Introduce srml/im-online (#3079)

* Fix grammar and typo

* Extend network service

* Extend offchain API

* Support creating unsigned UncheckedExtrinsic

* Introduce srml/im-online

* Bump impl and spec version

* Fix web-wasm test

* Apply suggestions from code review

Remove parity-multiaddr dependency

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Replace transmute with from_raw_parts

* Replace PeerId.to_string() with .to_base58()

Co-Authored-By: Pierre Krieger <pierre.krieger1708@gmail.com>

* Update Cargo.lock

* Bump impl and spec version (again)

It was updated in master in the meantime.

* Apply suggestions from code review

Co-Authored-By: Sergei Pepyakin <sergei@parity.io>

* Address comments

* Add public function is_online_in_current_session()

* Bump spec_version

* Fix doc tests

* Improve comments

* Remove superfluous line

* Name parameters consistently

* Implement comments

* Switch From to TryFrom

* Use Vec instead of HashSet

* Fix tests

* Revert me: local testing

* Fix check if already sent during session

We gossip each session, hence we need to check
if already sent in this session (not era).

* Fix typos

* Consistent terminology

* Revert "Revert me: local testing"

This reverts commit 73fbc29ff3e5ed71d99436318260b4f007e837f4.

* Introduce IsMember trait

* Implement misc comments

* Remove unused function

* Fix test

* Fix external_addresses being written

* Fix test

* Add necessary trait bound

* Do not increment version

* Update lib.rs

substrate/Cargo.lock

@@ -2360,6 +2360,7 @@ dependencies = [
  "srml-executive 2.0.0",
  "srml-finality-tracker 2.0.0",
  "srml-grandpa 2.0.0",
+ "srml-im-online 0.1.0",
  "srml-indices 2.0.0",
  "srml-session 2.0.0",
  "srml-staking 2.0.0",
@@ -3844,6 +3845,21 @@ dependencies = [
  "substrate-primitives 2.0.0",
 ]
 
+[[package]]
+name = "srml-im-online"
+version = "0.1.0"
+dependencies = [
+ "parity-codec 4.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.94 (registry+https://github.com/rust-lang/crates.io-index)",
+ "sr-io 2.0.0",
+ "sr-primitives 2.0.0",
+ "sr-std 2.0.0",
+ "srml-session 2.0.0",
+ "srml-support 2.0.0",
+ "srml-system 2.0.0",
+ "substrate-primitives 2.0.0",
+]
+
 [[package]]
 name = "srml-indices"
 version = "2.0.0"
@@ -4564,6 +4580,7 @@ dependencies = [
  "sr-primitives 2.0.0",
  "substrate-client 2.0.0",
  "substrate-client-db 2.0.0",
+ "substrate-network 2.0.0",
  "substrate-offchain-primitives 2.0.0",
  "substrate-primitives 2.0.0",
  "substrate-test-runtime-client 2.0.0",
@@ -4710,6 +4727,7 @@ dependencies = [
  "node-primitives 2.0.0",
  "node-runtime 2.0.0",
  "parity-codec 4.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "parity-multiaddr 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "parking_lot 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.94 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.40 (registry+https://github.com/rust-lang/crates.io-index)",

substrate/Cargo.toml

@@ -85,6 +85,7 @@ members = [
 	"srml/system",
 	"srml/timestamp",
 	"srml/treasury",
+	"srml/im-online",
 	"node/cli",
 	"node/executor",
 	"node/primitives",

substrate/core/executor/src/wasm_executor.rs

@@ -26,6 +26,7 @@ use wasmi::{
 };
 use state_machine::{Externalities, ChildStorageKey};
 use crate::error::{Error, Result};
+use parity_codec::Encode;
 use primitives::{blake2_128, blake2_256, twox_64, twox_128, twox_256, ed25519, sr25519, Pair};
 use primitives::offchain;
 use primitives::hexdisplay::HexDisplay;
@@ -767,6 +768,42 @@ impl_function_executor!(this: FunctionExecutor<'e, E>,
 
 		Ok(offset)
 	},
+	ext_network_state(written_out: *mut u32) -> *mut u8 => {
+		let res = this.ext.offchain()
+			.map(|api| api.network_state())
+			.ok_or_else(|| "Calling unavailable API ext_network_state: wasm")?;
+
+		let encoded = res.encode();
+		let len = encoded.len() as u32;
+		let offset = this.heap.allocate(len)? as u32;
+		this.memory.set(offset, &encoded)
+			.map_err(|_| "Invalid attempt to set memory in ext_network_state")?;
+
+		this.memory.write_primitive(written_out, len)
+			.map_err(|_| "Invalid attempt to write written_out in ext_network_state")?;
+
+		Ok(offset)
+	},
+	ext_authority_pubkey(
+		kind: u32,
+		written_out: *mut u32
+	) -> *mut u8 => {
+		let kind = offchain::CryptoKind::try_from(kind)
+			.map_err(|_| "crypto kind OOB while ext_authority_pubkey: wasm")?;
+
+		let res = this.ext.offchain()
+			.map(|api| api.authority_pubkey(kind))
+			.ok_or_else(|| "Calling unavailable API ext_authority_pubkey: wasm")?;
+
+		let encoded = res.encode();
+		let len = encoded.len() as u32;
+		let offset = this.heap.allocate(len)? as u32;
+		this.memory.set(offset, &encoded)
+			.map_err(|_| "Invalid attempt to set memory in ext_authority_pubkey")?;
+		this.memory.write_primitive(written_out, len)
+			.map_err(|_| "Invalid attempt to write written_out in ext_authority_pubkey")?;
+		Ok(offset)
+	},
 	ext_decrypt(
 		key: u32,
 		kind: u32,

substrate/core/network/src/lib.rs

@@ -189,6 +189,7 @@ pub mod test;
 pub use chain::{Client as ClientHandle, FinalityProofProvider};
 pub use service::{
 	NetworkService, NetworkWorker, TransactionPool, ExHashT, ReportHandle,
+	NetworkStateInfo,
 };
 pub use protocol::{PeerInfo, Context, consensus_gossip, message, specialization};
 pub use protocol::sync::SyncState;

substrate/core/network/src/service.rs

@@ -34,6 +34,7 @@ use futures::{prelude::*, sync::mpsc};
 use log::{warn, error, info};
 use libp2p::core::{swarm::NetworkBehaviour, transport::boxed::Boxed, muxing::StreamMuxerBox};
 use libp2p::{PeerId, Multiaddr, multihash::Multihash};
+use parking_lot::Mutex;
 use peerset::PeersetHandle;
 use runtime_primitives::{traits::{Block as BlockT, NumberFor}, ConsensusEngineId};
 
@@ -86,6 +87,8 @@ impl ReportHandle {
 pub struct NetworkService<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> {
 	/// Number of peers we're connected to.
 	num_connected: Arc<AtomicUsize>,
+	/// The local external addresses.
+	external_addresses: Arc<Mutex<Vec<Multiaddr>>>,
 	/// Are we actively catching up with the chain?
 	is_major_syncing: Arc<AtomicBool>,
 	/// Local copy of the `PeerId` of the local node.
@@ -215,8 +218,11 @@ impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> NetworkWorker
 			Swarm::<B, S, H>::add_external_address(&mut swarm, addr.clone());
 		}
 
+		let external_addresses = Arc::new(Mutex::new(Vec::new()));
+
 		let service = Arc::new(NetworkService {
 			bandwidth,
+			external_addresses: external_addresses.clone(),
 			num_connected: num_connected.clone(),
 			is_major_syncing: is_major_syncing.clone(),
 			peerset: peerset_handle,
@@ -226,6 +232,7 @@ impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> NetworkWorker
 		});
 
 		Ok(NetworkWorker {
+			external_addresses,
 			num_connected,
 			is_major_syncing,
 			network_service: swarm,
@@ -295,7 +302,7 @@ impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> NetworkWorker
 	/// Get network state.
 	///
 	/// **Note**: Use this only for debugging. This API is unstable. There are warnings literaly
-	/// everywhere about this. Please don't use this function to retreive actual information.
+	/// everywhere about this. Please don't use this function to retrieve actual information.
 	pub fn network_state(&mut self) -> NetworkState {
 		let swarm = &mut self.network_service;
 		let open = swarm.user_protocol().open_peers().cloned().collect::<Vec<_>>();
@@ -487,6 +494,11 @@ impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> NetworkServic
 	pub fn num_connected(&self) -> usize {
 		self.num_connected.load(Ordering::Relaxed)
 	}
+
+	/// Returns the local external addresses.
+	pub fn external_addresses(&self) -> Vec<Multiaddr> {
+		self.external_addresses.lock().clone()
+	}
 }
 
 impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT>
@@ -500,6 +512,32 @@ impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT>
 	}
 }
 
+/// Trait for providing information about the local network state
+pub trait NetworkStateInfo {
+	/// Returns the local external addresses.
+	fn external_addresses(&self) -> Vec<Multiaddr>;
+
+	/// Returns the local Peer ID.
+	fn peer_id(&self) -> PeerId;
+}
+
+impl<B, S, H> NetworkStateInfo for NetworkService<B, S, H>
+	where
+		B: runtime_primitives::traits::Block,
+		S: NetworkSpecialization<B>,
+		H: ExHashT,
+{
+	/// Returns the local external addresses.
+	fn external_addresses(&self) -> Vec<Multiaddr> {
+		self.external_addresses.lock().clone()
+	}
+
+	/// Returns the local Peer ID.
+	fn peer_id(&self) -> PeerId {
+		self.local_peer_id.clone()
+	}
+}
+
 /// Messages sent from the `NetworkService` to the `NetworkWorker`.
 ///
 /// Each entry corresponds to a method of `NetworkService`.
@@ -520,6 +558,8 @@ enum ServerToWorkerMsg<B: BlockT, S: NetworkSpecialization<B>> {
 /// You are encouraged to poll this in a separate background thread or task.
 #[must_use = "The NetworkWorker must be polled in order for the network to work"]
 pub struct NetworkWorker<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> {
+	/// Updated by the `NetworkWorker` and loaded by the `NetworkService`.
+	external_addresses: Arc<Mutex<Vec<Multiaddr>>>,
 	/// Updated by the `NetworkWorker` and loaded by the `NetworkService`.
 	num_connected: Arc<AtomicUsize>,
 	/// Updated by the `NetworkWorker` and loaded by the `NetworkService`.
@@ -621,6 +661,10 @@ impl<B: BlockT + 'static, S: NetworkSpecialization<B>, H: ExHashT> Future for Ne
 
 		// Update the variables shared with the `NetworkService`.
 		self.num_connected.store(self.network_service.user_protocol_mut().num_connected_peers(), Ordering::Relaxed);
+		{
+			let external_addresses = Swarm::<B, S, H>::external_addresses(&self.network_service).cloned().collect();
+			*self.external_addresses.lock() = external_addresses;
+		}
 		self.is_major_syncing.store(match self.network_service.user_protocol_mut().sync_state() {
 			SyncState::Idle => false,
 			SyncState::Downloading => true,

substrate/core/offchain/Cargo.toml

@@ -16,6 +16,7 @@ parking_lot = "0.8.0"
 primitives = { package = "substrate-primitives", path = "../../core/primitives" }
 runtime_primitives = { package = "sr-primitives", path = "../../core/sr-primitives" }
 transaction_pool = { package = "substrate-transaction-pool", path = "../../core/transaction-pool" }
+network = { package = "substrate-network", path = "../../core/network" }
 
 [dev-dependencies]
 env_logger = "0.6"

substrate/core/offchain/src/api.rs

@@ -14,7 +14,7 @@
 // You should have received a copy of the GNU General Public License
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
-use std::sync::Arc;
+use std::{str::FromStr, sync::Arc, convert::TryFrom};
 use client::backend::OffchainStorage;
 use crate::AuthorityKeyProvider;
 use futures::{Stream, Future, sync::mpsc};
@@ -25,6 +25,7 @@ use primitives::offchain::{
 	Externalities as OffchainExt,
 	CryptoKind, CryptoKeyId,
 	StorageKind,
+	OpaqueNetworkState, OpaquePeerId, OpaqueMultiaddr,
 };
 use primitives::crypto::{Pair, Protected};
 use primitives::{ed25519, sr25519};
@@ -33,6 +34,8 @@ use runtime_primitives::{
 	traits::{self, Extrinsic},
 };
 use transaction_pool::txpool::{Pool, ChainApi};
+use network::NetworkStateInfo;
+use network::{PeerId, Multiaddr};
 
 /// A message between the offchain extension and the processing thread.
 enum ExtMessage {
@@ -59,6 +62,7 @@ pub(crate) struct Api<Storage, KeyProvider> {
 	db: Storage,
 	keys_password: Protected<String>,
 	key_provider: KeyProvider,
+	network_state: Arc<dyn NetworkStateInfo + Send + Sync>,
 }
 
 fn unavailable_yet<R: Default>(name: &str) -> R {
@@ -158,6 +162,26 @@ impl<Storage, KeyProvider> OffchainExt for Api<Storage, KeyProvider> where
 		Ok(CryptoKeyId(id))
 	}
 
+	fn authority_pubkey(&self, kind: CryptoKind) -> Result<Vec<u8>, ()> {
+		let key = self.read_key(None, kind)?;
+		let public = match key {
+			Key::Sr25519(pair) => pair.public().encode(),
+			Key::Ed25519(pair) => pair.public().encode(),
+		};
+
+		Ok(public)
+	}
+
+	fn network_state(&self) -> Result<OpaqueNetworkState, ()> {
+		let external_addresses = self.network_state.external_addresses();
+
+		let state = NetworkState::new(
+			self.network_state.peer_id(),
+			external_addresses,
+		);
+		Ok(OpaqueNetworkState::from(state))
+	}
+
 	fn encrypt(&mut self, _key: Option<CryptoKeyId>, _kind: CryptoKind, _data: &[u8]) -> Result<Vec<u8>, ()> {
 		unavailable_yet::<()>("encrypt");
 		Err(())
@@ -285,6 +309,71 @@ impl<Storage, KeyProvider> OffchainExt for Api<Storage, KeyProvider> where
 	}
 }
 
+/// Information about the local node's network state.
+#[derive(Clone, Eq, PartialEq, Debug)]
+pub struct NetworkState {
+	peer_id: PeerId,
+	external_addresses: Vec<Multiaddr>,
+}
+
+impl NetworkState {
+	fn new(peer_id: PeerId, external_addresses: Vec<Multiaddr>) -> Self {
+		NetworkState {
+			peer_id,
+			external_addresses,
+		}
+	}
+}
+
+impl From<NetworkState> for OpaqueNetworkState {
+	fn from(state: NetworkState) -> OpaqueNetworkState {
+		let enc = Encode::encode(&state.peer_id.into_bytes());
+		let peer_id = OpaquePeerId::new(enc);
+
+		let external_addresses: Vec<OpaqueMultiaddr> = state
+			.external_addresses
+			.iter()
+			.map(|multiaddr| {
+				let e = Encode::encode(&multiaddr.to_string());
+				OpaqueMultiaddr::new(e)
+			})
+			.collect();
+
+		OpaqueNetworkState {
+			peer_id,
+			external_addresses,
+		}
+	}
+}
+
+impl TryFrom<OpaqueNetworkState> for NetworkState {
+	type Error = ();
+
+	fn try_from(state: OpaqueNetworkState) -> Result<Self, Self::Error> {
+		let inner_vec = state.peer_id.0;
+
+		let bytes: Vec<u8> = Decode::decode(&mut &inner_vec[..]).ok_or(())?;
+		let peer_id = PeerId::from_bytes(bytes).map_err(|_| ())?;
+
+		let external_addresses: Result<Vec<Multiaddr>, Self::Error> = state.external_addresses
+			.iter()
+			.map(|enc_multiaddr| -> Result<Multiaddr, Self::Error> {
+				let inner_vec = &enc_multiaddr.0;
+				let bytes = <Vec<u8>>::decode(&mut &inner_vec[..]).ok_or(())?;
+				let multiaddr_str = String::from_utf8(bytes).map_err(|_| ())?;
+				let multiaddr = Multiaddr::from_str(&multiaddr_str).map_err(|_| ())?;
+				Ok(multiaddr)
+			})
+			.collect();
+		let external_addresses = external_addresses?;
+
+		Ok(NetworkState {
+			peer_id,
+			external_addresses,
+		})
+	}
+}
+
 /// Offchain extensions implementation API
 ///
 /// This is the asynchronous processing part of the API.
@@ -302,6 +391,7 @@ impl<A: ChainApi> AsyncApi<A> {
 		keys_password: Protected<String>,
 		key_provider: P,
 		at: BlockId<A::Block>,
+		network_state: Arc<dyn NetworkStateInfo + Send + Sync>,
 	) -> (Api<S, P>, AsyncApi<A>) {
 		let (sender, rx) = mpsc::unbounded();
 
@@ -310,6 +400,7 @@ impl<A: ChainApi> AsyncApi<A> {
 			db,
 			keys_password,
 			key_provider,
+			network_state,
 		};
 
 		let async_api = AsyncApi {
@@ -355,8 +446,22 @@ impl<A: ChainApi> AsyncApi<A> {
 #[cfg(test)]
 mod tests {
 	use super::*;
+	use std::{collections::HashSet, convert::TryFrom};
 	use client_db::offchain::LocalStorage;
 	use crate::tests::TestProvider;
+	use network::PeerId;
+
+	struct MockNetworkStateInfo();
+
+	impl NetworkStateInfo for MockNetworkStateInfo {
+		fn external_addresses(&self) -> Vec<Multiaddr> {
+			Vec::new()
+		}
+
+		fn peer_id(&self) -> PeerId {
+			PeerId::random()
+		}
+	}
 
 	fn offchain_api() -> (Api<LocalStorage, TestProvider>, AsyncApi<impl ChainApi>) {
 		let _ = env_logger::try_init();
@@ -366,7 +471,8 @@ mod tests {
 			Pool::new(Default::default(), transaction_pool::ChainApi::new(client.clone()))
 		);
 
-		AsyncApi::new(pool, db, "pass".to_owned().into(), TestProvider::default(), BlockId::Number(0))
+		let mock = Arc::new(MockNetworkStateInfo());
+		AsyncApi::new(pool, db, "pass".to_owned().into(), TestProvider::default(), BlockId::Number(0), mock)
 	}
 
 	#[test]
@@ -455,4 +561,23 @@ mod tests {
 			"Invalid kind should trigger a missing key error."
 		);
 	}
+
+	#[test]
+	fn should_convert_network_states() {
+		// given
+		let state = NetworkState::new(
+			PeerId::random(),
+			vec![
+				Multiaddr::try_from("/ip4/127.0.0.1/tcp/1234".to_string()).unwrap(),
+				Multiaddr::try_from("/ip6/2601:9:4f81:9700:803e:ca65:66e8:c21").unwrap(),
+			],
+		);
+
+		// when
+		let opaque_state = OpaqueNetworkState::from(state.clone());
+		let converted_back_state = NetworkState::try_from(opaque_state).unwrap();
+
+		// then
+		assert_eq!(state, converted_back_state);
+	}
 }

substrate/core/offchain/src/lib.rs

@@ -51,6 +51,7 @@ use runtime_primitives::{
 };
 use futures::future::Future;
 use transaction_pool::txpool::{Pool, ChainApi};
+use network::NetworkStateInfo;
 
 mod api;
 
@@ -130,6 +131,7 @@ impl<Client, Storage, KeyProvider, Block> OffchainWorkers<
 		&self,
 		number: &<Block::Header as traits::Header>::Number,
 		pool: &Arc<Pool<A>>,
+		network_state: Arc<dyn NetworkStateInfo + Send + Sync>,
 	) -> impl Future<Item = (), Error = ()> where
 		A: ChainApi<Block=Block> + 'static,
 	{
@@ -145,6 +147,7 @@ impl<Client, Storage, KeyProvider, Block> OffchainWorkers<
 				self.keys_password.clone(),
 				self.authority_key.clone(),
 				at.clone(),
+				network_state.clone(),
 			);
 			debug!("Running offchain workers at {:?}", at);
 			let api = Box::new(api);
@@ -161,6 +164,20 @@ mod tests {
 	use super::*;
 	use futures::Future;
 	use primitives::{ed25519, sr25519, crypto::{TypedKey, Pair}};
+	use std::collections::HashSet;
+	use network::{Multiaddr, PeerId};
+
+	struct MockNetworkStateInfo();
+
+	impl NetworkStateInfo for MockNetworkStateInfo {
+		fn external_addresses(&self) -> Vec<Multiaddr> {
+			Vec::new()
+		}
+
+		fn peer_id(&self) -> PeerId {
+			PeerId::random()
+		}
+	}
 
 	#[derive(Clone, Default)]
 	pub(crate) struct TestProvider {
@@ -186,10 +203,11 @@ mod tests {
 		let client = Arc::new(test_client::new());
 		let pool = Arc::new(Pool::new(Default::default(), ::transaction_pool::ChainApi::new(client.clone())));
 		let db = client_db::offchain::LocalStorage::new_test();
+		let mock = Arc::new(MockNetworkStateInfo());
 
 		// when
 		let offchain = OffchainWorkers::new(client, db, TestProvider::default(), "".to_owned().into());
-		runtime.executor().spawn(offchain.on_block_imported(&0u64, &pool));
+		runtime.executor().spawn(offchain.on_block_imported(&0u64, &pool, mock.clone()));
 
 		// then
 		runtime.shutdown_on_idle().wait().unwrap();

substrate/core/offchain/src/testing.rs

@@ -31,6 +31,7 @@ use primitives::offchain::{
 	CryptoKind,
 	CryptoKeyId,
 	StorageKind,
+	OpaqueNetworkState,
 };
 
 /// Pending request.
@@ -139,6 +140,14 @@ impl offchain::Externalities for TestOffchainExt {
 		unimplemented!("not needed in tests so far")
 	}
 
+	fn network_state(&self) -> Result<OpaqueNetworkState, ()> {
+		unimplemented!("not needed in tests so far")
+	}
+
+	fn authority_pubkey(&self, _kind: CryptoKind) -> Result<Vec<u8>, ()> {
+		unimplemented!("not needed in tests so far")
+	}
+
 	fn new_crypto_key(&mut self, _crypto: CryptoKind) -> Result<CryptoKeyId, ()> {
 		unimplemented!("not needed in tests so far")
 	}

substrate/core/primitives/src/offchain.rs

@@ -185,6 +185,41 @@ impl TryFrom<u32> for HttpRequestStatus {
 	}
 }
 
+/// A blob to hold information about the local node's network state
+/// without committing to its format.
+#[derive(Clone, Eq, PartialEq, Encode, Decode)]
+#[cfg_attr(feature = "std", derive(Debug))]
+pub struct OpaqueNetworkState {
+	/// PeerId of the local node.
+	pub peer_id: OpaquePeerId,
+	/// List of addresses the node knows it can be reached as.
+	pub external_addresses: Vec<OpaqueMultiaddr>,
+}
+
+/// Simple blob to hold a `PeerId` without committing to its format.
+#[derive(Clone, Eq, PartialEq, Encode, Decode)]
+#[cfg_attr(feature = "std", derive(Debug))]
+pub struct OpaquePeerId(pub Vec<u8>);
+
+impl OpaquePeerId {
+	/// Create new `OpaquePeerId`
+	pub fn new(vec: Vec<u8>) -> Self {
+		OpaquePeerId(vec)
+	}
+}
+
+/// Simple blob to hold a `Multiaddr` without committing to its format.
+#[derive(Clone, Eq, PartialEq, Encode, Decode)]
+#[cfg_attr(feature = "std", derive(Debug))]
+pub struct OpaqueMultiaddr(pub Vec<u8>);
+
+impl OpaqueMultiaddr {
+	/// Create new `OpaqueMultiaddr`
+	pub fn new(vec: Vec<u8>) -> Self {
+		OpaqueMultiaddr(vec)
+	}
+}
+
 /// Opaque timestamp type
 #[derive(Clone, Copy, PartialEq, Eq, Ord, PartialOrd, Default)]
 #[cfg_attr(feature = "std", derive(Debug))]
@@ -241,6 +276,12 @@ pub trait Externalities {
 	/// The transaction will end up in the pool and be propagated to others.
 	fn submit_transaction(&mut self, extrinsic: Vec<u8>) -> Result<(), ()>;
 
+	/// Returns information about the local node's network state.
+	fn network_state(&self) -> Result<OpaqueNetworkState, ()>;
+
+	/// Returns the locally configured authority public key, if available.
+	fn authority_pubkey(&self, crypto: CryptoKind) -> Result<Vec<u8>, ()>;
+
 	/// Create new key(pair) for signing/encryption/decryption.
 	///
 	/// Returns an error if given crypto kind is not supported.
@@ -319,7 +360,7 @@ pub trait Externalities {
 	/// offchain worker tasks running on the same machine. It IS persisted between runs.
 	fn local_storage_get(&mut self, kind: StorageKind, key: &[u8]) -> Option<Vec<u8>>;
 
-	/// Initiaties a http request given HTTP verb and the URL.
+	/// Initiates a http request given HTTP verb and the URL.
 	///
 	/// Meta is a future-reserved field containing additional, parity-codec encoded parameters.
 	/// Returns the id of newly started request.
@@ -398,6 +439,14 @@ impl<T: Externalities + ?Sized> Externalities for Box<T> {
 		(&mut **self).encrypt(key, kind, data)
 	}
 
+	fn network_state(&self) -> Result<OpaqueNetworkState, ()> {
+		(& **self).network_state()
+	}
+
+	fn authority_pubkey(&self, key:CryptoKind) -> Result<Vec<u8>, ()> {
+		(&**self).authority_pubkey(key)
+	}
+
 	fn decrypt(&mut self, key: Option<CryptoKeyId>, kind: CryptoKind, data: &[u8]) -> Result<Vec<u8>, ()> {
 		(&mut **self).decrypt(key, kind, data)
 	}

substrate/core/service/Cargo.toml

@@ -33,6 +33,7 @@ transaction_pool = { package = "substrate-transaction-pool", path = "../../core/
 rpc = { package = "substrate-rpc-servers", path = "../../core/rpc-servers" }
 tel = { package = "substrate-telemetry", path = "../../core/telemetry" }
 offchain = { package = "substrate-offchain", path = "../../core/offchain" }
+parity-multiaddr = { package = "parity-multiaddr", version = "0.5.0" }
 
 [dev-dependencies]
 substrate-test-runtime-client = { path = "../test-runtime/client" }

substrate/core/service/src/components.rs

@@ -23,7 +23,7 @@ use client_db;
 use client::{self, Client, runtime_api};
 use crate::{error, Service, AuthorityKeyProvider};
 use consensus_common::{import_queue::ImportQueue, SelectChain};
-use network::{self, OnDemand, FinalityProofProvider, config::BoxFinalityProofRequestBuilder};
+use network::{self, OnDemand, FinalityProofProvider, NetworkStateInfo, config::BoxFinalityProofRequestBuilder};
 use substrate_executor::{NativeExecutor, NativeExecutionDispatch};
 use transaction_pool::txpool::{self, Options as TransactionPoolOptions, Pool as TransactionPool};
 use runtime_primitives::{
@@ -235,6 +235,7 @@ pub trait OffchainWorker<C: Components> {
 			ComponentBlock<C>
 		>,
 		pool: &Arc<TransactionPool<C::TransactionPoolApi>>,
+		network_state: &Arc<dyn NetworkStateInfo + Send + Sync>,
 	) -> error::Result<Box<dyn Future<Item = (), Error = ()> + Send>>;
 }
 
@@ -251,8 +252,9 @@ impl<C: Components> OffchainWorker<Self> for C where
 			ComponentBlock<C>
 		>,
 		pool: &Arc<TransactionPool<C::TransactionPoolApi>>,
+		network_state: &Arc<dyn NetworkStateInfo + Send + Sync>,
 	) -> error::Result<Box<dyn Future<Item = (), Error = ()> + Send>> {
-		Ok(Box::new(offchain.on_block_imported(number, pool)))
+		Ok(Box::new(offchain.on_block_imported(number, pool, network_state.clone())))
 	}
 }
 

substrate/core/service/src/lib.rs

@@ -37,7 +37,7 @@ use exit_future::Signal;
 use futures::prelude::*;
 use futures03::stream::{StreamExt as _, TryStreamExt as _};
 use keystore::Store as Keystore;
-use network::NetworkState;
+use network::{NetworkState, NetworkStateInfo};
 use log::{info, warn, debug, error};
 use parity_codec::{Encode, Decode};
 use primitives::{Pair, ed25519, crypto};
@@ -293,6 +293,7 @@ impl<Components: components::Components> Service<Components> {
 			let wclient = Arc::downgrade(&client);
 			let offchain = offchain_workers.as_ref().map(Arc::downgrade);
 			let to_spawn_tx_ = to_spawn_tx.clone();
+			let network_state_info: Arc<dyn NetworkStateInfo + Send + Sync> = network.clone();
 
 			let events = client.import_notification_stream()
 				.map(|v| Ok::<_, ()>(v)).compat()
@@ -312,6 +313,7 @@ impl<Components: components::Components> Service<Components> {
 							&number,
 							&offchain,
 							&txpool,
+							&network_state_info,
 						).map_err(|e| warn!("Offchain workers error processing new block: {:?}", e))?;
 						let _ = to_spawn_tx_.unbounded_send(future);
 					}

substrate/core/sr-io/src/lib.rs

@@ -38,6 +38,7 @@ use primitives::offchain::{
 	HttpRequestId, HttpRequestStatus, HttpError,
 	CryptoKind, CryptoKeyId,
 	StorageKind,
+	OpaqueNetworkState,
 };
 
 /// Error verifying ECDSA signature
@@ -239,6 +240,13 @@ export_api! {
 		/// The transaction will end up in the pool.
 		fn submit_transaction<T: codec::Encode>(data: &T) -> Result<(), ()>;
 
+		/// Returns information about the local node's network state.
+		fn network_state() -> Result<OpaqueNetworkState, ()>;
+
+		/// Returns the currently configured authority public key, if available.
+		// TODO [#3139] change into crypto_pubkey(&self, key: Option<CryptoKeyId>, kind: CryptoKind)
+		fn authority_pubkey(crypto: CryptoKind) -> Result<Vec<u8>, ()>;
+
 		/// Create new key(pair) for signing/encryption/decryption.
 		///
 		/// Returns an error if given crypto kind is not supported.
@@ -313,7 +321,7 @@ export_api! {
 		/// offchain worker tasks running on the same machine. It IS persisted between runs.
 		fn local_storage_get(kind: StorageKind, key: &[u8]) -> Option<Vec<u8>>;
 
-		/// Initiaties a http request given HTTP verb and the URL.
+		/// Initiates a http request given HTTP verb and the URL.
 		///
 		/// Meta is a future-reserved field containing additional, parity-codec encoded parameters.
 		/// Returns the id of newly started request.

substrate/core/sr-io/with_std.rs

@@ -269,6 +269,18 @@ impl OffchainApi for () {
 		}, "submit_transaction can be called only in the offchain worker context")
 	}
 
+	fn network_state() -> Result<OpaqueNetworkState, ()> {
+		with_offchain(|ext| {
+			ext.network_state()
+		}, "network_state can be called only in the offchain worker context")
+	}
+
+	fn authority_pubkey(crypto: offchain::CryptoKind) -> Result<Vec<u8>, ()> {
+		with_offchain(|ext| {
+			ext.authority_pubkey(crypto)
+		}, "authority_pubkey can be called only in the offchain worker context")
+	}
+
 	fn new_crypto_key(crypto: offchain::CryptoKind) -> Result<offchain::CryptoKeyId, ()> {
 		with_offchain(|ext| {
 			ext.new_crypto_key(crypto)

substrate/core/sr-io/without_std.rs

@@ -385,6 +385,33 @@ pub mod ext {
 		/// - nonzero otherwise.
 		fn ext_submit_transaction(data: *const u8, len: u32) -> u32;
 
+		/// Returns information about the local node's network state.
+		///
+		/// # Returns
+		///
+		/// The encoded `Result<offchain::OpaqueNetworkState, ()>`.
+		/// `written_out` contains the length of the message.
+		///
+		/// The ownership of the returned buffer is transferred to the runtime
+		/// code and the runtime is responsible for freeing it. This is always
+		/// a properly allocated pointer (which cannot be NULL), hence the
+		/// runtime code can always rely on it.
+		fn ext_network_state(written_out: *mut u32) -> *mut u8;
+
+		/// Returns the locally configured authority public key, if available.
+		/// The `crypto` argument is `offchain::CryptoKind` converted to `u32`.
+		///
+		/// # Returns
+		///
+		/// The encoded `Result<PublicKey encoded to Vec<u8>, ()>`.
+		/// `written_out` contains the length of the message.
+		///
+		/// The ownership of the returned buffer is transferred to the runtime
+		/// code and the runtime is responsible for freeing it. This is always
+		/// a properly allocated pointer (which cannot be NULL), hence the
+		/// runtime code can always rely on it.
+		fn ext_authority_pubkey(crypto: u32, written_out: *mut u32) -> *mut u8;
+
 		/// Create new key(pair) for signing/encryption/decryption.
 		///
 		/// # Returns
@@ -504,7 +531,7 @@ pub mod ext {
 		/// - Otherwise, pointer to the value in memory. `value_len` contains the length of the value.
 		fn ext_local_storage_get(kind: u32, key: *const u8, key_len: u32, value_len: *mut u32) -> *mut u8;
 
-		/// Initiaties a http request.
+		/// Initiates a http request.
 		///
 		/// `meta` is parity-codec encoded additional parameters to the request (like redirection policy,
 		/// timeouts, certificates policy, etc). The format is not yet specified and the field is currently
@@ -888,6 +915,39 @@ impl OffchainApi for () {
 		}
 	}
 
+	fn network_state() -> Result<offchain::OpaqueNetworkState, ()> {
+		let mut len = 0_u32;
+		let raw_result = unsafe {
+			let ptr = ext_network_state.get()(&mut len);
+
+			from_raw_parts(ptr, len)
+		};
+
+		match raw_result {
+			Some(raw_result) => codec::Decode::decode(&mut &*raw_result).unwrap_or(Err(())),
+			None => Err(())
+		}
+	}
+
+	fn authority_pubkey(kind: offchain::CryptoKind) -> Result<Vec<u8>, ()> {
+		let kind = kind as isize as u32;
+
+		let mut len = 0u32;
+		let raw_result = unsafe {
+			let ptr = ext_authority_pubkey.get()(
+				kind,
+				&mut len,
+			);
+
+			from_raw_parts(ptr, len)
+		};
+
+		match raw_result {
+			Some(raw_result) => codec::Decode::decode(&mut &*raw_result).unwrap_or(Err(())),
+			None => Err(())
+		}
+	}
+
 	fn new_crypto_key(crypto: offchain::CryptoKind) -> Result<offchain::CryptoKeyId, ()> {
 		let crypto = crypto.into();
 		let ret = unsafe {

substrate/core/sr-primitives/src/generic/unchecked_extrinsic.rs

@@ -114,9 +114,15 @@ impl<
 	Signature: Codec,
 	Call,
 > Extrinsic for UncheckedExtrinsic<Address, Index, Call, Signature> {
+	type Call = Call;
+
 	fn is_signed(&self) -> Option<bool> {
 		Some(self.signature.is_some())
 	}
+
+	fn new_unsigned(call: Self::Call) -> Option<Self> {
+		Some(UncheckedExtrinsic::new_unsigned(call))
+	}
 }
 
 impl<Address: Codec, Index: HasCompact + Codec, Signature: Codec, Call: Decode> Decode

substrate/core/sr-primitives/src/generic/unchecked_mortal_compact_extrinsic.rs

@@ -59,9 +59,15 @@ impl<Address, Index, Call, Signature> UncheckedMortalCompactExtrinsic<Address, I
 }
 
 impl<Address: Encode, Index: Encode, Call: Encode, Signature: Encode> Extrinsic for UncheckedMortalCompactExtrinsic<Address, Index, Call, Signature> {
+	type Call = Call;
+
 	fn is_signed(&self) -> Option<bool> {
 		Some(self.signature.is_some())
 	}
+
+	fn new_unsigned(call: Self::Call) -> Option<Self> {
+		Some(UncheckedMortalCompactExtrinsic::new_unsigned(call))
+	}
 }
 
 impl<Address, AccountId, Index, Call, Signature, Context, Hash, BlockNumber> Checkable<Context>

substrate/core/sr-primitives/src/generic/unchecked_mortal_extrinsic.rs

@@ -61,9 +61,15 @@ impl<Address, Index, Call, Signature> UncheckedMortalExtrinsic<Address, Index, C
 }
 
 impl<Address: Encode, Index: Encode, Call: Encode, Signature: Encode> Extrinsic for UncheckedMortalExtrinsic<Address, Index, Call, Signature> {
+	type Call = Call;
+
 	fn is_signed(&self) -> Option<bool> {
 		Some(self.signature.is_some())
 	}
+
+	fn new_unsigned(call: Self::Call) -> Option<Self> {
+		Some(UncheckedMortalExtrinsic::new_unsigned(call))
+	}
 }
 
 impl<Address, AccountId, Index, Call, Signature, Context, Hash, BlockNumber> Checkable<Context>

substrate/core/sr-primitives/src/lib.rs

@@ -869,9 +869,13 @@ impl ::serde::Serialize for OpaqueExtrinsic {
 }
 
 impl traits::Extrinsic for OpaqueExtrinsic {
+	type Call = ();
+
 	fn is_signed(&self) -> Option<bool> {
 		None
 	}
+
+	fn new_unsigned(_call: Self::Call) -> Option<Self> { None }
 }
 
 #[cfg(test)]

substrate/core/sr-primitives/src/testing.rs

@@ -44,6 +44,14 @@ impl TypedKey for UintAuthorityId {
 	const KEY_TYPE: KeyTypeId = UINT_DUMMY_KEY;
 }
 
+impl AsRef<[u8]> for UintAuthorityId {
+	fn as_ref(&self) -> &[u8] {
+		let ptr = self.0 as *const _;
+		// It's safe to do this here since `UintAuthorityId` is `u64`.
+		unsafe { std::slice::from_raw_parts(ptr, 8) }
+	}
+}
+
 impl OpaqueKeys for UintAuthorityId {
 	type KeyTypeIds = std::iter::Cloned<std::slice::Iter<'static, KeyTypeId>>;
 
@@ -133,6 +141,8 @@ impl<'a> Deserialize<'a> for Header {
 pub struct ExtrinsicWrapper<Xt>(Xt);
 
 impl<Xt> traits::Extrinsic for ExtrinsicWrapper<Xt> {
+	type Call = ();
+
 	fn is_signed(&self) -> Option<bool> {
 		None
 	}
@@ -219,6 +229,8 @@ impl<Call: Codec + Sync + Send, Context> Checkable<Context> for TestXt<Call> {
 	fn check(self, _: &Context) -> Result<Self::Checked, &'static str> { Ok(self) }
 }
 impl<Call: Codec + Sync + Send> traits::Extrinsic for TestXt<Call> {
+	type Call = Call;
+
 	fn is_signed(&self) -> Option<bool> {
 		Some(self.0.is_some())
 	}

substrate/core/sr-primitives/src/traits.rs

@@ -622,6 +622,12 @@ pub trait RandomnessBeacon {
 pub trait Member: Send + Sync + Sized + MaybeDebug + Eq + PartialEq + Clone + 'static {}
 impl<T: Send + Sync + Sized + MaybeDebug + Eq + PartialEq + Clone + 'static> Member for T {}
 
+/// Determine if a `MemberId` is a valid member.
+pub trait IsMember<MemberId> {
+	/// Is the given `MemberId` a valid member?
+	fn is_member(member_id: &MemberId) -> bool;
+}
+
 /// Something which fulfills the abstract idea of a Substrate header. It has types for a `Number`,
 /// a `Hash` and a `Digest`. It provides access to an `extrinsics_root`, `state_root` and
 /// `parent_hash`, as well as a `digest` and a block `number`.
@@ -702,10 +708,16 @@ pub trait Block: Clone + Send + Sync + Codec + Eq + MaybeSerializeDebugButNotDes
 }
 
 /// Something that acts like an `Extrinsic`.
-pub trait Extrinsic {
+pub trait Extrinsic: Sized {
+	/// The function call.
+	type Call;
+
 	/// Is this `Extrinsic` signed?
 	/// If no information are available about signed/unsigned, `None` should be returned.
 	fn is_signed(&self) -> Option<bool> { None }
+
+	/// New instance of an unsigned extrinsic aka "inherent".
+	fn new_unsigned(_call: Self::Call) -> Option<Self> { None }
 }
 
 /// Extract the hashing type for a block.

substrate/core/state-machine/src/ext.rs

@@ -81,7 +81,7 @@ where
 	changes_trie_transaction: Option<(MemoryDB<H>, H::Out)>,
 	/// Additional externalities for offchain workers.
 	///
-	/// If None, some methods from the trait might not supported.
+	/// If None, some methods from the trait might not be supported.
 	offchain_externalities: Option<&'a mut O>,
 	/// Dummy usage of N arg.
 	_phantom: ::std::marker::PhantomData<N>,

substrate/core/state-machine/src/lib.rs

@@ -24,7 +24,7 @@ use log::warn;
 use hash_db::Hasher;
 use parity_codec::{Decode, Encode};
 use primitives::{
-	storage::well_known_keys, NativeOrEncoded, NeverNativeValue, offchain
+	storage::well_known_keys, NativeOrEncoded, NeverNativeValue, offchain,
 };
 
 pub mod backend;
@@ -240,6 +240,19 @@ impl offchain::Externalities for NeverOffchainExt {
 		unreachable!()
 	}
 
+	fn network_state(
+		&self,
+	) -> Result<offchain::OpaqueNetworkState, ()> {
+		unreachable!()
+	}
+
+	fn authority_pubkey(
+		&self,
+		_crypto: offchain::CryptoKind,
+	) -> Result<Vec<u8>, ()> {
+		unreachable!()
+	}
+
 	fn new_crypto_key(
 		&mut self,
 		_crypto: offchain::CryptoKind,

substrate/core/test-runtime/src/lib.rs

@@ -140,6 +140,8 @@ impl BlindCheckable for Extrinsic {
 }
 
 impl ExtrinsicT for Extrinsic {
+	type Call = ();
+
 	fn is_signed(&self) -> Option<bool> {
 		if let Extrinsic::IncludeData(_) = *self {
 			Some(false)
@@ -147,6 +149,10 @@ impl ExtrinsicT for Extrinsic {
 			Some(true)
 		}
 	}
+
+	fn new_unsigned(_call: Self::Call) -> Option<Self> {
+		None
+	}
 }
 
 impl Extrinsic {

substrate/node-template/runtime/src/lib.rs

@@ -80,9 +80,13 @@ pub mod opaque {
 		}
 	}
 	impl traits::Extrinsic for UncheckedExtrinsic {
+		type Call = ();
 		fn is_signed(&self) -> Option<bool> {
 			None
 		}
+		fn new_unsigned(_call: Self::Call) -> Option<Self> {
+			None
+		}
 	}
 	/// Opaque block header type.
 	pub type Header = generic::Header<BlockNumber, BlakeTwo256>;

substrate/node/cli/src/chain_spec.rs

@@ -19,10 +19,10 @@
 use primitives::{ed25519, sr25519, Pair, crypto::UncheckedInto};
 use node_primitives::{AccountId, AuraId, Balance};
 use node_runtime::{
-	GrandpaConfig, BalancesConfig, ContractsConfig, ElectionsConfig, DemocracyConfig, CouncilConfig,
-	AuraConfig, IndicesConfig, SessionConfig, StakingConfig, SudoConfig, TechnicalCommitteeConfig,
-	SystemConfig, WASM_BINARY, Perbill, SessionKeys, StakerStatus, DAYS, DOLLARS,
-	MILLICENTS,
+	GrandpaConfig, BalancesConfig, ContractsConfig, ElectionsConfig, DemocracyConfig,
+	CouncilConfig, AuraConfig,  ImOnlineConfig, IndicesConfig, SessionConfig, StakingConfig,
+	SudoConfig,	TechnicalCommitteeConfig, SystemConfig, WASM_BINARY, Perbill, SessionKeys,
+	StakerStatus, DAYS, DOLLARS, MILLICENTS,
 };
 pub use node_runtime::GenesisConfig;
 use substrate_service;
@@ -154,6 +154,10 @@ fn staging_testnet_config_genesis() -> GenesisConfig {
 		aura: Some(AuraConfig {
 			authorities: initial_authorities.iter().map(|x| x.2.clone()).collect(),
 		}),
+		im_online: Some(ImOnlineConfig {
+			gossip_at: 0,
+			last_new_era_start: 0,
+		}),
 		grandpa: Some(GrandpaConfig {
 			authorities: initial_authorities.iter().map(|x| (x.3.clone(), 1)).collect(),
 		}),
@@ -291,6 +295,10 @@ pub fn testnet_genesis(
 		aura: Some(AuraConfig {
 			authorities: initial_authorities.iter().map(|x| x.2.clone()).collect(),
 		}),
+		im_online: Some(ImOnlineConfig{
+			gossip_at: 0,
+			last_new_era_start: 0,
+		}),
 		grandpa: Some(GrandpaConfig {
 			authorities: initial_authorities.iter().map(|x| (x.3.clone(), 1)).collect(),
 		}),

substrate/node/executor/src/lib.rs

@@ -354,6 +354,7 @@ mod tests {
 				gas_price: 1 * MILLICENTS,
 			}),
 			sudo: Some(Default::default()),
+			im_online: Some(Default::default()),
 			grandpa: Some(GrandpaConfig {
 				authorities: vec![],
 			}),

substrate/node/runtime/Cargo.toml

@@ -33,6 +33,7 @@ system = { package = "srml-system", path = "../../srml/system", default-features
 timestamp = { package = "srml-timestamp", path = "../../srml/timestamp", default-features = false }
 treasury = { package = "srml-treasury", path = "../../srml/treasury", default-features = false }
 sudo = { package = "srml-sudo", path = "../../srml/sudo", default-features = false }
+im-online = { package = "srml-im-online", path = "../../srml/im-online", default-features = false }
 node-primitives = { path = "../primitives", default-features = false }
 consensus_aura = { package = "substrate-consensus-aura-primitives", path = "../../core/consensus/aura/primitives", default-features = false }
 rustc-hex = { version = "2.0", optional = true }
@@ -79,4 +80,5 @@ std = [
 	"rustc-hex",
 	"substrate-keyring",
 	"offchain-primitives/std",
+	"im-online/std",
 ]

substrate/node/runtime/src/lib.rs

@@ -74,8 +74,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to equal spec_version. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 114,
-	impl_version: 114,
+	spec_version: 115,
+	impl_version: 115,
 	apis: RUNTIME_API_VERSIONS,
 };
 
@@ -193,7 +193,7 @@ parameter_types! {
 	pub const Offset: BlockNumber = 0;
 }
 
-type SessionHandlers = (Grandpa, Aura);
+type SessionHandlers = (Grandpa, Aura, ImOnline);
 
 impl_opaque_keys! {
 	pub struct SessionKeys {
@@ -371,6 +371,15 @@ impl sudo::Trait for Runtime {
 	type Proposal = Call;
 }
 
+impl im_online::Trait for Runtime {
+	type AuthorityId = AuraId;
+	type Call = Call;
+	type Event = Event;
+	type SessionsPerEra = SessionsPerEra;
+	type UncheckedExtrinsic = UncheckedExtrinsic;
+	type IsValidAuthorityId = Aura;
+}
+
 impl grandpa::Trait for Runtime {
 	type Event = Event;
 }
@@ -409,6 +418,7 @@ construct_runtime!(
 		Treasury: treasury::{Module, Call, Storage, Event<T>},
 		Contracts: contracts,
 		Sudo: sudo,
+		ImOnline: im_online::{default, ValidateUnsigned},
 	}
 );
 

substrate/srml/aura/src/lib.rs

@@ -54,7 +54,7 @@ use rstd::{result, prelude::*};
 use parity_codec::Encode;
 use srml_support::{decl_storage, decl_module, Parameter, storage::StorageValue, traits::Get};
 use primitives::{
-	traits::{SaturatedConversion, Saturating, Zero, One, Member, TypedKey},
+	traits::{SaturatedConversion, Saturating, Zero, One, Member, IsMember, TypedKey},
 	generic::DigestItem,
 };
 use timestamp::OnTimestampSet;
@@ -210,6 +210,14 @@ impl<T: Trait> session::OneSessionHandler<T::AccountId> for Module<T> {
 	}
 }
 
+impl<T: Trait> IsMember<T::AuthorityId> for Module<T> {
+	fn is_member(authority_id: &T::AuthorityId) -> bool {
+		Self::authorities()
+			.iter()
+			.any(|id| id == authority_id)
+	}
+}
+
 /// A report of skipped authorities in Aura.
 #[derive(Clone, PartialEq, Eq)]
 #[cfg_attr(feature = "std", derive(Debug))]

substrate/srml/babe/src/lib.rs

@@ -23,7 +23,10 @@ pub use timestamp;
 use rstd::{result, prelude::*};
 use srml_support::{decl_storage, decl_module, StorageValue, traits::FindAuthor, traits::Get};
 use timestamp::{OnTimestampSet, Trait};
-use primitives::{generic::DigestItem, traits::{SaturatedConversion, Saturating, RandomnessBeacon}};
+use primitives::{
+	generic::DigestItem,
+	traits::{IsMember, SaturatedConversion, Saturating, RandomnessBeacon}
+};
 use primitives::ConsensusEngineId;
 #[cfg(feature = "std")]
 use timestamp::TimestampInherentData;
@@ -188,6 +191,14 @@ impl<T: Trait> FindAuthor<u64> for Module<T> {
 	}
 }
 
+impl<T: timestamp::Trait> IsMember<AuthorityId> for Module<T> {
+	fn is_member(authority_id: &AuthorityId) -> bool {
+		<Module<T>>::authorities()
+			.iter()
+			.any(|id| id == authority_id)
+	}
+}
+
 impl<T: Trait> Module<T> {
 	/// Determine the BABE slot duration based on the Timestamp module configuration.
 	pub fn slot_duration() -> T::Moment {

substrate/srml/im-online/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+name = "srml-im-online"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2018"
+
+[dependencies]
+parity-codec = { version = "4.1.1", default-features = false, features = ["derive"] }
+primitives = { package = "sr-primitives", path = "../../core/sr-primitives", default-features = false }
+rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
+serde = { version = "1.0", optional = true }
+session = { package = "srml-session", path = "../session", default-features = false }
+srml-support = { path = "../support", default-features = false }
+sr-io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
+substrate_primitives = { package = "substrate-primitives", path = "../../core/primitives", default-features = false }
+system = { package = "srml-system", path = "../system", default-features = false }
+
+[features]
+default = ["std"]
+std = [
+	"parity-codec/std",
+	"primitives/std",
+	"rstd/std",
+	"serde",
+	"session/std",
+	"srml-support/std",
+	"sr-io/std",
+	"system/std",
+]

substrate/srml/im-online/src/lib.rs

@@ -0,0 +1,433 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate 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.
+
+// Substrate 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 Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! # I'm online Module
+//!
+//! If the local node is a validator (i.e. contains an authority key), this module
+//! gossips a heartbeat transaction with each new session. The heartbeat functions
+//! as a simple mechanism to signal that the node is online in the current era.
+//!
+//! Received heartbeats are tracked for one era and reset with each new era. The
+//! module exposes two public functions to query if a heartbeat has been received
+//! in the current era or session.
+//!
+//! The heartbeat is a signed transaction, which was signed using the session key
+//! and includes the recent best block number of the local validators chain as well
+//! as the [NetworkState](../../core/offchain/struct.NetworkState.html).
+//! It is submitted as an Unsigned Transaction via off-chain workers.
+//!
+//! - [`im_online::Trait`](./trait.Trait.html)
+//! - [`Call`](./enum.Call.html)
+//! - [`Module`](./struct.Module.html)
+//!
+//! ## Interface
+//!
+//! ### Public Functions
+//!
+//! - `is_online_in_current_era` - True if the validator sent a heartbeat in the current era.
+//! - `is_online_in_current_session` - True if the validator sent a heartbeat in the current session.
+//!
+//! ## Usage
+//!
+//! ```
+//! use srml_support::{decl_module, dispatch::Result};
+//! use system::ensure_signed;
+//! use srml_im_online::{self as im_online};
+//!
+//! pub trait Trait: im_online::Trait {}
+//!
+//! decl_module! {
+//! 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+//! 		pub fn is_online(origin, authority_id: T::AuthorityId) -> Result {
+//! 			let _sender = ensure_signed(origin)?;
+//! 			let _is_online = <im_online::Module<T>>::is_online_in_current_era(&authority_id);
+//! 			Ok(())
+//! 		}
+//! 	}
+//! }
+//! # fn main() { }
+//! ```
+//!
+//! ## Dependencies
+//!
+//! This module depends on the [Session module](../srml_session/index.html).
+
+// Ensure we're `no_std` when compiling for Wasm.
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use substrate_primitives::{
+	crypto::TypedKey, offchain::CryptoKind,
+	crypto::key_types,
+	offchain::OpaqueNetworkState,
+	offchain::StorageKind,
+	sr25519, ed25519,
+};
+use parity_codec::{Encode, Decode};
+use primitives::{
+	ApplyError, traits::{Member, IsMember, Extrinsic as ExtrinsicT},
+	transaction_validity::{TransactionValidity, TransactionLongevity},
+};
+use rstd::prelude::*;
+use session::SessionIndex;
+use sr_io::Printable;
+use srml_support::{
+	Parameter, StorageValue, decl_module, decl_event, decl_storage,
+	traits::Get, StorageDoubleMap, print,
+};
+use system::ensure_none;
+
+// The local storage database key under which the worker progress status
+// is tracked.
+const DB_KEY: &[u8] = b"srml/im-online-worker-status";
+
+// It's important to persist the worker state, since e.g. the
+// server could be restarted while starting the gossip process, but before
+// finishing it. With every execution of the off-chain worker we check
+// if we need to recover and resume gossipping or if there is already
+// another off-chain worker in the process of gossipping.
+#[derive(Encode, Decode, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "std", derive(Debug))]
+struct WorkerStatus<BlockNumber> {
+	done: bool,
+	gossipping_at: BlockNumber,
+}
+
+// Error which may occur while executing the off-chain code.
+enum OffchainErr {
+	DecodeAuthorityId,
+	DecodeWorkerStatus,
+	ExtrinsicCreation,
+	FailedSigning,
+	NetworkState,
+	SubmitTransaction,
+	UnknownCryptoKind,
+}
+
+impl Printable for OffchainErr {
+	fn print(self) {
+		match self {
+			OffchainErr::DecodeAuthorityId => print("Offchain error: decoding AuthorityId failed!"),
+			OffchainErr::DecodeWorkerStatus => print("Offchain error: decoding WorkerStatus failed!"),
+			OffchainErr::ExtrinsicCreation => print("Offchain error: extrinsic creation failed!"),
+			OffchainErr::FailedSigning => print("Offchain error: signing failed!"),
+			OffchainErr::NetworkState => print("Offchain error: fetching network state failed!"),
+			OffchainErr::SubmitTransaction => print("Offchain error: submitting transaction failed!"),
+			OffchainErr::UnknownCryptoKind => print("Offchain error: the CryptoKind is unknown!"),
+		}
+	}
+}
+
+/// Heartbeat which is send/received.
+#[derive(Encode, Decode, Clone, PartialEq, Eq)]
+#[cfg_attr(feature = "std", derive(Debug))]
+pub struct Heartbeat<BlockNumber, AuthorityId>
+	where BlockNumber: PartialEq + Eq + Decode + Encode,
+{
+	block_number: BlockNumber,
+	network_state: OpaqueNetworkState,
+	session_index: session::SessionIndex,
+	authority_id: AuthorityId,
+}
+
+pub trait Trait: system::Trait + session::Trait {
+	/// The overarching event type.
+	type Event: From<Event<Self>> + Into<<Self as system::Trait>::Event>;
+
+	/// The function call.
+	type Call: From<Call<Self>>;
+
+	/// A extrinsic right from the external world. This is unchecked and so
+	/// can contain a signature.
+	type UncheckedExtrinsic: ExtrinsicT<Call=Self::Call> + Encode + Decode;
+
+	/// The identifier type for an authority.
+	type AuthorityId: Member + Parameter + Default + TypedKey + Decode + Encode + AsRef<[u8]>;
+
+	/// Number of sessions per era.
+	type SessionsPerEra: Get<SessionIndex>;
+
+	/// Determine if an `AuthorityId` is a valid authority.
+	type IsValidAuthorityId: IsMember<Self::AuthorityId>;
+}
+
+decl_event!(
+	pub enum Event<T> where
+		<T as system::Trait>::BlockNumber,
+		<T as Trait>::AuthorityId
+	{
+		/// A new heartbeat was received at this `BlockNumber` from `AuthorityId`
+		HeartbeatReceived(BlockNumber, AuthorityId),
+	}
+);
+
+decl_storage! {
+	trait Store for Module<T: Trait> as ImOnline {
+		// The block number when we should gossip.
+		GossipAt get(gossip_at) config(): T::BlockNumber;
+
+		// The session index when the last new era started.
+		LastNewEraStart get(last_new_era_start) config(): Option<session::SessionIndex>;
+
+		// For each session index we keep a mapping of `AuthorityId` to
+		// `offchain::OpaqueNetworkState`.
+		ReceivedHeartbeats get(received_heartbeats): double_map session::SessionIndex,
+			blake2_256(T::AuthorityId) => Vec<u8>;
+	}
+}
+
+decl_module! {
+	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
+		/// Number of sessions per era.
+		const SessionsPerEra: session::SessionIndex = T::SessionsPerEra::get();
+
+		fn deposit_event<T>() = default;
+
+		fn heartbeat(
+			origin,
+			heartbeat: Heartbeat<T::BlockNumber, T::AuthorityId>,
+			_signature: Vec<u8>
+		) {
+			ensure_none(origin)?;
+
+			let current_session = <session::Module<T>>::current_index();
+			let exists = <ReceivedHeartbeats<T>>::exists(current_session, &heartbeat.authority_id);
+			if !exists {
+				let now = <system::Module<T>>::block_number();
+				Self::deposit_event(RawEvent::HeartbeatReceived(now, heartbeat.authority_id.clone()));
+
+				let network_state = heartbeat.network_state.encode();
+				<ReceivedHeartbeats<T>>::insert(current_session, &heartbeat.authority_id, network_state);
+			}
+		}
+
+		// Runs after every block.
+		fn offchain_worker(now: T::BlockNumber) {
+			fn gossip_at<T: Trait>(block_number: T::BlockNumber) -> Result<(), OffchainErr> {
+				let kind = match <T::AuthorityId as TypedKey>::KEY_TYPE {
+					key_types::SR25519 => CryptoKind::Sr25519,
+					key_types::ED25519 => CryptoKind::Ed25519,
+					_ => return Err(OffchainErr::UnknownCryptoKind),
+				};
+
+				// we run only when a local authority key is configured
+				if let Ok(key) = sr_io::authority_pubkey(kind) {
+					let authority_id = <T as Trait>::AuthorityId::decode(&mut &key[..])
+						.ok_or(OffchainErr::DecodeAuthorityId)?;
+					let network_state =
+						sr_io::network_state().map_err(|_| OffchainErr::NetworkState)?;
+					let heartbeat_data = Heartbeat {
+						block_number,
+						network_state,
+						session_index: <session::Module<T>>::current_index(),
+						authority_id,
+					};
+
+					let signature = sr_io::sign(None, kind, &heartbeat_data.encode())
+						.map_err(|_| OffchainErr::FailedSigning)?;
+					let call = Call::heartbeat(heartbeat_data, signature);
+					let ex = T::UncheckedExtrinsic::new_unsigned(call.into())
+						.ok_or(OffchainErr::ExtrinsicCreation)?;
+					sr_io::submit_transaction(&ex)
+						.map_err(|_| OffchainErr::SubmitTransaction)?;
+					set_worker_status::<T>(block_number, true);
+				}
+				Ok(())
+			}
+
+			fn set_worker_status<T: Trait>(gossipping_at: T::BlockNumber, done: bool) {
+				let enc = WorkerStatus {
+					done,
+					gossipping_at,
+				};
+				sr_io::local_storage_set(StorageKind::PERSISTENT, DB_KEY, &enc.encode());
+			}
+
+			fn was_not_yet_gossipped<T: Trait>(
+				now: T::BlockNumber,
+				next_gossip: T::BlockNumber,
+			) -> Result<bool, OffchainErr> {
+				let last_gossip = sr_io::local_storage_get(StorageKind::PERSISTENT, DB_KEY);
+				match last_gossip {
+					Some(l) => {
+						let worker_status: WorkerStatus<T::BlockNumber> = Decode::decode(&mut &l[..])
+							.ok_or(OffchainErr::DecodeWorkerStatus)?;
+
+						let was_aborted = !worker_status.done && worker_status.gossipping_at < now;
+
+						// another off-chain worker is currently in the process of submitting
+						let already_submitting =
+							!worker_status.done && worker_status.gossipping_at == now;
+
+						let not_yet_gossipped =
+							worker_status.done && worker_status.gossipping_at < next_gossip;
+
+						let ret = (was_aborted && !already_submitting) || not_yet_gossipped;
+						Ok(ret)
+					},
+					None => Ok(true),
+				}
+			}
+
+			let next_gossip = <GossipAt<T>>::get();
+			let not_yet_gossipped = match was_not_yet_gossipped::<T>(now, next_gossip) {
+				Ok(v) => v,
+				Err(err) => {
+					print(err);
+					return;
+				},
+			};
+			if next_gossip < now && not_yet_gossipped {
+				set_worker_status::<T>(now, false);
+
+				match gossip_at::<T>(now) {
+					Ok(_) => {},
+					Err(err) => print(err),
+				}
+			}
+		}
+	}
+}
+
+impl<T: Trait> Module<T> {
+	/// Returns `true` if a heartbeat has been received for `AuthorityId`
+	/// during the current era. Otherwise `false`.
+	pub fn is_online_in_current_era(authority_id: &T::AuthorityId) -> bool {
+		let curr = <session::Module<T>>::current_index();
+		match LastNewEraStart::get() {
+			Some(start) => {
+				// iterate over every session
+				for index in start..curr  {
+					if <ReceivedHeartbeats<T>>::exists(index, authority_id) {
+						return true;
+					}
+				}
+				false
+			},
+			None => <ReceivedHeartbeats<T>>::exists(curr, authority_id),
+		}
+	}
+
+	/// Returns `true` if a heartbeat has been received for `AuthorityId`
+	/// during the current session. Otherwise `false`.
+	pub fn is_online_in_current_session(authority_id: &T::AuthorityId) -> bool {
+		let current_session = <session::Module<T>>::current_index();
+		<ReceivedHeartbeats<T>>::exists(current_session, authority_id)
+	}
+
+	/// Session has just changed.
+	fn new_session() {
+		let now = <system::Module<T>>::block_number();
+		<GossipAt<T>>::put(now);
+
+		let current_session = <session::Module<T>>::current_index();
+
+		match LastNewEraStart::get() {
+			Some(last_new_era_start) => {
+				let sessions_per_era = T::SessionsPerEra::get();
+
+				let new_era = current_session - last_new_era_start > sessions_per_era;
+				if new_era {
+					LastNewEraStart::put(current_session);
+					Self::remove_heartbeats();
+				}
+			},
+			None => LastNewEraStart::put(current_session),
+		};
+	}
+
+	// Remove all stored heartbeats.
+	fn remove_heartbeats() {
+		let curr = <session::Module<T>>::current_index();
+		match LastNewEraStart::get() {
+			Some(start) => {
+				for index in start..curr {
+					<ReceivedHeartbeats<T>>::remove_prefix(index);
+				}
+			},
+			None => <ReceivedHeartbeats<T>>::remove_prefix(curr),
+		}
+	}
+}
+
+impl<T: Trait> session::OneSessionHandler<T::AccountId> for Module<T> {
+	type Key = <T as Trait>::AuthorityId;
+
+	fn on_new_session<'a, I: 'a>(_changed: bool, _validators: I) {
+		Self::new_session();
+	}
+
+	fn on_disabled(_i: usize) {
+		// ignore
+	}
+}
+
+impl<T: Trait> srml_support::unsigned::ValidateUnsigned for Module<T> {
+	type Call = Call<T>;
+
+	fn validate_unsigned(call: &Self::Call) -> srml_support::unsigned::TransactionValidity {
+		if let Call::heartbeat(heartbeat, signature) = call {
+			// verify that the incoming (unverified) pubkey is actually an authority id
+			let is_authority = T::IsValidAuthorityId::is_member(&heartbeat.authority_id);
+			if !is_authority {
+				return TransactionValidity::Invalid(ApplyError::BadSignature as i8);
+			}
+
+			if <Module<T>>::is_online_in_current_session(&heartbeat.authority_id) {
+				// we already received a heartbeat for this authority
+				return TransactionValidity::Invalid(ApplyError::BadSignature as i8);
+			}
+
+			if signature.len() != 64 {
+				return TransactionValidity::Invalid(ApplyError::BadSignature as i8);
+			}
+
+			let signature = {
+				  let mut array = [0; 64];
+				  array.copy_from_slice(&signature); // panics if not enough, hence the check above
+				  array
+			};
+
+			let encoded_heartbeat = heartbeat.encode();
+
+			let signature_valid = match <T::AuthorityId as TypedKey>::KEY_TYPE {
+				ed25519::Public::KEY_TYPE =>
+					sr_io::ed25519_verify(&signature, &encoded_heartbeat, &heartbeat.authority_id),
+				sr25519::Public::KEY_TYPE =>
+					sr_io::sr25519_verify(&signature, &encoded_heartbeat, &heartbeat.authority_id),
+				_ => return TransactionValidity::Invalid(ApplyError::BadSignature as i8),
+			};
+
+			if !signature_valid {
+				return TransactionValidity::Invalid(ApplyError::BadSignature as i8);
+			}
+
+			// check if session index from heartbeat is recent
+			let current_session = <session::Module<T>>::current_index();
+			if heartbeat.session_index < current_session {
+				return TransactionValidity::Invalid(ApplyError::BadSignature as i8);
+			}
+
+			return srml_support::unsigned::TransactionValidity::Valid {
+				priority: 0,
+				requires: vec![],
+				provides: vec![encoded_heartbeat],
+				longevity: TransactionLongevity::max_value(),
+				propagate: true,
+			}
+		}
+		TransactionValidity::Invalid(0)
+	}
+}