A0-4568: Move response logic out of runway

consensus/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "aleph-bft"
-version = "0.38.1"
+version = "0.38.2"
 edition = "2021"
 authors = ["Cardinal Cryptography"]
 categories = ["algorithms", "data-structures", "cryptography", "database"]

consensus/src/dissemination/mod.rs

@@ -0,0 +1,25 @@
+use crate::{
+    runway::{NewestUnitResponse, Salt},
+    units::{UncheckedSignedUnit, UnitCoord},
+    Data, Hasher, NodeIndex, Signature, UncheckedSigned,
+};
+
+mod responder;
+
+pub use responder::Responder;
+
+/// Possible requests for information from other nodes.
+#[derive(Debug)]
+pub enum Request<H: Hasher> {
+    Coord(UnitCoord),
+    Parents(H::Hash),
+    NewestUnit(NodeIndex, Salt),
+}
+
+/// Responses to requests.
+#[derive(Debug)]
+pub enum Response<H: Hasher, D: Data, S: Signature> {
+    Coord(UncheckedSignedUnit<H, D, S>),
+    Parents(H::Hash, Vec<UncheckedSignedUnit<H, D, S>>),
+    NewestUnit(UncheckedSigned<NewestUnitResponse<H, D, S>, S>),
+}

consensus/src/dissemination/responder.rs

@@ -0,0 +1,338 @@
+use crate::{
+    dag::DagUnit,
+    dissemination::{Request, Response},
+    runway::{NewestUnitResponse, Salt},
+    units::{UnitCoord, UnitStore, UnitWithParents, WrappedUnit},
+    Data, Hasher, MultiKeychain, NodeIndex, Signed,
+};
+use std::marker::PhantomData;
+use thiserror::Error;
+
+/// A responder that is able to answer requests for data about units.
+pub struct Responder<H: Hasher, D: Data, MK: MultiKeychain> {
+    keychain: MK,
+    _phantom: PhantomData<(H, D)>,
+}
+
+/// Ways in which it can be impossible for us to respond to a request.
+#[derive(Eq, Error, Debug, PartialEq)]
+pub enum Error<H: Hasher> {
+    #[error("no canonical unit at {0}")]
+    NoCanonicalAt(UnitCoord),
+    #[error("unit with hash {0:?} not known")]
+    UnknownUnit(H::Hash),
+}
+
+impl<H: Hasher, D: Data, MK: MultiKeychain> Responder<H, D, MK> {
+    /// Create a new responder.
+    pub fn new(keychain: MK) -> Self {
+        Responder {
+            keychain,
+            _phantom: PhantomData,
+        }
+    }
+
+    fn index(&self) -> NodeIndex {
+        self.keychain.index()
+    }
+
+    fn on_request_coord(
+        &self,
+        coord: UnitCoord,
+        units: &UnitStore<DagUnit<H, D, MK>>,
+    ) -> Result<Response<H, D, MK::Signature>, Error<H>> {
+        units
+            .canonical_unit(coord)
+            .map(|unit| Response::Coord(unit.clone().unpack().into()))
+            .ok_or(Error::NoCanonicalAt(coord))
+    }
+
+    fn on_request_parents(
+        &self,
+        hash: H::Hash,
+        units: &UnitStore<DagUnit<H, D, MK>>,
+    ) -> Result<Response<H, D, MK::Signature>, Error<H>> {
+        units
+            .unit(&hash)
+            .map(|unit| {
+                let parents = unit
+                    .parents()
+                    .values()
+                    .map(|parent_hash| {
+                        units
+                            .unit(parent_hash)
+                            .expect("Units are added to the store in order.")
+                            .clone()
+                            .unpack()
+                            .into_unchecked()
+                    })
+                    .collect();
+                Response::Parents(hash, parents)
+            })
+            .ok_or(Error::UnknownUnit(hash))
+    }
+
+    fn on_request_newest(
+        &self,
+        requester: NodeIndex,
+        salt: Salt,
+        units: &UnitStore<DagUnit<H, D, MK>>,
+    ) -> Response<H, D, MK::Signature> {
+        let unit = units
+            .canonical_units(requester)
+            .last()
+            .map(|unit| unit.clone().unpack().into_unchecked());
+        let response = NewestUnitResponse::new(requester, self.index(), unit, salt);
+
+        let signed_response = Signed::sign(response, &self.keychain).into_unchecked();
+        Response::NewestUnit(signed_response)
+    }
+
+    /// Handle an incoming request returning either the appropriate response or an error if we
+    /// aren't able to help.
+    pub fn handle_request(
+        &self,
+        request: Request<H>,
+        units: &UnitStore<DagUnit<H, D, MK>>,
+    ) -> Result<Response<H, D, MK::Signature>, Error<H>> {
+        use Request::*;
+        match request {
+            Coord(coord) => self.on_request_coord(coord, units),
+            Parents(hash) => self.on_request_parents(hash, units),
+            NewestUnit(node_id, salt) => Ok(self.on_request_newest(node_id, salt, units)),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{
+        dissemination::{
+            responder::{Error, Responder},
+            Request, Response,
+        },
+        units::{
+            random_full_parent_reconstrusted_units_up_to, TestingDagUnit, Unit, UnitCoord,
+            UnitStore, UnitWithParents, WrappedUnit,
+        },
+        NodeCount, NodeIndex,
+    };
+    use aleph_bft_mock::{Data, Hasher64, Keychain};
+    use std::iter::zip;
+
+    const NODE_ID: NodeIndex = NodeIndex(0);
+    const NODE_COUNT: NodeCount = NodeCount(7);
+
+    fn setup() -> (
+        Responder<Hasher64, Data, Keychain>,
+        UnitStore<TestingDagUnit>,
+        Vec<Keychain>,
+    ) {
+        let keychains = Keychain::new_vec(NODE_COUNT);
+        (
+            Responder::new(keychains[NODE_ID.0]),
+            UnitStore::new(NODE_COUNT),
+            keychains,
+        )
+    }
+
+    #[test]
+    fn empty_fails_to_respond_to_coords() {
+        let (responder, store, _) = setup();
+        let coord = UnitCoord::new(0, NodeIndex(1));
+        let request = Request::Coord(coord);
+        match responder.handle_request(request, &store) {
+            Ok(response) => panic!("Unexpected response: {:?}.", response),
+            Err(err) => assert_eq!(err, Error::NoCanonicalAt(coord)),
+        }
+    }
+
+    #[test]
+    fn empty_fails_to_respond_to_parents() {
+        let (responder, store, keychains) = setup();
+        let session_id = 2137;
+        let hash =
+            random_full_parent_reconstrusted_units_up_to(1, NODE_COUNT, session_id, &keychains)
+                .last()
+                .expect("just created this round")
+                .last()
+                .expect("the round has at least one unit")
+                .hash();
+        let request = Request::Parents(hash);
+        match responder.handle_request(request, &store) {
+            Ok(response) => panic!("Unexpected response: {:?}.", response),
+            Err(err) => assert_eq!(err, Error::UnknownUnit(hash)),
+        }
+    }
+
+    #[test]
+    fn empty_newest_responds_with_no_units() {
+        let (responder, store, keychains) = setup();
+        let requester = NodeIndex(1);
+        let request = Request::NewestUnit(requester, rand::random());
+        let response = responder
+            .handle_request(request, &store)
+            .expect("newest unit requests always get a response");
+        match response {
+            Response::NewestUnit(newest_unit_response) => {
+                let checked_newest_unit_response = newest_unit_response
+                    .check(&keychains[NODE_ID.0])
+                    .expect("should sign correctly");
+                assert_eq!(
+                    checked_newest_unit_response.as_signable().requester(),
+                    requester
+                );
+                assert!(checked_newest_unit_response
+                    .as_signable()
+                    .included_data()
+                    .is_empty());
+            }
+            other => panic!("Unexpected response: {:?}.", other),
+        }
+    }
+
+    #[test]
+    fn responds_to_coords_when_possible() {
+        let (responder, mut store, keychains) = setup();
+        let session_id = 2137;
+        let coord = UnitCoord::new(3, NodeIndex(1));
+        let units = random_full_parent_reconstrusted_units_up_to(
+            coord.round() + 1,
+            NODE_COUNT,
+            session_id,
+            &keychains,
+        );
+        for round_units in &units {
+            for unit in round_units {
+                store.insert(unit.clone());
+            }
+        }
+        let request = Request::Coord(coord);
+        let response = responder
+            .handle_request(request, &store)
+            .expect("should successfully respond");
+        match response {
+            Response::Coord(unit) => assert_eq!(
+                unit,
+                units[coord.round() as usize][coord.creator().0]
+                    .clone()
+                    .unpack()
+                    .into_unchecked()
+            ),
+            other => panic!("Unexpected response: {:?}.", other),
+        }
+    }
+
+    #[test]
+    fn fails_to_responds_to_too_new_coords() {
+        let (responder, mut store, keychains) = setup();
+        let session_id = 2137;
+        let coord = UnitCoord::new(3, NodeIndex(1));
+        let units = random_full_parent_reconstrusted_units_up_to(
+            coord.round() - 1,
+            NODE_COUNT,
+            session_id,
+            &keychains,
+        );
+        for round_units in &units {
+            for unit in round_units {
+                store.insert(unit.clone());
+            }
+        }
+        let request = Request::Coord(coord);
+        match responder.handle_request(request, &store) {
+            Ok(response) => panic!("Unexpected response: {:?}.", response),
+            Err(err) => assert_eq!(err, Error::NoCanonicalAt(coord)),
+        }
+    }
+
+    #[test]
+    fn responds_to_parents_when_possible() {
+        let (responder, mut store, keychains) = setup();
+        let session_id = 2137;
+        let units =
+            random_full_parent_reconstrusted_units_up_to(5, NODE_COUNT, session_id, &keychains);
+        for round_units in &units {
+            for unit in round_units {
+                store.insert(unit.clone());
+            }
+        }
+        let requested_unit = units
+            .last()
+            .expect("just created this round")
+            .last()
+            .expect("the round has at least one unit")
+            .clone();
+        let request = Request::Parents(requested_unit.hash());
+        let response = responder
+            .handle_request(request, &store)
+            .expect("should successfully respond");
+        match response {
+            Response::Parents(response_hash, parents) => {
+                assert_eq!(response_hash, requested_unit.hash());
+                assert_eq!(parents.len(), requested_unit.parents().size().0);
+                for (parent, parent_hash) in zip(parents, requested_unit.parents().values()) {
+                    assert_eq!(&parent.as_signable().hash(), parent_hash);
+                }
+            }
+            other => panic!("Unexpected response: {:?}.", other),
+        }
+    }
+
+    #[test]
+    fn fails_to_respond_to_unknown_parents() {
+        let (responder, mut store, keychains) = setup();
+        let session_id = 2137;
+        let units =
+            random_full_parent_reconstrusted_units_up_to(5, NODE_COUNT, session_id, &keychains);
+        for round_units in &units {
+            for unit in round_units {
+                store.insert(unit.clone());
+            }
+        }
+        let hash =
+            random_full_parent_reconstrusted_units_up_to(1, NODE_COUNT, session_id, &keychains)
+                .last()
+                .expect("just created this round")
+                .last()
+                .expect("the round has at least one unit")
+                .hash();
+        let request = Request::Parents(hash);
+        match responder.handle_request(request, &store) {
+            Ok(response) => panic!("Unexpected response: {:?}.", response),
+            Err(err) => assert_eq!(err, Error::UnknownUnit(hash)),
+        }
+    }
+
+    #[test]
+    fn responds_to_existing_newest() {
+        let (responder, mut store, keychains) = setup();
+        let session_id = 2137;
+        let units =
+            random_full_parent_reconstrusted_units_up_to(5, NODE_COUNT, session_id, &keychains);
+        for round_units in &units {
+            for unit in round_units {
+                store.insert(unit.clone());
+            }
+        }
+        let requester = NodeIndex(1);
+        let request = Request::NewestUnit(requester, rand::random());
+        let response = responder
+            .handle_request(request, &store)
+            .expect("newest unit requests always get a response");
+        match response {
+            Response::NewestUnit(newest_unit_response) => {
+                let checked_newest_unit_response = newest_unit_response
+                    .check(&keychains[NODE_ID.0])
+                    .expect("should sign correctly");
+                assert_eq!(
+                    checked_newest_unit_response.as_signable().requester(),
+                    requester
+                );
+                // unfortunately there is no easy way to check whether the response contains a unit
+                // with its API :/
+            }
+            other => panic!("Unexpected response: {:?}.", other),
+        }
+    }
+}