wip: attempt to use upstream snap sync

core/blockchain_reader.go

@@ -247,6 +247,20 @@ func (bc *BlockChain) HasBlockAndState(hash common.Hash, number uint64) bool {
 	return bc.HasState(block.Root())
 }
 
+// ContractCodeWithPrefix retrieves a blob of data associated with a contract
+// hash either from ephemeral in-memory cache, or from persistent storage.
+//
+// If the code doesn't exist in the in-memory cache, check the storage with
+// new code scheme.
+func (bc *BlockChain) ContractCodeWithPrefix(hash common.Hash) ([]byte, error) {
+	type codeReader interface {
+		ContractCodeWithPrefix(address common.Address, codeHash common.Hash) ([]byte, error)
+	}
+	// TODO(rjl493456442) The associated account address is also required
+	// in Verkle scheme. Fix it once snap-sync is supported for Verkle.
+	return bc.stateCache.(codeReader).ContractCodeWithPrefix(common.Address{}, hash)
+}
+
 // State returns a new mutable state based on the current HEAD block.
 func (bc *BlockChain) State() (*state.StateDB, error) {
 	return bc.StateAt(bc.CurrentBlock().Root)

core/state/database.go

@@ -171,6 +171,10 @@ func (db *cachingDB) ContractCode(address common.Address, codeHash common.Hash)
 	return nil, errors.New("not found")
 }
 
+func (db *cachingDB) ContractCodeWithPrefix(address common.Address, codeHash common.Hash) ([]byte, error) {
+	return db.ContractCode(address, codeHash)
+}
+
 // ContractCodeSize retrieves a particular contracts code's size.
 func (db *cachingDB) ContractCodeSize(addr common.Address, codeHash common.Hash) (int, error) {
 	if cached, ok := db.codeSizeCache.Get(codeHash); ok {

eth/protocols/snap/discovery.go

@@ -0,0 +1,32 @@
+// Copyright 2020 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package snap
+
+import (
+	"github.com/ava-labs/libevm/rlp"
+)
+
+// enrEntry is the ENR entry which advertises `snap` protocol on the discovery.
+type enrEntry struct {
+	// Ignore additional fields (for forward compatibility).
+	Rest []rlp.RawValue `rlp:"tail"`
+}
+
+// ENRKey implements enr.Entry.
+func (e enrEntry) ENRKey() string {
+	return "snap"
+}