feat: consensus fixes and block sync

consensus/src/consensus.rs

@@ -15,11 +15,24 @@ use crate::state::{
 /// - A M-notarization for a block, for the current view (it can be proposed by any replica)
 /// - A L-notarization for a block, for the current view (it can be proposed by any replica)
 /// - A nullification for a view, for the current view (it can be proposed by any replica)
+/// - A block recovery request/response for fetching missing blocks from peers
 #[derive(Clone, Debug, Archive, Deserialize, Serialize)]
 pub enum ConsensusMessage<const N: usize, const F: usize, const M_SIZE: usize> {
     BlockProposal(Block),
     Vote(Vote),
     Nullify(Nullify),
     MNotarization(MNotarization<N, F, M_SIZE>),
     Nullification(Nullification<N, F, M_SIZE>),
+    /// Request a missing block by view and expected hash. Sent when a replica has M-notarization
+    /// for a view but never received the actual block proposal from the leader.
+    BlockRecoveryRequest {
+        view: u64,
+        block_hash: [u8; 32],
+    },
+    /// Response containing the requested block. Sent by a peer that has the block in its
+    /// non-finalized view chain or finalized storage.
+    BlockRecoveryResponse {
+        view: u64,
+        block: Block,
+    },
 }

consensus/src/consensus_manager/events.rs

@@ -196,4 +196,22 @@ pub enum ViewProgressEvent<const N: usize, const F: usize, const M_SIZE: usize>
         /// The starting view that triggered the nullification (where conflict was detected)
         start_view: u64,
     },
+
+    /// If the current replica should request a missing block from peers.
+    /// This happens when a view has received M-notarization (block_hash is known)
+    /// but the actual block proposal was never received from the leader.
+    ShouldRequestBlock {
+        /// The view number for which the block is missing.
+        view: u64,
+        /// The expected block hash (from the M-notarization).
+        block_hash: [u8; blake3::OUT_LEN],
+    },
+
+    /// If the current replica should request multiple missing blocks from peers.
+    /// This is the batch version of `ShouldRequestBlock`, used when multiple views
+    /// need block recovery simultaneously (e.g., after a node joins late).
+    ShouldRequestBlocks {
+        /// The list of (view, block_hash) pairs for which blocks are missing.
+        requests: Vec<(u64, [u8; blake3::OUT_LEN])>,
+    },
 }