htlcswitch: move packet failure to mailbox

This commit moves the current logic for sending failures out of the link
and into the mailbox in preparation for our failing delayed htlcs. We do
so because the mailbox may need to fail packets while the link is
offline, and needs to be able to complete the task without member
methods on the link.

htlcswitch/switch.go

@@ -283,12 +283,11 @@ func New(cfg Config, currentHeight uint32) (*Switch, error) {
 		return nil, err
 	}
 
-	return &Switch{
+	s := &Switch{
 		bestHeight:        currentHeight,
 		cfg:               &cfg,
 		circuits:          circuitMap,
 		linkIndex:         make(map[lnwire.ChannelID]ChannelLink),
-		mailOrchestrator:  newMailOrchestrator(),
 		forwardingIndex:   make(map[lnwire.ShortChannelID]ChannelLink),
 		interfaceIndex:    make(map[[33]byte]map[lnwire.ChannelID]ChannelLink),
 		pendingLinkIndex:  make(map[lnwire.ChannelID]ChannelLink),
@@ -297,7 +296,14 @@ func New(cfg Config, currentHeight uint32) (*Switch, error) {
 		chanCloseRequests: make(chan *ChanClose),
 		resolutionMsgs:    make(chan *resolutionMsg),
 		quit:              make(chan struct{}),
-	}, nil
+	}
+
+	s.mailOrchestrator = newMailOrchestrator(&mailOrchConfig{
+		fetchUpdate:    s.cfg.FetchLastChannelUpdate,
+		forwardPackets: s.ForwardPackets,
+	})
+
+	return s, nil
 }
 
 // resolutionMsg is a struct that wraps an existing ResolutionMsg with a done
@@ -2037,7 +2043,8 @@ func (s *Switch) AddLink(link ChannelLink) error {
 	// Get and attach the mailbox for this link, which buffers packets in
 	// case there packets that we tried to deliver while this link was
 	// offline.
-	mailbox := s.mailOrchestrator.GetOrCreateMailBox(chanID)
+	shortChanID := link.ShortChanID()
+	mailbox := s.mailOrchestrator.GetOrCreateMailBox(chanID, shortChanID)
 	link.AttachMailBox(mailbox)
 
 	if err := link.Start(); err != nil {
@@ -2045,7 +2052,6 @@ func (s *Switch) AddLink(link ChannelLink) error {
 		return err
 	}
 
-	shortChanID := link.ShortChanID()
 	if shortChanID == hop.Source {
 		log.Infof("Adding pending link chan_id=%v, short_chan_id=%v",
 			chanID, shortChanID)
@@ -2217,7 +2223,7 @@ func (s *Switch) UpdateShortChanID(chanID lnwire.ChannelID) error {
 
 	// Finally, alert the mail orchestrator to the change of short channel
 	// ID, and deliver any unclaimed packets to the link.
-	mailbox := s.mailOrchestrator.GetOrCreateMailBox(chanID)
+	mailbox := s.mailOrchestrator.GetOrCreateMailBox(chanID, shortChanID)
 	s.mailOrchestrator.BindLiveShortChanID(
 		mailbox, chanID, shortChanID,
 	)