lnd.xprv/lnwallet/sigpool.go

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package lnwallet
import (
"fmt"
"sync"
"sync/atomic"
"github.com/btcsuite/btcd/btcec"
"github.com/btcsuite/btcd/wire"
2018-07-31 10:17:17 +03:00
"github.com/lightningnetwork/lnd/lnwire"
)
const (
// jobBuffer is a constant the represents the buffer of jobs in the two
// main queues. This allows clients avoid necessarily blocking when
// submitting jobs into the queue.
jobBuffer = 100
// TODO(roasbeef): job buffer pool?
)
// VerifyJob is a job sent to the sigPool sig pool to verify a signature
// on a transaction. The items contained in the struct are necessary and
// sufficient to verify the full signature. The passed sigHash closure function
// should be set to a function that generates the relevant sighash.
//
// TODO(roasbeef): when we move to ecschnorr, make into batch signature
// verification using bos-coster (or pip?).
type VerifyJob struct {
// PubKey is the public key that was used to generate the purported
// valid signature. Note that with the current channel construction,
// this public key will likely have been tweaked using the current per
// commitment point for a particular commitment transactions.
PubKey *btcec.PublicKey
// Sig is the raw signature generated using the above public key. This
// is the signature to be verified.
Sig *btcec.Signature
// SigHash is a function closure generates the sighashes that the
// passed signature is known to have signed.
SigHash func() ([]byte, error)
// HtlcIndex is the index of the HTLC from the PoV of the remote
// party's update log.
HtlcIndex uint64
// Cancel is a channel that should be closed if the caller wishes to
// cancel all pending verification jobs part of a single batch. This
// channel is to be closed in the case that a single signature in a
// batch has been returned as invalid, as there is no need to verify
// the remainder of the signatures.
Cancel chan struct{}
// ErrResp is the channel that the result of the signature verification
// is to be sent over. In the see that the signature is valid, a nil
// error will be passed. Otherwise, a concrete error detailing the
// issue will be passed.
ErrResp chan *HtlcIndexErr
}
// HtlcIndexErr is a special type of error that also includes a pointer to the
// original validation job. This error message allows us to craft more detailed
// errors at upper layers.
type HtlcIndexErr struct {
error
*VerifyJob
}
// SignJob is a job sent to the sigPool sig pool to generate a valid
// signature according to the passed SignDescriptor for the passed transaction.
// Jobs are intended to be sent in batches in order to parallelize the job of
// generating signatures for a new commitment transaction.
type SignJob struct {
// SignDesc is intended to be a full populated SignDescriptor which
// encodes the necessary material (keys, witness script, etc) required
// to generate a valid signature for the specified input.
SignDesc SignDescriptor
// Tx is the transaction to be signed. This is required to generate the
// proper sighash for the input to be signed.
Tx *wire.MsgTx
// OutputIndex is the output index of the HTLC on the commitment
// transaction being signed.
OutputIndex int32
// Cancel is a channel that should be closed if the caller wishes to
// abandon all pending sign jobs part of a single batch.
Cancel chan struct{}
// Resp is the channel that the response to this particular SignJob
// will be sent over.
//
// TODO(roasbeef): actually need to allow caller to set, need to retain
// order mark commit sig as special
Resp chan SignJobResp
}
// SignJobResp is the response to a sign job. Both channels are to be read in
// order to ensure no unnecessary goroutine blocking occurs. Additionally, both
// channels should be buffered.
type SignJobResp struct {
// Sig is the generated signature for a particular SignJob In the case
// of an error during signature generation, then this value sent will
// be nil.
Sig lnwire.Sig
// Err is the error that occurred when executing the specified
// signature job. In the case that no error occurred, this value will
// be nil.
Err error
}
// TODO(roasbeef); fix description
// SigPool is a struct that is meant to allow the current channel state
// machine to parallelize all signature generation and verification. This
// struct is needed as _each_ HTLC when creating a commitment transaction
// requires a signature, and similarly a receiver of a new commitment must
// verify all the HTLC signatures included within the CommitSig message. A pool
// of workers will be maintained by the sigPool. Batches of jobs (either
// to sign or verify) can be sent to the pool of workers which will
// asynchronously perform the specified job.
type SigPool struct {
started uint32 // To be used atomically.
stopped uint32 // To be used atomically.
signer Signer
verifyJobs chan VerifyJob
signJobs chan SignJob
wg sync.WaitGroup
quit chan struct{}
numWorkers int
}
// NewSigPool creates a new signature pool with the specified number of
// workers. The recommended parameter for the number of works is the number of
// physical CPU cores available on the target machine.
func NewSigPool(numWorkers int, signer Signer) *SigPool {
return &SigPool{
signer: signer,
numWorkers: numWorkers,
verifyJobs: make(chan VerifyJob, jobBuffer),
signJobs: make(chan SignJob, jobBuffer),
quit: make(chan struct{}),
}
}
// Start starts of all goroutines that the sigPool sig pool needs to
// carry out its duties.
func (s *SigPool) Start() error {
if !atomic.CompareAndSwapUint32(&s.started, 0, 1) {
return nil
}
for i := 0; i < s.numWorkers; i++ {
s.wg.Add(1)
go s.poolWorker()
}
return nil
}
// Stop signals any active workers carrying out jobs to exit so the sigPool can
// gracefully shutdown.
func (s *SigPool) Stop() error {
if !atomic.CompareAndSwapUint32(&s.stopped, 0, 1) {
return nil
}
close(s.quit)
s.wg.Wait()
return nil
}
// poolWorker is the main worker goroutine within the sigPool sig pool.
// Individual batches are distributed amongst each of the active workers. The
// workers then execute the task based on the type of job, and return the
// result back to caller.
func (s *SigPool) poolWorker() {
defer s.wg.Done()
for {
select {
// We've just received a new signature job. Given the items
// contained within the message, we'll craft a signature and
// send the result along with a possible error back to the
// caller.
case sigMsg := <-s.signJobs:
rawSig, err := s.signer.SignOutputRaw(
sigMsg.Tx, &sigMsg.SignDesc,
)
if err != nil {
select {
case sigMsg.Resp <- SignJobResp{
Sig: lnwire.Sig{},
Err: err,
}:
continue
case <-sigMsg.Cancel:
continue
case <-s.quit:
return
}
}
sig, err := lnwire.NewSigFromRawSignature(rawSig)
select {
case sigMsg.Resp <- SignJobResp{
Sig: sig,
Err: err,
}:
case <-sigMsg.Cancel:
continue
case <-s.quit:
return
}
// We've just received a new verification job from the outside
// world. We'll attempt to construct the sighash, parse the
// signature, and finally verify the signature.
case verifyMsg := <-s.verifyJobs:
sigHash, err := verifyMsg.SigHash()
if err != nil {
select {
case verifyMsg.ErrResp <- &HtlcIndexErr{
error: err,
VerifyJob: &verifyMsg,
}:
continue
case <-verifyMsg.Cancel:
continue
}
}
rawSig := verifyMsg.Sig
if !rawSig.Verify(sigHash, verifyMsg.PubKey) {
err := fmt.Errorf("invalid signature "+
"sighash: %x, sig: %x", sigHash,
rawSig.Serialize())
select {
case verifyMsg.ErrResp <- &HtlcIndexErr{
error: err,
VerifyJob: &verifyMsg,
}:
case <-verifyMsg.Cancel:
case <-s.quit:
return
}
} else {
select {
case verifyMsg.ErrResp <- nil:
case <-verifyMsg.Cancel:
case <-s.quit:
return
}
}
// The sigPool sig pool is exiting, so we will as well.
case <-s.quit:
return
}
}
}
// SubmitSignBatch submits a batch of signature jobs to the sigPool. The
// response and cancel channels for each of the SignJob's are expected to be
// fully populated, as the response for each job will be sent over the
// response channel within the job itself.
func (s *SigPool) SubmitSignBatch(signJobs []SignJob) {
for _, job := range signJobs {
select {
case s.signJobs <- job:
case <-job.Cancel:
// TODO(roasbeef): return error?
case <-s.quit:
return
}
}
}
// SubmitVerifyBatch submits a batch of verification jobs to the sigPool. For
// each job submitted, an error will be passed into the returned channel
// denoting if signature verification was valid or not. The passed cancelChan
// allows the caller to cancel all pending jobs in the case that they wish to
// bail early.
func (s *SigPool) SubmitVerifyBatch(verifyJobs []VerifyJob,
cancelChan chan struct{}) <-chan *HtlcIndexErr {
errChan := make(chan *HtlcIndexErr, len(verifyJobs))
for _, job := range verifyJobs {
job.Cancel = cancelChan
job.ErrResp = errChan
select {
case s.verifyJobs <- job:
case <-job.Cancel:
return errChan
}
}
return errChan
}