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Monorepo for Tangled
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import ( "context" _ "embed" "encoding/json" "errors" "fmt" "log/slog" "os" "os/exec" "path/filepath" "strconv" "strings" "sync" "time"
"github.com/digitalocean/go-qemu/qmp" "github.com/google/uuid")
const ( defaultQMPTimeout = 10 * time.Second outerSlirpCIDR = "10.0.2.0/24" innerSlirpNet = "10.0.3.0/24" innerSlirpHost = "10.0.3.2" innerSlirpDNS = "10.0.3.3" innerSlirpDHCP = "10.0.3.15" netnsTapName = "tap0" netnsMTU = "65520")
type QEMUConfig struct { Image ImageSpec BootTimeout time.Duration CID uint32 EnableKVM bool QEMULogPath string QMPPath string SerialLogPath string WorkDir string VolumePaths map[string]string VolumeBaseName string Cgroup CgroupLimits Dev bool}
type QEMUVMHandle struct { cid uint32 Process *os.Process qemuLogPath string QMPMon *qmp.SocketMonitor QMPPath string serialLogPath string workDir string
cmd *exec.Cmd done chan struct{} qemuLogFile *os.File cgroup *CgroupHandle slirpCmd *exec.Cmd slirpExit *os.File waitErr error waitErrMu sync.Mutex}
type qemuRunner struct{}
func (qemuRunner) Validate(spec ImageSpec, enableKVM bool) error { if _, err := exec.LookPath(spec.RunnerCmd()); err != nil { return fmt.Errorf("required host command %q not found in PATH: %w", spec.RunnerCmd(), err) } if _, err := os.Stat("/dev/vhost-vsock"); err != nil { return fmt.Errorf("microvm requires /dev/vhost-vsock for vhost-vsock-device: %w", err) } if enableKVM { if _, err := os.Stat("/dev/kvm"); err != nil { return fmt.Errorf("microvm KVM was requested but /dev/kvm is not accessible: %w", err) } } if len(spec.NetworkInterfaces) > 0 { if _, err := os.Stat("/dev/net/tun"); err != nil { return fmt.Errorf("microvm slirp4netns networking requires /dev/net/tun: %w", err) } for _, cmd := range []string{"ip", "mount", "slirp4netns", "unshare"} { if _, err := exec.LookPath(cmd); err != nil { return fmt.Errorf("required host command %q not found in PATH: %w", cmd, err) } } } return nil}
func (qemuRunner) Start(ctx context.Context, cfg VMConfig, volumePaths map[string]string, logger *slog.Logger) (VMHandle, error) { bootTimeout := cfg.BootTimeout if bootTimeout == 0 { bootTimeout = 10 * time.Second } return StartQEMU(ctx, QEMUConfig{ Image: cfg.Image, BootTimeout: bootTimeout, CID: cfg.CID, EnableKVM: cfg.EnableKVM, WorkDir: cfg.WorkDir, VolumePaths: volumePaths, Cgroup: cfg.Cgroup, Dev: cfg.Dev, }, logger)}
func StartQEMU(ctx context.Context, cfg QEMUConfig, logger *slog.Logger) (VMHandle, error) { if logger == nil { logger = slog.Default() }
workDir := cfg.WorkDir
handle := &QEMUVMHandle{ workDir: workDir, }
var ok bool defer func() { if !ok { _ = handle.Close() } }()
cid := cfg.CID if cid == 0 { var err error cid, err = AllocateCID() if err != nil { return nil, err } } if cid < minGuestCID { return nil, fmt.Errorf("guest CID must be >= %d", minGuestCID) } handle.cid = cid
volumePaths := cfg.VolumePaths
qemuLogPath := cfg.QEMULogPath if qemuLogPath == "" { qemuLogPath = filepath.Join(workDir, "qemu.log") } qemuLogFile, err := createParentedFile(qemuLogPath) if err != nil { return nil, err } handle.qemuLogPath = qemuLogPath handle.qemuLogFile = qemuLogFile
serialLogPath := cfg.SerialLogPath if serialLogPath == "" { serialLogPath = filepath.Join(workDir, "serial.log") } if err := os.MkdirAll(filepath.Dir(serialLogPath), 0o755); err != nil { return nil, fmt.Errorf("create serial log directory: %w", err) } handle.serialLogPath = serialLogPath
qmpPath := cfg.QMPPath if qmpPath == "" { qmpPath = filepath.Join(workDir, "qmp.sock") } handle.QMPPath = qmpPath
qemuCmd := cfg.Image.RunnerCmd() qemuBinary, err := exec.LookPath(qemuCmd) if err != nil { return nil, fmt.Errorf("%s command not found in PATH: %w", qemuCmd, err) }
args, err := qemuArgs(qemuArgsConfig{ Image: cfg.Image, CID: cid, EnableKVM: cfg.EnableKVM, QMPPath: qmpPath, SerialLogPath: serialLogPath, VolumePaths: volumePaths, }) if err != nil { return nil, err }
cmd, slirpNet, err := qemuCommand(ctx, qemuBinary, args, cfg.Image, workDir, cfg.Dev) if err != nil { return nil, err } cmd.Env = append(os.Environ(), "TMPDIR="+workDir) cmd.Stdout = qemuLogFile cmd.Stderr = qemuLogFile
cgroup, err := prepareCgroup(cfg.Cgroup, logger) if err != nil { return nil, err } handle.cgroup = cgroup
logger.Info("starting qemu microvm", "cid", cid, "workDir", workDir, "serialLog", serialLogPath, "qmp", qmpPath) if err := cmd.Start(); err != nil { return nil, fmt.Errorf("starting qemu: %w", err) } handle.cmd = cmd handle.Process = cmd.Process handle.done = make(chan struct{}) go func() { err := cmd.Wait() handle.waitErrMu.Lock() handle.waitErr = err handle.waitErrMu.Unlock() close(handle.done) }()
if err := cgroup.AddProcess(cmd.Process.Pid, logger); err != nil { return nil, err }
if slirpNet != nil { handle.slirpCmd, handle.slirpExit, err = slirpNet.Start(ctx, qemuLogFile, logger) if err != nil { return nil, err } if handle.slirpCmd != nil && handle.slirpCmd.Process != nil { if err := cgroup.AddProcess(handle.slirpCmd.Process.Pid, logger); err != nil { return nil, err } } }
qmpTimeout := cfg.BootTimeout if qmpTimeout == 0 { qmpTimeout = defaultQMPTimeout } if err := handle.waitForQMP(ctx, qmpTimeout); err != nil { return nil, err }
status, err := handle.QMPQueryStatus() if err != nil { return nil, err } if status != "running" { return nil, fmt.Errorf("qemu guest not running (status: %s)", status) } logger.Info("qemu microvm running", "cid", cid, "status", status)
ok = true return handle, nil}
func (h *QEMUVMHandle) Wait() error { if h == nil || h.done == nil { return nil } <-h.done h.waitErrMu.Lock() defer h.waitErrMu.Unlock() return h.waitErr}
func (h *QEMUVMHandle) WaitContext(ctx context.Context) error { if h == nil || h.done == nil { return nil } select { case <-h.done: h.waitErrMu.Lock() defer h.waitErrMu.Unlock() return h.waitErr case <-ctx.Done(): return ctx.Err() }}
func (h *QEMUVMHandle) Kill() error { if h == nil || h.Process == nil { return nil } return h.Process.Kill()}
func (h *QEMUVMHandle) Shutdown(ctx context.Context) error { if h == nil { return nil } if h.QMPMon != nil { if err := h.QMPSystemPowerdown(); err != nil { return err } } if h.done == nil { return nil } select { case <-h.done: return h.Wait() case <-ctx.Done(): _ = h.Kill() _ = h.Wait() return ctx.Err() }}
func (h *QEMUVMHandle) Close() error { if h == nil { return nil }
var closeErr error if h.QMPMon != nil { closeErr = errors.Join(closeErr, h.QMPMon.Disconnect()) h.QMPMon = nil } if h.Process != nil { _ = h.Process.Kill() _ = h.Wait() } if h.slirpExit != nil { _ = h.slirpExit.Close() h.slirpExit = nil } if h.slirpCmd != nil && h.slirpCmd.Process != nil { _ = h.slirpCmd.Process.Kill() _ = h.slirpCmd.Wait() h.slirpCmd = nil } if h.qemuLogFile != nil { closeErr = errors.Join(closeErr, h.qemuLogFile.Close()) h.qemuLogFile = nil } if h.cgroup != nil { closeErr = errors.Join(closeErr, h.cgroup.Close()) h.cgroup = nil } return closeErr}
func (h *QEMUVMHandle) QMPRun(command qmp.Command) ([]byte, error) { if h == nil || h.QMPMon == nil { return nil, fmt.Errorf("qmp monitor is not connected") } data, err := json.Marshal(command) if err != nil { return nil, err } return h.QMPMon.Run(data)}
func (h *QEMUVMHandle) QMPQueryStatus() (string, error) { raw, err := h.QMPRun(qmp.Command{Execute: "query-status"}) if err != nil { return "", fmt.Errorf("qmp query-status failed: %w", err) }
var resp struct { Return struct { Status string `json:"status"` } `json:"return"` } if err := json.Unmarshal(raw, &resp); err != nil { return "", fmt.Errorf("qmp query-status parse: %w", err) } return resp.Return.Status, nil}
func (h *QEMUVMHandle) QMPSystemPowerdown() error { _, err := h.QMPRun(qmp.Command{Execute: "system_powerdown"}) return err}
func (h *QEMUVMHandle) Logs() VMLogs { if h == nil { return VMLogs{} } return VMLogs{ Serial: h.serialLogPath, Extra: map[string]string{ "qemu": h.qemuLogPath, }, }}
func (h *QEMUVMHandle) CID() uint32 { if h == nil { return 0 } return h.cid}
func (h *QEMUVMHandle) WorkDir() string { if h == nil { return "" } return h.workDir}
func (h *QEMUVMHandle) OOMKilled() bool { if h == nil { return false } return h.cgroup.OOMKilled()}
func (h *QEMUVMHandle) waitForQMP(ctx context.Context, timeout time.Duration) error { qmpCtx, cancel := context.WithTimeout(ctx, timeout) defer cancel()
var lastErr error for { mon, err := qmp.NewSocketMonitor("unix", h.QMPPath, 2*time.Second) if err == nil { if err = mon.Connect(); err == nil { h.QMPMon = mon return nil } _ = mon.Disconnect() } lastErr = err
select { case <-qmpCtx.Done(): return fmt.Errorf("qmp connect timeout: %w", lastErr) case <-h.done: return fmt.Errorf("qemu exited before qmp was ready: %w", h.Wait()) case <-time.After(25 * time.Millisecond): } }}
func qemuCommand( ctx context.Context, qemuBinary string, args []string, spec ImageSpec, workDir string, dev bool,) (*exec.Cmd, *slirpNamespace, error) { if len(spec.NetworkInterfaces) == 0 { return exec.CommandContext(ctx, qemuBinary, args...), nil, nil }
ipPath, err := exec.LookPath("ip") if err != nil { return nil, nil, fmt.Errorf("ip command not found in PATH: %w", err) } mountPath, err := exec.LookPath("mount") if err != nil { return nil, nil, fmt.Errorf("mount command not found in PATH: %w", err) } unsharePath, err := exec.LookPath("unshare") if err != nil { return nil, nil, fmt.Errorf("unshare command not found in PATH: %w", err) }
pidFile, resolvPath, wrapperPath, err := prepareQEMUNetnsFiles(workDir, dev) if err != nil { return nil, nil, err }
cmdArgs := append([]string{ "--user", "--map-root-user", "--net", "--mount", "--propagation", "private", "--", wrapperPath, pidFile, ipPath, mountPath, resolvPath, qemuBinary, }, args...)
cmd := exec.CommandContext(ctx, unsharePath, cmdArgs...)
return cmd, &slirpNamespace{ spec: spec, pidFile: pidFile, dev: dev, }, nil}
func prepareQEMUNetnsFiles(workDir string, dev bool) (pidFile, resolvPath, wrapperPath string, err error) { pidFile = filepath.Join(workDir, "qemu-netns.pid") resolvPath = filepath.Join(workDir, "qemu-netns-resolv.conf") wrapperPath = filepath.Join(workDir, "qemu-netns-wrapper")
// the guest resolves through shuttle on 127.0.0.1. keep qemu's slirp DNS // pointed at an unroutable local resolver inside this network namespace so // direct guest queries to 10.0.3.3 don't bypass the shuttle dns policy. if err := os.WriteFile(resolvPath, []byte("nameserver 127.0.0.1\n"), 0o644); err != nil { return "", "", "", fmt.Errorf("write qemu network namespace resolv.conf: %w", err) }
if err := writeNetnsWrapper(wrapperPath, dev); err != nil { return "", "", "", fmt.Errorf("write qemu network namespace wrapper: %w", err) }
return pidFile, resolvPath, wrapperPath, nil}
type qemuArgsConfig struct { Image ImageSpec CID uint32 EnableKVM bool QMPPath string SerialLogPath string VolumePaths map[string]string}
func qemuArgs(cfg qemuArgsConfig) ([]string, error) { uuid := uuid.New()
b := newArgBuilder(64)
addQEMUMachineArgs(&b, cfg, uuid) addQEMUStoreArgs(&b, cfg)
if cfg.EnableKVM { addQEMUKVMArgs(&b, cfg.Image) }
if err := addQEMUVolumeArgs(&b, cfg); err != nil { return nil, err }
if err := addQEMUNetworkArgs(&b, cfg.Image.NetworkInterfaces); err != nil { return nil, err }
b.Optf("-device", "vhost-vsock-device,guest-cid=%d", cfg.CID)
if len(cfg.Image.RunnerConfig.ExtraArgs) > 0 { b.Add(cfg.Image.RunnerConfig.ExtraArgs...) }
return b.Args(), nil}
func addQEMUMachineArgs(b *argBuilder, cfg qemuArgsConfig, uuid uuid.UUID) { if cfg.Image.RunnerConfig.Machine != "" { b.Opt("-M", cfg.Image.RunnerConfig.Machine) } b.Optf("-m", "%dM", cfg.Image.MemoryMiB) b.Opt("-smp", strconv.Itoa(cfg.Image.VCPUs))
b.Add( "-nodefaults", "-no-user-config", "-no-reboot", )
b.Opt("-kernel", cfg.Image.Kernel) b.Opt("-initrd", cfg.Image.Initrd)
b.Opt("-device", "virtio-rng-device")
b.Optf("-smbios", "type=1,uuid=%s", uuid) b.Opt("-serial", "file:"+cfg.SerialLogPath)
// use virtio console if requsted. this is faster than the serial UART logging // because serial has a higher cost when being accesssed. we still have to // support serial itself for early kernel boot but thats OK. if cfg.Image.RunnerConfig.Console == "hvc0" { b.Optf("-chardev", "file,id=virtiocon0,path=%s,append=on", cfg.SerialLogPath) b.Add("-device", "virtio-serial-device") b.Opt("-device", "virtconsole,chardev=virtiocon0") } b.Opt("-display", "none") b.Opt("-monitor", "none") b.Opt("-append", cfg.Image.BootArgs)
b.Opt("-sandbox", "on") b.Optf("-qmp", "unix:%s,server,nowait", cfg.QMPPath)}
func addQEMUStoreArgs(b *argBuilder, cfg qemuArgsConfig) { drive := newOptionBuilder(8) drive.KV("id", "store") drive.KV("format", "raw") drive.Add("read-only=on") drive.KV("file", cfg.Image.StoreDisk) drive.Add("if=none") drive.Add("aio=io_uring")
b.Opt("-drive", drive.String()) b.Opt("-device", "virtio-blk-device,drive=store")}
func addQEMUKVMArgs(b *argBuilder, image ImageSpec) { b.Flag("-enable-kvm") if image.RunnerConfig.CPU != "" { b.Opt("-cpu", image.RunnerConfig.CPU) } b.Opt("-device", "i8042")}
func addQEMUVolumeArgs(b *argBuilder, cfg qemuArgsConfig) error { for index, volume := range cfg.Image.Volumes { path := cfg.VolumePaths[volume.Image] if path == "" { return fmt.Errorf("missing prepared path for volume %q", volume.Image) }
driveID := fmt.Sprintf("volume%d", index)
drive := newOptionBuilder(10) drive.KV("id", driveID) drive.KV("format", "raw") drive.Add("read-only=off") drive.KV("file", path) drive.Add("if=none") drive.Add("aio=io_uring") drive.Add("discard=unmap") drive.Add("cache=none")
b.Opt("-drive", drive.String()) b.Optf("-device", "virtio-blk-device,drive=%s", driveID) }
return nil}
func addQEMUNetworkArgs(b *argBuilder, interfaces []NetworkInterface) error { for _, networkInterface := range interfaces { if networkInterface.Type != "slirp4netns" { return fmt.Errorf("unsupported microvm network interface type %q", networkInterface.Type) }
netdevOpts := newOptionBuilder(6) netdevOpts.Add("user") netdevOpts.KV("id", networkInterface.ID) netdevOpts.KV("net", innerSlirpNet) netdevOpts.KV("host", innerSlirpHost) netdevOpts.KV("dns", innerSlirpDNS) netdevOpts.KV("dhcpstart", innerSlirpDHCP)
b.Opt("-netdev", netdevOpts.String()) b.Optf( "-device", "virtio-net-device,netdev=%s,mac=%s", networkInterface.ID, networkInterface.MAC, ) }
return nil}
func waitForPIDFile(ctx context.Context, path string) (string, error) { waitCtx, cancel := context.WithTimeout(ctx, 5*time.Second) defer cancel()
ticker := time.NewTicker(25 * time.Millisecond) defer ticker.Stop()
for { data, err := os.ReadFile(path) if err == nil { pid := strings.TrimSpace(string(data)) if pid != "" { return pid, nil } } else if !errors.Is(err, os.ErrNotExist) { return "", fmt.Errorf("read qemu network namespace pid: %w", err) }
select { case <-waitCtx.Done(): return "", fmt.Errorf("waiting for qemu network namespace pid: %w", waitCtx.Err()) case <-ticker.C: } }}