Add experimental Void guest workflow and vsock agent

Make iterating on a Firecracker-friendly Void guest practical without replacing the Debian default image path.

Add local Void rootfs build/register/verify plumbing, a language-agnostic dev package baseline, and guest SSH/work-disk hardening so new images use the runtime bundle key, keep a normal root bash environment, and repair stale nested /root layouts on restart.

Replace the guest PING/PONG responder with an HTTP /healthz agent over vsock, rename the runtime bundle and config surface from ping helper to agent while still accepting the legacy keys, and route the post-SSH reminder through the new vm.health path.

Validated with GOCACHE=/tmp/banger-gocache go test ./..., make build, bash -n customize.sh make-rootfs-void.sh, and git diff --check.
This commit is contained in:
Thales Maciel 2026-03-19 14:51:25 -03:00
parent c8d9a122f9
commit 3ed78fdcfc
No known key found for this signature in database
GPG key ID: 33112E6833C34679
42 changed files with 2222 additions and 388 deletions

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@ -0,0 +1,158 @@
package vsockagent
import (
"context"
"encoding/json"
"errors"
"fmt"
"io"
"log/slog"
"net"
"net/http"
"time"
sdkvsock "github.com/firecracker-microvm/firecracker-go-sdk/vsock"
"github.com/sirupsen/logrus"
)
const (
Port uint32 = 42070
HealthPath = "/healthz"
HealthyStatus = "ok"
GuestBinaryName = "banger-vsock-agent"
GuestInstallPath = "/usr/local/bin/" + GuestBinaryName
ServiceName = "banger-vsock-agent.service"
serviceUnit = `[Unit]
Description=Banger vsock agent
After=network.target
[Service]
Type=simple
ExecStart=/usr/local/bin/banger-vsock-agent
Restart=on-failure
RestartSec=1
[Install]
WantedBy=multi-user.target
`
modulesLoadConfig = "vsock\nvmw_vsock_virtio_transport\n"
)
type HealthResponse struct {
Status string `json:"status"`
}
func NewHandler() http.Handler {
mux := http.NewServeMux()
mux.HandleFunc(HealthPath, func(w http.ResponseWriter, r *http.Request) {
if r.Method != http.MethodGet {
http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
return
}
w.Header().Set("Content-Type", "application/json")
_ = json.NewEncoder(w).Encode(HealthResponse{Status: HealthyStatus})
})
return mux
}
func Health(ctx context.Context, logger *slog.Logger, socketPath string) error {
transport := &http.Transport{
DisableKeepAlives: true,
DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
return sdkvsock.DialContext(
ctx,
socketPath,
Port,
sdkvsock.WithRetryTimeout(3*time.Second),
sdkvsock.WithRetryInterval(100*time.Millisecond),
sdkvsock.WithLogger(newLogger(logger)),
)
},
}
defer transport.CloseIdleConnections()
req, err := http.NewRequestWithContext(ctx, http.MethodGet, "http://vsock"+HealthPath, nil)
if err != nil {
return err
}
resp, err := (&http.Client{Transport: transport}).Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
body, _ := io.ReadAll(io.LimitReader(resp.Body, 1024))
return fmt.Errorf("unexpected health status %d: %s", resp.StatusCode, string(body))
}
var payload HealthResponse
if err := json.NewDecoder(resp.Body).Decode(&payload); err != nil {
return err
}
if payload.Status != HealthyStatus {
return fmt.Errorf("unexpected health response status %q", payload.Status)
}
if logger != nil {
logger.Debug("vsock health ok", "vsock_path", socketPath, "vsock_port", Port)
}
return nil
}
func ServiceUnit() string {
return serviceUnit
}
func ModulesLoadConfig() string {
return modulesLoadConfig
}
func ReminderMessage(name string) string {
return fmt.Sprintf("session ended; %s is still running (stop it with 'banger vm stop %s')", name, name)
}
func WarningMessage(name string, err error) string {
if err == nil {
return ""
}
return fmt.Sprintf("warning: failed to check whether %s is still running: %v", name, err)
}
func newLogger(base *slog.Logger) *logrus.Entry {
logger := logrus.New()
logger.SetOutput(io.Discard)
logger.SetLevel(logrus.DebugLevel)
logger.AddHook(slogHook{logger: base})
return logrus.NewEntry(logger)
}
type slogHook struct {
logger *slog.Logger
}
func (h slogHook) Levels() []logrus.Level {
return logrus.AllLevels
}
func (h slogHook) Fire(entry *logrus.Entry) error {
if h.logger == nil {
return nil
}
level := slog.LevelDebug
switch entry.Level {
case logrus.ErrorLevel, logrus.FatalLevel, logrus.PanicLevel:
level = slog.LevelError
case logrus.WarnLevel:
level = slog.LevelWarn
case logrus.InfoLevel:
level = slog.LevelInfo
}
attrs := make([]any, 0, len(entry.Data)*2)
for key, value := range entry.Data {
attrs = append(attrs, key, value)
}
h.logger.Log(context.Background(), level, entry.Message, attrs...)
return nil
}
func IsServerClosed(err error) bool {
return errors.Is(err, http.ErrServerClosed)
}

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@ -0,0 +1,133 @@
package vsockagent
import (
"bytes"
"context"
"encoding/json"
"net"
"net/http"
"path/filepath"
"strings"
"testing"
"time"
)
func TestNewHandlerHealthz(t *testing.T) {
t.Parallel()
req, err := http.NewRequest(http.MethodGet, HealthPath, nil)
if err != nil {
t.Fatalf("NewRequest: %v", err)
}
rr := newTestResponseRecorder()
NewHandler().ServeHTTP(rr, req)
if rr.status != http.StatusOK {
t.Fatalf("status = %d, want %d", rr.status, http.StatusOK)
}
if got := rr.headers.Get("Content-Type"); got != "application/json" {
t.Fatalf("content-type = %q", got)
}
var payload HealthResponse
if err := json.Unmarshal(rr.body.Bytes(), &payload); err != nil {
t.Fatalf("Unmarshal: %v", err)
}
if payload.Status != HealthyStatus {
t.Fatalf("status = %q, want %q", payload.Status, HealthyStatus)
}
}
func TestHealth(t *testing.T) {
t.Parallel()
dir := t.TempDir()
socketPath := filepath.Join(dir, "fc.vsock")
listener, err := net.Listen("unix", socketPath)
if err != nil {
t.Fatalf("Listen: %v", err)
}
defer listener.Close()
done := make(chan error, 1)
go func() {
conn, err := listener.Accept()
if err != nil {
done <- err
return
}
defer conn.Close()
buf := make([]byte, 0, 256)
tmp := make([]byte, 256)
for {
n, err := conn.Read(tmp)
if err != nil {
done <- err
return
}
buf = append(buf, tmp[:n]...)
if strings.Contains(string(buf), "\n") {
break
}
}
if got := string(buf); got != "CONNECT 42070\n" {
done <- unexpectedStringError(got)
return
}
if _, err := conn.Write([]byte("OK 55\n")); err != nil {
done <- err
return
}
buf = buf[:0]
for {
n, err := conn.Read(tmp)
if err != nil {
done <- err
return
}
buf = append(buf, tmp[:n]...)
if strings.Contains(string(buf), "\r\n\r\n") {
break
}
}
req := string(buf)
if !strings.Contains(req, "GET /healthz HTTP/1.1\r\n") {
done <- unexpectedStringError(req)
return
}
_, err = conn.Write([]byte("HTTP/1.1 200 OK\r\nContent-Type: application/json\r\nContent-Length: 15\r\n\r\n{\"status\":\"ok\"}"))
done <- err
}()
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
if err := Health(ctx, nil, socketPath); err != nil {
t.Fatalf("Health: %v", err)
}
if err := <-done; err != nil {
t.Fatalf("server: %v", err)
}
}
type testResponseRecorder struct {
headers http.Header
body bytes.Buffer
status int
}
func newTestResponseRecorder() *testResponseRecorder {
return &testResponseRecorder{headers: make(http.Header), status: http.StatusOK}
}
func (r *testResponseRecorder) Header() http.Header { return r.headers }
func (r *testResponseRecorder) Write(data []byte) (int, error) { return r.body.Write(data) }
func (r *testResponseRecorder) WriteHeader(status int) { r.status = status }
type unexpectedStringError string
func (e unexpectedStringError) Error() string {
return "unexpected string: " + string(e)
}