Reward submitters only when submitted block is finalized (#34)

* reward submitters on finalization

* fix grumble

* make submitter part of ImportContext

bridges/modules/ethereum/src/finality.rs

@@ -49,9 +49,10 @@ pub fn finalize_blocks<S: Storage>(
 	best_finalized_hash: &H256,
 	header_validators: (&H256, &[Address]),
 	hash: &H256,
+	submitter: Option<&S::Submitter>,
 	header: &Header,
 	two_thirds_majority_transition: u64,
-) -> Result<Vec<(u64, H256)>, Error> {
+) -> Result<Vec<(u64, H256, Option<S::Submitter>)>, Error> {
 	// compute count of voters for every unfinalized block in ancestry
 	let validators = header_validators.1.iter().collect();
 	let (mut votes, mut headers) = prepare_votes(
@@ -61,18 +62,19 @@ pub fn finalize_blocks<S: Storage>(
 		&validators,
 		hash,
 		header,
+		submitter,
 		two_thirds_majority_transition,
 	)?;
 
 	// now let's iterate in reverse order && find just finalized blocks
 	let mut newly_finalized = Vec::new();
-	while let Some((oldest_hash, oldest_number, signers)) = headers.pop_front() {
+	while let Some((oldest_hash, oldest_number, submitter, signers)) = headers.pop_front() {
 		if !is_finalized(&validators, &votes, oldest_number >= two_thirds_majority_transition) {
 			break;
 		}
 
 		remove_signers_votes(&signers, &mut votes);
-		newly_finalized.push((oldest_number, oldest_hash));
+		newly_finalized.push((oldest_number, oldest_hash, submitter));
 	}
 
 	Ok(newly_finalized)
@@ -96,8 +98,9 @@ fn prepare_votes<S: Storage>(
 	validators: &BTreeSet<&Address>,
 	hash: &H256,
 	header: &Header,
+	submitter: Option<&S::Submitter>,
 	two_thirds_majority_transition: u64,
-) -> Result<(BTreeMap<Address, u64>, VecDeque<(H256, u64, BTreeSet<Address>)>), Error> {
+) -> Result<(BTreeMap<Address, u64>, VecDeque<(H256, u64, Option<S::Submitter>, BTreeSet<Address>)>), Error> {
 	// this fn can only work with single validators set
 	if !validators.contains(&header.author) {
 		return Err(Error::NotValidator);
@@ -108,17 +111,17 @@ fn prepare_votes<S: Storage>(
 	// the same set of validators
 	let mut parent_empty_step_signers = empty_steps_signers(header);
 	let ancestry = ancestry(storage, header)
-		.map(|(hash, header)| {
+		.map(|(hash, header, submitter)| {
 			let mut signers = BTreeSet::new();
 			sp_std::mem::swap(&mut signers, &mut parent_empty_step_signers);
 			signers.insert(header.author);
 
 			let empty_step_signers = empty_steps_signers(&header);
-			let res = (hash, header.number, signers);
+			let res = (hash, header.number, submitter, signers);
 			parent_empty_step_signers = empty_step_signers;
 			res
 		})
-		.take_while(|&(hash, _, _)| hash != *validators_begin && hash != *best_finalized_hash);
+		.take_while(|&(hash, _, _, _)| hash != *validators_begin && hash != *best_finalized_hash);
 
 	// now let's iterate built iterator and compute number of validators
 	// 'voted' for each header
@@ -126,21 +129,21 @@ fn prepare_votes<S: Storage>(
 	// just finalized blocks)
 	let mut votes = BTreeMap::new();
 	let mut headers = VecDeque::new();
-	for (hash, number, signers) in ancestry {
+	for (hash, number, submitter, signers) in ancestry {
 		add_signers_votes(validators, &signers, &mut votes)?;
 		if is_finalized(validators, &votes, number >= two_thirds_majority_transition) {
 			remove_signers_votes(&signers, &mut votes);
 			break;
 		}
 
-		headers.push_front((hash, number, signers));
+		headers.push_front((hash, number, submitter, signers));
 	}
 
 	// update votes with last header vote
 	let mut header_signers = BTreeSet::new();
 	header_signers.insert(header.author);
 	*votes.entry(header.author).or_insert(0) += 1;
-	headers.push_back((*hash, header.number, header_signers));
+	headers.push_back((*hash, header.number, submitter.cloned(), header_signers));
 
 	Ok((votes, headers))
 }
@@ -211,6 +214,7 @@ mod tests {
 				&Default::default(),
 				(&Default::default(), &[]),
 				&Default::default(),
+				None,
 				&Header::default(),
 				0,
 			),
@@ -233,7 +237,7 @@ mod tests {
 		};
 		let hash1 = header1.hash();
 		let mut header_to_import = HeaderToImport {
-			context: storage.import_context(&genesis().hash()).unwrap(),
+			context: storage.import_context(None, &genesis().hash()).unwrap(),
 			is_best: true,
 			hash: hash1,
 			header: header1,
@@ -247,6 +251,7 @@ mod tests {
 				&Default::default(),
 				(&Default::default(), &validators_addresses(5)),
 				&hash1,
+				None,
 				&header_to_import.header,
 				u64::max_value(),
 			),
@@ -269,6 +274,7 @@ mod tests {
 				&Default::default(),
 				(&Default::default(), &validators_addresses(5)),
 				&hash2,
+				None,
 				&header_to_import.header,
 				u64::max_value(),
 			),
@@ -291,10 +297,11 @@ mod tests {
 				&Default::default(),
 				(&Default::default(), &validators_addresses(5)),
 				&hash3,
+				None,
 				&header_to_import.header,
 				u64::max_value(),
 			),
-			Ok(vec![(1, hash1)]),
+			Ok(vec![(1, hash1, None)]),
 		);
 		storage.insert_header(header_to_import);
 	}

bridges/modules/ethereum/src/import.rs

@@ -36,7 +36,10 @@ use crate::validators::{Validators, ValidatorsConfiguration};
 use crate::verification::verify_aura_header;
 use crate::{AuraConfiguration, Storage};
 use primitives::{Header, Receipt, H256};
-use sp_std::prelude::*;
+use sp_std::{
+	collections::btree_map::BTreeMap,
+	prelude::*,
+};
 
 /// Maximal number of headers behind best blocks that we are aiming to store. When there
 /// are too many unfinalized headers, it slows down finalization tracking significantly.
@@ -61,15 +64,32 @@ pub fn import_headers<S: Storage>(
 	aura_config: &AuraConfiguration,
 	validators_config: &ValidatorsConfiguration,
 	prune_depth: u64,
+	submitter: Option<S::Submitter>,
 	headers: Vec<(Header, Option<Vec<Receipt>>)>,
+	finalized_headers: &mut BTreeMap<S::Submitter, u64>,
 ) -> Result<(u64, u64), Error> {
 	let mut useful = 0;
 	let mut useless = 0;
 	for (header, receipts) in headers {
-		let import_result = import_header(storage, aura_config, validators_config, prune_depth, header, receipts);
+		let import_result = import_header(
+			storage,
+			aura_config,
+			validators_config,
+			prune_depth,
+			submitter.clone(),
+			header,
+			receipts,
+		);
 
 		match import_result {
-			Ok(_) => useful += 1,
+			Ok((_, finalized)) => {
+				for (_, _, submitter) in finalized {
+					if let Some(submitter) = submitter {
+						*finalized_headers.entry(submitter).or_default() += 1;
+					}
+				}
+				useful += 1;
+			},
 			Err(Error::AncientHeader) | Err(Error::KnownHeader) => useless += 1,
 			Err(error) => return Err(error),
 		}
@@ -82,19 +102,22 @@ pub fn import_headers<S: Storage>(
 ///
 /// Transactions receipts must be provided if `header_import_requires_receipts()`
 /// has returned true.
+///
+/// Returns imported block hash.
 pub fn import_header<S: Storage>(
 	storage: &mut S,
 	aura_config: &AuraConfiguration,
 	validators_config: &ValidatorsConfiguration,
 	prune_depth: u64,
+	submitter: Option<S::Submitter>,
 	header: Header,
 	receipts: Option<Vec<Receipt>>,
-) -> Result<H256, Error> {
+) -> Result<(H256, Vec<(u64, H256, Option<S::Submitter>)>), Error> {
 	// first check that we are able to import this header at all
 	let (hash, prev_finalized_hash) = is_importable_header(storage, &header)?;
 
 	// verify header
-	let import_context = verify_aura_header(storage, aura_config, &header)?;
+	let import_context = verify_aura_header(storage, aura_config, submitter, &header)?;
 
 	// check if block schedules new validators
 	let validators = Validators::new(validators_config);
@@ -106,6 +129,7 @@ pub fn import_header<S: Storage>(
 		&prev_finalized_hash,
 		(import_context.validators_start(), import_context.validators()),
 		&hash,
+		import_context.submitter(),
 		&header,
 		aura_config.two_thirds_majority_transition,
 	)?;
@@ -119,25 +143,27 @@ pub fn import_header<S: Storage>(
 	let total_difficulty = import_context.total_difficulty() + header.difficulty;
 	let is_best = total_difficulty > best_total_difficulty;
 	let header_number = header.number;
-	storage.insert_header(import_context.into_import_header(
+	storage.insert_header(
-		is_best,
+		import_context.into_import_header(
-		hash,
+			is_best,
-		header,
+			hash,
-		total_difficulty,
+			header,
-		enacted_change,
+			total_difficulty,
-		scheduled_change,
+			enacted_change,
-	));
+			scheduled_change,
+		),
+	);
 
 	// now mark finalized headers && prune old headers
 	storage.finalize_headers(
-		finalized_blocks.last().cloned(),
+		finalized_blocks.last().map(|(number, hash, _)| (*number, *hash)),
 		match is_best {
 			true => header_number.checked_sub(prune_depth),
 			false => None,
 		},
 	);
 
-	Ok(hash)
+	Ok((hash, finalized_blocks))
 }
 
 /// Returns true if transactions receipts are required to import given header.
@@ -189,6 +215,7 @@ mod tests {
 				&kovan_aura_config(),
 				&kovan_validators_config(),
 				PRUNE_DEPTH,
+				None,
 				Default::default(),
 				None,
 			),
@@ -207,6 +234,7 @@ mod tests {
 				&kovan_aura_config(),
 				&kovan_validators_config(),
 				PRUNE_DEPTH,
+				None,
 				block.clone(),
 				None,
 			)
@@ -219,6 +247,7 @@ mod tests {
 				&kovan_aura_config(),
 				&kovan_validators_config(),
 				PRUNE_DEPTH,
+				None,
 				block,
 				None,
 			)
@@ -243,6 +272,7 @@ mod tests {
 				&kovan_aura_config(),
 				&validators_config,
 				PRUNE_DEPTH,
+				None,
 				header,
 				None
 			)
@@ -267,43 +297,67 @@ mod tests {
 
 		// header [0..11] are finalizing blocks [0; 9]
 		// => since we want to keep 10 finalized blocks, we aren't pruning anything
-		let mut last_block_hash = Default::default();
+		let mut latest_block_hash = Default::default();
 		for i in 1..11 {
 			let header = block_i(&storage, i, &validators);
-			last_block_hash =
+			let (rolling_last_block_hash, finalized_blocks) =
-				import_header(&mut storage, &kovan_aura_config(), &validators_config, 10, header, None).unwrap();
+				import_header(
+					&mut storage,
+					&kovan_aura_config(),
+					&validators_config,
+					10,
+					Some(100),
+					header,
+					None,
+				).unwrap();
+			match i {
+				2 ..= 10 => assert_eq!(
+					finalized_blocks,
+					vec![(i - 1, block_i(&storage, i - 1, &validators).hash(), Some(100))],
+					"At {}",
+					i,
+				),
+				_ => assert_eq!(finalized_blocks, vec![], "At {}", i),
+			}
+			latest_block_hash = rolling_last_block_hash;
 		}
 		assert!(storage.header(&genesis().hash()).is_some());
 
 		// header 11 finalizes headers [10] AND schedules change
 		// => we prune header#0
-		let header = custom_block_i(&storage, 11, &validators, |header| {
+		let header11 = custom_block_i(&storage, 11, &validators, |header| {
 			header.log_bloom = (&[0xff; 256]).into();
 			header.receipts_root = "2e60346495092587026484e868a5b3063749032b2ea3843844509a6320d7f951"
 				.parse()
 				.unwrap();
 		});
-		last_block_hash = import_header(
+		let (rolling_last_block_hash, finalized_blocks) = import_header(
 			&mut storage,
 			&kovan_aura_config(),
 			&validators_config,
 			10,
-			header,
+			Some(101),
+			header11.clone(),
 			Some(vec![crate::validators::tests::validators_change_recept(
-				last_block_hash,
+				latest_block_hash,
 			)]),
-		)
+		).unwrap();
-		.unwrap();
+		assert_eq!(
+			finalized_blocks,
+			vec![(10, block_i(&storage, 10, &validators).hash(), Some(100))],
+		);
 		assert!(storage.header(&genesis().hash()).is_none());
+		latest_block_hash = rolling_last_block_hash;
 
 		// and now let's say validators 1 && 2 went offline
 		// => in the range 12-25 no blocks are finalized, but we still continue to prune old headers
 		// until header#11 is met. we can't prune #11, because it schedules change
 		let mut step = 56;
+		let mut expected_blocks = vec![(11, header11.hash(), Some(101))];
 		for i in 12..25 {
 			let header = Header {
 				number: i as _,
-				parent_hash: last_block_hash,
+				parent_hash: latest_block_hash,
 				gas_limit: 0x2000.into(),
 				author: validator(2).address().to_fixed_bytes().into(),
 				seal: vec![vec![step].into(), vec![].into()],
@@ -311,8 +365,22 @@ mod tests {
 				..Default::default()
 			};
 			let header = signed_header(&validators, header, step as _);
-			last_block_hash =
+			expected_blocks.push((i, header.hash(), Some(102)));
-				import_header(&mut storage, &kovan_aura_config(), &validators_config, 10, header, None).unwrap();
+			let (rolling_last_block_hash, finalized_blocks) =
+				import_header(
+					&mut storage,
+					&kovan_aura_config(),
+					&validators_config,
+					10,
+					Some(102),
+					header,
+					None,
+				).unwrap();
+			assert_eq!(
+				finalized_blocks,
+				vec![],
+			);
+			latest_block_hash = rolling_last_block_hash;
 			step += 3;
 		}
 		assert_eq!(storage.oldest_unpruned_block(), 11);
@@ -322,7 +390,7 @@ mod tests {
 		step -= 2;
 		let header = Header {
 			number: 25,
-			parent_hash: last_block_hash,
+			parent_hash: latest_block_hash,
 			gas_limit: 0x2000.into(),
 			author: validator(0).address().to_fixed_bytes().into(),
 			seal: vec![vec![step].into(), vec![].into()],
@@ -330,7 +398,16 @@ mod tests {
 			..Default::default()
 		};
 		let header = signed_header(&validators, header, step as _);
-		import_header(&mut storage, &kovan_aura_config(), &validators_config, 10, header, None).unwrap();
+		let (_, finalized_blocks) = import_header(
+			&mut storage,
+			&kovan_aura_config(),
+			&validators_config,
+			10,
+			Some(103),
+			header,
+			None,
+		).unwrap();
+		assert_eq!(finalized_blocks, expected_blocks);
 		assert_eq!(storage.oldest_unpruned_block(), 15);
 	}
 }

bridges/modules/ethereum/src/lib.rs

@@ -36,7 +36,12 @@ use codec::{Decode, Encode};
 use frame_support::{decl_module, decl_storage};
 use primitives::{Address, Header, Receipt, H256, U256};
 use sp_runtime::RuntimeDebug;
-use sp_std::{iter::from_fn, prelude::*};
+use sp_std::{
+	prelude::*,
+	cmp::Ord,
+	collections::btree_map::BTreeMap,
+	iter::from_fn,
+};
 use validators::{ValidatorsConfiguration, ValidatorsSource};
 
 pub use import::{header_import_requires_receipts, import_header};
@@ -70,7 +75,10 @@ pub struct AuraConfiguration {
 
 /// Block header as it is stored in the runtime storage.
 #[derive(Clone, Encode, Decode, PartialEq, RuntimeDebug)]
-pub struct StoredHeader {
+pub struct StoredHeader<Submitter> {
+	/// Submitter of this header. May be `None` if header has been submitted
+	/// using unsigned transaction.
+	pub submitter: Option<Submitter>,
 	/// The block header itself.
 	pub header: Header,
 	/// Total difficulty of the chain.
@@ -85,9 +93,9 @@ pub struct StoredHeader {
 /// Header that we're importing.
 #[derive(RuntimeDebug)]
 #[cfg_attr(test, derive(Clone, PartialEq))]
-pub struct HeaderToImport {
+pub struct HeaderToImport<Submitter> {
 	/// Header import context,
-	pub context: ImportContext,
+	pub context: ImportContext<Submitter>,
 	/// Should we consider this header as best?
 	pub is_best: bool,
 	/// The hash of the header.
@@ -105,22 +113,25 @@ pub struct HeaderToImport {
 /// Header import context.
 #[derive(RuntimeDebug)]
 #[cfg_attr(test, derive(Clone, PartialEq))]
-pub struct ImportContext {
+pub struct ImportContext<Submitter> {
+	submitter: Option<Submitter>,
 	parent_header: Header,
 	parent_total_difficulty: U256,
 	next_validators_set_id: u64,
 	next_validators_set: (H256, Vec<Address>),
 }
 
-impl ImportContext {
+impl<Submitter> ImportContext<Submitter> {
 	/// Create import context using passing parameters;
 	pub fn new(
+		submitter: Option<Submitter>,
 		parent_header: Header,
 		parent_total_difficulty: U256,
 		next_validators_set_id: u64,
 		next_validators_set: (H256, Vec<Address>),
 	) -> Self {
 		ImportContext {
+			submitter,
 			parent_header,
 			parent_total_difficulty,
 			next_validators_set_id,
@@ -128,6 +139,11 @@ impl ImportContext {
 		}
 	}
 
+	/// Returns reference to header submitter (if known).
+	pub fn submitter(&self) -> Option<&Submitter> {
+		self.submitter.as_ref()
+	}
+
 	/// Returns reference to parent header.
 	pub fn parent_header(&self) -> &Header {
 		&self.parent_header
@@ -162,7 +178,7 @@ impl ImportContext {
 		total_difficulty: U256,
 		enacted_change: Option<Vec<Address>>,
 		scheduled_change: Option<Vec<Address>>,
-	) -> HeaderToImport {
+	) -> HeaderToImport<Submitter> {
 		HeaderToImport {
 			context: self,
 			is_best,
@@ -179,18 +195,27 @@ impl ImportContext {
 ///
 /// Storage modification must be discarded if block import has failed.
 pub trait Storage {
+	/// Header submitter identifier.
+	type Submitter: Clone + Ord;
+
 	/// Get best known block.
 	fn best_block(&self) -> (u64, H256, U256);
 	/// Get last finalized block.
 	fn finalized_block(&self) -> (u64, H256);
 	/// Get imported header by its hash.
-	fn header(&self, hash: &H256) -> Option<Header>;
+	///
+	/// Returns header and its submitter (if known).
+	fn header(&self, hash: &H256) -> Option<(Header, Option<Self::Submitter>)>;
 	/// Get header import context by parent header hash.
-	fn import_context(&self, parent_hash: &H256) -> Option<ImportContext>;
+	fn import_context(
+		&self,
+		submitter: Option<Self::Submitter>,
+		parent_hash: &H256,
+	) -> Option<ImportContext<Self::Submitter>>;
 	/// Get new validators that are scheduled by given header.
 	fn scheduled_change(&self, hash: &H256) -> Option<Vec<Address>>;
 	/// Insert imported header.
-	fn insert_header(&mut self, header: HeaderToImport);
+	fn insert_header(&mut self, header: HeaderToImport<Self::Submitter>);
 	/// Finalize given block and prune all headers with number < prune_end.
 	/// The headers in the pruning range could be either finalized, or not.
 	/// It is the storage duty to ensure that unfinalized headers that have
@@ -202,14 +227,25 @@ pub trait Storage {
 /// Decides whether the session should be ended.
 pub trait OnHeadersSubmitted<AccountId> {
 	/// Called when valid headers have been submitted.
+	///
+	/// The submitter **must not** be rewarded for submitting valid headers, because greedy authority
+	/// could produce and submit multiple valid headers (without relaying them to other peers) and
+	/// get rewarded. Instead, the provider could track submitters and stop rewarding if too many
+	/// headers have been submitted without finalization.
 	fn on_valid_headers_submitted(submitter: AccountId, useful: u64, useless: u64);
 	/// Called when invalid headers have been submitted.
 	fn on_invalid_headers_submitted(submitter: AccountId);
+	/// Called when earlier submitted headers have been finalized.
+	///
+	/// finalized is the number of headers that submitter has submitted and which
+	/// have been finalized.
+	fn on_valid_headers_finalized(submitter: AccountId, finalized: u64);
 }
 
 impl<AccountId> OnHeadersSubmitted<AccountId> for () {
 	fn on_valid_headers_submitted(_submitter: AccountId, _useful: u64, _useless: u64) {}
 	fn on_invalid_headers_submitted(_submitter: AccountId) {}
+	fn on_valid_headers_finalized(_submitter: AccountId, _finalized: u64) {}
 }
 
 /// The module configuration trait
@@ -228,14 +264,27 @@ decl_module! {
 		/// enormous block production/import time.
 		pub fn import_headers(origin, headers_with_receipts: Vec<(Header, Option<Vec<Receipt>>)>) {
 			let submitter = frame_system::ensure_signed(origin)?;
+			let mut finalized_headers = BTreeMap::new();
 			let import_result = import::import_headers(
-				&mut BridgeStorage,
+				&mut BridgeStorage::<T>::new(),
 				&kovan_aura_config(),
 				&kovan_validators_config(),
 				crate::import::PRUNE_DEPTH,
+				Some(submitter.clone()),
 				headers_with_receipts,
+				&mut finalized_headers,
 			);
 
+			// if we have finalized some headers, we will reward their submitters even
+			// if current submitter has provided some invalid headers
+			for (f_submitter, f_count) in finalized_headers {
+				T::OnHeadersSubmitted::on_valid_headers_finalized(
+					f_submitter,
+					f_count,
+				);
+			}
+
+			// now track/penalize current submitter for providing new headers
 			match import_result {
 				Ok((useful, useless)) =>
 					T::OnHeadersSubmitted::on_valid_headers_submitted(submitter, useful, useless),
@@ -259,7 +308,7 @@ decl_storage! {
 		/// Oldest unpruned block(s) number.
 		OldestUnprunedBlock: u64;
 		/// Map of imported headers by hash.
-		Headers: map hasher(blake2_256) H256 => Option<StoredHeader>;
+		Headers: map hasher(blake2_256) H256 => Option<StoredHeader<T::AccountId>>;
 		/// Map of imported header hashes by number.
 		HeadersByNumber: map hasher(blake2_256) u64 => Option<Vec<H256>>;
 		/// The ID of next validator set.
@@ -293,7 +342,8 @@ decl_storage! {
 			FinalizedBlock::put((config.initial_header.number, initial_hash));
 			OldestUnprunedBlock::put(config.initial_header.number);
 			HeadersByNumber::insert(config.initial_header.number, vec![initial_hash]);
-			Headers::insert(initial_hash, StoredHeader {
+			Headers::<T>::insert(initial_hash, StoredHeader {
+				submitter: None,
 				header: config.initial_header.clone(),
 				total_difficulty: config.initial_difficulty,
 				next_validators_set_id: 0,
@@ -310,25 +360,34 @@ impl<T: Trait> Module<T> {
 	/// The caller should only submit `import_header` transaction that makes
 	/// (or leads to making) other header the best one.
 	pub fn best_block() -> (u64, H256) {
-		let (number, hash, _) = BridgeStorage.best_block();
+		let (number, hash, _) = BridgeStorage::<T>::new().best_block();
 		(number, hash)
 	}
 
 	/// Returns true if the import of given block requires transactions receipts.
 	pub fn is_import_requires_receipts(header: Header) -> bool {
-		import::header_import_requires_receipts(&BridgeStorage, &kovan_validators_config(), &header)
+		import::header_import_requires_receipts(&BridgeStorage::<T>::new(), &kovan_validators_config(), &header)
 	}
 
 	/// Returns true if header is known to the runtime.
 	pub fn is_known_block(hash: H256) -> bool {
-		BridgeStorage.header(&hash).is_some()
+		BridgeStorage::<T>::new().header(&hash).is_some()
 	}
 }
 
 /// Runtime bridge storage.
-struct BridgeStorage;
+#[derive(Default)]
+struct BridgeStorage<T>(sp_std::marker::PhantomData<T>);
+
+impl<T> BridgeStorage<T> {
+	pub fn new() -> Self {
+		BridgeStorage(sp_std::marker::PhantomData::<T>::default())
+	}
+}
+
+impl<T: Trait> Storage for BridgeStorage<T> {
+	type Submitter = T::AccountId;
 
-impl Storage for BridgeStorage {
 	fn best_block(&self) -> (u64, H256, U256) {
 		BestBlock::get()
 	}
@@ -337,16 +396,21 @@ impl Storage for BridgeStorage {
 		FinalizedBlock::get()
 	}
 
-	fn header(&self, hash: &H256) -> Option<Header> {
+	fn header(&self, hash: &H256) -> Option<(Header, Option<Self::Submitter>)> {
-		Headers::get(hash).map(|header| header.header)
+		Headers::<T>::get(hash).map(|header| (header.header, header.submitter))
 	}
 
-	fn import_context(&self, parent_hash: &H256) -> Option<ImportContext> {
+	fn import_context(
-		Headers::get(parent_hash).map(|parent_header| {
+		&self,
+		submitter: Option<Self::Submitter>,
+		parent_hash: &H256,
+	) -> Option<ImportContext<Self::Submitter>> {
+		Headers::<T>::get(parent_hash).map(|parent_header| {
 			let (next_validators_set_start, next_validators) =
 				ValidatorsSets::get(parent_header.next_validators_set_id)
 					.expect("validators set is only pruned when last ref is pruned; there is a ref; qed");
 			ImportContext {
+				submitter,
 				parent_header: parent_header.header,
 				parent_total_difficulty: parent_header.total_difficulty,
 				next_validators_set_id: parent_header.next_validators_set_id,
@@ -359,7 +423,7 @@ impl Storage for BridgeStorage {
 		ScheduledChanges::get(hash)
 	}
 
-	fn insert_header(&mut self, header: HeaderToImport) {
+	fn insert_header(&mut self, header: HeaderToImport<Self::Submitter>) {
 		if header.is_best {
 			BestBlock::put((header.header.number, header.hash, header.total_difficulty));
 		}
@@ -387,9 +451,10 @@ impl Storage for BridgeStorage {
 		};
 
 		HeadersByNumber::append_or_insert(header.header.number, vec![header.hash]);
-		Headers::insert(
+		Headers::<T>::insert(
 			&header.hash,
 			StoredHeader {
+				submitter: header.context.submitter,
 				header: header.header,
 				total_difficulty: header.total_difficulty,
 				next_validators_set_id,
@@ -426,7 +491,7 @@ impl Storage for BridgeStorage {
 
 				// physically remove headers and (probably) obsolete validators sets
 				for hash in blocks_at_number.into_iter().flat_map(|x| x) {
-					let header = Headers::take(&hash);
+					let header = Headers::<T>::take(&hash);
 					ScheduledChanges::remove(hash);
 					if let Some(header) = header {
 						ValidatorsSetsRc::mutate(header.next_validators_set_id, |rc| match *rc {
@@ -570,19 +635,22 @@ pub fn kovan_validators_config() -> ValidatorsConfiguration {
 }
 
 /// Return iterator of given header ancestors.
-pub(crate) fn ancestry<'a, S: Storage>(storage: &'a S, header: &Header) -> impl Iterator<Item = (H256, Header)> + 'a {
+pub(crate) fn ancestry<'a, S: Storage>(
+	storage: &'a S,
+	header: &Header,
+) -> impl Iterator<Item = (H256, Header, Option<S::Submitter>)> + 'a {
 	let mut parent_hash = header.parent_hash.clone();
 	from_fn(move || {
-		let header = storage.header(&parent_hash);
+		let header_and_submitter = storage.header(&parent_hash);
-		match header {
+		match header_and_submitter {
-			Some(header) => {
+			Some((header, submitter)) => {
 				if header.number == 0 {
 					return None;
 				}
 
 				let hash = parent_hash.clone();
 				parent_hash = header.parent_hash.clone();
-				Some((hash, header))
+				Some((hash, header, submitter))
 			}
 			None => None,
 		}
@@ -596,6 +664,8 @@ pub(crate) mod tests {
 	use primitives::{rlp_encode, H520};
 	use std::collections::{hash_map::Entry, HashMap};
 
+	pub type AccountId = u64;
+
 	pub fn genesis() -> Header {
 		Header {
 			seal: vec![vec![42].into(), vec![].into()],
@@ -651,7 +721,7 @@ pub(crate) mod tests {
 		best_block: (u64, H256, U256),
 		finalized_block: (u64, H256),
 		oldest_unpruned_block: u64,
-		headers: HashMap<H256, StoredHeader>,
+		headers: HashMap<H256, StoredHeader<AccountId>>,
 		headers_by_number: HashMap<u64, Vec<H256>>,
 		next_validators_set_id: u64,
 		validators_sets: HashMap<u64, (H256, Vec<Address>)>,
@@ -670,6 +740,7 @@ pub(crate) mod tests {
 				headers: vec![(
 					hash,
 					StoredHeader {
+						submitter: None,
 						header: initial_header,
 						total_difficulty: 0.into(),
 						next_validators_set_id: 0,
@@ -688,12 +759,14 @@ pub(crate) mod tests {
 			self.oldest_unpruned_block
 		}
 
-		pub(crate) fn stored_header(&self, hash: &H256) -> Option<&StoredHeader> {
+		pub(crate) fn stored_header(&self, hash: &H256) -> Option<&StoredHeader<AccountId>> {
 			self.headers.get(hash)
 		}
 	}
 
 	impl Storage for InMemoryStorage {
+		type Submitter = AccountId;
+
 		fn best_block(&self) -> (u64, H256, U256) {
 			self.best_block.clone()
 		}
@@ -702,15 +775,20 @@ pub(crate) mod tests {
 			self.finalized_block.clone()
 		}
 
-		fn header(&self, hash: &H256) -> Option<Header> {
+		fn header(&self, hash: &H256) -> Option<(Header, Option<Self::Submitter>)> {
-			self.headers.get(hash).map(|header| header.header.clone())
+			self.headers.get(hash).map(|header| (header.header.clone(), header.submitter.clone()))
 		}
 
-		fn import_context(&self, parent_hash: &H256) -> Option<ImportContext> {
+		fn import_context(
+			&self,
+			submitter: Option<Self::Submitter>,
+			parent_hash: &H256,
+		) -> Option<ImportContext<Self::Submitter>> {
 			self.headers.get(parent_hash).map(|parent_header| {
 				let (next_validators_set_start, next_validators) =
 					self.validators_sets.get(&parent_header.next_validators_set_id).unwrap();
 				ImportContext {
+					submitter,
 					parent_header: parent_header.header.clone(),
 					parent_total_difficulty: parent_header.total_difficulty,
 					next_validators_set_id: parent_header.next_validators_set_id,
@@ -723,7 +801,7 @@ pub(crate) mod tests {
 			self.scheduled_changes.get(hash).cloned()
 		}
 
-		fn insert_header(&mut self, header: HeaderToImport) {
+		fn insert_header(&mut self, header: HeaderToImport<Self::Submitter>) {
 			if header.is_best {
 				self.best_block = (header.header.number, header.hash, header.total_difficulty);
 			}
@@ -755,6 +833,7 @@ pub(crate) mod tests {
 			self.headers.insert(
 				header.hash,
 				StoredHeader {
+					submitter: header.context.submitter,
 					header: header.header,
 					total_difficulty: header.total_difficulty,
 					next_validators_set_id,

bridges/modules/ethereum/src/validators.rs

@@ -198,9 +198,9 @@ impl<'a> Validators<'a> {
 	pub fn finalize_validators_change<S: Storage>(
 		&self,
 		storage: &mut S,
-		finalized_blocks: &[(u64, H256)],
+		finalized_blocks: &[(u64, H256, Option<S::Submitter>)],
 	) -> Option<Vec<Address>> {
-		for (_, finalized_hash) in finalized_blocks.iter().rev() {
+		for (_, finalized_hash, _) in finalized_blocks.iter().rev() {
 			if let Some(changes) = storage.scheduled_change(finalized_hash) {
 				return Some(changes);
 			}

bridges/modules/ethereum/src/verification.rs

@@ -40,14 +40,15 @@ use sp_io::crypto::secp256k1_ecdsa_recover;
 pub fn verify_aura_header<S: Storage>(
 	storage: &S,
 	params: &AuraConfiguration,
+	submitter: Option<S::Submitter>,
 	header: &Header,
-) -> Result<ImportContext, Error> {
+) -> Result<ImportContext<S::Submitter>, Error> {
 	// let's do the lightest check first
 	contextless_checks(params, header)?;
 
 	// the rest of checks requires parent
 	let context = storage
-		.import_context(&header.parent_hash)
+		.import_context(submitter, &header.parent_hash)
 		.ok_or(Error::MissingParentBlock)?;
 	let validators = context.validators();
 	let header_step = header.step().ok_or(Error::MissingStep)?;
@@ -179,7 +180,7 @@ fn verify_signature(expected_validator: &Address, signature: &H520, message: &H2
 mod tests {
 	use super::*;
 	use crate::kovan_aura_config;
-	use crate::tests::{genesis, signed_header, validator, validators_addresses, InMemoryStorage};
+	use crate::tests::{genesis, signed_header, validator, validators_addresses, AccountId, InMemoryStorage};
 	use parity_crypto::publickey::{sign, KeyPair};
 	use primitives::{rlp_encode, H520};
 
@@ -197,12 +198,15 @@ mod tests {
 		empty_step
 	}
 
-	fn verify_with_config(config: &AuraConfiguration, header: &Header) -> Result<ImportContext, Error> {
+	fn verify_with_config(
+		config: &AuraConfiguration,
+		header: &Header,
+	) -> Result<ImportContext<AccountId>, Error> {
 		let storage = InMemoryStorage::new(genesis(), validators_addresses(3));
-		verify_aura_header(&storage, &config, header)
+		verify_aura_header(&storage, &config, None, header)
 	}
 
-	fn default_verify(header: &Header) -> Result<ImportContext, Error> {
+	fn default_verify(header: &Header) -> Result<ImportContext<AccountId>, Error> {
 		verify_with_config(&kovan_aura_config(), header)
 	}