Merge pull request #4352 from matheusdtech/discovery-lock-premature

discovery: correctly lock premature messages

discovery/gossiper.go

@@ -6,7 +6,6 @@ import (
 	"fmt"
 	"runtime"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/btcsuite/btcd/btcec"
@@ -247,7 +246,8 @@ type AuthenticatedGossiper struct {
 	stopped sync.Once
 
 	// bestHeight is the height of the block at the tip of the main chain
-	// as we know it. To be used atomically.
+	// as we know it. Accesses *MUST* be done with the gossiper's lock
+	// held.
 	bestHeight uint32
 
 	quit chan struct{}
@@ -1030,28 +1030,30 @@ func (d *AuthenticatedGossiper) networkHandler() {
 				return
 			}
 
-			// Once a new block arrives, we updates our running
+			// Once a new block arrives, we update our running
 			// track of the height of the chain tip.
+			d.Lock()
 			blockHeight := uint32(newBlock.Height)
-			atomic.StoreUint32(&d.bestHeight, blockHeight)
+			d.bestHeight = blockHeight
+
+			log.Debugf("New block: height=%d, hash=%s", blockHeight,
+				newBlock.Hash)
 
 			// Next we check if we have any premature announcements
 			// for this height, if so, then we process them once
 			// more as normal announcements.
-			d.Lock()
-			numPremature := len(d.prematureAnnouncements[blockHeight])
-			d.Unlock()
-
-			// Return early if no announcement to process.
-			if numPremature == 0 {
+			premature := d.prematureAnnouncements[blockHeight]
+			if len(premature) == 0 {
+				d.Unlock()
 				continue
 			}
+			delete(d.prematureAnnouncements, blockHeight)
+			d.Unlock()
 
 			log.Infof("Re-processing %v premature announcements "+
-				"for height %v", numPremature, blockHeight)
+				"for height %v", len(premature), blockHeight)
 
-			d.Lock()
-			for _, ann := range d.prematureAnnouncements[blockHeight] {
+			for _, ann := range premature {
 				emittedAnnouncements := d.processNetworkAnnouncement(ann)
 				if emittedAnnouncements != nil {
 					announcements.AddMsgs(
@@ -1059,8 +1061,6 @@ func (d *AuthenticatedGossiper) networkHandler() {
 					)
 				}
 			}
-			delete(d.prematureAnnouncements, blockHeight)
-			d.Unlock()
 
 		// The trickle timer has ticked, which indicates we should
 		// flush to the network the pending batch of new announcements
@@ -1491,11 +1491,11 @@ func (d *AuthenticatedGossiper) addNode(msg *lnwire.NodeAnnouncement) error {
 func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 	nMsg *networkMsg) []networkMsg {
 
+	// isPremature *MUST* be called with the gossiper's lock held.
 	isPremature := func(chanID lnwire.ShortChannelID, delta uint32) bool {
 		// TODO(roasbeef) make height delta 6
 		//  * or configurable
-		bestHeight := atomic.LoadUint32(&d.bestHeight)
-		return chanID.BlockHeight+delta > bestHeight
+		return chanID.BlockHeight+delta > d.bestHeight
 	}
 
 	var announcements []networkMsg
@@ -1581,6 +1581,7 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 		// If the advertised inclusionary block is beyond our knowledge
 		// of the chain tip, then we'll put the announcement in limbo
 		// to be fully verified once we advance forward in the chain.
+		d.Lock()
 		if nMsg.isRemote && isPremature(msg.ShortChannelID, 0) {
 			blockHeight := msg.ShortChannelID.BlockHeight
 			log.Infof("Announcement for chan_id=(%v), is "+
@@ -1588,9 +1589,8 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 				"height %v is known",
 				msg.ShortChannelID.ToUint64(),
 				msg.ShortChannelID.BlockHeight,
-				atomic.LoadUint32(&d.bestHeight))
+				d.bestHeight)
 
-			d.Lock()
 			d.prematureAnnouncements[blockHeight] = append(
 				d.prematureAnnouncements[blockHeight],
 				nMsg,
@@ -1598,6 +1598,7 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 			d.Unlock()
 			return nil
 		}
+		d.Unlock()
 
 		// At this point, we'll now ask the router if this is a
 		// zombie/known edge. If so we can skip all the processing
@@ -1808,14 +1809,14 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 		// If the advertised inclusionary block is beyond our knowledge
 		// of the chain tip, then we'll put the announcement in limbo
 		// to be fully verified once we advance forward in the chain.
+		d.Lock()
 		if nMsg.isRemote && isPremature(msg.ShortChannelID, 0) {
 			log.Infof("Update announcement for "+
 				"short_chan_id(%v), is premature: advertises "+
 				"height %v, only height %v is known",
 				shortChanID, blockHeight,
-				atomic.LoadUint32(&d.bestHeight))
+				d.bestHeight)
 
-			d.Lock()
 			d.prematureAnnouncements[blockHeight] = append(
 				d.prematureAnnouncements[blockHeight],
 				nMsg,
@@ -1823,6 +1824,7 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 			d.Unlock()
 			return nil
 		}
+		d.Unlock()
 
 		// Before we perform any of the expensive checks below, we'll
 		// check whether this update is stale or is for a zombie
@@ -2058,19 +2060,20 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(
 		// proof is premature.  If so we'll halt processing until the
 		// expected announcement height.  This allows us to be tolerant
 		// to other clients if this constraint was changed.
+		d.Lock()
 		if isPremature(msg.ShortChannelID, d.cfg.ProofMatureDelta) {
-			d.Lock()
 			d.prematureAnnouncements[needBlockHeight] = append(
 				d.prematureAnnouncements[needBlockHeight],
 				nMsg,
 			)
-			d.Unlock()
 			log.Infof("Premature proof announcement, "+
 				"current block height lower than needed: %v <"+
 				" %v, add announcement to reprocessing batch",
-				atomic.LoadUint32(&d.bestHeight), needBlockHeight)
+				d.bestHeight, needBlockHeight)
+			d.Unlock()
 			return nil
 		}
+		d.Unlock()
 
 		// Ensure that we know of a channel with the target channel ID
 		// before proceeding further.