channel.go

package migration_01_to_11

import (
	"errors"
	"fmt"
	"io"
	"strconv"
	"strings"
	"sync"

	"github.com/btcsuite/btcd/btcec"
	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/wire"
	"github.com/btcsuite/btcutil"
	"github.com/lightningnetwork/lnd/keychain"
	"github.com/lightningnetwork/lnd/lnwire"
	"github.com/lightningnetwork/lnd/shachain"
)

var (
	// closedChannelBucket stores summarization information concerning
	// previously open, but now closed channels.
	closedChannelBucket = []byte("closed-chan-bucket")

	// openChanBucket stores all the currently open channels. This bucket
	// has a second, nested bucket which is keyed by a node's ID. Within
	// that node ID bucket, all attributes required to track, update, and
	// close a channel are stored.
	//
	// openChan -> nodeID -> chanPoint
	//
	// TODO(roasbeef): flesh out comment
	openChannelBucket = []byte("open-chan-bucket")
)

// ChannelType is an enum-like type that describes one of several possible
// channel types. Each open channel is associated with a particular type as the
// channel type may determine how higher level operations are conducted such as
// fee negotiation, channel closing, the format of HTLCs, etc.
// TODO(roasbeef): split up per-chain?
type ChannelType uint8

const (
	// NOTE: iota isn't used here for this enum needs to be stable
	// long-term as it will be persisted to the database.

	// SingleFunder represents a channel wherein one party solely funds the
	// entire capacity of the channel.
	SingleFunder ChannelType = 0
)

// ChannelConstraints represents a set of constraints meant to allow a node to
// limit their exposure, enact flow control and ensure that all HTLCs are
// economically relevant. This struct will be mirrored for both sides of the
// channel, as each side will enforce various constraints that MUST be adhered
// to for the life time of the channel. The parameters for each of these
// constraints are static for the duration of the channel, meaning the channel
// must be torn down for them to change.
type ChannelConstraints struct {
	// DustLimit is the threshold (in satoshis) below which any outputs
	// should be trimmed. When an output is trimmed, it isn't materialized
	// as an actual output, but is instead burned to miner's fees.
	DustLimit btcutil.Amount

	// ChanReserve is an absolute reservation on the channel for the
	// owner of this set of constraints. This means that the current
	// settled balance for this node CANNOT dip below the reservation
	// amount. This acts as a defense against costless attacks when
	// either side no longer has any skin in the game.
	ChanReserve btcutil.Amount

	// MaxPendingAmount is the maximum pending HTLC value that the
	// owner of these constraints can offer the remote node at a
	// particular time.
	MaxPendingAmount lnwire.MilliSatoshi

	// MinHTLC is the minimum HTLC value that the owner of these
	// constraints can offer the remote node. If any HTLCs below this
	// amount are offered, then the HTLC will be rejected. This, in
	// tandem with the dust limit allows a node to regulate the
	// smallest HTLC that it deems economically relevant.
	MinHTLC lnwire.MilliSatoshi

	// MaxAcceptedHtlcs is the maximum number of HTLCs that the owner of
	// this set of constraints can offer the remote node. This allows each
	// node to limit their over all exposure to HTLCs that may need to be
	// acted upon in the case of a unilateral channel closure or a contract
	// breach.
	MaxAcceptedHtlcs uint16

	// CsvDelay is the relative time lock delay expressed in blocks. Any
	// settled outputs that pay to the owner of this channel configuration
	// MUST ensure that the delay branch uses this value as the relative
	// time lock. Similarly, any HTLC's offered by this node should use
	// this value as well.
	CsvDelay uint16
}

// ChannelConfig is a struct that houses the various configuration opens for
// channels. Each side maintains an instance of this configuration file as it
// governs: how the funding and commitment transaction to be created, the
// nature of HTLC's allotted, the keys to be used for delivery, and relative
// time lock parameters.
type ChannelConfig struct {
	// ChannelConstraints is the set of constraints that must be upheld for
	// the duration of the channel for the owner of this channel
	// configuration. Constraints govern a number of flow control related
	// parameters, also including the smallest HTLC that will be accepted
	// by a participant.
	ChannelConstraints

	// MultiSigKey is the key to be used within the 2-of-2 output script
	// for the owner of this channel config.
	MultiSigKey keychain.KeyDescriptor

	// RevocationBasePoint is the base public key to be used when deriving
	// revocation keys for the remote node's commitment transaction. This
	// will be combined along with a per commitment secret to derive a
	// unique revocation key for each state.
	RevocationBasePoint keychain.KeyDescriptor

	// PaymentBasePoint is the base public key to be used when deriving
	// the key used within the non-delayed pay-to-self output on the
	// commitment transaction for a node. This will be combined with a
	// tweak derived from the per-commitment point to ensure unique keys
	// for each commitment transaction.
	PaymentBasePoint keychain.KeyDescriptor

	// DelayBasePoint is the base public key to be used when deriving the
	// key used within the delayed pay-to-self output on the commitment
	// transaction for a node. This will be combined with a tweak derived
	// from the per-commitment point to ensure unique keys for each
	// commitment transaction.
	DelayBasePoint keychain.KeyDescriptor

	// HtlcBasePoint is the base public key to be used when deriving the
	// local HTLC key. The derived key (combined with the tweak derived
	// from the per-commitment point) is used within the "to self" clause
	// within any HTLC output scripts.
	HtlcBasePoint keychain.KeyDescriptor
}

// ChannelCommitment is a snapshot of the commitment state at a particular
// point in the commitment chain. With each state transition, a snapshot of the
// current state along with all non-settled HTLCs are recorded. These snapshots
// detail the state of the _remote_ party's commitment at a particular state
// number.  For ourselves (the local node) we ONLY store our most recent
// (unrevoked) state for safety purposes.
type ChannelCommitment struct {
	// CommitHeight is the update number that this ChannelDelta represents
	// the total number of commitment updates to this point. This can be
	// viewed as sort of a "commitment height" as this number is
	// monotonically increasing.
	CommitHeight uint64

	// LocalLogIndex is the cumulative log index index of the local node at
	// this point in the commitment chain. This value will be incremented
	// for each _update_ added to the local update log.
	LocalLogIndex uint64

	// LocalHtlcIndex is the current local running HTLC index. This value
	// will be incremented for each outgoing HTLC the local node offers.
	LocalHtlcIndex uint64

	// RemoteLogIndex is the cumulative log index index of the remote node
	// at this point in the commitment chain. This value will be
	// incremented for each _update_ added to the remote update log.
	RemoteLogIndex uint64

	// RemoteHtlcIndex is the current remote running HTLC index. This value
	// will be incremented for each outgoing HTLC the remote node offers.
	RemoteHtlcIndex uint64

	// LocalBalance is the current available settled balance within the
	// channel directly spendable by us.
	LocalBalance lnwire.MilliSatoshi

	// RemoteBalance is the current available settled balance within the
	// channel directly spendable by the remote node.
	RemoteBalance lnwire.MilliSatoshi

	// CommitFee is the amount calculated to be paid in fees for the
	// current set of commitment transactions. The fee amount is persisted
	// with the channel in order to allow the fee amount to be removed and
	// recalculated with each channel state update, including updates that
	// happen after a system restart.
	CommitFee btcutil.Amount

	// FeePerKw is the min satoshis/kilo-weight that should be paid within
	// the commitment transaction for the entire duration of the channel's
	// lifetime. This field may be updated during normal operation of the
	// channel as on-chain conditions change.
	//
	// TODO(halseth): make this SatPerKWeight. Cannot be done atm because
	// this will cause the import cycle lnwallet<->channeldb. Fee
	// estimation stuff should be in its own package.
	FeePerKw btcutil.Amount

	// CommitTx is the latest version of the commitment state, broadcast
	// able by us.
	CommitTx *wire.MsgTx

	// CommitSig is one half of the signature required to fully complete
	// the script for the commitment transaction above. This is the
	// signature signed by the remote party for our version of the
	// commitment transactions.
	CommitSig []byte

	// Htlcs is the set of HTLC's that are pending at this particular
	// commitment height.
	Htlcs []HTLC

	// TODO(roasbeef): pending commit pointer?
	//  * lets just walk through
}

// ChannelStatus is a bit vector used to indicate whether an OpenChannel is in
// the default usable state, or a state where it shouldn't be used.
type ChannelStatus uint8

var (
	// ChanStatusDefault is the normal state of an open channel.
	ChanStatusDefault ChannelStatus

	// ChanStatusBorked indicates that the channel has entered an
	// irreconcilable state, triggered by a state desynchronization or
	// channel breach.  Channels in this state should never be added to the
	// htlc switch.
	ChanStatusBorked ChannelStatus = 1

	// ChanStatusCommitBroadcasted indicates that a commitment for this
	// channel has been broadcasted.
	ChanStatusCommitBroadcasted ChannelStatus = 1 << 1

	// ChanStatusLocalDataLoss indicates that we have lost channel state
	// for this channel, and broadcasting our latest commitment might be
	// considered a breach.
	//
	// TODO(halseh): actually enforce that we are not force closing such a
	// channel.
	ChanStatusLocalDataLoss ChannelStatus = 1 << 2

	// ChanStatusRestored is a status flag that signals that the channel
	// has been restored, and doesn't have all the fields a typical channel
	// will have.
	ChanStatusRestored ChannelStatus = 1 << 3
)

// chanStatusStrings maps a ChannelStatus to a human friendly string that
// describes that status.
var chanStatusStrings = map[ChannelStatus]string{
	ChanStatusDefault:           "ChanStatusDefault",
	ChanStatusBorked:            "ChanStatusBorked",
	ChanStatusCommitBroadcasted: "ChanStatusCommitBroadcasted",
	ChanStatusLocalDataLoss:     "ChanStatusLocalDataLoss",
	ChanStatusRestored:          "ChanStatusRestored",
}

// orderedChanStatusFlags is an in-order list of all that channel status flags.
var orderedChanStatusFlags = []ChannelStatus{
	ChanStatusDefault,
	ChanStatusBorked,
	ChanStatusCommitBroadcasted,
	ChanStatusLocalDataLoss,
	ChanStatusRestored,
}

// String returns a human-readable representation of the ChannelStatus.
func (c ChannelStatus) String() string {
	// If no flags are set, then this is the default case.
	if c == 0 {
		return chanStatusStrings[ChanStatusDefault]
	}

	// Add individual bit flags.
	statusStr := ""
	for _, flag := range orderedChanStatusFlags {
		if c&flag == flag {
			statusStr += chanStatusStrings[flag] + "|"
			c -= flag
		}
	}

	// Remove anything to the right of the final bar, including it as well.
	statusStr = strings.TrimRight(statusStr, "|")

	// Add any remaining flags which aren't accounted for as hex.
	if c != 0 {
		statusStr += "|0x" + strconv.FormatUint(uint64(c), 16)
	}

	// If this was purely an unknown flag, then remove the extra bar at the
	// start of the string.
	statusStr = strings.TrimLeft(statusStr, "|")

	return statusStr
}

// OpenChannel encapsulates the persistent and dynamic state of an open channel
// with a remote node. An open channel supports several options for on-disk
// serialization depending on the exact context. Full (upon channel creation)
// state commitments, and partial (due to a commitment update) writes are
// supported. Each partial write due to a state update appends the new update
// to an on-disk log, which can then subsequently be queried in order to
// "time-travel" to a prior state.
type OpenChannel struct {
	// ChanType denotes which type of channel this is.
	ChanType ChannelType

	// ChainHash is a hash which represents the blockchain that this
	// channel will be opened within. This value is typically the genesis
	// hash. In the case that the original chain went through a contentious
	// hard-fork, then this value will be tweaked using the unique fork
	// point on each branch.
	ChainHash chainhash.Hash

	// FundingOutpoint is the outpoint of the final funding transaction.
	// This value uniquely and globally identifies the channel within the
	// target blockchain as specified by the chain hash parameter.
	FundingOutpoint wire.OutPoint

	// ShortChannelID encodes the exact location in the chain in which the
	// channel was initially confirmed. This includes: the block height,
	// transaction index, and the output within the target transaction.
	ShortChannelID lnwire.ShortChannelID

	// IsPending indicates whether a channel's funding transaction has been
	// confirmed.
	IsPending bool

	// IsInitiator is a bool which indicates if we were the original
	// initiator for the channel. This value may affect how higher levels
	// negotiate fees, or close the channel.
	IsInitiator bool

	// FundingBroadcastHeight is the height in which the funding
	// transaction was broadcast. This value can be used by higher level
	// sub-systems to determine if a channel is stale and/or should have
	// been confirmed before a certain height.
	FundingBroadcastHeight uint32

	// NumConfsRequired is the number of confirmations a channel's funding
	// transaction must have received in order to be considered available
	// for normal transactional use.
	NumConfsRequired uint16

	// ChannelFlags holds the flags that were sent as part of the
	// open_channel message.
	ChannelFlags lnwire.FundingFlag

	// IdentityPub is the identity public key of the remote node this
	// channel has been established with.
	IdentityPub *btcec.PublicKey

	// Capacity is the total capacity of this channel.
	Capacity btcutil.Amount

	// TotalMSatSent is the total number of milli-satoshis we've sent
	// within this channel.
	TotalMSatSent lnwire.MilliSatoshi

	// TotalMSatReceived is the total number of milli-satoshis we've
	// received within this channel.
	TotalMSatReceived lnwire.MilliSatoshi

	// LocalChanCfg is the channel configuration for the local node.
	LocalChanCfg ChannelConfig

	// RemoteChanCfg is the channel configuration for the remote node.
	RemoteChanCfg ChannelConfig

	// LocalCommitment is the current local commitment state for the local
	// party. This is stored distinct from the state of the remote party
	// as there are certain asymmetric parameters which affect the
	// structure of each commitment.
	LocalCommitment ChannelCommitment

	// RemoteCommitment is the current remote commitment state for the
	// remote party. This is stored distinct from the state of the local
	// party as there are certain asymmetric parameters which affect the
	// structure of each commitment.
	RemoteCommitment ChannelCommitment

	// RemoteCurrentRevocation is the current revocation for their
	// commitment transaction. However, since this the derived public key,
	// we don't yet have the private key so we aren't yet able to verify
	// that it's actually in the hash chain.
	RemoteCurrentRevocation *btcec.PublicKey

	// RemoteNextRevocation is the revocation key to be used for the *next*
	// commitment transaction we create for the local node. Within the
	// specification, this value is referred to as the
	// per-commitment-point.
	RemoteNextRevocation *btcec.PublicKey

	// RevocationProducer is used to generate the revocation in such a way
	// that remote side might store it efficiently and have the ability to
	// restore the revocation by index if needed. Current implementation of
	// secret producer is shachain producer.
	RevocationProducer shachain.Producer

	// RevocationStore is used to efficiently store the revocations for
	// previous channels states sent to us by remote side. Current
	// implementation of secret store is shachain store.
	RevocationStore shachain.Store

	// FundingTxn is the transaction containing this channel's funding
	// outpoint. Upon restarts, this txn will be rebroadcast if the channel
	// is found to be pending.
	//
	// NOTE: This value will only be populated for single-funder channels
	// for which we are the initiator.
	FundingTxn *wire.MsgTx

	// TODO(roasbeef): eww
	Db *DB

	// TODO(roasbeef): just need to store local and remote HTLC's?

	sync.RWMutex
}

// ShortChanID returns the current ShortChannelID of this channel.
func (c *OpenChannel) ShortChanID() lnwire.ShortChannelID {
	c.RLock()
	defer c.RUnlock()

	return c.ShortChannelID
}

// HTLC is the on-disk representation of a hash time-locked contract. HTLCs are
// contained within ChannelDeltas which encode the current state of the
// commitment between state updates.
//
// TODO(roasbeef): save space by using smaller ints at tail end?
type HTLC struct {
	// Signature is the signature for the second level covenant transaction
	// for this HTLC. The second level transaction is a timeout tx in the
	// case that this is an outgoing HTLC, and a success tx in the case
	// that this is an incoming HTLC.
	//
	// TODO(roasbeef): make [64]byte instead?
	Signature []byte

	// RHash is the payment hash of the HTLC.
	RHash [32]byte

	// Amt is the amount of milli-satoshis this HTLC escrows.
	Amt lnwire.MilliSatoshi

	// RefundTimeout is the absolute timeout on the HTLC that the sender
	// must wait before reclaiming the funds in limbo.
	RefundTimeout uint32

	// OutputIndex is the output index for this particular HTLC output
	// within the commitment transaction.
	OutputIndex int32

	// Incoming denotes whether we're the receiver or the sender of this
	// HTLC.
	Incoming bool

	// OnionBlob is an opaque blob which is used to complete multi-hop
	// routing.
	OnionBlob []byte

	// HtlcIndex is the HTLC counter index of this active, outstanding
	// HTLC. This differs from the LogIndex, as the HtlcIndex is only
	// incremented for each offered HTLC, while they LogIndex is
	// incremented for each update (includes settle+fail).
	HtlcIndex uint64

	// LogIndex is the cumulative log index of this HTLC. This differs
	// from the HtlcIndex as this will be incremented for each new log
	// update added.
	LogIndex uint64
}

// CircuitKey is used by a channel to uniquely identify the HTLCs it receives
// from the switch, and is used to purge our in-memory state of HTLCs that have
// already been processed by a link. Two list of CircuitKeys are included in
// each CommitDiff to allow a link to determine which in-memory htlcs directed
// the opening and closing of circuits in the switch's circuit map.
type CircuitKey struct {
	// ChanID is the short chanid indicating the HTLC's origin.
	//
	// NOTE: It is fine for this value to be blank, as this indicates a
	// locally-sourced payment.
	ChanID lnwire.ShortChannelID

	// HtlcID is the unique htlc index predominately assigned by links,
	// though can also be assigned by switch in the case of locally-sourced
	// payments.
	HtlcID uint64
}

// String returns a string representation of the CircuitKey.
func (k CircuitKey) String() string {
	return fmt.Sprintf("(Chan ID=%s, HTLC ID=%d)", k.ChanID, k.HtlcID)
}

// ClosureType is an enum like structure that details exactly _how_ a channel
// was closed. Three closure types are currently possible: none, cooperative,
// local force close, remote force close, and (remote) breach.
type ClosureType uint8

const (
	// RemoteForceClose indicates that the remote peer has unilaterally
	// broadcast their current commitment state on-chain.
	RemoteForceClose ClosureType = 4
)

// ChannelCloseSummary contains the final state of a channel at the point it
// was closed. Once a channel is closed, all the information pertaining to that
// channel within the openChannelBucket is deleted, and a compact summary is
// put in place instead.
type ChannelCloseSummary struct {
	// ChanPoint is the outpoint for this channel's funding transaction,
	// and is used as a unique identifier for the channel.
	ChanPoint wire.OutPoint

	// ShortChanID encodes the exact location in the chain in which the
	// channel was initially confirmed. This includes: the block height,
	// transaction index, and the output within the target transaction.
	ShortChanID lnwire.ShortChannelID

	// ChainHash is the hash of the genesis block that this channel resides
	// within.
	ChainHash chainhash.Hash

	// ClosingTXID is the txid of the transaction which ultimately closed
	// this channel.
	ClosingTXID chainhash.Hash

	// RemotePub is the public key of the remote peer that we formerly had
	// a channel with.
	RemotePub *btcec.PublicKey

	// Capacity was the total capacity of the channel.
	Capacity btcutil.Amount

	// CloseHeight is the height at which the funding transaction was
	// spent.
	CloseHeight uint32

	// SettledBalance is our total balance settled balance at the time of
	// channel closure. This _does not_ include the sum of any outputs that
	// have been time-locked as a result of the unilateral channel closure.
	SettledBalance btcutil.Amount

	// TimeLockedBalance is the sum of all the time-locked outputs at the
	// time of channel closure. If we triggered the force closure of this
	// channel, then this value will be non-zero if our settled output is
	// above the dust limit. If we were on the receiving side of a channel
	// force closure, then this value will be non-zero if we had any
	// outstanding outgoing HTLC's at the time of channel closure.
	TimeLockedBalance btcutil.Amount

	// CloseType details exactly _how_ the channel was closed. Five closure
	// types are possible: cooperative, local force, remote force, breach
	// and funding canceled.
	CloseType ClosureType

	// IsPending indicates whether this channel is in the 'pending close'
	// state, which means the channel closing transaction has been
	// confirmed, but not yet been fully resolved. In the case of a channel
	// that has been cooperatively closed, it will go straight into the
	// fully resolved state as soon as the closing transaction has been
	// confirmed. However, for channels that have been force closed, they'll
	// stay marked as "pending" until _all_ the pending funds have been
	// swept.
	IsPending bool

	// RemoteCurrentRevocation is the current revocation for their
	// commitment transaction. However, since this is the derived public key,
	// we don't yet have the private key so we aren't yet able to verify
	// that it's actually in the hash chain.
	RemoteCurrentRevocation *btcec.PublicKey

	// RemoteNextRevocation is the revocation key to be used for the *next*
	// commitment transaction we create for the local node. Within the
	// specification, this value is referred to as the
	// per-commitment-point.
	RemoteNextRevocation *btcec.PublicKey

	// LocalChanCfg is the channel configuration for the local node.
	LocalChanConfig ChannelConfig

	// LastChanSyncMsg is the ChannelReestablish message for this channel
	// for the state at the point where it was closed.
	LastChanSyncMsg *lnwire.ChannelReestablish
}

func serializeChannelCloseSummary(w io.Writer, cs *ChannelCloseSummary) error {
	err := WriteElements(w,
		cs.ChanPoint, cs.ShortChanID, cs.ChainHash, cs.ClosingTXID,
		cs.CloseHeight, cs.RemotePub, cs.Capacity, cs.SettledBalance,
		cs.TimeLockedBalance, cs.CloseType, cs.IsPending,
	)
	if err != nil {
		return err
	}

	// If this is a close channel summary created before the addition of
	// the new fields, then we can exit here.
	if cs.RemoteCurrentRevocation == nil {
		return WriteElements(w, false)
	}

	// If fields are present, write boolean to indicate this, and continue.
	if err := WriteElements(w, true); err != nil {
		return err
	}

	if err := WriteElements(w, cs.RemoteCurrentRevocation); err != nil {
		return err
	}

	if err := writeChanConfig(w, &cs.LocalChanConfig); err != nil {
		return err
	}

	// The RemoteNextRevocation field is optional, as it's possible for a
	// channel to be closed before we learn of the next unrevoked
	// revocation point for the remote party. Write a boolen indicating
	// whether this field is present or not.
	if err := WriteElements(w, cs.RemoteNextRevocation != nil); err != nil {
		return err
	}

	// Write the field, if present.
	if cs.RemoteNextRevocation != nil {
		if err = WriteElements(w, cs.RemoteNextRevocation); err != nil {
			return err
		}
	}

	// Write whether the channel sync message is present.
	if err := WriteElements(w, cs.LastChanSyncMsg != nil); err != nil {
		return err
	}

	// Write the channel sync message, if present.
	if cs.LastChanSyncMsg != nil {
		if err := WriteElements(w, cs.LastChanSyncMsg); err != nil {
			return err
		}
	}

	return nil
}

func deserializeCloseChannelSummary(r io.Reader) (*ChannelCloseSummary, error) {
	c := &ChannelCloseSummary{}

	err := ReadElements(r,
		&c.ChanPoint, &c.ShortChanID, &c.ChainHash, &c.ClosingTXID,
		&c.CloseHeight, &c.RemotePub, &c.Capacity, &c.SettledBalance,
		&c.TimeLockedBalance, &c.CloseType, &c.IsPending,
	)
	if err != nil {
		return nil, err
	}

	// We'll now check to see if the channel close summary was encoded with
	// any of the additional optional fields.
	var hasNewFields bool
	err = ReadElements(r, &hasNewFields)
	if err != nil {
		return nil, err
	}

	// If fields are not present, we can return.
	if !hasNewFields {
		return c, nil
	}

	// Otherwise read the new fields.
	if err := ReadElements(r, &c.RemoteCurrentRevocation); err != nil {
		return nil, err
	}

	if err := readChanConfig(r, &c.LocalChanConfig); err != nil {
		return nil, err
	}

	// Finally, we'll attempt to read the next unrevoked commitment point
	// for the remote party. If we closed the channel before receiving a
	// funding locked message then this might not be present. A boolean
	// indicating whether the field is present will come first.
	var hasRemoteNextRevocation bool
	err = ReadElements(r, &hasRemoteNextRevocation)
	if err != nil {
		return nil, err
	}

	// If this field was written, read it.
	if hasRemoteNextRevocation {
		err = ReadElements(r, &c.RemoteNextRevocation)
		if err != nil {
			return nil, err
		}
	}

	// Check if we have a channel sync message to read.
	var hasChanSyncMsg bool
	err = ReadElements(r, &hasChanSyncMsg)
	if err == io.EOF {
		return c, nil
	} else if err != nil {
		return nil, err
	}

	// If a chan sync message is present, read it.
	if hasChanSyncMsg {
		// We must pass in reference to a lnwire.Message for the codec
		// to support it.
		var msg lnwire.Message
		if err := ReadElements(r, &msg); err != nil {
			return nil, err
		}

		chanSync, ok := msg.(*lnwire.ChannelReestablish)
		if !ok {
			return nil, errors.New("unable cast db Message to " +
				"ChannelReestablish")
		}
		c.LastChanSyncMsg = chanSync
	}

	return c, nil
}

func writeChanConfig(b io.Writer, c *ChannelConfig) error {
	return WriteElements(b,
		c.DustLimit, c.MaxPendingAmount, c.ChanReserve, c.MinHTLC,
		c.MaxAcceptedHtlcs, c.CsvDelay, c.MultiSigKey,
		c.RevocationBasePoint, c.PaymentBasePoint, c.DelayBasePoint,
		c.HtlcBasePoint,
	)
}

func readChanConfig(b io.Reader, c *ChannelConfig) error {
	return ReadElements(b,
		&c.DustLimit, &c.MaxPendingAmount, &c.ChanReserve,
		&c.MinHTLC, &c.MaxAcceptedHtlcs, &c.CsvDelay,
		&c.MultiSigKey, &c.RevocationBasePoint,
		&c.PaymentBasePoint, &c.DelayBasePoint,
		&c.HtlcBasePoint,
	)
}