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Add LightClientHeader wrapper

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In Altair, light client sync protocol exchanges `BeaconBlockHeader`
structures for tracking current progress. Wrapping `BeaconBlockHeader`
inside a `LightClientHeader` allows future extensions of this header,
e.g., to also track `ExecutionPayloadHeader`.

Note: This changes the JSON REST format by adding a `beacon` nesting.
For SSZ, the serialization format stays same (but overall root changes).
This commit is contained in:
Etan Kissling 2023-01-05 13:36:04 +01:00
parent 19cf15b838
commit 5c64a2047a
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8 changed files with 128 additions and 115 deletions
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26
specs/altair/light-client/full-node.md
View File

@ -38,13 +38,15 @@ def compute_merkle_proof_for_state(state: BeaconState,
### `block_to_light_client_header`
```python
def block_to_light_client_header(block: SignedBeaconBlock) -> BeaconBlockHeader:
return BeaconBlockHeader(
slot=block.message.slot,
proposer_index=block.message.proposer_index,
parent_root=block.message.parent_root,
state_root=block.message.state_root,
body_root=hash_tree_root(block.message.body),
def block_to_light_client_header(block: SignedBeaconBlock) -> LightClientHeader:
return LightClientHeader(
beacon=BeaconBlockHeader(
slot=block.message.slot,
proposer_index=block.message.proposer_index,
parent_root=block.message.parent_root,
state_root=block.message.state_root,
body_root=hash_tree_root(block.message.body),
),
)
```
@ -125,7 +127,7 @@ def create_light_client_update(state: BeaconState,
if finalized_block is not None:
if finalized_block.message.slot != GENESIS_SLOT:
update.finalized_header = block_to_light_client_header(finalized_block)
assert hash_tree_root(update.finalized_header) == attested_state.finalized_checkpoint.root
assert hash_tree_root(update.finalized_header.beacon) == attested_state.finalized_checkpoint.root
else:
assert attested_state.finalized_checkpoint.root == Bytes32()
update.finality_branch = compute_merkle_proof_for_state(
@ -139,8 +141,8 @@ def create_light_client_update(state: BeaconState,
Full nodes SHOULD provide the best derivable `LightClientUpdate` (according to `is_better_update`) for each sync committee period covering any epochs in range `[max(ALTAIR_FORK_EPOCH, current_epoch - MIN_EPOCHS_FOR_BLOCK_REQUESTS), current_epoch]` where `current_epoch` is defined by the current wall-clock time. Full nodes MAY also provide `LightClientUpdate` for other sync committee periods.
- `LightClientUpdate` are assigned to sync committee periods based on their `attested_header.slot`
- `LightClientUpdate` are only considered if `compute_sync_committee_period_at_slot(update.attested_header.slot) == compute_sync_committee_period_at_slot(update.signature_slot)`
- `LightClientUpdate` are assigned to sync committee periods based on their `attested_header.beacon.slot`
- `LightClientUpdate` are only considered if `compute_sync_committee_period_at_slot(update.attested_header.beacon.slot) == compute_sync_committee_period_at_slot(update.signature_slot)`
- Only `LightClientUpdate` with `next_sync_committee` as selected by fork choice are provided, regardless of ranking by `is_better_update`. To uniquely identify a non-finalized sync committee fork, all of `period`, `current_sync_committee` and `next_sync_committee` need to be incorporated, as sync committees may reappear over time.
### `create_light_client_finality_update`
@ -156,7 +158,7 @@ def create_light_client_finality_update(update: LightClientUpdate) -> LightClien
)
```
Full nodes SHOULD provide the `LightClientFinalityUpdate` with the highest `attested_header.slot` (if multiple, highest `signature_slot`) as selected by fork choice, and SHOULD support a push mechanism to deliver new `LightClientFinalityUpdate` whenever `finalized_header` changes.
Full nodes SHOULD provide the `LightClientFinalityUpdate` with the highest `attested_header.beacon.slot` (if multiple, highest `signature_slot`) as selected by fork choice, and SHOULD support a push mechanism to deliver new `LightClientFinalityUpdate` whenever `finalized_header` changes.
### `create_light_client_optimistic_update`
@ -169,4 +171,4 @@ def create_light_client_optimistic_update(update: LightClientUpdate) -> LightCli
)
```
Full nodes SHOULD provide the `LightClientOptimisticUpdate` with the highest `attested_header.slot` (if multiple, highest `signature_slot`) as selected by fork choice, and SHOULD support a push mechanism to deliver new `LightClientOptimisticUpdate` whenever `attested_header` changes.
Full nodes SHOULD provide the `LightClientOptimisticUpdate` with the highest `attested_header.beacon.slot` (if multiple, highest `signature_slot`) as selected by fork choice, and SHOULD support a push mechanism to deliver new `LightClientOptimisticUpdate` whenever `attested_header` changes.

2
specs/altair/light-client/light-client.md
View File

@ -23,7 +23,7 @@ This document explains how light clients MAY obtain light client data to sync wi
1. The light client MUST be configured out-of-band with a spec/preset (including fork schedule), with `genesis_state` (including `genesis_time` and `genesis_validators_root`), and with a trusted block root. The trusted block SHOULD be within the weak subjectivity period, and its root SHOULD be from a finalized `Checkpoint`.
2. The local clock is initialized based on the configured `genesis_time`, and the current fork digest is determined to browse for and connect to relevant light client data providers.
3. The light client fetches a [`LightClientBootstrap`](./sync-protocol.md#lightclientbootstrap) object for the configured trusted block root. The `bootstrap` object is passed to [`initialize_light_client_store`](./sync-protocol.md#initialize_light_client_store) to obtain a local [`LightClientStore`](./sync-protocol.md#lightclientstore).
4. The light client tracks the sync committee periods `finalized_period` from `store.finalized_header.slot`, `optimistic_period` from `store.optimistic_header.slot`, and `current_period` from `current_slot` based on the local clock.
4. The light client tracks the sync committee periods `finalized_period` from `store.finalized_header.beacon.slot`, `optimistic_period` from `store.optimistic_header.beacon.slot`, and `current_period` from `current_slot` based on the local clock.
1. When `finalized_period == optimistic_period` and [`is_next_sync_committee_known`](./sync-protocol.md#is_next_sync_committee_known) indicates `False`, the light client fetches a [`LightClientUpdate`](./sync-protocol.md#lightclientupdate) for `finalized_period`. If `finalized_period == current_period`, this fetch SHOULD be scheduled at a random time before `current_period` advances.
2. When `finalized_period + 1 < current_period`, the light client fetches a `LightClientUpdate` for each sync committee period in range `[finalized_period + 1, current_period)` (current period excluded)
3. When `finalized_period + 1 >= current_period`, the light client keeps observing [`LightClientFinalityUpdate`](./sync-protocol.md#lightclientfinalityupdate) and [`LightClientOptimisticUpdate`](./sync-protocol.md#lightclientoptimisticupdate). Received objects are passed to [`process_light_client_finality_update`](./sync-protocol.md#process_light_client_finality_update) and [`process_light_client_optimistic_update`](./sync-protocol.md#process_light_client_optimistic_update). This ensures that `finalized_header` and `optimistic_header` reflect the latest blocks.

24
specs/altair/light-client/p2p-interface.md
View File

@ -59,7 +59,7 @@ New global topics are added to provide light clients with the latest updates.
This topic is used to propagate the latest `LightClientFinalityUpdate` to light clients, allowing them to keep track of the latest `finalized_header`.
The following validations MUST pass before forwarding the `finality_update` on the network.
- _[IGNORE]_ The `finalized_header.slot` is greater than that of all previously forwarded `finality_update`s
- _[IGNORE]_ The `finalized_header.beacon.slot` is greater than that of all previously forwarded `finality_update`s
- _[IGNORE]_ The `finality_update` is received after the block at `signature_slot` was given enough time to propagate through the network -- i.e. validate that one-third of `finality_update.signature_slot` has transpired (`SECONDS_PER_SLOT / INTERVALS_PER_SLOT` seconds after the start of the slot, with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance)
For full nodes, the following validations MUST additionally pass before forwarding the `finality_update` on the network.
@ -67,11 +67,11 @@ For full nodes, the following validations MUST additionally pass before forwardi
For light clients, the following validations MUST additionally pass before forwarding the `finality_update` on the network.
- _[REJECT]_ The `finality_update` is valid -- i.e. validate that `process_light_client_finality_update` does not indicate errors
- _[IGNORE]_ The `finality_update` advances the `finalized_header` of the local `LightClientStore` -- i.e. validate that processing `finality_update` increases `store.finalized_header.slot`
- _[IGNORE]_ The `finality_update` advances the `finalized_header` of the local `LightClientStore` -- i.e. validate that processing `finality_update` increases `store.finalized_header.beacon.slot`
Light clients SHOULD call `process_light_client_finality_update` even if the message is ignored.
The gossip `ForkDigest`-context is determined based on `compute_fork_version(compute_epoch_at_slot(finality_update.attested_header.slot))`.
The gossip `ForkDigest`-context is determined based on `compute_fork_version(compute_epoch_at_slot(finality_update.attested_header.beacon.slot))`.
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
@ -87,7 +87,7 @@ Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
This topic is used to propagate the latest `LightClientOptimisticUpdate` to light clients, allowing them to keep track of the latest `optimistic_header`.
The following validations MUST pass before forwarding the `optimistic_update` on the network.
- _[IGNORE]_ The `attested_header.slot` is greater than that of all previously forwarded `optimistic_update`s
- _[IGNORE]_ The `attested_header.beacon.slot` is greater than that of all previously forwarded `optimistic_update`s
- _[IGNORE]_ The `optimistic_update` is received after the block at `signature_slot` was given enough time to propagate through the network -- i.e. validate that one-third of `optimistic_update.signature_slot` has transpired (`SECONDS_PER_SLOT / INTERVALS_PER_SLOT` seconds after the start of the slot, with a `MAXIMUM_GOSSIP_CLOCK_DISPARITY` allowance)
For full nodes, the following validations MUST additionally pass before forwarding the `optimistic_update` on the network.
@ -95,11 +95,11 @@ For full nodes, the following validations MUST additionally pass before forwardi
For light clients, the following validations MUST additionally pass before forwarding the `optimistic_update` on the network.
- _[REJECT]_ The `optimistic_update` is valid -- i.e. validate that `process_light_client_optimistic_update` does not indicate errors
- _[IGNORE]_ The `optimistic_update` either matches corresponding fields of the most recently forwarded `LightClientFinalityUpdate` (if any), or it advances the `optimistic_header` of the local `LightClientStore` -- i.e. validate that processing `optimistic_update` increases `store.optimistic_header.slot`
- _[IGNORE]_ The `optimistic_update` either matches corresponding fields of the most recently forwarded `LightClientFinalityUpdate` (if any), or it advances the `optimistic_header` of the local `LightClientStore` -- i.e. validate that processing `optimistic_update` increases `store.optimistic_header.beacon.slot`
Light clients SHOULD call `process_light_client_optimistic_update` even if the message is ignored.
The gossip `ForkDigest`-context is determined based on `compute_fork_version(compute_epoch_at_slot(optimistic_update.attested_header.slot))`.
The gossip `ForkDigest`-context is determined based on `compute_fork_version(compute_epoch_at_slot(optimistic_update.attested_header.beacon.slot))`.
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
@ -142,7 +142,7 @@ Peers SHOULD provide results as defined in [`create_light_client_bootstrap`](./f
When a `LightClientBootstrap` instance cannot be produced for a given block root, peers SHOULD respond with error code `3: ResourceUnavailable`.
A `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(bootstrap.header.slot))` is used to select the fork namespace of the Response type.
A `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(bootstrap.header.beacon.slot))` is used to select the fork namespace of the Response type.
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
@ -180,7 +180,7 @@ The response MUST consist of zero or more `response_chunk`. Each _successful_ `r
Peers SHOULD provide results as defined in [`create_light_client_update`](./full-node.md#create_light_client_update). They MUST respond with at least the earliest known result within the requested range, and MUST send results in consecutive order (by period). The response MUST NOT contain more than `min(MAX_REQUEST_LIGHT_CLIENT_UPDATES, count)` results.
For each `response_chunk`, a `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(update.attested_header.slot))` is used to select the fork namespace of the Response type. Note that this `fork_version` may be different from the one used to verify the `update.sync_aggregate`, which is based on `update.signature_slot`.
For each `response_chunk`, a `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(update.attested_header.beacon.slot))` is used to select the fork namespace of the Response type. Note that this `fork_version` may be different from the one used to verify the `update.sync_aggregate`, which is based on `update.signature_slot`.
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
@ -211,7 +211,7 @@ Peers SHOULD provide results as defined in [`create_light_client_finality_update
When no `LightClientFinalityUpdate` is available, peers SHOULD respond with error code `3: ResourceUnavailable`.
A `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(finality_update.attested_header.slot))` is used to select the fork namespace of the Response type. Note that this `fork_version` may be different from the one used to verify the `finality_update.sync_aggregate`, which is based on `finality_update.signature_slot`.
A `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(finality_update.attested_header.beacon.slot))` is used to select the fork namespace of the Response type. Note that this `fork_version` may be different from the one used to verify the `finality_update.sync_aggregate`, which is based on `finality_update.signature_slot`.
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
@ -242,7 +242,7 @@ Peers SHOULD provide results as defined in [`create_light_client_optimistic_upda
When no `LightClientOptimisticUpdate` is available, peers SHOULD respond with error code `3: ResourceUnavailable`.
A `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(optimistic_update.attested_header.slot))` is used to select the fork namespace of the Response type. Note that this `fork_version` may be different from the one used to verify the `optimistic_update.sync_aggregate`, which is based on `optimistic_update.signature_slot`.
A `ForkDigest`-context based on `compute_fork_version(compute_epoch_at_slot(optimistic_update.attested_header.beacon.slot))` is used to select the fork namespace of the Response type. Note that this `fork_version` may be different from the one used to verify the `optimistic_update.sync_aggregate`, which is based on `optimistic_update.signature_slot`.
Per `context = compute_fork_digest(fork_version, genesis_validators_root)`:
@ -273,7 +273,7 @@ All full nodes SHOULD subscribe to and provide stability on the [`light_client_f
Whenever fork choice selects a new head block with a sync aggregate participation `>= MIN_SYNC_COMMITTEE_PARTICIPANTS` and a post-Altair parent block, full nodes with at least one validator assigned to the current sync committee at the block's `slot` SHOULD broadcast derived light client data as follows:
- If `finalized_header.slot` increased, a `LightClientFinalityUpdate` SHOULD be broadcasted to the pubsub topic `light_client_finality_update` if no matching message has not yet been forwarded as part of gossip validation.
- If `attested_header.slot` increased, a `LightClientOptimisticUpdate` SHOULD be broadcasted to the pubsub topic `light_client_optimistic_update` if no matching message has not yet been forwarded as part of gossip validation.
- If `finalized_header.beacon.slot` increased, a `LightClientFinalityUpdate` SHOULD be broadcasted to the pubsub topic `light_client_finality_update` if no matching message has not yet been forwarded as part of gossip validation.
- If `attested_header.beacon.slot` increased, a `LightClientOptimisticUpdate` SHOULD be broadcasted to the pubsub topic `light_client_optimistic_update` if no matching message has not yet been forwarded as part of gossip validation.
These messages SHOULD be broadcasted after one-third of `slot` has transpired (`SECONDS_PER_SLOT / INTERVALS_PER_SLOT` seconds after the start of the slot). To ensure that the corresponding block was given enough time to propagate through the network, they SHOULD NOT be sent earlier. Note that this is different from how other messages are handled, e.g., attestations, which may be sent early.

101
specs/altair/light-client/sync-protocol.md
View File

@ -13,6 +13,7 @@
- [Preset](#preset)
- [Misc](#misc)
- [Containers](#containers)
- [`LightClientHeader`](#lightclientheader)
- [`LightClientBootstrap`](#lightclientbootstrap)
- [`LightClientUpdate`](#lightclientupdate)
- [`LightClientFinalityUpdate`](#lightclientfinalityupdate)
@ -73,13 +74,21 @@ Additional documents describe how the light client sync protocol can be used:
## Containers
### `LightClientHeader`
```python
class LightClientHeader(Container):
# Beacon block header
beacon: BeaconBlockHeader
```
### `LightClientBootstrap`
```python
class LightClientBootstrap(Container):
# Header matching the requested beacon block root
header: BeaconBlockHeader
# Current sync committee corresponding to `header.state_root`
header: LightClientHeader
# Current sync committee corresponding to `header.beacon.state_root`
current_sync_committee: SyncCommittee
current_sync_committee_branch: Vector[Bytes32, floorlog2(CURRENT_SYNC_COMMITTEE_INDEX)]
```
@ -89,12 +98,12 @@ class LightClientBootstrap(Container):
```python
class LightClientUpdate(Container):
# Header attested to by the sync committee
attested_header: BeaconBlockHeader
# Next sync committee corresponding to `attested_header.state_root`
attested_header: LightClientHeader
# Next sync committee corresponding to `attested_header.beacon.state_root`
next_sync_committee: SyncCommittee
next_sync_committee_branch: Vector[Bytes32, floorlog2(NEXT_SYNC_COMMITTEE_INDEX)]
# Finalized header corresponding to `attested_header.state_root`
finalized_header: BeaconBlockHeader
# Finalized header corresponding to `attested_header.beacon.state_root`
finalized_header: LightClientHeader
finality_branch: Vector[Bytes32, floorlog2(FINALIZED_ROOT_INDEX)]
# Sync committee aggregate signature
sync_aggregate: SyncAggregate
@ -107,9 +116,9 @@ class LightClientUpdate(Container):
```python
class LightClientFinalityUpdate(Container):
# Header attested to by the sync committee
attested_header: BeaconBlockHeader
# Finalized header corresponding to `attested_header.state_root`
finalized_header: BeaconBlockHeader
attested_header: LightClientHeader
# Finalized header corresponding to `attested_header.beacon.state_root`
finalized_header: LightClientHeader
finality_branch: Vector[Bytes32, floorlog2(FINALIZED_ROOT_INDEX)]
# Sync committee aggregate signature
sync_aggregate: SyncAggregate
@ -122,7 +131,7 @@ class LightClientFinalityUpdate(Container):
```python
class LightClientOptimisticUpdate(Container):
# Header attested to by the sync committee
attested_header: BeaconBlockHeader
attested_header: LightClientHeader
# Sync committee aggregate signature
sync_aggregate: SyncAggregate
# Slot at which the aggregate signature was created (untrusted)
@ -135,14 +144,14 @@ class LightClientOptimisticUpdate(Container):
@dataclass
class LightClientStore(object):
# Header that is finalized
finalized_header: BeaconBlockHeader
finalized_header: LightClientHeader
# Sync committees corresponding to the finalized header
current_sync_committee: SyncCommittee
next_sync_committee: SyncCommittee
# Best available header to switch finalized head to if we see nothing else
best_valid_update: Optional[LightClientUpdate]
# Most recent available reasonably-safe header
optimistic_header: BeaconBlockHeader
optimistic_header: LightClientHeader
# Max number of active participants in a sync committee (used to calculate safety threshold)
previous_max_active_participants: uint64
current_max_active_participants: uint64
@ -181,11 +190,11 @@ def is_better_update(new_update: LightClientUpdate, old_update: LightClientUpdat
# Compare presence of relevant sync committee
new_has_relevant_sync_committee = is_sync_committee_update(new_update) and (
compute_sync_committee_period_at_slot(new_update.attested_header.slot)
compute_sync_committee_period_at_slot(new_update.attested_header.beacon.slot)
== compute_sync_committee_period_at_slot(new_update.signature_slot)
)
old_has_relevant_sync_committee = is_sync_committee_update(old_update) and (
compute_sync_committee_period_at_slot(old_update.attested_header.slot)
compute_sync_committee_period_at_slot(old_update.attested_header.beacon.slot)
== compute_sync_committee_period_at_slot(old_update.signature_slot)
)
if new_has_relevant_sync_committee != old_has_relevant_sync_committee:
@ -200,12 +209,12 @@ def is_better_update(new_update: LightClientUpdate, old_update: LightClientUpdat
# Compare sync committee finality
if new_has_finality:
new_has_sync_committee_finality = (
compute_sync_committee_period_at_slot(new_update.finalized_header.slot)
== compute_sync_committee_period_at_slot(new_update.attested_header.slot)
compute_sync_committee_period_at_slot(new_update.finalized_header.beacon.slot)
== compute_sync_committee_period_at_slot(new_update.attested_header.beacon.slot)
)
old_has_sync_committee_finality = (
compute_sync_committee_period_at_slot(old_update.finalized_header.slot)
== compute_sync_committee_period_at_slot(old_update.attested_header.slot)
compute_sync_committee_period_at_slot(old_update.finalized_header.beacon.slot)
== compute_sync_committee_period_at_slot(old_update.attested_header.beacon.slot)
)
if new_has_sync_committee_finality != old_has_sync_committee_finality:
return new_has_sync_committee_finality
@ -215,8 +224,8 @@ def is_better_update(new_update: LightClientUpdate, old_update: LightClientUpdat
return new_num_active_participants > old_num_active_participants
# Tiebreaker 2: Prefer older data (fewer changes to best)
if new_update.attested_header.slot != old_update.attested_header.slot:
return new_update.attested_header.slot < old_update.attested_header.slot
if new_update.attested_header.beacon.slot != old_update.attested_header.beacon.slot:
return new_update.attested_header.beacon.slot < old_update.attested_header.beacon.slot
return new_update.signature_slot < old_update.signature_slot
```
@ -260,14 +269,14 @@ A light client maintains its state in a `store` object of type `LightClientStore
```python
def initialize_light_client_store(trusted_block_root: Root,
bootstrap: LightClientBootstrap) -> LightClientStore:
assert hash_tree_root(bootstrap.header) == trusted_block_root
assert hash_tree_root(bootstrap.header.beacon) == trusted_block_root
assert is_valid_merkle_branch(
leaf=hash_tree_root(bootstrap.current_sync_committee),
branch=bootstrap.current_sync_committee_branch,
depth=floorlog2(CURRENT_SYNC_COMMITTEE_INDEX),
index=get_subtree_index(CURRENT_SYNC_COMMITTEE_INDEX),
root=bootstrap.header.state_root,
root=bootstrap.header.beacon.state_root,
)
return LightClientStore(
@ -301,8 +310,10 @@ def validate_light_client_update(store: LightClientStore,
assert sum(sync_aggregate.sync_committee_bits) >= MIN_SYNC_COMMITTEE_PARTICIPANTS
# Verify update does not skip a sync committee period
assert current_slot >= update.signature_slot > update.attested_header.slot >= update.finalized_header.slot
store_period = compute_sync_committee_period_at_slot(store.finalized_header.slot)
update_attested_slot = update.attested_header.beacon.slot
update_finalized_slot = update.finalized_header.beacon.slot
assert current_slot >= update.signature_slot > update_attested_slot >= update_finalized_slot
store_period = compute_sync_committee_period_at_slot(store.finalized_header.beacon.slot)
update_signature_period = compute_sync_committee_period_at_slot(update.signature_slot)
if is_next_sync_committee_known(store):
assert update_signature_period in (store_period, store_period + 1)
@ -310,12 +321,12 @@ def validate_light_client_update(store: LightClientStore,
assert update_signature_period == store_period
# Verify update is relevant
update_attested_period = compute_sync_committee_period_at_slot(update.attested_header.slot)
update_attested_period = compute_sync_committee_period_at_slot(update_attested_slot)
update_has_next_sync_committee = not is_next_sync_committee_known(store) and (
is_sync_committee_update(update) and update_attested_period == store_period
)
assert (
update.attested_header.slot > store.finalized_header.slot
update_attested_slot > store.finalized_header.beacon.slot
or update_has_next_sync_committee
)
@ -323,19 +334,19 @@ def validate_light_client_update(store: LightClientStore,
# to match the finalized checkpoint root saved in the state of `attested_header`.
# Note that the genesis finalized checkpoint root is represented as a zero hash.
if not is_finality_update(update):
assert update.finalized_header == BeaconBlockHeader()
assert update.finalized_header == LightClientHeader()
else:
if update.finalized_header.slot == GENESIS_SLOT:
assert update.finalized_header == BeaconBlockHeader()
if update_finalized_slot == GENESIS_SLOT:
assert update.finalized_header == LightClientHeader()
finalized_root = Bytes32()
else:
finalized_root = hash_tree_root(update.finalized_header)
finalized_root = hash_tree_root(update.finalized_header.beacon)
assert is_valid_merkle_branch(
leaf=finalized_root,
branch=update.finality_branch,
depth=floorlog2(FINALIZED_ROOT_INDEX),
index=get_subtree_index(FINALIZED_ROOT_INDEX),
root=update.attested_header.state_root,
root=update.attested_header.beacon.state_root,
)
# Verify that the `next_sync_committee`, if present, actually is the next sync committee saved in the
@ -350,7 +361,7 @@ def validate_light_client_update(store: LightClientStore,
branch=update.next_sync_committee_branch,
depth=floorlog2(NEXT_SYNC_COMMITTEE_INDEX),
index=get_subtree_index(NEXT_SYNC_COMMITTEE_INDEX),
root=update.attested_header.state_root,
root=update.attested_header.beacon.state_root,
)
# Verify sync committee aggregate signature
@ -364,7 +375,7 @@ def validate_light_client_update(store: LightClientStore,
]
fork_version = compute_fork_version(compute_epoch_at_slot(update.signature_slot))
domain = compute_domain(DOMAIN_SYNC_COMMITTEE, fork_version, genesis_validators_root)
signing_root = compute_signing_root(update.attested_header, domain)
signing_root = compute_signing_root(update.attested_header.beacon, domain)
assert bls.FastAggregateVerify(participant_pubkeys, signing_root, sync_aggregate.sync_committee_signature)
```
@ -372,8 +383,8 @@ def validate_light_client_update(store: LightClientStore,
```python
def apply_light_client_update(store: LightClientStore, update: LightClientUpdate) -> None:
store_period = compute_sync_committee_period_at_slot(store.finalized_header.slot)
update_finalized_period = compute_sync_committee_period_at_slot(update.finalized_header.slot)
store_period = compute_sync_committee_period_at_slot(store.finalized_header.beacon.slot)
update_finalized_period = compute_sync_committee_period_at_slot(update.finalized_header.beacon.slot)
if not is_next_sync_committee_known(store):
assert update_finalized_period == store_period
store.next_sync_committee = update.next_sync_committee
@ -382,9 +393,9 @@ def apply_light_client_update(store: LightClientStore, update: LightClientUpdate
store.next_sync_committee = update.next_sync_committee
store.previous_max_active_participants = store.current_max_active_participants
store.current_max_active_participants = 0
if update.finalized_header.slot > store.finalized_header.slot:
if update.finalized_header.beacon.slot > store.finalized_header.beacon.slot:
store.finalized_header = update.finalized_header
if store.finalized_header.slot > store.optimistic_header.slot:
if store.finalized_header.beacon.slot > store.optimistic_header.beacon.slot:
store.optimistic_header = store.finalized_header
```
@ -393,14 +404,14 @@ def apply_light_client_update(store: LightClientStore, update: LightClientUpdate
```python
def process_light_client_store_force_update(store: LightClientStore, current_slot: Slot) -> None:
if (
current_slot > store.finalized_header.slot + UPDATE_TIMEOUT
current_slot > store.finalized_header.beacon.slot + UPDATE_TIMEOUT
and store.best_valid_update is not None
):
# Forced best update when the update timeout has elapsed.
# Because the apply logic waits for `finalized_header.slot` to indicate sync committee finality,
# Because the apply logic waits for `finalized_header.beacon.slot` to indicate sync committee finality,
# the `attested_header` may be treated as `finalized_header` in extended periods of non-finality
# to guarantee progression into later sync committee periods according to `is_better_update`.
if store.best_valid_update.finalized_header.slot <= store.finalized_header.slot:
if store.best_valid_update.finalized_header.beacon.slot <= store.finalized_header.beacon.slot:
store.best_valid_update.finalized_header = store.best_valid_update.attested_header
apply_light_client_update(store, store.best_valid_update)
store.best_valid_update = None
@ -433,7 +444,7 @@ def process_light_client_update(store: LightClientStore,
# Update the optimistic header
if (
sum(sync_committee_bits) > get_safety_threshold(store)
and update.attested_header.slot > store.optimistic_header.slot
and update.attested_header.beacon.slot > store.optimistic_header.beacon.slot
):
store.optimistic_header = update.attested_header
@ -441,14 +452,14 @@ def process_light_client_update(store: LightClientStore,
update_has_finalized_next_sync_committee = (
not is_next_sync_committee_known(store)
and is_sync_committee_update(update) and is_finality_update(update) and (
compute_sync_committee_period_at_slot(update.finalized_header.slot)
== compute_sync_committee_period_at_slot(update.attested_header.slot)
compute_sync_committee_period_at_slot(update.finalized_header.beacon.slot)
== compute_sync_committee_period_at_slot(update.attested_header.beacon.slot)
)
)
if (
sum(sync_committee_bits) * 3 >= len(sync_committee_bits) * 2
and (
update.finalized_header.slot > store.finalized_header.slot
update.finalized_header.beacon.slot > store.finalized_header.beacon.slot
or update_has_finalized_next_sync_committee
)
):
@ -487,7 +498,7 @@ def process_light_client_optimistic_update(store: LightClientStore,
attested_header=optimistic_update.attested_header,
next_sync_committee=SyncCommittee(),
next_sync_committee_branch=[Bytes32() for _ in range(floorlog2(NEXT_SYNC_COMMITTEE_INDEX))],
finalized_header=BeaconBlockHeader(),
finalized_header=LightClientHeader(),
finality_branch=[Bytes32() for _ in range(floorlog2(FINALIZED_ROOT_INDEX))],
sync_aggregate=optimistic_update.sync_aggregate,
signature_slot=optimistic_update.signature_slot,

74
tests/core/pyspec/eth2spec/test/altair/light_client/test_sync.py
View File

@ -56,18 +56,18 @@ def get_update_file_name(spec, update):
suffix2 = "f"
else:
suffix2 = "x"
return f"update_{encode_hex(update.attested_header.hash_tree_root())}_{suffix1}{suffix2}"
return f"update_{encode_hex(update.attested_header.beacon.hash_tree_root())}_{suffix1}{suffix2}"
def get_checks(store):
return {
"finalized_header": {
'slot': int(store.finalized_header.slot),
'beacon_root': encode_hex(store.finalized_header.hash_tree_root()),
'slot': int(store.finalized_header.beacon.slot),
'beacon_root': encode_hex(store.finalized_header.beacon.hash_tree_root()),
},
"optimistic_header": {
'slot': int(store.optimistic_header.slot),
'beacon_root': encode_hex(store.optimistic_header.hash_tree_root()),
'slot': int(store.optimistic_header.beacon.slot),
'beacon_root': encode_hex(store.optimistic_header.beacon.hash_tree_root()),
},
}
@ -141,10 +141,10 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Advance to next sync committee period
# ```
@ -167,10 +167,10 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Edge case: Signature in next period
# ```
@ -193,10 +193,10 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Edge case: Finalized header not included
# ```
@ -214,10 +214,10 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
update = yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block=None)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update == update
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Non-finalized case: Attested `next_sync_committee` is not finalized
# ```
@ -236,10 +236,10 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
update = yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update == update
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Force-update using timeout
# ```
@ -256,10 +256,10 @@ def test_light_client_sync(spec, state):
attested_state = state.copy()
next_slots(spec, state, spec.UPDATE_TIMEOUT - 1)
yield from emit_force_update(test, spec, state)
assert test.store.finalized_header.slot == store_state.slot
assert test.store.finalized_header.beacon.slot == store_state.slot
assert test.store.next_sync_committee == store_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == store_state.slot
assert test.store.optimistic_header.beacon.slot == store_state.slot
# Edge case: Finalized header not included, after force-update
# ```
@ -275,10 +275,10 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
update = yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block=None)
assert test.store.finalized_header.slot == store_state.slot
assert test.store.finalized_header.beacon.slot == store_state.slot
assert test.store.next_sync_committee == store_state.next_sync_committee
assert test.store.best_valid_update == update
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Edge case: Finalized header older than store
# ```
@ -296,15 +296,15 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
update = yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == store_state.slot
assert test.store.finalized_header.beacon.slot == store_state.slot
assert test.store.next_sync_committee == store_state.next_sync_committee
assert test.store.best_valid_update == update
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
yield from emit_force_update(test, spec, state)
assert test.store.finalized_header.slot == attested_state.slot
assert test.store.finalized_header.beacon.slot == attested_state.slot
assert test.store.next_sync_committee == attested_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Advance to next sync committee period
# ```
@ -327,10 +327,10 @@ def test_light_client_sync(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Finish test
yield from finish_test(test)
@ -357,10 +357,10 @@ def test_supply_sync_committee_from_past_update(spec, state):
# Apply `LightClientUpdate` from the past, populating `store.next_sync_committee`
yield from emit_update(test, spec, past_state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == state.slot
assert test.store.finalized_header.beacon.slot == state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == state.slot
assert test.store.optimistic_header.beacon.slot == state.slot
# Finish test
yield from finish_test(test)
@ -383,10 +383,10 @@ def test_advance_finality_without_sync_committee(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Advance finality into next sync committee period, but omit `next_sync_committee`
transition_to(spec, state, compute_start_slot_at_next_sync_committee_period(spec, state))
@ -402,10 +402,10 @@ def test_advance_finality_without_sync_committee(spec, state):
sync_aggregate, _ = get_sync_aggregate(spec, state)
block = state_transition_with_full_block(spec, state, True, True, sync_aggregate=sync_aggregate)
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block, with_next=False)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert not spec.is_next_sync_committee_known(test.store)
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Advance finality once more, with `next_sync_committee` still unknown
past_state = finalized_state
@ -419,24 +419,24 @@ def test_advance_finality_without_sync_committee(spec, state):
# Apply `LightClientUpdate` without `finalized_header` nor `next_sync_committee`
update = yield from emit_update(test, spec, state, block, attested_state, attested_block, None, with_next=False)
assert test.store.finalized_header.slot == past_state.slot
assert test.store.finalized_header.beacon.slot == past_state.slot
assert not spec.is_next_sync_committee_known(test.store)
assert test.store.best_valid_update == update
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Apply `LightClientUpdate` with `finalized_header` but no `next_sync_committee`
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block, with_next=False)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert not spec.is_next_sync_committee_known(test.store)
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Apply full `LightClientUpdate`, supplying `next_sync_committee`
yield from emit_update(test, spec, state, block, attested_state, attested_block, finalized_block)
assert test.store.finalized_header.slot == finalized_state.slot
assert test.store.finalized_header.beacon.slot == finalized_state.slot
assert test.store.next_sync_committee == finalized_state.next_sync_committee
assert test.store.best_valid_update is None
assert test.store.optimistic_header.slot == attested_state.slot
assert test.store.optimistic_header.beacon.slot == attested_state.slot
# Finish test
yield from finish_test(test)

2
tests/core/pyspec/eth2spec/test/altair/light_client/test_update_ranking.py
View File

@ -37,7 +37,7 @@ def test_update_ranking(spec, state):
# - `sig_finalized` / `sig_attested` --> Only signature in next sync committee period
# - `att_finalized` / `att_attested` --> Attested header also in next sync committee period
# - `fin_finalized` / `fin_attested` --> Finalized header also in next sync committee period
# - `lat_finalized` / `lat_attested` --> Like `fin`, but at a later `attested_header.slot`
# - `lat_finalized` / `lat_attested` --> Like `fin`, but at a later `attested_header.beacon.slot`
next_slots(spec, state, spec.compute_start_slot_at_epoch(spec.EPOCHS_PER_SYNC_COMMITTEE_PERIOD - 3) - 1)
sig_finalized_block = state_transition_with_full_block(spec, state, True, True)
_, _, state = next_slots_with_attestations(spec, state, spec.SLOTS_PER_EPOCH - 1, True, True)

6
tests/core/pyspec/eth2spec/test/altair/unittests/light_client/test_sync_protocol.py
View File

@ -69,7 +69,7 @@ def test_process_light_client_update_at_period_boundary(spec, state):
# Forward to slot before next sync committee period so that next block is final one in period
next_slots(spec, state, spec.UPDATE_TIMEOUT - 2)
store_period = spec.compute_sync_committee_period_at_slot(store.optimistic_header.slot)
store_period = spec.compute_sync_committee_period_at_slot(store.optimistic_header.beacon.slot)
update_period = spec.compute_sync_committee_period_at_slot(state.slot)
assert store_period == update_period
@ -104,7 +104,7 @@ def test_process_light_client_update_timeout(spec, state):
# Forward to next sync committee period
next_slots(spec, state, spec.UPDATE_TIMEOUT)
store_period = spec.compute_sync_committee_period_at_slot(store.optimistic_header.slot)
store_period = spec.compute_sync_committee_period_at_slot(store.optimistic_header.beacon.slot)
update_period = spec.compute_sync_committee_period_at_slot(state.slot)
assert store_period + 1 == update_period
@ -146,7 +146,7 @@ def test_process_light_client_update_finality_updated(spec, state):
# Ensure that finality checkpoint has changed
assert state.finalized_checkpoint.epoch == 3
# Ensure that it's same period
store_period = spec.compute_sync_committee_period_at_slot(store.optimistic_header.slot)
store_period = spec.compute_sync_committee_period_at_slot(store.optimistic_header.beacon.slot)
update_period = spec.compute_sync_committee_period_at_slot(state.slot)
assert store_period == update_period

8
tests/formats/light_client/sync.md
View File

@ -25,12 +25,12 @@ Each step includes checks to verify the expected impact on the `store` object.
```yaml
finalized_header: {
slot: int, -- Integer value from store.finalized_header.slot
beacon_root: string, -- Encoded 32-byte value from store.finalized_header.hash_tree_root()
slot: int, -- Integer value from store.finalized_header.beacon.slot
beacon_root: string, -- Encoded 32-byte value from store.finalized_header.beacon.hash_tree_root()
}
optimistic_header: {
slot: int, -- Integer value from store.optimistic_header.slot
beacon_root: string, -- Encoded 32-byte value from store.optimistic_header.hash_tree_root()
slot: int, -- Integer value from store.optimistic_header.beacon.slot
beacon_root: string, -- Encoded 32-byte value from store.optimistic_header.beacon.hash_tree_root()
}
```