Simplify blob verification

michaelsproul · michaelsproul · commit 645c8696e98b · 2025-09-24T18:57:53.000+10:00
diff --git a/beacon_node/beacon_chain/src/blob_verification.rs b/beacon_node/beacon_chain/src/blob_verification.rs
@@ -5,8 +5,7 @@ use std::sync::Arc;
 
 use crate::beacon_chain::{BeaconChain, BeaconChainTypes};
 use crate::block_verification::{
-    BlockSlashInfo, cheap_state_advance_to_obtain_committees, get_validator_pubkey_cache,
-    process_block_slash_info,
+    BlockSlashInfo, get_validator_pubkey_cache, process_block_slash_info,
 };
 use crate::kzg_utils::{validate_blob, validate_blobs};
 use crate::observed_data_sidecars::{ObservationStrategy, Observe};
@@ -494,59 +493,32 @@ pub fn validate_blob_sidecar_for_gossip<T: BeaconChainTypes, O: ObservationStrat
     }
 
     let proposer_shuffling_root =
-        if parent_block.slot.epoch(T::EthSpec::slots_per_epoch()) == blob_epoch {
-            parent_block
-                .next_epoch_shuffling_id
-                .shuffling_decision_block
-        } else {
-            parent_block.root
-        };
-
-    let proposer_opt = chain
-        .beacon_proposer_cache
-        .lock()
-        .get_slot::<T::EthSpec>(proposer_shuffling_root, blob_slot);
-
-    let (proposer_index, fork) = if let Some(proposer) = proposer_opt {
-        (proposer.index, proposer.fork)
-    } else {
-        debug!(
-            %block_root,
-            %blob_index,
-            "Proposer shuffling cache miss for blob verification"
-        );
-        let (parent_state_root, mut parent_state) = chain
-            .store
-            .get_advanced_hot_state(block_parent_root, blob_slot, parent_block.state_root)
-            .map_err(|e| GossipBlobError::BeaconChainError(Box::new(e.into())))?
-            .ok_or_else(|| {
-                BeaconChainError::DBInconsistent(format!(
-                    "Missing state for parent block {block_parent_root:?}",
-                ))
-            })?;
-
-        let state = cheap_state_advance_to_obtain_committees::<_, GossipBlobError>(
-            &mut parent_state,
-            Some(parent_state_root),
-            blob_slot,
-            &chain.spec,
-        )?;
-
-        let epoch = state.current_epoch();
-        let proposers = state.get_beacon_proposer_indices(epoch, &chain.spec)?;
-        let proposer_index = *proposers
-            .get(blob_slot.as_usize() % T::EthSpec::slots_per_epoch() as usize)
-            .ok_or_else(|| BeaconChainError::NoProposerForSlot(blob_slot))?;
-
-        // Prime the proposer shuffling cache with the newly-learned value.
-        chain.beacon_proposer_cache.lock().insert(
-            blob_epoch,
-            proposer_shuffling_root,
-            proposers,
-            state.fork(),
-        )?;
-        (proposer_index, state.fork())
+        parent_block.proposer_shuffling_root_for_child_block(blob_epoch, &chain.spec);
+
+    let Some(proposer) = chain.with_proposer_cache(
+        proposer_shuffling_root,
+        blob_epoch,
+        |cache| cache.get_slot::<T::EthSpec>(proposer_shuffling_root, blob_slot),
+        || {
+            debug!(
+                %block_root,
+                index = %blob_index,
+                "Proposer shuffling cache miss for blob verification"
+            );
+            chain
+                .store
+                .get_advanced_hot_state(block_parent_root, blob_slot, parent_block.state_root)
+                .map_err(|e| GossipBlobError::BeaconChainError(Box::new(e.into())))
+        },
+    )?
+    else {
+        return Err(BeaconChainError::DBInconsistent(format!(
+            "Missing state for parent block {block_parent_root:?}",
+        ))
+        .into());
     };
+    let proposer_index = proposer.index;
+    let fork = proposer.fork;
 
     // Signature verify the signed block header.
     let signature_is_valid = {
