package lnwire import ( "fmt" "io" "github.com/roasbeef/btcutil" ) // OnionPacketSize is the size of the serialized Sphinx onion packet included // in each UpdateAddHTLC message. const OnionPacketSize = 1254 // UpdateAddHTLC is the message sent by Alice to Bob when she wishes to add an // HTLC to his remote commitment transaction. In addition to information // detailing the value, the ID, expiry, and the onion blob is also included // which allows Bob to derive the next hop in the route. The HTLC added by this // message is to be added to the remote node's "pending" HTLC's. A subsequent // CommitSig message will move the pending HTLC to the newly created commitment // transaction, marking them as "staged". type UpdateAddHTLC struct { // ChanID is the particular active channel that this // UpdateAddHTLC is binded to. ChanID ChannelID // ID is the identification server for this HTLC. This value is // explicitly included as it allows nodes to survive single-sided // restarts. The ID value for this sides starts at zero, and increases // with each offered HTLC. ID uint64 // Expiry is the number of blocks after which this HTLC should expire. // It is the receiver's duty to ensure that the outgoing HTLC has a // sufficient expiry value to allow her to redeem the incoming HTLC. Expiry uint32 // Amount is the amount of satoshis this HTLC is worth. Amount btcutil.Amount // PaymentHash is the payment hash to be included in the HTLC this // request creates. The pre-image to this HTLC must be revelaed by the // upstream peer in order to fully settle the HTLC. PaymentHash [32]byte // OnionBlob is the raw serialized mix header used to route an HTLC in // a privacy-preserving manner. The mix header is defined currently to // be parsed as a 4-tuple: (groupElement, routingInfo, headerMAC, // body). First the receiving node should use the groupElement, and // its current onion key to derive a shared secret with the source. // Once the shared secret has been derived, the headerMAC should be // checked FIRST. Note that the MAC only covers the routingInfo field. // If the MAC matches, and the shared secret is fresh, then the node // should strip off a layer of encryption, exposing the next hop to be // used in the subsequent UpdateAddHTLC message. OnionBlob [OnionPacketSize]byte } // NewUpdateAddHTLC returns a new empty UpdateAddHTLC message. func NewUpdateAddHTLC() *UpdateAddHTLC { return &UpdateAddHTLC{} } // A compile time check to ensure UpdateAddHTLC implements the lnwire.Message // interface. var _ Message = (*UpdateAddHTLC)(nil) // Decode deserializes a serialized UpdateAddHTLC message stored in the passed // io.Reader observing the specified protocol version. // // This is part of the lnwire.Message interface. func (c *UpdateAddHTLC) Decode(r io.Reader, pver uint32) error { return readElements(r, &c.ChanID, &c.ID, &c.Expiry, &c.Amount, c.PaymentHash[:], c.OnionBlob[:], ) } // Encode serializes the target UpdateAddHTLC into the passed io.Writer observing // the protocol version specified. // // This is part of the lnwire.Message interface. func (c *UpdateAddHTLC) Encode(w io.Writer, pver uint32) error { return writeElements(w, c.ChanID, c.ID, c.Expiry, c.Amount, c.PaymentHash[:], c.OnionBlob[:], ) } // Command returns the integer uniquely identifying this message type on the // wire. // // This is part of the lnwire.Message interface. func (c *UpdateAddHTLC) Command() uint32 { return CmdUpdateAddHTLC } // MaxPayloadLength returns the maximum allowed payload size for a UpdateAddHTLC // complete message observing the specified protocol version. // // This is part of the lnwire.Message interface. func (c *UpdateAddHTLC) MaxPayloadLength(uint32) uint32 { // 1338 return 32 + 8 + 4 + 8 + 32 + 1254 } // Validate performs any necessary sanity checks to ensure all fields present // on the UpdateAddHTLC are valid. // // This is part of the lnwire.Message interface. func (c *UpdateAddHTLC) Validate() error { if c.Amount < 0 { // While fees can be negative, it's too confusing to allow // negative payments. Maybe for some wallets, but not this one! return fmt.Errorf("amount paid cannot be negative") } // We're good! return nil }