From 1098aef26a2018853dfd6d217ab7f950f9fab379 Mon Sep 17 00:00:00 2001
From: Felix Lange <fjl@twurst.com>
Date: Fri, 18 Oct 2019 12:18:26 +0200
Subject: [PATCH] cmd/devp2p: improve crawl timestamp handling

---
 cmd/devp2p/crawl.go      | 28 +++++++++++++++-------------
 cmd/devp2p/nodeset.go    | 18 ++++++++++++------
 cmd/devp2p/nodesetcmd.go |  2 +-
 3 files changed, 28 insertions(+), 20 deletions(-)

diff --git a/cmd/devp2p/crawl.go b/cmd/devp2p/crawl.go
index ae14425503..27755f0d00 100644
--- a/cmd/devp2p/crawl.go
+++ b/cmd/devp2p/crawl.go
@@ -111,38 +111,40 @@ func (c *crawler) runIterator(done chan<- enode.Iterator, it enode.Iterator) {
 }
 
 func (c *crawler) updateNode(n *enode.Node) {
-	existing, ok := c.output[n.ID()]
+	node, ok := c.output[n.ID()]
 
 	// Skip validation of recently-seen nodes.
-	if ok && time.Since(existing.LastSeen) < c.revalidateInterval {
+	if ok && time.Since(node.LastCheck) < c.revalidateInterval {
 		return
 	}
 
 	// Request the node record.
 	nn, err := c.disc.RequestENR(n)
+	node.LastCheck = truncNow()
 	if err != nil {
-		if existing.Checks == 0 {
+		if node.Score == 0 {
+			// Node doesn't implement EIP-868.
 			log.Debug("Skipping node", "id", n.ID())
 			return
 		}
-		existing.Checks /= 2
+		node.Score /= 2
 	} else {
-		if !ok {
-			existing.FirstSeen = truncNow()
+		node.N = nn
+		node.Seq = nn.Seq()
+		node.Score++
+		if node.FirstResponse.IsZero() {
+			node.FirstResponse = node.LastCheck
 		}
-		existing.N = nn
-		existing.Seq = nn.Seq()
-		existing.LastSeen = truncNow()
-		existing.Checks++
+		node.LastResponse = node.LastCheck
 	}
 
 	// Store/update node in output set.
-	if existing.Checks <= 0 {
+	if node.Score <= 0 {
 		log.Info("Removing node", "id", n.ID())
 		delete(c.output, n.ID())
 	} else {
-		log.Info("Updating node", "id", n.ID(), "seq", existing.Seq, "checks", existing.Checks)
-		c.output[n.ID()] = existing
+		log.Info("Updating node", "id", n.ID(), "seq", n.Seq(), "score", node.Score)
+		c.output[n.ID()] = node
 	}
 }
 
diff --git a/cmd/devp2p/nodeset.go b/cmd/devp2p/nodeset.go
index 94177c53eb..2d86c3f65a 100644
--- a/cmd/devp2p/nodeset.go
+++ b/cmd/devp2p/nodeset.go
@@ -36,11 +36,17 @@ const jsonIndent = "    "
 type nodeSet map[enode.ID]nodeJSON
 
 type nodeJSON struct {
-	Seq       uint64      `json:"seq"`
-	N         *enode.Node `json:"record"`
-	FirstSeen time.Time   `json:"firstSeen,omitempty"`
-	LastSeen  time.Time   `json:"lastSeen,omitempty"`
-	Checks    int         `json:"checks"`
+	Seq uint64      `json:"seq"`
+	N   *enode.Node `json:"record"`
+
+	// The score tracks how many liveness checks were performed. It is incremented by one
+	// every time the node passes a check, and halved every time it doesn't.
+	Score int `json:"score,omitempty"`
+	// These two track the time of last successful contact.
+	FirstResponse time.Time `json:"firstResponse,omitempty"`
+	LastResponse  time.Time `json:"lastResponse,omitempty"`
+	// This one tracks the time of our last attempt to contact the node.
+	LastCheck time.Time `json:"lastCheck,omitempty"`
 }
 
 func loadNodesJSON(file string) nodeSet {
@@ -79,7 +85,7 @@ func (ns nodeSet) nodes() []*enode.Node {
 
 func (ns nodeSet) add(nodes ...*enode.Node) {
 	for _, n := range nodes {
-		ns[n.ID()] = nodeJSON{Seq: n.Seq(), N: n, FirstSeen: truncNow()}
+		ns[n.ID()] = nodeJSON{Seq: n.Seq(), N: n}
 	}
 }
 
diff --git a/cmd/devp2p/nodesetcmd.go b/cmd/devp2p/nodesetcmd.go
index 5fc065946b..802cedf086 100644
--- a/cmd/devp2p/nodesetcmd.go
+++ b/cmd/devp2p/nodesetcmd.go
@@ -148,7 +148,7 @@ func minAgeFilter(args []string) (nodeFilter, error) {
 		return nil, err
 	}
 	f := func(n nodeJSON) bool {
-		age := n.LastSeen.Sub(n.FirstSeen)
+		age := n.LastResponse.Sub(n.FirstResponse)
 		return age >= minage
 	}
 	return f, nil