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feat: Allow follower nodes to backfill blocks #679

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feat: Allow follower nodes to backfill blocks #679

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4847c48
feat: Allow followers to backfill blocks if they are behind
adityapk00 Jul 16, 2026
7e35bf2
clippy
adityapk00 Jul 16, 2026
1e53917
separate out channels for backfill
adityapk00 Jul 16, 2026
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30 changes: 11 additions & 19 deletions crates/node/src/node.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@

use crate::{
ZoneEngine,
replication::{broadcast_persisted_blocks, import_leader_blocks},
replication::{broadcast_persisted_blocks, run_block_sync},
rpc::{ZoneRpc, ZoneRpcApi, rpc_connection_config, start_private_rpc},
};
use alloy_primitives::Address;
Expand Down Expand Up @@ -557,25 +557,17 @@ where
events,
} = handle.into_parts();

match role {
Role::Leader => {
task_executor.spawn_critical_task(
"zone-p2p-block-broadcast",
broadcast_persisted_blocks(provider, commands),
);
// Leaders do not receive block messages. Dropping this receiver is harmless: the
// runtime only emits BlockReceived on followers.
drop(events);
}
Role::Follower => {
// Keep the command sender alive so the runtime's command loop remains available
// for later ACK/backfill commands even though followers send nothing in this PR.
task_executor.spawn_critical_task(
"zone-p2p-block-import",
import_leader_blocks(provider, engine, events, commands),
);
}
if role == Role::Leader {
// Only a leader can build + broadcast blocks
task_executor.spawn_critical_task(
"zone-p2p-block-broadcast",
broadcast_persisted_blocks(provider.clone(), commands.clone()),
);
}
task_executor.spawn_critical_task(
"zone-p2p-block-sync",
run_block_sync(provider, engine, events, commands),

@tempoxyz-bot tempoxyz-bot Jul 16, 2026

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🚨 [SECURITY] Leader backfill advances the execution head without reconciling ZoneEngine state

Spawning run_block_sync for leaders lets P2P imports advance the provider/EL head through the Reth engine handle, but that path cannot update ZoneEngine::last_header, DepositQueue, or the TIP-403 policy-cache baseline. A valid imported block can leave the sequencer believing it is still at the old parent, causing duplicate L1 reprocessing attempts, competing blocks, or persistent leader liveness failure.

Recommended Fix: Disable leader P2P import while ZoneEngine is active, run recovery before starting/seeding the sequencer state, or add an atomic reconciliation API that advances last_header, confirms queued L1 blocks, and updates the policy cache through imported history.

@adityapk00 adityapk00 Jul 16, 2026

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This is TBD, leader backfill needs slightly different code, will be in a follow-up PR.

);

task_executor.spawn_critical_with_graceful_shutdown_signal(
"zone-p2p",
Expand Down
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