loop

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 Go to latest Published: Aug 3, 2021 License: MIT Imports: 44 Imported by: 1

README

Lightning Loop

Lightning Loop is a non-custodial service offered by Lightning Labs that makes it easy to move bitcoin into and out of the Lightning Network.

Features

  • Automated channel balancing
  • Privacy-forward non-custodial swaps
  • Opportunistic transaction batching to save on fees
  • Progress monitoring of in-flight swaps

Use Cases

  • Automate channel balancing with AutoLoop (Learn more)
  • Deposit to a Bitcoin address without closing channels with Loop In
  • Convert outbound liquidity into inbound liquidity with Loop Out
  • Refill depleted Lightning channels with Loop In

Installation

Download the latest binaries from the releases page.

Execution

The Loop client needs its own short-lived daemon to facilitate swaps. To start loopd:

loopd

To use Loop in testnet, simply pass the network flag:

loopd --network=testnet

By default loopd attempts to connect to the lnd instance running on localhost:10009 and reads the macaroon and tls certificate from ~/.lnd. This can be altered using command line flags. See loopd --help.

Usage

AutoLoop

AutoLoop makes it easy to keep your channels balanced. Checkout our autoloop documentation for details.

Loop Out

Use Loop Out to move bitcoins on Lightning into an on-chain Bitcoin address.

To execute a Loop Out:

loop out <amt_in_satoshis>

Other notable options:

  • Use the --fast flag to swap immediately (Note: This opts-out of fee savings made possible by transaction batching)
  • Use the --channel flag to loop out on specific channels
  • Use the --addr flag to specify the address the looped out funds should be sent to (Note: By default funds are sent to the lnd wallet)

Run loop monitor to monitor the status of a swap.

Loop In

Use Loop In to convert on-chain bitcoin into spendable Lightning funds.

To execute a Loop In:

loop in <amt_in_satoshis>
More info

For more information about using Loop checkout our Loop FAQs.

Development

Regtest

To get started with local development against a stripped down dummy Loop server running in a local regtest Bitcoin network, take a look at the regtest server environment example documentation.

Testnet

To use Loop in testnet, simply pass the network flag:

loopd --network=testnet
Submit feature requests

The GitHub issue tracker can be used to request specific improvements or report bugs.

Join us on Slack

Join us on the LND Slack and join the #loop channel to ask questions and interact with the community.

LND

Note that Loop requires lnd to be built with all of its subservers. Download the latest official release binary or build lnd from source by following the installation instructions. If you choose to build lnd from source, use the following command to enable all the relevant subservers:

make install tags="signrpc walletrpc chainrpc invoicesrpc"

API

The Loop daemon exposes a gRPC API (defaults to port 11010) and a REST API (defaults to port 8081).

The gRPC and REST connections of loopd are encrypted with TLS and secured with macaroon authentication the same way lnd is.

If no custom loop directory is set then the TLS certificate is stored in ~/.loop/<network>/tls.cert and the base macaroon in ~/.loop/<network>/loop.macaroon.

The loop command will pick up these file automatically on mainnet if no custom loop directory is used. For other networks it should be sufficient to add the --network flag to tell the CLI in what sub directory to look for the files.

For more information on macaroons, see the macaroon documentation of lnd.

NOTE: Loop's macaroons are independent from lnd's. The same macaroon cannot be used for both loopd and lnd.

Build from source

If you’d prefer to build from source:

git clone https://github.com/lightninglabs/loop.git
cd loop/cmd
go install ./...

Documentation

Index

Constants

This section is empty.

Variables

View Source 
var (
	// ErrSwapFeeTooHigh is returned when the swap invoice amount is too
	// high.
	ErrSwapFeeTooHigh = errors.New("swap fee too high")

	// ErrPrepayAmountTooHigh is returned when the prepay invoice amount is
	// too high.
	ErrPrepayAmountTooHigh = errors.New("prepay amount too high")

	// ErrSwapAmountTooLow is returned when the requested swap amount is
	// less than the server minimum.
	ErrSwapAmountTooLow = errors.New("swap amount too low")

	// ErrSwapAmountTooHigh is returned when the requested swap amount is
	// more than the server maximum.
	ErrSwapAmountTooHigh = errors.New("swap amount too high")

	// ErrExpiryTooFar is returned when the server proposes an expiry that
	// is too soon for us.
	ErrExpiryTooFar = errors.New("swap expiry too far")

	// MinerFeeEstimationFailed is a magic number that is returned in a
	// quote call as the miner fee if the fee estimation in lnd's wallet
	// failed because of insufficient funds.
	MinerFeeEstimationFailed btcutil.Amount = -1
)
View Source 
var (
	// MaxLoopInAcceptDelta configures the maximum acceptable number of
	// remaining blocks until the on-chain htlc expires. This value is used
	// to decide whether we want to continue with the swap parameters as
	// proposed by the server. It is a protection to prevent the server from
	// getting us to lock up our funds to an arbitrary point in the future.
	MaxLoopInAcceptDelta = int32(1500)

	// MinLoopInPublishDelta defines the minimum number of remaining blocks
	// until on-chain htlc expiry required to proceed to publishing the htlc
	// tx. This value isn't critical, as we could even safely publish the
	// htlc after expiry. The reason we do implement this check is to
	// prevent us from publishing an htlc that the server surely wouldn't
	// follow up to.
	MinLoopInPublishDelta = int32(10)

	// TimeoutTxConfTarget defines the confirmation target for the loop in
	// timeout tx.
	TimeoutTxConfTarget = int32(2)
)
View Source 
var (
	// MinLoopOutPreimageRevealDelta configures the minimum number of
	// remaining blocks before htlc expiry required to reveal preimage.
	MinLoopOutPreimageRevealDelta int32 = 20

	// DefaultSweepConfTarget is the default confirmation target we'll use
	// when sweeping on-chain HTLCs.
	DefaultSweepConfTarget int32 = 9

	// DefaultHtlcConfTarget is the default confirmation target we'll use
	// for on-chain htlcs published by the swap client for Loop In.
	DefaultHtlcConfTarget int32 = 6

	// DefaultSweepConfTargetDelta is the delta of blocks from a Loop Out
	// swap's expiration height at which we begin to use the default sweep
	// confirmation target.
	//
	// TODO(wilmer): tune?
	DefaultSweepConfTargetDelta = DefaultSweepConfTarget * 2
)
View Source 
var AgentName = defaultAgentName

AgentName stores the name of the software that is added as the first part of the user agent string. This defaults to the value "loopd" when being run as a standalone component but can be overwritten by LiT for example when loopd is integrated into the UI.

View Source 
var Commit string

Commit stores the current commit hash of this build, this should be set using the -ldflags during compilation.

Functions

func GetHtlcScriptVersion 

func GetHtlcScriptVersion(
	protocolVersion loopdb.ProtocolVersion) swap.ScriptVersion

GetHtlcScriptVersion returns the correct HTLC script version for the passed protocol version.

func UseLogger 

func UseLogger(logger btclog.Logger)

UseLogger uses a specified Logger to output package logging info. This should be used in preference to SetLogWriter if the caller is also using btclog.

func UserAgent 

func UserAgent(initiator string) string

UserAgent returns the full user agent string that identifies the software that is submitting swaps to the loop server.

func Version 

func Version() string

Version returns the application version as a properly formed string per the semantic versioning 2.0.0 spec (http://semver.org/) and the commit it was built on.

Types

type Client 

type Client struct {
	// contains filtered or unexported fields
}

Client performs the client side part of swaps. This interface exists to be able to implement a stub.

func NewClient 

func NewClient(dbDir string, cfg *ClientConfig) (*Client, func(), error)

NewClient returns a new instance to initiate swaps with.

func (*Client) FetchSwaps 

func (s *Client) FetchSwaps() ([]*SwapInfo, error)

FetchSwaps returns all loop in and out swaps currently in the database.

func (*Client) LoopIn 

func (s *Client) LoopIn(globalCtx context.Context,
	request *LoopInRequest) (*LoopInSwapInfo, error)

LoopIn initiates a loop in swap.

func (*Client) LoopInQuote 

func (s *Client) LoopInQuote(ctx context.Context,
	request *LoopInQuoteRequest) (*LoopInQuote, error)

LoopInQuote takes an amount and returns a break down of estimated costs for the client. Both the swap server and the on-chain fee estimator are queried to get to build the quote response.

func (*Client) LoopInTerms 

func (s *Client) LoopInTerms(ctx context.Context) (
	*LoopInTerms, error)

LoopInTerms returns the terms on which the server executes swaps.

func (*Client) LoopOut 

func (s *Client) LoopOut(globalCtx context.Context,
	request *OutRequest) (*LoopOutSwapInfo, error)

LoopOut initiates a loop out swap. It blocks until the swap is initiation with the swap server is completed (typically this takes only a short amount of time). From there on further status information can be acquired through the status channel returned from the Run call.

When the call returns, the swap has been persisted and will be resumed automatically after restarts.

The return value is a hash that uniquely identifies the new swap.

func (*Client) LoopOutQuote 

func (s *Client) LoopOutQuote(ctx context.Context,
	request *LoopOutQuoteRequest) (*LoopOutQuote, error)

LoopOutQuote takes a LoopOut amount and returns a break down of estimated costs for the client. Both the swap server and the on-chain fee estimator are queried to get to build the quote response.

func (*Client) LoopOutTerms 

func (s *Client) LoopOutTerms(ctx context.Context) (
	*LoopOutTerms, error)

LoopOutTerms returns the terms on which the server executes swaps.

func (*Client) Probe 

func (s *Client) Probe(ctx context.Context, req *ProbeRequest) error

Probe asks the server to probe a route to us given a requested amount and last hop. The server is free to discard frequent request to avoid abuse or if there's been a recent probe to us for the same amount.

func (*Client) Run 

func (s *Client) Run(ctx context.Context,
	statusChan chan<- SwapInfo) error

Run is a blocking call that executes all swaps. Any pending swaps are restored from persistent storage and resumed. Subsequent updates will be sent through the passed in statusChan. The function can be terminated by cancelling the context.

type ClientConfig 

type ClientConfig struct {
	// ServerAddress is the loop server to connect to.
	ServerAddress string

	// ProxyAddress is the SOCKS proxy that should be used to establish the
	// connection.
	ProxyAddress string

	// SwapServerNoTLS skips TLS for the swap server connection when set.
	SwapServerNoTLS bool

	// TLSPathServer is the path to the TLS certificate that is required to
	// connect to the server.
	TLSPathServer string

	// Lnd is an instance of the lnd proxy.
	Lnd *lndclient.LndServices

	// MaxLsatCost is the maximum price we are willing to pay to the server
	// for the token.
	MaxLsatCost btcutil.Amount

	// MaxLsatFee is the maximum that we are willing to pay in routing fees
	// to obtain the token.
	MaxLsatFee btcutil.Amount

	// LoopOutMaxParts defines the maximum number of parts that may be used
	// for a loop out swap. When greater than one, a multi-part payment may
	// be attempted.
	LoopOutMaxParts uint32
}

ClientConfig is the exported configuration structure that is required to instantiate the loop client.

type In 

type In struct {
	loopdb.LoopInContract

	SwapInfoKit

	// State where the swap is in.
	State loopdb.SwapState
}

In contains status information for a loop in swap.

func (*In) LastUpdate 

func (s *In) LastUpdate() time.Time

LastUpdate returns the last update time of the swap

func (*In) SwapHash 

func (s *In) SwapHash() lntypes.Hash

SwapHash returns the swap hash.

type LoopInQuote 

type LoopInQuote struct {
	// SwapFee is the fee that the swap server is charging for the swap.
	SwapFee btcutil.Amount

	// MinerFee is an estimate of the on-chain fee that needs to be paid to
	// sweep the htlc.
	MinerFee btcutil.Amount

	// Time lock delta relative to current block height that swap server
	// will accept on the swap initiation call.
	CltvDelta int32
}

LoopInQuote contains estimates for the fees making up the total swap cost for the client.

type LoopInQuoteRequest 

type LoopInQuoteRequest struct {
	// Amount specifies the requested swap amount in sat. This does not
	// include the swap and miner fee.
	Amount btcutil.Amount

	// HtlcConfTarget specifies the targeted confirmation target for the
	// client sweep tx.
	HtlcConfTarget int32

	// ExternalHtlc specifies whether the htlc is published by an external
	// source.
	ExternalHtlc bool

	// LastHop is an optional last hop to use. This last hop is used when
	// the client has already requested a server probe for more accurate
	// routing fee estimation.
	LastHop *route.Vertex

	// RouteHints are optional route hints to reach the destination through
	// private channels.
	RouteHints [][]zpay32.HopHint
}

LoopInQuoteRequest specifies the swap parameters for which a quote is requested.

type LoopInRequest 

type LoopInRequest struct {
	// Amount specifies the requested swap amount in sat. This does not
	// include the swap and miner fee.
	Amount btcutil.Amount

	// MaxSwapFee is the maximum we are willing to pay the server for the
	// swap. This value is not disclosed in the swap initiation call, but if
	// the server asks for a higher fee, we abort the swap. Typically this
	// value is taken from the response of the LoopInQuote call. It
	// includes the prepay amount.
	MaxSwapFee btcutil.Amount

	// MaxMinerFee is the maximum in on-chain fees that we are willing to
	// spent. If we publish the on-chain htlc and the fee estimate turns out
	// higher than this value, we cancel the swap.
	//
	// MaxMinerFee is typically taken from the response of the LoopInQuote
	// call.
	MaxMinerFee btcutil.Amount

	// HtlcConfTarget specifies the targeted confirmation target for the
	// client htlc tx.
	HtlcConfTarget int32

	// LastHop optionally specifies the last hop to use for the loop in
	// payment.
	LastHop *route.Vertex

	// ExternalHtlc specifies whether the htlc is published by an external
	// source.
	ExternalHtlc bool

	// Label contains an optional label for the swap.
	Label string

	// Initiator is an optional string that identifies what software
	// initiated the swap (loop CLI, autolooper, LiT UI and so on) and is
	// appended to the user agent string.
	Initiator string
}

LoopInRequest contains the required parameters for the swap.

type LoopInSwapInfo 

type LoopInSwapInfo struct {
	// SwapHash contains the sha256 hash of the swap preimage.
	SwapHash lntypes.Hash

	// HtlcAddressP2WSH contains the native segwit swap htlc address,
	// where the loop-in funds may be paid.
	HtlcAddressP2WSH btcutil.Address

	// HtlcAddressNP2WSH contains the nested segwit swap htlc address,
	// where the loop-in funds may be paid.
	HtlcAddressNP2WSH btcutil.Address

	// ServerMessages is the human-readable message received from the loop
	// server.
	ServerMessage string
}

LoopInSwapInfo contains essential information of a loop-in swap after the swap is initiated.

type LoopInTerms 

type LoopInTerms struct {
	// MinSwapAmount is the minimum amount that the server requires for a
	// swap.
	MinSwapAmount btcutil.Amount

	// MaxSwapAmount is the maximum amount that the server accepts for a
	// swap.
	MaxSwapAmount btcutil.Amount
}

LoopInTerms are the server terms on which it executes loop in swaps.

type LoopOutQuote 

type LoopOutQuote struct {
	// SwapFee is the fee that the swap server is charging for the swap.
	SwapFee btcutil.Amount

	// PrepayAmount is the part of the swap fee that is requested as a
	// prepayment.
	PrepayAmount btcutil.Amount

	// MinerFee is an estimate of the on-chain fee that needs to be paid to
	// sweep the htlc.
	MinerFee btcutil.Amount

	// SwapPaymentDest is the node pubkey where to swap payment needs to be
	// sent to.
	SwapPaymentDest [33]byte
}

LoopOutQuote contains estimates for the fees making up the total swap cost for the client.

type LoopOutQuoteRequest 

type LoopOutQuoteRequest struct {
	// Amount specifies the requested swap amount in sat. This does not
	// include the swap and miner fee.
	Amount btcutil.Amount

	// SweepConfTarget specifies the targeted confirmation target for the
	// client sweep tx.
	SweepConfTarget int32

	// SwapPublicationDeadline can be set by the client to allow the server
	// delaying publication of the swap HTLC to save on chain fees.
	SwapPublicationDeadline time.Time
}

LoopOutQuoteRequest specifies the swap parameters for which a quote is requested.

type LoopOutSwapInfo 

type LoopOutSwapInfo struct {
	// SwapHash contains the sha256 hash of the swap preimage.
	SwapHash lntypes.Hash

	// HtlcAddressP2WSH contains the native segwit swap htlc address that
	// the server will publish to.
	HtlcAddressP2WSH btcutil.Address

	// ServerMessages is the human-readable message received from the loop
	// server.
	ServerMessage string
}

LoopOutSwapInfo contains essential information of a loop-out swap after the swap is initiated.

type LoopOutTerms 

type LoopOutTerms struct {
	// MinSwapAmount is the minimum amount that the server requires for a
	// swap.
	MinSwapAmount btcutil.Amount

	// MaxSwapAmount is the maximum amount that the server accepts for a
	// swap.
	MaxSwapAmount btcutil.Amount

	// MinCltvDelta is the minimum expiry delta for loop out swaps.
	MinCltvDelta int32

	// MaxCltvDelta is the maximum expiry delta for loop out swaps.
	MaxCltvDelta int32
}

LoopOutTerms are the server terms on which it executes swaps.

type Out 

type Out struct {
	// LoopOutContract describes the details of this loop.Out. Using these
	// details,the full swap can be executed.
	loopdb.LoopOutContract

	// State is the current state of the target swap.
	State loopdb.SwapState

	// SwapInfoKit contains shared data amongst all swap types.
	SwapInfoKit
}

Out contains the full details of a loop out request. This includes things like the payment hash, the total value, and the final CTLV delay of the swap. We'll use this to track an active swap throughout that various swap stages.

type OutRequest 

type OutRequest struct {
	// Amount specifies the requested swap amount in sat. This does not
	// include the swap and miner fee.
	Amount btcutil.Amount

	// Destination address for the swap.
	DestAddr btcutil.Address

	// MaxSwapRoutingFee is the maximum off-chain fee in msat that may be
	// paid for payment to the server. This limit is applied during path
	// finding. Typically this value is taken from the response of the
	// LoopOutQuote call.
	MaxSwapRoutingFee btcutil.Amount

	// MaxPrepayRoutingFee is the maximum off-chain fee in msat that may be
	// paid for payment to the server. This limit is applied during path
	// finding. Typically this value is taken from the response of the
	// LoopOutQuote call.
	MaxPrepayRoutingFee btcutil.Amount

	// MaxSwapFee is the maximum we are willing to pay the server for the
	// swap. This value is not disclosed in the swap initiation call, but
	// if the server asks for a higher fee, we abort the swap. Typically
	// this value is taken from the response of the LoopOutQuote call. It
	// includes the prepay amount.
	MaxSwapFee btcutil.Amount

	// MaxPrepayAmount is the maximum amount of the swap fee that may be
	// charged as a prepayment.
	MaxPrepayAmount btcutil.Amount

	// MaxMinerFee is the maximum in on-chain fees that we are willing to
	// spent. If we want to sweep the on-chain htlc and the fee estimate
	// turns out higher than this value, we cancel the swap. If the fee
	// estimate is lower, we publish the sweep tx.
	//
	// If the sweep tx isn't confirmed, we are forced to ratchet up fees
	// until it is swept. Possibly even exceeding MaxMinerFee if we get
	// close to the htlc timeout. Because the initial publication revealed
	// the preimage, we have no other choice. The server may already have
	// pulled the off-chain htlc. Only when the fee becomes higher than the
	// swap amount, we can only wait for fees to come down and hope - if we
	// are past the timeout - that the server isn't publishing the
	// revocation.
	//
	// MaxMinerFee is typically taken from the response of the
	// LoopOutQuote call.
	MaxMinerFee btcutil.Amount

	// SweepConfTarget specifies the targeted confirmation target for the
	// client sweep tx.
	SweepConfTarget int32

	// HtlcConfirmations specifies the number of confirmations we require
	// for on chain loop out htlcs.
	HtlcConfirmations int32

	// OutgoingChanSet optionally specifies the short channel ids of the
	// channels that may be used to loop out.
	OutgoingChanSet loopdb.ChannelSet

	// SwapPublicationDeadline can be set by the client to allow the server
	// delaying publication of the swap HTLC to save on chain fees.
	SwapPublicationDeadline time.Time

	// Expiry is the absolute expiry height of the on-chain htlc.
	Expiry int32

	// Label contains an optional label for the swap.
	Label string

	// Initiator is an optional string that identifies what software
	// initiated the swap (loop CLI, autolooper, LiT UI and so on) and is
	// appended to the user agent string.
	Initiator string
}

OutRequest contains the required parameters for a loop out swap.

type ProbeRequest 

type ProbeRequest struct {
	// Amount is the amount that will be probed.
	Amount btcutil.Amount

	// LastHop is the last hop along the route.
	LastHop *route.Vertex

	// Optional hop hints.
	RouteHints [][]zpay32.HopHint
}

ProbeRequest specifies probe parameters for the server probe.

type ServerUpdate 

type ServerUpdate struct {
	// State is the state that the server has sent us.
	State looprpc.ServerSwapState

	// Timestamp is the time of the server state update.
	Timestamp time.Time
}

ServerUpdate summarizes an update from the swap server.

type SwapInfo 

type SwapInfo struct {
	loopdb.SwapStateData

	loopdb.SwapContract

	// LastUpdateTime is the time of the last state change.
	LastUpdate time.Time

	// SwapHash stores the swap preimage hash.
	SwapHash lntypes.Hash

	// SwapType describes whether this is a loop in or loop out swap.
	SwapType swap.Type

	// HtlcAddressP2WSH stores the address of the P2WSH (native segwit)
	// swap htlc. This is used for both loop-in and loop-out.
	HtlcAddressP2WSH btcutil.Address

	// HtlcAddressNP2WSH stores the address of the NP2WSH (nested segwit)
	// swap htlc. This is only used for external loop-in.
	HtlcAddressNP2WSH btcutil.Address

	// ExternalHtlc is set to true for external loop-in swaps.
	ExternalHtlc bool
}

SwapInfo exposes common info fields for loop in and loop out swaps.

type SwapInfoKit 

type SwapInfoKit struct {
	// Hash is the sha256 hash of the preimage that unlocks the htlcs. It
	// is used to uniquely identify this swap.
	Hash lntypes.Hash

	// LastUpdateTime is the time of the last update of this swap.
	LastUpdateTime time.Time
}

SwapInfoKit contains common swap info fields.

Source Files

View all Source files

Directories

Path Synopsis
cmd
loop
loopd
Package liquidity is responsible for monitoring our node's liquidity.
 Package liquidity is responsible for monitoring our node's liquidity.
Package looprpc is a reverse proxy.
 Package looprpc is a reverse proxy.

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