htlcswitch+router+server: handle payment error topology updates

In previous commits we have intoduced the onion errors. Some of this
errors include lnwire.ChannelUpdate message. In order to change
topology accordingly to the received error, from nodes where failure
have occured, we have to propogate the update to the router subsystem.

htlcswitch/switch.go

@@ -88,6 +88,10 @@ type Config struct {
 	// or forced unilateral closure of the channel initiated by a local
 	// subsystem.
 	LocalChannelClose func(pubKey []byte, request *ChanClose)
+
+	// UpdateTopology sends the onion error failure topology update to router
+	// subsystem.
+	UpdateTopology func(msg *lnwire.ChannelUpdate) error
 }
 
 // Switch is the central messaging bus for all incoming/outgoing HTLCs.
@@ -313,6 +317,31 @@ func (s *Switch) handleLocalDispatch(payment *pendingPayment, packet *htlcPacket
 				err)
 			log.Error(userErr)
 		} else {
+			// Process payment failure by updating the lightning network
+			// topology by using router subsystem handler.
+			var update *lnwire.ChannelUpdate
+
+			switch failure := failure.(type) {
+			case *lnwire.FailTemporaryChannelFailure:
+				update = failure.Update
+			case *lnwire.FailAmountBelowMinimum:
+				update = &failure.Update
+			case *lnwire.FailFeeInsufficient:
+				update = &failure.Update
+			case *lnwire.FailIncorrectCltvExpiry:
+				update = &failure.Update
+			case *lnwire.FailExpiryTooSoon:
+				update = &failure.Update
+			case *lnwire.FailChannelDisabled:
+				update = &failure.Update
+			}
+
+			if update != nil {
+				log.Info("Received payment failure(%v), applying lightning "+
+					"network topology update", failure.Code())
+				s.cfg.UpdateTopology(update)
+			}
+
 			userErr = errors.New(failure.Code())
 		}