Count PTC votes from duplicated validators

specs/gloas/beacon-chain.md

@@ -614,7 +614,7 @@ def compute_balance_weighted_selection(
     Return ``size`` indices sampled by effective balance, using ``indices``
     as candidates. If ``shuffle_indices`` is ``True``, candidate indices
     are themselves sampled from ``indices`` by shuffling it, otherwise
-    ``indices`` is traversed in order.
+    ``indices`` is traversed in order. The returned list can contain duplicates.
     """
     MAX_RANDOM_VALUE = 2**16 - 1
     total = uint64(len(indices))
@@ -665,7 +665,7 @@ def compute_proposer_indices(
 ```python
 def compute_ptc(state: BeaconState, slot: Slot) -> Vector[ValidatorIndex, PTC_SIZE]:
     """
-    Get the payload timeliness committee for the given ``slot``.
+    Get the payload timeliness committee, with possible duplicates, for the given ``slot``.
     """
     epoch = compute_epoch_at_slot(slot)
     seed = hash(get_seed(state, epoch, DOMAIN_PTC_ATTESTER) + uint_to_bytes(slot))

specs/gloas/fork-choice.md

@@ -937,17 +937,25 @@ def on_payload_attestation_message(
     Run ``on_payload_attestation_message`` upon receiving a new ``ptc_message`` from
     either within a block or directly on the wire.
     """
-    # The beacon block root must be known
     data = ptc_message.data
+
     # PTC attestation must be for a known block. If block is unknown, delay consideration until the block is found
     assert data.beacon_block_root in store.block_states
     state = store.block_states[data.beacon_block_root]
-    ptc = get_ptc(state, data.slot)
+
     # PTC votes can only change the vote for their assigned beacon block, return early otherwise
     if data.slot != state.slot:
         return
+
+    # Get all positions of the attester in the PTC
+    ptc_indices = []
+    ptc = get_ptc(state, data.slot)
+    for ptc_index, validator_index in enumerate(ptc):
+        if validator_index == ptc_message.validator_index:
+            ptc_indices.append(ptc_index)
+
     # Check that the attester is from the PTC
-    assert ptc_message.validator_index in ptc
+    assert len(ptc_indices) > 0
 
     # Verify the signature and check that its for the current slot if it is coming from the wire
     if not is_from_block:
@@ -962,10 +970,11 @@ def on_payload_attestation_message(
                 signature=ptc_message.signature,
             ),
         )
+
     # Update the votes for the block
-    ptc_index = ptc.index(ptc_message.validator_index)
     payload_timeliness_vote = store.payload_timeliness_vote[data.beacon_block_root]
-    payload_timeliness_vote[ptc_index] = data.payload_present
     payload_data_availability_vote = store.payload_data_availability_vote[data.beacon_block_root]
-    payload_data_availability_vote[ptc_index] = data.blob_data_available
+    for ptc_index in ptc_indices:
+        payload_timeliness_vote[ptc_index] = data.payload_present
+        payload_data_availability_vote[ptc_index] = data.blob_data_available
 ```