Slashing for voted-offline validators. (#541)

[Backport] Vote out offline authorities

polkadot/api/src/full.rs

@@ -25,8 +25,11 @@ use state_machine;
 
 use runtime::Address;
 use runtime_primitives::traits::AuxLookup;
-use primitives::{AccountId, Block, Header, BlockId, Hash, Index, SessionKey, Timestamp, UncheckedExtrinsic};
-use primitives::parachain::{CandidateReceipt, DutyRoster, Id as ParaId};
+use primitives::{
+	AccountId, Block, Header, BlockId, Hash, Index, InherentData,
+	SessionKey, Timestamp, UncheckedExtrinsic,
+};
+use primitives::parachain::{DutyRoster, Id as ParaId};
 
 use {BlockBuilder, PolkadotApi, LocalPolkadotApi, ErrorKind, Error, Result};
 
@@ -132,20 +135,20 @@ impl<B: LocalBackend<Block>> PolkadotApi for Client<B, LocalCallExecutor<B, Nati
 		with_runtime!(self, at, || ::runtime::Parachains::parachain_head(parachain))
 	}
 
-	fn build_block(&self, at: &BlockId, timestamp: Timestamp, new_heads: Vec<CandidateReceipt>) -> Result<Self::BlockBuilder> {
+	fn build_block(&self, at: &BlockId, inherent_data: InherentData) -> Result<Self::BlockBuilder> {
 		let mut block_builder = self.new_block_at(at)?;
-		for inherent in self.inherent_extrinsics(at, timestamp, new_heads)? {
+		for inherent in self.inherent_extrinsics(at, inherent_data)? {
 			block_builder.push(inherent)?;
 		}
 
 		Ok(block_builder)
 	}
 
-	fn inherent_extrinsics(&self, at: &BlockId, timestamp: Timestamp, new_heads: Vec<CandidateReceipt>) -> Result<Vec<UncheckedExtrinsic>> {
+	fn inherent_extrinsics(&self, at: &BlockId, inherent_data: InherentData) -> Result<Vec<UncheckedExtrinsic>> {
 		use codec::{Encode, Decode};
 
 		with_runtime!(self, at, || {
-			let extrinsics = ::runtime::inherent_extrinsics(timestamp, new_heads);
+			let extrinsics = ::runtime::inherent_extrinsics(inherent_data);
 			extrinsics.into_iter()
 				.map(|x| x.encode()) // get encoded representation
 				.map(|x| Decode::decode(&mut &x[..])) // get byte-vec equivalent to extrinsic
@@ -216,7 +219,11 @@ mod tests {
 		let client = client();
 
 		let id = BlockId::number(0);
-		let block_builder = client.build_block(&id, 1_000_000, Vec::new()).unwrap();
+		let block_builder = client.build_block(&id, InherentData {
+			timestamp: 1_000_000,
+			parachain_heads: Vec::new(),
+			offline_indices: Vec::new(),
+		}).unwrap();
 		let block = block_builder.bake().unwrap();
 
 		assert_eq!(block.header.number, 1);
@@ -228,7 +235,11 @@ mod tests {
 		let client = client();
 
 		let id = BlockId::number(0);
-		let inherent = client.inherent_extrinsics(&id, 1_000_000, Vec::new()).unwrap();
+		let inherent = client.inherent_extrinsics(&id, InherentData {
+			timestamp: 1_000_000,
+			parachain_heads: Vec::new(),
+			offline_indices: Vec::new(),
+		}).unwrap();
 
 		let mut block_builder = client.new_block_at(&id).unwrap();
 		for extrinsic in inherent {

polkadot/api/src/lib.rs

@@ -38,10 +38,12 @@ extern crate substrate_keyring as keyring;
 pub mod full;
 pub mod light;
 
-use primitives::{AccountId, Block, BlockId, Hash, Index, SessionKey, Timestamp,
-	UncheckedExtrinsic};
+use primitives::{
+	AccountId, Block, BlockId, Hash, Index, SessionKey, Timestamp,
+	UncheckedExtrinsic, InherentData,
+};
 use runtime::Address;
-use primitives::parachain::{CandidateReceipt, DutyRoster, Id as ParaId};
+use primitives::parachain::{DutyRoster, Id as ParaId};
 
 error_chain! {
 	errors {
@@ -128,11 +130,11 @@ pub trait PolkadotApi {
 	fn evaluate_block(&self, at: &BlockId, block: Block) -> Result<bool>;
 
 	/// Build a block on top of the given, with inherent extrinsics pre-pushed.
-	fn build_block(&self, at: &BlockId, timestamp: Timestamp, new_heads: Vec<CandidateReceipt>) -> Result<Self::BlockBuilder>;
+	fn build_block(&self, at: &BlockId, inherent_data: InherentData) -> Result<Self::BlockBuilder>;
 
 	/// Attempt to produce the (encoded) inherent extrinsics for a block being built upon the given.
 	/// This may vary by runtime and will fail if a runtime doesn't follow the same API.
-	fn inherent_extrinsics(&self, at: &BlockId, timestamp: Timestamp, new_heads: Vec<CandidateReceipt>) -> Result<Vec<UncheckedExtrinsic>>;
+	fn inherent_extrinsics(&self, at: &BlockId, inherent_data: InherentData) -> Result<Vec<UncheckedExtrinsic>>;
 }
 
 /// Mark for all Polkadot API implementations, that are making use of state data, stored locally.

polkadot/api/src/light.rs

@@ -20,9 +20,12 @@ use std::sync::Arc;
 use client::backend::{Backend, RemoteBackend};
 use client::{Client, CallExecutor};
 use codec::Decode;
-use primitives::{AccountId, Block, BlockId, Hash, Index, SessionKey, Timestamp, UncheckedExtrinsic};
+use primitives::{
+	AccountId, Block, BlockId, Hash, Index, InherentData,
+	SessionKey, Timestamp, UncheckedExtrinsic,
+};
 use runtime::Address;
-use primitives::parachain::{CandidateReceipt, DutyRoster, Id as ParaId};
+use primitives::parachain::{DutyRoster, Id as ParaId};
 use {PolkadotApi, BlockBuilder, RemotePolkadotApi, Result, ErrorKind};
 
 /// Light block builder. TODO: make this work (efficiently)
@@ -92,11 +95,11 @@ impl<B: Backend<Block>, E: CallExecutor<Block>> PolkadotApi for RemotePolkadotAp
 		Err(ErrorKind::UnknownRuntime.into())
 	}
 
-	fn build_block(&self, _at: &BlockId, _timestamp: Timestamp, _new_heads: Vec<CandidateReceipt>) -> Result<Self::BlockBuilder> {
+	fn build_block(&self, _at: &BlockId, _inherent: InherentData) -> Result<Self::BlockBuilder> {
 		Err(ErrorKind::UnknownRuntime.into())
 	}
 
-	fn inherent_extrinsics(&self, _at: &BlockId, _timestamp: Timestamp, _new_heads: Vec<CandidateReceipt>) -> Result<Vec<Vec<u8>>> {
+	fn inherent_extrinsics(&self, _at: &BlockId, _inherent: InherentData) -> Result<Vec<Vec<u8>>> {
 		Err(ErrorKind::UnknownRuntime.into())
 	}
 }

polkadot/consensus/Cargo.toml

@@ -11,7 +11,7 @@ ed25519 = { path = "../../substrate/ed25519" }
 error-chain = "0.12"
 log = "0.3"
 exit-future = "0.1"
-rhododendron = "0.2"
+rhododendron = "0.3"
 polkadot-api = { path = "../api" }
 polkadot-parachain = { path = "../parachain" }
 polkadot-primitives = { path = "../primitives" }

polkadot/consensus/src/dynamic_inclusion.rs

@@ -74,6 +74,9 @@ impl DynamicInclusion {
 			Some(now + until)
 		}
 	}
+
+	/// Get the start instant.
+	pub fn started_at(&self) -> Instant { self.start }
 }
 
 #[cfg(test)]

polkadot/consensus/src/lib.rs

@@ -67,7 +67,7 @@ use std::time::{Duration, Instant};
 
 use codec::{Decode, Encode};
 use polkadot_api::PolkadotApi;
-use polkadot_primitives::{Hash, Block, BlockId, BlockNumber, Header, Timestamp, SessionKey};
+use polkadot_primitives::{AccountId, Hash, Block, BlockId, BlockNumber, Header, Timestamp, SessionKey};
 use polkadot_primitives::parachain::{Id as ParaId, Chain, DutyRoster, BlockData, Extrinsic as ParachainExtrinsic, CandidateReceipt, CandidateSignature};
 use primitives::AuthorityId;
 use transaction_pool::TransactionPool;
@@ -78,20 +78,26 @@ use futures::prelude::*;
 use futures::future;
 use collation::CollationFetch;
 use dynamic_inclusion::DynamicInclusion;
+use parking_lot::RwLock;
 
 pub use self::collation::{validate_collation, Collators};
 pub use self::error::{ErrorKind, Error};
+pub use self::offline_tracker::OfflineTracker;
 pub use self::shared_table::{SharedTable, StatementProducer, ProducedStatements, Statement, SignedStatement, GenericStatement};
 pub use service::Service;
 
 mod dynamic_inclusion;
 mod evaluation;
 mod error;
+mod offline_tracker;
 mod service;
 mod shared_table;
 
 pub mod collation;
 
+/// Shared offline validator tracker.
+pub type SharedOfflineTracker = Arc<RwLock<OfflineTracker>>;
+
 // block size limit.
 const MAX_TRANSACTIONS_SIZE: usize = 4 * 1024 * 1024;
 
@@ -236,6 +242,8 @@ pub struct ProposerFactory<C, N, P> {
 	pub handle: TaskExecutor,
 	/// The duration after which parachain-empty blocks will be allowed.
 	pub parachain_empty_duration: Duration,
+	/// Offline-tracker.
+	pub offline: SharedOfflineTracker,
 }
 
 impl<C, N, P> bft::Environment<Block> for ProposerFactory<C, N, P>
@@ -251,10 +259,11 @@ impl<C, N, P> bft::Environment<Block> for ProposerFactory<C, N, P>
 	type Output = N::Output;
 	type Error = Error;
 
-	fn init(&self,
+	fn init(
+		&self,
 		parent_header: &Header,
 		authorities: &[AuthorityId],
-		sign_with: Arc<ed25519::Pair>
+		sign_with: Arc<ed25519::Pair>,
 	) -> Result<(Self::Proposer, Self::Input, Self::Output), Error> {
 		use runtime_primitives::traits::{Hash as HashT, BlakeTwo256};
 
@@ -265,6 +274,9 @@ impl<C, N, P> bft::Environment<Block> for ProposerFactory<C, N, P>
 		let random_seed = self.client.random_seed(&id)?;
 		let random_seed = BlakeTwo256::hash(&*random_seed);
 
+		let validators = self.client.validators(&id)?;
+		self.offline.write().note_new_block(&validators[..]);
+
 		let (group_info, local_duty) = make_group_info(
 			duty_roster,
 			authorities,
@@ -316,6 +328,8 @@ impl<C, N, P> bft::Environment<Block> for ProposerFactory<C, N, P>
 			random_seed,
 			table,
 			transaction_pool: self.transaction_pool.clone(),
+			offline: self.offline.clone(),
+			validators,
 			_drop_signal: drop_signal,
 		};
 
@@ -370,9 +384,22 @@ pub struct Proposer<C: PolkadotApi> {
 	random_seed: Hash,
 	table: Arc<SharedTable>,
 	transaction_pool: Arc<TransactionPool<C>>,
+	offline: SharedOfflineTracker,
+	validators: Vec<AccountId>,
 	_drop_signal: exit_future::Signal,
 }
 
+impl<C: PolkadotApi + Send + Sync> Proposer<C> {
+	fn primary_index(&self, round_number: usize, len: usize) -> usize {
+		use primitives::uint::U256;
+
+		let big_len = U256::from(len);
+		let offset = U256::from_big_endian(&self.random_seed.0) % big_len;
+		let offset = offset.low_u64() as usize + round_number;
+		offset % len
+	}
+}
+
 impl<C> bft::Proposer<Block> for Proposer<C>
 	where
 		C: PolkadotApi + Send + Sync,
@@ -408,6 +435,8 @@ impl<C> bft::Proposer<Block> for Proposer<C>
 			client: self.client.clone(),
 			transaction_pool: self.transaction_pool.clone(),
 			table: self.table.clone(),
+			offline: self.offline.clone(),
+			validators: self.validators.clone(),
 			timing,
 		})
 	}
@@ -482,6 +511,13 @@ impl<C> bft::Proposer<Block> for Proposer<C>
 			includability_tracker.join(temporary_delay)
 		};
 
+		// refuse to vote if this block says a validator is offline that we
+		// think isn't.
+		let offline = proposal.noted_offline();
+		if !self.offline.read().check_consistency(&self.validators[..], offline) {
+			return Box::new(futures::empty());
+		}
+
 		// evaluate whether the block is actually valid.
 		// TODO: is it better to delay this until the delays are finished?
 		let evaluated = self.client
@@ -503,13 +539,8 @@ impl<C> bft::Proposer<Block> for Proposer<C>
 	}
 
 	fn round_proposer(&self, round_number: usize, authorities: &[AuthorityId]) -> AuthorityId {
-		use primitives::uint::U256;
-
-		let len: U256 = authorities.len().into();
-		let offset = U256::from_big_endian(&self.random_seed.0) % len;
-		let offset = offset.low_u64() as usize + round_number;
-
-		let proposer = authorities[offset % authorities.len()].clone();
+		let offset = self.primary_index(round_number, authorities.len());
+		let proposer = authorities[offset].clone();
 		trace!(target: "bft", "proposer for round {} is {}", round_number, proposer);
 
 		proposer
@@ -578,6 +609,34 @@ impl<C> bft::Proposer<Block> for Proposer<C>
 				.expect("locally signed extrinsic is valid; qed");
 		}
 	}
+
+	fn on_round_end(&self, round_number: usize, was_proposed: bool) {
+		let primary_validator = self.validators[
+			self.primary_index(round_number, self.validators.len())
+		];
+
+		// alter the message based on whether we think the empty proposer was forced to skip the round.
+		// this is determined by checking if our local validator would have been forced to skip the round.
+		let consider_online = was_proposed || {
+			let forced_delay = self.dynamic_inclusion.acceptable_in(Instant::now(), self.table.includable_count());
+			match forced_delay {
+				None => info!(
+					"Potential Offline Validator: {:?} failed to propose during assigned slot: {}",
+					primary_validator,
+					round_number,
+				),
+				Some(_) => info!(
+					"Potential Offline Validator {:?} potentially forced to skip assigned slot: {}",
+					primary_validator,
+					round_number,
+				),
+			}
+
+			forced_delay.is_some()
+		};
+
+		self.offline.write().note_round_end(primary_validator, consider_online);
+	}
 }
 
 fn current_timestamp() -> Timestamp {
@@ -634,16 +693,42 @@ pub struct CreateProposal<C: PolkadotApi>  {
 	transaction_pool: Arc<TransactionPool<C>>,
 	table: Arc<SharedTable>,
 	timing: ProposalTiming,
+	validators: Vec<AccountId>,
+	offline: SharedOfflineTracker,
 }
 
 impl<C> CreateProposal<C> where C: PolkadotApi {
 	fn propose_with(&self, candidates: Vec<CandidateReceipt>) -> Result<Block, Error> {
 		use polkadot_api::BlockBuilder;
 		use runtime_primitives::traits::{Hash as HashT, BlakeTwo256};
+		use polkadot_primitives::InherentData;
+
+		const MAX_VOTE_OFFLINE_SECONDS: Duration = Duration::from_secs(60);
 
 		// TODO: handle case when current timestamp behind that in state.
 		let timestamp = current_timestamp();
-		let mut block_builder = self.client.build_block(&self.parent_id, timestamp, candidates)?;
+
+		let elapsed_since_start = self.timing.dynamic_inclusion.started_at().elapsed();
+		let offline_indices = if elapsed_since_start > MAX_VOTE_OFFLINE_SECONDS {
+			Vec::new()
+		} else {
+			self.offline.read().reports(&self.validators[..])
+		};
+
+		if !offline_indices.is_empty() {
+			info!(
+				"Submitting offline validators {:?} for slash-vote",
+				offline_indices.iter().map(|&i| self.validators[i as usize]).collect::<Vec<_>>(),
+			)
+		}
+
+		let inherent_data = InherentData {
+			timestamp,
+			parachain_heads: candidates,
+			offline_indices,
+		};
+
+		let mut block_builder = self.client.build_block(&self.parent_id, inherent_data)?;
 
 		{
 			let mut unqueue_invalid = Vec::new();

polkadot/consensus/src/offline_tracker.rs

@@ -0,0 +1,137 @@
+// Copyright 2018 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot 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.
+
+// Polkadot 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 Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Tracks offline validators.
+
+use polkadot_primitives::AccountId;
+
+use std::collections::HashMap;
+use std::time::{Instant, Duration};
+
+// time before we report a validator.
+const REPORT_TIME: Duration = Duration::from_secs(60 * 5);
+
+struct Observed {
+	last_round_end: Instant,
+	offline_since: Instant,
+}
+
+impl Observed {
+	fn new() -> Observed {
+		let now = Instant::now();
+		Observed {
+			last_round_end: now,
+			offline_since: now,
+		}
+	}
+
+	fn note_round_end(&mut self, was_online: bool) {
+		let now = Instant::now();
+
+		self.last_round_end = now;
+		if was_online {
+			self.offline_since = now;
+		}
+	}
+
+	fn is_active(&self) -> bool {
+		// can happen if clocks are not monotonic
+		if self.offline_since > self.last_round_end { return true }
+		self.last_round_end.duration_since(self.offline_since) < REPORT_TIME
+	}
+}
+
+/// Tracks offline validators and can issue a report for those offline.
+pub struct OfflineTracker {
+	observed: HashMap<AccountId, Observed>,
+}
+
+impl OfflineTracker {
+	/// Create a new tracker.
+	pub fn new() -> Self {
+		OfflineTracker { observed: HashMap::new() }
+	}
+
+	/// Note new consensus is starting with the given set of validators.
+	pub fn note_new_block(&mut self, validators: &[AccountId]) {
+		use std::collections::HashSet;
+
+		let set: HashSet<_> = validators.iter().cloned().collect();
+		self.observed.retain(|k, _| set.contains(k));
+	}
+
+	/// Note that a round has ended.
+	pub fn note_round_end(&mut self, validator: AccountId, was_online: bool) {
+		self.observed.entry(validator)
+			.or_insert_with(Observed::new)
+			.note_round_end(was_online);
+	}
+
+	/// Generate a vector of indices for offline account IDs.
+	pub fn reports(&self, validators: &[AccountId]) -> Vec<u32> {
+		validators.iter()
+			.enumerate()
+			.filter_map(|(i, v)| if self.is_online(v) {
+				None
+			} else {
+				Some(i as u32)
+			})
+			.collect()
+	}
+
+	/// Whether reports on a validator set are consistent with our view of things.
+	pub fn check_consistency(&self, validators: &[AccountId], reports: &[u32]) -> bool {
+		reports.iter().cloned().all(|r| {
+			let v = match validators.get(r as usize) {
+				Some(v) => v,
+				None => return false,
+			};
+
+			// we must think all validators reported externally are offline.
+			let thinks_online = self.is_online(v);
+			!thinks_online
+		})
+	}
+
+	fn is_online(&self, v: &AccountId) -> bool {
+		self.observed.get(v).map(Observed::is_active).unwrap_or(true)
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[test]
+	fn validator_offline() {
+		let mut tracker = OfflineTracker::new();
+		let v = [0; 32].into();
+		let v2 = [1; 32].into();
+		let v3 = [2; 32].into();
+		tracker.note_round_end(v, true);
+		tracker.note_round_end(v2, true);
+		tracker.note_round_end(v3, true);
+
+		let slash_time = REPORT_TIME + Duration::from_secs(5);
+		tracker.observed.get_mut(&v).unwrap().offline_since -= slash_time;
+		tracker.observed.get_mut(&v2).unwrap().offline_since -= slash_time;
+
+		assert_eq!(tracker.reports(&[v, v2, v3]), vec![0, 1]);
+
+		tracker.note_new_block(&[v, v3]);
+		assert_eq!(tracker.reports(&[v, v2, v3]), vec![0]);
+	}
+}

polkadot/consensus/src/service.rs

@@ -113,6 +113,9 @@ impl Service {
 			N::TableRouter: Send + 'static,
 			<N::Collation as IntoFuture>::Future: Send + 'static,
 	{
+		use parking_lot::RwLock;
+		use super::OfflineTracker;
+
 		let (signal, exit) = ::exit_future::signal();
 		let thread = thread::spawn(move || {
 			let mut runtime = LocalRuntime::new().expect("Could not create local runtime");
@@ -125,6 +128,7 @@ impl Service {
 				network,
 				parachain_empty_duration,
 				handle: thread_pool,
+				offline: Arc::new(RwLock::new(OfflineTracker::new())),
 			};
 			let bft_service = Arc::new(BftService::new(client.clone(), key, factory));
 

polkadot/network/Cargo.toml

@@ -17,4 +17,4 @@ ed25519 = { path = "../../substrate/ed25519" }
 futures = "0.1"
 tokio = "0.1.7"
 log = "0.4"
-rhododendron = "0.2"
+rhododendron = "0.3"

polkadot/primitives/src/lib.rs

@@ -120,3 +120,32 @@ impl Encode for Log {
 		self.0.encode_to(dest)
 	}
 }
+
+/// Inherent data to include in a block.
+pub struct InherentData {
+	/// Current timestamp.
+	pub timestamp: Timestamp,
+	/// Parachain heads update.
+	pub parachain_heads: Vec<::parachain::CandidateReceipt>,
+	/// Indices of offline validators.
+	pub offline_indices: Vec<u32>,
+}
+
+impl Decode for InherentData {
+	fn decode<I: Input>(input: &mut I) -> Option<Self> {
+		let (timestamp, parachain_heads, offline_indices) = Decode::decode(input)?;
+		Some(InherentData {
+			timestamp,
+			parachain_heads,
+			offline_indices,
+		})
+	}
+}
+
+impl Encode for InherentData {
+	fn encode_to<T: Output>(&self, dest: &mut T) {
+		self.timestamp.encode_to(dest);
+		self.parachain_heads.encode_to(dest);
+		self.offline_indices.encode_to(dest);
+	}
+}

polkadot/runtime/src/checked_block.rs

@@ -16,9 +16,10 @@
 
 //! Typesafe block interaction.
 
-use super::{Call, Block, TIMESTAMP_SET_POSITION, PARACHAINS_SET_POSITION};
+use super::{Call, Block, TIMESTAMP_SET_POSITION, PARACHAINS_SET_POSITION, NOTE_OFFLINE_POSITION};
 use timestamp::Call as TimestampCall;
 use parachains::Call as ParachainsCall;
+use session::Call as SessionCall;
 use primitives::parachain::CandidateReceipt;
 
 /// Provides a type-safe wrapper around a structurally valid block.
@@ -47,6 +48,7 @@ impl CheckedBlock {
 		});
 
 		if !has_heads { return Err(block) }
+
 		Ok(CheckedBlock {
 			inner: block,
 			file_line: None,
@@ -88,6 +90,14 @@ impl CheckedBlock {
 		}
 	}
 
+	/// Extract the noted offline validator indices (if any) from the block.
+	pub fn noted_offline(&self) -> &[u32] {
+		self.inner.extrinsics.get(NOTE_OFFLINE_POSITION as usize).and_then(|xt| match xt.extrinsic.function {
+			Call::Session(SessionCall::note_offline(ref x)) => Some(&x[..]),
+			_ => None,
+		}).unwrap_or(&[])
+	}
+
 	/// Convert into inner block.
 	pub fn into_inner(self) -> Block { self.inner }
 }

polkadot/runtime/src/lib.rs

@@ -85,6 +85,8 @@ pub use primitives::Header;
 pub const TIMESTAMP_SET_POSITION: u32 = 0;
 /// The position of the parachains set extrinsic.
 pub const PARACHAINS_SET_POSITION: u32 = 1;
+/// The position of the offline nodes noting extrinsic.
+pub const NOTE_OFFLINE_POSITION: u32 = 2;
 
 /// The address format for describing accounts.
 pub type Address = staking::Address<Concrete>;
@@ -110,7 +112,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	spec_name: ver_str!("polkadot"),
 	impl_name: ver_str!("parity-polkadot"),
 	authoring_version: 1,
-	spec_version: 2,
+	spec_version: 3,
 	impl_version: 0,
 };
 
@@ -160,6 +162,7 @@ impl Convert<AccountId, SessionKey> for SessionKeyConversion {
 }
 
 impl session::Trait for Concrete {
+	const NOTE_OFFLINE_POSITION: u32 = NOTE_OFFLINE_POSITION;
 	type ConvertAccountIdToSessionKey = SessionKeyConversion;
 	type OnSessionChange = Staking;
 }
@@ -247,7 +250,7 @@ pub mod api {
 		apply_extrinsic => |extrinsic| super::Executive::apply_extrinsic(extrinsic),
 		execute_block => |block| super::Executive::execute_block(block),
 		finalise_block => |()| super::Executive::finalise_block(),
-		inherent_extrinsics => |(timestamp, heads)| super::inherent_extrinsics(timestamp, heads),
+		inherent_extrinsics => |inherent| super::inherent_extrinsics(inherent),
 		validator_count => |()| super::Session::validator_count(),
 		validators => |()| super::Session::validators()
 	);

polkadot/runtime/src/parachains.rs

@@ -265,6 +265,7 @@ mod tests {
 		type Header = Header;
 	}
 	impl session::Trait for Test {
+		const NOTE_OFFLINE_POSITION: u32 = 1;
 		type ConvertAccountIdToSessionKey = Identity;
 		type OnSessionChange = ();
 	}

polkadot/runtime/src/utils.rs

@@ -19,30 +19,33 @@
 use rstd::prelude::*;
 use super::{Call, UncheckedExtrinsic, Extrinsic, Staking};
 use runtime_primitives::traits::{Checkable, AuxLookup};
-use primitives::parachain::CandidateReceipt;
 use timestamp::Call as TimestampCall;
 use parachains::Call as ParachainsCall;
+use session::Call as SessionCall;
 
 /// Produces the list of inherent extrinsics.
-pub fn inherent_extrinsics(timestamp: ::primitives::Timestamp, parachain_heads: Vec<CandidateReceipt>) -> Vec<UncheckedExtrinsic> {
-	vec![
-		UncheckedExtrinsic::new(
-			Extrinsic {
-				signed: Default::default(),
-				function: Call::Timestamp(TimestampCall::set(timestamp)),
-				index: 0,
-			},
-			Default::default()
-		),
-		UncheckedExtrinsic::new(
-			Extrinsic {
-				signed: Default::default(),
-				function: Call::Parachains(ParachainsCall::set_heads(parachain_heads)),
-				index: 0,
-			},
-			Default::default()
-		)
-	]
+pub fn inherent_extrinsics(data: ::primitives::InherentData) -> Vec<UncheckedExtrinsic> {
+	let make_inherent = |function|	UncheckedExtrinsic::new(
+		Extrinsic {
+			signed: Default::default(),
+			function,
+			index: 0,
+		},
+		Default::default(),
+	);
+
+	let mut inherent = vec![
+		make_inherent(Call::Timestamp(TimestampCall::set(data.timestamp))),
+		make_inherent(Call::Parachains(ParachainsCall::set_heads(data.parachain_heads))),
+	];
+
+	if !data.offline_indices.is_empty() {
+		inherent.push(make_inherent(
+			Call::Session(SessionCall::note_offline(data.offline_indices))
+		));
+	}
+
+	inherent
 }
 
 /// Checks an unchecked extrinsic for validity.

polkadot/runtime/wasm/Cargo.lock

@@ -416,7 +416,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "libc 0.2.41 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "smallvec 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "smallvec 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -691,8 +691,11 @@ dependencies = [
 
 [[package]]
 name = "smallvec"
-version = "0.6.1"
+version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "unreachable 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
 
 [[package]]
 name = "stable_deref_trait"
@@ -1213,7 +1216,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 "checksum serde 1.0.64 (registry+https://github.com/rust-lang/crates.io-index)" = "fba5be06346c5200249c8c8ca4ccba4a09e8747c71c16e420bd359a0db4d8f91"
 "checksum serde_derive 1.0.64 (registry+https://github.com/rust-lang/crates.io-index)" = "79e4620ba6fbe051fc7506fab6f84205823564d55da18d55b695160fb3479cd8"
-"checksum smallvec 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)" = "03dab98ab5ded3a8b43b2c80751194608d0b2aa0f1d46cf95d1c35e192844aa7"
+"checksum smallvec 0.6.4 (registry+https://github.com/rust-lang/crates.io-index)" = "211a489e65e94b103926d2054ae515a1cdb5d515ea0ef414fee23b7e043ce748"
 "checksum stable_deref_trait 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "15132e0e364248108c5e2c02e3ab539be8d6f5d52a01ca9bbf27ed657316f02b"
 "checksum syn 0.14.1 (registry+https://github.com/rust-lang/crates.io-index)" = "6dfd71b2be5a58ee30a6f8ea355ba8290d397131c00dfa55c3d34e6e13db5101"
 "checksum termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "689a3bdfaab439fd92bc87df5c4c78417d3cbe537487274e9b0b2dce76e92096"

polkadot/transaction-pool/src/lib.rs

@@ -286,7 +286,7 @@ impl<'a, A> txpool::Verifier<UncheckedExtrinsic> for Verifier<'a, A> where
 
 		let encoded = uxt.encode();
 		let (encoded_size, hash) = (encoded.len(), BlakeTwo256::hash(&encoded));
-		
+
 		debug!(target: "transaction-pool", "Transaction submitted: {}", ::substrate_primitives::hexdisplay::HexDisplay::from(&encoded));
 
 		let inner = match uxt.clone().check_with(|a| self.lookup(a)) {
@@ -446,10 +446,10 @@ mod tests {
 	use substrate_keyring::Keyring::{self, *};
 	use codec::{Decode, Encode};
 	use polkadot_api::{PolkadotApi, BlockBuilder, Result};
-	use primitives::{AccountId, AccountIndex, Block, BlockId, Hash, Index, SessionKey, Timestamp,
+	use primitives::{AccountId, AccountIndex, Block, BlockId, Hash, Index, SessionKey,
 		UncheckedExtrinsic as FutureProofUncheckedExtrinsic};
 	use runtime::{RawAddress, Call, TimestampCall, BareExtrinsic, Extrinsic, UncheckedExtrinsic};
-	use primitives::parachain::{CandidateReceipt, DutyRoster, Id as ParaId};
+	use primitives::parachain::{DutyRoster, Id as ParaId};
 	use substrate_runtime_primitives::{MaybeUnsigned, generic};
 
 	struct TestBlockBuilder;
@@ -494,8 +494,8 @@ mod tests {
 		fn active_parachains(&self, _at: &BlockId) -> Result<Vec<ParaId>> { unimplemented!() }
 		fn parachain_code(&self, _at: &BlockId, _parachain: ParaId) -> Result<Option<Vec<u8>>> { unimplemented!() }
 		fn parachain_head(&self, _at: &BlockId, _parachain: ParaId) -> Result<Option<Vec<u8>>> { unimplemented!() }
-		fn build_block(&self, _at: &BlockId, _timestamp: Timestamp, _new_heads: Vec<CandidateReceipt>) -> Result<Self::BlockBuilder> { unimplemented!() }
-		fn inherent_extrinsics(&self, _at: &BlockId, _timestamp: Timestamp, _new_heads: Vec<CandidateReceipt>) -> Result<Vec<Vec<u8>>> { unimplemented!() }
+		fn build_block(&self, _at: &BlockId, _inherent: ::primitives::InherentData) -> Result<Self::BlockBuilder> { unimplemented!() }
+		fn inherent_extrinsics(&self, _at: &BlockId, _inherent: ::primitives::InherentData) -> Result<Vec<Vec<u8>>> { unimplemented!() }
 
 		fn index(&self, _at: &BlockId, _account: AccountId) -> Result<Index> {
 			Ok((_account[0] as u32) + number_of(_at))