babe: report equivocations (#6362)

* slots: create primitives crate for consensus slots

* offences: add method to check if an offence is unknown

* babe: initial equivocation reporting implementation

* babe: organize imports

* babe: working equivocation reporting

* babe: add slot number to equivocation proof

* session: move duplicate traits to session primitives

* babe: move equivocation stuff to its own file

* offences: fix test

* session: don't have primitives depend on frame_support

* babe: use opaque type for key owner proof

* babe: cleanup client equivocation reporting

* babe: cleanup equivocation code in pallet

* babe: allow sending signed equivocation reports

* node: fix compilation

* fix test compilation

* babe: return bool on check_equivocation_proof

* babe: add test for equivocation reporting

* babe: add more tests

* babe: add test for validate unsigned

* babe: take slot number in generate_key_ownership_proof API

* babe: add benchmark for equivocation proof checking

* session: add benchmark for membership proof checking

* offences: fix babe benchmark

* babe: add weights based on benchmark results

* babe: adjust weights after benchmarking on reference hardware

* babe: reorder checks in check_and_report_equivocation

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

@@ -0,0 +1,41 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2020 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Primitives for slots-based consensus engines.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use codec::{Decode, Encode};
+
+/// A slot number.
+pub type SlotNumber = u64;
+
+/// Represents an equivocation proof. An equivocation happens when a validator
+/// produces more than one block on the same slot. The proof of equivocation
+/// are the given distinct headers that were signed by the validator and which
+/// include the slot number.
+#[derive(Clone, Debug, Decode, Encode, PartialEq)]
+pub struct EquivocationProof<Header, Id> {
+	/// Returns the authority id of the equivocator.
+	pub offender: Id,
+	/// The slot number at which the equivocation happened.
+	pub slot_number: SlotNumber,
+	/// The first header involved in the equivocation.
+	pub first_header: Header,
+	/// The second header involved in the equivocation.
+	pub second_header: Header,
+}