package channeldb import ( "bytes" "encoding/binary" "errors" "fmt" "github.com/coreos/bbolt" "github.com/lightningnetwork/lnd/lntypes" ) var ( // ErrAlreadyPaid signals we have already paid this payment hash. ErrAlreadyPaid = errors.New("invoice is already paid") // ErrPaymentInFlight signals that payment for this payment hash is // already "in flight" on the network. ErrPaymentInFlight = errors.New("payment is in transition") // ErrPaymentNotInitiated is returned if payment wasn't initiated in // switch. ErrPaymentNotInitiated = errors.New("payment isn't initiated") // ErrPaymentAlreadyCompleted is returned in the event we attempt to // recomplete a completed payment. ErrPaymentAlreadyCompleted = errors.New("payment is already completed") // ErrPaymentAlreadyFailed is returned in the event we attempt to // re-fail a failed payment. ErrPaymentAlreadyFailed = errors.New("payment has already failed") // ErrUnknownPaymentStatus is returned when we do not recognize the // existing state of a payment. ErrUnknownPaymentStatus = errors.New("unknown payment status") ) // ControlTower tracks all outgoing payments made, whose primary purpose is to // prevent duplicate payments to the same payment hash. In production, a // persistent implementation is preferred so that tracking can survive across // restarts. Payments are transitioned through various payment states, and the // ControlTower interface provides access to driving the state transitions. type ControlTower interface { // InitPayment atomically moves the payment into the InFlight state. // This method checks that no completed payment exist for this payment // hash. InitPayment(lntypes.Hash, *PaymentCreationInfo) error // RegisterAttempt atomically records the provided PaymentAttemptInfo. RegisterAttempt(lntypes.Hash, *PaymentAttemptInfo) error // Success transitions a payment into the Completed state. After // invoking this method, InitPayment should always return an error to // prevent us from making duplicate payments to the same payment hash. // The provided preimage is atomically saved to the DB for record // keeping. Success(lntypes.Hash, lntypes.Preimage) error // Fail transitions a payment into the Failed state. After invoking // this method, InitPayment should return nil on its next call for this // payment hash, allowing the switch to make a subsequent payment. Fail(lntypes.Hash) error // FetchInFlightPayments returns all payments with status InFlight. FetchInFlightPayments() ([]*InFlightPayment, error) } // paymentControl is persistent implementation of ControlTower to restrict // double payment sending. type paymentControl struct { db *DB } // NewPaymentControl creates a new instance of the paymentControl. func NewPaymentControl(db *DB) ControlTower { return &paymentControl{ db: db, } } // InitPayment checks or records the given PaymentCreationInfo with the DB, // making sure it does not already exist as an in-flight payment. Then this // method returns successfully, the payment is guranteeed to be in the InFlight // state. func (p *paymentControl) InitPayment(paymentHash lntypes.Hash, info *PaymentCreationInfo) error { var b bytes.Buffer if err := serializePaymentCreationInfo(&b, info); err != nil { return err } infoBytes := b.Bytes() var takeoffErr error err := p.db.Batch(func(tx *bbolt.Tx) error { bucket, err := fetchPaymentBucket(tx, paymentHash) if err != nil { return err } // Get the existing status of this payment, if any. paymentStatus := fetchPaymentStatus(bucket) // Reset the takeoff error, to avoid carrying over an error // from a previous execution of the batched db transaction. takeoffErr = nil switch paymentStatus { // We allow retrying failed payments. case StatusFailed: // This is a new payment that is being initialized for the // first time. case StatusGrounded: // We already have an InFlight payment on the network. We will // disallow any new payments. case StatusInFlight: takeoffErr = ErrPaymentInFlight return nil // We've already completed a payment to this payment hash, // forbid the switch from sending another. case StatusCompleted: takeoffErr = ErrAlreadyPaid return nil default: takeoffErr = ErrUnknownPaymentStatus return nil } // Obtain a new sequence number for this payment. This is used // to sort the payments in order of creation, and also acts as // a unique identifier for each payment. sequenceNum, err := nextPaymentSequence(tx) if err != nil { return err } err = bucket.Put(paymentSequenceKey, sequenceNum) if err != nil { return err } // We'll move it into the InFlight state. err = bucket.Put(paymentStatusKey, StatusInFlight.Bytes()) if err != nil { return err } // Add the payment info to the bucket, which contains the // static information for this payment err = bucket.Put(paymentCreationInfoKey, infoBytes) if err != nil { return err } // We'll delete any lingering attempt info to start with, in // case we are initializing a payment that was attempted // earlier, but left in a state where we could retry. err = bucket.Delete(paymentAttemptInfoKey) if err != nil { return err } return nil }) if err != nil { return nil } return takeoffErr } // RegisterAttempt atomically records the provided PaymentAttemptInfo to the // DB. func (p *paymentControl) RegisterAttempt(paymentHash lntypes.Hash, attempt *PaymentAttemptInfo) error { // Serialize the information before opening the db transaction. var a bytes.Buffer if err := serializePaymentAttemptInfo(&a, attempt); err != nil { return err } attemptBytes := a.Bytes() var updateErr error err := p.db.Batch(func(tx *bbolt.Tx) error { // Reset the update error, to avoid carrying over an error // from a previous execution of the batched db transaction. updateErr = nil bucket, err := fetchPaymentBucket(tx, paymentHash) if err != nil { return err } // We can only register attempts for payments that are // in-flight. if err := ensureInFlight(bucket); err != nil { updateErr = err return nil } // Add the payment attempt to the payments bucket. return bucket.Put(paymentAttemptInfoKey, attemptBytes) }) if err != nil { return err } return updateErr } // Success transitions a payment into the Completed state. After invoking this // method, InitPayment should always return an error to prevent us from making // duplicate payments to the same payment hash. The provided preimage is // atomically saved to the DB for record keeping. func (p *paymentControl) Success(paymentHash lntypes.Hash, preimage lntypes.Preimage) error { var updateErr error err := p.db.Batch(func(tx *bbolt.Tx) error { // Reset the update error, to avoid carrying over an error // from a previous execution of the batched db transaction. updateErr = nil bucket, err := fetchPaymentBucket(tx, paymentHash) if err != nil { return err } // We can only mark in-flight payments as succeeded. if err := ensureInFlight(bucket); err != nil { updateErr = err return nil } // Record the successful payment info atomically to the // payments record. err = bucket.Put(paymentSettleInfoKey, preimage[:]) if err != nil { return err } return bucket.Put(paymentStatusKey, StatusCompleted.Bytes()) }) if err != nil { return err } return updateErr } // Fail transitions a payment into the Failed state. After invoking this // method, InitPayment should return nil on its next call for this payment // hash, allowing the switch to make a subsequent payment. func (p *paymentControl) Fail(paymentHash lntypes.Hash) error { var updateErr error err := p.db.Batch(func(tx *bbolt.Tx) error { // Reset the update error, to avoid carrying over an error // from a previous execution of the batched db transaction. updateErr = nil bucket, err := fetchPaymentBucket(tx, paymentHash) if err != nil { return err } // We can only mark in-flight payments as failed. if err := ensureInFlight(bucket); err != nil { updateErr = err return nil } // A failed response was received for an InFlight payment, mark // it as Failed to allow subsequent attempts. return bucket.Put(paymentStatusKey, StatusFailed.Bytes()) }) if err != nil { return err } return updateErr } // fetchPaymentBucket fetches or creates the sub-bucket assigned to this // payment hash. func fetchPaymentBucket(tx *bbolt.Tx, paymentHash lntypes.Hash) ( *bbolt.Bucket, error) { payments, err := tx.CreateBucketIfNotExists(paymentsRootBucket) if err != nil { return nil, err } return payments.CreateBucketIfNotExists(paymentHash[:]) } // nextPaymentSequence returns the next sequence number to store for a new // payment. func nextPaymentSequence(tx *bbolt.Tx) ([]byte, error) { payments, err := tx.CreateBucketIfNotExists(paymentsRootBucket) if err != nil { return nil, err } seq, err := payments.NextSequence() if err != nil { return nil, err } b := make([]byte, 8) binary.BigEndian.PutUint64(b, seq) return b, nil } // fetchPaymentStatus fetches the payment status from the bucket. If the // status isn't found, it will default to "StatusGrounded". func fetchPaymentStatus(bucket *bbolt.Bucket) PaymentStatus { // The default status for all payments that aren't recorded in // database. var paymentStatus = StatusGrounded paymentStatusBytes := bucket.Get(paymentStatusKey) if paymentStatusBytes != nil { paymentStatus.FromBytes(paymentStatusBytes) } return paymentStatus } // ensureInFlight checks whether the payment found in the given bucket has // status InFlight, and returns an error otherwise. This should be used to // ensure we only mark in-flight payments as succeeded or failed. func ensureInFlight(bucket *bbolt.Bucket) error { paymentStatus := fetchPaymentStatus(bucket) switch { // The payment was indeed InFlight, return. case paymentStatus == StatusInFlight: return nil // Our records show the payment as unknown, meaning it never // should have left the switch. case paymentStatus == StatusGrounded: return ErrPaymentNotInitiated // The payment succeeded previously. case paymentStatus == StatusCompleted: return ErrPaymentAlreadyCompleted // The payment was already failed. case paymentStatus == StatusFailed: return ErrPaymentAlreadyFailed default: return ErrUnknownPaymentStatus } } // InFlightPayment is a wrapper around a payment that has status InFlight. type InFlightPayment struct { // Info is the PaymentCreationInfo of the in-flight payment. Info *PaymentCreationInfo // Attempt contains information about the last payment attempt that was // made to this payment hash. // // NOTE: Might be nil. Attempt *PaymentAttemptInfo } // FetchInFlightPayments returns all payments with status InFlight. func (p *paymentControl) FetchInFlightPayments() ([]*InFlightPayment, error) { var inFlights []*InFlightPayment err := p.db.View(func(tx *bbolt.Tx) error { payments := tx.Bucket(paymentsRootBucket) if payments == nil { return nil } return payments.ForEach(func(k, _ []byte) error { bucket := payments.Bucket(k) if bucket == nil { return fmt.Errorf("non bucket element") } // If the status is not InFlight, we can return early. paymentStatus := fetchPaymentStatus(bucket) if paymentStatus != StatusInFlight { return nil } var ( inFlight = &InFlightPayment{} err error ) // Get the CreationInfo. b := bucket.Get(paymentCreationInfoKey) if b == nil { return fmt.Errorf("unable to find creation " + "info for inflight payment") } r := bytes.NewReader(b) inFlight.Info, err = deserializePaymentCreationInfo(r) if err != nil { return err } // Now get the attempt info, which may or may not be // available. attempt := bucket.Get(paymentAttemptInfoKey) if attempt != nil { r = bytes.NewReader(attempt) inFlight.Attempt, err = deserializePaymentAttemptInfo(r) if err != nil { return err } } inFlights = append(inFlights, inFlight) return nil }) }) if err != nil { return nil, err } return inFlights, nil }