From b7aebd92cf22ade5cc511dd270bff31bf6dfde28 Mon Sep 17 00:00:00 2001
From: Conner Fromknecht <conner@lightning.engineering>
Date: Tue, 18 Sep 2018 00:22:38 -0700
Subject: [PATCH] cnct/contract_resolvers: reliably publish commit sweep

---
 contractcourt/contract_resolvers.go | 29 ++++++++++++++++++++++-------
 1 file changed, 22 insertions(+), 7 deletions(-)

diff --git a/contractcourt/contract_resolvers.go b/contractcourt/contract_resolvers.go
index 223220d6..d0d7328e 100644
--- a/contractcourt/contract_resolvers.go
+++ b/contractcourt/contract_resolvers.go
@@ -1258,18 +1258,33 @@ func (c *commitSweepResolver) Resolve() (ContractResolver, error) {
 		log.Infof("%T(%v): sweeping commit output with tx=%v", c,
 			c.chanPoint, spew.Sdump(c.sweepTx))
 
-		// Finally, we'll broadcast the sweep transaction to the
-		// network.
-		if err := c.PublishTx(c.sweepTx); err != nil {
+		// With the sweep transaction constructed, we'll now Checkpoint
+		// our state.
+		if err := c.Checkpoint(c); err != nil {
+			log.Errorf("unable to Checkpoint: %v", err)
+			return nil, err
+		}
+
+		// With the sweep transaction checkpointed, we'll now publish
+		// the transaction. Upon restart, the resolver will immediately
+		// take the case below since the sweep tx is checkpointed.
+		err := c.PublishTx(c.sweepTx)
+		if err != nil && err != lnwallet.ErrDoubleSpend {
 			log.Errorf("%T(%v): unable to publish sweep tx: %v",
 				c, c.chanPoint, err)
 			return nil, err
 		}
 
-		// With the sweep transaction confirmed, we'll now Checkpoint
-		// our state.
-		if err := c.Checkpoint(c); err != nil {
-			log.Errorf("unable to Checkpoint: %v", err)
+	// If the sweep transaction has been generated, and the remote party
+	// broadcast the commit transaction, we'll republish it for reliability
+	// to ensure it confirms. The resolver will enter this case after
+	// checkpointing in the case above, ensuring we reliably on restarts.
+	case c.sweepTx != nil && !isLocalCommitTx:
+		err := c.PublishTx(c.sweepTx)
+		if err != nil && err != lnwallet.ErrDoubleSpend {
+			log.Errorf("%T(%v): unable to publish sweep tx: %v",
+				c, c.chanPoint, err)
+			return nil, err
 		}
 
 	// Otherwise, this is our commitment transaction, So we'll obtain the