core, consensus: pluggable consensus engines (#3817)

This commit adds pluggable consensus engines to go-ethereum. In short, it
introduces a generic consensus interface, and refactors the entire codebase to
use this interface.

2 files changed, 128 insertions, 0 deletions

diff --git a/consensus/misc/dao.go b/consensus/misc/dao.go
new file mode 100644
index 000000000..67d4adb44
--- /dev/null
+++ b/consensus/misc/dao.go
@@ -0,0 +1,85 @@
+// Copyright 2016 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 misc
+
+import (
+	"bytes"
+	"errors"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/core/state"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+var (
+	// ErrBadProDAOExtra is returned if a header doens't support the DAO fork on a
+	// pro-fork client.
+	ErrBadProDAOExtra = errors.New("bad DAO pro-fork extra-data")
+
+	// ErrBadNoDAOExtra is returned if a header does support the DAO fork on a no-
+	// fork client.
+	ErrBadNoDAOExtra = errors.New("bad DAO no-fork extra-data")
+)
+
+// VerifyDAOHeaderExtraData validates the extra-data field of a block header to
+// ensure it conforms to DAO hard-fork rules.
+//
+// DAO hard-fork extension to the header validity:
+//   a) if the node is no-fork, do not accept blocks in the [fork, fork+10) range
+//      with the fork specific extra-data set
+//   b) if the node is pro-fork, require blocks in the specific range to have the
+//      unique extra-data set.
+func VerifyDAOHeaderExtraData(config *params.ChainConfig, header *types.Header) error {
+	// Short circuit validation if the node doesn't care about the DAO fork
+	if config.DAOForkBlock == nil {
+		return nil
+	}
+	// Make sure the block is within the fork's modified extra-data range
+	limit := new(big.Int).Add(config.DAOForkBlock, params.DAOForkExtraRange)
+	if header.Number.Cmp(config.DAOForkBlock) < 0 || header.Number.Cmp(limit) >= 0 {
+		return nil
+	}
+	// Depending whether we support or oppose the fork, validate the extra-data contents
+	if config.DAOForkSupport {
+		if !bytes.Equal(header.Extra, params.DAOForkBlockExtra) {
+			return ErrBadProDAOExtra
+		}
+	} else {
+		if bytes.Equal(header.Extra, params.DAOForkBlockExtra) {
+			return ErrBadNoDAOExtra
+		}
+	}
+	// All ok, header has the same extra-data we expect
+	return nil
+}
+
+// ApplyDAOHardFork modifies the state database according to the DAO hard-fork
+// rules, transferring all balances of a set of DAO accounts to a single refund
+// contract.
+func ApplyDAOHardFork(statedb *state.StateDB) {
+	// Retrieve the contract to refund balances into
+	if !statedb.Exist(params.DAORefundContract) {
+		statedb.CreateAccount(params.DAORefundContract)
+	}
+
+	// Move every DAO account and extra-balance account funds into the refund contract
+	for _, addr := range params.DAODrainList() {
+		statedb.AddBalance(params.DAORefundContract, statedb.GetBalance(addr))
+		statedb.SetBalance(addr, new(big.Int))
+	}
+}
diff --git a/consensus/misc/forks.go b/consensus/misc/forks.go
new file mode 100644
index 000000000..4a5e7c37e
--- /dev/null
+++ b/consensus/misc/forks.go
@@ -0,0 +1,43 @@
+// Copyright 2017 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 misc
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
+	"github.com/ethereum/go-ethereum/params"
+)
+
+// VerifyForkHashes verifies that blocks conforming to network hard-forks do have
+// the correct hashes, to avoid clients going off on different chains. This is an
+// optional feature.
+func VerifyForkHashes(config *params.ChainConfig, header *types.Header, uncle bool) error {
+	// We don't care about uncles
+	if uncle {
+		return nil
+	}
+	// If the homestead reprice hash is set, validate it
+	if config.EIP150Block != nil && config.EIP150Block.Cmp(header.Number) == 0 {
+		if config.EIP150Hash != (common.Hash{}) && config.EIP150Hash != header.Hash() {
+			return fmt.Errorf("homestead gas reprice fork: have 0x%x, want 0x%x", header.Hash(), config.EIP150Hash)
+		}
+	}
+	// All ok, return
+	return nil
+}