babe: secondary blocks with VRF (#5501)

* babe: secondary blocks with VRF

* Fix node runtime compile

* Fix test-utils runtime interface

* Fix babe tests

* typo: v == 2

* babe: support online configuration upgrades

* Fix rpc tests

* Fix runtime version tests

* Switch to use NextConfigDescriptor instead of changing runtime interface

* Fix tests

* epoch-changes: map function that allows converting with different epoch types

* Add migration script for the epoch config change

* Fix docs for PrimaryAndSecondaryVRFSlots

* Add docs of `SecondaryVRF` in babe crate

* babe-primitives: Secondary -> SecondaryPlain

* babe-client: Secondary -> SecondaryPlain

* Fix migration tests

* test-utils-runtime: Secondary -> SecondaryPlain

* Fix missing name change in test-utils-runtime

* Fix migration: Epoch should be EpochV0

* Update client/consensus/babe/src/lib.rs

Co-Authored-By: André Silva <123550+andresilva@users.noreply.github.com>

* Fix new epochChanges version

* Fix babe-primitives naming changes

* Fix merge issues in babe-client

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>
Co-authored-by: André Silva <andre.beat@gmail.com>

substrate/primitives/consensus/babe/src/digests.rs

@@ -65,7 +65,7 @@ impl TryFrom<RawPrimaryPreDigest> for PrimaryPreDigest {
 
 /// BABE secondary slot assignment pre-digest.
 #[derive(Clone, RuntimeDebug, Encode, Decode)]
-pub struct SecondaryPreDigest {
+pub struct SecondaryPlainPreDigest {
 	/// Authority index
 	///
 	/// This is not strictly-speaking necessary, since the secondary slots
@@ -77,6 +77,37 @@ pub struct SecondaryPreDigest {
 	pub slot_number: SlotNumber,
 }
 
+/// BABE secondary deterministic slot assignment with VRF outputs.
+#[derive(Clone, RuntimeDebug, Encode, Decode)]
+pub struct RawSecondaryVRFPreDigest<VRFOutput=schnorrkel::RawVRFOutput, VRFProof=schnorrkel::RawVRFProof> {
+	/// Authority index
+	pub authority_index: super::AuthorityIndex,
+	/// Slot number
+	pub slot_number: SlotNumber,
+	/// VRF output
+	pub vrf_output: VRFOutput,
+	/// VRF proof
+	pub vrf_proof: VRFProof,
+}
+
+#[cfg(feature = "std")]
+/// BABE secondary slot assignment with VRF outputs pre-digest, for std environment.
+pub type SecondaryVRFPreDigest = RawSecondaryVRFPreDigest<schnorrkel::VRFOutput, schnorrkel::VRFProof>;
+
+#[cfg(feature = "std")]
+impl TryFrom<RawSecondaryVRFPreDigest> for SecondaryVRFPreDigest {
+	type Error = SignatureError;
+
+	fn try_from(raw: RawSecondaryVRFPreDigest) -> Result<SecondaryVRFPreDigest, SignatureError> {
+		Ok(SecondaryVRFPreDigest {
+			authority_index: raw.authority_index,
+			slot_number: raw.slot_number,
+			vrf_output: raw.vrf_output.try_into()?,
+			vrf_proof: raw.vrf_proof.try_into()?,
+		})
+	}
+}
+
 /// A BABE pre-runtime digest. This contains all data required to validate a
 /// block and for the BABE runtime module. Slots can be assigned to a primary
 /// (VRF based) and to a secondary (slot number based).
@@ -87,7 +118,10 @@ pub enum RawPreDigest<VRFOutput=schnorrkel::RawVRFOutput, VRFProof=schnorrkel::R
 	Primary(RawPrimaryPreDigest<VRFOutput, VRFProof>),
 	/// A secondary deterministic slot assignment.
 	#[codec(index = "2")]
-	Secondary(SecondaryPreDigest),
+	SecondaryPlain(SecondaryPlainPreDigest),
+	/// A secondary deterministic slot assignment with VRF outputs.
+	#[codec(index = "3")]
+	SecondaryVRF(RawSecondaryVRFPreDigest<VRFOutput, VRFProof>),
 }
 
 #[cfg(feature = "std")]
@@ -99,7 +133,8 @@ impl<VRFOutput, VRFProof> RawPreDigest<VRFOutput, VRFProof> {
 	pub fn authority_index(&self) -> AuthorityIndex {
 		match self {
 			RawPreDigest::Primary(primary) => primary.authority_index,
-			RawPreDigest::Secondary(secondary) => secondary.authority_index,
+			RawPreDigest::SecondaryPlain(secondary) => secondary.authority_index,
+			RawPreDigest::SecondaryVRF(secondary) => secondary.authority_index,
 		}
 	}
 
@@ -107,7 +142,8 @@ impl<VRFOutput, VRFProof> RawPreDigest<VRFOutput, VRFProof> {
 	pub fn slot_number(&self) -> SlotNumber {
 		match self {
 			RawPreDigest::Primary(primary) => primary.slot_number,
-			RawPreDigest::Secondary(secondary) => secondary.slot_number,
+			RawPreDigest::SecondaryPlain(secondary) => secondary.slot_number,
+			RawPreDigest::SecondaryVRF(secondary) => secondary.slot_number,
 		}
 	}
 
@@ -116,7 +152,7 @@ impl<VRFOutput, VRFProof> RawPreDigest<VRFOutput, VRFProof> {
 	pub fn added_weight(&self) -> crate::BabeBlockWeight {
 		match self {
 			RawPreDigest::Primary(_) => 1,
-			RawPreDigest::Secondary(_) => 0,
+			RawPreDigest::SecondaryPlain(_) | RawPreDigest::SecondaryVRF(_) => 0,
 		}
 	}
 }
@@ -128,7 +164,8 @@ impl TryFrom<RawPreDigest> for PreDigest {
 	fn try_from(raw: RawPreDigest) -> Result<PreDigest, SignatureError> {
 		Ok(match raw {
 			RawPreDigest::Primary(primary) => PreDigest::Primary(primary.try_into()?),
-			RawPreDigest::Secondary(secondary) => PreDigest::Secondary(secondary),
+			RawPreDigest::SecondaryPlain(secondary) => PreDigest::SecondaryPlain(secondary),
+			RawPreDigest::SecondaryVRF(secondary) => PreDigest::SecondaryVRF(secondary.try_into()?),
 		})
 	}
 }

substrate/primitives/consensus/babe/src/lib.rs

@@ -95,7 +95,7 @@ pub enum ConsensusLog {
 
 /// Configuration data used by the BABE consensus engine.
 #[derive(Clone, PartialEq, Eq, Encode, Decode, RuntimeDebug)]
-pub struct BabeGenesisConfiguration {
+pub struct BabeGenesisConfigurationV1 {
 	/// The slot duration in milliseconds for BABE. Currently, only
 	/// the value provided by this type at genesis will be used.
 	///
@@ -124,6 +124,76 @@ pub struct BabeGenesisConfiguration {
 	pub secondary_slots: bool,
 }
 
+impl From<BabeGenesisConfigurationV1> for BabeGenesisConfiguration {
+	fn from(v1: BabeGenesisConfigurationV1) -> Self {
+		Self {
+			slot_duration: v1.slot_duration,
+			epoch_length: v1.epoch_length,
+			c: v1.c,
+			genesis_authorities: v1.genesis_authorities,
+			randomness: v1.randomness,
+			allowed_slots: if v1.secondary_slots {
+				AllowedSlots::PrimaryAndSecondaryPlainSlots
+			} else {
+				AllowedSlots::PrimarySlots
+			},
+		}
+	}
+}
+
+/// Configuration data used by the BABE consensus engine.
+#[derive(Clone, PartialEq, Eq, Encode, Decode, RuntimeDebug)]
+pub struct BabeGenesisConfiguration {
+	/// The slot duration in milliseconds for BABE. Currently, only
+	/// the value provided by this type at genesis will be used.
+	///
+	/// Dynamic slot duration may be supported in the future.
+	pub slot_duration: u64,
+
+	/// The duration of epochs in slots.
+	pub epoch_length: SlotNumber,
+
+	/// A constant value that is used in the threshold calculation formula.
+	/// Expressed as a rational where the first member of the tuple is the
+	/// numerator and the second is the denominator. The rational should
+	/// represent a value between 0 and 1.
+	/// In the threshold formula calculation, `1 - c` represents the probability
+	/// of a slot being empty.
+	pub c: (u64, u64),
+
+	/// The authorities for the genesis epoch.
+	pub genesis_authorities: Vec<(AuthorityId, BabeAuthorityWeight)>,
+
+	/// The randomness for the genesis epoch.
+	pub randomness: Randomness,
+
+	/// Type of allowed slots.
+	pub allowed_slots: AllowedSlots,
+}
+
+/// Types of allowed slots.
+#[derive(Clone, Copy, PartialEq, Eq, Encode, Decode, RuntimeDebug)]
+pub enum AllowedSlots {
+	/// Only allow primary slots.
+	PrimarySlots,
+	/// Allow primary and secondary plain slots.
+	PrimaryAndSecondaryPlainSlots,
+	/// Allow primary and secondary VRF slots.
+	PrimaryAndSecondaryVRFSlots,
+}
+
+impl AllowedSlots {
+	/// Whether plain secondary slots are allowed.
+	pub fn is_secondary_plain_slots_allowed(&self) -> bool {
+		*self == Self::PrimaryAndSecondaryPlainSlots
+	}
+
+	/// Whether VRF secondary slots are allowed.
+	pub fn is_secondary_vrf_slots_allowed(&self) -> bool {
+		*self == Self::PrimaryAndSecondaryVRFSlots
+	}
+}
+
 #[cfg(feature = "std")]
 impl sp_consensus::SlotData for BabeGenesisConfiguration {
 	fn slot_duration(&self) -> u64 {
@@ -146,15 +216,20 @@ pub struct BabeEpochConfiguration {
 
 	/// Whether this chain should run with secondary slots, which are assigned
 	/// in round-robin manner.
-	pub secondary_slots: bool,
+	pub allowed_slots: AllowedSlots,
 }
 
 sp_api::decl_runtime_apis! {
 	/// API necessary for block authorship with BABE.
+	#[api_version(2)]
 	pub trait BabeApi {
 		/// Return the genesis configuration for BABE. The configuration is only read on genesis.
 		fn configuration() -> BabeGenesisConfiguration;
 
+		/// Return the configuration for BABE. Version 1.
+		#[changed_in(2)]
+		fn configuration() -> BabeGenesisConfigurationV1;
+
 		/// Returns the slot number that started the current epoch.
 		fn current_epoch_start() -> SlotNumber;
 	}