From 406642a1f069ebe3026be7fed39a3205a91dd3bc Mon Sep 17 00:00:00 2001
From: Ignotus Peverell <igno.peverell@protonmail.com>
Date: Wed, 18 Oct 2017 04:48:21 +0000
Subject: [PATCH] Fix for missing header head during sync

Addresses a corner case of sync. If we're still in sync mode but
just caught up to the head, a block could be added through normal
gossip. So we can't short-circuit some of the header handling
even though during sync the header should have already been
validated and saved, because we can still get a block from gossip.
---
 chain/src/pipe.rs    | 17 ++---------------
 grin/src/adapters.rs |  5 +++--
 grin/src/sync.rs     |  3 +++
 3 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/chain/src/pipe.rs b/chain/src/pipe.rs
index 2cc4f2893..b34f681bb 100644
--- a/chain/src/pipe.rs
+++ b/chain/src/pipe.rs
@@ -322,22 +322,9 @@ fn update_head(b: &Block, ctx: &mut BlockContext) -> Result<Option<Tip>, Error>
 		// update the block height index
 		ctx.store.setup_height(&b.header).map_err(&Error::StoreErr)?;
 
-		// in sync mode, only update the "body chain", otherwise update both the
-		// "header chain" and "body chain"
-		if ctx.opts.intersects(SYNC) {
-			ctx.store.save_body_head(&tip).map_err(&Error::StoreErr)?;
-		} else {
-			ctx.store.save_head(&tip).map_err(&Error::StoreErr)?;
-		}
-		// TODO if we're switching branch, make sure to backtrack the sum trees
-
+		ctx.store.save_head(&tip).map_err(&Error::StoreErr)?;
 		ctx.head = tip.clone();
-		info!(
-			LOGGER,
-			"Updated head to {} at {}.",
-			b.hash(),
-			b.header.height
-		);
+		info!(LOGGER, "Updated head to {} at {}.", b.hash(), b.header.height);
 		Ok(Some(tip))
 	} else {
 		Ok(None)
diff --git a/grin/src/adapters.rs b/grin/src/adapters.rs
index e80a50e6d..a6eaff884 100644
--- a/grin/src/adapters.rs
+++ b/grin/src/adapters.rs
@@ -60,8 +60,9 @@ impl NetAdapter for NetToChainAdapter {
 		let bhash = b.hash();
 		debug!(
 			LOGGER,
-			"Received block {} from network, going to process.",
-			bhash
+			"Received block {} at {} from network, going to process.",
+			bhash,
+			b.header.height,
 		);
 
 		// pushing the new block through the chain pipeline
diff --git a/grin/src/sync.rs b/grin/src/sync.rs
index b66662a33..85c5ceac6 100644
--- a/grin/src/sync.rs
+++ b/grin/src/sync.rs
@@ -126,6 +126,9 @@ impl Syncer {
 		let mut prev_h = header_head.last_block_h;
 		while prev_h != full_head.last_block_h {
 			let header = self.chain.get_block_header(&prev_h)?;
+			if header.height < full_head.height {
+				break;
+			}
 			blocks_to_download.push(header.hash());
 			prev_h = header.previous;
 		}