refactor: Drop fork reconciliation memory limit

There is already a memory limit being enforced implicitly, namely through:

1. Requiring that every block have a size less than or equal to
   `MAX_BLOCK_SIZE_IN_FORK_RECONCILIATION`.

2. Requiring that the number of blocks being reconciled does not exceed
   `self.global_state_lock.cli().sync_mode_threshold`.

This commit removes the memory limit in `try_ensure_path` as well as the state
variable used to track memory use for fork reconciliation.

Author: aszepieniec

neptune-core/src/application/loops/peer_loop.rs

@@ -76,10 +76,6 @@ const MINIMUM_BLOCK_BATCH_SIZE: usize = 2;
 const MAX_BLOCK_SIZE_IN_FORK_RECONCILIATION: usize =
     2 * 8 * ConsensusRuleSet::HardforkAlpha.max_block_size();
 
-/// Maximum total bytes for all blocks in fork_reconciliation_blocks.
-/// This caps overall memory usage during fork resolution.
-const MAX_FORK_RECONCILIATION_TOTAL_BYTES: usize = 100 * 1024 * 1024;
-
 /// Maximum size of a single announcement, in BFieldElements. Typical encrypted
 /// UTXO notifications are ~400 BFEs. This limit provides headroom while
 /// preventing DoS via oversized announcements.
@@ -456,25 +452,6 @@ impl PeerLoopHandler {
             );
             self.punish(NegativePeerSanction::OversizedBlock).await?;
             peer_state.fork_reconciliation_blocks.clear();
-            peer_state.fork_reconciliation_bytes = 0;
-            return Ok(());
-        }
-
-        // Reject if total memory budget would be exceeded
-        let new_total_bytes = peer_state
-            .fork_reconciliation_bytes
-            .saturating_add(block_size);
-        if new_total_bytes > MAX_FORK_RECONCILIATION_TOTAL_BYTES {
-            warn!(
-                "Fork reconciliation memory budget exceeded: {} + {} = {} bytes (max: {} bytes)",
-                peer_state.fork_reconciliation_bytes,
-                block_size,
-                new_total_bytes,
-                MAX_FORK_RECONCILIATION_TOTAL_BYTES
-            );
-            self.punish(NegativePeerSanction::OversizedBlock).await?;
-            peer_state.fork_reconciliation_blocks.clear();
-            peer_state.fork_reconciliation_bytes = 0;
             return Ok(());
         }
 
@@ -519,13 +496,11 @@ impl PeerLoopHandler {
             )))
             .await?;
             peer_state.fork_reconciliation_blocks = vec![];
-            peer_state.fork_reconciliation_bytes = 0;
             return Ok(());
         }
 
         // otherwise, append
         peer_state.fork_reconciliation_blocks.push(*received_block);
-        peer_state.fork_reconciliation_bytes = new_total_bytes;
 
         // Try fetch parent
         let received_block_header = *peer_state
@@ -559,7 +534,6 @@ impl PeerLoopHandler {
         let Some(parent_block) = parent_block else {
             if parent_height.is_genesis() {
                 peer_state.fork_reconciliation_blocks.clear();
-                peer_state.fork_reconciliation_bytes = 0;
                 self.punish(NegativePeerSanction::DifferentGenesis).await?;
                 return Ok(());
             }
@@ -584,7 +558,6 @@ impl PeerLoopHandler {
         // block that we have.
         let fork_reconciliation_event = !peer_state.fork_reconciliation_blocks.is_empty();
         peer_state.fork_reconciliation_blocks.clear();
-        peer_state.fork_reconciliation_bytes = 0;
 
         if let Some(new_block_height) = self.handle_blocks(new_blocks, parent_block).await? {
             // If `BlockNotification` was received during a block reconciliation

neptune-core/src/protocol/peer.rs

@@ -624,9 +624,6 @@ impl PeerMessage {
 pub struct MutablePeerState {
     pub highest_shared_block_height: BlockHeight,
     pub fork_reconciliation_blocks: Vec<Block>,
-    /// Total estimated bytes of blocks in fork_reconciliation_blocks.
-    /// Used to cap memory usage during fork resolution.
-    pub(crate) fork_reconciliation_bytes: usize,
     pub(crate) sync_challenge: Option<IssuedSyncChallenge>,
 
     /// Timestamp for the last successful sync challenge response.
@@ -640,7 +637,6 @@ impl MutablePeerState {
         Self {
             highest_shared_block_height: block_height,
             fork_reconciliation_blocks: vec![],
-            fork_reconciliation_bytes: 0,
             sync_challenge: None,
             successful_sync_challenge_response_time: None,
         }