Add checkpoint root to proposer preferences

specs/gloas/builder.md

@@ -120,11 +120,15 @@ to include. They produce a `SignedExecutionPayloadBid` as follows.
 05. Set `bid.prev_randao` to be the previous RANDAO of the constructed payload,
     that is `payload.prev_randao`.
 06. Set `bid.fee_recipient` to be an execution address to receive the payment.
-    The proposer's preferred fee recipient can be obtained from the
-    `SignedProposerPreferences` associated with `bid.slot`.
-07. Set `bid.gas_limit` to be the gas limit of the constructed payload. The
-    proposer's preferred gas limit can be obtained from the
-    `SignedProposerPreferences` associated with `bid.slot`.
+    The proposer's preferred fee recipient is obtained from the
+    `SignedProposerPreferences` whose `message.proposal_slot == bid.slot` and
+    whose `message.checkpoint_root` equals
+    `get_checkpoint_block(store, bid.parent_block_root, compute_epoch_at_slot(bid.slot) - 1)`.
+    Builders that cannot find a matching `SignedProposerPreferences` MUST NOT
+    broadcast the bid.
+07. Set `bid.gas_limit` to be the gas limit of the constructed payload, which
+    must match the `gas_limit` in the same `SignedProposerPreferences`
+    referenced in step 6.
 08. Set `bid.builder_index` to be the index of the builder performing these
     actions.
 09. Set `bid.slot` to be the slot for which this bid is aimed. This slot

specs/gloas/p2p-interface.md

@@ -108,12 +108,16 @@ class PartialDataColumnGroupID(Container):
 
 ```python
 class ProposerPreferences(Container):
+    checkpoint_root: Root
     proposal_slot: Slot
     validator_index: ValidatorIndex
     fee_recipient: ExecutionAddress
     gas_limit: uint64
 ```
 
+The `checkpoint_root` is
+`get_checkpoint_block(store, head_root, compute_epoch_at_slot(proposal_slot) - 1)`.
+
 #### New `SignedProposerPreferences`
 
 *[New in Gloas:EIP7732]*
@@ -355,18 +359,19 @@ This topic is used to propagate signed bids as `SignedExecutionPayloadBid`.
 
 The following validations MUST pass before forwarding the
 `signed_execution_payload_bid` on the network, assuming the alias
-`bid = signed_execution_payload_bid.message`:
+`bid = signed_execution_payload_bid.message` and the alias
+`proposer_preferences` for the validated `SignedProposerPreferences` whose
+`message.proposal_slot == bid.slot` and
+`message.checkpoint_root == get_checkpoint_block(store, bid.parent_block_root, compute_epoch_at_slot(bid.slot) - 1)`:
 
 - _[IGNORE]_ `bid.slot` is the current slot or the next slot.
-- _[IGNORE]_ the `SignedProposerPreferences` where `preferences.proposal_slot`
-  is equal to `bid.slot` has been seen.
+- _[IGNORE]_ `proposer_preferences` is defined (i.e. a matching
+  `SignedProposerPreferences` has been seen).
 - _[REJECT]_ `bid.builder_index` is a valid/active builder index -- i.e.
   `is_active_builder(state, bid.builder_index)` returns `True`.
 - _[REJECT]_ `bid.execution_payment` is zero.
-- _[REJECT]_ `bid.fee_recipient` matches the `fee_recipient` from the proposer's
-  `SignedProposerPreferences` associated with `bid.slot`.
-- _[REJECT]_ `bid.gas_limit` matches the `gas_limit` from the proposer's
-  `SignedProposerPreferences` associated with `bid.slot`.
+- _[REJECT]_ `bid.fee_recipient == proposer_preferences.message.fee_recipient`.
+- _[REJECT]_ `bid.gas_limit == proposer_preferences.message.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`.
@@ -403,33 +408,32 @@ The following validations MUST pass before forwarding the
 
 - _[IGNORE]_ `preferences.proposal_slot` is in the current or next epoch -- i.e.
   `compute_epoch_at_slot(preferences.proposal_slot)` is in
-  `[get_current_epoch(state), get_current_epoch(state) + 1]`.
+  `[compute_epoch_at_slot(current_slot), compute_epoch_at_slot(current_slot) + 1]`.
 - _[IGNORE]_ `preferences.proposal_slot` has not already passed -- i.e.
-  `preferences.proposal_slot > state.slot`.
-- _[IGNORE]_ `preferences.validator_index` is present at the correct slot in the
-  current or next epoch's portion of `state.proposer_lookahead` -- i.e.
-  `is_valid_proposal_slot(state, preferences)` returns `True`.
-- _[IGNORE]_ The `signed_proposer_preferences` is the first valid message
-  received from the validator with index `preferences.validator_index` and the
-  given slot `preferences.proposal_slot`.
+  `preferences.proposal_slot > current_slot`.
+- _[IGNORE]_ The block with root `preferences.checkpoint_root` is unknown to the
+  node. Implementations MAY queue the message for re-processing once the block
+  becomes known.
+- _[REJECT]_ `is_valid_proposal_slot(state, preferences)` returns `False`, where
+  `state` is the checkpoint state at
+  `(compute_epoch_at_slot(preferences.proposal_slot) - 1, preferences.checkpoint_root)`.
+- _[IGNORE]_ The `signed_proposer_preferences` is the first valid message seen
+  for the tuple
+  `(preferences.checkpoint_root, preferences.proposal_slot, preferences.validator_index)`.
 - _[REJECT]_ `signed_proposer_preferences.signature` is valid with respect to
   the validator's public key.
 
 ```python
 def is_valid_proposal_slot(state: BeaconState, preferences: ProposerPreferences) -> bool:
     """
-    Check if the validator is the proposer for the given slot in the current or
-    next epoch.
+    Check if the validator is the proposer for the given slot using the
+    checkpoint ``state`` identified by ``preferences.checkpoint_root``.
     """
-    current_epoch = get_current_epoch(state)
     proposal_epoch = compute_epoch_at_slot(preferences.proposal_slot)
-    if proposal_epoch < current_epoch:
-        return False
-    if proposal_epoch > current_epoch + Epoch(1):
+    if get_current_epoch(state) != proposal_epoch - Epoch(1):
         return False
 
-    index = (proposal_epoch - current_epoch) * SLOTS_PER_EPOCH
-    index += preferences.proposal_slot % SLOTS_PER_EPOCH
+    index = SLOTS_PER_EPOCH + preferences.proposal_slot % SLOTS_PER_EPOCH
     return state.proposer_lookahead[index] == preferences.validator_index
 ```
 

specs/gloas/validator.md

@@ -153,15 +153,18 @@ def get_upcoming_proposal_slots(
 To construct each `SignedProposerPreferences`:
 
 1. Instantiate a new `ProposerPreferences` object as `preferences`.
-2. Set `preferences.proposal_slot` to `upcoming_proposal_slots[i]`.
-3. Set `preferences.validator_index` to the validator's index.
-4. Set `preferences.fee_recipient` to the execution address where the validator
+2. Set `preferences.checkpoint_root` to
+   `get_checkpoint_block(store, head_root, compute_epoch_at_slot(preferences.proposal_slot) - 1)`,
+   where `head_root` is the proposer's current head.
+3. Set `preferences.proposal_slot` to `upcoming_proposal_slots[i]`.
+4. Set `preferences.validator_index` to the validator's index.
+5. Set `preferences.fee_recipient` to the execution address where the validator
    wishes to receive the builder payment.
-5. Set `preferences.gas_limit` to the validator's preferred gas limit for this
+6. Set `preferences.gas_limit` to the validator's preferred gas limit for this
    execution payload.
-6. Instantiate a new `SignedProposerPreferences` object as `signed_preferences`.
-7. Set `signed_preferences.message` to `preferences`.
-8. Set `signed_preferences.signature` to the result of
+7. Instantiate a new `SignedProposerPreferences` object as `signed_preferences`.
+8. Set `signed_preferences.message` to `preferences`.
+9. Set `signed_preferences.signature` to the result of
    `get_proposer_preferences_signature(state, preferences, privkey)`.
 
 ```python