From 21133e185617ca092a761c04e102747036b1cc24 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Wed, 31 Jul 2019 19:59:32 -0700
Subject: [PATCH] channeldb: define new channel type, SingleFunderTweakless

In this commit, we define a new channel type: SingleFunderTweakless.
We'll use this channel type to denote channels with commitments that
don't tweak the remote party's key in their non-delay output.
---
 channeldb/channel.go | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/channeldb/channel.go b/channeldb/channel.go
index 8b5d5253b..fefd27404 100644
--- a/channeldb/channel.go
+++ b/channeldb/channel.go
@@ -135,14 +135,31 @@ const (
 
 	// SingleFunder represents a channel wherein one party solely funds the
 	// entire capacity of the channel.
-	SingleFunder = 0
+	SingleFunder ChannelType = 0
 
 	// 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 = 1
+	DualFunder ChannelType = 1
+
+	// SingleFunderTweakless is similar to the basic SingleFunder channel
+	// type, but it omits the tweak for one's key in the commitment
+	// transaction of the remote party.
+	SingleFunderTweakless ChannelType = 2
 )
 
+// IsSingleFunder returns true if the channel type if one of the known single
+// funder variants.
+func (c ChannelType) IsSingleFunder() bool {
+	return c == SingleFunder || c == SingleFunderTweakless
+}
+
+// IsTweakless returns true if the target channel uses a commitment that
+// doesn't tweak the key for the remote party.
+func (c ChannelType) IsTweakless() bool {
+	return c == SingleFunderTweakless
+}
+
 // ChannelConstraints represents a set of constraints meant to allow a node to
 // limit their exposure, enact flow control and ensure that all HTLCs are
 // economically relevant. This struct will be mirrored for both sides of the
@@ -2506,7 +2523,7 @@ func putChanInfo(chanBucket *bbolt.Bucket, channel *OpenChannel) error {
 	}
 
 	// For single funder channels that we initiated, write the funding txn.
-	if channel.ChanType == SingleFunder && channel.IsInitiator &&
+	if channel.ChanType.IsSingleFunder() && channel.IsInitiator &&
 		!channel.hasChanStatus(ChanStatusRestored) {
 
 		if err := WriteElement(&w, channel.FundingTxn); err != nil {
@@ -2628,7 +2645,7 @@ func fetchChanInfo(chanBucket *bbolt.Bucket, channel *OpenChannel) error {
 	}
 
 	// For single funder channels that we initiated, read the funding txn.
-	if channel.ChanType == SingleFunder && channel.IsInitiator &&
+	if channel.ChanType.IsSingleFunder() && channel.IsInitiator &&
 		!channel.hasChanStatus(ChanStatusRestored) {
 
 		if err := ReadElement(r, &channel.FundingTxn); err != nil {