feat: add diagnostics and safe reset maintenance

internal/operationlock/lock.go

@@ -0,0 +1,84 @@
+// Package operationlock serializes proxyctl state mutations across processes.
+package operationlock
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+
+	"golang.org/x/sys/unix"
+
+	"proxyctl/internal/securefs"
+)
+
+type Lock struct {
+	path  string
+	uid   int
+	gid   int
+	owned bool
+}
+
+func New(path string) *Lock { return &Lock{path: path} }
+func NewOwned(path string, uid, gid int) *Lock {
+	return &Lock{path: path, uid: uid, gid: gid, owned: true}
+}
+
+func (l *Lock) Lock(ctx context.Context) (func(), error) {
+	if !filepath.IsAbs(l.path) {
+		return nil, errors.New("operation lock path must be absolute")
+	}
+	directory := filepath.Dir(l.path)
+	if err := os.MkdirAll(directory, 0o700); err != nil {
+		return nil, fmt.Errorf("create operation lock directory: %w", err)
+	}
+	if err := os.Chmod(directory, 0o700); err != nil {
+		return nil, fmt.Errorf("secure operation lock directory: %w", err)
+	}
+	if l.owned && (os.Geteuid() != l.uid || os.Getegid() != l.gid) {
+		if err := os.Chown(directory, l.uid, l.gid); err != nil {
+			return nil, fmt.Errorf("set operation lock directory owner: %w", err)
+		}
+	}
+	file, err := securefs.OpenNoFollow(l.path, unix.O_CREAT|unix.O_RDWR|unix.O_NONBLOCK, 0o600)
+	if err != nil {
+		return nil, fmt.Errorf("open operation lock: %w", err)
+	}
+	info, err := file.Stat()
+	if err != nil || !info.Mode().IsRegular() {
+		file.Close()
+		if err != nil {
+			return nil, fmt.Errorf("inspect operation lock: %w", err)
+		}
+		return nil, errors.New("operation lock is not a regular file")
+	}
+	if err := file.Chmod(0o600); err != nil {
+		file.Close()
+		return nil, fmt.Errorf("secure operation lock: %w", err)
+	}
+	if l.owned && (os.Geteuid() != l.uid || os.Getegid() != l.gid) {
+		if err := file.Chown(l.uid, l.gid); err != nil {
+			file.Close()
+			return nil, fmt.Errorf("set operation lock owner: %w", err)
+		}
+	}
+	for {
+		err = unix.Flock(int(file.Fd()), unix.LOCK_EX|unix.LOCK_NB)
+		if err == nil {
+			break
+		}
+		if !errors.Is(err, unix.EWOULDBLOCK) && !errors.Is(err, unix.EAGAIN) {
+			file.Close()
+			return nil, fmt.Errorf("acquire operation lock: %w", err)
+		}
+		select {
+		case <-ctx.Done():
+			file.Close()
+			return nil, ctx.Err()
+		case <-time.After(10 * time.Millisecond):
+		}
+	}
+	return func() { _ = unix.Flock(int(file.Fd()), unix.LOCK_UN); _ = file.Close() }, nil
+}

internal/operationlock/lock_test.go

@@ -0,0 +1,30 @@
+package operationlock_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"proxyctl/internal/operationlock"
+)
+
+func TestLockSerializesIndependentInstancesAndHonorsContext(t *testing.T) {
+	path := t.TempDir() + "/proxyctl.lock"
+	first := operationlock.New(path)
+	second := operationlock.New(path)
+	unlock, err := first.Lock(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Millisecond)
+	defer cancel()
+	if _, err := second.Lock(ctx); err == nil {
+		t.Fatal("second lock acquired while first held")
+	}
+	unlock()
+	unlockSecond, err := second.Lock(context.Background())
+	if err != nil {
+		t.Fatal(err)
+	}
+	unlockSecond()
+}