feat(holocene): Simplify eip1559Params (#404)

* chore(holocene): Simplify `eip1559Params`

* lint

* add section on header extension

* toc

* change attrs validity rules

* fork activation rule

* toc

* change from QUANTITY -> DATA

* update types

* review

* toc

specs/SUMMARY.md

@@ -54,7 +54,6 @@
       - [Derivation](./protocol/holocene/derivation.md)
       - [Execution Engine](./protocol/holocene/exec-engine.md)
       - [Predeploys](./protocol/holocene/predeploys.md)
-      - [L1 Block Attributes](./protocol/holocene/l1-attributes.md)
       - [Configurability](./protocol/holocene/configurability.md)
 - [Governance]()
   - [Governance Token](./governance/gov-token.md)

specs/protocol/holocene/configurability.md

@@ -14,6 +14,8 @@
   - [Interface](#interface)
     - [EIP-1559 Params](#eip-1559-params)
       - [`setEIP1559Params`](#seteip1559params)
+      - [`eip1559Elasticity`](#eip1559elasticity)
+      - [`eip1559Denominator`](#eip1559denominator)
     - [Fee Vault Config](#fee-vault-config)
       - [`setBaseFeeVaultConfig`](#setbasefeevaultconfig)
       - [`setL1FeeVaultConfig`](#setl1feevaultconfig)
@@ -50,15 +52,15 @@ The `ConfigType` enum represents configuration that can be modified.
 
 ### `ConfigUpdate`
 
-The following `ConfigUpdate` enum is defined where the `CONFIG_VERSION` is `uint256(0)`:
+The following `ConfigUpdate` event is defined where the `CONFIG_VERSION` is `uint256(0)`:
 
 | Name | Value | Definition | Usage |
 | ---- | ----- | --- | -- |
 | `BATCHER` | `uint8(0)` | `abi.encode(address)` | Modifies the account that is authorized to progress the safe chain |
 | `FEE_SCALARS` | `uint8(1)` | `(uint256(0x01) << 248) \| (uint256(_blobbasefeeScalar) << 32) \| _basefeeScalar` | Modifies the fee scalars |
 | `GAS_LIMIT` | `uint8(2)` | `abi.encode(uint64 _gasLimit)` | Modifies the L2 gas limit |
 | `UNSAFE_BLOCK_SIGNER` | `uint8(3)` | `abi.encode(address)` | Modifies the account that is authorized to progress the unsafe chain |
-| `EIP_1559_PARAMS` | `uint8(4)` | `uint256(uint64(_denominator)) << 32 \| uint64(_elasticity)` | Modifies the EIP-1559 denominator and elasticity |
+| `EIP_1559_PARAMS` | `uint8(4)` | `uint256(uint64(uint32(_denominator))) << 32 \| uint64(uint32(_elasticity))` | Modifies the EIP-1559 denominator and elasticity |
 
 ### Initialization
 
@@ -95,12 +97,28 @@ operator to modify the `BASE_FEE_MAX_CHANGE_DENOMINATOR` and the `ELASTICITY_MUL
 This function MUST only be callable by the chain governor.
 
 ```solidity
-function setEIP1559Params(uint64 _denominator, uint64 _elasticity)
+function setEIP1559Params(uint32 _denominator, uint32 _elasticity)
 ```
 
 The `_denominator` and `_elasticity` MUST be set to values greater to than 0.
 It is possible for the chain operator to set EIP-1559 parameters that result in poor user experience.
 
+##### `eip1559Elasticity`
+
+This function returns the currently configured EIP-1559 elasticity.
+
+```solidity
+function eip1559Elasticity()(uint64)
+```
+
+##### `eip1559Denominator`
+
+This function returns the currently configured EIP-1559 denominator.
+
+```solidity
+function eip1559Denominator()(uint64)
+```
+
 #### Fee Vault Config
 
 For each `FeeVault`, there is a setter for its config. The arguments to the setter include

specs/protocol/holocene/derivation.md

@@ -15,6 +15,7 @@
   - [Batch Queue](#batch-queue)
     - [Fast Channel Invalidation](#fast-channel-invalidation)
   - [Engine Queue](#engine-queue)
+  - [Attributes Builder](#attributes-builder)
   - [Activation](#activation)
 - [Rationale](#rationale)
   - [Strict Frame and Batch Ordering](#strict-frame-and-batch-ordering)
@@ -177,6 +178,19 @@ As before, a failure to then process the deposit-only attributes is a critical e
 If an invalid payload is replaced by a deposit-only payload, for consistency reasons, the remaining
 span batch, if applicable, and channel it originated from are dropped as well.
 
+## Attributes Builder
+
+Starting after the fork activation block, the `PayloadAttributes` produced by the attributes builder will include
+the `eip1559Params` field described in the [execution engine specs](./exec-engine.md#eip1559params-encoding). This
+value exists within the `SystemConfig`.
+
+On the fork activation block, the attributes builder will include a 0'd out `eip1559Params`, as to instruct
+the engine to use the [canyon base fee parameter constants](../exec-engine.md#1559-parameters). This
+is to prime the pipeline's view of the `SystemConfig` with the default EIP-1559 parameter values. After the first
+Holocene payload has been processed, future payloads should use the `SystemConfig`'s EIP-1559 denominator and elasticity
+parameter as the `eip1559Params` field's value. When the pipeline encounters a `UpdateType.EIP_1559_PARAMS`,
+`ConfigUpdate` event, the pipeline's system config will be synchronized with the `SystemConfig` contract's.
+
 ## Activation
 
 The new batch rules activate when the _L1 inclusion block timestamp_ is greater or equal to the

specs/protocol/holocene/exec-engine.md

@@ -4,30 +4,36 @@
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
 **Table of Contents**
 
+- [Timestamp Activation](#timestamp-activation)
 - [`L2ToL1MessagePasser` Storage Root in Header](#l2tol1messagepasser-storage-root-in-header)
-  - [Timestamp Activation](#timestamp-activation)
   - [Header Validity Rules](#header-validity-rules)
   - [Header Withdrawals Root](#header-withdrawals-root)
     - [Rationale](#rationale)
     - [Forwards Compatibility Considerations](#forwards-compatibility-considerations)
     - [Client Implementation Considerations](#client-implementation-considerations)
+- [Extended `PayloadAttributesV3`](#extended-payloadattributesv3)
+  - [`eip1559Params` encoding](#eip1559params-encoding)
+  - [Execution](#execution)
+  - [Rationale](#rationale-1)
+- [`eip1559Params` in Header](#eip1559params-in-header)
+  - [Header Validity Rules](#header-validity-rules-1)
+  - [Encoding](#encoding)
+  - [Rationale](#rationale-2)
 
 <!-- END doctoc generated TOC please keep comment here to allow auto update -->
 
+## Timestamp Activation
+
+Holocene, like other network upgrades, is activated at a timestamp.
+Changes to the L2 Block execution rules are applied when the `L2 Timestamp >= activation time`.
+
 ## `L2ToL1MessagePasser` Storage Root in Header
 
-After the Holocene hardfork's activation, the L2 block header's `withdrawalsRoot` field will consist of the 32-byte
+After Holocene's activation, the L2 block header's `withdrawalsRoot` field will consist of the 32-byte
 [`L2ToL1MessagePasser`][l2-to-l1-mp] account storage root _after_ the block has been executed, and _after_ the
 insertions and deletions have been applied to the trie. In other words, the storage root should be the same root
 that is returned by `eth_getProof` at the given block number.
 
-### Timestamp Activation
-
-Holocene, like other network upgrades, is activated at a timestamp.
-Changes to the L2 Block execution rules are applied when the `L2 Timestamp >= activation time`.
-Changes to the L2 block header are applied when it is considering data from a L1 Block whose timestamp
-is greater than or equal to the activation timestamp.
-
 ### Header Validity Rules
 
 Prior to holocene activation, the L2 block header's `withdrawalsRoot` field must be:
@@ -73,5 +79,73 @@ an outbound withdrawal for a long period of time, the node may not have access t
 clients are able to at the very least reconstruct the account storage root at a given block on the fly if it does not
 directly store this information.
 
+## Extended `PayloadAttributesV3`
+
+The [`PayloadAttributesV3`](https://github.com/ethereum/execution-apis/blob/cea7eeb642052f4c2e03449dc48296def4aafc24/src/engine/cancun.md#payloadattributesv3)
+type is extended to:
+
+```rs
+PayloadAttributesV3: {
+    timestamp: QUANTITY
+    random: DATA (32 bytes)
+    suggestedFeeRecipient: DATA (20 bytes)
+    withdrawals: array of WithdrawalV1
+    parentBeaconBlockRoot: DATA (32 bytes)
+    transactions: array of DATA
+    noTxPool: bool
+    gasLimit: QUANTITY or null
+    eip1559Params: DATA (8 bytes)
+}
+```
+
+### `eip1559Params` encoding
+
+| Name          | Type               | Byte Offset |
+| ------------- | ------------------ | ----------- |
+| `denominator` | `u32 (big-endian)` | `[0, 4)`    |
+| `elasticity`  | `u32 (big-endian)` | `[4, 8)`    |
+
+### Execution
+
+During execution, the EIP-1559 parameters used to calculate the next block base fee should come from the
+`PayloadAttributesV3` type rather than the previous protocol constants, if it is non-null.
+
+- If, before Holocene activation, `eip1559Parameters` is non-zero, the attributes are to be considered invalid by the
+  engine.
+- After Holocene activation:
+  - if `eip1559Params` is zero, the [canyon base fee parameter constants](../exec-engine.md#1559-parameters) are
+    used.
+  - if `eip1559Params` are non-null, the values from the attributes are used.
+
+### Rationale
+
+This type is made available in the payload attributes to allow the block builder to dynamically control the EIP-1559
+parameters of the chain. As described in the [derivation - AttributesBuilder](./derivation.md#attributes-builder)
+section, the derivation pipeline must populate this field from the `SystemConfig` during payload building, similar to
+how it must reference the `SystemConfig` for the `gasLimit` field.
+
+## `eip1559Params` in Header
+
+Upon Holocene activation, the L2 block header's `nonce` field will consist of the 8-byte `eip1559Params` value.
+
+### Header Validity Rules
+
+Prior to Holocene activation, the L2 block header's `nonce` field is valid iff it is equal to `u64(0)`.
+
+After Holocene activation, The L2 block header's `nonce` field is valid iff it is non-zero.
+
+### Encoding
+
+The encoding of the `eip1559Params` value is described in [`eip1559Params` encoding](#eip1559params-encoding).
+
+### Rationale
+
+By chosing to put the `eip1559Params` in the `PayloadAttributes` rather than in the L1 block info transaction,
+the EIP-1559 parameters for the chain are not available within history. This would place a burden on performing
+historical execution, as L1 would have to be consulted for fetching the values from the `SystemConfig` contract.
+Instead, we re-use an unused field in the L1 block header as to make these parameters available, retaining the
+purity of the function that computes the next block's base fee from the chain configuration, parent block header,
+and next block timestamp.
+
 [l2-to-l1-mp]: ../../protocol/predeploys.md#L2ToL1MessagePasser
 [output-root]: ../../glossary.md#l2-output-root

specs/protocol/holocene/overview.md

@@ -24,5 +24,4 @@ This document is not finalized and should be considered experimental.
 ## Smart Contracts
 
 - [Predeploys](./predeploys.md)
-- [L1 Block Attributes](./l1-attributes.md)
 - [Configurability](./configurability.md)

specs/protocol/holocene/predeploys.md

@@ -9,10 +9,7 @@
   - [L1Block](#l1block)
     - [Storage](#storage)
     - [Interface](#interface)
-      - [`setL1BlockValuesHolocene`](#setl1blockvaluesholocene)
       - [`setHolocene`](#setholocene)
-      - [`eip1559Elasticity`](#eip1559elasticity)
-      - [`eip1559Denominator`](#eip1559denominator)
       - [`setConfig`](#setconfig)
       - [`baseFeeVaultConfig`](#basefeevaultconfig)
       - [`sequencerFeeVaultConfig`](#sequencerfeevaultconfig)
@@ -101,37 +98,12 @@ via a deposit transaction from the `DEPOSITOR_ACCOUNT`.
 
 #### Interface
 
-##### `setL1BlockValuesHolocene`
-
-This function MUST only be callable by the `DEPOSITOR_ACCOUNT`. It is a replacement
-for `setL1BlockValuesEcotone` and its calldata is defined in [L1 Attributes](./l1-attributes.md).
-
-```function
-function setL1BlockValuesHolocene()
-```
-
 ##### `setHolocene`
 
 This function is meant to be called once on the activation block of the holocene network upgrade.
 It MUST only be callable by the `DEPOSITOR_ACCOUNT` once. When it is called, it MUST call
 call each getter for the network specific config and set the returndata into storage.
 
-##### `eip1559Elasticity`
-
-This function returns the currently configured EIP-1559 elasticity.
-
-```solidity
-function eip1559Elasticity()(uint64)
-```
-
-##### `eip1559Denominator`
-
-This function returns the currently configured EIP-1559 denominator.
-
-```solidity
-function eip1559Denominator()(uint64)
-```
-
 ##### `setConfig`
 
 This function MUST only be callable by the `DEPOSITOR_ACCOUNT`. It modifies the storage directly