Install trigger for DAO-rescue soft-fork.

Soft-fork should only be primed to trigger if the gas-limit of
block #1760000 is at most 4,000,000.

To accomplish this we pass in the gas limit of that block to
EnvInfo so it can inform Schedule. This gets marshalled through
`OpenBlock`/`ClosedBlock` and the `enact` functions much like
`last_hashes`. `block.rs`'s `env_info()` takes care to ensure
that if the current block happens to be #1760000, then we
populate with the current `gas_limit`.

ethcore/src/basic_authority.rs

@@ -215,8 +215,9 @@ mod tests {
 			timestamp: 0,
 			difficulty: 0.into(),
 			last_hashes: vec![],
+			dao_rescue_block_gas_limit: None,
 			gas_used: 0.into(),
-			gas_limit: 0.into()
+			gas_limit: 0.into(),
 		});
 
 		assert!(schedule.stack_limit > 0);
@@ -278,7 +279,7 @@ mod tests {
 		spec.ensure_db_good(db.as_hashdb_mut());
 		let last_hashes = vec![genesis_header.hash()];
 		let vm_factory = Default::default();
-		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, addr.clone(), 3141562.into(), vec![]).unwrap();
+		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, None, addr.clone(), 3141562.into(), vec![]).unwrap();
 		let b = b.close_and_lock();
 		let seal = engine.generate_seal(b.block(), Some(&tap)).unwrap();
 

ethcore/src/block.rs

@@ -177,6 +177,7 @@ pub struct OpenBlock<'x> {
 	engine: &'x Engine,
 	vm_factory: &'x EvmFactory,
 	last_hashes: LastHashes,
+	dao_rescue_block_gas_limit: Option<U256>,
 }
 
 /// Just like `OpenBlock`, except that we've applied `Engine::on_close_block`, finished up the non-seal header fields,
@@ -188,6 +189,7 @@ pub struct ClosedBlock {
 	block: ExecutedBlock,
 	uncle_bytes: Bytes,
 	last_hashes: LastHashes,
+	dao_rescue_block_gas_limit: Option<U256>,
 	unclosed_state: State,
 }
 
@@ -198,7 +200,6 @@ pub struct ClosedBlock {
 pub struct LockedBlock {
 	block: ExecutedBlock,
 	uncle_bytes: Bytes,
-	last_hashes: LastHashes,
 }
 
 /// A block that has a valid seal.
@@ -219,9 +220,10 @@ impl<'x> OpenBlock<'x> {
 		db: Box<JournalDB>,
 		parent: &Header,
 		last_hashes: LastHashes,
+		dao_rescue_block_gas_limit: Option<U256>,
 		author: Address,
 		gas_floor_target: U256,
-		extra_data: Bytes
+		extra_data: Bytes,
 	) -> Result<Self, Error> {
 		let state = try!(State::from_existing(db, parent.state_root().clone(), engine.account_start_nonce()));
 		let mut r = OpenBlock {
@@ -229,6 +231,7 @@ impl<'x> OpenBlock<'x> {
 			engine: engine,
 			vm_factory: vm_factory,
 			last_hashes: last_hashes,
+			dao_rescue_block_gas_limit: dao_rescue_block_gas_limit,
 		};
 
 		r.block.base.header.parent_hash = parent.hash();
@@ -293,6 +296,7 @@ impl<'x> OpenBlock<'x> {
 			last_hashes: self.last_hashes.clone(),		// TODO: should be a reference.
 			gas_used: self.block.receipts.last().map_or(U256::zero(), |r| r.gas_used),
 			gas_limit: self.block.base.header.gas_limit.clone(),
+			dao_rescue_block_gas_limit: if self.block.base.header.number == 1760000 { Some(self.block.base.header.gas_limit) } else { self.dao_rescue_block_gas_limit },
 		}
 	}
 
@@ -339,6 +343,7 @@ impl<'x> OpenBlock<'x> {
 			block: s.block,
 			uncle_bytes: uncle_bytes,
 			last_hashes: s.last_hashes,
+			dao_rescue_block_gas_limit: s.dao_rescue_block_gas_limit,
 			unclosed_state: unclosed_state,
 		}
 	}
@@ -360,7 +365,6 @@ impl<'x> OpenBlock<'x> {
 		LockedBlock {
 			block: s.block,
 			uncle_bytes: uncle_bytes,
-			last_hashes: s.last_hashes,
 		}
 	}
 }
@@ -386,7 +390,6 @@ impl ClosedBlock {
 		LockedBlock {
 			block: self.block,
 			uncle_bytes: self.uncle_bytes,
-			last_hashes: self.last_hashes,
 		}
 	}
 
@@ -400,6 +403,7 @@ impl ClosedBlock {
 			engine: engine,
 			vm_factory: vm_factory,
 			last_hashes: self.last_hashes,
+			dao_rescue_block_gas_limit: self.dao_rescue_block_gas_limit,
 		}
 	}
 }
@@ -456,7 +460,18 @@ impl IsBlock for SealedBlock {
 
 /// Enact the block given by block header, transactions and uncles
 #[cfg_attr(feature="dev", allow(too_many_arguments))]
-pub fn enact(header: &Header, transactions: &[SignedTransaction], uncles: &[Header], engine: &Engine, tracing: bool, db: Box<JournalDB>, parent: &Header, last_hashes: LastHashes, vm_factory: &EvmFactory) -> Result<LockedBlock, Error> {
+pub fn enact(
+	header: &Header,
+	transactions: &[SignedTransaction],
+	uncles: &[Header],
+	engine: &Engine,
+	tracing: bool,
+	db: Box<JournalDB>,
+	parent: &Header,
+	last_hashes: LastHashes,
+	dao_rescue_block_gas_limit: Option<U256>,
+	vm_factory: &EvmFactory
+) -> Result<LockedBlock, Error> {
 	{
 		if ::log::max_log_level() >= ::log::LogLevel::Trace {
 			let s = try!(State::from_existing(db.boxed_clone(), parent.state_root().clone(), engine.account_start_nonce()));
@@ -464,7 +479,7 @@ pub fn enact(header: &Header, transactions: &[SignedTransaction], uncles: &[Head
 		}
 	}
 
-	let mut b = try!(OpenBlock::new(engine, vm_factory, tracing, db, parent, last_hashes, header.author().clone(), 3141562.into(), header.extra_data().clone()));
+	let mut b = try!(OpenBlock::new(engine, vm_factory, tracing, db, parent, last_hashes, dao_rescue_block_gas_limit, header.author().clone(), 3141562.into(), header.extra_data().clone()));
 	b.set_difficulty(*header.difficulty());
 	b.set_gas_limit(*header.gas_limit());
 	b.set_timestamp(header.timestamp());
@@ -474,22 +489,49 @@ pub fn enact(header: &Header, transactions: &[SignedTransaction], uncles: &[Head
 }
 
 /// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header
-pub fn enact_bytes(block_bytes: &[u8], engine: &Engine, tracing: bool, db: Box<JournalDB>, parent: &Header, last_hashes: LastHashes, vm_factory: &EvmFactory) -> Result<LockedBlock, Error> {
+pub fn enact_bytes(
+	block_bytes: &[u8],
+	engine: &Engine,
+	tracing: bool,
+	db: Box<JournalDB>,
+	parent: &Header,
+	last_hashes: LastHashes,
+	dao_rescue_block_gas_limit: Option<U256>,
+	vm_factory: &EvmFactory
+) -> Result<LockedBlock, Error> {
 	let block = BlockView::new(block_bytes);
 	let header = block.header();
-	enact(&header, &block.transactions(), &block.uncles(), engine, tracing, db, parent, last_hashes, vm_factory)
+	enact(&header, &block.transactions(), &block.uncles(), engine, tracing, db, parent, last_hashes, dao_rescue_block_gas_limit, vm_factory)
 }
 
 /// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header
-pub fn enact_verified(block: &PreverifiedBlock, engine: &Engine, tracing: bool, db: Box<JournalDB>, parent: &Header, last_hashes: LastHashes, vm_factory: &EvmFactory) -> Result<LockedBlock, Error> {
+pub fn enact_verified(
+	block: &PreverifiedBlock,
+	engine: &Engine,
+	tracing: bool,
+	db: Box<JournalDB>,
+	parent: &Header,
+	last_hashes: LastHashes,
+	dao_rescue_block_gas_limit: Option<U256>,
+	vm_factory: &EvmFactory
+) -> Result<LockedBlock, Error> {
 	let view = BlockView::new(&block.bytes);
-	enact(&block.header, &block.transactions, &view.uncles(), engine, tracing, db, parent, last_hashes, vm_factory)
+	enact(&block.header, &block.transactions, &view.uncles(), engine, tracing, db, parent, last_hashes, dao_rescue_block_gas_limit, vm_factory)
 }
 
 /// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header. Seal the block aferwards
-pub fn enact_and_seal(block_bytes: &[u8], engine: &Engine, tracing: bool, db: Box<JournalDB>, parent: &Header, last_hashes: LastHashes, vm_factory: &EvmFactory) -> Result<SealedBlock, Error> {
+pub fn enact_and_seal(
+	block_bytes: &[u8],
+	engine: &Engine,
+	tracing: bool,
+	db: Box<JournalDB>,
+	parent: &Header,
+	last_hashes: LastHashes,
+	dao_rescue_block_gas_limit: Option<U256>,
+	vm_factory: &EvmFactory
+) -> Result<SealedBlock, Error> {
 	let header = BlockView::new(block_bytes).header_view();
-	Ok(try!(try!(enact_bytes(block_bytes, engine, tracing, db, parent, last_hashes, vm_factory)).seal(engine, header.seal())))
+	Ok(try!(try!(enact_bytes(block_bytes, engine, tracing, db, parent, last_hashes, dao_rescue_block_gas_limit, vm_factory)).seal(engine, header.seal())))
 }
 
 #[cfg(test)]
@@ -509,7 +551,7 @@ mod tests {
 		spec.ensure_db_good(db.as_hashdb_mut());
 		let last_hashes = vec![genesis_header.hash()];
 		let vm_factory = Default::default();
-		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]).unwrap();
+		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, None, Address::zero(), 3141562.into(), vec![]).unwrap();
 		let b = b.close_and_lock();
 		let _ = b.seal(engine.deref(), vec![]);
 	}
@@ -525,7 +567,7 @@ mod tests {
 		let mut db = db_result.take();
 		spec.ensure_db_good(db.as_hashdb_mut());
 		let vm_factory = Default::default();
-		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], Address::zero(), 3141562.into(), vec![]).unwrap()
+		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], None, Address::zero(), 3141562.into(), vec![]).unwrap()
 			.close_and_lock().seal(engine.deref(), vec![]).unwrap();
 		let orig_bytes = b.rlp_bytes();
 		let orig_db = b.drain();
@@ -533,7 +575,7 @@ mod tests {
 		let mut db_result = get_temp_journal_db();
 		let mut db = db_result.take();
 		spec.ensure_db_good(db.as_hashdb_mut());
-		let e = enact_and_seal(&orig_bytes, engine.deref(), false, db, &genesis_header, vec![genesis_header.hash()], &Default::default()).unwrap();
+		let e = enact_and_seal(&orig_bytes, engine.deref(), false, db, &genesis_header, vec![genesis_header.hash()], None, &Default::default()).unwrap();
 
 		assert_eq!(e.rlp_bytes(), orig_bytes);
 
@@ -553,7 +595,7 @@ mod tests {
 		let mut db = db_result.take();
 		spec.ensure_db_good(db.as_hashdb_mut());
 		let vm_factory = Default::default();
-		let mut open_block = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], Address::zero(), 3141562.into(), vec![]).unwrap();
+		let mut open_block = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, vec![genesis_header.hash()], None, Address::zero(), 3141562.into(), vec![]).unwrap();
 		let mut uncle1_header = Header::new();
 		uncle1_header.extra_data = b"uncle1".to_vec();
 		let mut uncle2_header = Header::new();
@@ -568,7 +610,7 @@ mod tests {
 		let mut db_result = get_temp_journal_db();
 		let mut db = db_result.take();
 		spec.ensure_db_good(db.as_hashdb_mut());
-		let e = enact_and_seal(&orig_bytes, engine.deref(), false, db, &genesis_header, vec![genesis_header.hash()], &Default::default()).unwrap();
+		let e = enact_and_seal(&orig_bytes, engine.deref(), false, db, &genesis_header, vec![genesis_header.hash()], None, &Default::default()).unwrap();
 
 		let bytes = e.rlp_bytes();
 		assert_eq!(bytes, orig_bytes);

ethcore/src/client/client.rs

@@ -220,7 +220,7 @@ 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.vm_factory);
+		let enact_result = enact_verified(&block, engine, self.tracedb.tracing_enabled(), db, &parent, last_hashes, self.dao_rescue_block_gas_limit(), &self.vm_factory);
 		if let Err(e) = enact_result {
 			warn!(target: "client", "Block import failed for #{} ({})\nError: {:?}", header.number(), header.hash(), e);
 			return Err(());
@@ -462,6 +462,7 @@ 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(),
 		};
 		// that's just a copy of the state.
 		let mut state = self.state();
@@ -767,6 +768,7 @@ 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(),
 			author,
 			gas_floor_target,
 			extra_data,

ethcore/src/client/mod.rs

@@ -42,7 +42,7 @@ use header::{BlockNumber, Header};
 use transaction::{LocalizedTransaction, SignedTransaction};
 use log_entry::LocalizedLogEntry;
 use filter::Filter;
-use views::BlockView;
+use views::{HeaderView, BlockView};
 use error::{ImportResult, ExecutionError};
 use receipt::LocalizedReceipt;
 use trace::LocalizedTrace;
@@ -221,6 +221,13 @@ pub trait BlockChainClient : Sync + Send {
 			Err(())
 		}
 	}
+
+
+	/// 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())
+	}	
 }
 
 /// Extended client interface used for mining

ethcore/src/env_info.rs

@@ -39,6 +39,9 @@ pub struct EnvInfo {
 	pub last_hashes: LastHashes,
 	/// The gas used.
 	pub gas_used: U256,
+
+	/// Block gas limit at DAO rescue block #1760000 or None if not yet there.
+	pub dao_rescue_block_gas_limit: Option<U256>,
 }
 
 impl Default for EnvInfo {
@@ -51,6 +54,7 @@ impl Default for EnvInfo {
 			gas_limit: 0.into(),
 			last_hashes: vec![],
 			gas_used: 0.into(),
+			dao_rescue_block_gas_limit: None,
 		}
 	}
 }
@@ -66,6 +70,7 @@ impl From<ethjson::vm::Env> for EnvInfo {
 			timestamp: e.timestamp.into(),
 			last_hashes: (1..cmp::min(number + 1, 257)).map(|i| format!("{}", number - i).as_bytes().sha3()).collect(),
 			gas_used: U256::zero(),
+			dao_rescue_block_gas_limit: None,
 		}
 	}
 }

ethcore/src/ethereum/ethash.rs

@@ -103,7 +103,7 @@ impl Engine for Ethash {
 		} else {
 			let mut s = Schedule::new_homestead();
 			// TODO: make dependent on gaslimit > 4000000 of block 1760000.	
-			s.block_dao_transactions = env_info.number >= 1760000;
+			s.block_dao_transactions = env_info.dao_rescue_block_gas_limit.map(|x| x <= 4_000_000.into()).unwrap_or(false);
 			s
 		}
 	}
@@ -319,7 +319,7 @@ mod tests {
 		spec.ensure_db_good(db.as_hashdb_mut());
 		let last_hashes = vec![genesis_header.hash()];
 		let vm_factory = Default::default();
-		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]).unwrap();
+		let b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, None, Address::zero(), 3141562.into(), vec![]).unwrap();
 		let b = b.close();
 		assert_eq!(b.state().balance(&Address::zero()), U256::from_str("4563918244f40000").unwrap());
 	}
@@ -334,7 +334,7 @@ mod tests {
 		spec.ensure_db_good(db.as_hashdb_mut());
 		let last_hashes = vec![genesis_header.hash()];
 		let vm_factory = Default::default();
-		let mut b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, Address::zero(), 3141562.into(), vec![]).unwrap();
+		let mut b = OpenBlock::new(engine.deref(), &vm_factory, false, db, &genesis_header, last_hashes, None, Address::zero(), 3141562.into(), vec![]).unwrap();
 		let mut uncle = Header::new();
 		let uncle_author = address_from_hex("ef2d6d194084c2de36e0dabfce45d046b37d1106");
 		uncle.author = uncle_author.clone();
@@ -362,7 +362,8 @@ mod tests {
 			difficulty: 0.into(),
 			last_hashes: vec![],
 			gas_used: 0.into(),
-			gas_limit: 0.into()
+			gas_limit: 0.into(),
+			dao_rescue_block_gas_limit: None,
 		});
 
 		assert!(schedule.stack_limit > 0);
@@ -374,7 +375,8 @@ mod tests {
 			difficulty: 0.into(),
 			last_hashes: vec![],
 			gas_used: 0.into(),
-			gas_limit: 0.into()
+			gas_limit: 0.into(),
+			dao_rescue_block_gas_limit: None,
 		});
 
 		assert!(!schedule.have_delegate_call);

ethcore/src/externalities.rs

@@ -318,7 +318,8 @@ mod tests {
 			difficulty: 0.into(),
 			last_hashes: vec![],
 			gas_used: 0.into(),
-			gas_limit: 0.into()
+			gas_limit: 0.into(),
+			dao_rescue_block_gas_limit: None,
 		}
 	}
 

ethcore/src/miner/miner.rs

@@ -266,6 +266,7 @@ 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(),
 				};
 				// that's just a copy of the state.
 				let mut state = block.state().clone();

ethcore/src/tests/helpers.rs

@@ -179,6 +179,7 @@ pub fn generate_dummy_client_with_spec_and_data<F>(get_test_spec: F, block_numbe
 			db,
 			&last_header,
 			last_hashes.clone(),
+			None,
 			author.clone(),
 			3141562.into(),
 			vec![]