A0-4563: Added unit test for censorship resistance in Extender (#503)

* A0-4563: Added a UT in which one of the nodes is missing units

* Adding some non-direct parents

* fmt

* Actually use first round

* clippy

* Bump consensus crate version

* Review

consensus/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aleph-bft"
-version = "0.39.0"
+version = "0.39.1"
 edition = "2021"
 authors = ["Cardinal Cryptography"]
 categories = ["algorithms", "data-structures", "cryptography", "database"]

consensus/src/dag/mod.rs

@@ -468,7 +468,7 @@ mod test {
             .take(5)
             .cloned()
             .collect();
-        let fork = random_unit_with_parents(forker_id, &fork_parents);
+        let fork = random_unit_with_parents(forker_id, &fork_parents, 3);
         let fork = Signed::sign(fork, &keychains[forker_id.0]);
         let unit = units
             .get(3)
@@ -552,7 +552,7 @@ mod test {
             .take(5)
             .cloned()
             .collect();
-        let fork = random_unit_with_parents(forker_id, &fork_parents);
+        let fork = random_unit_with_parents(forker_id, &fork_parents, 3);
         let fork = Signed::sign(fork, &keychains[forker_id.0]);
         let unit = units
             .get(3)

consensus/src/extension/election.rs

@@ -217,8 +217,8 @@ mod test {
             units::Units,
         },
         units::{
-            random_full_parent_reconstrusted_units_up_to, random_reconstructed_unit_with_parents,
-            TestingDagUnit, Unit,
+            minimal_reconstructed_dag_units_up_to, random_full_parent_reconstrusted_units_up_to,
+            random_reconstructed_unit_with_parents, TestingDagUnit, Unit,
         },
         NodeCount,
     };
@@ -344,6 +344,7 @@ mod test {
                     creator,
                     &parents,
                     &keychains[creator.0],
+                    round,
                 ));
             }
         }
@@ -356,4 +357,32 @@ mod test {
             }
         }
     }
+
+    #[test]
+    #[ignore]
+    // TODO(A0-4563) Uncomment after changes to parent voting code
+    fn given_minimal_dag_with_orphaned_node_when_electing_then_orphaned_node_is_not_head() {
+        use ElectionResult::*;
+        let mut units = Units::new();
+        let n_members = NodeCount(14);
+        let max_round = 4;
+        let session_id = 2137;
+        let keychains = Keychain::new_vec(n_members);
+
+        let (dag, inactive_node_first_unit) =
+            minimal_reconstructed_dag_units_up_to(max_round, n_members, session_id, &keychains);
+        for round in dag {
+            for unit in round {
+                units.add_unit(unit);
+            }
+        }
+        let election = RoundElection::for_round(0, &units).expect("we have enough rounds");
+        match election {
+            Pending(_) => panic!("should have elected"),
+            Elected(head) => {
+                // This should be the second unit in order, as the first was not popular.
+                assert_ne!(head, inactive_node_first_unit.hash());
+            }
+        }
+    }
 }

consensus/src/extension/extender.rs

@@ -70,6 +70,7 @@ impl<U: UnitWithParents> Extender<U> {
 
 #[cfg(test)]
 mod test {
+    use crate::units::{minimal_reconstructed_dag_units_up_to, Unit};
     use crate::{
         extension::extender::Extender, units::random_full_parent_reconstrusted_units_up_to,
         NodeCount, Round,
@@ -97,4 +98,30 @@ mod test {
             assert_eq!(batch.len(), n_members.0);
         }
     }
+
+    #[test]
+    #[ignore]
+    // TODO(A0-4563) Uncomment after changes to parent voting code
+    fn given_minimal_dag_with_orphaned_node_when_producing_batches_have_correct_length() {
+        let mut extender = Extender::new();
+        let n_members = NodeCount(4);
+        let threshold = n_members.consensus_threshold();
+        let max_round: Round = 4;
+        let session_id = 2137;
+        let keychains = Keychain::new_vec(n_members);
+        let mut batches = Vec::new();
+        let (dag, _) =
+            minimal_reconstructed_dag_units_up_to(max_round, n_members, session_id, &keychains);
+        for round in dag {
+            for unit in round {
+                batches.append(&mut extender.add_unit(unit));
+            }
+        }
+        assert_eq!(batches.len(), (max_round - 3).into());
+        assert_eq!(batches[0].len(), 1);
+        assert_eq!(batches[0][0].round(), 0);
+        for batch in batches.iter().skip(1) {
+            assert_eq!(batch.len(), threshold.0);
+        }
+    }
 }

consensus/src/units/mod.rs

@@ -15,11 +15,12 @@ mod validator;
 pub(crate) use store::*;
 #[cfg(test)]
 pub use testing::{
-    create_preunits, creator_set, full_unit_to_unchecked_signed_unit, preunit_to_full_unit,
-    preunit_to_signed_unit, preunit_to_unchecked_signed_unit,
-    random_full_parent_reconstrusted_units_up_to, random_full_parent_units_up_to,
-    random_reconstructed_unit_with_parents, random_unit_with_parents, DagUnit as TestingDagUnit,
-    FullUnit as TestingFullUnit, SignedUnit as TestingSignedUnit, WrappedSignedUnit,
+    create_preunits, creator_set, full_unit_to_unchecked_signed_unit,
+    minimal_reconstructed_dag_units_up_to, preunit_to_full_unit, preunit_to_signed_unit,
+    preunit_to_unchecked_signed_unit, random_full_parent_reconstrusted_units_up_to,
+    random_full_parent_units_up_to, random_reconstructed_unit_with_parents,
+    random_unit_with_parents, DagUnit as TestingDagUnit, FullUnit as TestingFullUnit,
+    SignedUnit as TestingSignedUnit, WrappedSignedUnit,
 };
 pub use validator::{ValidationError, Validator};
 

consensus/src/units/testing.rs

@@ -1,3 +1,4 @@
+use crate::units::TestingDagUnit;
 use crate::{
     creation::Creator as GenericCreator,
     dag::ReconstructedUnit,
@@ -9,6 +10,7 @@ use crate::{
     NodeCount, NodeIndex, NodeMap, Round, SessionId, Signed,
 };
 use aleph_bft_mock::{Data, Hash64, Hasher64, Keychain, Signature};
+use rand::prelude::IteratorRandom;
 
 type ControlHash = GenericControlHash<Hasher64>;
 type Creator = GenericCreator<Hasher64>;
@@ -149,10 +151,10 @@ fn parent_map<U: Unit<Hasher = Hasher64>>(parents: &Vec<U>) -> NodeMap<Hash64> {
 pub fn random_unit_with_parents<U: Unit<Hasher = Hasher64>>(
     creator: NodeIndex,
     parents: &Vec<U>,
+    round: Round,
 ) -> FullUnit {
     let representative_parent = parents.last().expect("there are parents");
     let session_id = representative_parent.session_id();
-    let round = representative_parent.round() + 1;
     let parent_map = parent_map(parents);
     let control_hash = ControlHash::new(&parent_map);
     preunit_to_full_unit(PreUnit::new(creator, round, control_hash), session_id)
@@ -162,9 +164,10 @@ pub fn random_reconstructed_unit_with_parents<U: Unit<Hasher = Hasher64>>(
     creator: NodeIndex,
     parents: &Vec<U>,
     keychain: &Keychain,
+    round: Round,
 ) -> DagUnit {
     ReconstructedUnit::with_parents(
-        full_unit_to_signed_unit(random_unit_with_parents(creator, parents), keychain),
+        full_unit_to_signed_unit(random_unit_with_parents(creator, parents, round), keychain),
         parent_map(parents),
     )
     .expect("correct parents")
@@ -176,18 +179,20 @@ pub fn random_full_parent_units_up_to(
     session_id: SessionId,
 ) -> Vec<Vec<FullUnit>> {
     let mut result = vec![random_initial_units(n_members, session_id)];
-    for _ in 0..round {
+    for r in 1..=round {
         let units = n_members
             .into_iterator()
             .map(|node_id| {
-                random_unit_with_parents(node_id, result.last().expect("previous round present"))
+                random_unit_with_parents(node_id, result.last().expect("previous round present"), r)
             })
             .collect();
         result.push(units);
     }
     result
 }
 
+/// Constructs a DAG so that in each round (except round 0) it has all N parents, where N is number
+/// of nodes in the DAG
 pub fn random_full_parent_reconstrusted_units_up_to(
     round: Round,
     n_members: NodeCount,
@@ -197,18 +202,70 @@ pub fn random_full_parent_reconstrusted_units_up_to(
     let mut result = vec![random_initial_reconstructed_units(
         n_members, session_id, keychains,
     )];
-    for _ in 0..round {
+    for r in 1..=round {
         let units = n_members
             .into_iterator()
             .map(|node_id| {
                 random_reconstructed_unit_with_parents(
                     node_id,
                     result.last().expect("previous round present"),
                     &keychains[node_id.0],
+                    r,
                 )
             })
             .collect();
         result.push(units);
     }
     result
 }
+
+/// Constructs a DAG so that in each round (except round 0) it has at least 2N/3 + 1 parents, where
+/// N is number of nodes in the DAG. At least one node from N/3 group has some non-direct parents.
+pub fn minimal_reconstructed_dag_units_up_to(
+    round: Round,
+    n_members: NodeCount,
+    session_id: SessionId,
+    keychains: &[Keychain],
+) -> (Vec<Vec<DagUnit>>, DagUnit) {
+    let mut rng = rand::thread_rng();
+    let threshold = n_members.consensus_threshold().0;
+
+    let mut dag = vec![random_initial_reconstructed_units(
+        n_members, session_id, keychains,
+    )];
+    let inactive_node_first_and_last_seen_unit = dag
+        .last()
+        .expect("previous round present")
+        .last()
+        .expect("there is at least one node")
+        .clone();
+    let inactive_node = inactive_node_first_and_last_seen_unit.creator();
+    for r in 1..=round {
+        let mut parents: Vec<TestingDagUnit> = dag
+            .last()
+            .expect("previous round present")
+            .clone()
+            .into_iter()
+            .filter(|unit| unit.creator() != inactive_node)
+            .choose_multiple(&mut rng, threshold)
+            .into_iter()
+            .collect();
+        if r == round {
+            let ancestor_unit = dag
+                .first()
+                .expect("first round present")
+                .get(inactive_node.0)
+                .expect("inactive node unit present");
+            parents.push(ancestor_unit.clone());
+        }
+        let units = n_members
+            .into_iterator()
+            .filter(|node_id| node_id != &inactive_node)
+            .map(|node_id| {
+                random_reconstructed_unit_with_parents(node_id, &parents, &keychains[node_id.0], r)
+            })
+            .collect();
+        dag.push(units);
+    }
+    (dag, inactive_node_first_and_last_seen_unit)
+}

consensus/src/units/validator.rs

@@ -254,7 +254,7 @@ mod tests {
             .take(4)
             .cloned()
             .collect();
-        let unit = random_unit_with_parents(creator_id, &parents);
+        let unit = random_unit_with_parents(creator_id, &parents, 1);
         let preunit = unit.as_pre_unit().clone();
         let keychain = Keychain::new(n_members, creator_id);
         let unchecked_unit = full_unit_to_unchecked_signed_unit(unit, &keychain);