feat(lib/grandpa): Add warp sync provider (#4187)

dot/state/grandpa.go

@@ -7,6 +7,7 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"slices"
 	"strconv"
 
 	"github.com/ChainSafe/gossamer/dot/telemetry"
@@ -37,7 +38,7 @@ var (
 
 // GrandpaState tracks information related to grandpa
 type GrandpaState struct {
-	db         GetPutDeleter
+	db         GrandpaDatabase
 	blockState *BlockState
 
 	forcedChanges        *orderedPendingChanges
@@ -602,3 +603,23 @@ func (s *GrandpaState) GetPrecommits(round, setID uint64) ([]types.GrandpaSigned
 
 	return pcs, nil
 }
+
+// GetAuthoritiesChangesFromBlock retrieves blocks numbers where authority set changes happened
+func (s *GrandpaState) GetAuthoritiesChangesFromBlock(initialBlockNumber uint) ([]uint, error) {
+	blockNumbers := make([]uint, 0)
+	iter, err := s.db.NewPrefixIterator(setIDChangePrefix)
+	if err != nil {
+		return nil, err
+	}
+
+	for iter.Next() {
+		blockNumber := common.BytesToUint(iter.Value())
+		if blockNumber >= initialBlockNumber {
+			blockNumbers = append(blockNumbers, blockNumber)
+		}
+	}
+
+	// To ensure the order of the blocks
+	slices.Sort(blockNumbers)
+	return blockNumbers, nil
+}

dot/state/interfaces.go

@@ -10,6 +10,11 @@ import (
 	"github.com/ChainSafe/gossamer/internal/database"
 )
 
+type GrandpaDatabase interface {
+	GetPutDeleter
+	NewPrefixIterator(prefix []byte) (database.Iterator, error)
+}
+
 // GetPutDeleter has methods to get, put and delete key values.
 type GetPutDeleter interface {
 	GetPutter

internal/client/consensus/grandpa/mocks_generate_test.go

@@ -0,0 +1,6 @@
+// Copyright 2021 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
+package grandpa
+
+//go:generate mockgen -destination=mocks_test.go -package $GOPACKAGE . BlockState,GrandpaState

internal/client/consensus/grandpa/warp_sync.go

@@ -0,0 +1,173 @@
+// Copyright 2024 ChainSafe Systems (ON)
+// SPDX-License-Identifier: LGPL-3.0-only
+
+package grandpa
+
+import (
+	"fmt"
+
+	"github.com/ChainSafe/gossamer/dot/types"
+	"github.com/ChainSafe/gossamer/internal/primitives/core/hash"
+	"github.com/ChainSafe/gossamer/internal/primitives/runtime"
+	"github.com/ChainSafe/gossamer/lib/common"
+	"github.com/ChainSafe/gossamer/pkg/scale"
+)
+
+const MaxWarpSyncProofSize = 8 * 1024 * 1024
+
+var (
+	errMissingStartBlock      = fmt.Errorf("missing start block")
+	errStartBlockNotFinalized = fmt.Errorf("start block is not finalized")
+)
+
+type BlockState interface {
+	GetHeader(hash common.Hash) (*types.Header, error)
+	GetHighestFinalisedHeader() (*types.Header, error)
+	GetHeaderByNumber(num uint) (*types.Header, error)
+	GetJustification(hash common.Hash) ([]byte, error)
+}
+
+type GrandpaState interface {
+	GetAuthoritiesChangesFromBlock(blockNumber uint) ([]uint, error)
+}
+
+type WarpSyncFragment struct {
+	// The last block that the given authority set finalized. This block should contain a digest
+	// signalling an authority set change from which we can fetch the next authority set.
+	Header types.Header
+	// A justification for the header above which proves its finality. In order to validate it the
+	// verifier must be aware of the authorities and set id for which the justification refers to.
+	Justification GrandpaJustification[hash.H256, uint64]
+}
+
+type WarpSyncProof struct {
+	Proofs []WarpSyncFragment
+	// indicates whether the warp sync has been completed
+	IsFinished   bool
+	proofsLength int
+}
+
+func NewWarpSyncProof() WarpSyncProof {
+	return WarpSyncProof{
+		Proofs:       make([]WarpSyncFragment, 0),
+		IsFinished:   false,
+		proofsLength: 0,
+	}
+}
+
+func (w *WarpSyncProof) addFragment(fragment WarpSyncFragment) (limitReached bool, err error) {
+	encodedFragment, err := scale.Marshal(fragment)
+	if err != nil {
+		return false, err
+	}
+
+	if w.proofsLength+len(encodedFragment) >= MaxWarpSyncProofSize {
+		return true, nil
+	}
+
+	w.proofsLength += len(encodedFragment)
+	w.Proofs = append(w.Proofs, fragment)
+
+	return false, nil
+}
+
+func (w *WarpSyncProof) lastProofBlockNumber() uint64 {
+	if len(w.Proofs) == 0 {
+		return 0
+	}
+	return w.Proofs[len(w.Proofs)-1].Justification.Justification.Commit.TargetNumber + 1
+}
+
+type WarpSyncProofProvider struct {
+	blockState   BlockState
+	grandpaState GrandpaState
+}
+
+// Generate build a warp sync encoded proof starting from the given block hash
+func (np *WarpSyncProofProvider) Generate(start common.Hash) ([]byte, error) {
+	// Get and traverse all GRANDPA authorities changes from the given block hash
+	beginBlockHeader, err := np.blockState.GetHeader(start)
+	if err != nil {
+		return nil, fmt.Errorf("%w: %w", errMissingStartBlock, err)
+	}
+
+	lastFinalizedBlockHeader, err := np.blockState.GetHighestFinalisedHeader()
+	if err != nil {
+		return nil, fmt.Errorf("getting best block header: %w", err)
+	}
+
+	if beginBlockHeader.Number > lastFinalizedBlockHeader.Number {
+		return nil, errStartBlockNotFinalized
+	}
+
+	authoritySetChanges, err := np.grandpaState.GetAuthoritiesChangesFromBlock(beginBlockHeader.Number)
+	if err != nil {
+		return nil, err
+	}
+
+	limitReached := false
+	finalProof := NewWarpSyncProof()
+	for _, blockNumber := range authoritySetChanges {
+		header, err := np.blockState.GetHeaderByNumber(blockNumber)
+		if err != nil {
+			return nil, err
+		}
+
+		encJustification, err := np.blockState.GetJustification(header.Hash()) // get the justification of such block
+		if err != nil {
+			return nil, err
+		}
+
+		justification, err := decodeJustification[hash.H256, uint64, runtime.BlakeTwo256](encJustification)
+		if err != nil {
+			return nil, err
+		}
+
+		fragment := WarpSyncFragment{Header: *header, Justification: *justification}
+
+		// check the proof size
+		limitReached, err = finalProof.addFragment(fragment)
+		if err != nil {
+			return nil, err
+		}
+
+		if limitReached {
+			break
+		}
+	}
+
+	// If the limit is not reached then retrieve the latest (best) justification
+	// and append in the proofs
+	if !limitReached {
+		// the existing best justification must be for a block higher than the
+		// last authority set change. if we didn't prove any authority set
+		// change then we fallback to make sure it's higher or equal to the
+		// initial warp sync block.
+		lastFinalizedBlockHeader, err := np.blockState.GetHighestFinalisedHeader()
+		if err != nil {
+			return nil, fmt.Errorf("getting best block header: %w", err)
+		}
+		latestJustification, err := np.blockState.GetJustification(lastFinalizedBlockHeader.Hash())
+		if err != nil {
+			return nil, err
+		}
+
+		justification, err := decodeJustification[hash.H256, uint64, runtime.BlakeTwo256](latestJustification)
+		if err != nil {
+			return nil, err
+		}
+
+		if justification.Justification.Commit.TargetNumber >= finalProof.lastProofBlockNumber() {
+			fragment := WarpSyncFragment{Header: *lastFinalizedBlockHeader, Justification: *justification}
+			_, err = finalProof.addFragment(fragment)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		finalProof.IsFinished = true
+	}
+
+	// Encode and return the proof
+	return scale.Marshal(finalProof)
+}