Check gas limit consistency with the target #5236

nflaig · 2026-06-29T17:04:00Z

just realized this but shouldn't this be a REJECT if is_gas_limit_target_compatible = False? we do the same if fee recipient is incorrect, wondering if we used IGNORE just because it's combined with "known execution payload in fork choice" condition

Yes, I think it should. Can you open a PR for this?

Reject instead of ignore incompatible gas limit bids #5428

michaelsproul · 2026-05-20T04:48:55Z

Don't we have to worry about overflow here? What if parent_gas_limit is really small (or 0, as we encountered at default Gloas genesis).

Actually nvm, it's fine because of how max_gas_limit_difference is calculated (parent_gas_limit <= 1024 implies max_gas_limit_difference == 0).

-Original file line number
+Diff line change
@@ Expand Up @@
         `get_proposer_dependent_root(parent_state, compute_epoch_at_slot(bid.slot))`,
         where `parent_state` is the post-state of `bid.parent_block_root`.
 . Set `bid.gas_limit` to be the gas limit of the constructed payload, which
-        must match the `gas_limit` in the `SignedProposerPreferences` referenced in
-        step 6.
+        **MUST** satisfy
+        `is_gas_limit_target_compatible(parent_gas_limit, bid.gas_limit, target_gas_limit)`,
+        where `parent_gas_limit` is the `gas_limit` of the parent execution payload
+        and `target_gas_limit` is the `target_gas_limit` in the
+        `SignedProposerPreferences` referenced in step 6.
 . Set `bid.builder_index` to be the index of the builder performing these
         actions.
 . Set `bid.slot` to be the slot for which this bid is aimed. This slot
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -182,6 +182,7 @@ def upgrade_to_gloas(pre: fulu.BeaconState) -> BeaconState: @@
             # [New in Gloas:EIP7732]
             latest_execution_payload_bid=ExecutionPayloadBid(
                 block_hash=pre.latest_execution_payload_header.block_hash,
+                gas_limit=pre.latest_execution_payload_header.gas_limit,
                 execution_requests_root=hash_tree_root(ExecutionRequests()),
             ),
             # [New in Gloas:EIP7732]
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up / @@ -90,7 +90,7 @@ class ProposerPreferences(Container): @@
         proposal_slot: Slot
         validator_index: ValidatorIndex
         fee_recipient: ExecutionAddress
-        gas_limit: uint64
+        target_gas_limit: uint64
     ```
     #### New `SignedProposerPreferences`
@@ Expand Down Expand Up @@
       `is_active_builder(state, bid.builder_index)` returns `True`.
     - _[REJECT]_ `bid.execution_payment == 0`.
     - _[REJECT]_ `bid.fee_recipient == proposer_preferences.fee_recipient`.
-    - _[REJECT]_ `bid.gas_limit == proposer_preferences.gas_limit`.
     - _[REJECT]_ The length of KZG commitments is less than or equal to the
       limitation defined in the consensus layer -- i.e. validate that
       `len(bid.blob_kzg_commitments) <= get_blob_parameters(compute_epoch_at_slot(bid.slot)).max_blobs_per_block`.
@@ Expand All @@
     - _[IGNORE]_ `bid.value` is less or equal than the builder's excess balance --
       i.e. `can_builder_cover_bid(state, builder_index, amount)` returns `True`.
     - _[IGNORE]_ `bid.parent_block_hash` is the block hash of a known execution
-      payload in fork choice.
+      payload in fork choice and
+      `is_gas_limit_target_compatible(parent_gas_limit, bid.gas_limit, proposer_preferences.target_gas_limit)`
+      is `True` where `parent_gas_limit` is the `gas_limit` of that execution
+      payload.
     - _[IGNORE]_ `bid.parent_block_root` is the hash tree root of a known beacon
       block in fork choice.
     - _[REJECT]_ `signed_execution_payload_bid.signature` is valid with respect to
       the `bid.builder_index`.
+    ```python
+    def is_gas_limit_target_compatible(
+        parent_gas_limit: uint64, gas_limit: uint64, target_gas_limit: uint64
+    ) -> bool:
+        """
+        Check if ``gas_limit`` is compatible with ``target_gas_limit`` under the
+        EIP-1559 transition rule from ``parent_gas_limit``.
+        """
+        max_gas_limit_difference = max(parent_gas_limit // 1024, 1) - 1
+        min_gas_limit = parent_gas_limit - max_gas_limit_difference
+        max_gas_limit = parent_gas_limit + max_gas_limit_difference
+        if target_gas_limit >= min_gas_limit and target_gas_limit <= max_gas_limit:
+            return gas_limit == target_gas_limit
+        if target_gas_limit > max_gas_limit:
+            return gas_limit == max_gas_limit
+        return gas_limit == min_gas_limit
+    ```
     *Note*: Implementations SHOULD include DoS prevention measures to mitigate spam
     from malicious builders submitting numerous bids with minimal value increments.
     Possible strategies include: (1) only forwarding bids that exceed the current
@@ Expand All / @@ -376,7 +397,7 @@ bid at regular time intervals. @@
     This topic is used to propagate signed proposer preferences as
     `SignedProposerPreferences`. These messages allow validators to communicate
-    their preferred `fee_recipient` and `gas_limit` to builders.
+    their preferred `fee_recipient` and `target_gas_limit` to builders.
     The following validations MUST pass before forwarding the
     `signed_proposer_preferences` on the network, assuming the alias
@@ Expand Down @@

-Original file line number
+Diff line change
@@ Expand Up @@
     `get_upcoming_proposal_slots(state, validator_index)`. These include any future
     proposal slots within the proposer lookahead, i.e. the current epoch up to
     `MIN_SEED_LOOKAHEAD` epochs ahead. This allows builders to construct execution
-    payloads with the validator's preferred `fee_recipient` and `gas_limit`. If a
-    validator does not broadcast a `SignedProposerPreferences` message, this implies
-    that the validator will not accept any trustless bids for that slot.
+    payloads with the validator's preferred `fee_recipient` and `target_gas_limit`.
+    If a validator does not broadcast a `SignedProposerPreferences` message, this
+    implies that the validator will not accept any trustless bids for that slot.
     ```python
     def get_upcoming_proposal_slots(
@@ Expand Down Expand Up / @@ -162,8 +162,8 @@ To construct each `SignedProposerPreferences`: @@
 . Set `preferences.validator_index` to the validator's index.
 . Set `preferences.fee_recipient` to the execution address where the validator
        wishes to receive the builder payment.
-. Set `preferences.gas_limit` to the validator's preferred gas limit for this
-       execution payload.
+. Set `preferences.target_gas_limit` to the validator's preferred gas limit for
+       this execution payload.
 . Instantiate a new `SignedProposerPreferences` object as `signed_preferences`.
 . Set `signed_preferences.message` to `preferences`.
 . Set `signed_preferences.signature` to the result of
@@ Expand Down @@

-Original file line number
+Diff line change
@@ -0,0 +1,58 @@
+    from eth_consensus_specs.test.context import (
+        single_phase,
+        spec_test,
+        with_gloas_and_later,
+    )
+    @with_gloas_and_later
+    @spec_test
+    @single_phase
+    def test_increase_within_limit(spec):
+        assert spec.is_gas_limit_target_compatible(60_000_000, 60_000_100, 60_000_100)
+    @with_gloas_and_later
+    @spec_test
+    @single_phase
+    def test_increase_exceeding_limit(spec):
+        # max_gas_limit_difference = 60_000_000 // 1024 - 1 = 58_592
+        assert spec.is_gas_limit_target_compatible(60_000_000, 60_058_592, 100_000_000)
+    @with_gloas_and_later
+    @spec_test
+    @single_phase
+    def test_increase_exceeding_limit_off_by_one_fails(spec):
+        # gas_limit one above max_gas_limit (= 60_058_592) must fail (off by one)
+        assert not spec.is_gas_limit_target_compatible(60_000_000, 60_058_593, 100_000_000)
+    @with_gloas_and_later
+    @spec_test
+    @single_phase
+    def test_decrease_within_limit(spec):
+        assert spec.is_gas_limit_target_compatible(60_000_000, 59_999_990, 59_999_990)
+    @with_gloas_and_later
+    @spec_test
+    @single_phase
+    def test_decrease_exceeding_limit(spec):
+        # max_gas_limit_difference = 60_000_000 // 1024 - 1 = 58_592
+        assert spec.is_gas_limit_target_compatible(60_000_000, 59_941_408, 30_000_000)
+    @with_gloas_and_later
+    @spec_test
+    @single_phase
+    def test_target_equals_parent(spec):
+        assert spec.is_gas_limit_target_compatible(60_000_000, 60_000_000, 60_000_000)
+    @with_gloas_and_later
+    @spec_test
+    @single_phase
+    def test_parent_gas_limit_underflows(spec):
+        # parent_gas_limit // 1024 = 0; guard clamps to max(0, 1) - 1 = 0 (no underflow)
+        assert spec.is_gas_limit_target_compatible(1023, 1023, 60_000_000)

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