consortium/v2: add RPC API for querying finality vote easily (axieinf…

…inity#318)

This commit adds 2 APIs in consortiumv2 namespace:
consortiumv2_getValidatorAtHash, consortiumv2_getFinalityVoteAtHash.
consortiumv2_getValidatorAtHash returns the authorized validators that can seal
block hash with BLS public key. consortiumv2_getFinalityVoteAtHash returns the
finality vote information in the block header at block hash.

consensus/consortium/v2/api.go

@@ -0,0 +1,80 @@
+package v2
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/consensus"
+	consortiumCommon "github.com/ethereum/go-ethereum/consensus/consortium/common"
+	"github.com/ethereum/go-ethereum/consensus/consortium/v2/finality"
+)
+
+type consortiumV2Api struct {
+	chain      consensus.ChainHeaderReader
+	consortium *Consortium
+}
+
+// GetValidatorAtHash returns the authorized validators that can seal block hash with
+// their BLS public key if available
+func (api *consortiumV2Api) GetValidatorAtHash(hash common.Hash) ([]finality.ValidatorWithBlsPub, error) {
+	header := api.chain.GetHeaderByHash(hash)
+	if header == nil {
+		return nil, consortiumCommon.ErrUnknownBlock
+	}
+
+	snap, err := api.consortium.snapshot(api.chain, header.Number.Uint64()-1, header.ParentHash, nil)
+	if err != nil {
+		return nil, err
+	}
+
+	if snap.ValidatorsWithBlsPub != nil {
+		return snap.ValidatorsWithBlsPub, nil
+	}
+
+	var validators []finality.ValidatorWithBlsPub
+	for validator := range snap.Validators {
+		validators = append(validators, finality.ValidatorWithBlsPub{
+			Address: validator,
+		})
+	}
+
+	return validators, nil
+}
+
+type finalityVote struct {
+	Signature      string
+	VoterPublicKey []string
+	VoterAddress   []string
+}
+
+// GetFinalityVoteAtHash returns the finality vote at block hash
+func (api *consortiumV2Api) GetFinalityVoteAtHash(hash common.Hash) (*finalityVote, error) {
+	header := api.chain.GetHeaderByHash(hash)
+	if header == nil {
+		return nil, consortiumCommon.ErrUnknownBlock
+	}
+
+	isShillin := api.consortium.chainConfig.IsShillin(header.Number)
+	extraData, err := finality.DecodeExtra(header.Extra, isShillin)
+	if err != nil {
+		return nil, err
+	}
+
+	if extraData.HasFinalityVote == 0 {
+		return nil, nil
+	}
+
+	var vote finalityVote
+	vote.Signature = common.Bytes2Hex(extraData.AggregatedFinalityVotes.Marshal())
+
+	snap, err := api.consortium.snapshot(api.chain, header.Number.Uint64()-1, header.ParentHash, nil)
+	if err != nil {
+		return nil, err
+	}
+	position := extraData.FinalityVotedValidators.Indices()
+	for _, pos := range position {
+		validator := snap.ValidatorsWithBlsPub[pos]
+		vote.VoterAddress = append(vote.VoterAddress, validator.Address.Hex())
+		vote.VoterPublicKey = append(vote.VoterPublicKey, common.Bytes2Hex(validator.BlsPublicKey.Marshal()))
+	}
+
+	return &vote, nil
+}

consensus/consortium/v2/consortium.go

@@ -1021,7 +1021,14 @@ func (c *Consortium) Close() error {
 
 // APIs are backward compatible with the v1, so we do not to implement it again
 func (c *Consortium) APIs(chain consensus.ChainHeaderReader) []rpc.API {
-	return []rpc.API{}
+	return []rpc.API{
+		{
+			Namespace: "consortiumv2",
+			Version:   "1.0",
+			Service:   &consortiumV2Api{chain: chain, consortium: c},
+			Public:    false,
+		},
+	}
 }
 
 // CalcDifficulty is the difficulty adjustment algorithm. It returns the difficulty