From 7a491776a1eea596ec52b09c504f94547ef962a5 Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Thu, 3 Oct 2019 16:59:36 -0700
Subject: [PATCH] contractcourt: use legacy chain actions of commitSet not
 found

In this commit, we fix a bug that would prevent users that had
unresolved contracts at the time of update from starting their nodes.
Before we added the conf commit set, the information needed to
supplement the resolvers was found in the chain action map. As a result,
if the conf commit set is nil, then we also need to check this legacy
data to ensure that we can supplement the resolvers to the best of our
ability based on the available data.

Fixes #3549.
---
 contractcourt/channel_arbitrator.go | 32 +++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/contractcourt/channel_arbitrator.go b/contractcourt/channel_arbitrator.go
index 1789e775..3bd66902 100644
--- a/contractcourt/channel_arbitrator.go
+++ b/contractcourt/channel_arbitrator.go
@@ -426,8 +426,7 @@ func (c *ChannelArbitrator) Start() error {
 		// receive a chain event from the chain watcher than the
 		// commitment has been confirmed on chain, and before we
 		// advance our state step, we call InsertConfirmedCommitSet.
-		confCommitSet := commitSet.HtlcSets[*commitSet.ConfCommitKey]
-		if err := c.relaunchResolvers(confCommitSet); err != nil {
+		if err := c.relaunchResolvers(commitSet); err != nil {
 			c.cfg.BlockEpochs.Cancel()
 			return err
 		}
@@ -443,10 +442,10 @@ func (c *ChannelArbitrator) Start() error {
 // starting the ChannelArbitrator. This information should ideally be stored in
 // the database, so this only serves as a intermediate work-around to prevent a
 // migration.
-func (c *ChannelArbitrator) relaunchResolvers(confirmedHTLCs []channeldb.HTLC) error {
-	// We'll now query our log to see if there are any active
-	// unresolved contracts. If this is the case, then we'll
-	// relaunch all contract resolvers.
+func (c *ChannelArbitrator) relaunchResolvers(commitSet *CommitSet) error {
+	// We'll now query our log to see if there are any active unresolved
+	// contracts. If this is the case, then we'll relaunch all contract
+	// resolvers.
 	unresolvedContracts, err := c.log.FetchUnresolvedContracts()
 	if err != nil {
 		return err
@@ -461,6 +460,27 @@ func (c *ChannelArbitrator) relaunchResolvers(confirmedHTLCs []channeldb.HTLC) e
 	}
 	commitHash := contractResolutions.CommitHash
 
+	// In prior versions of lnd, the information needed to supplement the
+	// resolvers (in most cases, the full amount of the HTLC) was found in
+	// the chain action map, which is now deprecated.  As a result, if the
+	// commitSet is nil (an older node with unresolved HTLCs at time of
+	// upgrade), then we'll use the chain action information in place. The
+	// chain actions may exclude some information, but we cannot recover it
+	// for these older nodes at the moment.
+	var confirmedHTLCs []channeldb.HTLC
+	if commitSet != nil {
+		confirmedHTLCs = commitSet.HtlcSets[*commitSet.ConfCommitKey]
+	} else {
+		chainActions, err := c.log.FetchChainActions()
+		if err != nil {
+			log.Errorf("unable to fetch chain actions: %v", err)
+			return err
+		}
+		for _, htlcs := range chainActions {
+			confirmedHTLCs = append(confirmedHTLCs, htlcs...)
+		}
+	}
+
 	// Reconstruct the htlc outpoints and data from the chain action log.
 	// The purpose of the constructed htlc map is to supplement to
 	// resolvers restored from database with extra data. Ideally this data