lnd.xprv/htlcswitch/circuit.go

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package htlcswitch
import (
"bytes"
"crypto/sha256"
"encoding/hex"
"sync"
"github.com/go-errors/errors"
"github.com/lightningnetwork/lnd/lnwire"
)
// circuitKey uniquely identifies an active circuit between two open channels.
// Currently, the payment hash is used to uniquely identify each circuit.
type circuitKey [sha256.Size]byte
// String returns the string representation of the circuitKey.
func (k *circuitKey) String() string {
return hex.EncodeToString(k[:])
}
// paymentCircuit is used by the htlc switch subsystem to determine the
// forwards/backwards path for the settle/fail HTLC messages. A payment circuit
// will be created once a channel link forwards the htlc add request and
// removed when we receive settle/fail htlc message.
type paymentCircuit struct {
// PaymentHash used as unique identifier of payment.
PaymentHash circuitKey
// Src identifies the channel from which add htlc request is came from
// and to which settle/fail htlc request will be returned back. Once
// the switch forwards the settle/fail message to the src the circuit
// is considered to be completed.
Src lnwire.ShortChannelID
// Dest identifies the channel to which we propagate the htlc add
// update and from which we are expecting to receive htlc settle/fail
// request back.
Dest lnwire.ShortChannelID
// ErrorEncrypter is used to re-encrypt the onion failure before
// sending it back to the originator of the payment.
ErrorEncrypter ErrorEncrypter
// RefCount is used to count the circuits with the same circuit key.
RefCount int
}
// newPaymentCircuit creates new payment circuit instance.
func newPaymentCircuit(src, dest lnwire.ShortChannelID, key circuitKey,
e ErrorEncrypter) *paymentCircuit {
return &paymentCircuit{
Src: src,
Dest: dest,
PaymentHash: key,
RefCount: 1,
ErrorEncrypter: e,
}
}
// isEqual checks the equality of two payment circuits.
func (a *paymentCircuit) isEqual(b *paymentCircuit) bool {
return bytes.Equal(a.PaymentHash[:], b.PaymentHash[:]) &&
a.Src == b.Src &&
a.Dest == b.Dest
}
// circuitMap is a data structure that implements thread safe storage of
// circuits. Each circuit key (payment hash) may have several of circuits
// corresponding to it due to the possibility of repeated payment hashes.
//
// TODO(andrew.shvv) make it persistent
type circuitMap struct {
sync.RWMutex
circuits map[circuitKey]*paymentCircuit
}
// newCircuitMap creates a new instance of the circuitMap.
func newCircuitMap() *circuitMap {
return &circuitMap{
circuits: make(map[circuitKey]*paymentCircuit),
}
}
// add adds a new active payment circuit to the circuitMap.
func (m *circuitMap) add(circuit *paymentCircuit) error {
m.Lock()
defer m.Unlock()
// Examine the circuit map to see if this circuit is already in use or
// not. If so, then we'll simply increment the reference count.
// Otherwise, we'll create a new circuit from scratch.
//
// TODO(roasbeef): include dest+src+amt in key
if c, ok := m.circuits[circuit.PaymentHash]; ok {
c.RefCount++
return nil
}
m.circuits[circuit.PaymentHash] = circuit
return nil
}
// remove destroys the target circuit by removing it from the circuit map.
func (m *circuitMap) remove(key circuitKey) (*paymentCircuit, error) {
m.Lock()
defer m.Unlock()
if circuit, ok := m.circuits[key]; ok {
if circuit.RefCount--; circuit.RefCount == 0 {
delete(m.circuits, key)
}
return circuit, nil
}
return nil, errors.Errorf("can't find circuit"+
" for key %v", key)
}
// pending returns number of circuits which are waiting for to be completed
// (settle/fail responses to be received).
func (m *circuitMap) pending() int {
m.RLock()
defer m.RUnlock()
var length int
for _, circuits := range m.circuits {
length += circuits.RefCount
}
return length
}