feat(p2p): use BlocksByRange for long-range sync

crates/net/p2p/src/lib.rs

@@ -41,7 +41,7 @@ use crate::{
     },
     req_resp::{
         BLOCKS_BY_RANGE_PROTOCOL_V1, BLOCKS_BY_ROOT_PROTOCOL_V1, Codec,
-        MAX_COMPRESSED_PAYLOAD_SIZE, Request, STATUS_PROTOCOL_V1, build_status,
+        MAX_COMPRESSED_PAYLOAD_SIZE, MAX_REQUEST_BLOCKS, Request, STATUS_PROTOCOL_V1, build_status,
         fetch_block_from_peer,
     },
     swarm_adapter::SwarmHandle,
@@ -59,6 +59,9 @@ const MAX_FETCH_RETRIES: u32 = 10;
 const INITIAL_BACKOFF_MS: u64 = 5;
 const BACKOFF_MULTIPLIER: u64 = 2;
 const PEER_REDIAL_INTERVAL_SECS: u64 = 12;
+const LONG_RANGE_SYNC_THRESHOLD: u64 = 2;
+const MAX_SYNC_RANGE: u64 = MAX_REQUEST_BLOCKS * 64; // 65,536 slots (~3 days)
+const MAX_SLOT_LOOKBACK: u64 = MAX_REQUEST_BLOCKS * 4; // 4 096 slots
 
 pub(crate) struct PendingRequest {
     pub(crate) attempts: u32,
@@ -302,6 +305,7 @@ impl P2P {
             connected_peers: HashSet::new(),
             pending_requests: HashMap::new(),
             request_id_map: HashMap::new(),
+            range_request_ids: HashSet::new(),
             bootnode_addrs: built.bootnode_addrs,
             node_names,
         };
@@ -338,6 +342,7 @@ pub struct P2PServer {
     pub(crate) connected_peers: HashSet<PeerId>,
     pub(crate) pending_requests: HashMap<H256, PendingRequest>,
     pub(crate) request_id_map: HashMap<OutboundRequestId, H256>,
+    pub(crate) range_request_ids: HashSet<OutboundRequestId>,
     bootnode_addrs: HashMap<PeerId, Multiaddr>,
     node_names: HashMap<PeerId, String>,
 }

crates/net/p2p/src/req_resp/handlers.rs

@@ -12,13 +12,14 @@ use ethlambda_types::primitives::HashTreeRoot as _;
 use ethlambda_types::{block::SignedBlock, primitives::H256};
 
 use super::{
-    BLOCKS_BY_ROOT_PROTOCOL_V1, BlocksByRangeRequest, BlocksByRootRequest, MAX_REQUEST_BLOCKS,
-    Request, Response, ResponsePayload, Status,
+    BLOCKS_BY_RANGE_PROTOCOL_V1, BLOCKS_BY_ROOT_PROTOCOL_V1, BlocksByRangeRequest,
+    BlocksByRootRequest, MAX_REQUEST_BLOCKS, Request, Response, ResponsePayload, Status,
     messages::{ResponseCode, error_message},
 };
 use crate::{
-    BACKOFF_MULTIPLIER, INITIAL_BACKOFF_MS, MAX_FETCH_RETRIES, P2PServer, PendingRequest,
-    p2p_protocol, req_resp::RequestedBlockRoots,
+    BACKOFF_MULTIPLIER, INITIAL_BACKOFF_MS, LONG_RANGE_SYNC_THRESHOLD, MAX_FETCH_RETRIES,
+    MAX_SLOT_LOOKBACK, MAX_SYNC_RANGE, P2PServer, PendingRequest, p2p_protocol,
+    req_resp::RequestedBlockRoots,
 };
 
 pub async fn handle_req_resp_message(
@@ -62,12 +63,18 @@ pub async fn handle_req_resp_message(
                     Response::Success { payload } => match payload {
                         ResponsePayload::Status(status) => {
                             info!(kind = "status_response", peer_count, "P2P message received");
-                            handle_status_response(status, peer).await;
+                            handle_status_response(server, status, peer).await;
                         }
                         ResponsePayload::Blocks(blocks) => {
                             info!(kind = "blocks_response", peer_count, "P2P message received");
-                            handle_blocks_by_root_response(server, blocks, peer, request_id, ctx)
+                            if server.range_request_ids.remove(&request_id) {
+                                handle_blocks_by_range_response(server, blocks, peer).await;
+                            } else {
+                                handle_blocks_by_root_response(
+                                    server, blocks, peer, request_id, ctx,
+                                )
                                 .await;
+                            }
                         }
                     },
                     Response::Error { code, message } => {
@@ -88,6 +95,8 @@ pub async fn handle_req_resp_message(
             // Check if this was a block fetch request
             if let Some(root) = server.request_id_map.remove(&request_id) {
                 handle_fetch_failure(server, root, peer, ctx).await;
+            } else if server.range_request_ids.remove(&request_id) {
+                warn!(%peer, ?request_id, "BlocksByRange request failed");
             }
         }
         request_response::Event::InboundFailure {
@@ -118,8 +127,26 @@ async fn handle_status_request(
     server.swarm_handle.send_response(channel, response);
 }
 
-async fn handle_status_response(status: Status, peer: PeerId) {
+async fn handle_status_response(server: &mut P2PServer, status: Status, peer: PeerId) {
     info!(finalized_slot=%status.finalized.slot, head_slot=%status.head.slot, "Received status response from peer {peer}");
+
+    let our_head_slot = server.store.head_slot();
+    if status.head.slot <= our_head_slot {
+        return;
+    }
+    let gap = status.head.slot - our_head_slot;
+
+    if gap > LONG_RANGE_SYNC_THRESHOLD {
+        // Long-range sync: request blocks by range to efficiently fill large gap.
+        let start_slot = our_head_slot.saturating_add(1);
+        // Cap the range to avoid requesting an excessive number of blocks if the peer is very far ahead.
+        let count = gap.min(MAX_SYNC_RANGE);
+        info!(%peer, start_slot, gap, "Long-range sync: using BlocksByRange");
+        request_blocks_by_range_from_peer(server, peer, start_slot, count).await;
+    } else {
+        // Short-range sync: fetch individual blocks by root, relying on gossip to fill any small gaps.
+        info!(%peer, gap, "Short gap, relying on gossip / FetchBlock for missing slots");
+    }
 }
 
 async fn handle_blocks_by_root_request(
@@ -207,6 +234,12 @@ fn canonical_blocks_by_range(
         return Vec::new();
     };
 
+    // Avoid expensive lookups if the requested range is too far in the past (beyond recent gossip history).
+    let head_slot = store.head_slot();
+    if head_slot.saturating_sub(end_slot) > MAX_SLOT_LOOKBACK {
+        return Vec::new();
+    }
+
     let mut roots_by_slot = HashMap::new();
     let mut current_root = store.head();
 
@@ -282,6 +315,36 @@ async fn handle_blocks_by_root_response(
     }
 }
 
+async fn handle_blocks_by_range_response(
+    server: &mut P2PServer,
+    blocks: Vec<SignedBlock>,
+    peer: PeerId,
+) {
+    info!(%peer, count = blocks.len(), "Received BlocksByRange response");
+
+    if blocks.is_empty() {
+        warn!(%peer, "Received empty BlocksByRange response");
+        return;
+    }
+
+    if let Some(ref blockchain) = server.blockchain {
+        for block in blocks {
+            let block_root = block.message.hash_tree_root();
+            let slot = block.message.slot;
+            // TODO: validate block.message.slot is within the originally requested range.
+            let _ = blockchain.new_block(block).inspect_err(|err| {
+                error!(
+                    %peer,
+                    %slot,
+                    block_root = %ethlambda_types::ShortRoot(&block_root.0),
+                    %err,
+                    "Failed to forward range-fetched block to blockchain"
+                )
+            });
+        }
+    }
+}
+
 /// Build a Status message from the current Store state.
 pub fn build_status(store: &Store) -> Status {
     let finalized = store.latest_finalized();
@@ -380,6 +443,61 @@ pub async fn fetch_block_from_peer(server: &mut P2PServer, root: H256) -> bool {
     true
 }
 
+async fn request_blocks_by_range_from_peer(
+    server: &mut P2PServer,
+    peer: PeerId,
+    start_slot: u64,
+    count: u64,
+) -> bool {
+    if count == 0 {
+        return true;
+    }
+
+    let mut remaining = count;
+    let mut next_slot = start_slot;
+
+    while remaining > 0 {
+        let batch_count = remaining.min(MAX_REQUEST_BLOCKS);
+        let request = BlocksByRangeRequest {
+            start_slot: next_slot,
+            count: batch_count,
+            step: 1,
+        };
+
+        info!(
+            %peer,
+            start_slot = next_slot,
+            count = batch_count,
+            "Sending BlocksByRange request"
+        );
+
+        let Some(request_id) = server
+            .swarm_handle
+            .send_request(
+                peer,
+                Request::BlocksByRange(request),
+                libp2p::StreamProtocol::new(BLOCKS_BY_RANGE_PROTOCOL_V1),
+            )
+            .await
+        else {
+            warn!(
+                %peer,
+                start_slot = next_slot,
+                count = batch_count,
+                "Failed to send BlocksByRange request (swarm adapter closed)"
+            );
+            return false;
+        };
+
+        server.range_request_ids.insert(request_id);
+
+        remaining -= batch_count;
+        next_slot = next_slot.saturating_add(batch_count);
+    }
+
+    true
+}
+
 async fn handle_fetch_failure(
     server: &mut P2PServer,
     root: H256,