lnd: hook up encrypted onion error scaffolding

In this commit daemon have been changed to set the proper hooks in the
channel link and switch subsystems so that they could send and receive
encrypted onion errors.

server.go

@@ -71,7 +71,7 @@ type server struct {
 
 	utxoNursery *utxoNursery
 
-	sphinx *sphinx.Router
+	sphinx *htlcswitch.OnionProcessor
 
 	connMgr *connmgr.ConnManager
 
@@ -126,7 +126,8 @@ func newServer(listenAddrs []string, chanDB *channeldb.DB, cc *chainControl,
 
 		// TODO(roasbeef): derive proper onion key based on rotation
 		// schedule
-		sphinx:      sphinx.NewRouter(privKey, activeNetParams.Params),
+		sphinx: htlcswitch.NewOnionProcessor(
+			sphinx.NewRouter(privKey, activeNetParams.Params)),
 		lightningID: sha256.Sum256(serializedPubKey),
 
 		persistentPeers:    make(map[string]struct{}),
@@ -236,11 +237,19 @@ func newServer(listenAddrs []string, chanDB *channeldb.DB, cc *chainControl,
 		Chain:     cc.chainIO,
 		ChainView: cc.chainView,
 		SendToSwitch: func(firstHop *btcec.PublicKey,
-			htlcAdd *lnwire.UpdateAddHTLC) ([32]byte, error) {
+			htlcAdd *lnwire.UpdateAddHTLC,
+			circuit *sphinx.Circuit) ([32]byte, error) {
+
+			// Initialize the data obfuscator in order to be able to decode the
+			// onion failure and wrap it so that we could process lnwire onion
+			// failures.
+			failureDeobfuscator := &htlcswitch.FailureDeobfuscator{
+				OnionDeobfuscator: sphinx.NewOnionDeobfuscator(circuit),
+			}
 
 			var firstHopPub [33]byte
 			copy(firstHopPub[:], firstHop.SerializeCompressed())
-			return s.htlcSwitch.SendHTLC(firstHopPub, htlcAdd)
+			return s.htlcSwitch.SendHTLC(firstHopPub, htlcAdd, failureDeobfuscator)
 		},
 	})
 	if err != nil {