Slashing for voted-offline validators. (#541)

[Backport] Vote out offline authorities

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.