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fix(orchestrator): pin tap device host-side MAC address #3271

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Merged
rguliyev merged 2 commits into from
Jul 11, 2026
Merged

fix(orchestrator): pin tap device host-side MAC address #3271

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73e02dd
fix(orchestrator): pin tap device host-side MAC address
rguliyev Jul 11, 2026
ed2ae14
fix(orchestrator): parse tap host MAC once at package init
rguliyev Jul 11, 2026
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7 changes: 7 additions & 0 deletions packages/orchestrator/pkg/sandbox/network/network.go
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Original file line number Diff line number Diff line change
Expand Up @@ -214,6 +214,13 @@ func (s *Slot) CreateNetwork(ctx context.Context) (retErr error) {
return fmt.Errorf("error creating tap device: %w", err)
}

// Keep resumed guests' cached gateway ARP entries valid. Tap devices are
// isolated in per-sandbox network namespaces, so sharing this MAC is safe.
err = netlink.LinkSetHardwareAddr(tap, tapHostHardwareAddr)
if err != nil {
return fmt.Errorf("error setting tap device hardware address: %w", err)
}

err = netlink.LinkSetUp(tap)
if err != nil {
return fmt.Errorf("error setting tap device up: %w", err)
Expand Down
20 changes: 17 additions & 3 deletions packages/orchestrator/pkg/sandbox/network/slot.go
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Original file line number Diff line number Diff line change
Expand Up @@ -35,12 +35,14 @@ const (
tapInterfaceName = "tap0"
tapIp = "169.254.0.22"
tapMAC = "02:FC:00:00:00:05"
tapHostMAC = "02:FC:00:00:00:06"
)

var (
hostNetworkCIDR = getHostNetworkCIDR()
vrtNetworkCIDR = getVrtNetworkCIDR()
vrtSlotsSize = GetVrtSlotsSize()
hostNetworkCIDR = getHostNetworkCIDR()
vrtNetworkCIDR = getVrtNetworkCIDR()
vrtSlotsSize = GetVrtSlotsSize()
tapHostHardwareAddr = getTapHostHardwareAddr()
)

// Slot network allocation
Expand Down Expand Up @@ -390,6 +392,18 @@ func getHostNetworkCIDR() *net.IPNet {
return subnet
}

// getTapHostHardwareAddr parses the fixed tapHostMAC constant once at package
// init, so CreateNetwork doesn't reparse a value that can never change or
// fail at runtime.
func getTapHostHardwareAddr() net.HardwareAddr {
addr, err := net.ParseMAC(tapHostMAC)
if err != nil {
log.Fatalf("Failed to parse tap host MAC address %s: %v", tapHostMAC, err)
}

return addr
}

func getVrtNetworkCIDR() *net.IPNet {
cidr := env.GetEnv("SANDBOXES_VRT_NETWORK_CIDR", defaultVrtNetworkCIDR)

Expand Down
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