From bf05e4778046643d55739a755be175ed9e9402fe Mon Sep 17 00:00:00 2001
From: Olaoluwa Osuntokun <laolu32@gmail.com>
Date: Tue, 30 Jan 2018 20:41:27 -0800
Subject: [PATCH] discovery: add additional gossiper level reject cache
MIME-Version: 1.0
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In this commit, we’ll add a new reject cache to ensure that we don’t
attempt to re-process any announcements already rejected by the
ChannelRouter.
---
 discovery/gossiper.go | 52 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/discovery/gossiper.go b/discovery/gossiper.go
index 5d722caf..64dee356 100644
--- a/discovery/gossiper.go
+++ b/discovery/gossiper.go
@@ -193,6 +193,9 @@ type AuthenticatedGossiper struct {
 	// consistent between when the DB is first read until it's written.
 	channelMtx *multimutex.Mutex
 
+	rejectMtx     sync.RWMutex
+	recentRejects map[uint64]struct{}
+
 	sync.Mutex
 }
 
@@ -214,6 +217,7 @@ func New(cfg Config, selfKey *btcec.PublicKey) (*AuthenticatedGossiper, error) {
 		prematureChannelUpdates: make(map[uint64][]*networkMsg),
 		waitingProofs:           storage,
 		channelMtx:              multimutex.NewMutex(),
+		recentRejects:           make(map[uint64]struct{}),
 	}, nil
 }
 
@@ -890,6 +894,13 @@ func (d *AuthenticatedGossiper) networkHandler() {
 				continue
 			}
 
+			// If this message was recently rejected, then we won't
+			// attempt to re-process it.
+			if d.isRecentlyRejectedMsg(announcement.msg) {
+				announcement.err <- fmt.Errorf("recently rejected")
+				continue
+			}
+
 			// We'll set up any dependent, and wait until a free
 			// slot for this job opens up, this allow us to not
 			// have thousands of goroutines active.
@@ -1014,6 +1025,26 @@ func (d *AuthenticatedGossiper) networkHandler() {
 	}
 }
 
+// isRecentlyRejectedMsg returns true if we recently rejected a message, and
+// false otherwise, This avoids expensive reprocessing of the message.
+func (d *AuthenticatedGossiper) isRecentlyRejectedMsg(msg lnwire.Message) bool {
+	d.rejectMtx.RLock()
+	defer d.rejectMtx.RUnlock()
+
+	switch m := msg.(type) {
+	case *lnwire.ChannelUpdate:
+		_, ok := d.recentRejects[m.ShortChannelID.ToUint64()]
+		return ok
+
+	case *lnwire.ChannelAnnouncement:
+		_, ok := d.recentRejects[m.ShortChannelID.ToUint64()]
+		return ok
+
+	default:
+		return false
+	}
+}
+
 // retransmitStaleChannels examines all outgoing channels that the source node
 // is known to maintain to check to see if any of them are "stale". A channel
 // is stale iff, the last timestamp of its rebroadcast is older then
@@ -1325,6 +1356,9 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(nMsg *networkMsg) []n
 			log.Error("Ignoring ChannelAnnouncement from "+
 				"chain=%v, gossiper on chain=%v", msg.ChainHash,
 				d.cfg.ChainHash)
+			d.rejectMtx.Lock()
+			d.recentRejects[msg.ShortChannelID.ToUint64()] = struct{}{}
+			d.rejectMtx.Unlock()
 			return nil
 		}
 
@@ -1356,6 +1390,9 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(nMsg *networkMsg) []n
 			if err := ValidateChannelAnn(msg); err != nil {
 				err := errors.Errorf("unable to validate "+
 					"announcement: %v", err)
+				d.rejectMtx.Lock()
+				d.recentRejects[msg.ShortChannelID.ToUint64()] = struct{}{}
+				d.rejectMtx.Unlock()
 
 				log.Error(err)
 				nMsg.err <- err
@@ -1416,6 +1453,9 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(nMsg *networkMsg) []n
 				// see if we get any new announcements.
 				anns, rErr := d.processRejectedEdge(msg, proof)
 				if rErr != nil {
+					d.rejectMtx.Lock()
+					d.recentRejects[msg.ShortChannelID.ToUint64()] = struct{}{}
+					d.rejectMtx.Unlock()
 					nMsg.err <- rErr
 					return nil
 				}
@@ -1517,6 +1557,9 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(nMsg *networkMsg) []n
 			log.Error("Ignoring ChannelUpdate from "+
 				"chain=%v, gossiper on chain=%v", msg.ChainHash,
 				d.cfg.ChainHash)
+			d.rejectMtx.Lock()
+			d.recentRejects[msg.ShortChannelID.ToUint64()] = struct{}{}
+			d.rejectMtx.Unlock()
 			return nil
 		}
 
@@ -1590,6 +1633,10 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(nMsg *networkMsg) []n
 					shortChanID, err)
 				log.Error(err)
 				nMsg.err <- err
+
+				d.rejectMtx.Lock()
+				d.recentRejects[msg.ShortChannelID.ToUint64()] = struct{}{}
+				d.rejectMtx.Unlock()
 				return nil
 			}
 		}
@@ -1633,6 +1680,9 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(nMsg *networkMsg) []n
 			if routing.IsError(err, routing.ErrOutdated, routing.ErrIgnored) {
 				log.Debug(err)
 			} else {
+				d.rejectMtx.Lock()
+				d.recentRejects[msg.ShortChannelID.ToUint64()] = struct{}{}
+				d.rejectMtx.Unlock()
 				log.Error(err)
 			}
 
@@ -1808,7 +1858,7 @@ func (d *AuthenticatedGossiper) processNetworkAnnouncement(nMsg *networkMsg) []n
 						chanInfo.AuthProof, chanInfo, e1, e2,
 					)
 					if err != nil {
-						log.Error("unable to gen ann: %v", err)
+						log.Errorf("unable to gen ann: %v", err)
 						return
 					}
 					err = d.cfg.SendToPeer(nMsg.peer, chanAnn)