fix(bootstrap): skip backup peer list when no bootstrap peers configured

CHANGELOG.md

@@ -29,6 +29,7 @@ The following emojis are used to highlight certain changes:
 ### Fixed
 
 - `gateway`: `X-Ipfs-Path` values no longer carry bytes that are invalid in an HTTP field value (Section 5.5 of RFC 9110). The header used to echo raw UnixFS file names, so non-ASCII paths arrived garbled or broke strict clients; when the header is enabled, it is now omitted for such paths, which only the percent-encoded `Ipfs-Uri` can carry. [#1209](https://github.com/ipfs/boxo/pull/1209)
+- `bootstrap`: the saved backup peer list is no longer dialed when no bootstrap peers are configured. [#1213](https://github.com/ipfs/boxo/pull/1213)
 
 ### Security
 

bootstrap/bootstrap.go

@@ -299,11 +299,17 @@ func bootstrapRound(ctx context.Context, host host.Host, cfg BootstrapConfig) er
 	// Retrieving them here makes sure we remain observant of changes to client configuration.
 	peers := cfg.BootstrapPeers()
 
-	if len(peers) > 0 {
-		numToDial -= int(peersConnect(ctx, host, peers, numToDial, true))
-		if numToDial <= 0 {
-			return nil
-		}
+	if len(peers) == 0 {
+		// The backup list is a fallback for when configured bootstrap peers
+		// are unreachable (ipfs/kubo#8856). With no configured peers there is
+		// nothing to fall back from.
+		log.Debugf("%s bootstrap skipped -- no bootstrap peers configured", id)
+		return nil
+	}
+
+	numToDial -= int(peersConnect(ctx, host, peers, numToDial, true))
+	if numToDial <= 0 {
+		return nil
 	}
 
 	if cfg.loadBackupBootstrapPeers == nil {

bootstrap/bootstrap_test.go

@@ -254,3 +254,77 @@ func TestHasCircuitProtocol(t *testing.T) {
 		})
 	}
 }
+
+// TestBootstrapRoundSkipsBackupWhenNoBootstrapPeers verifies that bootstrapRound
+// does not consult the backup peer list when no bootstrap peers are configured.
+// The backup list exists only as a recovery mechanism for when configured
+// bootstrap peers are down; with no configured peers there is nothing to
+// recover from, so dialing stale backup peers from previous runs would be
+// unwanted network traffic. See ipfs/kubo#11452.
+func TestBootstrapRoundSkipsBackupWhenNoBootstrapPeers(t *testing.T) {
+	backupCalled := false
+	loadFunc := func(_ context.Context) []peer.AddrInfo {
+		backupCalled = true
+		return nil
+	}
+	saveFunc := func(_ context.Context, _ []peer.AddrInfo) {}
+
+	bootCfg := BootstrapConfigWithPeers(nil, WithBackupPeers(loadFunc, saveFunc))
+	bootCfg.MinPeerThreshold = 2
+
+	priv, _, err := crypto.GenerateEd25519Key(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	p2pHost, err := libp2p.New(libp2p.Identity(priv))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = p2pHost.Close() })
+
+	if err := bootstrapRound(t.Context(), p2pHost, bootCfg); err != nil {
+		t.Fatalf("bootstrapRound returned error: %v", err)
+	}
+	if backupCalled {
+		t.Fatal("bootstrapRound consulted the backup peer list despite no bootstrap peers being configured")
+	}
+}
+
+// TestBootstrapRoundDialsBackupWhenBootstrapPeersPresent confirms the backup
+// list is still consulted when configured bootstrap peers fail to connect,
+// preserving the recovery mechanism from ipfs/kubo#8856.
+func TestBootstrapRoundDialsBackupWhenBootstrapPeersPresent(t *testing.T) {
+	backupCalled := false
+	loadFunc := func(_ context.Context) []peer.AddrInfo {
+		backupCalled = true
+		return nil
+	}
+	saveFunc := func(_ context.Context, _ []peer.AddrInfo) {}
+
+	// A fake, undialable bootstrap peer so peersConnect attempts and fails
+	// rather than short-circuiting on an empty list.
+	fakeID, err := test.RandPeerID()
+	if err != nil {
+		t.Fatal(err)
+	}
+	fakePeer := peer.AddrInfo{ID: fakeID}
+	bootCfg := BootstrapConfigWithPeers([]peer.AddrInfo{fakePeer}, WithBackupPeers(loadFunc, saveFunc))
+	bootCfg.MinPeerThreshold = 2
+	// Keep the round snappy: the dial will fail fast against a random peer ID.
+	bootCfg.ConnectionTimeout = 500 * time.Millisecond
+
+	priv, _, err := crypto.GenerateEd25519Key(rand.Reader)
+	if err != nil {
+		t.Fatal(err)
+	}
+	p2pHost, err := libp2p.New(libp2p.Identity(priv))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(func() { _ = p2pHost.Close() })
+
+	_ = bootstrapRound(t.Context(), p2pHost, bootCfg)
+	if !backupCalled {
+		t.Fatal("bootstrapRound did not consult the backup peer list despite configured bootstrap peers failing to connect")
+	}
+}