htlcswitch: move hop iterator into htlcswitch/hop package

Prepares for onion blob decoding outside of htlcswitch.

htlcswitch/circuit.go

@@ -5,6 +5,7 @@ import (
 	"io"
 
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -51,7 +52,7 @@ type PaymentCircuit struct {
 
 	// ErrorEncrypter is used to re-encrypt the onion failure before
 	// sending it back to the originator of the payment.
-	ErrorEncrypter ErrorEncrypter
+	ErrorEncrypter hop.ErrorEncrypter
 
 	// LoadedFromDisk is set true for any circuits loaded after the circuit
 	// map is reloaded from disk.
@@ -136,7 +137,7 @@ func (c *PaymentCircuit) Encode(w io.Writer) error {
 	}
 
 	// Defaults to EncrypterTypeNone.
-	var encrypterType EncrypterType
+	var encrypterType hop.EncrypterType
 	if c.ErrorEncrypter != nil {
 		encrypterType = c.ErrorEncrypter.Type()
 	}
@@ -147,7 +148,7 @@ func (c *PaymentCircuit) Encode(w io.Writer) error {
 	}
 
 	// Skip encoding of error encrypter if this half add does not have one.
-	if encrypterType == EncrypterTypeNone {
+	if encrypterType == hop.EncrypterTypeNone {
 		return nil
 	}
 
@@ -183,23 +184,23 @@ func (c *PaymentCircuit) Decode(r io.Reader) error {
 		binary.BigEndian.Uint64(scratch[:]))
 
 	// Read the encrypter type used for this circuit.
-	var encrypterType EncrypterType
+	var encrypterType hop.EncrypterType
 	err := binary.Read(r, binary.BigEndian, &encrypterType)
 	if err != nil {
 		return err
 	}
 
 	switch encrypterType {
-	case EncrypterTypeNone:
+	case hop.EncrypterTypeNone:
 		// No encrypter was provided, such as when the payment is
 		// locally initiated.
 		return nil
 
-	case EncrypterTypeSphinx:
+	case hop.EncrypterTypeSphinx:
 		// Sphinx encrypter was used as this is a forwarded HTLC.
-		c.ErrorEncrypter = NewSphinxErrorEncrypter()
+		c.ErrorEncrypter = hop.NewSphinxErrorEncrypter()
 
-	case EncrypterTypeMock:
+	case hop.EncrypterTypeMock:
 		// Test encrypter.
 		c.ErrorEncrypter = NewMockObfuscator()
 

htlcswitch/circuit_map.go

@@ -179,7 +179,7 @@ type CircuitMapConfig struct {
 
 	// ExtractErrorEncrypter derives the shared secret used to encrypt
 	// errors from the obfuscator's ephemeral public key.
-	ExtractErrorEncrypter ErrorEncrypterExtracter
+	ExtractErrorEncrypter hop.ErrorEncrypterExtracter
 }
 
 // NewCircuitMap creates a new instance of the circuitMap.

htlcswitch/circuit_test.go

@@ -9,9 +9,10 @@ import (
 	"github.com/btcsuite/btcd/btcec"
 	bitcoinCfg "github.com/btcsuite/btcd/chaincfg"
 	"github.com/btcsuite/btcutil"
-	"github.com/lightningnetwork/lightning-onion"
+	sphinx "github.com/lightningnetwork/lightning-onion"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/htlcswitch"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -30,7 +31,7 @@ var (
 
 	// testExtracter is a precomputed extraction of testEphemeralKey, using
 	// the sphinxPrivKey.
-	testExtracter *htlcswitch.SphinxErrorEncrypter
+	testExtracter *hop.SphinxErrorEncrypter
 )
 
 func init() {
@@ -67,7 +68,7 @@ func initTestExtracter() {
 		testEphemeralKey,
 	)
 
-	sphinxExtracter, ok := obfuscator.(*htlcswitch.SphinxErrorEncrypter)
+	sphinxExtracter, ok := obfuscator.(*hop.SphinxErrorEncrypter)
 	if !ok {
 		panic("did not extract sphinx error encrypter")
 	}
@@ -81,7 +82,7 @@ func initTestExtracter() {
 
 // newOnionProcessor creates starts a new htlcswitch.OnionProcessor using a temp
 // db and no garbage collection.
-func newOnionProcessor(t *testing.T) *htlcswitch.OnionProcessor {
+func newOnionProcessor(t *testing.T) *hop.OnionProcessor {
 	sphinxRouter := sphinx.NewRouter(
 		sphinxPrivKey, &bitcoinCfg.SimNetParams, sphinx.NewMemoryReplayLog(),
 	)
@@ -90,7 +91,7 @@ func newOnionProcessor(t *testing.T) *htlcswitch.OnionProcessor {
 		t.Fatalf("unable to start sphinx router: %v", err)
 	}
 
-	return htlcswitch.NewOnionProcessor(sphinxRouter)
+	return hop.NewOnionProcessor(sphinxRouter)
 }
 
 // newCircuitMap creates a new htlcswitch.CircuitMap using a temp db and a
@@ -128,7 +129,7 @@ var halfCircuitTests = []struct {
 	outValue  btcutil.Amount
 	chanID    lnwire.ShortChannelID
 	htlcID    uint64
-	encrypter htlcswitch.ErrorEncrypter
+	encrypter hop.ErrorEncrypter
 }{
 	{
 		hash:      hash1,
@@ -1142,7 +1143,7 @@ func TestCircuitMapCloseOpenCircuits(t *testing.T) {
 			ChanID: chan1,
 			HtlcID: 3,
 		},
-		ErrorEncrypter: &htlcswitch.SphinxErrorEncrypter{
+		ErrorEncrypter: &hop.SphinxErrorEncrypter{
 			EphemeralKey: testEphemeralKey,
 		},
 	}

htlcswitch/failure.go

@@ -3,10 +3,9 @@ package htlcswitch
 import (
 	"bytes"
 	"fmt"
-	"io"
 
-	"github.com/btcsuite/btcd/btcec"
 	sphinx "github.com/lightningnetwork/lightning-onion"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -47,203 +46,15 @@ type ErrorDecrypter interface {
 	DecryptError(lnwire.OpaqueReason) (*ForwardingError, error)
 }
 
-// EncrypterType establishes an enum used in serialization to indicate how to
-// decode a concrete instance of the ErrorEncrypter interface.
-type EncrypterType byte
-
-const (
-	// EncrypterTypeNone signals that no error encyrpter is present, this
-	// can happen if the htlc is originates in the switch.
-	EncrypterTypeNone EncrypterType = 0
-
-	// EncrypterTypeSphinx is used to identify a sphinx onion error
-	// encrypter instance.
-	EncrypterTypeSphinx = 1
-
-	// EncrypterTypeMock is used to identify a mock obfuscator instance.
-	EncrypterTypeMock = 2
-)
-
 // UnknownEncrypterType is an error message used to signal that an unexpected
 // EncrypterType was encountered during decoding.
-type UnknownEncrypterType EncrypterType
+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)
 }
 
-// ErrorEncrypterExtracter defines a function signature that extracts an
-// ErrorEncrypter from an sphinx OnionPacket.
-type ErrorEncrypterExtracter func(*btcec.PublicKey) (ErrorEncrypter,
-	lnwire.FailCode)
-
-// ErrorEncrypter is an interface that is used to encrypt HTLC related errors
-// at the source of the error, and also at each intermediate hop all the way
-// back to the source of the payment.
-type ErrorEncrypter interface {
-	// EncryptFirstHop transforms a concrete failure message into an
-	// encrypted opaque failure reason. This method will be used at the
-	// source that the error occurs. It differs from IntermediateEncrypt
-	// slightly, in that it computes a proper MAC over the error.
-	EncryptFirstHop(lnwire.FailureMessage) (lnwire.OpaqueReason, error)
-
-	// EncryptMalformedError is similar to EncryptFirstHop (it adds the
-	// MAC), but it accepts an opaque failure reason rather than a failure
-	// message. This method is used when we receive an
-	// UpdateFailMalformedHTLC from the remote peer and then need to
-	// convert that into a proper error from only the raw bytes.
-	EncryptMalformedError(lnwire.OpaqueReason) lnwire.OpaqueReason
-
-	// IntermediateEncrypt wraps an already encrypted opaque reason error
-	// in an additional layer of onion encryption. This process repeats
-	// until the error arrives at the source of the payment.
-	IntermediateEncrypt(lnwire.OpaqueReason) lnwire.OpaqueReason
-
-	// Type returns an enum indicating the underlying concrete instance
-	// backing this interface.
-	Type() EncrypterType
-
-	// Encode serializes the encrypter's ephemeral public key to the given
-	// io.Writer.
-	Encode(io.Writer) error
-
-	// Decode deserializes the encrypter' ephemeral public key from the
-	// given io.Reader.
-	Decode(io.Reader) error
-
-	// Reextract rederives the encrypter using the extracter, performing an
-	// ECDH with the sphinx router's key and the ephemeral public key.
-	//
-	// NOTE: This should be called shortly after Decode to properly
-	// reinitialize the error encrypter.
-	Reextract(ErrorEncrypterExtracter) error
-}
-
-// SphinxErrorEncrypter is a concrete implementation of both the ErrorEncrypter
-// interface backed by an implementation of the Sphinx packet format. As a
-// result, all errors handled are themselves wrapped in layers of onion
-// encryption and must be treated as such accordingly.
-type SphinxErrorEncrypter struct {
-	*sphinx.OnionErrorEncrypter
-
-	EphemeralKey *btcec.PublicKey
-}
-
-// NewSphinxErrorEncrypter initializes a blank sphinx error encrypter, that
-// should be used to deserialize an encoded SphinxErrorEncrypter. Since the
-// actual encrypter is not stored in plaintext while at rest, reconstructing the
-// error encrypter requires:
-//   1) Decode: to deserialize the ephemeral public key.
-//   2) Reextract: to "unlock" the actual error encrypter using an active
-//        OnionProcessor.
-func NewSphinxErrorEncrypter() *SphinxErrorEncrypter {
-	return &SphinxErrorEncrypter{
-		OnionErrorEncrypter: nil,
-		EphemeralKey:        &btcec.PublicKey{},
-	}
-}
-
-// EncryptFirstHop transforms a concrete failure message into an encrypted
-// opaque failure reason. This method will be used at the source that the error
-// occurs. It differs from BackwardObfuscate slightly, in that it computes a
-// proper MAC over the error.
-//
-// NOTE: Part of the ErrorEncrypter interface.
-func (s *SphinxErrorEncrypter) EncryptFirstHop(failure lnwire.FailureMessage) (lnwire.OpaqueReason, error) {
-	var b bytes.Buffer
-	if err := lnwire.EncodeFailure(&b, failure, 0); err != nil {
-		return nil, err
-	}
-
-	// We pass a true as the first parameter to indicate that a MAC should
-	// be added.
-	return s.EncryptError(true, b.Bytes()), nil
-}
-
-// EncryptMalformedError is similar to EncryptFirstHop (it adds the MAC), but
-// it accepts an opaque failure reason rather than a failure message. This
-// method is used when we receive an UpdateFailMalformedHTLC from the remote
-// peer and then need to convert that into an proper error from only the raw
-// bytes.
-//
-// NOTE: Part of the ErrorEncrypter interface.
-func (s *SphinxErrorEncrypter) EncryptMalformedError(reason lnwire.OpaqueReason) lnwire.OpaqueReason {
-	return s.EncryptError(true, reason)
-}
-
-// IntermediateEncrypt wraps an already encrypted opaque reason error in an
-// additional layer of onion encryption. This process repeats until the error
-// arrives at the source of the payment. We re-encrypt the message on the
-// backwards path to ensure that the error is indistinguishable from any other
-// error seen.
-//
-// NOTE: Part of the ErrorEncrypter interface.
-func (s *SphinxErrorEncrypter) IntermediateEncrypt(reason lnwire.OpaqueReason) lnwire.OpaqueReason {
-	return s.EncryptError(false, reason)
-}
-
-// Type returns the identifier for a sphinx error encrypter.
-func (s *SphinxErrorEncrypter) Type() EncrypterType {
-	return EncrypterTypeSphinx
-}
-
-// Encode serializes the error encrypter' ephemeral public key to the provided
-// io.Writer.
-func (s *SphinxErrorEncrypter) Encode(w io.Writer) error {
-	ephemeral := s.EphemeralKey.SerializeCompressed()
-	_, err := w.Write(ephemeral)
-	return err
-}
-
-// Decode reconstructs the error encrypter's ephemeral public key from the
-// provided io.Reader.
-func (s *SphinxErrorEncrypter) Decode(r io.Reader) error {
-	var ephemeral [33]byte
-	if _, err := io.ReadFull(r, ephemeral[:]); err != nil {
-		return err
-	}
-
-	var err error
-	s.EphemeralKey, err = btcec.ParsePubKey(ephemeral[:], btcec.S256())
-	if err != nil {
-		return err
-	}
-
-	return nil
-}
-
-// Reextract rederives the error encrypter from the currently held EphemeralKey.
-// This intended to be used shortly after Decode, to fully initialize a
-// SphinxErrorEncrypter.
-func (s *SphinxErrorEncrypter) Reextract(
-	extract ErrorEncrypterExtracter) error {
-
-	obfuscator, failcode := extract(s.EphemeralKey)
-	if failcode != lnwire.CodeNone {
-		// This should never happen, since we already validated that
-		// this obfuscator can be extracted when it was received in the
-		// link.
-		return fmt.Errorf("unable to reconstruct onion "+
-			"obfuscator, got failcode: %d", failcode)
-	}
-
-	sphinxEncrypter, ok := obfuscator.(*SphinxErrorEncrypter)
-	if !ok {
-		return fmt.Errorf("incorrect onion error extracter")
-	}
-
-	// Copy the freshly extracted encrypter.
-	s.OnionErrorEncrypter = sphinxEncrypter.OnionErrorEncrypter
-
-	return nil
-
-}
-
-// A compile time check to ensure SphinxErrorEncrypter implements the
-// ErrorEncrypter interface.
-var _ ErrorEncrypter = (*SphinxErrorEncrypter)(nil)
-
 // OnionErrorDecrypter is the interface that provides onion level error
 // decryption.
 type OnionErrorDecrypter interface {

htlcswitch/hop/error_encryptor.go

@@ -0,0 +1,205 @@
+package hop
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+
+	"github.com/btcsuite/btcd/btcec"
+	sphinx "github.com/lightningnetwork/lightning-onion"
+	"github.com/lightningnetwork/lnd/lnwire"
+)
+
+// EncrypterType establishes an enum used in serialization to indicate how to
+// decode a concrete instance of the ErrorEncrypter interface.
+type EncrypterType byte
+
+const (
+	// EncrypterTypeNone signals that no error encyrpter is present, this
+	// can happen if the htlc is originates in the switch.
+	EncrypterTypeNone EncrypterType = 0
+
+	// EncrypterTypeSphinx is used to identify a sphinx onion error
+	// encrypter instance.
+	EncrypterTypeSphinx = 1
+
+	// EncrypterTypeMock is used to identify a mock obfuscator instance.
+	EncrypterTypeMock = 2
+)
+
+// ErrorEncrypterExtracter defines a function signature that extracts an
+// ErrorEncrypter from an sphinx OnionPacket.
+type ErrorEncrypterExtracter func(*btcec.PublicKey) (ErrorEncrypter,
+	lnwire.FailCode)
+
+// ErrorEncrypter is an interface that is used to encrypt HTLC related errors
+// at the source of the error, and also at each intermediate hop all the way
+// back to the source of the payment.
+type ErrorEncrypter interface {
+	// EncryptFirstHop transforms a concrete failure message into an
+	// encrypted opaque failure reason. This method will be used at the
+	// source that the error occurs. It differs from IntermediateEncrypt
+	// slightly, in that it computes a proper MAC over the error.
+	EncryptFirstHop(lnwire.FailureMessage) (lnwire.OpaqueReason, error)
+
+	// EncryptMalformedError is similar to EncryptFirstHop (it adds the
+	// MAC), but it accepts an opaque failure reason rather than a failure
+	// message. This method is used when we receive an
+	// UpdateFailMalformedHTLC from the remote peer and then need to
+	// convert that into a proper error from only the raw bytes.
+	EncryptMalformedError(lnwire.OpaqueReason) lnwire.OpaqueReason
+
+	// IntermediateEncrypt wraps an already encrypted opaque reason error
+	// in an additional layer of onion encryption. This process repeats
+	// until the error arrives at the source of the payment.
+	IntermediateEncrypt(lnwire.OpaqueReason) lnwire.OpaqueReason
+
+	// Type returns an enum indicating the underlying concrete instance
+	// backing this interface.
+	Type() EncrypterType
+
+	// Encode serializes the encrypter's ephemeral public key to the given
+	// io.Writer.
+	Encode(io.Writer) error
+
+	// Decode deserializes the encrypter' ephemeral public key from the
+	// given io.Reader.
+	Decode(io.Reader) error
+
+	// Reextract rederives the encrypter using the extracter, performing an
+	// ECDH with the sphinx router's key and the ephemeral public key.
+	//
+	// NOTE: This should be called shortly after Decode to properly
+	// reinitialize the error encrypter.
+	Reextract(ErrorEncrypterExtracter) error
+}
+
+// SphinxErrorEncrypter is a concrete implementation of both the ErrorEncrypter
+// interface backed by an implementation of the Sphinx packet format. As a
+// result, all errors handled are themselves wrapped in layers of onion
+// encryption and must be treated as such accordingly.
+type SphinxErrorEncrypter struct {
+	*sphinx.OnionErrorEncrypter
+
+	EphemeralKey *btcec.PublicKey
+}
+
+// NewSphinxErrorEncrypter initializes a blank sphinx error encrypter, that
+// should be used to deserialize an encoded SphinxErrorEncrypter. Since the
+// actual encrypter is not stored in plaintext while at rest, reconstructing the
+// error encrypter requires:
+//   1) Decode: to deserialize the ephemeral public key.
+//   2) Reextract: to "unlock" the actual error encrypter using an active
+//        OnionProcessor.
+func NewSphinxErrorEncrypter() *SphinxErrorEncrypter {
+	return &SphinxErrorEncrypter{
+		OnionErrorEncrypter: nil,
+		EphemeralKey:        &btcec.PublicKey{},
+	}
+}
+
+// EncryptFirstHop transforms a concrete failure message into an encrypted
+// opaque failure reason. This method will be used at the source that the error
+// occurs. It differs from BackwardObfuscate slightly, in that it computes a
+// proper MAC over the error.
+//
+// NOTE: Part of the ErrorEncrypter interface.
+func (s *SphinxErrorEncrypter) EncryptFirstHop(
+	failure lnwire.FailureMessage) (lnwire.OpaqueReason, error) {
+
+	var b bytes.Buffer
+	if err := lnwire.EncodeFailure(&b, failure, 0); err != nil {
+		return nil, err
+	}
+
+	// We pass a true as the first parameter to indicate that a MAC should
+	// be added.
+	return s.EncryptError(true, b.Bytes()), nil
+}
+
+// EncryptMalformedError is similar to EncryptFirstHop (it adds the MAC), but
+// it accepts an opaque failure reason rather than a failure message. This
+// method is used when we receive an UpdateFailMalformedHTLC from the remote
+// peer and then need to convert that into an proper error from only the raw
+// bytes.
+//
+// NOTE: Part of the ErrorEncrypter interface.
+func (s *SphinxErrorEncrypter) EncryptMalformedError(
+	reason lnwire.OpaqueReason) lnwire.OpaqueReason {
+
+	return s.EncryptError(true, reason)
+}
+
+// IntermediateEncrypt wraps an already encrypted opaque reason error in an
+// additional layer of onion encryption. This process repeats until the error
+// arrives at the source of the payment. We re-encrypt the message on the
+// backwards path to ensure that the error is indistinguishable from any other
+// error seen.
+//
+// NOTE: Part of the ErrorEncrypter interface.
+func (s *SphinxErrorEncrypter) IntermediateEncrypt(
+	reason lnwire.OpaqueReason) lnwire.OpaqueReason {
+
+	return s.EncryptError(false, reason)
+}
+
+// Type returns the identifier for a sphinx error encrypter.
+func (s *SphinxErrorEncrypter) Type() EncrypterType {
+	return EncrypterTypeSphinx
+}
+
+// Encode serializes the error encrypter' ephemeral public key to the provided
+// io.Writer.
+func (s *SphinxErrorEncrypter) Encode(w io.Writer) error {
+	ephemeral := s.EphemeralKey.SerializeCompressed()
+	_, err := w.Write(ephemeral)
+	return err
+}
+
+// Decode reconstructs the error encrypter's ephemeral public key from the
+// provided io.Reader.
+func (s *SphinxErrorEncrypter) Decode(r io.Reader) error {
+	var ephemeral [33]byte
+	if _, err := io.ReadFull(r, ephemeral[:]); err != nil {
+		return err
+	}
+
+	var err error
+	s.EphemeralKey, err = btcec.ParsePubKey(ephemeral[:], btcec.S256())
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Reextract rederives the error encrypter from the currently held EphemeralKey.
+// This intended to be used shortly after Decode, to fully initialize a
+// SphinxErrorEncrypter.
+func (s *SphinxErrorEncrypter) Reextract(
+	extract ErrorEncrypterExtracter) error {
+
+	obfuscator, failcode := extract(s.EphemeralKey)
+	if failcode != lnwire.CodeNone {
+		// This should never happen, since we already validated that
+		// this obfuscator can be extracted when it was received in the
+		// link.
+		return fmt.Errorf("unable to reconstruct onion "+
+			"obfuscator, got failcode: %d", failcode)
+	}
+
+	sphinxEncrypter, ok := obfuscator.(*SphinxErrorEncrypter)
+	if !ok {
+		return fmt.Errorf("incorrect onion error extracter")
+	}
+
+	// Copy the freshly extracted encrypter.
+	s.OnionErrorEncrypter = sphinxEncrypter.OnionErrorEncrypter
+
+	return nil
+
+}
+
+// A compile time check to ensure SphinxErrorEncrypter implements the
+// ErrorEncrypter interface.
+var _ ErrorEncrypter = (*SphinxErrorEncrypter)(nil)

htlcswitch/hop/iterator.go

@@ -1,4 +1,4 @@
-package htlcswitch
+package hop
 
 import (
 	"bytes"
@@ -6,23 +6,22 @@ import (
 	"io"
 
 	"github.com/btcsuite/btcd/btcec"
-	"github.com/lightningnetwork/lightning-onion"
+	sphinx "github.com/lightningnetwork/lightning-onion"
-	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
-// HopIterator is an interface that abstracts away the routing information
+// Iterator is an interface that abstracts away the routing information
 // included in HTLC's which includes the entirety of the payment path of an
 // HTLC. This interface provides two basic method which carry out: how to
 // interpret the forwarding information encoded within the HTLC packet, and hop
 // to encode the forwarding information for the _next_ hop.
-type HopIterator interface {
+type Iterator interface {
 	// ForwardingInstructions returns the set of fields that detail exactly
 	// _how_ this hop should forward the HTLC to the next hop.
 	// Additionally, the information encoded within the returned
 	// ForwardingInfo is to be used by each hop to authenticate the
 	// information given to it by the prior hop.
-	ForwardingInstructions() (hop.ForwardingInfo, error)
+	ForwardingInstructions() (ForwardingInfo, error)
 
 	// ExtraOnionBlob returns the additional EOB data (if available).
 	ExtraOnionBlob() []byte
@@ -64,7 +63,7 @@ func makeSphinxHopIterator(ogPacket *sphinx.OnionPacket,
 
 // A compile time check to ensure sphinxHopIterator implements the HopIterator
 // interface.
-var _ HopIterator = (*sphinxHopIterator)(nil)
+var _ Iterator = (*sphinxHopIterator)(nil)
 
 // Encode encodes iterator and writes it to the writer.
 //
@@ -79,32 +78,30 @@ func (r *sphinxHopIterator) EncodeNextHop(w io.Writer) error {
 // hop to authenticate the information given to it by the prior hop.
 //
 // NOTE: Part of the HopIterator interface.
-func (r *sphinxHopIterator) ForwardingInstructions() (
+func (r *sphinxHopIterator) ForwardingInstructions() (ForwardingInfo, error) {
-	hop.ForwardingInfo, error) {
-
 	switch r.processedPacket.Payload.Type {
 	// If this is the legacy payload, then we'll extract the information
 	// directly from the pre-populated ForwardingInstructions field.
 	case sphinx.PayloadLegacy:
 		fwdInst := r.processedPacket.ForwardingInstructions
-		p := hop.NewLegacyPayload(fwdInst)
+		p := NewLegacyPayload(fwdInst)
 
 		return p.ForwardingInfo(), nil
 
 	// Otherwise, if this is the TLV payload, then we'll make a new stream
 	// to decode only what we need to make routing decisions.
 	case sphinx.PayloadTLV:
-		p, err := hop.NewPayloadFromReader(bytes.NewReader(
+		p, err := NewPayloadFromReader(bytes.NewReader(
 			r.processedPacket.Payload.Payload,
 		))
 		if err != nil {
-			return hop.ForwardingInfo{}, err
+			return ForwardingInfo{}, err
 		}
 
 		return p.ForwardingInfo(), nil
 
 	default:
-		return hop.ForwardingInfo{}, fmt.Errorf("unknown "+
+		return ForwardingInfo{}, fmt.Errorf("unknown "+
 			"sphinx payload type: %v",
 			r.processedPacket.Payload.Type)
 	}
@@ -164,7 +161,7 @@ func (p *OnionProcessor) Stop() error {
 // instance using the rHash as the associated data when checking the relevant
 // MACs during the decoding process.
 func (p *OnionProcessor) DecodeHopIterator(r io.Reader, rHash []byte,
-	incomingCltv uint32) (HopIterator, lnwire.FailCode) {
+	incomingCltv uint32) (Iterator, lnwire.FailCode) {
 
 	onionPkt := &sphinx.OnionPacket{}
 	if err := onionPkt.Decode(r); err != nil {
@@ -216,7 +213,7 @@ type DecodeHopIteratorRequest struct {
 // DecodeHopIteratorResponse encapsulates the outcome of a batched sphinx onion
 // processing.
 type DecodeHopIteratorResponse struct {
-	HopIterator HopIterator
+	HopIterator Iterator
 	FailCode    lnwire.FailCode
 }
 
@@ -225,7 +222,7 @@ type DecodeHopIteratorResponse struct {
 //
 // NOTE: The HopIterator should be considered invalid if the fail code is
 // anything but lnwire.CodeNone.
-func (r *DecodeHopIteratorResponse) Result() (HopIterator, lnwire.FailCode) {
+func (r *DecodeHopIteratorResponse) Result() (Iterator, lnwire.FailCode) {
 	return r.HopIterator, r.FailCode
 }
 

htlcswitch/hop/iterator_test.go

@@ -1,4 +1,4 @@
-package htlcswitch
+package hop
 
 import (
 	"bytes"
@@ -7,7 +7,6 @@ import (
 
 	"github.com/davecgh/go-spew/spew"
 	sphinx "github.com/lightningnetwork/lightning-onion"
-	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/record"
 	"github.com/lightningnetwork/lnd/tlv"
@@ -30,7 +29,7 @@ func TestSphinxHopIteratorForwardingInstructions(t *testing.T) {
 	// Next, we'll make the hop forwarding information that we should
 	// extract each type, no matter the payload type.
 	nextAddrInt := binary.BigEndian.Uint64(hopData.NextAddress[:])
-	expectedFwdInfo := hop.ForwardingInfo{
+	expectedFwdInfo := ForwardingInfo{
 		NextHop:         lnwire.NewShortChanIDFromInt(nextAddrInt),
 		AmountToForward: lnwire.MilliSatoshi(hopData.ForwardAmount),
 		OutgoingCTLV:    hopData.OutgoingCltv,
@@ -54,7 +53,7 @@ func TestSphinxHopIteratorForwardingInstructions(t *testing.T) {
 
 	var testCases = []struct {
 		sphinxPacket    *sphinx.ProcessedPacket
-		expectedFwdInfo hop.ForwardingInfo
+		expectedFwdInfo ForwardingInfo
 	}{
 		// A regular legacy payload that signals more hops.
 		{

htlcswitch/hop/log.go

@@ -0,0 +1,16 @@
+package hop
+
+import (
+	"github.com/btcsuite/btclog"
+)
+
+// log is a logger that is initialized with no output filters.  This
+// means the package will not perform any logging by default until the caller
+// requests it.
+var log btclog.Logger
+
+// UseLogger uses a specified Logger to output package logging info. This
+// function is called from the parent package htlcswitch logger initialization.
+func UseLogger(logger btclog.Logger) {
+	log = logger
+}

htlcswitch/link.go

@@ -144,12 +144,12 @@ type ChannelLinkConfig struct {
 	//
 	// NOTE: This function assumes the same set of readers and preimages
 	// are always presented for the same identifier.
-	DecodeHopIterators func([]byte, []DecodeHopIteratorRequest) (
+	DecodeHopIterators func([]byte, []hop.DecodeHopIteratorRequest) (
-		[]DecodeHopIteratorResponse, error)
+		[]hop.DecodeHopIteratorResponse, error)
 
 	// ExtractErrorEncrypter function is responsible for decoding HTLC
 	// Sphinx onion blob, and creating onion failure obfuscator.
-	ExtractErrorEncrypter ErrorEncrypterExtracter
+	ExtractErrorEncrypter hop.ErrorEncrypterExtracter
 
 	// FetchLastChannelUpdate retrieves the latest routing policy for a
 	// target channel. This channel will typically be the outgoing channel
@@ -379,7 +379,7 @@ type channelLink struct {
 // hodlHtlc contains htlc data that is required for resolution.
 type hodlHtlc struct {
 	pd         *lnwallet.PaymentDescriptor
-	obfuscator ErrorEncrypter
+	obfuscator hop.ErrorEncrypter
 }
 
 // NewChannelLink creates a new instance of a ChannelLink given a configuration
@@ -2553,7 +2553,9 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 	l.tracef("processing %d remote adds for height %d",
 		len(lockedInHtlcs), fwdPkg.Height)
 
-	decodeReqs := make([]DecodeHopIteratorRequest, 0, len(lockedInHtlcs))
+	decodeReqs := make(
+		[]hop.DecodeHopIteratorRequest, 0, len(lockedInHtlcs),
+	)
 	for _, pd := range lockedInHtlcs {
 		switch pd.EntryType {
 
@@ -2565,7 +2567,7 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 			// which process the Sphinx packet.
 			onionReader := bytes.NewReader(pd.OnionBlob)
 
-			req := DecodeHopIteratorRequest{
+			req := hop.DecodeHopIteratorRequest{
 				OnionReader:  onionReader,
 				RHash:        pd.RHash[:],
 				IncomingCltv: pd.Timeout,
@@ -2850,7 +2852,7 @@ func (l *channelLink) processRemoteAdds(fwdPkg *channeldb.FwdPkg,
 // processExitHop handles an htlc for which this link is the exit hop. It
 // returns a boolean indicating whether the commitment tx needs an update.
 func (l *channelLink) processExitHop(pd *lnwallet.PaymentDescriptor,
-	obfuscator ErrorEncrypter, fwdInfo hop.ForwardingInfo,
+	obfuscator hop.ErrorEncrypter, fwdInfo hop.ForwardingInfo,
 	heightNow uint32, eob []byte) (bool, error) {
 
 	// If hodl.ExitSettle is requested, we will not validate the final hop's
@@ -3021,7 +3023,7 @@ func (l *channelLink) handleBatchFwdErrs(errChan chan error) {
 // sendHTLCError functions cancels HTLC and send cancel message back to the
 // peer from which HTLC was received.
 func (l *channelLink) sendHTLCError(htlcIndex uint64, failure lnwire.FailureMessage,
-	e ErrorEncrypter, sourceRef *channeldb.AddRef) {
+	e hop.ErrorEncrypter, sourceRef *channeldb.AddRef) {
 
 	reason, err := e.EncryptFirstHop(failure)
 	if err != nil {

htlcswitch/link_test.go

@@ -1292,7 +1292,7 @@ func TestChannelLinkMultiHopDecodeError(t *testing.T) {
 
 	// Replace decode function with another which throws an error.
 	n.carolChannelLink.cfg.ExtractErrorEncrypter = func(
-		*btcec.PublicKey) (ErrorEncrypter, lnwire.FailCode) {
+		*btcec.PublicKey) (hop.ErrorEncrypter, lnwire.FailCode) {
 		return nil, lnwire.CodeInvalidOnionVersion
 	}
 
@@ -1666,7 +1666,7 @@ func newSingleLinkTestHarness(chanAmt, chanReserve btcutil.Amount) (
 		ForwardPackets:     aliceSwitch.ForwardPackets,
 		DecodeHopIterators: decoder.DecodeHopIterators,
 		ExtractErrorEncrypter: func(*btcec.PublicKey) (
-			ErrorEncrypter, lnwire.FailCode) {
+			hop.ErrorEncrypter, lnwire.FailCode) {
 			return obfuscator, lnwire.CodeNone
 		},
 		FetchLastChannelUpdate: mockGetChanUpdateMessage,
@@ -4230,7 +4230,7 @@ func (h *persistentLinkHarness) restartLink(
 		ForwardPackets:     aliceSwitch.ForwardPackets,
 		DecodeHopIterators: decoder.DecodeHopIterators,
 		ExtractErrorEncrypter: func(*btcec.PublicKey) (
-			ErrorEncrypter, lnwire.FailCode) {
+			hop.ErrorEncrypter, lnwire.FailCode) {
 			return obfuscator, lnwire.CodeNone
 		},
 		FetchLastChannelUpdate: mockGetChanUpdateMessage,

htlcswitch/log.go

@@ -3,6 +3,7 @@ package htlcswitch
 import (
 	"github.com/btcsuite/btclog"
 	"github.com/lightningnetwork/lnd/build"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 )
 
 // log is a logger that is initialized with no output filters.  This
@@ -12,7 +13,10 @@ var log btclog.Logger
 
 // The default amount of logging is none.
 func init() {
-	UseLogger(build.NewSubLogger("HSWC", nil))
+	logger := build.NewSubLogger("HSWC", nil)
+
+	UseLogger(logger)
+	hop.UseLogger(logger)
 }
 
 // DisableLog disables all library log output.  Logging output is disabled

htlcswitch/mock.go

@@ -272,7 +272,7 @@ type mockHopIterator struct {
 	hops []hop.ForwardingInfo
 }
 
-func newMockHopIterator(hops ...hop.ForwardingInfo) HopIterator {
+func newMockHopIterator(hops ...hop.ForwardingInfo) hop.Iterator {
 	return &mockHopIterator{hops: hops}
 }
 
@@ -289,7 +289,8 @@ func (r *mockHopIterator) ExtraOnionBlob() []byte {
 }
 
 func (r *mockHopIterator) ExtractErrorEncrypter(
-	extracter ErrorEncrypterExtracter) (ErrorEncrypter, lnwire.FailCode) {
+	extracter hop.ErrorEncrypterExtracter) (hop.ErrorEncrypter,
+	lnwire.FailCode) {
 
 	return extracter(nil)
 }
@@ -331,7 +332,7 @@ func encodeFwdInfo(w io.Writer, f *hop.ForwardingInfo) error {
 	return nil
 }
 
-var _ HopIterator = (*mockHopIterator)(nil)
+var _ hop.Iterator = (*mockHopIterator)(nil)
 
 // mockObfuscator mock implementation of the failure obfuscator which only
 // encodes the failure and do not makes any onion obfuscation.
@@ -340,7 +341,7 @@ type mockObfuscator struct {
 }
 
 // NewMockObfuscator initializes a dummy mockObfuscator used for testing.
-func NewMockObfuscator() ErrorEncrypter {
+func NewMockObfuscator() hop.ErrorEncrypter {
 	return &mockObfuscator{}
 }
 
@@ -348,8 +349,8 @@ func (o *mockObfuscator) OnionPacket() *sphinx.OnionPacket {
 	return o.ogPacket
 }
 
-func (o *mockObfuscator) Type() EncrypterType {
+func (o *mockObfuscator) Type() hop.EncrypterType {
-	return EncrypterTypeMock
+	return hop.EncrypterTypeMock
 }
 
 func (o *mockObfuscator) Encode(w io.Writer) error {
@@ -360,7 +361,9 @@ func (o *mockObfuscator) Decode(r io.Reader) error {
 	return nil
 }
 
-func (o *mockObfuscator) Reextract(extracter ErrorEncrypterExtracter) error {
+func (o *mockObfuscator) Reextract(
+	extracter hop.ErrorEncrypterExtracter) error {
+
 	return nil
 }
 
@@ -411,19 +414,19 @@ var _ ErrorDecrypter = (*mockDeobfuscator)(nil)
 type mockIteratorDecoder struct {
 	mu sync.RWMutex
 
-	responses map[[32]byte][]DecodeHopIteratorResponse
+	responses map[[32]byte][]hop.DecodeHopIteratorResponse
 
 	decodeFail bool
 }
 
 func newMockIteratorDecoder() *mockIteratorDecoder {
 	return &mockIteratorDecoder{
-		responses: make(map[[32]byte][]DecodeHopIteratorResponse),
+		responses: make(map[[32]byte][]hop.DecodeHopIteratorResponse),
 	}
 }
 
 func (p *mockIteratorDecoder) DecodeHopIterator(r io.Reader, rHash []byte,
-	cltv uint32) (HopIterator, lnwire.FailCode) {
+	cltv uint32) (hop.Iterator, lnwire.FailCode) {
 
 	var b [4]byte
 	_, err := r.Read(b[:])
@@ -446,7 +449,8 @@ func (p *mockIteratorDecoder) DecodeHopIterator(r io.Reader, rHash []byte,
 }
 
 func (p *mockIteratorDecoder) DecodeHopIterators(id []byte,
-	reqs []DecodeHopIteratorRequest) ([]DecodeHopIteratorResponse, error) {
+	reqs []hop.DecodeHopIteratorRequest) (
+	[]hop.DecodeHopIteratorResponse, error) {
 
 	idHash := sha256.Sum256(id)
 
@@ -459,7 +463,7 @@ func (p *mockIteratorDecoder) DecodeHopIterators(id []byte,
 
 	batchSize := len(reqs)
 
-	resps := make([]DecodeHopIteratorResponse, 0, batchSize)
+	resps := make([]hop.DecodeHopIteratorResponse, 0, batchSize)
 	for _, req := range reqs {
 		iterator, failcode := p.DecodeHopIterator(
 			req.OnionReader, req.RHash, req.IncomingCltv,
@@ -469,7 +473,7 @@ func (p *mockIteratorDecoder) DecodeHopIterators(id []byte,
 			failcode = lnwire.CodeTemporaryChannelFailure
 		}
 
-		resp := DecodeHopIteratorResponse{
+		resp := hop.DecodeHopIteratorResponse{
 			HopIterator: iterator,
 			FailCode:    failcode,
 		}

htlcswitch/packet.go

@@ -2,6 +2,7 @@ package htlcswitch
 
 import (
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -54,7 +55,7 @@ type htlcPacket struct {
 
 	// obfuscator contains the necessary state to allow the switch to wrap
 	// any forwarded errors in an additional layer of encryption.
-	obfuscator ErrorEncrypter
+	obfuscator hop.ErrorEncrypter
 
 	// localFailure is set to true if an HTLC fails for a local payment before
 	// the first hop. In this case, the failure reason is simply encoded, not

htlcswitch/switch.go

@@ -143,7 +143,7 @@ type Config struct {
 	// ExtractErrorEncrypter is an interface allowing switch to reextract
 	// error encrypters stored in the circuit map on restarts, since they
 	// are not stored directly within the database.
-	ExtractErrorEncrypter ErrorEncrypterExtracter
+	ExtractErrorEncrypter hop.ErrorEncrypterExtracter
 
 	// FetchLastChannelUpdate retrieves the latest routing policy for a
 	// target channel. This channel will typically be the outgoing channel

htlcswitch/test_utils.go

@@ -1054,7 +1054,7 @@ func createTwoClusterChannels(aliceToBob, bobToCarol btcutil.Amount) (
 type hopNetwork struct {
 	feeEstimator *mockFeeEstimator
 	globalPolicy ForwardingPolicy
-	obfuscator   ErrorEncrypter
+	obfuscator   hop.ErrorEncrypter
 
 	defaultDelta uint32
 }
@@ -1101,7 +1101,7 @@ func (h *hopNetwork) createChannelLink(server, peer *mockServer,
 			ForwardPackets:     server.htlcSwitch.ForwardPackets,
 			DecodeHopIterators: decoder.DecodeHopIterators,
 			ExtractErrorEncrypter: func(*btcec.PublicKey) (
-				ErrorEncrypter, lnwire.FailCode) {
+				hop.ErrorEncrypter, lnwire.FailCode) {
 				return h.obfuscator, lnwire.CodeNone
 			},
 			FetchLastChannelUpdate: mockGetChanUpdateMessage,

server.go

@@ -34,6 +34,7 @@ import (
 	"github.com/lightningnetwork/lnd/contractcourt"
 	"github.com/lightningnetwork/lnd/discovery"
 	"github.com/lightningnetwork/lnd/htlcswitch"
+	"github.com/lightningnetwork/lnd/htlcswitch/hop"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lncfg"
@@ -208,7 +209,7 @@ type server struct {
 
 	chainArb *contractcourt.ChainArbitrator
 
-	sphinx *htlcswitch.OnionProcessor
+	sphinx *hop.OnionProcessor
 
 	towerClient wtclient.Client
 
@@ -367,7 +368,7 @@ func newServer(listenAddrs []net.Addr, chanDB *channeldb.DB,
 
 		// TODO(roasbeef): derive proper onion key based on rotation
 		// schedule
-		sphinx: htlcswitch.NewOnionProcessor(sphinxRouter),
+		sphinx: hop.NewOnionProcessor(sphinxRouter),
 
 		persistentPeers:         make(map[string]struct{}),
 		persistentPeersBackoff:  make(map[string]time.Duration),