fix: report the status describing a filesystem error, not always EIO

errors.go

@@ -5,6 +5,8 @@ import (
 	"encoding/binary"
 	"errors"
 	"fmt"
+	"io/fs"
+	"syscall"
 )
 
 // RPCError provides the error interface for errors thrown by
@@ -196,6 +198,57 @@ func (s *NFSStatusError) Unwrap() error {
 	return s.WrappedErr
 }
 
+// statusFromError translates err into the NFS status describing it, returning
+// fallback for an error it does not recognize.
+func statusFromError(err error, fallback NFSStatus) NFSStatus {
+	switch {
+	case err == nil:
+		return NFSStatusOk
+	case errors.Is(err, syscall.EROFS):
+		return NFSStatusROFS
+	case errors.Is(err, syscall.ENOSPC):
+		return NFSStatusNoSPC
+	case errors.Is(err, syscall.EDQUOT):
+		return NFSStatusDQuot
+	case errors.Is(err, syscall.ENOTEMPTY):
+		return NFSStatusNotEmpty
+	case errors.Is(err, syscall.EXDEV):
+		return NFSStatusXDev
+	case errors.Is(err, syscall.EISDIR):
+		return NFSStatusIsDir
+	case errors.Is(err, syscall.ENOTDIR):
+		return NFSStatusNotDir
+	case errors.Is(err, syscall.ENAMETOOLONG):
+		return NFSStatusNameTooLong
+	case errors.Is(err, syscall.EMLINK):
+		return NFSStatusMlink
+	case errors.Is(err, syscall.EFBIG):
+		return NFSStatusFBig
+	case errors.Is(err, syscall.ENXIO):
+		return NFSStatusNXIO
+	case errors.Is(err, syscall.EPERM):
+		return NFSStatusPerm
+	// ENOTEMPTY is also fs.ErrExist and EPERM is also fs.ErrPermission, so these
+	// sentinels come last.
+	case errors.Is(err, fs.ErrNotExist):
+		return NFSStatusNoEnt
+	case errors.Is(err, fs.ErrExist):
+		return NFSStatusExist
+	case errors.Is(err, fs.ErrPermission):
+		return NFSStatusAccess
+	case errors.Is(err, fs.ErrInvalid):
+		return NFSStatusInval
+	default:
+		return fallback
+	}
+}
+
+// statusError wraps err in the NFSStatusError describing it, falling back to
+// the given status when the error is unrecognized.
+func statusError(err error, fallback NFSStatus) *NFSStatusError {
+	return &NFSStatusError{statusFromError(err, fallback), err}
+}
+
 // StatusErrorWithBody is an NFS error with a payload.
 type StatusErrorWithBody struct {
 	NFSStatusError

errors_test.go

@@ -0,0 +1,17 @@
+package nfs
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestStatusErrorKeepsFallback(t *testing.T) {
+	err := errors.New("backend exploded")
+	statusErr := statusError(err, NFSStatusAccess)
+	if statusErr.NFSStatus != NFSStatusAccess {
+		t.Errorf("status = %v, want %v", statusErr.NFSStatus, NFSStatusAccess)
+	}
+	if !errors.Is(statusErr, err) {
+		t.Errorf("statusError dropped the wrapped error: %v", statusErr)
+	}
+}

nfs_oncreate.go

@@ -70,7 +70,7 @@ func onCreate(ctx context.Context, w *response, userHandle Handler) error {
 		}
 	} else {
 		if s, err := fs.Stat(fs.Join(path...)); err != nil {
-			return &NFSStatusError{NFSStatusAccess, err}
+			return statusError(err, NFSStatusAccess)
 		} else if !s.IsDir() {
 			return &NFSStatusError{NFSStatusNotDir, nil}
 		}
@@ -79,18 +79,18 @@ func onCreate(ctx context.Context, w *response, userHandle Handler) error {
 	file, err := fs.Create(newFilePath)
 	if err != nil {
 		Log.Errorf("Error Creating: %v", err)
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	}
 	if err := file.Close(); err != nil {
 		Log.Errorf("Error Creating: %v", err)
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	}
 
 	fp := userHandle.ToHandle(fs, newFile)
 	changer := userHandle.Change(fs)
 	if err := attrs.Apply(changer, fs, newFilePath); err != nil {
 		Log.Errorf("Error applying attributes: %v\n", err)
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 
 	writer := bytes.NewBuffer([]byte{})

nfs_ongetattr.go

@@ -3,7 +3,6 @@ package nfs
 import (
 	"bytes"
 	"context"
-	"os"
 
 	"github.com/willscott/go-nfs-client/nfs/xdr"
 )
@@ -22,10 +21,7 @@ func onGetAttr(ctx context.Context, w *response, userHandle Handler) error {
 	fullPath := fs.Join(path...)
 	info, err := fs.Lstat(fullPath)
 	if err != nil {
-		if os.IsNotExist(err) {
-			return &NFSStatusError{NFSStatusNoEnt, err}
-		}
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 	attr := ToFileAttribute(info, fullPath)
 

nfs_onlink.go

@@ -44,7 +44,7 @@ func onLink(ctx context.Context, w *response, userHandle Handler) error {
 		return &NFSStatusError{NFSStatusExist, os.ErrExist}
 	}
 	if s, err := fs.Stat(fs.Join(path...)); err != nil {
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	} else if !s.IsDir() {
 		return &NFSStatusError{NFSStatusNotDir, nil}
 	}
@@ -61,10 +61,10 @@ func onLink(ctx context.Context, w *response, userHandle Handler) error {
 
 	err = cos.Link(string(target), newFilePath)
 	if err != nil {
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	}
 	if err := attrs.Apply(changer, fs, newFilePath); err != nil {
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 
 	writer := bytes.NewBuffer([]byte{})

nfs_onmkdir.go

@@ -49,21 +49,21 @@ func onMkdir(ctx context.Context, w *response, userHandle Handler) error {
 		}
 	} else {
 		if s, err := fs.Stat(fs.Join(path...)); err != nil {
-			return &NFSStatusError{NFSStatusAccess, err}
+			return statusError(err, NFSStatusAccess)
 		} else if !s.IsDir() {
 			return &NFSStatusError{NFSStatusNotDir, nil}
 		}
 	}
 
 	if err := fs.MkdirAll(newFolderPath, attrs.Mode(mkdirDefaultMode)); err != nil {
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	}
 
 	fp := userHandle.ToHandle(fs, newFolder)
 	changer := userHandle.Change(fs)
 	if changer != nil {
 		if err := attrs.Apply(changer, fs, newFolderPath); err != nil {
-			return &NFSStatusError{NFSStatusIO, err}
+			return statusError(err, NFSStatusIO)
 		}
 	}
 

nfs_onread.go

@@ -69,7 +69,7 @@ func onRead(ctx context.Context, w *response, userHandle Handler) error {
 	// todo: multiple reads if size isn't full
 	cnt, err := fh.ReadAt(resp.Data, int64(obj.Offset))
 	if err != nil && !errors.Is(err, io.EOF) {
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 	resp.Count = uint32(cnt)
 	resp.Data = resp.Data[:resp.Count]

nfs_onremove.go

@@ -3,7 +3,6 @@ package nfs
 import (
 	"bytes"
 	"context"
-	"errors"
 	"os"
 
 	"github.com/go-git/go-billy/v6"
@@ -62,14 +61,8 @@ func onRemoveObj(ctx context.Context, w *response, userHandle Handler, directory
 
 	fullPath := fs.Join(path...)
 	dirInfo, err := fs.Stat(fullPath)
-	if os.IsNotExist(err) {
-		return &NFSStatusError{NFSStatusNoEnt, err}
-	}
-	if os.IsPermission(err) {
-		return &NFSStatusError{NFSStatusAccess, err}
-	}
 	if err != nil {
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 	if !dirInfo.IsDir() {
 		return &NFSStatusError{NFSStatusNotDir, nil}
@@ -86,16 +79,10 @@ func onRemoveObj(ctx context.Context, w *response, userHandle Handler, directory
 	// Lstat, not Stat: POSIX rmdir()/unlink() act on the entry itself, not what it points to :
 	// rmdir() must reject a symlink to an empty directory, unlink() must remove the symlink itself.
 	targetInfo, err := fs.Lstat(toDelete)
-	if os.IsNotExist(err) {
-		return &NFSStatusError{NFSStatusNoEnt, err}
-	}
-	if os.IsPermission(err) {
+	if err != nil {
 		// A permission error here means an ancestor directory in toDelete's path
 		// lacks its executable permission, not that toDelete itself is inaccessible.
-		return &NFSStatusError{NFSStatusAccess, err}
-	}
-	if err != nil {
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 
 	if directory && !targetInfo.IsDir() {
@@ -107,38 +94,21 @@ func onRemoveObj(ctx context.Context, w *response, userHandle Handler, directory
 
 	if directory {
 		empty, err := isEmptyDir(ctx, userHandle, fs, toDelete)
-		// This error can come from a user-supplied OpenDir, which may return
-		// a wrapped os.ErrNotExist/os.ErrPermission. errors.Is sees through the
-		// wrapping; the os.IsNotExist/os.IsPermission checks elsewhere do not.
-		if errors.Is(err, os.ErrNotExist) {
-			return &NFSStatusError{NFSStatusNoEnt, err}
-		}
-		if errors.Is(err, os.ErrPermission) {
-			return &NFSStatusError{NFSStatusAccess, err}
-		}
 		if err != nil {
-			return &NFSStatusError{NFSStatusIO, err}
+			return statusError(err, NFSStatusIO)
 		}
 		if !empty {
 			return &NFSStatusError{NFSStatusNotEmpty, nil}
 		}
 	}
 
 	err = fs.Remove(toDelete)
-	if os.IsNotExist(err) {
-		return &NFSStatusError{NFSStatusNoEnt, err}
-	}
-	if os.IsPermission(err) {
-		return &NFSStatusError{NFSStatusAccess, err}
-	}
 	if err != nil {
-		// We passed all directory/empty checks above, so an error here likely means
-		// the target changed underneath us (the TOCTOU window noted above) - e.g. a
-		// directory that just became non-empty. We report NFSStatusIO rather than
-		// trying to distinguish that case, since billy doesn't expose a portable way
-		// to recognize it.
+		// The checks above passed, so an error here means the target changed
+		// underneath us in the TOCTOU window - a directory that became non-empty,
+		// say.
 		Log.Errorf("remove %q after passing directory checks: %v", toDelete, err)
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 
 	if err := userHandle.InvalidateHandle(fs, toDeleteHandle); err != nil {

nfs_onrename.go

@@ -48,10 +48,7 @@ func onRename(ctx context.Context, w *response, userHandle Handler) error {
 	fromDirPath := fs.Join(fromPath...)
 	fromDirInfo, err := fs.Stat(fromDirPath)
 	if err != nil {
-		if os.IsNotExist(err) {
-			return &NFSStatusError{NFSStatusNoEnt, err}
-		}
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 	if !fromDirInfo.IsDir() {
 		return &NFSStatusError{NFSStatusNotDir, nil}
@@ -61,10 +58,7 @@ func onRename(ctx context.Context, w *response, userHandle Handler) error {
 	toDirPath := fs.Join(toPath...)
 	toDirInfo, err := fs.Stat(toDirPath)
 	if err != nil {
-		if os.IsNotExist(err) {
-			return &NFSStatusError{NFSStatusNoEnt, err}
-		}
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 	if !toDirInfo.IsDir() {
 		return &NFSStatusError{NFSStatusNotDir, nil}
@@ -78,13 +72,7 @@ func onRename(ctx context.Context, w *response, userHandle Handler) error {
 
 	err = fs.Rename(fromLoc, toLoc)
 	if err != nil {
-		if os.IsNotExist(err) {
-			return &NFSStatusError{NFSStatusNoEnt, err}
-		}
-		if os.IsPermission(err) {
-			return &NFSStatusError{NFSStatusAccess, err}
-		}
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 
 	if err := userHandle.InvalidateHandle(fs, oldHandle); err != nil {

nfs_onsymlink.go

@@ -43,21 +43,21 @@ func onSymlink(ctx context.Context, w *response, userHandle Handler) error {
 		return &NFSStatusError{NFSStatusExist, os.ErrExist}
 	}
 	if s, err := fs.Stat(fs.Join(path...)); err != nil {
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	} else if !s.IsDir() {
 		return &NFSStatusError{NFSStatusNotDir, nil}
 	}
 
 	err = fs.Symlink(string(target), newFilePath)
 	if err != nil {
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	}
 
 	fp := userHandle.ToHandle(fs, append(path, string(obj.Filename)))
 	changer := userHandle.Change(fs)
 	if changer != nil {
 		if err := attrs.Apply(changer, fs, newFilePath); err != nil {
-			return &NFSStatusError{NFSStatusIO, err}
+			return statusError(err, NFSStatusIO)
 		}
 	}
 

nfs_onwrite.go

@@ -52,10 +52,7 @@ func onWrite(ctx context.Context, w *response, userHandle Handler) error {
 	fullPath := fs.Join(path...)
 	info, err := fs.Stat(fullPath)
 	if err != nil {
-		if os.IsNotExist(err) {
-			return &NFSStatusError{NFSStatusNoEnt, err}
-		}
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	}
 	if !info.Mode().IsRegular() {
 		return &NFSStatusError{NFSStatusInval, os.ErrInvalid}
@@ -65,7 +62,7 @@ func onWrite(ctx context.Context, w *response, userHandle Handler) error {
 	// now the actual op.
 	file, err := fs.OpenFile(fs.Join(path...), os.O_RDWR, info.Mode().Perm())
 	if err != nil {
-		return &NFSStatusError{NFSStatusAccess, err}
+		return statusError(err, NFSStatusAccess)
 	}
 	defer func() {
 		if file != nil {
@@ -84,13 +81,13 @@ func onWrite(ctx context.Context, w *response, userHandle Handler) error {
 	var writtenCount int
 
 	if writtenCount, err = file.WriteAt(req.Data[:end], int64(req.Offset)); err != nil {
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 	err = file.Close()
 	file = nil // No more need to close on exit.
 	if err != nil {
 		Log.Errorf("error closing: %v", err)
-		return &NFSStatusError{NFSStatusIO, err}
+		return statusError(err, NFSStatusIO)
 	}
 
 	writer := bytes.NewBuffer([]byte{})