routing: add support for detection+processing of premature announcements
This commit fixes a prior block propagation race-condition by detecting and properly processing “premature” announcements. A premature announcement is one that’s received with an anchored block height which is beyond our chain tip. Once received, we now store these announcements in a special map that’s caches them in memory. Once a new block arrives, we check the map for the existence of any entries, processing them as normal if so.
This commit is contained in:
Olaoluwa Osuntokun
parent
2c0d5e0f0d
commit
9cef2f8657
@ -96,8 +96,13 @@ type Config struct {
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type ChannelRouter struct {
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sync.RWMutex
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// cfg is a copy of the configuration struct that the ChannelRouter was
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// initialized with.
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cfg *Config
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// selfNode is the center of the star-graph centered around the
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// ChannelRouter. The ChannelRouter uses this node as a starting point
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// when doing any path finding.
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selfNode *channeldb.LightningNode
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// TODO(roasbeef): make LRU, invalidate upon new block connect
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@ -105,12 +110,31 @@ type ChannelRouter struct {
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nodeCache map[[33]byte]*channeldb.LightningNode
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edgeCache map[wire.OutPoint]*channeldb.ChannelEdge
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// newBlocks is a channel in which new blocks connected to the end of
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// the main chain are sent over.
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newBlocks chan *chainntnfs.BlockEpoch
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// networkMsgs is a channel that carries new network messages from
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// outside the ChannelRouter to be processed by the networkHandler.
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networkMsgs chan *routingMsg
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// syncRequests is a channel that carries requests to synchronize newly
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// connected peers to the state of the channel graph from our PoV.
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syncRequests chan *syncRequest
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// prematureAnnouncements maps a blockheight to a set of announcements
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// which are "premature" from our PoV. An announcement is premature if
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// it claims to be anchored in a block which is beyond the current
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// mainchain tip as we know it. Premature announcements will be
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// processed once the chain tip as we know it extends to/past the
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// premature height.
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// TODO(roasbeef): limit premature announcements to N
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prematureAnnouncements map[uint32][]lnwire.Message
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// bestHeight is the height of the block at the tip of the main chain
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// as we know it.
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bestHeight uint32
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fakeSig *btcec.Signature
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started uint32
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@ -150,6 +174,7 @@ func New(cfg Config) (*ChannelRouter, error) {
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fakeSig: fakeSig,
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networkMsgs: make(chan *routingMsg),
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syncRequests: make(chan *syncRequest),
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prematureAnnouncements: make(map[uint32][]lnwire.Message),
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quit: make(chan struct{}),
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}, nil
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}
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@ -174,6 +199,12 @@ func (r *ChannelRouter) Start() error {
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}
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r.newBlocks = blockEpochs.Epochs
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_, height, err := r.cfg.Chain.GetBestBlock()
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if err != nil {
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return err
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}
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r.bestHeight = uint32(height)
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// Before we begin normal operation of the router, we first need to
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// synchronize the channel graph to the latest state of the UTXO set.
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if err := r.syncGraphWithChain(); err != nil {
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@ -304,6 +335,7 @@ func (r *ChannelRouter) networkHandler() {
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var announcementBatch []lnwire.Message
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// TODO(roasbeef): parametrize the above
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trickleTimer := time.NewTicker(time.Millisecond * 300)
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defer trickleTimer.Stop()
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@ -316,11 +348,8 @@ func (r *ChannelRouter) networkHandler() {
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// result we'll modify the channel graph accordingly depending
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// on the exact type of the message.
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case netMsg := <-r.networkMsgs:
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// TODO(roasbeef): this loop would mostly be moved to
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// the discovery service
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// Process the network announcement to determine if this
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// is either a new announcement from our PoV or an
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// Process the network announcement to determine if
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// this is either a new announcement from our PoV or an
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// update to a prior vertex/edge we previously
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// accepted.
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accepted := r.processNetworkAnnouncement(netMsg.msg)
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@ -345,15 +374,34 @@ func (r *ChannelRouter) networkHandler() {
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return
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}
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// Once a new block arrives, we update our running
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// track of the height of the chain tip.
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blockHeight := uint32(newBlock.Height)
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r.bestHeight = blockHeight
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// Next we check if we have any premature announcements
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// for this height, if so, then we process them once
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// more as normal announcements.
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prematureAnns := r.prematureAnnouncements[uint32(newBlock.Height)]
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log.Infof("Re-processing %v premature announcements for "+
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"height %v", len(prematureAnns), blockHeight)
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for _, ann := range prematureAnns {
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if ok := r.processNetworkAnnouncement(ann); ok {
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announcementBatch = append(announcementBatch, ann)
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}
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}
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delete(r.prematureAnnouncements, blockHeight)
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log.Infof("Pruning channel graph using block %v (height=%v)",
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newBlock.Hash, blockHeight)
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block, err := r.cfg.Chain.GetBlock(newBlock.Hash)
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if err != nil {
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log.Errorf("unable to get block: %v", err)
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continue
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}
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log.Infof("Pruning channel graph using block %v (height=%v)",
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newBlock.Hash, newBlock.Height)
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// We're only interested in all prior outputs that've
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// been spent in the block, so collate all the
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// referenced previous outpoints within each tx and
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@ -371,14 +419,14 @@ func (r *ChannelRouter) networkHandler() {
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// of the block being pruned so the prune tip can be
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// updated.
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numClosed, err := r.cfg.Graph.PruneGraph(spentOutputs,
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newBlock.Hash, uint32(newBlock.Height))
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newBlock.Hash, blockHeight)
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if err != nil {
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log.Errorf("unable to prune routing table: %v", err)
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continue
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}
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log.Infof("Block %v (height=%v) closed %v channels",
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newBlock.Hash, newBlock.Height, numClosed)
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newBlock.Hash, blockHeight, numClosed)
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// The retransmission timer has ticked which indicates that we
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// should broadcast our personal channel sot the network. This
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@ -481,9 +529,13 @@ func (r *ChannelRouter) networkHandler() {
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// channel or node announcement. If the update didn't affect the internal state
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// of the draft due to either being out of date, invalid, or redundant, then
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// false is returned. Otherwise, true is returned indicating that the caller
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// may want to batch this request to be broadcast to immediate peers during th
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// may want to batch this request to be broadcast to immediate peers during the
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// next announcement epoch.
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func (r *ChannelRouter) processNetworkAnnouncement(msg lnwire.Message) bool {
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isPremature := func(chanID *lnwire.ChannelID) bool {
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return chanID.BlockHeight > r.bestHeight
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}
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switch msg := msg.(type) {
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// A new node announcement has arrived which either presents a new
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@ -545,10 +597,22 @@ func (r *ChannelRouter) processNetworkAnnouncement(msg lnwire.Message) bool {
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return false
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}
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// TODO(roasbeef): check if height > then our known height and
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// wait for next epoch based on that?
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// * or add to "premature" announcement bucket
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// * bucket gets checked on each new incoming block
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// If the advertised inclusionary block is beyond our knowledge
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// of the chain tip, then we'll put the announcement in limbo
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// to be fully verified once we advance forward in the chain.
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if isPremature(&msg.ChannelID) {
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blockHeight := msg.ChannelID.BlockHeight
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log.Infof("Announcement for chan_id=(%v), is "+
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"premature: advertises height %v, only height "+
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"%v is known", channelID,
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msg.ChannelID.BlockHeight, r.bestHeight)
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r.prematureAnnouncements[blockHeight] = append(
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r.prematureAnnouncements[blockHeight],
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msg,
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)
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return false
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}
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// Before we can add the channel to the channel graph, we need
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// to obtain the full funding outpoint that's encoded within
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@ -597,6 +661,23 @@ func (r *ChannelRouter) processNetworkAnnouncement(msg lnwire.Message) bool {
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return false
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}
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// If the advertised inclusionary block is beyond our knowledge
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// of the chain tip, then we'll put the announcement in limbo
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// to be fully verified once we advance forward in the chain.
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if isPremature(&msg.ChannelID) {
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blockHeight := msg.ChannelID.BlockHeight
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log.Infof("Update announcement for chan_id=(%v), is "+
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"premature: advertises height %v, only height "+
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"%v is known", chanID, blockHeight,
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r.bestHeight)
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r.prematureAnnouncements[blockHeight] = append(
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r.prematureAnnouncements[blockHeight],
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msg,
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)
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return false
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}
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// As edges are directional edge node has a unique policy for
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// the direction of the edge they control. Therefore we first
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// check if we already have the most up to date information for
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