lnwallet: add log message for edge case

also see discussion in #7108

docs/release-notes/release-notes-0.16.0.md

@@ -115,6 +115,9 @@ current gossip sync query status.
 * [Fix the issue of ghost UTXOs not being detected as spent if they were created
   with an external tool](https://github.com/lightningnetwork/lnd/pull/7243).
 
+* [Add log message for edge
+  case](https://github.com/lightningnetwork/lnd/pull/7115).
+
 ## Build
 
 [The project has updated to Go
@@ -357,6 +360,7 @@ refactor the itest for code health and maintenance.
 * andreihod
 * Antoni Spaanderman
 * Carla Kirk-Cohen
+* Carsten Otto
 * Conner Babinchak
 * cutiful
 * Daniel McNally

lnwallet/channel.go

@@ -7031,7 +7031,14 @@ func (lc *LightningChannel) availableCommitmentBalance(view *htlcView,
 	// report our available balance just below the non-dust amount, to
 	// avoid attempting HTLCs larger than this size.
 	if theirBalance < htlcCommitFee && ourBalance >= nonDustHtlcAmt {
-		ourBalance = nonDustHtlcAmt - 1
+		// see https://github.com/lightning/bolts/issues/728
+		ourReportedBalance := nonDustHtlcAmt - 1
+		lc.log.Infof("Reducing local balance (from %v to %v): "+
+			"remote side does not have enough funds (%v < %v) to "+
+			"pay for non-dust HTLC in case of unilateral close.",
+			ourBalance, ourReportedBalance, theirBalance,
+			htlcCommitFee)
+		ourBalance = ourReportedBalance
 	}
 
 	return ourBalance, commitWeight