package channeldb import ( "bytes" "encoding/binary" "fmt" "io" "net" "sync" "github.com/boltdb/bolt" "github.com/lightningnetwork/lnd/lnwire" "github.com/lightningnetwork/lnd/shachain" "github.com/roasbeef/btcd/btcec" "github.com/roasbeef/btcd/chaincfg/chainhash" "github.com/roasbeef/btcd/wire" "github.com/roasbeef/btcutil" ) 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") // chanInfoKey can be accessed within the bucket for a channel // (identified by it's chanPoint). This key stores all the static // information for a channel which is decided at the end of the // funding flow. chanInfoKey = []byte("chan-info-key") // chanCommitmentKey can be accessed within the sub-bucket for a // particular channel. This key stores the up to date commitment state // for a particular channel party. Appending a 0 to the end of this key // indicates it's the commitment for the local party, and appending a 1 // to the end of this key indicates it's the commitment for the remote // party. chanCommitmentKey = []byte("chan-commitment-key") // revocationStateKey stores their current revocation hash, our // preimage producer and their preimage store. revocationStateKey = []byte("revocation-state-key") // commitDiffKey stores the current pending commitment state we've // extended to the remote party (if any). Each time we propose a new // state, we store the information necessary to reconstruct this state // from the prior commitment. This allows us to resync the remote party // to their expected state in the case of message loss. // // TODO(roasbeef): rename to commit chain? commitDiffKey = []byte("commit-diff-key") // revocationLogBucket is dedicated for storing the necessary delta // state between channel updates required to re-construct a past state // in order to punish a counterparty attempting a non-cooperative // channel closure. This key should be accessed from within the // sub-bucket of a target channel, identified by its channel point. revocationLogBucket = []byte("revocation-log-key") ) var ( // ErrNoCommitmentsFound is returned when a channel has not set // commitment states. ErrNoCommitmentsFound = fmt.Errorf("no commitments found") // ErrNoChanInfoFound is returned when a particular channel does not // have any channels state. ErrNoChanInfoFound = fmt.Errorf("no chan info found") // ErrNoRevocationsFound is returned when revocation state for a // particular channel cannot be found. ErrNoRevocationsFound = fmt.Errorf("no revocations found") // ErrNoPendingCommit is returned when there is not a pending // commitment for a remote party. A new commitment is written to disk // each time we write a new state in order to be properly fault // tolerant. ErrNoPendingCommit = fmt.Errorf("no pending commits found") ) // 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 = 0 // DualFunder represents a channel wherein both parties contribute // funds towards the total capacity of the channel. The channel may be // funded symmetrically or asymmetrically. DualFunder = 1 ) // ChannelConstraints represents a set of constraints meant to allow a node to // limit their exposure, enact flow control and ensure that all HTLC's 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 is static for the duration of the channel, meaning the channel // must be teared 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 // MaxPendingAmount is the maximum pending HTLC value that can be // present within the channel at a particular time. This value is set // by the initiator of the channel and must be upheld at all times. MaxPendingAmount lnwire.MilliSatoshi // ChanReserve is an absolute reservation on the channel for this // particular node. 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 // MinHTLC is the minimum HTLC accepted for a direction of the channel. // If any HTLC's 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 amount of HTLC's that are to be // accepted by the owner of this set of constraints. This allows each // node to limit their over all exposure to HTLC's that may need to be // acted upon in the case of a unilateral channel closure or a contract // breach. MaxAcceptedHtlcs 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 // 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 // MultiSigKey is the key to be used within the 2-of-2 output script // for the owner of this channel config. MultiSigKey *btcec.PublicKey // 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 *btcec.PublicKey // PaymentBasePoint is the based 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 *btcec.PublicKey // DelayBasePoint is the based 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 *btcec.PublicKey } // 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. 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 thru } // 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 identities the channel within the // target blockchain as specified by the chain hash parameter. FundingOutpoint 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 // 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 // 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 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 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 // TODO(roasbeef): eww Db *DB // TODO(roasbeef): just need to store local and remote HTLC's? sync.RWMutex } // FullSync serializes, and writes to disk the *full* channel state, using // both the active channel bucket to store the prefixed column fields, and the // remote node's ID to store the remainder of the channel state. func (c *OpenChannel) FullSync() error { c.Lock() defer c.Unlock() return c.Db.Update(c.fullSync) } // updateChanBucket is a helper function that returns a writeable bucket that a // channel's data resides in given: the public key for the node, the outpoint, // and the chainhash that the channel resides on. func updateChanBucket(tx *bolt.Tx, nodeKey *btcec.PublicKey, outPoint *wire.OutPoint, chainHash chainhash.Hash) (*bolt.Bucket, error) { // First fetch the top level bucket which stores all data related to // current, active channels. openChanBucket, err := tx.CreateBucketIfNotExists(openChannelBucket) if err != nil { return nil, err } // Within this top level bucket, fetch the bucket dedicated to storing // open channel data specific to the remote node. nodePub := nodeKey.SerializeCompressed() nodeChanBucket, err := openChanBucket.CreateBucketIfNotExists(nodePub) if err != nil { return nil, err } // We'll then recurse down an additional layer in order to fetch the // bucket for this particular chain. chainBucket, err := nodeChanBucket.CreateBucketIfNotExists(chainHash[:]) if err != nil { return nil, err } // With the bucket for the node fetched, we can now go down another // level, creating the bucket (if it doesn't exist), for this channel // itself. var chanPointBuf bytes.Buffer chanPointBuf.Grow(outPointSize) if err := writeOutpoint(&chanPointBuf, outPoint); err != nil { return nil, err } chanBucket, err := chainBucket.CreateBucketIfNotExists( chanPointBuf.Bytes(), ) if err != nil { return nil, err } return chanBucket, nil } // readChanBucket is a helper function that returns a readable bucket that a // channel's data resides in given: the public key for the node, the outpoint, // and the chainhash that the channel resides on. func readChanBucket(tx *bolt.Tx, nodeKey *btcec.PublicKey, outPoint *wire.OutPoint, chainHash chainhash.Hash) (*bolt.Bucket, error) { // First fetch the top level bucket which stores all data related to // current, active channels. openChanBucket := tx.Bucket(openChannelBucket) if openChanBucket == nil { return nil, ErrNoChanDBExists } // Within this top level bucket, fetch the bucket dedicated to storing // open channel data specific to the remote node. nodePub := nodeKey.SerializeCompressed() nodeChanBucket := openChanBucket.Bucket(nodePub) if nodeChanBucket == nil { return nil, ErrNoActiveChannels } // We'll then recurse down an additional layer in order to fetch the // bucket for this particular chain. chainBucket := nodeChanBucket.Bucket(chainHash[:]) if chainBucket == nil { return nil, ErrNoActiveChannels } // With the bucket for the node fetched, we can now go down another // level, for this channel iteslf. var chanPointBuf bytes.Buffer chanPointBuf.Grow(outPointSize) if err := writeOutpoint(&chanPointBuf, outPoint); err != nil { return nil, err } chanBucket := chainBucket.Bucket(chanPointBuf.Bytes()) if chanBucket == nil { return nil, ErrNoActiveChannels } return chanBucket, nil } // fullSync is an internal version of the FullSync method which allows callers // to sync the contents of an OpenChannel while re-using an existing database // transaction. func (c *OpenChannel) fullSync(tx *bolt.Tx) error { chanBucket, err := updateChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } return putOpenChannel(chanBucket, c) } // MarkAsOpen marks a channel as fully open given a locator that uniquely // describes its location within the chain. func (c *OpenChannel) MarkAsOpen(openLoc lnwire.ShortChannelID) error { c.Lock() defer c.Unlock() return c.Db.Update(func(tx *bolt.Tx) error { chanBucket, err := updateChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } channel, err := fetchOpenChannel(chanBucket, &c.FundingOutpoint) if err != nil { return err } channel.IsPending = false channel.ShortChanID = openLoc return putOpenChannel(chanBucket, channel) }) } // putChannel serializes, and stores the current state of the channel in its // entirety. func putOpenChannel(chanBucket *bolt.Bucket, channel *OpenChannel) error { // First, we'll write out all the relatively static fields, that are // decided upon initial channel creation. if err := putChanInfo(chanBucket, channel); err != nil { return fmt.Errorf("unable to store chan info: %v", err) } // With the static channel info written out, we'll now write out the // current commitment state for both parties. if err := putChanCommitments(chanBucket, channel); err != nil { return fmt.Errorf("unable to store chan commitments: %v", err) } // Finally, we'll write out the revocation state for both parties // within a distinct key space. if err := putChanRevocationState(chanBucket, channel); err != nil { return fmt.Errorf("unable to store chan revocations: %v", err) } return nil } // fetchOpenChannel retrieves, and deserializes (including decrypting // sensitive) the complete channel currently active with the passed nodeID. func fetchOpenChannel(chanBucket *bolt.Bucket, chanPoint *wire.OutPoint) (*OpenChannel, error) { channel := &OpenChannel{ FundingOutpoint: *chanPoint, } // First, we'll read all the static information that changes less // frequently from disk. if err := fetchChanInfo(chanBucket, channel); err != nil { return nil, fmt.Errorf("unable to fetch chan info: %v", err) } // With the static information read, we'll now read the current // commitment state for both sides of the channel. if err := fetchChanCommitments(chanBucket, channel); err != nil { return nil, fmt.Errorf("unable to fetch chan commitments: %v", err) } // Finally, we'll retrieve the current revocation state so we can // properly if err := fetchChanRevocationState(chanBucket, channel); err != nil { return nil, fmt.Errorf("unable to fetch chan revocations: %v", err) } return channel, nil } // SyncPending writes the contents of the channel to the database while it's in // the pending (waiting for funding confirmation) state. The IsPending flag // will be set to true. When the channel's funding transaction is confirmed, // the channel should be marked as "open" and the IsPending flag set to false. // Note that this function also creates a LinkNode relationship between this // newly created channel and a new LinkNode instance. This allows listing all // channels in the database globally, or according to the LinkNode they were // created with. // // TODO(roasbeef): addr param should eventually be a lnwire.NetAddress type // that includes service bits. func (c *OpenChannel) SyncPending(addr *net.TCPAddr, pendingHeight uint32) error { c.Lock() defer c.Unlock() c.FundingBroadcastHeight = pendingHeight return c.Db.Update(func(tx *bolt.Tx) error { // First, sync all the persistent channel state to disk. if err := c.fullSync(tx); err != nil { return err } nodeInfoBucket, err := tx.CreateBucketIfNotExists(nodeInfoBucket) if err != nil { return err } // If a LinkNode for this identity public key already exists, // then we can exit early. nodePub := c.IdentityPub.SerializeCompressed() if nodeInfoBucket.Get(nodePub) != nil { return nil } // Next, we need to establish a (possibly) new LinkNode // relationship for this channel. The LinkNode metadata // contains reachability, up-time, and service bits related // information. linkNode := c.Db.NewLinkNode(wire.MainNet, c.IdentityPub, addr) // TODO(roasbeef): do away with link node all together? return putLinkNode(nodeInfoBucket, linkNode) }) } // UpdateCommitment updates the commitment state for the specified party // (remote or local). The commitment stat completely describes the balance // state at this point in the commitment chain. This method its to be called on // two occasions: when we revoke our prior commitment state, and when the // remote party revokes their prior commitment state. func (c *OpenChannel) UpdateCommitment(newCommitment *ChannelCommitment) error { c.Lock() defer c.Unlock() err := c.Db.Update(func(tx *bolt.Tx) error { chanBucket, err := updateChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } if err = putChanInfo(chanBucket, c); err != nil { return fmt.Errorf("unable to store chan info: %v", err) } // With the proper bucket fetched, we'll now write toe latest // commitment state to dis for the target party. err = putChanCommitment(chanBucket, newCommitment, true) if err != nil { return fmt.Errorf("unable to store chan "+ "revocations: %v", err) } return nil }) if err != nil { return err } c.LocalCommitment = *newCommitment return nil } // 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 this HTLC. This differs // from the HtlcIndex as this will be incremented for each new log // update added. LogIndex uint64 } func serializeHtlcs(b io.Writer, htlcs []HTLC) error { numHtlcs := uint16(len(htlcs)) if err := writeElement(b, numHtlcs); err != nil { return err } for _, htlc := range htlcs { if err := writeElements(b, htlc.Signature, htlc.RHash, htlc.Amt, htlc.RefundTimeout, htlc.OutputIndex, htlc.Incoming, htlc.OnionBlob[:], htlc.HtlcIndex, htlc.LogIndex, ); err != nil { return err } } return nil } func deserializeHtlcs(r io.Reader) ([]HTLC, error) { var numHtlcs uint16 if err := readElement(r, &numHtlcs); err != nil { return nil, err } var htlcs []HTLC if numHtlcs == 0 { return htlcs, nil } htlcs = make([]HTLC, numHtlcs) for i := uint16(0); i < numHtlcs; i++ { if err := readElements(r, &htlcs[i].Signature, &htlcs[i].RHash, &htlcs[i].Amt, &htlcs[i].RefundTimeout, &htlcs[i].OutputIndex, &htlcs[i].Incoming, &htlcs[i].OnionBlob, &htlcs[i].HtlcIndex, &htlcs[i].LogIndex, ); err != nil { return htlcs, err } } return htlcs, nil } // Copy returns a full copy of the target HTLC. func (h *HTLC) Copy() HTLC { clone := HTLC{ Incoming: h.Incoming, Amt: h.Amt, RefundTimeout: h.RefundTimeout, OutputIndex: h.OutputIndex, } copy(clone.Signature[:], h.Signature) copy(clone.RHash[:], h.RHash[:]) return clone } // LogUpdate represents a pending update to the remote commitment chain. The // log update may be an add, fail, or settle entry. We maintain this data in // order to be able to properly retransmit our proposed // state if necessary. type LogUpdate struct { // LogIndex is the log index of this proposed commitment update entry. LogIndex uint64 // UpdateMsg is the update message that was included within the our // local update log. The LogIndex value denotes the log index of this // update which will be used when restoring our local update log if // we're left with a dangling update on restart. UpdateMsg lnwire.Message } // CommitDiff represents the delta needed to apply the state transition between // two subsequent commitment states. Given state N and state N+1, one is able // to apply the set of messages contained within the CommitDiff to N to arrive // at state N+1. Each time a new commitment is extended, we'll write a new // commitment (along with the full commitment state) to disk so we can // re-transmit the state in the case of a connection loss or message drop. type CommitDiff struct { // ChannelCommitment is the full commitment state that one would arrive // at by applying the set of messages contained in the UpdateDiff to // the prior accepted commitment. Commitment ChannelCommitment // LogUpdates is the set of messages sent prior to the commitment state // transition in question. Upon reconnection, if we detect that they // don't have the commitment, then we re-send this along with the // proper signature. LogUpdates []LogUpdate // CommitSig is the exact CommitSig message that should be sent after // the set of LogUpdates above has been retransmitted. The signatures // within this message should properly cover the new commitment state // and also the HTLC's within the new commitment state. CommitSig *lnwire.CommitSig } func serializeCommitDiff(w io.Writer, diff *CommitDiff) error { if err := serializeChanCommit(w, &diff.Commitment); err != nil { return err } if err := diff.CommitSig.Encode(w, 0); err != nil { return err } numUpdates := uint16(len(diff.LogUpdates)) if err := binary.Write(w, byteOrder, numUpdates); err != nil { return err } for _, diff := range diff.LogUpdates { err := writeElements(w, diff.LogIndex, diff.UpdateMsg) if err != nil { return err } } return nil } func deserializeCommitDiff(r io.Reader) (*CommitDiff, error) { var ( d CommitDiff err error ) d.Commitment, err = deserializeChanCommit(r) if err != nil { return nil, err } d.CommitSig = &lnwire.CommitSig{} if err := d.CommitSig.Decode(r, 0); err != nil { return nil, err } var numUpdates uint16 if err := binary.Read(r, byteOrder, &numUpdates); err != nil { return nil, err } d.LogUpdates = make([]LogUpdate, numUpdates) for i := 0; i < int(numUpdates); i++ { err := readElements(r, &d.LogUpdates[i].LogIndex, &d.LogUpdates[i].UpdateMsg, ) if err != nil { return nil, err } } return &d, nil } // AppendRemoteCommitChain appends a new CommitDiff to the end of the // commitment chain for the remote party. This method is to be used once we // have prepared a new commitment state for the remote party, but before we // transmit it to the remote party. The contents of the argument should be // sufficient to retransmit the updates and signature needed to reconstruct the // state in full, in the case that we need to retransmit. func (c *OpenChannel) AppendRemoteCommitChain(diff *CommitDiff) error { c.Lock() defer c.Unlock() return c.Db.Update(func(tx *bolt.Tx) error { // First, we'll grab the writeable bucket where this channel's // data resides. chanBucket, err := updateChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } // TODO(roasbeef): use seqno to derive key for later LCP // With the bucket retrieved, we'll now serialize the commit // diff itself, and write it to disk. var b bytes.Buffer if err := serializeCommitDiff(&b, diff); err != nil { return err } return chanBucket.Put(commitDiffKey, b.Bytes()) }) } // RemoteCommitChainTip returns the "tip" of the current remote commitment // chain. This value will be non-nil iff, we've created a new commitment for // the remote party that they haven't yet ACK'd. In this case, their commitment // chain will have a length of two: their current unrevoked commitment, and // this new pending commitment. Once they revoked their prior state, we'll swap // these pointers, causing the tip and the tail to point to the same entry. func (c *OpenChannel) RemoteCommitChainTip() (*CommitDiff, error) { var cd *CommitDiff err := c.Db.View(func(tx *bolt.Tx) error { chanBucket, err := readChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } tipBytes := chanBucket.Get(commitDiffKey) if tipBytes == nil { return ErrNoPendingCommit } tipReader := bytes.NewReader(tipBytes) dcd, err := deserializeCommitDiff(tipReader) if err != nil { return err } cd = dcd return nil }) if err != nil { return nil, err } return cd, err } // InsertNextRevocation inserts the _next_ commitment point (revocation) into // the database, and also modifies the internal RemoteNextRevocation attribute // to point to the passed key. This method is to be using during final channel // set up, _after_ the channel has been fully confirmed. // // NOTE: If this method isn't called, then the target channel won't be able to // propose new states for the commitment state of the remote party. func (c *OpenChannel) InsertNextRevocation(revKey *btcec.PublicKey) error { c.Lock() defer c.Unlock() c.RemoteNextRevocation = revKey err := c.Db.Update(func(tx *bolt.Tx) error { chanBucket, err := updateChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } return putChanRevocationState(chanBucket, c) }) if err != nil { return err } return nil } // AdvanceCommitChainTail records the new state transition within an on-disk // append-only log which records all state transitions by the remote peer. In // the case of an uncooperative broadcast of a prior state by the remote peer, // this log can be consulted in order to reconstruct the state needed to // rectify the situation. This method will add the current commitment for the // remote party to the revocation log, and promote the current pending // commitment to the current remove commitment. func (c *OpenChannel) AdvanceCommitChainTail() error { c.Lock() defer c.Unlock() var newRemoteCommit *ChannelCommitment err := c.Db.Update(func(tx *bolt.Tx) error { chanBucket, err := readChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } // Persist the latest preimage state to disk as the remote peer // has just added to our local preimage store, and given us a // new pending revocation key. if err := putChanRevocationState(chanBucket, c); err != nil { return err } // With the current preimage producer/store state updated, // append a new log entry recording this the delta of this // state transition. // // TODO(roasbeef): could make the deltas relative, would save // space, but then tradeoff for more disk-seeks to recover the // full state. logKey := revocationLogBucket logBucket, err := chanBucket.CreateBucketIfNotExists(logKey) if err != nil { return err } // Before we append this revoked state to the revocation log, // we'll swap out what's currently the tail of the commit tip, // with the current locked-in commitment for the remote party. tipBytes := chanBucket.Get(commitDiffKey) tipReader := bytes.NewReader(tipBytes) newCommit, err := deserializeCommitDiff(tipReader) if err != nil { return err } err = putChanCommitment(chanBucket, &newCommit.Commitment, false) if err != nil { return err } if err := chanBucket.Delete(commitDiffKey); err != nil { return err } // With the commitment pointer swapped, we can now add the // revoked (prior) state to the revocation log. // // TODO(roasbeef): store less err = appendChannelLogEntry(logBucket, &c.RemoteCommitment) if err != nil { return err } newRemoteCommit = &newCommit.Commitment return nil }) if err != nil { return err } // With the db transaction complete, we'll swap over the in-memory // pointer of the new remote commitment, which was previously the tip // of the commit chain. c.RemoteCommitment = *newRemoteCommit return nil } // RevocationLogTail returns the "tail", or the end of the current revocation // log. This entry represents the last previous state for the remote node's // commitment chain. The ChannelDelta returned by this method will always lag // one state behind the most current (unrevoked) state of the remote node's // commitment chain. func (c *OpenChannel) RevocationLogTail() (*ChannelCommitment, error) { c.RLock() defer c.RUnlock() // If we haven't created any state updates yet, then we'll exit erly as // there's nothing to be found on disk in the revocation bucket. if c.RemoteCommitment.CommitHeight == 0 { return nil, nil } var commit ChannelCommitment if err := c.Db.View(func(tx *bolt.Tx) error { chanBucket, err := readChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } logBucket := chanBucket.Bucket(revocationLogBucket) if logBucket == nil { return ErrNoPastDeltas } // Once we have the bucket that stores the revocation log from // this channel, we'll jump to the _last_ key in bucket. As we // store the update number on disk in a big-endian format, // this'll retrieve the latest entry. cursor := logBucket.Cursor() _, tailLogEntry := cursor.Last() logEntryReader := bytes.NewReader(tailLogEntry) // Once we have the entry, we'll decode it into the channel // delta pointer we created above. var dbErr error commit, dbErr = deserializeChanCommit(logEntryReader) if dbErr != nil { return dbErr } return nil }); err != nil { return nil, err } return &commit, nil } // CommitmentHeight returns the current commitment height. The commitment // height represents the number of updates to the commitment state to data. // This value is always monotonically increasing. This method is provided in // order to allow multiple instances of a particular open channel to obtain a // consistent view of the number of channel updates to data. func (c *OpenChannel) CommitmentHeight() (uint64, error) { c.RLock() defer c.RUnlock() var height uint64 err := c.Db.View(func(tx *bolt.Tx) error { // Get the bucket dedicated to storing the metadata for open // channels. chanBucket, err := readChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } commit, err := fetchChanCommitment(chanBucket, true) if err != nil { return err } height = commit.CommitHeight return nil }) if err != nil { return 0, nil } return height, nil } // FindPreviousState scans through the append-only log in an attempt to recover // the previous channel state indicated by the update number. This method is // intended to be used for obtaining the relevant data needed to claim all // funds rightfully spendable in the case of an on-chain broadcast of the // commitment transaction. func (c *OpenChannel) FindPreviousState(updateNum uint64) (*ChannelCommitment, error) { c.RLock() defer c.RUnlock() var commit ChannelCommitment err := c.Db.View(func(tx *bolt.Tx) error { chanBucket, err := readChanBucket(tx, c.IdentityPub, &c.FundingOutpoint, c.ChainHash) if err != nil { return err } logBucket := chanBucket.Bucket(revocationLogBucket) if logBucket == nil { return ErrNoPastDeltas } c, err := fetchChannelLogEntry(logBucket, updateNum) if err != nil { return err } commit = c return nil }) if err != nil { return nil, err } return &commit, nil } // ClosureType is an enum like structure that details exactly _how_ a channel // was closed. Three closure types are currently possible: cooperative, force, // and breach. type ClosureType uint8 const ( // CooperativeClose indicates that a channel has been closed // cooperatively. This means that both channel peers were online and // signed a new transaction paying out the settled balance of the // contract. CooperativeClose ClosureType = iota // ForceClose indicates that one peer unilaterally broadcast their // current commitment state on-chain. ForceClose // BreachClose indicates that one peer attempted to broadcast a prior // _revoked_ channel state. BreachClose // FundingCanceled indicates that the channel never was fully opened // before it was marked as closed in the database. This can happen if // we or the remote fail at some point during the opening workflow, or // we timeout waiting for the funding transaction to be confirmed. FundingCanceled ) // 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 // 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 // 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. Three // closure types are possible: cooperative, force, and breach. CloseType ClosureType // IsPending indicates whether this channel is in the 'pending close' // state, which means the channel closing transaction has been // broadcast, but not confirmed yet or has not yet been fully resolved. // In the case of a channel that has been cooperatively closed, it will // no longer be considered pending as soon as the closing transaction // has been confirmed. However, for channel that have been force // closed, they'll stay marked as "pending" until _all_ the pending // funds have been swept. IsPending bool // TODO(roasbeef): also store short_chan_id? } // CloseChannel closes a previously active Lightning channel. Closing a channel // entails deleting all saved state within the database concerning this // channel. This method also takes a struct that summarizes the state of the // channel at closing, this compact representation will be the only component // of a channel left over after a full closing. func (c *OpenChannel) CloseChannel(summary *ChannelCloseSummary) error { c.Lock() defer c.Unlock() return c.Db.Update(func(tx *bolt.Tx) error { openChanBucket := tx.Bucket(openChannelBucket) if openChanBucket == nil { return ErrNoChanDBExists } nodePub := c.IdentityPub.SerializeCompressed() nodeChanBucket := openChanBucket.Bucket(nodePub) if nodeChanBucket == nil { return ErrNoActiveChannels } chainBucket := nodeChanBucket.Bucket(c.ChainHash[:]) if chainBucket == nil { return ErrNoActiveChannels } var chanPointBuf bytes.Buffer chanPointBuf.Grow(outPointSize) err := writeOutpoint(&chanPointBuf, &c.FundingOutpoint) if err != nil { return err } chanBucket := chainBucket.Bucket(chanPointBuf.Bytes()) if chanBucket == nil { return ErrNoActiveChannels } // Now that the index to this channel has been deleted, purge // the remaining channel metadata from the database. err = deleteOpenChannel(chanBucket, chanPointBuf.Bytes()) if err != nil { return err } // With the base channel data deleted, attempt to delete the // information stored within the revocation log. logBucket := chanBucket.Bucket(revocationLogBucket) if logBucket != nil { err := wipeChannelLogEntries(logBucket) if err != nil { return err } err = chanBucket.DeleteBucket(revocationLogBucket) if err != nil { return err } } err = chainBucket.DeleteBucket(chanPointBuf.Bytes()) if err != nil { return err } // Finally, create a summary of this channel in the closed // channel bucket for this node. return putChannelCloseSummary(tx, chanPointBuf.Bytes(), summary) }) } // ChannelSnapshot is a frozen snapshot of the current channel state. A // snapshot is detached from the original channel that generated it, providing // read-only access to the current or prior state of an active channel. // // TODO(roasbeef): remove all together? pretty much just commitment type ChannelSnapshot struct { // RemoteIdentity is the identity public key of the remote node that we // are maintaining the open channel with. RemoteIdentity btcec.PublicKey // ChanPoint is the outpoint that created the channel. This output is // found within the funding transaction and uniquely identified the // channel on the resident chain. ChannelPoint wire.OutPoint // ChainHash is the genesis hash of the chain that the channel resides // within. ChainHash chainhash.Hash // Capacity is the total capacity of the 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 // ChannelCommitment is the current up-to-date commitment for the // target channel. ChannelCommitment } // Snapshot returns a read-only snapshot of the current channel state. This // snapshot includes information concerning the current settled balance within // the channel, metadata detailing total flows, and any outstanding HTLCs. func (c *OpenChannel) Snapshot() *ChannelSnapshot { c.RLock() defer c.RUnlock() localCommit := c.LocalCommitment snapshot := &ChannelSnapshot{ RemoteIdentity: *c.IdentityPub, ChannelPoint: c.FundingOutpoint, Capacity: c.Capacity, TotalMSatSent: c.TotalMSatSent, TotalMSatReceived: c.TotalMSatReceived, ChainHash: c.ChainHash, ChannelCommitment: ChannelCommitment{ LocalBalance: localCommit.LocalBalance, RemoteBalance: localCommit.RemoteBalance, CommitHeight: localCommit.CommitHeight, CommitFee: localCommit.CommitFee, }, } // Copy over the current set of HTLCs to ensure the caller can't mutate // our internal state. snapshot.Htlcs = make([]HTLC, len(localCommit.Htlcs)) for i, h := range localCommit.Htlcs { snapshot.Htlcs[i] = h.Copy() } return snapshot } func putChannelCloseSummary(tx *bolt.Tx, chanID []byte, summary *ChannelCloseSummary) error { closedChanBucket, err := tx.CreateBucketIfNotExists(closedChannelBucket) if err != nil { return err } var b bytes.Buffer if err := serializeChannelCloseSummary(&b, summary); err != nil { return err } return closedChanBucket.Put(chanID, b.Bytes()) } func serializeChannelCloseSummary(w io.Writer, cs *ChannelCloseSummary) error { return writeElements(w, cs.ChanPoint, cs.ChainHash, cs.ClosingTXID, cs.RemotePub, cs.Capacity, cs.SettledBalance, cs.TimeLockedBalance, cs.CloseType, cs.IsPending, ) } func fetchChannelCloseSummary(tx *bolt.Tx, chanID []byte) (*ChannelCloseSummary, error) { closedChanBucket, err := tx.CreateBucketIfNotExists(closedChannelBucket) if err != nil { return nil, err } summaryBytes := closedChanBucket.Get(chanID) if summaryBytes == nil { return nil, fmt.Errorf("closed channel summary not found") } summaryReader := bytes.NewReader(summaryBytes) return deserializeCloseChannelSummary(summaryReader) } func deserializeCloseChannelSummary(r io.Reader) (*ChannelCloseSummary, error) { c := &ChannelCloseSummary{} err := readElements(r, &c.ChanPoint, &c.ChainHash, &c.ClosingTXID, &c.RemotePub, &c.Capacity, &c.SettledBalance, &c.TimeLockedBalance, &c.CloseType, &c.IsPending, ) if err != nil { return nil, err } return c, nil } func putChanInfo(chanBucket *bolt.Bucket, channel *OpenChannel) error { var w bytes.Buffer if err := writeElements(&w, channel.ChanType, channel.ChainHash, channel.FundingOutpoint, channel.ShortChanID, channel.IsPending, channel.IsInitiator, channel.FundingBroadcastHeight, channel.NumConfsRequired, channel.IdentityPub, channel.Capacity, channel.TotalMSatSent, channel.TotalMSatReceived, ); err != nil { return err } writeChanConfig := func(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, ) } if err := writeChanConfig(&w, &channel.LocalChanCfg); err != nil { return err } if err := writeChanConfig(&w, &channel.RemoteChanCfg); err != nil { return err } return chanBucket.Put(chanInfoKey, w.Bytes()) } func serializeChanCommit(w io.Writer, c *ChannelCommitment) error { if err := writeElements(w, c.CommitHeight, c.LocalLogIndex, c.LocalHtlcIndex, c.RemoteLogIndex, c.RemoteHtlcIndex, c.LocalBalance, c.RemoteBalance, c.CommitFee, c.FeePerKw, c.CommitTx, c.CommitSig, ); err != nil { return err } return serializeHtlcs(w, c.Htlcs) } func putChanCommitment(chanBucket *bolt.Bucket, c *ChannelCommitment, local bool) error { var commitKey []byte if local { commitKey = append(chanCommitmentKey, byte(0x00)) } else { commitKey = append(chanCommitmentKey, byte(0x01)) } var b bytes.Buffer if err := serializeChanCommit(&b, c); err != nil { return err } return chanBucket.Put(commitKey, b.Bytes()) } func putChanCommitments(chanBucket *bolt.Bucket, channel *OpenChannel) error { err := putChanCommitment(chanBucket, &channel.LocalCommitment, true) if err != nil { return err } return putChanCommitment(chanBucket, &channel.RemoteCommitment, false) } func putChanRevocationState(chanBucket *bolt.Bucket, channel *OpenChannel) error { var b bytes.Buffer err := writeElements( &b, channel.RemoteCurrentRevocation, channel.RevocationProducer, channel.RevocationStore, ) if err != nil { return err } // TODO(roasbeef): don't keep producer on disk // If the next revocation is present, which is only the case after the // FundingLocked message has been sent, then we'll write it to disk. if channel.RemoteNextRevocation != nil { err = writeElements(&b, channel.RemoteNextRevocation) if err != nil { return err } } return chanBucket.Put(revocationStateKey, b.Bytes()) } func fetchChanInfo(chanBucket *bolt.Bucket, channel *OpenChannel) error { infoBytes := chanBucket.Get(chanInfoKey) if infoBytes == nil { return ErrNoChanInfoFound } r := bytes.NewReader(infoBytes) if err := readElements(r, &channel.ChanType, &channel.ChainHash, &channel.FundingOutpoint, &channel.ShortChanID, &channel.IsPending, &channel.IsInitiator, &channel.FundingBroadcastHeight, &channel.NumConfsRequired, &channel.IdentityPub, &channel.Capacity, &channel.TotalMSatSent, &channel.TotalMSatReceived, ); err != nil { return err } readChanConfig := func(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, ) } if err := readChanConfig(r, &channel.LocalChanCfg); err != nil { return err } if err := readChanConfig(r, &channel.RemoteChanCfg); err != nil { return err } return nil } func deserializeChanCommit(r io.Reader) (ChannelCommitment, error) { var c ChannelCommitment err := readElements(r, &c.CommitHeight, &c.LocalLogIndex, &c.LocalHtlcIndex, &c.RemoteLogIndex, &c.RemoteHtlcIndex, &c.LocalBalance, &c.RemoteBalance, &c.CommitFee, &c.FeePerKw, &c.CommitTx, &c.CommitSig, ) if err != nil { return c, err } c.Htlcs, err = deserializeHtlcs(r) if err != nil { return c, err } return c, nil } func fetchChanCommitment(chanBucket *bolt.Bucket, local bool) (ChannelCommitment, error) { var commitKey []byte if local { commitKey = append(chanCommitmentKey, byte(0x00)) } else { commitKey = append(chanCommitmentKey, byte(0x01)) } commitBytes := chanBucket.Get(commitKey) if commitBytes == nil { return ChannelCommitment{}, ErrNoCommitmentsFound } r := bytes.NewReader(commitBytes) return deserializeChanCommit(r) } func fetchChanCommitments(chanBucket *bolt.Bucket, channel *OpenChannel) error { var err error channel.LocalCommitment, err = fetchChanCommitment(chanBucket, true) if err != nil { return err } channel.RemoteCommitment, err = fetchChanCommitment(chanBucket, false) if err != nil { return err } return nil } func fetchChanRevocationState(chanBucket *bolt.Bucket, channel *OpenChannel) error { revBytes := chanBucket.Get(revocationStateKey) if revBytes == nil { return ErrNoRevocationsFound } r := bytes.NewReader(revBytes) err := readElements( r, &channel.RemoteCurrentRevocation, &channel.RevocationProducer, &channel.RevocationStore, ) if err != nil { return err } // If there aren't any bytes left in the buffer, then we don't yet have // the next remote revocation, so we can exit early here. if r.Len() == 0 { return nil } // Otherwise we'll read the next revocation for the remote party which // is always the last item within the buffer. return readElements(r, &channel.RemoteNextRevocation) } func deleteOpenChannel(chanBucket *bolt.Bucket, chanPointBytes []byte) error { if err := chanBucket.Delete(chanInfoKey); err != nil { return err } err := chanBucket.Delete(append(chanCommitmentKey, byte(0x00))) if err != nil { return err } err = chanBucket.Delete(append(chanCommitmentKey, byte(0x01))) if err != nil { return err } if err := chanBucket.Delete(revocationStateKey); err != nil { return err } if diff := chanBucket.Get(commitDiffKey); diff != nil { return chanBucket.Delete(commitDiffKey) } return nil } func makeLogKey(updateNum uint64) [8]byte { var key [8]byte byteOrder.PutUint64(key[:], updateNum) return key } func appendChannelLogEntry(log *bolt.Bucket, commit *ChannelCommitment) error { var b bytes.Buffer if err := serializeChanCommit(&b, commit); err != nil { return err } logEntrykey := makeLogKey(commit.CommitHeight) return log.Put(logEntrykey[:], b.Bytes()) } func fetchChannelLogEntry(log *bolt.Bucket, updateNum uint64) (ChannelCommitment, error) { logEntrykey := makeLogKey(updateNum) commitBytes := log.Get(logEntrykey[:]) if commitBytes == nil { return ChannelCommitment{}, fmt.Errorf("log entry not found") } commitReader := bytes.NewReader(commitBytes) return deserializeChanCommit(commitReader) } func wipeChannelLogEntries(log *bolt.Bucket) error { // TODO(roasbeef): comment logCursor := log.Cursor() for k, _ := logCursor.First(); k != nil; k, _ = logCursor.Next() { if err := logCursor.Delete(); err != nil { return err } } return nil }