// AskForOneBlock is for testing only, so you can ask for a specific block height
// and see what goes wrong
func (s *SPVCon) AskForOneBlock(h int32) error {
var hdr wire.BlockHeader
var err error
dbTip := int32(h)
s.headerMutex.Lock() // seek to header we need
_, err = s.headerFile.Seek(int64((dbTip)*80), os.SEEK_SET)
if err != nil {
return err
}
err = hdr.Deserialize(s.headerFile) // read header, done w/ file for now
s.headerMutex.Unlock() // unlock after reading 1 header
if err != nil {
log.Printf("header deserialize error!\n")
return err
}
bHash := hdr.BlockSha()
// create inventory we're asking for
iv1 := wire.NewInvVect(wire.InvTypeWitnessBlock, &bHash)
gdataMsg := wire.NewMsgGetData()
// add inventory
err = gdataMsg.AddInvVect(iv1)
if err != nil {
return err
}
hah := NewRootAndHeight(bHash, h)
s.outMsgQueue <- gdataMsg
s.blockQueue <- hah // push height and mroot of requested block on queue
return nil
}
// checkProofOfWork ensures the block header bits which indicate the target
// difficulty is in min/max range and that the block hash is less than the
// target difficulty as claimed.
//
// The flags modify the behavior of this function as follows:
// - BFNoPoWCheck: The check to ensure the block hash is less than the target
// difficulty is not performed.
func checkProofOfWork(header *wire.BlockHeader, powLimit *big.Int, flags BehaviorFlags) error {
// The target difficulty must be larger than zero.
target := CompactToBig(header.Bits)
if target.Sign() <= 0 {
str := fmt.Sprintf("block target difficulty of %064x is too low",
target)
return ruleError(ErrUnexpectedDifficulty, str)
}
// The target difficulty must be less than the maximum allowed.
if target.Cmp(powLimit) > 0 {
str := fmt.Sprintf("block target difficulty of %064x is "+
"higher than max of %064x", target, powLimit)
return ruleError(ErrUnexpectedDifficulty, str)
}
// The block hash must be less than the claimed target unless the flag
// to avoid proof of work checks is set.
if flags&BFNoPoWCheck != BFNoPoWCheck {
// The block hash must be less than the claimed target.
hash := header.BlockHash()
hashNum := HashToBig(&hash)
if hashNum.Cmp(target) > 0 {
str := fmt.Sprintf("block hash of %064x is higher than "+
"expected max of %064x", hashNum, target)
return ruleError(ErrHighHash, str)
}
}
return nil
}
/* calcDiff returns a bool given two block headers. This bool is
true if the correct dificulty adjustment is seen in the "next" header.
Only feed it headers n-2016 and n-1, otherwise it will calculate a difficulty
when no adjustment should take place, and return false.
Note that the epoch is actually 2015 blocks long, which is confusing. */
func calcDiffAdjust(start, end wire.BlockHeader, p *chaincfg.Params) uint32 {
duration := end.Timestamp.UnixNano() - start.Timestamp.UnixNano()
if duration < minRetargetTimespan {
log.Printf("whoa there, block %s off-scale high 4X diff adjustment!",
end.BlockSha().String())
duration = minRetargetTimespan
} else if duration > maxRetargetTimespan {
log.Printf("Uh-oh! block %s off-scale low 0.25X diff adjustment!\n",
end.BlockSha().String())
duration = maxRetargetTimespan
}
// calculation of new 32-byte difficulty target
// first turn the previous target into a big int
prevTarget := blockchain.CompactToBig(start.Bits)
// new target is old * duration...
newTarget := new(big.Int).Mul(prevTarget, big.NewInt(duration))
// divided by 2 weeks
newTarget.Div(newTarget, big.NewInt(int64(targetTimespan)))
// clip again if above minimum target (too easy)
if newTarget.Cmp(p.PowLimit) > 0 {
newTarget.Set(p.PowLimit)
}
// calculate and return 4-byte 'bits' difficulty from 32-byte target
return blockchain.BigToCompact(newTarget)
}
func (s *SPVCon) AskForHeaders() error {
var hdr wire.BlockHeader
ghdr := wire.NewMsgGetHeaders()
ghdr.ProtocolVersion = s.localVersion
s.headerMutex.Lock() // start header file ops
info, err := s.headerFile.Stat()
if err != nil {
return err
}
headerFileSize := info.Size()
if headerFileSize == 0 || headerFileSize%80 != 0 { // header file broken
return fmt.Errorf("Header file not a multiple of 80 bytes")
}
// seek to 80 bytes from end of file
ns, err := s.headerFile.Seek(-80, os.SEEK_END)
if err != nil {
log.Printf("can't seek\n")
return err
}
log.Printf("suk to offset %d (should be near the end\n", ns)
// get header from last 80 bytes of file
err = hdr.Deserialize(s.headerFile)
if err != nil {
log.Printf("can't Deserialize")
return err
}
s.headerMutex.Unlock() // done with header file
cHash := hdr.BlockSha()
err = ghdr.AddBlockLocatorHash(&cHash)
if err != nil {
return err
}
fmt.Printf("get headers message has %d header hashes, first one is %s\n",
len(ghdr.BlockLocatorHashes), ghdr.BlockLocatorHashes[0].String())
s.outMsgQueue <- ghdr
return nil
}
// solveBlock attempts to find a nonce which makes the passed block header hash
// to a value less than the target difficulty. When a successful solution is
// found true is returned and the nonce field of the passed header is updated
// with the solution. False is returned if no solution exists.
func solveBlock(header *wire.BlockHeader, targetDifficulty *big.Int) bool {
// sbResult is used by the solver goroutines to send results.
type sbResult struct {
found bool
nonce uint32
}
// solver accepts a block header and a nonce range to test. It is
// intended to be run as a goroutine.
quit := make(chan bool)
results := make(chan sbResult)
solver := func(hdr wire.BlockHeader, startNonce, stopNonce uint32) {
// We need to modify the nonce field of the header, so make sure
// we work with a copy of the original header.
for i := startNonce; i >= startNonce && i <= stopNonce; i++ {
select {
case <-quit:
return
default:
hdr.Nonce = i
hash := hdr.BlockHash()
if blockchain.HashToBig(&hash).Cmp(targetDifficulty) <= 0 {
results <- sbResult{true, i}
return
}
}
}
results <- sbResult{false, 0}
}
startNonce := uint32(0)
stopNonce := uint32(math.MaxUint32)
numCores := uint32(runtime.NumCPU())
noncesPerCore := (stopNonce - startNonce) / numCores
for i := uint32(0); i < numCores; i++ {
rangeStart := startNonce + (noncesPerCore * i)
rangeStop := startNonce + (noncesPerCore * (i + 1)) - 1
if i == numCores-1 {
rangeStop = stopNonce
}
go solver(*header, rangeStart, rangeStop)
}
for i := uint32(0); i < numCores; i++ {
result := <-results
if result.found {
close(quit)
header.Nonce = result.nonce
return true
}
}
return false
}
/* checkProofOfWork verifies the header hashes into something
lower than specified by the 4-byte bits field. */
func checkProofOfWork(header wire.BlockHeader, p *chaincfg.Params) bool {
target := blockchain.CompactToBig(header.Bits)
// The target must more than 0. Why can you even encode negative...
if target.Sign() <= 0 {
log.Printf("block target %064x is neagtive(??)\n", target.Bytes())
return false
}
// The target must be less than the maximum allowed (difficulty 1)
if target.Cmp(p.PowLimit) > 0 {
log.Printf("block target %064x is "+
"higher than max of %064x", target, p.PowLimit.Bytes())
return false
}
// The header hash must be less than the claimed target in the header.
blockHash := header.BlockSha()
hashNum := blockchain.ShaHashToBig(&blockHash)
if hashNum.Cmp(target) > 0 {
log.Printf("block hash %064x is higher than "+
"required target of %064x", hashNum, target)
return false
}
return true
}
// AskForMerkBlocks requests blocks from current to last
// right now this asks for 1 block per getData message.
// Maybe it's faster to ask for many in a each message?
func (s *SPVCon) AskForBlocks() error {
var hdr wire.BlockHeader
s.headerMutex.Lock() // lock just to check filesize
stat, err := os.Stat(headerFileName)
s.headerMutex.Unlock() // checked, unlock
endPos := stat.Size()
headerTip := int32(endPos/80) - 1 // move back 1 header length to read
dbTip, err := s.TS.GetDBSyncHeight()
if err != nil {
return err
}
fmt.Printf("dbTip %d headerTip %d\n", dbTip, headerTip)
if dbTip > headerTip {
return fmt.Errorf("error- db longer than headers! shouldn't happen.")
}
if dbTip == headerTip {
// nothing to ask for; set wait state and return
fmt.Printf("no blocks to request, entering wait state\n")
fmt.Printf("%d bytes received\n", s.RBytes)
s.inWaitState <- true
// also advertise any unconfirmed txs here
s.Rebroadcast()
return nil
}
fmt.Printf("will request blocks %d to %d\n", dbTip+1, headerTip)
if !s.HardMode { // don't send this in hardmode! that's the whole point
// create initial filter
filt, err := s.TS.GimmeFilter()
if err != nil {
return err
}
// send filter
s.SendFilter(filt)
fmt.Printf("sent filter %x\n", filt.MsgFilterLoad().Filter)
}
// loop through all heights where we want merkleblocks.
for dbTip < headerTip {
dbTip++ // we're requesting the next header
// load header from file
s.headerMutex.Lock() // seek to header we need
_, err = s.headerFile.Seek(int64((dbTip)*80), os.SEEK_SET)
if err != nil {
return err
}
err = hdr.Deserialize(s.headerFile) // read header, done w/ file for now
s.headerMutex.Unlock() // unlock after reading 1 header
if err != nil {
log.Printf("header deserialize error!\n")
return err
}
bHash := hdr.BlockSha()
// create inventory we're asking for
iv1 := new(wire.InvVect)
// if hardmode, ask for legit blocks, none of this ralphy stuff
if s.HardMode {
iv1 = wire.NewInvVect(wire.InvTypeWitnessBlock, &bHash)
} else { // ah well
iv1 = wire.NewInvVect(wire.InvTypeFilteredWitnessBlock, &bHash)
}
gdataMsg := wire.NewMsgGetData()
// add inventory
err = gdataMsg.AddInvVect(iv1)
if err != nil {
return err
}
hah := NewRootAndHeight(hdr.BlockSha(), dbTip)
if dbTip == headerTip { // if this is the last block, indicate finality
hah.final = true
}
// waits here most of the time for the queue to empty out
s.blockQueue <- hah // push height and mroot of requested block on queue
s.outMsgQueue <- gdataMsg
}
return nil
}
// IngestHeaders takes in a bunch of headers and appends them to the
// local header file, checking that they fit. If there's no headers,
// it assumes we're done and returns false. If it worked it assumes there's
// more to request and returns true.
func (s *SPVCon) IngestHeaders(m *wire.MsgHeaders) (bool, error) {
gotNum := int64(len(m.Headers))
if gotNum > 0 {
fmt.Printf("got %d headers. Range:\n%s - %s\n",
gotNum, m.Headers[0].BlockSha().String(),
m.Headers[len(m.Headers)-1].BlockSha().String())
} else {
log.Printf("got 0 headers, we're probably synced up")
return false, nil
}
s.headerMutex.Lock()
defer s.headerMutex.Unlock()
var err error
// seek to last header
_, err = s.headerFile.Seek(-80, os.SEEK_END)
if err != nil {
return false, err
}
var last wire.BlockHeader
err = last.Deserialize(s.headerFile)
if err != nil {
return false, err
}
prevHash := last.BlockSha()
endPos, err := s.headerFile.Seek(0, os.SEEK_END)
if err != nil {
return false, err
}
tip := int32(endPos/80) - 1 // move back 1 header length to read
// check first header returned to make sure it fits on the end
// of our header file
if !m.Headers[0].PrevBlock.IsEqual(&prevHash) {
// delete 100 headers if this happens! Dumb reorg.
log.Printf("reorg? header msg doesn't fit. points to %s, expect %s",
m.Headers[0].PrevBlock.String(), prevHash.String())
if endPos < 8080 {
// jeez I give up, back to genesis
s.headerFile.Truncate(80)
} else {
err = s.headerFile.Truncate(endPos - 8000)
if err != nil {
return false, fmt.Errorf("couldn't truncate header file")
}
}
return true, fmt.Errorf("Truncated header file to try again")
}
for _, resphdr := range m.Headers {
// write to end of file
err = resphdr.Serialize(s.headerFile)
if err != nil {
return false, err
}
// advance chain tip
tip++
// check last header
worked := CheckHeader(s.headerFile, tip, s.TS.Param)
if !worked {
if endPos < 8080 {
// jeez I give up, back to genesis
s.headerFile.Truncate(80)
} else {
err = s.headerFile.Truncate(endPos - 8000)
if err != nil {
return false, fmt.Errorf("couldn't truncate header file")
}
}
// probably should disconnect from spv node at this point,
// since they're giving us invalid headers.
return true, fmt.Errorf(
"Header %d - %s doesn't fit, dropping 100 headers.",
resphdr.BlockSha().String(), tip)
}
}
log.Printf("Headers to height %d OK.", tip)
return true, nil
}
// checkBlockHeaderContext peforms several validation checks on the block header
// which depend on its position within the block chain.
//
// The flags modify the behavior of this function as follows:
// - BFFastAdd: All checks except those involving comparing the header against
// the checkpoints are not performed.
//
// This function MUST be called with the chain state lock held (for writes).
func (b *BlockChain) checkBlockHeaderContext(header *wire.BlockHeader, prevNode *blockNode, flags BehaviorFlags) error {
// The genesis block is valid by definition.
if prevNode == nil {
return nil
}
fastAdd := flags&BFFastAdd == BFFastAdd
if !fastAdd {
// Ensure the difficulty specified in the block header matches
// the calculated difficulty based on the previous block and
// difficulty retarget rules.
expectedDifficulty, err := b.calcNextRequiredDifficulty(prevNode,
header.Timestamp)
if err != nil {
return err
}
blockDifficulty := header.Bits
if blockDifficulty != expectedDifficulty {
str := "block difficulty of %d is not the expected value of %d"
str = fmt.Sprintf(str, blockDifficulty, expectedDifficulty)
return ruleError(ErrUnexpectedDifficulty, str)
}
// Ensure the timestamp for the block header is after the
// median time of the last several blocks (medianTimeBlocks).
medianTime, err := b.calcPastMedianTime(prevNode)
if err != nil {
log.Errorf("calcPastMedianTime: %v", err)
return err
}
if !header.Timestamp.After(medianTime) {
str := "block timestamp of %v is not after expected %v"
str = fmt.Sprintf(str, header.Timestamp, medianTime)
return ruleError(ErrTimeTooOld, str)
}
}
// The height of this block is one more than the referenced previous
// block.
blockHeight := prevNode.height + 1
// Ensure chain matches up to predetermined checkpoints.
blockHash := header.BlockHash()
if !b.verifyCheckpoint(blockHeight, &blockHash) {
str := fmt.Sprintf("block at height %d does not match "+
"checkpoint hash", blockHeight)
return ruleError(ErrBadCheckpoint, str)
}
// Find the previous checkpoint and prevent blocks which fork the main
// chain before it. This prevents storage of new, otherwise valid,
// blocks which build off of old blocks that are likely at a much easier
// difficulty and therefore could be used to waste cache and disk space.
checkpointBlock, err := b.findPreviousCheckpoint()
if err != nil {
return err
}
if checkpointBlock != nil && blockHeight < checkpointBlock.Height() {
str := fmt.Sprintf("block at height %d forks the main chain "+
"before the previous checkpoint at height %d",
blockHeight, checkpointBlock.Height())
return ruleError(ErrForkTooOld, str)
}
// Reject outdated block versions once a majority of the network
// has upgraded. These were originally voted on by BIP0034,
// BIP0065, and BIP0066.
params := b.chainParams
if header.Version < 2 && blockHeight >= params.BIP0034Height ||
header.Version < 3 && blockHeight >= params.BIP0066Height ||
header.Version < 4 && blockHeight >= params.BIP0065Height {
str := "new blocks with version %d are no longer valid"
str = fmt.Sprintf(str, header.Version)
return ruleError(ErrBlockVersionTooOld, str)
}
return nil
}
func CheckHeader(r io.ReadSeeker, height int32, p *chaincfg.Params) bool {
var err error
var cur, prev, epochStart wire.BlockHeader
// don't try to verfy the genesis block. That way madness lies.
if height == 0 {
return true
}
// initial load of headers
// load epochstart, previous and current.
// get the header from the epoch start, up to 2016 blocks ago
_, err = r.Seek(int64(80*(height-(height%epochLength))), os.SEEK_SET)
if err != nil {
log.Printf(err.Error())
return false
}
err = epochStart.Deserialize(r)
if err != nil {
log.Printf(err.Error())
return false
}
// log.Printf("start epoch at height %d ", height-(height%epochLength))
// seek to n-1 header
_, err = r.Seek(int64(80*(height-1)), os.SEEK_SET)
if err != nil {
log.Printf(err.Error())
return false
}
// read in n-1
err = prev.Deserialize(r)
if err != nil {
log.Printf(err.Error())
return false
}
// seek to curHeight header and read in
_, err = r.Seek(int64(80*(height)), os.SEEK_SET)
if err != nil {
log.Printf(err.Error())
return false
}
err = cur.Deserialize(r)
if err != nil {
log.Printf(err.Error())
return false
}
// get hash of n-1 header
prevHash := prev.BlockSha()
// check if headers link together. That whole 'blockchain' thing.
if prevHash.IsEqual(&cur.PrevBlock) == false {
log.Printf("Headers %d and %d don't link.\n",
height-1, height)
log.Printf("%s - %s",
prev.BlockSha().String(), cur.BlockSha().String())
return false
}
rightBits := epochStart.Bits // normal, no adjustment; Dn = Dn-1
// see if we're on a difficulty adjustment block
if (height)%epochLength == 0 {
// if so, check if difficulty adjustment is valid.
// That whole "controlled supply" thing.
// calculate diff n based on n-2016 ... n-1
rightBits = calcDiffAdjust(epochStart, prev, p)
// done with adjustment, save new ephochStart header
epochStart = cur
log.Printf("Update epoch at height %d", height)
} else { // not a new epoch
// if on testnet, check for difficulty nerfing
if p.ResetMinDifficulty && cur.Timestamp.After(
prev.Timestamp.Add(targetSpacing*2)) {
// fmt.Printf("nerf %d ", curHeight)
rightBits = p.PowLimitBits // difficulty 1
}
if cur.Bits != rightBits {
log.Printf("Block %d %s incorrect difficuly. Read %x, expect %x\n",
height, cur.BlockSha().String(), cur.Bits, rightBits)
return false
}
}
// check if there's a valid proof of work. That whole "Bitcoin" thing.
if !checkProofOfWork(cur, p) {
log.Printf("Block %d Bad proof of work.\n", height)
return false
}
return true // it must have worked if there's no errors and got to the end.
}
