feat(l1): reorg re-injection for mempool transactions and blob sidecars

cmd/ethrex/cli.rs

@@ -10,7 +10,7 @@ use std::{
 
 use clap::{ArgAction, Parser as ClapParser, Subcommand as ClapSubcommand};
 use ethrex_blockchain::{
-    BlockchainOptions, BlockchainType, L2Config,
+    BlockchainOptions, BlockchainType, DEFAULT_MEMPOOL_REORG_DEPTH, L2Config,
     error::{ChainError, InvalidBlockError},
 };
 use ethrex_common::types::{Block, DEFAULT_BUILDER_GAS_CEIL, Genesis, validate_block_body};
@@ -183,6 +183,15 @@ pub struct Options {
         env = "ETHREX_MEMPOOL_MAX_SIZE"
     )]
     pub mempool_max_size: usize,
+    #[arg(
+        help = "Maximum reorg depth (in blocks) for which transactions in orphaned blocks are re-injected into the mempool. Deeper reorgs skip re-injection.",
+        long = "mempool.reorg-depth",
+        default_value_t = DEFAULT_MEMPOOL_REORG_DEPTH,
+        value_name = "MEMPOOL_REORG_DEPTH",
+        help_heading = "Node options",
+        env = "ETHREX_MEMPOOL_REORG_DEPTH"
+    )]
+    pub mempool_reorg_depth: u64,
     #[arg(
         long = "http.addr",
         default_value = "0.0.0.0",
@@ -392,6 +401,7 @@ impl Options {
             discv4_enabled: true,
             discv5_enabled: true,
             mempool_max_size: 10_000,
+            mempool_reorg_depth: DEFAULT_MEMPOOL_REORG_DEPTH,
             ..Default::default()
         }
     }
@@ -414,6 +424,7 @@ impl Options {
             discv4_enabled: true,
             discv5_enabled: true,
             mempool_max_size: 10_000,
+            mempool_reorg_depth: DEFAULT_MEMPOOL_REORG_DEPTH,
             ..Default::default()
         }
     }
@@ -450,6 +461,7 @@ impl Default for Options {
             dev: Default::default(),
             force: false,
             mempool_max_size: Default::default(),
+            mempool_reorg_depth: DEFAULT_MEMPOOL_REORG_DEPTH,
             tx_broadcasting_time_interval: Default::default(),
             target_peers: Default::default(),
             lookup_interval: Default::default(),

cmd/ethrex/initializers.rs

@@ -529,6 +529,7 @@ pub async fn init_l1(
             max_blobs_per_block: opts.max_blobs_per_block,
             precompute_witnesses: opts.precompute_witnesses,
             precompile_cache_enabled: !opts.no_precompile_cache,
+            reorg_depth: opts.mempool_reorg_depth,
         },
     );
 

cmd/ethrex/l2/initializers.rs

@@ -224,6 +224,7 @@ pub async fn init_l2(
         max_blobs_per_block: None, // L2 doesn't support blob transactions
         precompute_witnesses: opts.node_opts.precompute_witnesses,
         precompile_cache_enabled: true,
+        reorg_depth: opts.node_opts.mempool_reorg_depth,
     };
 
     let blockchain = init_blockchain(store.clone(), blockchain_opts.clone());

crates/blockchain/blockchain.rs

@@ -119,6 +119,12 @@ use ethrex_common::types::BlobsBundle;
 const MAX_PAYLOADS: usize = 10;
 const MAX_MEMPOOL_SIZE_DEFAULT: usize = 10_000;
 
+/// Maximum reorg depth (in blocks) for which orphaned-block transactions are
+/// re-injected into the mempool. Reorgs deeper than this are treated as
+/// catastrophic — re-injection is skipped to bound the amount of work done
+/// during fork-choice processing.
+pub const DEFAULT_MEMPOOL_REORG_DEPTH: u64 = 64;
+
 /// Background thread for dropping large tree structures off the critical path.
 /// Accepts any `Send` value and drops it on a dedicated thread, avoiding
 /// recursive deallocation costs (~500us for state trie roots) on hot paths.
@@ -231,6 +237,10 @@ pub struct BlockchainOptions {
     /// warmer thread and the executor. Set to false (via `--no-precompile-cache`) to
     /// disable the cache for benchmarking purposes.
     pub precompile_cache_enabled: bool,
+    /// Maximum reorg depth (in blocks) for which transactions in orphaned
+    /// blocks are re-injected into the mempool. Reorgs deeper than this skip
+    /// re-injection and log a warning.
+    pub reorg_depth: u64,
 }
 
 impl Default for BlockchainOptions {
@@ -242,6 +252,7 @@ impl Default for BlockchainOptions {
             max_blobs_per_block: None,
             precompute_witnesses: false,
             precompile_cache_enabled: true,
+            reorg_depth: DEFAULT_MEMPOOL_REORG_DEPTH,
         }
     }
 }
@@ -2374,10 +2385,175 @@ impl Blockchain {
         self.mempool.remove_transaction(hash)
     }
 
-    /// Remove all transactions in the executed block from the pool (if we have them)
+    /// Remove all transactions in the executed block from the pool (if we have them).
+    ///
+    /// For blob (EIP-4844) transactions, the sidecars are moved into the mempool
+    /// limbo rather than discarded, so they remain available for re-injection if
+    /// the block gets orphaned by a reorg. Limbo entries are purged once the
+    /// block is finalized.
     pub fn remove_block_transactions_from_pool(&self, block: &Block) -> Result<(), StoreError> {
         for tx in &block.body.transactions {
-            self.mempool.remove_transaction(&tx.hash())?;
+            self.mempool.remove_included_transaction(&tx.hash())?;
+        }
+        Ok(())
+    }
+
+    /// Re-inject transactions that were in orphaned blocks back into the mempool
+    /// after a reorg, with full admission re-validation.
+    ///
+    /// Behaviour:
+    /// - If the reorg depth exceeds `options.reorg_depth`, the entire re-injection
+    ///   is skipped and a warning is logged.
+    /// - Each transaction is admitted via the same path as a freshly-submitted tx
+    ///   (`add_transaction_to_pool` / `add_blob_transaction_to_pool`), so all
+    ///   stateful checks (nonce/balance under the new canonical head) are applied.
+    /// - For blob transactions, the sidecar is pulled from the mempool limbo. If
+    ///   the sidecar is missing (e.g. the node was restarted between block
+    ///   inclusion and the reorg), the blob tx is dropped silently — there is no
+    ///   way to reconstruct sidecars.
+    /// - Failures are logged at debug level and the loop continues; re-injection
+    ///   is strictly best-effort.
+    ///
+    /// Returns the number of transactions actually re-injected.
+    pub async fn reinject_orphaned_transactions(
+        &self,
+        previous_head_hash: H256,
+        new_head_hash: H256,
+    ) -> Result<usize, StoreError> {
+        let Some(branches) =
+            fork_choice::find_common_ancestor(&self.storage, previous_head_hash, new_head_hash)
+                .await?
+        else {
+            debug!(
+                previous_head = %previous_head_hash,
+                new_head = %new_head_hash,
+                "Could not compute common ancestor for reorg re-injection; skipping",
+            );
+            return Ok(0);
+        };
+
+        let depth = branches.depth();
+        if depth == 0 {
+            // Not a reorg (e.g. the new head was a descendant of the previous head).
+            return Ok(0);
+        }
+
+        if depth > self.options.reorg_depth {
+            warn!(
+                depth,
+                cap = self.options.reorg_depth,
+                previous_head = %previous_head_hash,
+                new_head = %new_head_hash,
+                "Reorg deeper than configured cap; skipping mempool re-injection",
+            );
+            return Ok(0);
+        }
+
+        let txs = fork_choice::collect_orphaned_transactions(&self.storage, &branches).await?;
+        info!(
+            depth,
+            orphaned_tx_count = txs.len(),
+            previous_head = %previous_head_hash,
+            new_head = %new_head_hash,
+            "Reorg detected; re-injecting orphaned transactions into mempool",
+        );
+
+        let mut reinjected = 0usize;
+        for tx in txs {
+            let tx_hash = tx.hash();
+            match tx {
+                #[cfg(feature = "c-kzg")]
+                Transaction::EIP4844Transaction(inner) => {
+                    let Some(blobs_bundle) = self.mempool.take_blob_limbo_entry(&tx_hash)? else {
+                        debug!(
+                            tx_hash = %tx_hash,
+                            "Blob sidecar missing from limbo; cannot re-inject orphaned EIP-4844 tx",
+                        );
+                        continue;
+                    };
+                    match self.add_blob_transaction_to_pool(inner, blobs_bundle).await {
+                        Ok(_) => reinjected += 1,
+                        Err(error) => {
+                            debug!(
+                                tx_hash = %tx_hash,
+                                %error,
+                                "Failed to re-inject orphaned EIP-4844 transaction",
+                            );
+                        }
+                    }
+                }
+                #[cfg(not(feature = "c-kzg"))]
+                Transaction::EIP4844Transaction(_) => {
+                    debug!(
+                        tx_hash = %tx_hash,
+                        "Skipping orphaned EIP-4844 transaction (c-kzg feature disabled)",
+                    );
+                }
+                other => match self.add_transaction_to_pool(other).await {
+                    Ok(_) => reinjected += 1,
+                    Err(error) => {
+                        debug!(
+                            tx_hash = %tx_hash,
+                            %error,
+                            "Failed to re-inject orphaned transaction",
+                        );
+                    }
+                },
+            }
+        }
+        Ok(reinjected)
+    }
+
+    /// Purge blob sidecars from the mempool limbo for all transactions in
+    /// blocks between (exclusive) the previously-finalized block and (inclusive)
+    /// the newly-finalized block.
+    ///
+    /// Once a block is finalized it cannot be reorged, so we no longer need to
+    /// hold on to its blob sidecars. `previous_finalized_hash` may be zero on
+    /// the very first finalization advance, in which case purging walks back
+    /// until genesis (or as far as block bodies are available).
+    pub async fn purge_finalized_blob_limbo(
+        &self,
+        previous_finalized_hash: H256,
+        new_finalized_hash: H256,
+    ) -> Result<(), StoreError> {
+        if new_finalized_hash.is_zero() || previous_finalized_hash == new_finalized_hash {
+            return Ok(());
+        }
+
+        // Walk from new_finalized back to previous_finalized, collecting tx
+        // hashes for every block we pass through. We bound the walk by the
+        // configured reorg depth so a misconfigured / malicious previous_hash
+        // cannot cause unbounded work.
+        let max_walk = self.options.reorg_depth;
+        let mut current_hash = new_finalized_hash;
+        let mut steps = 0u64;
+        let mut hashes_to_purge: Vec<H256> = Vec::new();
+        while current_hash != previous_finalized_hash && !current_hash.is_zero() {
+            if steps > max_walk {
+                debug!(
+                    steps,
+                    cap = max_walk,
+                    "Blob limbo purge walked past the reorg-depth cap; stopping",
+                );
+                break;
+            }
+            let Some(header) = self.storage.get_block_header_by_hash(current_hash)? else {
+                break;
+            };
+            if let Some(body) = self.storage.get_block_body_by_hash(current_hash).await? {
+                for tx in body.transactions {
+                    hashes_to_purge.push(tx.hash());
+                }
+            }
+            if header.number == 0 {
+                break;
+            }
+            current_hash = header.parent_hash;
+            steps += 1;
+        }
+        if !hashes_to_purge.is_empty() {
+            self.mempool.purge_blob_limbo_entries(&hashes_to_purge)?;
         }
         Ok(())
     }