Add is_parent_strong proposer re-org check (#5417)

* initial fork choice additions

* add helper fns

* add is_parent_strong

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into add_is_parent_strong_check

* disabling proposer reorg should set parent_threshold to u64 max

* add new flag, is_parent_strong check in override fcu params

* cherry-pick changes

* Merge branch 'unstable' of https://github.com/sigp/lighthouse into add_is_parent_strong_check

* cleanup

* fmt

* Minor review tweaks

Author: eserilev

beacon_node/beacon_chain/src/beacon_chain.rs

@@ -4262,7 +4262,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         head_slot: Slot,
         canonical_head: Hash256,
     ) -> Option<BlockProductionPreState<T::EthSpec>> {
-        let re_org_threshold = self.config.re_org_threshold?;
+        let re_org_head_threshold = self.config.re_org_head_threshold?;
+        let re_org_parent_threshold = self.config.re_org_parent_threshold?;
 
         if self.spec.proposer_score_boost.is_none() {
             warn!(
@@ -4319,7 +4320,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             .get_proposer_head(
                 slot,
                 canonical_head,
-                re_org_threshold,
+                re_org_head_threshold,
+                re_org_parent_threshold,
                 &self.config.re_org_disallowed_offsets,
                 self.config.re_org_max_epochs_since_finalization,
             )
@@ -4373,7 +4375,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             "weak_head" => ?canonical_head,
             "parent" => ?re_org_parent_block,
             "head_weight" => proposer_head.head_node.weight,
-            "threshold_weight" => proposer_head.re_org_weight_threshold
+            "threshold_weight" => proposer_head.re_org_head_weight_threshold
         );
 
         Some(pre_state)
@@ -4593,9 +4595,14 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         let _timer = metrics::start_timer(&metrics::FORK_CHOICE_OVERRIDE_FCU_TIMES);
 
         // Never override if proposer re-orgs are disabled.
-        let re_org_threshold = self
+        let re_org_head_threshold = self
             .config
-            .re_org_threshold
+            .re_org_head_threshold
+            .ok_or(DoNotReOrg::ReOrgsDisabled)?;
+
+        let re_org_parent_threshold = self
+            .config
+            .re_org_parent_threshold
             .ok_or(DoNotReOrg::ReOrgsDisabled)?;
 
         let head_block_root = canonical_forkchoice_params.head_root;
@@ -4606,7 +4613,8 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
             .fork_choice_read_lock()
             .get_preliminary_proposer_head(
                 head_block_root,
-                re_org_threshold,
+                re_org_head_threshold,
+                re_org_parent_threshold,
                 &self.config.re_org_disallowed_offsets,
                 self.config.re_org_max_epochs_since_finalization,
             )
@@ -4674,16 +4682,27 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         }
 
         // If the current slot is already equal to the proposal slot (or we are in the tail end of
-        // the prior slot), then check the actual weight of the head against the re-org threshold.
-        let head_weak = if fork_choice_slot == re_org_block_slot {
-            info.head_node.weight < info.re_org_weight_threshold
+        // the prior slot), then check the actual weight of the head against the head re-org threshold
+        // and the actual weight of the parent against the parent re-org threshold.
+        let (head_weak, parent_strong) = if fork_choice_slot == re_org_block_slot {
+            (
+                info.head_node.weight < info.re_org_head_weight_threshold,
+                info.parent_node.weight > info.re_org_parent_weight_threshold,
+            )
         } else {
-            true
+            (true, true)
         };
         if !head_weak {
             return Err(DoNotReOrg::HeadNotWeak {
                 head_weight: info.head_node.weight,
-                re_org_weight_threshold: info.re_org_weight_threshold,
+                re_org_head_weight_threshold: info.re_org_head_weight_threshold,
+            }
+            .into());
+        }
+        if !parent_strong {
+            return Err(DoNotReOrg::ParentNotStrong {
+                parent_weight: info.parent_node.weight,
+                re_org_parent_weight_threshold: info.re_org_parent_weight_threshold,
             }
             .into());
         }

beacon_node/beacon_chain/src/builder.rs

@@ -172,8 +172,8 @@ where
     }
 
     /// Sets the proposer re-org threshold.
-    pub fn proposer_re_org_threshold(mut self, threshold: Option<ReOrgThreshold>) -> Self {
-        self.chain_config.re_org_threshold = threshold;
+    pub fn proposer_re_org_head_threshold(mut self, threshold: Option<ReOrgThreshold>) -> Self {
+        self.chain_config.re_org_head_threshold = threshold;
         self
     }
 

beacon_node/beacon_chain/src/chain_config.rs

@@ -3,7 +3,8 @@ use serde::{Deserialize, Serialize};
 use std::time::Duration;
 use types::{Checkpoint, Epoch};
 
-pub const DEFAULT_RE_ORG_THRESHOLD: ReOrgThreshold = ReOrgThreshold(20);
+pub const DEFAULT_RE_ORG_HEAD_THRESHOLD: ReOrgThreshold = ReOrgThreshold(20);
+pub const DEFAULT_RE_ORG_PARENT_THRESHOLD: ReOrgThreshold = ReOrgThreshold(160);
 pub const DEFAULT_RE_ORG_MAX_EPOCHS_SINCE_FINALIZATION: Epoch = Epoch::new(2);
 /// Default to 1/12th of the slot, which is 1 second on mainnet.
 pub const DEFAULT_RE_ORG_CUTOFF_DENOMINATOR: u32 = 12;
@@ -31,8 +32,10 @@ pub struct ChainConfig {
     pub enable_lock_timeouts: bool,
     /// The max size of a message that can be sent over the network.
     pub max_network_size: usize,
-    /// Maximum percentage of committee weight at which to attempt re-orging the canonical head.
-    pub re_org_threshold: Option<ReOrgThreshold>,
+    /// Maximum percentage of the head committee weight at which to attempt re-orging the canonical head.
+    pub re_org_head_threshold: Option<ReOrgThreshold>,
+    /// Minimum percentage of the parent committee weight at which to attempt re-orging the canonical head.
+    pub re_org_parent_threshold: Option<ReOrgThreshold>,
     /// Maximum number of epochs since finalization for attempting a proposer re-org.
     pub re_org_max_epochs_since_finalization: Epoch,
     /// Maximum delay after the start of the slot at which to propose a reorging block.
@@ -95,7 +98,8 @@ impl Default for ChainConfig {
             reconstruct_historic_states: false,
             enable_lock_timeouts: true,
             max_network_size: 10 * 1_048_576, // 10M
-            re_org_threshold: Some(DEFAULT_RE_ORG_THRESHOLD),
+            re_org_head_threshold: Some(DEFAULT_RE_ORG_HEAD_THRESHOLD),
+            re_org_parent_threshold: Some(DEFAULT_RE_ORG_PARENT_THRESHOLD),
             re_org_max_epochs_since_finalization: DEFAULT_RE_ORG_MAX_EPOCHS_SINCE_FINALIZATION,
             re_org_cutoff_millis: None,
             re_org_disallowed_offsets: DisallowedReOrgOffsets::default(),

beacon_node/http_api/tests/interactive_tests.rs

@@ -419,7 +419,7 @@ pub async fn proposer_boost_re_org_test(
         None,
         Some(Box::new(move |builder| {
             builder
-                .proposer_re_org_threshold(Some(ReOrgThreshold(re_org_threshold)))
+                .proposer_re_org_head_threshold(Some(ReOrgThreshold(re_org_threshold)))
                 .proposer_re_org_max_epochs_since_finalization(Epoch::new(
                     max_epochs_since_finalization,
                 ))

beacon_node/src/cli.rs

@@ -1040,10 +1040,18 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
             Arg::with_name("proposer-reorg-threshold")
                 .long("proposer-reorg-threshold")
                 .value_name("PERCENT")
-                .help("Percentage of vote weight below which to attempt a proposer reorg. \
+                .help("Percentage of head vote weight below which to attempt a proposer reorg. \
                        Default: 20%")
                 .conflicts_with("disable-proposer-reorgs")
         )
+        .arg(
+            Arg::with_name("proposer-reorg-parent-threshold")
+                .long("proposer-reorg-parent-threshold")
+                .value_name("PERCENT")
+                .help("Percentage of parent vote weight above which to attempt a proposer reorg. \
+                       Default: 160%")
+                .conflicts_with("disable-proposer-reorgs")
+        )
         .arg(
             Arg::with_name("proposer-reorg-epochs-since-finalization")
                 .long("proposer-reorg-epochs-since-finalization")

beacon_node/src/config.rs

@@ -1,6 +1,7 @@
 use beacon_chain::chain_config::{
     DisallowedReOrgOffsets, ReOrgThreshold, DEFAULT_PREPARE_PAYLOAD_LOOKAHEAD_FACTOR,
-    DEFAULT_RE_ORG_MAX_EPOCHS_SINCE_FINALIZATION, DEFAULT_RE_ORG_THRESHOLD,
+    DEFAULT_RE_ORG_HEAD_THRESHOLD, DEFAULT_RE_ORG_MAX_EPOCHS_SINCE_FINALIZATION,
+    DEFAULT_RE_ORG_PARENT_THRESHOLD,
 };
 use beacon_chain::TrustedSetup;
 use clap::ArgMatches;
@@ -749,19 +750,26 @@ pub fn get_config<E: EthSpec>(
     }
 
     if cli_args.is_present("disable-proposer-reorgs") {
-        client_config.chain.re_org_threshold = None;
+        client_config.chain.re_org_head_threshold = None;
+        client_config.chain.re_org_parent_threshold = None;
     } else {
-        client_config.chain.re_org_threshold = Some(
+        client_config.chain.re_org_head_threshold = Some(
             clap_utils::parse_optional(cli_args, "proposer-reorg-threshold")?
                 .map(ReOrgThreshold)
-                .unwrap_or(DEFAULT_RE_ORG_THRESHOLD),
+                .unwrap_or(DEFAULT_RE_ORG_HEAD_THRESHOLD),
         );
         client_config.chain.re_org_max_epochs_since_finalization =
             clap_utils::parse_optional(cli_args, "proposer-reorg-epochs-since-finalization")?
                 .unwrap_or(DEFAULT_RE_ORG_MAX_EPOCHS_SINCE_FINALIZATION);
         client_config.chain.re_org_cutoff_millis =
             clap_utils::parse_optional(cli_args, "proposer-reorg-cutoff")?;
 
+        client_config.chain.re_org_parent_threshold = Some(
+            clap_utils::parse_optional(cli_args, "proposer-reorg-parent-threshold")?
+                .map(ReOrgThreshold)
+                .unwrap_or(DEFAULT_RE_ORG_PARENT_THRESHOLD),
+        );
+
         if let Some(disallowed_offsets_str) =
             clap_utils::parse_optional::<String>(cli_args, "proposer-reorg-disallowed-offsets")?
         {

book/src/help_bn.md

@@ -383,8 +383,11 @@ OPTIONS:
         --proposer-reorg-epochs-since-finalization <EPOCHS>
             Maximum number of epochs since finalization at which proposer reorgs are allowed. Default: 2
 
+        --proposer-reorg-parent-threshold <PERCENT>
+            Percentage of parent vote weight above which to attempt a proposer reorg. Default: 160%
+
         --proposer-reorg-threshold <PERCENT>
-            Percentage of vote weight below which to attempt a proposer reorg. Default: 20%
+            Percentage of head vote weight below which to attempt a proposer reorg. Default: 20%
 
         --prune-blobs <BOOLEAN>
             Prune blobs from Lighthouse's database when they are older than the data data availability boundary relative

common/eth2_network_config/built_in_network_configs/gnosis/config.yaml

@@ -81,6 +81,12 @@ CHURN_LIMIT_QUOTIENT: 4096
 # ---------------------------------------------------------------
 # 40%
 PROPOSER_SCORE_BOOST: 40
+# 20%
+REORG_HEAD_WEIGHT_THRESHOLD: 20
+# 160%
+REORG_PARENT_WEIGHT_THRESHOLD: 160
+# `2` epochs
+REORG_MAX_EPOCHS_SINCE_FINALIZATION: 2
 
 # Deposit contract
 # ---------------------------------------------------------------

common/eth2_network_config/built_in_network_configs/holesky/config.yaml

@@ -71,6 +71,12 @@ MAX_PER_EPOCH_ACTIVATION_CHURN_LIMIT: 8
 # ---------------------------------------------------------------
 # 40%
 PROPOSER_SCORE_BOOST: 40
+# 20%
+REORG_HEAD_WEIGHT_THRESHOLD: 20
+# 160%
+REORG_PARENT_WEIGHT_THRESHOLD: 160
+# `2` epochs
+REORG_MAX_EPOCHS_SINCE_FINALIZATION: 2
 
 # Deposit contract
 # ---------------------------------------------------------------

common/eth2_network_config/built_in_network_configs/prater/config.yaml

@@ -78,6 +78,12 @@ MAX_PER_EPOCH_ACTIVATION_CHURN_LIMIT: 8
 # ---------------------------------------------------------------
 # 40%
 PROPOSER_SCORE_BOOST: 40
+# 20%
+REORG_HEAD_WEIGHT_THRESHOLD: 20
+# 160%
+REORG_PARENT_WEIGHT_THRESHOLD: 160
+# `2` epochs
+REORG_MAX_EPOCHS_SINCE_FINALIZATION: 2
 
 # Deposit contract
 # ---------------------------------------------------------------