banger/internal/firecracker/client.go

package firecracker

import (
	"context"
	"io"
	"os"
	"os/exec"
	"strings"
	"sync"

	sdk "github.com/firecracker-microvm/firecracker-go-sdk"
	models "github.com/firecracker-microvm/firecracker-go-sdk/client/models"
	"github.com/sirupsen/logrus"
)

type MachineConfig struct {
	BinaryPath      string
	VMID            string
	SocketPath      string
	LogPath         string
	MetricsPath     string
	KernelImagePath string
	InitrdPath      string
	KernelArgs      string
	RootDrivePath   string
	WorkDrivePath   string
	TapDevice       string
	VCPUCount       int
	MemoryMiB       int
}

type Machine struct {
	machine   *sdk.Machine
	logFile   *os.File
	closeOnce sync.Once
}

type Client struct {
	client *sdk.Client
}

func NewMachine(ctx context.Context, cfg MachineConfig) (*Machine, error) {
	logFile, err := openLogFile(cfg.LogPath)
	if err != nil {
		return nil, err
	}

	cmd := buildProcessRunner(ctx, cfg, logFile)
	machine, err := sdk.NewMachine(
		ctx,
		buildConfig(cfg),
		sdk.WithProcessRunner(cmd),
		sdk.WithLogger(newLogger()),
	)
	if err != nil {
		if logFile != nil {
			_ = logFile.Close()
		}
		return nil, err
	}

	return &Machine{machine: machine, logFile: logFile}, nil
}

func (m *Machine) Start(ctx context.Context) error {
	if err := m.machine.Start(ctx); err != nil {
		m.closeLog()
		return err
	}

	go func() {
		_ = m.machine.Wait(context.Background())
		m.closeLog()
	}()

	return nil
}

func (m *Machine) PID() (int, error) {
	return m.machine.PID()
}

func New(apiSock string) *Client {
	return &Client{client: sdk.NewClient(apiSock, newLogger(), false)}
}

func (c *Client) SendCtrlAltDel(ctx context.Context) error {
	action := models.InstanceActionInfoActionTypeSendCtrlAltDel
	_, err := c.client.CreateSyncAction(ctx, &models.InstanceActionInfo{
		ActionType: &action,
	})
	return err
}

func openLogFile(path string) (*os.File, error) {
	if path == "" {
		return nil, nil
	}
	return os.OpenFile(path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o644)
}

func buildConfig(cfg MachineConfig) sdk.Config {
	drives := sdk.NewDrivesBuilder(
		cfg.RootDrivePath,
	).
		WithRootDrive(cfg.RootDrivePath, sdk.WithDriveID("rootfs"), sdk.WithReadOnly(false)).
		AddDrive(cfg.WorkDrivePath, false, sdk.WithDriveID("work")).
		Build()

	return sdk.Config{
		SocketPath:      cfg.SocketPath,
		LogPath:         cfg.LogPath,
		MetricsPath:     cfg.MetricsPath,
		KernelImagePath: cfg.KernelImagePath,
		InitrdPath:      cfg.InitrdPath,
		KernelArgs:      cfg.KernelArgs,
		Drives:          drives,
		NetworkInterfaces: sdk.NetworkInterfaces{{
			StaticConfiguration: &sdk.StaticNetworkConfiguration{
				HostDevName: cfg.TapDevice,
			},
		}},
		MachineCfg: models.MachineConfiguration{
			VcpuCount:  sdk.Int64(int64(cfg.VCPUCount)),
			MemSizeMib: sdk.Int64(int64(cfg.MemoryMiB)),
			Smt:        sdk.Bool(false),
		},
		VMID: cfg.VMID,
	}
}

func buildProcessRunner(ctx context.Context, cfg MachineConfig, logFile *os.File) *exec.Cmd {
	script := strings.Join([]string{
		"umask 000",
		"exec " + shellQuote(cfg.BinaryPath) +
			" --api-sock " + shellQuote(cfg.SocketPath) +
			" --id " + shellQuote(cfg.VMID),
	}, " && ")

	cmd := exec.CommandContext(ctx, "sudo", "-n", "sh", "-c", script)
	cmd.Stdin = nil
	if logFile != nil {
		cmd.Stdout = logFile
		cmd.Stderr = logFile
	}
	return cmd
}

func shellQuote(value string) string {
	return "'" + strings.ReplaceAll(value, "'", `'"'"'`) + "'"
}

func newLogger() *logrus.Entry {
	logger := logrus.New()
	logger.SetOutput(io.Discard)
	return logrus.NewEntry(logger)
}

func (m *Machine) closeLog() {
	m.closeOnce.Do(func() {
		if m.logFile != nil {
			_ = m.logFile.Close()
		}
	})
}