
-	// takes into account any forwarded but un-cleared HTLC's, and any
-	// HTLC's which have been set to the over flow queue.
+	// represents the up to date available flow through the channel for the
+	// local party. This takes into account any forwarded but un-cleared
+	// HTLC's, and any HTLC's which have been set to the over flow queue.
 	Bandwidth() lnwire.MilliSatoshi
 
+	// RemoteBandwidth returns the amount of milli-satoshis which the remote
+	// party can send through the channel. Similar to Bandwidth(), it takes
+	// into account reserves and commitment fees from the remote's
+	// perspective.
+	RemoteBandwidth() lnwire.MilliSatoshi
+
 	// EligibleToForward returns a bool indicating if the channel is able
 	// to actively accept requests to forward HTLC's. A channel may be
 	// active, but not able to forward HTLC's if it hasn't yet finalized

htlcswitch/link.go

@@ -2149,6 +2149,15 @@ func (l *channelLink) Bandwidth() lnwire.MilliSatoshi {
 	return l.channel.AvailableBalance()
 }
 
+// RemoteBandwidth returns the total amount that the remote party can send
+// through the channel link at this given instance. The value returned is
+// expressed in millisatoshi.
+//
+// NOTE: Part of the ChannelLink interface.
+func (l *channelLink) RemoteBandwidth() lnwire.MilliSatoshi {
+	return l.channel.RemoteAvailableBalance()
+}
+
 // MayAddOutgoingHtlc indicates whether we can add an outgoing htlc with the
 // amount provided to the link. This check does not reserve a space, since
 // forwards or other payments may use the available slot, so it should be

htlcswitch/mock.go

@@ -167,7 +167,9 @@ type mockServer struct {
 
 var _ lnpeer.Peer = (*mockServer)(nil)
 
-func initSwitchWithDB(startingHeight uint32, db *channeldb.DB) (*Switch, error) {
+func initSwitchWithDB(startingHeight uint32, db *channeldb.DB) (
+	*Switch, error) {
+
 	signAliasUpdate := func(u *lnwire.ChannelUpdate1) (*ecdsa.Signature,
 		error) {
 
@@ -375,7 +377,8 @@ func encodeFwdInfo(w io.Writer, f *hop.ForwardingInfo) error {
 		return err
 	}
 
-	if err := binary.Write(w, binary.BigEndian, f.OutgoingCTLV); err != nil {
+	if err := binary.Write(
+		w, binary.BigEndian, f.OutgoingCTLV); err != nil {
 		return err
 	}
 
@@ -438,10 +441,11 @@ func (o *mockObfuscator) IntermediateEncrypt(reason lnwire.OpaqueReason) lnwire.
 	return reason
 }
 
-func (o *mockObfuscator) EncryptMalformedError(reason lnwire.OpaqueReason) lnwire.OpaqueReason {
+func (o *mockObfuscator) EncryptMalformedError(
+	reason lnwire.OpaqueReason) lnwire.OpaqueReason {
+
 	var b bytes.Buffer
 	b.Write(fakeHmac)
-
 	b.Write(reason)
 
 	return b.Bytes()
@@ -508,7 +512,9 @@ func (p *mockIteratorDecoder) DecodeHopIterator(r io.Reader, rHash []byte,
 		}
 
 		var nextHopBytes [8]byte
-		binary.BigEndian.PutUint64(nextHopBytes[:], f.NextHop.ToUint64())
+		binary.BigEndian.PutUint64(
+			nextHopBytes[:], f.NextHop.ToUint64(),
+		)
 
 		hops[i] = hop.NewLegacyPayload(&sphinx.HopData{
 			Realm:         [1]byte{}, // hop.BitcoinNetwork
@@ -569,7 +575,8 @@ func decodeFwdInfo(r io.Reader, f *hop.ForwardingInfo) error {
 		return err
 	}
 
-	if err := binary.Read(r, binary.BigEndian, &f.OutgoingCTLV); err != nil {
+	if err := binary.Read(
+		r, binary.BigEndian, &f.OutgoingCTLV); err != nil {
 		return err
 	}
 
@@ -910,10 +917,21 @@ func (f *mockChannelLink) ShortChanID() lnwire.ShortChannelID {
 	return f.shortChanID
 }
 
+// Bandwidth returns a hardcoded amount of milli-satoshis for the mock link.
+//
+// NOTE: Part of the ChannelLink interface.
 func (f *mockChannelLink) Bandwidth() lnwire.MilliSatoshi {
 	return 99999999
 }
 
+// RemoteBandwidth returns a hardcoded amount of milli-satoshis for
+// the mock link.
+//
+// NOTE: Part of the ChannelLink interface.
+func (f *mockChannelLink) RemoteBandwidth() lnwire.MilliSatoshi {
+	return 99999999
+}
+
 func (f *mockChannelLink) PeerPubKey() [33]byte {
 	return f.peer.PubKey()
 }