fix: teardown removes the lease file the daemon writes

cmd/adopt.go

@@ -84,6 +84,7 @@ func runAdopt(cmd *cobra.Command, _ []string) error {
 		fmt.Printf("  gateway:         %s\n", gateway)
 		fmt.Printf("  primary-nic:     %s\n", primaryNIC)
 		fmt.Printf("  secondary-nics:  %s\n", strings.Join(secondaryNICs, ","))
+		fmt.Printf("  enis:            %s\n", cmp.Or(strings.Join(eniIDs, ","), "none"))
 		if len(ips) > 0 {
 			fmt.Printf("  pool-size:       %d (first=%s, last=%s)\n", len(ips), ips[0], ips[len(ips)-1])
 		} else {

cmd/daemon.go

@@ -24,7 +24,6 @@ import (
 )
 
 const (
-	defaultLeaseFile     = "/var/lib/cocoon/net/leases.json"
 	defaultControlSocket = "/run/cocoon-net/control.sock"
 	defaultMetricsAddr   = ":9092"
 
@@ -52,7 +51,7 @@ they expire.`,
 		RunE: runDaemon,
 	}
 	cmd.Flags().StringVar(&flagStateDir, "state-dir", defaultStateDir, "directory containing pool.json")
-	cmd.Flags().StringVar(&flagLeaseFile, "lease-file", defaultLeaseFile, "path to lease persistence file")
+	cmd.Flags().StringVar(&flagLeaseFile, "lease-file", "", "lease persistence file (default <state-dir>/leases.json)")
 	cmd.Flags().StringVar(&flagControlSocket, "control-socket", cmp.Or(os.Getenv("COCOON_NET_CONTROL_SOCKET"), defaultControlSocket), "root-only Unix socket for local lease lifecycle operations (empty to disable)")
 	cmd.Flags().BoolVar(&flagSkipIPTables, "skip-iptables", false, "skip iptables setup (for pre-configured nodes)")
 	cmd.Flags().StringVar(&flagMetricsAddr, "metrics-addr", cmp.Or(os.Getenv("COCOON_NET_METRICS_ADDR"), defaultMetricsAddr), "prometheus metrics listen address (empty to disable)")
@@ -109,7 +108,7 @@ func runDaemon(cmd *cobra.Command, _ []string) error {
 		Gateway:       gateway,
 		SubnetMask:    ipNet.Mask,
 		DNSServers:    dnsIPs,
-		LeaseFile:     flagLeaseFile,
+		LeaseFile:     resolveLeaseFile(),
 		ControlSocket: flagControlSocket,
 	}, poolIPs)
 

cmd/teardown.go

@@ -14,8 +14,6 @@ import (
 	"github.com/cocoonstack/cocoon-net/platform"
 )
 
-const leaseFileName = "leases.json"
-
 func newTeardownCmd() *cobra.Command {
 	cmd := &cobra.Command{
 		Use:   "teardown",

cmd/utils.go

@@ -1,9 +1,11 @@
 package cmd
 
 import (
+	"cmp"
 	"context"
 	"fmt"
 	"net"
+	"path/filepath"
 	"slices"
 	"strings"
 
@@ -13,7 +15,10 @@ import (
 	"github.com/cocoonstack/cocoon-net/pool"
 )
 
-const defaultStateDir = "/var/lib/cocoon/net"
+const (
+	defaultStateDir = "/var/lib/cocoon/net"
+	leaseFileName   = "leases.json"
+)
 
 var (
 	flagPlatform     string
@@ -38,7 +43,7 @@ func registerCommonFlags(cmd *cobra.Command, defaultPoolSize int) {
 	cmd.Flags().StringVar(&flagSubnet, "subnet", "", "VM subnet CIDR, e.g. 172.20.100.0/24 (required)")
 	cmd.Flags().IntVar(&flagPoolSize, "pool-size", defaultPoolSize, "number of IPs in the pool")
 	cmd.Flags().StringVar(&flagGateway, "gateway", "", "gateway IP on cni0 (default: first IP in subnet)")
-	cmd.Flags().StringVar(&flagPrimaryNIC, "primary-nic", "", "host primary NIC (auto-detect if empty)")
+	cmd.Flags().StringVar(&flagPrimaryNIC, "primary-nic", "", "host primary NIC (default: eth0 on volcengine, ens4 otherwise)")
 	cmd.Flags().StringVar(&flagDNS, "dns", "8.8.8.8,1.1.1.1", "comma-separated DNS servers for DHCP clients")
 	cmd.Flags().StringVar(&flagStateDir, "state-dir", defaultStateDir, "state directory")
 	cmd.Flags().BoolVar(&flagDryRun, "dry-run", false, "show what would be done without making changes")
@@ -91,6 +96,10 @@ func resolveSubnet() error {
 	return nil
 }
 
+func resolveLeaseFile() string {
+	return cmp.Or(flagLeaseFile, filepath.Join(flagStateDir, leaseFileName))
+}
+
 func splitTrim(s, sep string) []string {
 	parts := strings.Split(s, sep)
 	for i := range parts {

cmd/utils_test.go

@@ -61,3 +61,24 @@ func TestResolveSubnet(t *testing.T) {
 		})
 	}
 }
+
+func TestResolveLeaseFile(t *testing.T) {
+	tests := []struct {
+		name      string
+		stateDir  string
+		leaseFile string
+		want      string
+	}{
+		{"default state dir", defaultStateDir, "", "/var/lib/cocoon/net/leases.json"},
+		{"custom state dir", "/srv/cocoon/net", "", "/srv/cocoon/net/leases.json"},
+		{"explicit lease file wins", "/srv/cocoon/net", "/run/cocoon/leases.json", "/run/cocoon/leases.json"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			flagStateDir, flagLeaseFile = tt.stateDir, tt.leaseFile
+			if got := resolveLeaseFile(); got != tt.want {
+				t.Errorf("resolveLeaseFile() = %q, want %q", got, tt.want)
+			}
+		})
+	}
+}

docs/configuration.md

@@ -16,7 +16,7 @@ variables below; runtime state (what was provisioned, and for whom) lives in
 | `--primary-nic` | `eth0` (Volcengine) / `ens4` (other platforms) | Host primary NIC |
 | `--dns` | `8.8.8.8,1.1.1.1` | DNS servers for DHCP clients |
 | `--state-dir` | `/var/lib/cocoon/net` | State directory for `pool.json` |
-| `--lease-file` | `/var/lib/cocoon/net/leases.json` (independent of `--state-dir`) | (daemon) DHCP lease persistence file |
+| `--lease-file` | `<state-dir>/leases.json` | (daemon) DHCP lease persistence file |
 | `--control-socket` | `/run/cocoon-net/control.sock` | (daemon) Root-only Unix socket used by local VM lifecycle managers to reclaim leases; empty to disable |
 | `--drop-cidr` | none | (repeatable, `init`/`adopt`) Destination CIDR to DROP at `FORWARD` for VM traffic -- see [DHCP: traffic isolation](dhcp.md#traffic-isolation) |
 | `--drop-internal-access` | `false` | (`init`/`adopt`) DROP `FORWARD` traffic within the node's own `--subnet` |

docs/dhcp.md

@@ -25,7 +25,7 @@ VPC-routable IP directly from this server.
   `204` after a successful or already-completed release, `400` for an invalid
   MAC, and `500` when persistence fails; callers may safely retry a `500`.
 - Leases are persisted to the `--lease-file` (default
-  `/var/lib/cocoon/net/leases.json`) on every allocation/release, and
+  `<state-dir>/leases.json`) on every allocation/release, and
   reloaded at daemon startup so a restart doesn't strand or double-assign
   leases.
 

platform/ip_test.go

@@ -45,7 +45,6 @@ func TestSubnetIPs_Slash24SkipsBroadcast(t *testing.T) {
 func TestSubnetIPs_Slash28(t *testing.T) {
 	t.Parallel()
 
-	// /28 has 16 addresses, 14 hosts, minus gateway = 13.
 	got, err := SubnetIPs("192.168.10.0/28", "192.168.10.1", 32)
 	if err != nil {
 		t.Fatalf("SubnetIPs: %v", err)

platform/volcengine/adopt.go

@@ -6,4 +6,5 @@ import (
 	"github.com/cocoonstack/cocoon-net/platform"
 )
 
+// Adopt is a no-op: the VPC routes the VM subnet to the secondary ENIs, so no host route hijacks it.
 func (v *Volcengine) Adopt(context.Context, *platform.Config) error { return nil }