From 5302a7dd58265728f230d14bb1358a90ec1d2497 Mon Sep 17 00:00:00 2001
From: Gav Wood <gavin@ethcore.io>
Date: Wed, 22 Jun 2016 19:49:07 +0200
Subject: [PATCH] Ensure judging the SF trigger by relative branch

Rather than just the canon chain.
---
 ethcore/src/client/client.rs |  6 +++---
 ethcore/src/client/mod.rs    | 16 +++++++++++++---
 ethcore/src/miner/miner.rs   |  2 +-
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/ethcore/src/client/client.rs b/ethcore/src/client/client.rs
index fa063cd61..693296469 100644
--- a/ethcore/src/client/client.rs
+++ b/ethcore/src/client/client.rs
@@ -230,7 +230,7 @@ impl<V> Client<V> where V: Verifier {
 		let last_hashes = self.build_last_hashes(header.parent_hash.clone());
 		let db = self.state_db.lock().unwrap().boxed_clone();
 
-		let enact_result = enact_verified(&block, engine, self.tracedb.tracing_enabled(), db, &parent, last_hashes, self.dao_rescue_block_gas_limit(), &self.vm_factory);
+		let enact_result = enact_verified(&block, engine, self.tracedb.tracing_enabled(), db, &parent, last_hashes, self.dao_rescue_block_gas_limit(header.parent_hash.clone()), &self.vm_factory);
 		if let Err(e) = enact_result {
 			warn!(target: "client", "Block import failed for #{} ({})\nError: {:?}", header.number(), header.hash(), e);
 			return Err(());
@@ -486,7 +486,7 @@ impl<V> BlockChainClient for Client<V> where V: Verifier {
 			last_hashes: last_hashes,
 			gas_used: U256::zero(),
 			gas_limit: U256::max_value(),
-			dao_rescue_block_gas_limit: self.dao_rescue_block_gas_limit(),
+			dao_rescue_block_gas_limit: self.dao_rescue_block_gas_limit(view.parent_hash()),
 		};
 		// that's just a copy of the state.
 		let mut state = self.state();
@@ -808,7 +808,7 @@ impl<V> MiningBlockChainClient for Client<V> where V: Verifier {
 			self.state_db.lock().unwrap().boxed_clone(),
 			&self.chain.block_header(&h).expect("h is best block hash: so it's header must exist: qed"),
 			self.build_last_hashes(h.clone()),
-			self.dao_rescue_block_gas_limit(),
+			self.dao_rescue_block_gas_limit(h.clone()),
 			author,
 			gas_floor_target,
 			extra_data,
diff --git a/ethcore/src/client/mod.rs b/ethcore/src/client/mod.rs
index c1bc3203c..589b65e16 100644
--- a/ethcore/src/client/mod.rs
+++ b/ethcore/src/client/mod.rs
@@ -227,9 +227,19 @@ pub trait BlockChainClient : Sync + Send {
 
 
 	/// Get `Some` gas limit of block 1_760_000, or `None` if chain is not yet that long.
-	fn dao_rescue_block_gas_limit(&self) -> Option<U256> {
-		self.block_header(BlockID::Number(1_760_000))
-			.map(|header| HeaderView::new(&header).gas_limit())
+	fn dao_rescue_block_gas_limit(&self, chain_hash: H256) -> Option<U256> {
+		if let Some(mut header) = self.block_header(BlockID::Hash(chain_hash)) {
+			if HeaderView::new(&header).number() < 1_760_000 {
+				None
+			} else {
+				while HeaderView::new(&header).number() != 1_760_000 {
+					header = self.block_header(BlockID::Hash(HeaderView::new(&header).parent_hash())).expect("chain is complete; parent of chain entry must be in chain; qed");
+				}
+				Some(HeaderView::new(&header).gas_limit())
+			}
+		} else {
+			None
+		}
 	}	
 }
 
diff --git a/ethcore/src/miner/miner.rs b/ethcore/src/miner/miner.rs
index 41e4b4810..290e94059 100644
--- a/ethcore/src/miner/miner.rs
+++ b/ethcore/src/miner/miner.rs
@@ -274,7 +274,7 @@ impl MinerService for Miner {
 					last_hashes: last_hashes,
 					gas_used: U256::zero(),
 					gas_limit: U256::max_value(),
-					dao_rescue_block_gas_limit: chain.dao_rescue_block_gas_limit(),
+					dao_rescue_block_gas_limit: chain.dao_rescue_block_gas_limit(header.parent_hash().clone()),
 				};
 				// that's just a copy of the state.
 				let mut state = block.state().clone();