Always send full parent header, not only hash, part of collation response

polkadot/node/network/collator-protocol/src/collator_side/collation.rs

@@ -25,9 +25,8 @@ use polkadot_node_network_protocol::{
 	PeerId,
 };
 use polkadot_node_primitives::PoV;
-use polkadot_node_subsystem::messages::ParentHeadData;
 use polkadot_primitives::{
-	vstaging::CandidateReceiptV2 as CandidateReceipt, CandidateHash, Hash, Id as ParaId,
+	vstaging::CandidateReceiptV2 as CandidateReceipt, CandidateHash, Hash, HeadData, Id as ParaId,
 };
 
 /// The status of a collation as seen from the collator.
@@ -72,8 +71,8 @@ pub struct Collation {
 	pub receipt: CandidateReceipt,
 	/// Proof to verify the state transition of the parachain.
 	pub pov: PoV,
-	/// Parent head-data (or just hash).
-	pub parent_head_data: ParentHeadData,
+	/// Parent head-data
+	pub parent_head_data: HeadData,
 	/// Collation status.
 	pub status: CollationStatus,
 }

polkadot/node/network/collator-protocol/src/collator_side/mod.rs

@@ -39,9 +39,7 @@ use polkadot_node_network_protocol::{
 };
 use polkadot_node_primitives::{CollationSecondedSignal, PoV, Statement};
 use polkadot_node_subsystem::{
-	messages::{
-		CollatorProtocolMessage, NetworkBridgeEvent, NetworkBridgeTxMessage, ParentHeadData,
-	},
+	messages::{CollatorProtocolMessage, NetworkBridgeEvent, NetworkBridgeTxMessage},
 	overseer, FromOrchestra, OverseerSignal,
 };
 use polkadot_node_subsystem_util::{
@@ -381,7 +379,6 @@ async fn distribute_collation<Context>(
 	state: &mut State,
 	id: ParaId,
 	receipt: CandidateReceipt,
-	parent_head_data_hash: Hash,
 	pov: PoV,
 	parent_head_data: HeadData,
 	result_sender: Option<oneshot::Sender<CollationSecondedSignal>>,
@@ -508,12 +505,6 @@ async fn distribute_collation<Context>(
 		state.collation_result_senders.insert(candidate_hash, result_sender);
 	}
 
-	let parent_head_data = if elastic_scaling {
-		ParentHeadData::WithData { hash: parent_head_data_hash, head_data: parent_head_data }
-	} else {
-		ParentHeadData::OnlyHash(parent_head_data_hash)
-	};
-
 	let para_head = receipt.descriptor.para_head();
 	per_relay_parent.collations.insert(
 		candidate_hash,
@@ -786,7 +777,7 @@ async fn process_msg<Context>(
 		},
 		DistributeCollation {
 			candidate_receipt,
-			parent_head_data_hash,
+			parent_head_data_hash: _,
 			pov,
 			parent_head_data,
 			result_sender,
@@ -811,7 +802,6 @@ async fn process_msg<Context>(
 						state,
 						id,
 						candidate_receipt,
-						parent_head_data_hash,
 						pov,
 						parent_head_data,
 						result_sender,
@@ -859,24 +849,19 @@ async fn send_collation(
 	request: VersionedCollationRequest,
 	receipt: CandidateReceipt,
 	pov: PoV,
-	parent_head_data: ParentHeadData,
+	parent_head_data: HeadData,
 ) {
 	let (tx, rx) = oneshot::channel();
 
 	let relay_parent = request.relay_parent();
 	let peer_id = request.peer_id();
 	let candidate_hash = receipt.hash();
 
-	let result = match parent_head_data {
-		ParentHeadData::WithData { head_data, .. } =>
-			Ok(request_v2::CollationFetchingResponse::CollationWithParentHeadData {
-				receipt,
-				pov,
-				parent_head_data: head_data,
-			}),
-		ParentHeadData::OnlyHash(_) =>
-			Ok(request_v2::CollationFetchingResponse::Collation(receipt, pov)),
-	};
+	let result = Ok(request_v2::CollationFetchingResponse::CollationWithParentHeadData {
+		receipt,
+		pov,
+		parent_head_data,
+	});
 
 	let response =
 		OutgoingResponse { result, reputation_changes: Vec::new(), sent_feedback: Some(tx) };

polkadot/node/network/collator-protocol/src/collator_side/tests/mod.rs

@@ -521,7 +521,8 @@ fn decode_collation_response(bytes: &[u8]) -> (CandidateReceipt, PoV) {
 	let response: CollationFetchingResponse =
 		CollationFetchingResponse::decode(&mut &bytes[..]).expect("Decoding should work");
 	match response {
-		CollationFetchingResponse::Collation(receipt, pov) => (receipt, pov),
+		CollationFetchingResponse::Collation(_, _) =>
+			panic!("Expected to always receive CollationWithParentHeadData"),
 		CollationFetchingResponse::CollationWithParentHeadData { receipt, pov, .. } =>
 			(receipt, pov),
 	}

prdoc/pr_8939.prdoc

@@ -0,0 +1,11 @@
+title: Always send full parent header, not only hash, part of collation response
+doc:
+- audience: Node Dev
+  description: |-
+    Implementation of https://github.com/paritytech/polkadot-sdk/issues/7733
+
+    # Description
+    Instead of **conditionally** sending the full parent header in the collation response we now **always** send it (never the hash of it).
+crates:
+- name: polkadot-collator-protocol
+  bump: patch