channeldb+routing+discovery: reject zombie announcements #2777

wpaulino · 2019-03-13T23:30:46Z

In this PR, we introduce a new persistent index for zombie edges to quickly reject announcements for edges we've previously deemed as zombies. Care has been taken to ensure we don't reject fresh updates for edges we've considered zombies.

channeldb/graph.go

discovery/gossiper.go

routing/router.go

Roasbeef

Excited to finally exterminate the Zombies in a permanent manner....LOK TAR OGAR!!!! ✊🏾

Solid set of changes, completed first pass and will start testing on various nodes. No major comments other than the sig validation and node pruning comments you'll find in-line.

channeldb/graph.go

Roasbeef · 2019-03-20T03:30:01Z

routing/router.go

+	MarkEdgeLive(chanID lnwire.ShortChannelID) error
+
+	// IsZombieEdge returns whether the edge is considered zombie.
+	IsZombieEdge(chanID lnwire.ShortChannelID) bool


This interface is getting a bit thicc...in the future I think we should slim it unbundle it a bit by breaking it into distinct interfaces that have very narrow purposes. As is now, many of the callers that accept this interface don't use most of the methods they're forced to know about.

Slimmed it down a bit since the gossiper now only requires knowing of MarkEdgeLive.

routing/router.go

discovery/gossiper.go

Roasbeef · 2019-03-20T03:52:55Z

discovery/gossiper_test.go

+	case <-time.After(2 * trickleDelay):
+	}
+
+	time.Sleep(time.Second)


Why's this sleep needed? Perhaps we should instead return to the caller immediately even if we get an update for an ann we don't know of.

Since we have to re-process it, if we return to the caller immediately then they won't be informed of any errors that occurred while re-processing it. Turns out the sleep wasn't needed though.

Roasbeef · 2019-03-20T04:05:20Z

routing/router.go

+				"as zombie: %v", chanToPrune.ChannelPoint, err)
+		}
+
+		err = r.cfg.Graph.DeleteChannelEdge(&chanToPrune.ChannelPoint)


Perhaps we should combine both operations into a single call? If we do, then this means that someone can't give us a super old channel and make us re-scan the graph with GetUTXO or the like.

yeah the more i think about this, i think its a good idea to have the transition from live -> zombie be atomic

Good point! Fixed.

Roasbeef · 2019-03-20T04:06:33Z

routing/router.go

+	// channels from the graph based on their spentness, but whether they
+	// are considered zombies or not.
+	if r.cfg.AssumeChannelValid {
+		if err := r.pruneZombieChans(); err != nil {


This skips calling PruneGraphNodes.

Will be including these changes in another PR.

wpaulino · 2019-03-26T06:05:04Z

Comments addressed, PTAL @cfromknecht @Roasbeef.

cfromknecht · 2019-03-27T00:10:42Z

routing/ann_validation.go

 	if err != nil {
-		return errors.Errorf("unable to reconstruct message: %v", err)


👍 one day, we will kill go-errors

cfromknecht

LGTM, will begin testing this on my node 🔥

channeldb/graph.go

halseth

💀🔫

channeldb/graph.go

routing/router.go

discovery/gossiper.go

discovery/gossiper_test.go

In this commit, we add a zombie edge index to the database. This allows us to quickly determine across restarts whether we're attempting to process an edge we've previously deemed as zombie.

We mark the edges as zombies when pruning them to ensure we don't attempt to reprocess them later on. This also applies to channels that have been removed from the graph due to being stale.

In this commit, we extend the graph's FetchChannelEdgesByID and HasChannelEdge methods to also check the zombie index whenever the edge to be looked up doesn't exist within the edge index. We do this to signal to callers that the edge is known, but only as a zombie, and the only information that we have about the edge are the node public keys of the two parties involved in the edge. In the event that an edge does exist within the zombie index, we make an additional check on edge policies to ensure they are not within the router's pruning window, indicating that it is a fresh update.

In this commit, we leverage the recently introduced zombie edge index to quickly reject announcements for edges we've previously deemed as zombies. Care has been taken to ensure we don't reject fresh updates for edges we've considered zombies.

cfromknecht · 2019-03-27T22:18:11Z

discovery/gossiper.go

+			// signed by the correct party. The least-significant
+			// bit in the flag on the channel update tells us which
+			// edge is being updated.
+			var pubKey *btcec.PublicKey


not a blocker, just noting that this same block of code exists in many places w/in the code base. would be great to have a method like

func (c *ChannelEdgeInfo) DirectionKey(flags lnwire.ChannelFlags) *btcec.PublicKey

Roasbeef

LGTM 🎎

Roasbeef · 2019-03-27T23:52:28Z

channeldb/graph.go

 			return nil
 		}

 		exists = true
+		isZombie = false


Non blocking nit: not actually needed since the default value of a bool is false.

halseth · 2019-03-28T09:50:39Z

discovery/gossiper.go

+				"graph(shortChanID=%v), saving for "+
+				"reprocessing later", shortChanID)
+
+			// NOTE: We don't return anything on the error channel


Can this potentially cause the gossiper to deadlock if the announcement never comes through? 🤔

No because we return. The errChan in which we're sending the error back is given to the caller.

Was just wondering who waits for the value on the channel, but looks like we never actually read it for remote annonucements...

wpaulino added this to the 0.6 milestone Mar 14, 2019

wpaulino added enhancement Improvements to existing features / behaviour database Related to the database/storage of LND graph P2 should be fixed if one has time gossip labels Mar 14, 2019

cfromknecht reviewed Mar 16, 2019

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wpaulino force-pushed the reject-zombie-anns branch 2 times, most recently from d0233f8 to b389ade Compare March 18, 2019 21:05

halseth mentioned this pull request Mar 19, 2019

router: Optimize pruning zombie channels. #2799

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wpaulino force-pushed the reject-zombie-anns branch from b389ade to a062952 Compare March 20, 2019 00:01

Roasbeef requested changes Mar 20, 2019

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wpaulino force-pushed the reject-zombie-anns branch 3 times, most recently from 89eb9bd to baae58d Compare March 26, 2019 05:39

wpaulino force-pushed the reject-zombie-anns branch from baae58d to d9f0cfc Compare March 26, 2019 23:49

cfromknecht reviewed Mar 27, 2019

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cfromknecht approved these changes Mar 27, 2019

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wpaulino force-pushed the reject-zombie-anns branch 3 times, most recently from 4bf9074 to 53ddc24 Compare March 27, 2019 00:57

Roasbeef reviewed Mar 27, 2019

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channeldb/graph.go Show resolved Hide resolved

wpaulino force-pushed the reject-zombie-anns branch 2 times, most recently from f496d0a to a9b85d1 Compare March 27, 2019 02:34

halseth suggested changes Mar 27, 2019

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wpaulino added 4 commits March 27, 2019 13:05

channeldb: remove unused buckets

a26a643

channeldb: add zombie edge index

b780dfa

In this commit, we add a zombie edge index to the database. This allows us to quickly determine across restarts whether we're attempting to process an edge we've previously deemed as zombie.

channeldb: extend DeleteChannelEdge to mark edge as zombie

e98f4d6

We mark the edges as zombies when pruning them to ensure we don't attempt to reprocess them later on. This also applies to channels that have been removed from the graph due to being stale.

wpaulino added 4 commits March 27, 2019 13:07

routing+server: expose DefaultChannelPruneExpiry

174645f

routing+discovery: extend ChannelGraphSource with zombie index methods

23796d3

routing: expose VerifyChannelUpdateSignature function

44a01db

wpaulino force-pushed the reject-zombie-anns branch from a9b85d1 to 5cec451 Compare March 27, 2019 20:08

cfromknecht reviewed Mar 27, 2019

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Roasbeef approved these changes Mar 28, 2019

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Roasbeef merged commit 43ba4a5 into lightningnetwork:master Mar 28, 2019

wpaulino deleted the reject-zombie-anns branch March 28, 2019 02:23

halseth reviewed Mar 28, 2019

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channeldb+routing+discovery: reject zombie announcements #2777

channeldb+routing+discovery: reject zombie announcements #2777

wpaulino commented Mar 13, 2019

Roasbeef left a comment

Roasbeef Mar 20, 2019

wpaulino Mar 26, 2019

Roasbeef Mar 20, 2019

wpaulino Mar 26, 2019

Roasbeef Mar 20, 2019

cfromknecht Mar 23, 2019

wpaulino Mar 26, 2019

Roasbeef Mar 20, 2019

wpaulino Mar 26, 2019

wpaulino commented Mar 26, 2019

cfromknecht Mar 27, 2019

cfromknecht left a comment

halseth left a comment

cfromknecht Mar 27, 2019

Roasbeef left a comment

Roasbeef Mar 27, 2019

halseth Mar 28, 2019

wpaulino Mar 28, 2019

halseth Apr 1, 2019

		if err != nil {
		return errors.Errorf("unable to reconstruct message: %v", err)

channeldb+routing+discovery: reject zombie announcements #2777

channeldb+routing+discovery: reject zombie announcements #2777

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wpaulino commented Mar 13, 2019

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