package qemu import ( "bufio" "context" "fmt" "log" "os" "strconv" "strings" "time" "github.com/hashicorp/packer/helper/multistep" "github.com/hashicorp/packer/packer" "github.com/digitalocean/go-qemu/qmp" ) // This step waits for the guest address to become available in the network // bridge, then it sets the guestAddress state property. type stepWaitGuestAddress struct { timeout time.Duration } func (s *stepWaitGuestAddress) Run(ctx context.Context, state multistep.StateBag) multistep.StepAction { config := state.Get("config").(*Config) ui := state.Get("ui").(packer.Ui) qmpMonitor := state.Get("qmp_monitor").(*qmp.SocketMonitor) ctx, cancel := context.WithTimeout(ctx, s.timeout) defer cancel() ui.Say(fmt.Sprintf("Waiting for the guest address to become available in the %s network bridge...", config.NetBridge)) for { guestAddress := getGuestAddress(qmpMonitor, config.NetBridge, "user.0") if guestAddress != "" { log.Printf("Found guest address %s", guestAddress) state.Put("guestAddress", guestAddress) return multistep.ActionContinue } select { case <-time.After(10 * time.Second): continue case <-ctx.Done(): return multistep.ActionHalt } } } func (s *stepWaitGuestAddress) Cleanup(state multistep.StateBag) { } func getGuestAddress(qmpMonitor *qmp.SocketMonitor, bridgeName string, deviceName string) string { devices, err := getNetDevices(qmpMonitor) if err != nil { log.Printf("Could not retrieve QEMU QMP network device list: %v", err) return "" } for _, device := range devices { if device.Name == deviceName { ipAddress, _ := getDeviceIPAddress(bridgeName, device.MacAddress) return ipAddress } } log.Printf("QEMU QMP network device %s was not found", deviceName) return "" } func getDeviceIPAddress(device string, macAddress string) (string, error) { // this parses /proc/net/arp to retrieve the given device IP address. // // /proc/net/arp is normally someting alike: // // IP address HW type Flags HW address Mask Device // 192.168.121.111 0x1 0x2 52:54:00:12:34:56 * virbr0 // const ( IPAddressIndex int = iota HWTypeIndex FlagsIndex HWAddressIndex MaskIndex DeviceIndex ) // see ARP flags at https://github.com/torvalds/linux/blob/v5.4/include/uapi/linux/if_arp.h#L132 const ( AtfCom int = 0x02 // ATF_COM (complete) ) f, err := os.Open("/proc/net/arp") if err != nil { return "", fmt.Errorf("failed to open /proc/net/arp: %w", err) } defer f.Close() s := bufio.NewScanner(f) s.Scan() for s.Scan() { fields := strings.Fields(s.Text()) if device != "" && fields[DeviceIndex] != device { continue } if fields[HWAddressIndex] != macAddress { continue } flags, err := strconv.ParseInt(fields[FlagsIndex], 0, 32) if err != nil { return "", fmt.Errorf("failed to parse /proc/net/arp flags field %s: %w", fields[FlagsIndex], err) } if int(flags)&AtfCom == AtfCom { return fields[IPAddressIndex], nil } } return "", fmt.Errorf("could not find %s", macAddress) }