Gloas lookup sync boilerplate (#9322)

Implements the boring boilerplate to send envelopes by root requests and process them. Pre-step to

- https://github.com/sigp/lighthouse/pull/9155


  


Co-Authored-By: dapplion <35266934+dapplion@users.noreply.github.com>

beacon_node/network/src/router.rs

@@ -26,6 +26,7 @@ use tokio_stream::wrappers::UnboundedReceiverStream;
 use tracing::{debug, error, trace, warn};
 use types::{
     BlobSidecar, DataColumnSidecar, EthSpec, ForkContext, PartialDataColumn, SignedBeaconBlock,
+    SignedExecutionPayloadEnvelope,
 };
 
 /// Handles messages from the network and routes them to the appropriate service to be handled.
@@ -348,10 +349,13 @@ impl<T: BeaconChainTypes> Router<T> {
             Response::DataColumnsByRange(data_column) => {
                 self.on_data_columns_by_range_response(peer_id, app_request_id, data_column);
             }
-            // TODO(EIP-7732): implement outgoing payload envelopes by range and root
-            // responses once sync manager requests them.
-            Response::PayloadEnvelopesByRoot(_) | Response::PayloadEnvelopesByRange(_) => {
-                debug!("Requesting envelopes by root and by range not supported yet");
+            Response::PayloadEnvelopesByRoot(envelope) => {
+                self.on_payload_envelopes_by_root_response(peer_id, app_request_id, envelope);
+            }
+            // TODO(EIP-7732): implement outgoing payload envelopes by range responses
+            // once sync manager requests them.
+            Response::PayloadEnvelopesByRange(_) => {
+                debug!("Requesting envelopes by range not supported yet");
             }
             // Lighthouse currently only serves BlocksByHead and does not issue it as a client,
             // so receiving a response is unexpected. Drop it without crashing.
@@ -821,6 +825,29 @@ impl<T: BeaconChainTypes> Router<T> {
         }
     }
 
+    /// Handle a `PayloadEnvelopesByRoot` response from the peer.
+    pub fn on_payload_envelopes_by_root_response(
+        &mut self,
+        peer_id: PeerId,
+        app_request_id: AppRequestId,
+        envelope: Option<Arc<SignedExecutionPayloadEnvelope<T::EthSpec>>>,
+    ) {
+        let sync_request_id = match app_request_id {
+            AppRequestId::Sync(id @ SyncRequestId::SinglePayloadEnvelope { .. }) => id,
+            other => {
+                crit!(request = ?other, %peer_id, "PayloadEnvelopesByRoot response on incorrect request");
+                return;
+            }
+        };
+
+        self.send_to_sync(SyncMessage::RpcPayloadEnvelope {
+            sync_request_id,
+            peer_id,
+            envelope,
+            seen_timestamp: self.chain.slot_clock.now_duration().unwrap_or_default(),
+        });
+    }
+
     fn handle_beacon_processor_send_result(
         &mut self,
         result: Result<(), crate::network_beacon_processor::Error<T::EthSpec>>,