lnd.xprv/htlcswitch/failure.go

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package htlcswitch
import (
"bytes"
"fmt"
sphinx "github.com/lightningnetwork/lightning-onion"
"github.com/lightningnetwork/lnd/htlcswitch/hop"
"github.com/lightningnetwork/lnd/lnwire"
)
// ForwardingError wraps an lnwire.FailureMessage in a struct that also
// includes the source of the error.
type ForwardingError struct {
// FailureSourceIdx is the index of the node that sent the failure. With
// this information, the dispatcher of a payment can modify their set of
// candidate routes in response to the type of failure extracted. Index
// zero is the self node.
FailureSourceIdx int
// ExtraMsg is an additional error message that callers can provide in
// order to provide context specific error details.
ExtraMsg string
lnwire.FailureMessage
}
// Error implements the built-in error interface. We use this method to allow
// the switch or any callers to insert additional context to the error message
// returned.
func (f *ForwardingError) Error() string {
if f.ExtraMsg == "" {
return fmt.Sprintf("%v", f.FailureMessage)
}
return fmt.Sprintf("%v: %v", f.FailureMessage, f.ExtraMsg)
}
// ErrorDecrypter is an interface that is used to decrypt the onion encrypted
// failure reason an extra out a well formed error.
type ErrorDecrypter interface {
// DecryptError peels off each layer of onion encryption from the first
// hop, to the source of the error. A fully populated
// lnwire.FailureMessage is returned along with the source of the
// error.
DecryptError(lnwire.OpaqueReason) (*ForwardingError, error)
}
// UnknownEncrypterType is an error message used to signal that an unexpected
// EncrypterType was encountered during decoding.
type UnknownEncrypterType hop.EncrypterType
// Error returns a formatted error indicating the invalid EncrypterType.
func (e UnknownEncrypterType) Error() string {
return fmt.Sprintf("unknown error encrypter type: %d", e)
}
// OnionErrorDecrypter is the interface that provides onion level error
// decryption.
type OnionErrorDecrypter interface {
// DecryptError attempts to decrypt the passed encrypted error response.
// The onion failure is encrypted in backward manner, starting from the
// node where error have occurred. As a result, in order to decrypt the
// error we need get all shared secret and apply decryption in the
// reverse order.
DecryptError(encryptedData []byte) (*sphinx.DecryptedError, error)
}
// SphinxErrorDecrypter wraps the sphinx data SphinxErrorDecrypter and maps the
// returned errors to concrete lnwire.FailureMessage instances.
type SphinxErrorDecrypter struct {
OnionErrorDecrypter
}
// DecryptError peels off each layer of onion encryption from the first hop, to
// the source of the error. A fully populated lnwire.FailureMessage is returned
// along with the source of the error.
//
// NOTE: Part of the ErrorDecrypter interface.
func (s *SphinxErrorDecrypter) DecryptError(reason lnwire.OpaqueReason) (
*ForwardingError, error) {
failure, err := s.OnionErrorDecrypter.DecryptError(reason)
if err != nil {
return nil, err
}
// Decode the failure. If an error occurs, we leave the failure message
// field nil.
r := bytes.NewReader(failure.Message)
failureMsg, err := lnwire.DecodeFailure(r, 0)
if err != nil {
return &ForwardingError{
FailureSourceIdx: failure.SenderIdx,
}, nil
}
return &ForwardingError{
FailureSourceIdx: failure.SenderIdx,
FailureMessage: failureMsg,
}, nil
}
// A compile time check to ensure ErrorDecrypter implements the Deobfuscator
// interface.
var _ ErrorDecrypter = (*SphinxErrorDecrypter)(nil)