p2p: reduce peer score for dial failures (backport #7265) (#7271)

* 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.

(cherry picked from commit 27560cf7a4)

Co-authored-by: Sam Kleinman <garen@tychoish.com>

CHANGELOG_PENDING.md

@@ -16,6 +16,8 @@ Special thanks to external contributors on this release:
 
 - P2P Protocol
 
+  - [p2p] \#7265 Peer manager reduces peer score for each failed dial attempts for peers that have not successfully dialed. (@tychoish)
+
 - Go API
 
 - Blockchain Protocol

internal/p2p/peermanager.go

@@ -534,6 +534,7 @@ 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 {
@@ -604,6 +605,7 @@ 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
 	}
@@ -662,6 +664,11 @@ 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.
@@ -1289,15 +1296,23 @@ 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.