feat(levm): implement EIP7691 - Blob throughput increase (#1782)

**Motivation**

LEVM needs to support the changes introduced in
[EIP-7691](https://eips.ethereum.org/EIPS/eip-7691).

**Description**

This EIP introduces changes to some of the blob hashes' constants
values. With this PR, the values for blob hash calculations in LEVM will
depend on the spec being used.

Closes #1783
Closes #1776

crates/common/types/block.rs

@@ -340,7 +340,11 @@ fn check_gas_limit(gas_limit: u64, parent_gas_limit: u64) -> bool {
         && gas_limit >= GAS_LIMIT_MINIMUM
 }
 
-// Calculates the base fee per blob gas for the current block based on it's parent excess blob gas
+/// Calculates the base fee per blob gas for the current block based on
+/// it's parent excess blob gas.
+/// NOTE: BLOB_BASE_FEE_UPDATE_FRACTION has a different value after
+/// prague fork. See
+/// [EIP-7691](https://eips.ethereum.org/EIPS/eip-7691#specification).
 pub fn calculate_base_fee_per_blob_gas(parent_excess_blob_gas: u64) -> u64 {
     fake_exponential(
         MIN_BASE_FEE_PER_BLOB_GAS,

crates/vm/levm/README.md

@@ -6,7 +6,7 @@ Implementation of a simple Ethereum Virtual Machine in Rust.
 
 | Fork           | Status |
 | -------------- | ------ |
-| Prague         | 🏗️     |
+| Prague         | ✅️     |
 | Cancun         | ✅     |
 | Shanghai       | ✅     |
 | Paris (Merge)  | ✅     |
@@ -78,14 +78,16 @@ There are a lot of EIPs schedule to include in this upgrade but for `levm` we'll
 
 - EIP-2537: Precompile for BLS12-381 curve operations
 - EIP-7623: Increase calldata cost
+- EIP-7691: Blob throughput increase
 - EIP-7702: Set EOA account code
 
 | Task Description          | Status |
 | ------------------------- | ------ |
 | Implement EIP-2537        | ✅     |
 | Implement EIP-7623        | ✅     |
-| Implement EIP-7702        | ✅     |
-| Make Prague EF tests pass | ❌     |
+| Implement EIP-7691        | ✅️     |
+| Implement EIP-7702        | ✅️     |
+| Make Prague EF tests pass | ✅     |
 
 ### Milestone 5: Integrate `ethrex L2` <> `levm`
 

crates/vm/levm/src/constants.rs

@@ -43,13 +43,24 @@ pub mod create_opcode {
 }
 
 pub const VERSIONED_HASH_VERSION_KZG: u8 = 0x01;
-pub const MAX_BLOB_NUMBER_PER_BLOCK: usize = 6;
 
 // Blob constants
 pub const TARGET_BLOB_GAS_PER_BLOCK: U256 = U256([393216, 0, 0, 0]); // TARGET_BLOB_NUMBER_PER_BLOCK * GAS_PER_BLOB
+pub const TARGET_BLOB_GAS_PER_BLOCK_PECTRA: U256 = U256([786432, 0, 0, 0]); // TARGET_BLOB_NUMBER_PER_BLOCK * GAS_PER_BLOB
+
 pub const MIN_BASE_FEE_PER_BLOB_GAS: U256 = U256::one();
+
+// WARNING: Do _not_ use the BLOB_BASE_FEE_UPDATE_FRACTION_* family of
+// constants as is. Use the `get_blob_base_fee_update_fraction_value`
+// function instead
 pub const BLOB_BASE_FEE_UPDATE_FRACTION: U256 = U256([3338477, 0, 0, 0]);
+pub const BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE: U256 = U256([5007716, 0, 0, 0]); // Defined in [EIP-7691](https://eips.ethereum.org/EIPS/eip-7691)
+
+// WARNING: Do _not_ use the MAX_BLOB_COUNT_* family of constants as
+// is. Use the `max_blobs_per_block` function instead
 pub const MAX_BLOB_COUNT: usize = 6;
+pub const MAX_BLOB_COUNT_ELECTRA: usize = 9;
+
 pub const VALID_BLOB_PREFIXES: [u8; 2] = [0x01, 0x02];
 
 // Block constants

crates/vm/levm/src/vm.rs

@@ -741,7 +741,7 @@ impl VM {
         fake_exponential(
             MIN_BASE_FEE_PER_BLOB_GAS,
             self.env.block_excess_blob_gas.unwrap_or_default(),
-            BLOB_BASE_FEE_UPDATE_FRACTION,
+            get_blob_base_fee_update_fraction_value(self.env.spec_id),
         )
     }
 
@@ -934,7 +934,7 @@ impl VM {
             }
 
             // (14) TYPE_3_TX_BLOB_COUNT_EXCEEDED
-            if blob_hashes.len() > MAX_BLOB_COUNT {
+            if blob_hashes.len() > max_blobs_per_block(self.env.spec_id) {
                 return Err(VMError::TxValidation(
                     TxValidationError::Type3TxBlobCountExceeded,
                 ));
@@ -1684,3 +1684,29 @@ fn eip7702_recover_address(auth_tuple: &AuthorizationTuple) -> Result<Option<Add
         .map_err(|_| VMError::Internal(InternalError::ConversionError))?;
     Ok(Some(Address::from_slice(&authority_address_bytes)))
 }
+
+/// After EIP-7691 the maximum number of blob hashes changes. For more
+/// information see
+/// [EIP-7691](https://eips.ethereum.org/EIPS/eip-7691#specification).
+pub const fn max_blobs_per_block(specid: SpecId) -> usize {
+    match specid {
+        SpecId::PRAGUE => MAX_BLOB_COUNT_ELECTRA,
+        SpecId::PRAGUE_EOF => MAX_BLOB_COUNT_ELECTRA,
+        _ => MAX_BLOB_COUNT,
+    }
+}
+
+/// According to EIP-7691
+/// (https://eips.ethereum.org/EIPS/eip-7691#specification):
+///
+/// "These changes imply that get_base_fee_per_blob_gas and
+/// calc_excess_blob_gas functions defined in EIP-4844 use the new
+/// values for the first block of the fork (and for all subsequent
+/// blocks)."
+pub const fn get_blob_base_fee_update_fraction_value(specid: SpecId) -> U256 {
+    match specid {
+        SpecId::PRAGUE => BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE,
+        SpecId::PRAGUE_EOF => BLOB_BASE_FEE_UPDATE_FRACTION_PRAGUE,
+        _ => BLOB_BASE_FEE_UPDATE_FRACTION,
+    }
+}