From 27560cf7a4dc5c8a1fed98f6bbe86898c1ca790f Mon Sep 17 00:00:00 2001
From: Sam Kleinman <garen@tychoish.com>
Date: Wed, 10 Nov 2021 10:52:18 -0500
Subject: [PATCH] p2p: reduce peer score for dial failures (#7265)

When dialing fails to succeed we should reduce the score of the peer,
which puts the peer at (potentially) greater chances of being removed
from the peer manager, and reduces the chance of the peer being
gossiped by the PEX reactor.
---
 CHANGELOG_PENDING.md        |  1 +
 internal/p2p/peermanager.go | 21 ++++++++++++++++++---
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/CHANGELOG_PENDING.md b/CHANGELOG_PENDING.md
index 70b361d26..08f53c6e0 100644
--- a/CHANGELOG_PENDING.md
+++ b/CHANGELOG_PENDING.md
@@ -23,6 +23,7 @@ Special thanks to external contributors on this release:
 - P2P Protocol
 
   - [p2p] \#7035 Remove legacy P2P routing implementation and associated configuration options. (@tychoish)
+  - [p2p] \#7265 Peer manager reduces peer score for each failed dial attempts for peers that have not successfully dialed. (@tychoish)
 
 - Go API
 
diff --git a/internal/p2p/peermanager.go b/internal/p2p/peermanager.go
index 7ccc0d59c..8c37cc1ff 100644
--- a/internal/p2p/peermanager.go
+++ b/internal/p2p/peermanager.go
@@ -532,6 +532,7 @@ func (m *PeerManager) DialFailed(address NodeAddress) error {
 	if !ok {
 		return nil // Assume the address has been removed, ignore.
 	}
+
 	addressInfo.LastDialFailure = time.Now().UTC()
 	addressInfo.DialFailures++
 	if err := m.store.Set(peer); err != nil {
@@ -602,6 +603,7 @@ func (m *PeerManager) Dialed(address NodeAddress) error {
 		addressInfo.LastDialSuccess = now
 		// If not found, assume address has been removed.
 	}
+
 	if err := m.store.Set(peer); err != nil {
 		return err
 	}
@@ -660,6 +662,11 @@ func (m *PeerManager) Accepted(peerID types.NodeID) error {
 		peer = m.newPeerInfo(peerID)
 	}
 
+	// reset this to avoid penalizing peers for their past transgressions
+	for _, addr := range peer.AddressInfo {
+		addr.DialFailures = 0
+	}
+
 	// If all connections slots are full, but we allow upgrades (and we checked
 	// above that we have upgrade capacity), then we can look for a lower-scored
 	// peer to replace and if found accept the connection anyway and evict it.
@@ -1287,15 +1294,23 @@ func (p *peerInfo) Score() PeerScore {
 		return PeerScorePersistent
 	}
 
-	if p.MutableScore <= 0 {
+	score := p.MutableScore
+
+	for _, addr := range p.AddressInfo {
+		// DialFailures is reset when dials succeed, so this
+		// is either the number of dial failures or 0.
+		score -= int64(addr.DialFailures)
+	}
+
+	if score <= 0 {
 		return 0
 	}
 
-	if p.MutableScore >= math.MaxUint8 {
+	if score >= math.MaxUint8 {
 		return PeerScore(math.MaxUint8)
 	}
 
-	return PeerScore(p.MutableScore)
+	return PeerScore(score)
 }
 
 // Validate validates the peer info.