discovery: limit NumBlocks to best known height for outgoing QueryChannelRange

This is done to ensure we don't receive replies for channels in blocks
not currently known to us, which we wouldn't be able to process.

discovery/gossiper.go

@@ -343,16 +343,18 @@ func New(cfg Config, selfKey *btcec.PublicKey) *AuthenticatedGossiper {
 		channelMtx:              multimutex.NewMutex(),
 		recentRejects:           make(map[uint64]struct{}),
 		heightForLastChanUpdate: make(map[uint64][2]uint32),
-		syncMgr: newSyncManager(&SyncManagerCfg{
-			ChainHash:               cfg.ChainHash,
-			ChanSeries:              cfg.ChanSeries,
-			RotateTicker:            cfg.RotateTicker,
-			HistoricalSyncTicker:    cfg.HistoricalSyncTicker,
-			NumActiveSyncers:        cfg.NumActiveSyncers,
-			IgnoreHistoricalFilters: cfg.IgnoreHistoricalFilters,
-		}),
 	}
 
+	gossiper.syncMgr = newSyncManager(&SyncManagerCfg{
+		ChainHash:               cfg.ChainHash,
+		ChanSeries:              cfg.ChanSeries,
+		RotateTicker:            cfg.RotateTicker,
+		HistoricalSyncTicker:    cfg.HistoricalSyncTicker,
+		NumActiveSyncers:        cfg.NumActiveSyncers,
+		IgnoreHistoricalFilters: cfg.IgnoreHistoricalFilters,
+		BestHeight:              gossiper.latestHeight,
+	})
+
 	gossiper.reliableSender = newReliableSender(&reliableSenderCfg{
 		NotifyWhenOnline:  cfg.NotifyWhenOnline,
 		NotifyWhenOffline: cfg.NotifyWhenOffline,
@@ -2644,3 +2646,10 @@ func IsKeepAliveUpdate(update *lnwire.ChannelUpdate,
 	}
 	return true
 }
+
+// latestHeight returns the gossiper's latest height known of the chain.
+func (d *AuthenticatedGossiper) latestHeight() uint32 {
+	d.Lock()
+	defer d.Unlock()
+	return d.bestHeight
+}