lnd.xprv/lnwire/update_add_htlc.go

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package lnwire
import (
"fmt"
"io"
"github.com/roasbeef/btcd/wire"
"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 {
// ChannelPoint is the particular active channel that this
// UpdateAddHTLC is binded to.
ChannelPoint wire.OutPoint
// 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 {
// ChannelPoint(8)
// ID(4)
// Expiry(4)
// Amount(8)
// PaymentHash(32)
// OnionBlob(1254)
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return readElements(r,
&c.ChannelPoint,
&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 {
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return writeElements(w,
c.ChannelPoint,
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 {
// 1342
return 36 + 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!
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return fmt.Errorf("amount paid cannot be negative")
}
// We're good!
return nil
}