feat(l1): engine REST/SSZ API

benches/benches/build_block_benchmark.rs

@@ -150,6 +150,7 @@ fn create_payload_block(genesis_block: &Block, store: &Store) -> (Block, u64) {
         version: 3,
         elasticity_multiplier: 1,
         gas_ceil: DEFAULT_BUILDER_GAS_CEIL,
+        target_gas_limit: None,
     };
     let id = payload_args.id();
     let block = create_payload(&payload_args, store, Bytes::new()).unwrap();

crates/blockchain/payload.rs

@@ -95,6 +95,10 @@ pub struct BuildPayloadArgs {
     pub version: u8,
     pub elasticity_multiplier: u64,
     pub gas_ceil: u64,
+    /// CL-provided target gas limit (EIP-7783, Amsterdam). When `Some`, takes
+    /// precedence over `gas_ceil` for `calc_gas_limit`. `None` falls back to
+    /// the builder's `gas_ceil`.
+    pub target_gas_limit: Option<u64>,
 }
 
 #[derive(Debug, Error)]
@@ -117,6 +121,9 @@ impl BuildPayloadArgs {
         if let Some(beacon_root) = self.beacon_root {
             hasher.update(beacon_root);
         }
+        if let Some(target_gas_limit) = self.target_gas_limit {
+            hasher.update(target_gas_limit.to_be_bytes());
+        }
         let res = &mut hasher.finalize()[..8];
         res[0] = self.version;
         Ok(u64::from_be_bytes(res.try_into().map_err(|_| {
@@ -137,7 +144,8 @@ pub fn create_payload(
         .ok_or_else(|| ChainError::ParentNotFound)?;
     let chain_config = storage.get_chain_config();
     let fork = chain_config.fork(args.timestamp);
-    let gas_limit = calc_gas_limit(parent_block.gas_limit, args.gas_ceil);
+    let desired_gas_limit = args.target_gas_limit.unwrap_or(args.gas_ceil);
+    let gas_limit = calc_gas_limit(parent_block.gas_limit, desired_gas_limit);
     let excess_blob_gas = chain_config
         .get_fork_blob_schedule(args.timestamp)
         .map(|schedule| calc_excess_blob_gas(&parent_block, schedule, fork));
@@ -1072,3 +1080,39 @@ impl PartialOrd for HeadTransaction {
         Some(self.cmp(other))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn base_args() -> BuildPayloadArgs {
+        BuildPayloadArgs {
+            parent: BlockHash::zero(),
+            timestamp: 1_700_000_000,
+            fee_recipient: Address::zero(),
+            random: H256::zero(),
+            withdrawals: None,
+            beacon_root: None,
+            slot_number: Some(42),
+            version: 4,
+            elasticity_multiplier: 2,
+            gas_ceil: 30_000_000,
+            target_gas_limit: None,
+        }
+    }
+
+    #[test]
+    fn payload_id_includes_target_gas_limit() {
+        let a = base_args();
+        let mut b = base_args();
+        b.target_gas_limit = Some(36_000_000);
+        assert_ne!(a.id().unwrap(), b.id().unwrap());
+    }
+
+    #[test]
+    fn payload_id_stable_when_target_unchanged() {
+        let a = base_args();
+        let b = base_args();
+        assert_eq!(a.id().unwrap(), b.id().unwrap());
+    }
+}

crates/l2/sequencer/block_producer.rs

@@ -159,6 +159,7 @@ impl BlockProducer {
             version,
             elasticity_multiplier: self.elasticity_multiplier,
             gas_ceil: self.block_gas_limit,
+            target_gas_limit: None,
         };
         let payload = create_payload(&args, &self.store, Bytes::new())?;
 

crates/networking/rpc/Cargo.toml

@@ -42,10 +42,12 @@ jemalloc_pprof = { version = "0.8.0", optional = true, features = [
 ] }
 spawned-rt.workspace = true
 spawned-concurrency.workspace = true
+futures.workspace = true
 
-# EIP-8025 dependencies (optional)
-libssz-merkle = { workspace = true, optional = true }
-libssz-types = { workspace = true, optional = true }
+# Engine REST/SSZ (execution-apis PR #764)
+libssz.workspace = true
+libssz-derive.workspace = true
+libssz-types.workspace = true
 
 # Clients
 envy = "0.4.2"

crates/networking/rpc/engine/fork_choice.rs

@@ -207,7 +207,7 @@ fn parse(
     Ok((forkchoice_state, payload_attributes))
 }
 
-async fn handle_forkchoice(
+pub(crate) async fn handle_forkchoice(
     fork_choice_state: &ForkChoiceState,
     context: RpcApiContext,
     version: usize,
@@ -382,7 +382,7 @@ async fn handle_forkchoice(
     }
 }
 
-fn validate_attributes_v1(
+pub(crate) fn validate_attributes_v1(
     attributes: &PayloadAttributesV3,
     head_block: &BlockHeader,
 ) -> Result<(), RpcErr> {
@@ -392,7 +392,7 @@ fn validate_attributes_v1(
     validate_timestamp(attributes, head_block)
 }
 
-fn validate_attributes_v2(
+pub(crate) fn validate_attributes_v2(
     attributes: &PayloadAttributesV3,
     head_block: &BlockHeader,
 ) -> Result<(), RpcErr> {
@@ -402,7 +402,7 @@ fn validate_attributes_v2(
     validate_timestamp(attributes, head_block)
 }
 
-fn validate_attributes_v2_pre_shanghai(
+pub(crate) fn validate_attributes_v2_pre_shanghai(
     attributes: &PayloadAttributesV3,
     head_block: &BlockHeader,
 ) -> Result<(), RpcErr> {
@@ -412,7 +412,7 @@ fn validate_attributes_v2_pre_shanghai(
     validate_timestamp(attributes, head_block)
 }
 
-fn validate_attributes_v3(
+pub(crate) fn validate_attributes_v3(
     attributes: &PayloadAttributesV3,
     head_block: &BlockHeader,
     context: &RpcApiContext,
@@ -448,7 +448,7 @@ fn validate_timestamp(
     Ok(())
 }
 
-async fn build_payload(
+pub(crate) async fn build_payload(
     attributes: &PayloadAttributesV3,
     context: RpcApiContext,
     fork_choice_state: &ForkChoiceState,
@@ -465,6 +465,7 @@ async fn build_payload(
         version,
         elasticity_multiplier: ELASTICITY_MULTIPLIER,
         gas_ceil: context.gas_ceil,
+        target_gas_limit: None,
     };
     let payload_id = args
         .id()
@@ -514,7 +515,7 @@ fn parse_v4(
     Ok((forkchoice_state, payload_attributes))
 }
 
-fn validate_attributes_v4(
+pub(crate) fn validate_attributes_v4(
     attributes: &PayloadAttributesV4,
     head_block: &BlockHeader,
     context: &RpcApiContext,
@@ -551,7 +552,7 @@ fn validate_timestamp_v4(
     Ok(())
 }
 
-async fn build_payload_v4(
+pub(crate) async fn build_payload_v4(
     attributes: &PayloadAttributesV4,
     context: RpcApiContext,
     fork_choice_state: &ForkChoiceState,
@@ -567,6 +568,9 @@ async fn build_payload_v4(
         version: 4,
         elasticity_multiplier: ELASTICITY_MULTIPLIER,
         gas_ceil: context.gas_ceil,
+        // Collapse the EIP-7783 0-sentinel to `None`; see the field doc on
+        // `PayloadAttributesV4::target_gas_limit`.
+        target_gas_limit: attributes.target_gas_limit.filter(|&v| v != 0),
     };
     let payload_id = args
         .id()

crates/networking/rpc/engine/mod.rs

@@ -66,6 +66,11 @@ impl RpcHandler for ExchangeCapabilitiesRequest {
     }
 
     async fn handle(&self, _context: RpcApiContext) -> Result<Value, RpcErr> {
-        Ok(json!(CAPABILITIES))
+        // Per execution-apis PR #764, advertise both JSON-RPC method names and
+        // the SSZ REST endpoint identifiers we support so the CL can pick the
+        // binary transport per endpoint.
+        let mut all: Vec<&str> = CAPABILITIES.to_vec();
+        all.extend_from_slice(crate::engine_rest::SSZ_REST_CAPABILITIES);
+        Ok(json!(all))
     }
 }