Invulnerabiity from slashing for certain validators (#1355)

* Invulnerabiity from slashing

* Update srml/staking/src/lib.rs

Co-Authored-By: gavofyork <github@gavwood.com>

substrate/core/test-runtime/wasm/Cargo.lock

@@ -1112,8 +1112,10 @@ version = "0.1.0"
 dependencies = [
  "error-chain 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.25 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-codec 2.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-codec-derive 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 0.1.0",
  "sr-version 0.1.0",
  "substrate-primitives 0.1.0",

substrate/node/cli/src/chain_spec.rs

@@ -86,6 +86,7 @@ fn staging_testnet_config_genesis() -> GenesisConfig {
 			bonding_duration: 60 * MINUTES,
 			offline_slash_grace: 4,
 			minimum_validator_count: 4,
+			invulnerables: initial_authorities.iter().cloned().map(Into::into).collect(),
 		}),
 		democracy: Some(DemocracyConfig {
 			launch_period: 10 * MINUTES,    // 1 day per public referendum
@@ -211,6 +212,7 @@ pub fn testnet_genesis(
 			current_offline_slash: 0,
 			current_session_reward: 0,
 			offline_slash_grace: 0,
+			invulnerables: initial_authorities.iter().cloned().map(Into::into).collect(),
 		}),
 		democracy: Some(DemocracyConfig {
 			launch_period: 9,

substrate/node/executor/src/lib.rs

@@ -252,6 +252,7 @@ mod tests {
 				current_offline_slash: 0,
 				current_session_reward: 0,
 				offline_slash_grace: 0,
+				invulnerables: vec![alice(), bob(), Charlie.to_raw_public().into()],
 			}),
 			democracy: Some(Default::default()),
 			council_seats: Some(Default::default()),
@@ -312,9 +313,9 @@ mod tests {
 			1,
 			GENESIS_HASH.into(),
 			if support_changes_trie {
-				hex!("bc4bdc45ba03402f9b4c7ec09834065c57205b1742bf2469ab9fc54544d8d002").into()
+				hex!("0bc6c118c326c65da9d0f93199f471aab4f636cfe87ab9a56c823024ca83995a").into()
 			} else {
-				hex!("6bfbf71fa08d99f2488e295807059269cbc43ea21af3316a92406974593a1fc2").into()
+				hex!("58e1f1493e311d9b1fef3660426ee289736c38eb6f7d98911551c51765163056").into()
 			},
 			if support_changes_trie {
 				vec![changes_trie_log(
@@ -340,7 +341,7 @@ mod tests {
 		construct_block(
 			2,
 			block1(false).1,
-			hex!("24f8ac99a6d98e9b53f4f6ef6ffdd12ba53ea3f247200a8126fa69c4b5047fbc").into(),
+			hex!("ced5607b16774cdbf750f8f7f0a99cd4afd7eb14db376a44bb8656f2ce02b18e").into(),
 			vec![ // session changes here, so we add a grandpa change signal log.
 				Log::from(::grandpa::RawLog::AuthoritiesChangeSignal(0, vec![
 					(Keyring::One.to_raw_public().into(), 1),
@@ -369,7 +370,7 @@ mod tests {
 		construct_block(
 			1,
 			GENESIS_HASH.into(),
-			hex!("7b7d3b509a444cdf214825d3354507823a4c91eafa493f0956448881a81ab797").into(),
+			hex!("8a506a6f72c7efb75fd069a8c4f57c8e0b6b5adbea9646522bda64d4c78f5412").into(),
 			vec![],
 			vec![
 				CheckedExtrinsic {
@@ -659,7 +660,7 @@ mod tests {
 		let b = construct_block(
 			1,
 			GENESIS_HASH.into(),
-			hex!("bfc8051f91071149cca8b8dca6290fdb82eda6868d48cfed25f8ca38ed3a1049").into(),
+			hex!("ce21753c3f806443c2758c982850861708054b65097fed82689e7b16cd5d6e24").into(),
 			vec![],
 			vec![
 				CheckedExtrinsic {

substrate/node/runtime/wasm/Cargo.lock

@@ -1472,8 +1472,10 @@ version = "0.1.0"
 dependencies = [
  "error-chain 0.12.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "futures 0.1.25 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-codec 2.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-codec-derive 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parking_lot 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "sr-primitives 0.1.0",
  "sr-version 0.1.0",
  "substrate-primitives 0.1.0",

substrate/srml/staking/src/lib.rs

@@ -224,6 +224,11 @@ decl_module! {
 			let new: u32 = new.into();
 			<OfflineSlashGrace<T>>::put(new);
 		}
+
+		/// Set the validators who cannot be slashed (if any).
+		fn set_invulnerables(validators: Vec<T::AccountId>) {
+			<Invulerables<T>>::put(validators);
+		}
 	}
 }
 
@@ -260,6 +265,10 @@ decl_storage! {
 		/// The length of the bonding duration in blocks.
 		pub BondingDuration get(bonding_duration) config(): T::BlockNumber = T::BlockNumber::sa(1000);
 
+		/// Any validators that may never be slashed or forcible kicked. It's a Vec since they're easy to initialise
+		/// and the performance hit is minimal (we expect no more than four invulnerables) and restricted to testnets.
+		pub Invulerables get(invulnerables) config(): Vec<T::AccountId>;
+
 		/// The current era index.
 		pub CurrentEra get(current_era) config(): T::BlockNumber;
 		/// Preferences that a validator has.
@@ -501,6 +510,11 @@ impl<T: Trait> Module<T> {
 	pub fn on_offline_validator(v: T::AccountId, count: usize) {
 		use primitives::traits::CheckedShl;
 
+		// Early exit if validator is invulnerable.
+		if Self::invulnerables().contains(&v) {
+			return
+		}
+
 		for _ in 0..count {
 			let slash_count = Self::slash_count(&v);
 			<SlashCount<T>>::insert(v.clone(), slash_count + 1);

substrate/srml/staking/src/mock.rs

@@ -123,6 +123,7 @@ pub fn new_test_ext(
 		current_session_reward: reward,
 		current_offline_slash: 20,
 		offline_slash_grace: 0,
+		invulnerables: vec![],
 	}.build_storage().unwrap().0);
 	t.extend(timestamp::GenesisConfig::<Test>{
 		period: 5,

substrate/srml/staking/src/tests.rs

@@ -35,6 +35,22 @@ fn note_null_offline_should_work() {
 	});
 }
 
+#[test]
+fn invulnerability_should_work() {
+	with_externalities(&mut new_test_ext(0, 3, 3, 0, true, 10), || {
+		Staking::set_invulnerables(vec![10]);
+		Balances::set_free_balance(&10, 70);
+		assert_eq!(Staking::offline_slash_grace(), 0);
+		assert_eq!(Staking::slash_count(&10), 0);
+		assert_eq!(Balances::free_balance(&10), 70);
+		System::set_extrinsic_index(1);
+		Staking::on_offline_validator(10, 1);
+		assert_eq!(Staking::slash_count(&10), 0);
+		assert_eq!(Balances::free_balance(&10), 70);
+		assert!(Staking::forcing_new_era().is_none());
+	});
+}
+
 #[test]
 fn note_offline_should_work() {
 	with_externalities(&mut new_test_ext(0, 3, 3, 0, true, 10), || {