PoA warp implementation (openethereum#5488)

* separate modules for consensus snapshot chunks

* bulk of authority warp logic

* finish authority warp implementation

* squash warnings and enable authority snapshot mode

* test harness for PoA

* fiddle with harness

* epoch generation proof fixes

* update constructor code

* store epoch transition proof after block commit

* basic snap and restore test

* use keyvaluedb in state restoration

* decompress chunks

* fix encoding issues

* fixed-to-contract-to-contract test

* implement ancient block import

* restore genesis transition in PoW snapshot

* add format version method to snapshot components

* supported version numbers in snapshot_components

* allow returning of ancient epoch transitions

* genesis hash mismatch check

* remove commented code

devtools/src/random_path.rs

@@ -96,7 +96,7 @@ impl Drop for RandomTempPath {
 
 pub struct GuardedTempResult<T> {
 	pub result: Option<T>,
-	pub _temp: RandomTempPath
+	pub _temp: RandomTempPath,
 }
 
 impl<T> GuardedTempResult<T> {

ethcore/Cargo.toml

@@ -52,6 +52,9 @@ stats = { path = "../util/stats" }
 time = "0.1"
 transient-hashmap = "0.4"
 
+[dev-dependencies]
+native-contracts = { path = "native_contracts", features = ["test_contracts"] }
+
 [features]
 jit = ["evmjit"]
 evm-debug = ["slow-blocks"]

ethcore/native_contracts/Cargo.toml

@@ -13,3 +13,6 @@ ethcore-util = { path = "../../util" }
 
 [build-dependencies]
 native-contract-generator = { path = "generator" }
+
+[features]
+default = []

ethcore/native_contracts/build.rs

@@ -33,6 +33,8 @@ const VALIDATOR_SET_ABI: &'static str = r#"[{"constant":true,"inputs":[],"name":
 
 const VALIDATOR_REPORT_ABI: &'static str = r#"[{"constant":false,"inputs":[{"name":"validator","type":"address"},{"name":"blockNumber","type":"uint256"},{"name":"proof","type":"bytes"}],"name":"reportMalicious","outputs":[],"payable":false,"type":"function"},{"constant":false,"inputs":[{"name":"validator","type":"address"},{"name":"blockNumber","type":"uint256"}],"name":"reportBenign","outputs":[],"payable":false,"type":"function"}]"#;
 
+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"}]"#;
+
 fn build_file(name: &str, abi: &str, filename: &str) {
 	let code = ::native_contract_generator::generate_module(name, abi).unwrap();
 
@@ -43,10 +45,16 @@ fn build_file(name: &str, abi: &str, filename: &str) {
 	f.write_all(code.as_bytes()).unwrap();
 }
 
+fn build_test_contracts() {
+	build_file("ValidatorSet", TEST_VALIDATOR_SET_ABI, "test_validator_set.rs");
+}
+
 fn main() {
 	build_file("Registry", REGISTRY_ABI, "registry.rs");
 	build_file("ServiceTransactionChecker", SERVICE_TRANSACTION_ABI, "service_transaction.rs");
 	build_file("SecretStoreAclStorage", SECRETSTORE_ACL_STORAGE_ABI, "secretstore_acl_storage.rs");
 	build_file("ValidatorSet", VALIDATOR_SET_ABI, "validator_set.rs");
 	build_file("ValidatorReport", VALIDATOR_REPORT_ABI, "validator_report.rs");
+
+	build_test_contracts();
 }

ethcore/native_contracts/src/lib.rs

@@ -29,6 +29,8 @@ mod secretstore_acl_storage;
 mod validator_set;
 mod validator_report;
 
+pub mod test_contracts;
+
 pub use self::registry::Registry;
 pub use self::service_transaction::ServiceTransactionChecker;
 pub use self::secretstore_acl_storage::SecretStoreAclStorage;

ethcore/native_contracts/src/test_contracts/mod.rs

@@ -0,0 +1,21 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Contracts used for testing.
+
+pub mod validator_set;
+
+pub use self::validator_set::ValidatorSet;

ethcore/native_contracts/src/test_contracts/validator_set.rs

@@ -0,0 +1,21 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+#![allow(unused_mut, unused_variables, unused_imports)]
+
+//! Test validator set contract.
+
+include!(concat!(env!("OUT_DIR"), "/test_validator_set.rs"));

ethcore/src/blockchain/blockchain.rs

@@ -445,7 +445,12 @@ impl<'a> Iterator for EpochTransitionIter<'a> {
 						let is_in_canon_chain = self.chain.block_hash(transition.block_number)
 							.map_or(false, |hash| hash == transition.block_hash);
 
-						if is_in_canon_chain {
+						// if the transition is within the block gap, there will only be
+						// one candidate, and it will be from a snapshot restored from.
+						let is_ancient = self.chain.first_block_number()
+							.map_or(false, |first| first > transition.block_number);
+
+						if is_ancient || is_in_canon_chain {
 							return Some((transitions.number, transition))
 						}
 					}
@@ -864,6 +869,7 @@ impl BlockChain {
 	}
 
 	/// Iterate over all epoch transitions.
+	/// This will only return transitions within the canonical chain.
 	pub fn epoch_transitions(&self) -> EpochTransitionIter {
 		let iter = self.db.iter_from_prefix(db::COL_EXTRA, &EPOCH_KEY_PREFIX[..]);
 		EpochTransitionIter {
@@ -872,6 +878,16 @@ impl BlockChain {
 		}
 	}
 
+	/// Get a specific epoch transition by epoch number and provided block hash.
+	pub fn epoch_transition(&self, epoch_num: u64, block_hash: H256) -> Option<EpochTransition> {
+		trace!(target: "blockchain", "Loading epoch {} transition at block {}",
+			epoch_num, block_hash);
+
+		self.db.read(db::COL_EXTRA, &epoch_num).and_then(|transitions: EpochTransitions| {
+			transitions.candidates.into_iter().find(|c| c.block_hash == block_hash)
+		})
+	}
+
 	/// Add a child to a given block. Assumes that the block hash is in
 	/// the chain and the child's parent is this block.
 	///

ethcore/src/client/ancient_import.rs

@@ -0,0 +1,68 @@
+// Copyright 2015-2017 Parity Technologies (UK) Ltd.
+// This file is part of Parity.
+
+// Parity is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Parity is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Parity.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Helper for ancient block import.
+
+use std::sync::Arc;
+
+use engines::{Engine, EpochVerifier, EpochChange};
+use error::Error;
+use header::Header;
+
+use rand::Rng;
+use util::RwLock;
+
+// do "heavy" verification on ~1/50 blocks, randomly sampled.
+const HEAVY_VERIFY_RATE: f32 = 0.02;
+
+/// Ancient block verifier: import an ancient sequence of blocks in order from a starting
+/// epoch.
+pub struct AncientVerifier {
+	cur_verifier: RwLock<Box<EpochVerifier>>,
+	engine: Arc<Engine>,
+}
+
+impl AncientVerifier {
+	/// Create a new ancient block verifier with the given engine and initial verifier.
+	pub fn new(engine: Arc<Engine>, start_verifier: Box<EpochVerifier>) -> Self {
+		AncientVerifier {
+			cur_verifier: RwLock::new(start_verifier),
+			engine: engine,
+		}
+	}
+
+	/// Verify the next block header, randomly choosing whether to do heavy or light
+	/// verification. If the block is the end of an epoch, updates the epoch verifier.
+	pub fn verify<R: Rng, F: Fn(u64) -> Result<Box<EpochVerifier>, Error>>(
+		&self,
+		rng: &mut R,
+		header: &Header,
+		block: &[u8],
+		receipts: &[::receipt::Receipt],
+		load_verifier: F,
+	) -> Result<(), ::error::Error> {
+		match rng.gen::<f32>() <= HEAVY_VERIFY_RATE {
+			true => self.cur_verifier.read().verify_heavy(header)?,
+			false => self.cur_verifier.read().verify_light(header)?,
+		}
+
+		if let EpochChange::Yes(num) = self.engine.is_epoch_end(header, Some(block), Some(receipts)) {
+			*self.cur_verifier.write() = load_verifier(num)?;
+		}
+
+		Ok(())
+	}
+}