93 lines
3.4 KiB
Go
93 lines
3.4 KiB
Go
// Copyright (c) 2013-2017 The btcsuite developers
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// Use of this source code is governed by an ISC
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// license that can be found in the LICENSE file.
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package blockchain
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import (
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"fmt"
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"github.com/btcsuite/btcd/database"
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"github.com/btcsuite/btcutil"
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)
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// maybeAcceptBlock potentially accepts a block into the block chain and, if
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// accepted, returns whether or not it is on the main chain. It performs
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// several validation checks which depend on its position within the block chain
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// before adding it. The block is expected to have already gone through
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// ProcessBlock before calling this function with it.
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//
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// The flags are also passed to checkBlockContext and connectBestChain. See
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// their documentation for how the flags modify their behavior.
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//
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// This function MUST be called with the chain state lock held (for writes).
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func (b *BlockChain) maybeAcceptBlock(block *btcutil.Block, flags BehaviorFlags) (bool, error) {
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// The height of this block is one more than the referenced previous
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// block.
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prevHash := &block.MsgBlock().Header.PrevBlock
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prevNode := b.index.LookupNode(prevHash)
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if prevNode == nil {
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str := fmt.Sprintf("previous block %s is unknown", prevHash)
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return false, ruleError(ErrPreviousBlockUnknown, str)
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} else if b.index.NodeStatus(prevNode).KnownInvalid() {
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str := fmt.Sprintf("previous block %s is known to be invalid", prevHash)
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return false, ruleError(ErrInvalidAncestorBlock, str)
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}
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blockHeight := prevNode.height + 1
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block.SetHeight(blockHeight)
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// The block must pass all of the validation rules which depend on the
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// position of the block within the block chain.
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err := b.checkBlockContext(block, prevNode, flags)
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if err != nil {
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return false, err
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}
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// Insert the block into the database if it's not already there. Even
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// though it is possible the block will ultimately fail to connect, it
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// has already passed all proof-of-work and validity tests which means
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// it would be prohibitively expensive for an attacker to fill up the
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// disk with a bunch of blocks that fail to connect. This is necessary
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// since it allows block download to be decoupled from the much more
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// expensive connection logic. It also has some other nice properties
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// such as making blocks that never become part of the main chain or
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// blocks that fail to connect available for further analysis.
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err = b.db.Update(func(dbTx database.Tx) error {
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return dbStoreBlock(dbTx, block)
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})
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if err != nil {
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return false, err
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}
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// Create a new block node for the block and add it to the node index. Even
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// if the block ultimately gets connected to the main chain, it starts out
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// on a side chain.
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blockHeader := &block.MsgBlock().Header
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newNode := newBlockNode(blockHeader, prevNode)
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newNode.status = statusDataStored
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b.index.AddNode(newNode)
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err = b.index.flushToDB()
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if err != nil {
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return false, err
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}
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// Connect the passed block to the chain while respecting proper chain
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// selection according to the chain with the most proof of work. This
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// also handles validation of the transaction scripts.
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isMainChain, err := b.connectBestChain(newNode, block, flags)
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if err != nil {
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return false, err
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}
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// Notify the caller that the new block was accepted into the block
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// chain. The caller would typically want to react by relaying the
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// inventory to other peers.
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b.chainLock.Unlock()
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b.sendNotification(NTBlockAccepted, block)
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b.chainLock.Lock()
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return isMainChain, nil
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}
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