From 56c07a52d84f60123078ca6e68755dbd680a1588 Mon Sep 17 00:00:00 2001
From: nsa <elzeigel@gmail.com>
Date: Sat, 15 Feb 2020 09:45:25 -0500
Subject: [PATCH] lnwallet: call valdiateCommitmentSanity in ReceiveHTLC

This commit checks the commitment sanity when receiving an HTLC so
that if a commitment transaction will overflow from an ADD, it is
caught earlier rather than in ReceiveNewCommitment.
---
 lnwallet/channel.go | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/lnwallet/channel.go b/lnwallet/channel.go
index 131d8632..92bf538c 100644
--- a/lnwallet/channel.go
+++ b/lnwallet/channel.go
@@ -3084,12 +3084,16 @@ func (lc *LightningChannel) validateCommitmentSanity(theirLogCounter,
 	view := lc.fetchHTLCView(theirLogCounter, ourLogCounter)
 
 	// If we are checking if we can add a new HTLC, we add this to the
-	// update log, in order to validate the sanity of the commitment
-	// resulting from _actually adding_ this HTLC to the state.
+	// appropriate update log, in order to validate the sanity of the
+	// commitment resulting from _actually adding_ this HTLC to the state.
 	if predictAdded != nil {
-		// If we are adding an HTLC, this will be an Add to the local
-		// update log.
-		view.ourUpdates = append(view.ourUpdates, predictAdded)
+		// If the remoteChain bool is true, add to ourUpdates.
+		if remoteChain {
+			view.ourUpdates = append(view.ourUpdates, predictAdded)
+		} else {
+			// Else add to theirUpdates.
+			view.theirUpdates = append(view.theirUpdates, predictAdded)
+		}
 	}
 
 	commitChain := lc.localCommitChain
@@ -4640,6 +4644,17 @@ func (lc *LightningChannel) ReceiveHTLC(htlc *lnwire.UpdateAddHTLC) (uint64, err
 		OnionBlob: htlc.OnionBlob[:],
 	}
 
+	localACKedIndex := lc.remoteCommitChain.tail().ourMessageIndex
+
+	// Clamp down on the number of HTLC's we can receive by checking the
+	// commitment sanity.
+	err := lc.validateCommitmentSanity(
+		lc.remoteUpdateLog.logIndex, localACKedIndex, false, pd,
+	)
+	if err != nil {
+		return 0, err
+	}
+
 	lc.remoteUpdateLog.appendHtlc(pd)
 
 	return pd.HtlcIndex, nil