PoA: Wait for transition finality before applying (#5774)

* final engine changes

* migration to v13

* adding and removing pending transitions

* epoch_transition_for

* port snapshot to new engine methods

* final validator set interface

* fix compiler errors

* revert v13/epoch_depth transition

* make call on new epoch

* rolling finality checker

* tests for finality checker

* constructing finality proof upon pending transition

* fix warnings and finality proof checking

* fix compiler warnings in tests

* test fixes

* don't include genesis in finality checking

* change snapshot test chain building logic

* minor refactorings

* fetch epoch transition based on parent, fix divide-by-zero in SimpleList

* fix formatting

* fix ABIs and finality checking in snapshot restoration

* encode signal number in proof

* create more blocks at the end of tests

* update gist to accurate contract code

* test for epoch_transition_for

* fix tests with immediateTransitions parameter

* disable force flag after forcing

* rename ValidatorsChanged to InitiateChange and finalizeSignal to finalizeChange

* a few more validator set tests

ethcore/native_contracts/build.rs

@@ -28,7 +28,7 @@ const SECRETSTORE_ACL_STORAGE_ABI: &'static str = include_str!("res/secretstore_
 const VALIDATOR_SET_ABI: &'static str = include_str!("res/validator_set.json");
 const VALIDATOR_REPORT_ABI: &'static str = include_str!("res/validator_report.json");
 
-const TEST_VALIDATOR_SET_ABI: &'static str = r#"[{"constant":true,"inputs":[],"name":"transitionNonce","outputs":[{"name":"n","type":"uint256"}],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"newValidators","type":"address[]"}],"name":"setValidators","outputs":[],"payable":false,"type":"function"},{"constant":true,"inputs":[],"name":"getValidators","outputs":[{"name":"vals","type":"address[]"}],"payable":false,"type":"function"},{"inputs":[],"payable":false,"type":"constructor"},{"anonymous":false,"inputs":[{"indexed":true,"name":"_parent_hash","type":"bytes32"},{"indexed":true,"name":"_nonce","type":"uint256"},{"indexed":false,"name":"_new_set","type":"address[]"}],"name":"ValidatorsChanged","type":"event"}]"#;
+const TEST_VALIDATOR_SET_ABI: &'static str = include_str!("res/test_validator_set.json");
 
 fn build_file(name: &str, abi: &str, filename: &str) {
 	let code = ::native_contract_generator::generate_module(name, abi).unwrap();

ethcore/native_contracts/generator/src/lib.rs

@@ -108,7 +108,7 @@ fn generate_functions(contract: &Contract) -> Result<String, Error> {
 /// Outputs: {abi_outputs:?}
 pub fn {snake_name}<F, U>(&self, call: F, {params}) -> BoxFuture<{output_type}, String>
 	where
-	    F: Fn(util::Address, Vec<u8>) -> U,
+	    F: FnOnce(util::Address, Vec<u8>) -> U,
 	    U: IntoFuture<Item=Vec<u8>, Error=String>,
 		U::Future: Send + 'static
 {{

ethcore/native_contracts/res/test_validator_set.json

@@ -0,0 +1,8 @@
+[
+	{"constant":false,"inputs":[{"name":"_validators","type":"address[]"}],"name":"setValidators","outputs":[],"payable":false,"type":"function"},
+	{"constant":false,"inputs":[{"name":"","type":"address"},{"name":"","type":"bytes"}],"name":"reportMalicious","outputs":[],"payable":false,"type":"function"},
+	{"constant":false,"inputs":[],"name":"finalizeChange","outputs":[],"payable":false,"type":"function"},
+	{"constant":true,"inputs":[],"name":"getValidators","outputs":[{"name":"_validators","type":"address[]"}],"payable":false,"type":"function"},
+	{"constant":false,"inputs":[{"name":"","type":"address"}],"name":"reportBenign","outputs":[],"payable":false,"type":"function"},
+	{"anonymous":false,"inputs":[{"indexed":true,"name":"_parent_hash","type":"bytes32"},{"indexed":false,"name":"_new_set","type":"address[]"}],"name":"InitiateChange","type":"event"}
+]

ethcore/native_contracts/res/validator_set.json

@@ -1,5 +1,5 @@
 [
-	{"constant":true,"inputs":[],"name":"transitionNonce","outputs":[{"name":"nonce","type":"uint256"}],"payable":false,"type":"function"},
+	{"constant":false,"inputs":[],"name":"finalizeChange","outputs":[],"payable":false,"type":"function"},
 	{"constant":true,"inputs":[],"name":"getValidators","outputs":[{"name":"validators","type":"address[]"}],"payable":false,"type":"function"},
-	{"anonymous":false,"inputs":[{"indexed":true,"name":"_parent_hash","type":"bytes32"},{"indexed":true,"name":"_nonce","type":"uint256"},{"indexed":false,"name":"_new_set","type":"address[]"}],"name":"ValidatorsChanged","type":"event"}
+	{"anonymous":false,"inputs":[{"indexed":true,"name":"_parent_hash","type":"bytes32"},{"indexed":false,"name":"_new_set","type":"address[]"}],"name":"InitiateChange","type":"event"}
 ]

ethcore/res/authority_round.json

@@ -11,7 +11,8 @@
 						"0x7d577a597b2742b498cb5cf0c26cdcd726d39e6e",
 						"0x82a978b3f5962a5b0957d9ee9eef472ee55b42f1"
 					]
-				}
+				},
+				"immediateTransitions": true
 			}
 		}
 	},

ethcore/res/validator_contract.json

@@ -8,7 +8,8 @@
 				"startStep": 2,
 				"validators": {
 					"contract": "0x0000000000000000000000000000000000000005"
-				}
+				},
+				"immediateTransitions": true
 			}
 		}
 	},

ethcore/src/block.rs

@@ -260,6 +260,7 @@ impl<'x> OpenBlock<'x> {
 		author: Address,
 		gas_range_target: (U256, U256),
 		extra_data: Bytes,
+		is_epoch_begin: bool,
 	) -> Result<Self, Error> {
 		let number = parent.number() + 1;
 		let state = State::from_existing(db, parent.state_root().clone(), engine.account_start_nonce(number), factories)?;
@@ -279,7 +280,8 @@ impl<'x> OpenBlock<'x> {
 		let gas_floor_target = cmp::max(gas_range_target.0, engine.params().min_gas_limit);
 		let gas_ceil_target = cmp::max(gas_range_target.1, gas_floor_target);
 		engine.populate_from_parent(&mut r.block.header, parent, gas_floor_target, gas_ceil_target);
-		engine.on_new_block(&mut r.block, last_hashes)?;
+		engine.on_new_block(&mut r.block, last_hashes, is_epoch_begin)?;
+
 		Ok(r)
 	}
 
@@ -430,7 +432,7 @@ impl<'x> OpenBlock<'x> {
 
 	#[cfg(test)]
 	/// Return mutable block reference. To be used in tests only.
-	pub fn block_mut (&mut self) -> &mut ExecutedBlock { &mut self.block }
+	pub fn block_mut(&mut self) -> &mut ExecutedBlock { &mut self.block }
 }
 
 impl<'x> IsBlock for OpenBlock<'x> {
@@ -554,6 +556,7 @@ pub fn enact(
 	parent: &Header,
 	last_hashes: Arc<LastHashes>,
 	factories: Factories,
+	is_epoch_begin: bool,
 ) -> Result<LockedBlock, Error> {
 	{
 		if ::log::max_log_level() >= ::log::LogLevel::Trace {
@@ -563,7 +566,19 @@ pub fn enact(
 		}
 	}
 
-	let mut b = OpenBlock::new(engine, factories, tracing, db, parent, last_hashes, Address::new(), (3141562.into(), 31415620.into()), vec![])?;
+	let mut b = OpenBlock::new(
+		engine,
+		factories,
+		tracing,
+		db,
+		parent,
+		last_hashes,
+		Address::new(),
+		(3141562.into(), 31415620.into()),
+		vec![],
+		is_epoch_begin,
+	)?;
+
 	b.set_difficulty(*header.difficulty());
 	b.set_gas_limit(*header.gas_limit());
 	b.set_timestamp(header.timestamp());
@@ -618,9 +633,22 @@ pub fn enact_verified(
 	parent: &Header,
 	last_hashes: Arc<LastHashes>,
 	factories: Factories,
+	is_epoch_begin: bool,
 ) -> Result<LockedBlock, Error> {
 	let view = BlockView::new(&block.bytes);
-	enact(&block.header, &block.transactions, &view.uncles(), engine, tracing, db, parent, last_hashes, factories)
+
+	enact(
+		&block.header,
+		&block.transactions,
+		&view.uncles(),
+		engine,
+		tracing,
+		db,
+		parent,
+		last_hashes,
+		factories,
+		is_epoch_begin,
+	)
 }
 
 #[cfg(test)]
@@ -653,7 +681,7 @@ mod tests {
 		let header = block.header();
 		let transactions: Result<Vec<_>, Error> = block.transactions().into_iter().map(SignedTransaction::new).collect();
 		let transactions = transactions?;
-		enact(&header, &transactions, &block.uncles(), engine, tracing, db, parent, last_hashes, factories)
+		enact(&header, &transactions, &block.uncles(), engine, tracing, db, parent, last_hashes, factories, false)
 	}
 
 	/// Enact the block given by `block_bytes` using `engine` on the database `db` with given `parent` block header. Seal the block aferwards
@@ -678,7 +706,7 @@ mod tests {
 		let genesis_header = spec.genesis_header();
 		let db = spec.ensure_db_good(get_temp_state_db(), &Default::default()).unwrap();
 		let last_hashes = Arc::new(vec![genesis_header.hash()]);
-		let b = OpenBlock::new(&*spec.engine, Default::default(), false, db, &genesis_header, last_hashes, Address::zero(), (3141562.into(), 31415620.into()), vec![]).unwrap();
+		let b = OpenBlock::new(&*spec.engine, Default::default(), false, db, &genesis_header, last_hashes, Address::zero(), (3141562.into(), 31415620.into()), vec![], false).unwrap();
 		let b = b.close_and_lock();
 		let _ = b.seal(&*spec.engine, vec![]);
 	}
@@ -692,7 +720,7 @@ mod tests {
 
 		let db = spec.ensure_db_good(get_temp_state_db(), &Default::default()).unwrap();
 		let last_hashes = Arc::new(vec![genesis_header.hash()]);
-		let b = OpenBlock::new(engine, Default::default(), false, db, &genesis_header, last_hashes.clone(), Address::zero(), (3141562.into(), 31415620.into()), vec![]).unwrap()
+		let b = OpenBlock::new(engine, Default::default(), false, db, &genesis_header, last_hashes.clone(), Address::zero(), (3141562.into(), 31415620.into()), vec![], false).unwrap()
 			.close_and_lock().seal(engine, vec![]).unwrap();
 		let orig_bytes = b.rlp_bytes();
 		let orig_db = b.drain();
@@ -716,7 +744,7 @@ mod tests {
 
 		let db = spec.ensure_db_good(get_temp_state_db(), &Default::default()).unwrap();
 		let last_hashes = Arc::new(vec![genesis_header.hash()]);
-		let mut open_block = OpenBlock::new(engine, Default::default(), false, db, &genesis_header, last_hashes.clone(), Address::zero(), (3141562.into(), 31415620.into()), vec![]).unwrap();
+		let mut open_block = OpenBlock::new(engine, Default::default(), false, db, &genesis_header, last_hashes.clone(), Address::zero(), (3141562.into(), 31415620.into()), vec![], false).unwrap();
 		let mut uncle1_header = Header::new();
 		uncle1_header.set_extra_data(b"uncle1".to_vec());
 		let mut uncle2_header = Header::new();