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manager.go
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// Copyright (c) 2013-2017 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.
package netsync
import (
"container/list"
"math/rand"
"net"
"sync"
"sync/atomic"
"time"
"github.com/gcash/bchd/blockchain"
"github.com/gcash/bchd/chaincfg"
"github.com/gcash/bchd/chaincfg/chainhash"
"github.com/gcash/bchd/database"
"github.com/gcash/bchd/mempool"
peerpkg "github.com/gcash/bchd/peer"
"github.com/gcash/bchd/wire"
"github.com/gcash/bchutil"
)
const (
// minInFlightBlocks is the minimum number of blocks that should be
// in the request queue for headers-first mode before requesting
// more.
minInFlightBlocks = 10
// maxNetworkViolations is the max number of network violations a
// sync peer can have before a new sync peer is found.
maxNetworkViolations = 3
// maxRejectedTxns is the maximum number of rejected transactions
// hashes to store in memory.
maxRejectedTxns = 1000
// maxRequestedBlocks is the maximum number of requested block
// hashes to store in memory.
maxRequestedBlocks = wire.MaxInvPerMsg
// maxRequestedTxns is the maximum number of requested transactions
// hashes to store in memory.
maxRequestedTxns = wire.MaxInvPerMsg
// maxLastBlockTime is the longest time in seconds that we will
// stay with a sync peer while below the current blockchain height.
// Set to 3 minutes.
maxLastBlockTime = 60 * 3 * time.Second
// syncPeerTickerInterval is how often we check the current
// syncPeer. Set to 30 seconds.
syncPeerTickerInterval = 30 * time.Second
)
// zeroHash is the zero value hash (all zeros). It is defined as a convenience.
var zeroHash chainhash.Hash
// newPeerMsg signifies a newly connected peer to the block handler.
type newPeerMsg struct {
peer *peerpkg.Peer
reply chan struct{}
}
// blockMsg packages a bitcoin block message and the peer it came from together
// so the block handler has access to that information.
type blockMsg struct {
block *bchutil.Block
peer *peerpkg.Peer
reply chan struct{}
}
// invMsg packages a bitcoin inv message and the peer it came from together
// so the block handler has access to that information.
type invMsg struct {
inv *wire.MsgInv
peer *peerpkg.Peer
}
// headersMsg packages a bitcoin headers message and the peer it came from
// together so the block handler has access to that information.
type headersMsg struct {
headers *wire.MsgHeaders
peer *peerpkg.Peer
}
// donePeerMsg signifies a newly disconnected peer to the block handler.
type donePeerMsg struct {
peer *peerpkg.Peer
reply chan struct{}
}
// txMsg packages a bitcoin tx message and the peer it came from together
// so the block handler has access to that information.
type txMsg struct {
tx *bchutil.Tx
peer *peerpkg.Peer
reply chan struct{}
}
// getSyncPeerMsg is a message type to be sent across the message channel for
// retrieving the current sync peer.
type getSyncPeerMsg struct {
reply chan int32
}
// processBlockResponse is a response sent to the reply channel of a
// processBlockMsg.
type processBlockResponse struct {
isOrphan bool
err error
}
// processBlockMsg is a message type to be sent across the message channel
// for requested a block is processed. Note this call differs from blockMsg
// above in that blockMsg is intended for blocks that came from peers and have
// extra handling whereas this message essentially is just a concurrent safe
// way to call ProcessBlock on the internal block chain instance.
type processBlockMsg struct {
block *bchutil.Block
flags blockchain.BehaviorFlags
reply chan processBlockResponse
}
// isCurrentMsg is a message type to be sent across the message channel for
// requesting whether or not the sync manager believes it is synced with the
// currently connected peers.
type isCurrentMsg struct {
reply chan bool
}
// pauseMsg is a message type to be sent across the message channel for
// pausing the sync manager. This effectively provides the caller with
// exclusive access over the manager until a receive is performed on the
// unpause channel.
type pauseMsg struct {
unpause <-chan struct{}
}
// headerNode is used as a node in a list of headers that are linked together
// between checkpoints.
type headerNode struct {
height int32
hash *chainhash.Hash
}
// peerSyncState stores additional information that the SyncManager tracks
// about a peer.
type peerSyncState struct {
syncCandidate bool
requestQueue []*wire.InvVect
requestedTxns map[chainhash.Hash]struct{}
requestedBlocks map[chainhash.Hash]struct{}
}
// syncPeerState stores additional info about the sync peer.
type syncPeerState struct {
recvBytes uint64
recvBytesLastTick uint64
lastBlockTime time.Time
violations int
ticks uint64
}
// validNetworkSpeed checks if the peer is slow and
// returns an integer representing the number of network
// violations the sync peer has.
func (sps *syncPeerState) validNetworkSpeed(minSyncPeerNetworkSpeed uint64) int {
// Fresh sync peer. We need another tick.
if sps.ticks == 0 {
return 0
}
// Number of bytes received in the last tick.
recvDiff := sps.recvBytes - sps.recvBytesLastTick
// If the peer was below the threshold, mark a violation and return.
if recvDiff/uint64(syncPeerTickerInterval.Seconds()) < minSyncPeerNetworkSpeed {
sps.violations++
return sps.violations
}
// No violation found, reset the violation counter.
sps.violations = 0
return sps.violations
}
// updateNetwork updates the received bytes. Just tracks 2 ticks
// worth of network bandwidth.
func (sps *syncPeerState) updateNetwork(syncPeer *peerpkg.Peer) {
sps.ticks++
sps.recvBytesLastTick = sps.recvBytes
sps.recvBytes = syncPeer.BytesReceived()
}
// SyncManager is used to communicate block related messages with peers. The
// SyncManager is started as by executing Start() in a goroutine. Once started,
// it selects peers to sync from and starts the initial block download. Once the
// chain is in sync, the SyncManager handles incoming block and header
// notifications and relays announcements of new blocks to peers.
type SyncManager struct {
peerNotifier PeerNotifier
started int32
shutdown int32
chain *blockchain.BlockChain
txMemPool *mempool.TxPool
chainParams *chaincfg.Params
progressLogger *blockProgressLogger
msgChan chan interface{}
wg sync.WaitGroup
quit chan struct{}
// These fields should only be accessed from the blockHandler thread.
rejectedTxns map[chainhash.Hash]struct{}
requestedTxns map[chainhash.Hash]struct{}
requestedBlocks map[chainhash.Hash]struct{}
syncPeer *peerpkg.Peer
syncPeerState *syncPeerState
peerStates map[*peerpkg.Peer]*peerSyncState
// The following fields are used for headers-first mode.
headersFirstMode bool
headerList *list.List
startHeader *list.Element
nextCheckpoint *chaincfg.Checkpoint
// An optional fee estimator.
feeEstimator *mempool.FeeEstimator
// minSyncPeerNetworkSpeed is the minimum speed allowed for
// a sync peer.
minSyncPeerNetworkSpeed uint64
}
// resetHeaderState sets the headers-first mode state to values appropriate for
// syncing from a new peer.
func (sm *SyncManager) resetHeaderState(newestHash *chainhash.Hash, newestHeight int32) {
sm.headersFirstMode = false
sm.headerList.Init()
sm.startHeader = nil
// When there is a next checkpoint, add an entry for the latest known
// block into the header pool. This allows the next downloaded header
// to prove it links to the chain properly.
if sm.nextCheckpoint != nil {
node := headerNode{height: newestHeight, hash: newestHash}
sm.headerList.PushBack(&node)
}
}
// findNextHeaderCheckpoint returns the next checkpoint after the passed height.
// It returns nil when there is not one either because the height is already
// later than the final checkpoint or some other reason such as disabled
// checkpoints.
func (sm *SyncManager) findNextHeaderCheckpoint(height int32) *chaincfg.Checkpoint {
checkpoints := sm.chain.Checkpoints()
if len(checkpoints) == 0 {
return nil
}
// There is no next checkpoint if the height is already after the final
// checkpoint.
finalCheckpoint := &checkpoints[len(checkpoints)-1]
if height >= finalCheckpoint.Height {
return nil
}
// Find the next checkpoint.
nextCheckpoint := finalCheckpoint
for i := len(checkpoints) - 2; i >= 0; i-- {
if height >= checkpoints[i].Height {
break
}
nextCheckpoint = &checkpoints[i]
}
return nextCheckpoint
}
// startSync will choose the best peer among the available candidate peers to
// download/sync the blockchain from. When syncing is already running, it
// simply returns. It also examines the candidates for any which are no longer
// candidates and removes them as needed.
func (sm *SyncManager) startSync() {
// Return now if we're already syncing.
if sm.syncPeer != nil {
return
}
best := sm.chain.BestSnapshot()
bestPeers := []*peerpkg.Peer{}
okPeers := []*peerpkg.Peer{}
for peer, state := range sm.peerStates {
if !state.syncCandidate {
continue
}
// Add any peers on the same block to okPeers. These should
// only be used as a last resort.
if peer.LastBlock() == best.Height {
okPeers = append(okPeers, peer)
continue
}
// Remove sync candidate peers that are no longer candidates due
// to passing their latest known block.
if peer.LastBlock() < best.Height {
state.syncCandidate = false
continue
}
// Append each good peer to bestPeers for selection later.
bestPeers = append(bestPeers, peer)
}
var bestPeer *peerpkg.Peer
// Try to select a random peer that is at a higher block height,
// if that is not available then use a random peer at the same
// height and hope they find blocks.
if len(bestPeers) > 0 {
bestPeer = bestPeers[rand.Intn(len(bestPeers))]
} else if len(okPeers) > 0 {
bestPeer = okPeers[rand.Intn(len(okPeers))]
}
// Start syncing from the best peer if one was selected.
if bestPeer != nil {
// Clear the requestedBlocks if the sync peer changes, otherwise
// we may ignore blocks we need that the last sync peer failed
// to send.
sm.requestedBlocks = make(map[chainhash.Hash]struct{})
locator, err := sm.chain.LatestBlockLocator()
if err != nil {
log.Errorf("Failed to get block locator for the "+
"latest block: %v", err)
return
}
log.Infof("Syncing to block height %d from peer %v",
bestPeer.LastBlock(), bestPeer.Addr())
// When the current height is less than a known checkpoint we
// can use block headers to learn about which blocks comprise
// the chain up to the checkpoint and perform less validation
// for them. This is possible since each header contains the
// hash of the previous header and a merkle root. Therefore if
// we validate all of the received headers link together
// properly and the checkpoint hashes match, we can be sure the
// hashes for the blocks in between are accurate. Further, once
// the full blocks are downloaded, the merkle root is computed
// and compared against the value in the header which proves the
// full block hasn't been tampered with.
//
// Once we have passed the final checkpoint, or checkpoints are
// disabled, use standard inv messages learn about the blocks
// and fully validate them. Finally, regression test mode does
// not support the headers-first approach so do normal block
// downloads when in regression test mode.
if sm.nextCheckpoint != nil &&
best.Height < sm.nextCheckpoint.Height &&
sm.chainParams != &chaincfg.RegressionNetParams {
bestPeer.PushGetHeadersMsg(locator, sm.nextCheckpoint.Hash)
sm.headersFirstMode = true
log.Infof("Downloading headers for blocks %d to "+
"%d from peer %s", best.Height+1,
sm.nextCheckpoint.Height, bestPeer.Addr())
} else {
bestPeer.PushGetBlocksMsg(locator, &zeroHash)
}
bestPeer.SetSyncPeer(true)
sm.syncPeer = bestPeer
sm.syncPeerState = &syncPeerState{
lastBlockTime: time.Now(),
recvBytes: bestPeer.BytesReceived(),
recvBytesLastTick: uint64(0),
}
} else {
log.Warnf("No sync peer candidates available")
}
}
// SyncHeight returns latest known block being synced to.
func (sm *SyncManager) SyncHeight() uint64 {
if sm.syncPeer == nil {
return 0
}
return uint64(sm.topBlock())
}
// isSyncCandidate returns whether or not the peer is a candidate to consider
// syncing from.
func (sm *SyncManager) isSyncCandidate(peer *peerpkg.Peer) bool {
// Typically a peer is not a candidate for sync if it's not a full node,
// however regression test is special in that the regression tool is
// not a full node and still needs to be considered a sync candidate.
if sm.chainParams == &chaincfg.RegressionNetParams {
// The peer is not a candidate if it's not coming from localhost
// or the hostname can't be determined for some reason.
host, _, err := net.SplitHostPort(peer.Addr())
if err != nil {
return false
}
if host != "127.0.0.1" && host != "localhost" {
return false
}
} else {
// The peer is not a candidate for sync if it's not a full
// node.
nodeServices := peer.Services()
if nodeServices&wire.SFNodeNetwork != wire.SFNodeNetwork {
return false
}
}
// Candidate if all checks passed.
return true
}
// handleNewPeerMsg deals with new peers that have signalled they may
// be considered as a sync peer (they have already successfully negotiated). It
// also starts syncing if needed. It is invoked from the syncHandler goroutine.
func (sm *SyncManager) handleNewPeerMsg(peer *peerpkg.Peer) {
// Ignore if in the process of shutting down.
if atomic.LoadInt32(&sm.shutdown) != 0 {
return
}
log.Infof("New valid peer %s (%s)", peer, peer.UserAgent())
// Initialize the peer state
isSyncCandidate := sm.isSyncCandidate(peer)
sm.peerStates[peer] = &peerSyncState{
syncCandidate: isSyncCandidate,
requestedTxns: make(map[chainhash.Hash]struct{}),
requestedBlocks: make(map[chainhash.Hash]struct{}),
}
// Start syncing by choosing the best candidate if needed.
if isSyncCandidate && sm.syncPeer == nil {
sm.startSync()
}
}
// handleCheckSyncPeer selects a new sync peer.
func (sm *SyncManager) handleCheckSyncPeer() {
if atomic.LoadInt32(&sm.shutdown) != 0 {
return
}
// If we don't have a sync peer, then there is nothing to do.
if sm.syncPeer == nil {
return
}
// Update network stats at the end of this tick.
defer sm.syncPeerState.updateNetwork(sm.syncPeer)
// Check network speed of the sync peer and its last block time. If we're currently
// flushing the cache skip this round.
if (sm.syncPeerState.validNetworkSpeed(sm.minSyncPeerNetworkSpeed) < maxNetworkViolations) &&
(time.Since(sm.syncPeerState.lastBlockTime) <= maxLastBlockTime) {
return
}
// Don't update sync peers if you have all the available
// blocks.
best := sm.chain.BestSnapshot()
if sm.topBlock() == best.Height || sm.chain.UtxoCacheFlushInProgress() {
// Update the time and violations to prevent disconnects.
sm.syncPeerState.lastBlockTime = time.Now()
sm.syncPeerState.violations = 0
return
}
state, exists := sm.peerStates[sm.syncPeer]
if !exists {
return
}
sm.clearRequestedState(state)
sm.updateSyncPeer(state)
}
// topBlock returns the best chains top block height
func (sm *SyncManager) topBlock() int32 {
if sm.syncPeer.LastBlock() > sm.syncPeer.StartingHeight() {
return sm.syncPeer.LastBlock()
}
return sm.syncPeer.StartingHeight()
}
// handleDonePeerMsg deals with peers that have signalled they are done. It
// removes the peer as a candidate for syncing and in the case where it was
// the current sync peer, attempts to select a new best peer to sync from. It
// is invoked from the syncHandler goroutine.
func (sm *SyncManager) handleDonePeerMsg(peer *peerpkg.Peer) {
state, exists := sm.peerStates[peer]
if !exists {
log.Warnf("Received done peer message for unknown peer %s", peer)
return
}
// Remove the peer from the list of candidate peers.
delete(sm.peerStates, peer)
log.Infof("Lost peer %s", peer)
// Cleanup state of requested items.
sm.clearRequestedState(state)
// Fetch a new sync peer if this is the sync peer.
if peer == sm.syncPeer {
sm.updateSyncPeer(state)
}
}
// clearRequestedState removes requested transactions
// and blocks from the global map.
func (sm *SyncManager) clearRequestedState(state *peerSyncState) {
// Remove requested transactions from the global map so that they will
// be fetched from elsewhere next time we get an inv.
for txHash := range state.requestedTxns {
delete(sm.requestedTxns, txHash)
}
// Remove requested blocks from the global map so that they will be
// fetched from elsewhere next time we get an inv.
for blockHash := range state.requestedBlocks {
delete(sm.requestedBlocks, blockHash)
}
}
// updateSyncPeer picks a new peer to sync from.
func (sm *SyncManager) updateSyncPeer(state *peerSyncState) {
log.Infof("Updating sync peer, last block: %v, violations: %v", sm.syncPeerState.lastBlockTime, sm.syncPeerState.violations)
// Disconnect from the misbehaving peer.
sm.syncPeer.Disconnect()
// Attempt to find a new peer to sync from
// Also, reset the headers-first state.
sm.syncPeer.SetSyncPeer(false)
sm.syncPeer = nil
sm.syncPeerState = nil
if sm.headersFirstMode {
best := sm.chain.BestSnapshot()
sm.resetHeaderState(&best.Hash, best.Height)
}
sm.startSync()
}
// handleTxMsg handles transaction messages from all peers.
func (sm *SyncManager) handleTxMsg(tmsg *txMsg) {
peer := tmsg.peer
state, exists := sm.peerStates[peer]
if !exists {
log.Warnf("Received tx message from unknown peer %s", peer)
return
}
// NOTE: BitcoinJ, and possibly other wallets, don't follow the spec of
// sending an inventory message and allowing the remote peer to decide
// whether or not they want to request the transaction via a getdata
// message. Unfortunately, the reference implementation permits
// unrequested data, so it has allowed wallets that don't follow the
// spec to proliferate. While this is not ideal, there is no check here
// to disconnect peers for sending unsolicited transactions to provide
// interoperability.
txHash := tmsg.tx.Hash()
// Ignore transactions that we have already rejected. Do not
// send a reject message here because if the transaction was already
// rejected, the transaction was unsolicited.
if _, exists = sm.rejectedTxns[*txHash]; exists {
log.Debugf("Ignoring unsolicited previously rejected "+
"transaction %v from %s", txHash, peer)
return
}
// Process the transaction to include validation, insertion in the
// memory pool, orphan handling, etc.
acceptedTxs, err := sm.txMemPool.ProcessTransaction(tmsg.tx,
true, true, mempool.Tag(peer.ID()))
// Remove transaction from request maps. Either the mempool/chain
// already knows about it and as such we shouldn't have any more
// instances of trying to fetch it, or we failed to insert and thus
// we'll retry next time we get an inv.
delete(state.requestedTxns, *txHash)
delete(sm.requestedTxns, *txHash)
if err != nil {
// Do not request this transaction again until a new block
// has been processed.
sm.rejectedTxns[*txHash] = struct{}{}
sm.limitMap(sm.rejectedTxns, maxRejectedTxns)
// When the error is a rule error, it means the transaction was
// simply rejected as opposed to something actually going wrong,
// so log it as such. Otherwise, something really did go wrong,
// so log it as an actual error.
if _, ok := err.(mempool.RuleError); ok {
log.Debugf("Rejected transaction %v from %s: %v",
txHash, peer, err)
} else {
log.Errorf("Failed to process transaction %v: %v",
txHash, err)
}
// Convert the error into an appropriate reject message and
// send it.
code, reason := mempool.ErrToRejectErr(err)
peer.PushRejectMsg(wire.CmdTx, code, reason, txHash, false)
return
}
if len(acceptedTxs) > 0 {
sm.peerNotifier.AnnounceNewTransactions(acceptedTxs)
}
}
// current returns true if we believe we are synced with our peers, false if we
// still have blocks to check
func (sm *SyncManager) current() bool {
if !sm.chain.IsCurrent() {
return false
}
// if blockChain thinks we are current and we have no syncPeer it
// is probably right.
if sm.syncPeer == nil {
return true
}
// No matter what chain thinks, if we are below the block we are syncing
// to we are not current.
if sm.chain.BestSnapshot().Height < sm.syncPeer.LastBlock() {
return false
}
return true
}
// handleBlockMsg handles block messages from all peers.
func (sm *SyncManager) handleBlockMsg(bmsg *blockMsg) {
peer := bmsg.peer
state, exists := sm.peerStates[peer]
if !exists {
log.Warnf("Received block message from unknown peer %s", peer)
return
}
// If we didn't ask for this block then the peer is misbehaving.
blockHash := bmsg.block.Hash()
if _, exists = state.requestedBlocks[*blockHash]; !exists {
// The regression test intentionally sends some blocks twice
// to test duplicate block insertion fails. Don't disconnect
// the peer or ignore the block when we're in regression test
// mode in this case so the chain code is actually fed the
// duplicate blocks.
if sm.chainParams != &chaincfg.RegressionNetParams {
log.Warnf("Got unrequested block %v from %s -- "+
"disconnecting", blockHash, peer.Addr())
peer.Disconnect()
return
}
}
// When in headers-first mode, if the block matches the hash of the
// first header in the list of headers that are being fetched, it's
// eligible for less validation since the headers have already been
// verified to link together and are valid up to the next checkpoint.
// Also, remove the list entry for all blocks except the checkpoint
// since it is needed to verify the next round of headers links
// properly.
isCheckpointBlock := false
behaviorFlags := blockchain.BFNone
if sm.headersFirstMode {
firstNodeEl := sm.headerList.Front()
if firstNodeEl != nil {
firstNode := firstNodeEl.Value.(*headerNode)
if blockHash.IsEqual(firstNode.hash) {
behaviorFlags |= blockchain.BFFastAdd
if firstNode.hash.IsEqual(sm.nextCheckpoint.Hash) {
isCheckpointBlock = true
} else {
sm.headerList.Remove(firstNodeEl)
}
}
}
}
// Remove block from request maps. Either chain will know about it and
// so we shouldn't have any more instances of trying to fetch it, or we
// will fail the insert and thus we'll retry next time we get an inv.
delete(state.requestedBlocks, *blockHash)
delete(sm.requestedBlocks, *blockHash)
// Process the block to include validation, best chain selection, orphan
// handling, etc.
_, isOrphan, err := sm.chain.ProcessBlock(bmsg.block, behaviorFlags)
if err != nil {
// When the error is a rule error, it means the block was simply
// rejected as opposed to something actually going wrong, so log
// it as such. Otherwise, something really did go wrong, so log
// it as an actual error.
if _, ok := err.(blockchain.RuleError); ok {
log.Infof("Rejected block %v from %s: %v", blockHash,
peer, err)
} else {
log.Errorf("Failed to process block %v: %v",
blockHash, err)
}
if dbErr, ok := err.(database.Error); ok && dbErr.ErrorCode ==
database.ErrCorruption {
panic(dbErr)
}
// Convert the error into an appropriate reject message and
// send it.
code, reason := mempool.ErrToRejectErr(err)
peer.PushRejectMsg(wire.CmdBlock, code, reason, blockHash, false)
return
}
// Meta-data about the new block this peer is reporting. We use this
// below to update this peer's lastest block height and the heights of
// other peers based on their last announced block hash. This allows us
// to dynamically update the block heights of peers, avoiding stale
// heights when looking for a new sync peer. Upon acceptance of a block
// or recognition of an orphan, we also use this information to update
// the block heights over other peers who's invs may have been ignored
// if we are actively syncing while the chain is not yet current or
// who may have lost the lock announcment race.
var heightUpdate int32
var blkHashUpdate *chainhash.Hash
// Request the parents for the orphan block from the peer that sent it.
if isOrphan {
// We've just received an orphan block from a peer. In order
// to update the height of the peer, we try to extract the
// block height from the scriptSig of the coinbase transaction.
// Extraction is only attempted if the block's version is
// high enough (ver 2+).
header := &bmsg.block.MsgBlock().Header
if blockchain.ShouldHaveSerializedBlockHeight(header) {
coinbaseTx := bmsg.block.Transactions()[0]
cbHeight, err := blockchain.ExtractCoinbaseHeight(coinbaseTx)
if err != nil {
log.Warnf("Unable to extract height from "+
"coinbase tx: %v", err)
} else {
log.Debugf("Extracted height of %v from "+
"orphan block", cbHeight)
heightUpdate = cbHeight
blkHashUpdate = blockHash
}
}
orphanRoot := sm.chain.GetOrphanRoot(blockHash)
locator, err := sm.chain.LatestBlockLocator()
if err != nil {
log.Warnf("Failed to get block locator for the "+
"latest block: %v", err)
} else {
peer.PushGetBlocksMsg(locator, orphanRoot)
}
} else {
// Only consider non-orphans for the timer.
if peer == sm.syncPeer {
sm.syncPeerState.lastBlockTime = time.Now()
}
// When the block is not an orphan, log information about it and
// update the chain state.
sm.progressLogger.LogBlockHeight(bmsg.block, sm.SyncHeight(), sm.chain)
// Update this peer's latest block height, for future
// potential sync node candidacy.
best := sm.chain.BestSnapshot()
heightUpdate = best.Height
blkHashUpdate = &best.Hash
// Clear the rejected transactions.
sm.rejectedTxns = make(map[chainhash.Hash]struct{})
}
// Update the block height for this peer. But only send a message to
// the server for updating peer heights if this is an orphan or our
// chain is "current". This avoids sending a spammy amount of messages
// if we're syncing the chain from scratch.
if blkHashUpdate != nil && heightUpdate != 0 {
peer.UpdateLastBlockHeight(heightUpdate)
if isOrphan || sm.current() {
go sm.peerNotifier.UpdatePeerHeights(blkHashUpdate, heightUpdate,
peer)
}
}
// If we are not in headers first mode, it's a good time to periodically
// flush the blockchain cache because we don't expect new blocks immediately.
// After that, there is nothing more to do.
if !sm.headersFirstMode {
if err := sm.chain.FlushCachedState(blockchain.FlushPeriodic); err != nil {
log.Errorf("Error while flushing the blockchain cache: %v", err)
}
return
}
// This is headers-first mode, so if the block is not a checkpoint
// request more blocks using the header list when the request queue is
// getting short.
if !isCheckpointBlock {
if sm.startHeader != nil &&
len(state.requestedBlocks) < minInFlightBlocks {
sm.fetchHeaderBlocks()
}
return
}
// This is headers-first mode and the block is a checkpoint. When
// there is a next checkpoint, get the next round of headers by asking
// for headers starting from the block after this one up to the next
// checkpoint.
prevHeight := sm.nextCheckpoint.Height
prevHash := sm.nextCheckpoint.Hash
sm.nextCheckpoint = sm.findNextHeaderCheckpoint(prevHeight)
if sm.nextCheckpoint != nil {
locator := blockchain.BlockLocator([]*chainhash.Hash{prevHash})
err := peer.PushGetHeadersMsg(locator, sm.nextCheckpoint.Hash)
if err != nil {
log.Warnf("Failed to send getheaders message to "+
"peer %s: %v", peer.Addr(), err)
return
}
if sm.syncPeer != nil {
log.Infof("Downloading headers for blocks %d to %d from "+
"peer %s", prevHeight+1, sm.nextCheckpoint.Height,
sm.syncPeer.Addr())
}
return
}
// This is headers-first mode, the block is a checkpoint, and there are
// no more checkpoints, so switch to normal mode by requesting blocks
// from the block after this one up to the end of the chain (zero hash).
sm.headersFirstMode = false
sm.headerList.Init()
log.Infof("Reached the final checkpoint -- switching to normal mode")
locator := blockchain.BlockLocator([]*chainhash.Hash{blockHash})
err = peer.PushGetBlocksMsg(locator, &zeroHash)
if err != nil {
log.Warnf("Failed to send getblocks message to peer %s: %v",
peer.Addr(), err)
return
}
}
// fetchHeaderBlocks creates and sends a request to the syncPeer for the next
// list of blocks to be downloaded based on the current list of headers.
func (sm *SyncManager) fetchHeaderBlocks() {
// Nothing to do if there is no sync peer.
if sm.syncPeer == nil {
log.Warnf("fetchHeaderBlocks called with no sync peer")
return
}
// Nothing to do if there is no start header.
if sm.startHeader == nil {
log.Warnf("fetchHeaderBlocks called with no start header")
return
}
// Build up a getdata request for the list of blocks the headers
// describe. The size hint will be limited to wire.MaxInvPerMsg by
// the function, so no need to double check it here.
gdmsg := wire.NewMsgGetDataSizeHint(uint(sm.headerList.Len()))
numRequested := 0
for e := sm.startHeader; e != nil; e = e.Next() {
node, ok := e.Value.(*headerNode)
if !ok {
log.Warn("Header list node type is not a headerNode")
continue
}
iv := wire.NewInvVect(wire.InvTypeBlock, node.hash)
haveInv, err := sm.haveInventory(iv)
if err != nil {
log.Warnf("Unexpected failure when checking for "+
"existing inventory during header block "+
"fetch: %v", err)
}
if !haveInv {
syncPeerState := sm.peerStates[sm.syncPeer]
sm.requestedBlocks[*node.hash] = struct{}{}
syncPeerState.requestedBlocks[*node.hash] = struct{}{}
gdmsg.AddInvVect(iv)
numRequested++
}
sm.startHeader = e.Next()
if numRequested >= wire.MaxInvPerMsg {
break
}
}
if len(gdmsg.InvList) > 0 {
sm.syncPeer.QueueMessage(gdmsg, nil)
}
}
// handleHeadersMsg handles block header messages from all peers. Headers are
// requested when performing a headers-first sync.
func (sm *SyncManager) handleHeadersMsg(hmsg *headersMsg) {
peer := hmsg.peer
_, exists := sm.peerStates[peer]
if !exists {
log.Warnf("Received headers message from unknown peer %s", peer)
return
}
// The remote peer is misbehaving if we didn't request headers.
msg := hmsg.headers
numHeaders := len(msg.Headers)
if !sm.headersFirstMode {
log.Warnf("Got %d unrequested headers from %s -- "+
"disconnecting", numHeaders, peer.Addr())
peer.Disconnect()
return
}
// Nothing to do for an empty headers message.
if numHeaders == 0 {
return
}
// Process all of the received headers ensuring each one connects to the
// previous and that checkpoints match.
receivedCheckpoint := false
var finalHash *chainhash.Hash
for _, blockHeader := range msg.Headers {
blockHash := blockHeader.BlockHash()
finalHash = &blockHash
// Ensure there is a previous header to compare against.
prevNodeEl := sm.headerList.Back()
if prevNodeEl == nil {
log.Warnf("Header list does not contain a previous" +
"element as expected -- disconnecting peer")
peer.Disconnect()
return
}
// Ensure the header properly connects to the previous one and
// add it to the list of headers.
node := headerNode{hash: &blockHash}
prevNode := prevNodeEl.Value.(*headerNode)
if prevNode.hash.IsEqual(&blockHeader.PrevBlock) {
node.height = prevNode.height + 1
e := sm.headerList.PushBack(&node)
if sm.startHeader == nil {
sm.startHeader = e
}
} else {
log.Warnf("Received block header that does not "+
"properly connect to the chain from peer %s "+
"-- disconnecting", peer.Addr())
peer.Disconnect()
return
}
// Verify the header at the next checkpoint height matches.
if node.height == sm.nextCheckpoint.Height {
if node.hash.IsEqual(sm.nextCheckpoint.Hash) {
receivedCheckpoint = true
log.Infof("Verified downloaded block "+
"header against checkpoint at height "+
"%d/hash %s", node.height, node.hash)
} else {
log.Warnf("Block header at height %d/hash "+
"%s from peer %s does NOT match "+
"expected checkpoint hash of %s -- "+
"disconnecting", node.height,
node.hash, peer.Addr(),
sm.nextCheckpoint.Hash)
peer.Disconnect()