features: wrap EPERM errors from all probe APIs

In an attempt to simplify the switch blocks in all types of feature
probes, lift the arbitrary EPERM wrapping exception.

Also, move the call to fd.Close() out of the switch statement to live
closer to the call that returns the fd. The fd can always be immediately
closed.

Signed-off-by: Timo Beckers <timo@isovalent.com>

features/map.go

@@ -130,6 +130,9 @@ func haveMapType(mt ebpf.MapType) error {
 	}
 
 	fd, err := sys.MapCreate(createMapTypeAttr(mt))
+	if err == nil {
+		fd.Close()
+	}
 
 	switch {
 	// For nested and storage map types we accept EBADF as indicator that these maps are supported
@@ -145,16 +148,9 @@ func haveMapType(mt ebpf.MapType) error {
 	case errors.Is(err, unix.EINVAL), errors.Is(err, unix.E2BIG):
 		err = fmt.Errorf("%w", ebpf.ErrNotSupported)
 
-	// EPERM is kept as-is and is not converted or wrapped.
-	case errors.Is(err, unix.EPERM):
-		break
-
 	// Wrap unexpected errors.
 	case err != nil:
 		err = fmt.Errorf("unexpected error during feature probe: %w", err)
-
-	default:
-		fd.Close()
 	}
 
 	mc.mapTypes[mt] = err

features/misc.go

@@ -92,6 +92,9 @@ func probeMisc(mt miscType) error {
 	}
 
 	fd, err := sys.ProgLoad(attr)
+	if err == nil {
+		fd.Close()
+	}
 
 	switch {
 	// EINVAL occurs when attempting to create a program with an unknown type.
@@ -101,16 +104,9 @@ func probeMisc(mt miscType) error {
 	case errors.Is(err, unix.EINVAL), errors.Is(err, unix.E2BIG):
 		err = fmt.Errorf("%w", ebpf.ErrNotSupported)
 
-	// EPERM is kept as-is and is not converted or wrapped.
-	case errors.Is(err, unix.EPERM):
-		break
-
 	// Wrap unexpected errors.
 	case err != nil:
 		err = fmt.Errorf("unexpected error during feature probe: %w", err)
-
-	default:
-		fd.Close()
 	}
 
 	miscs.miscTypes[mt] = err

features/prog.go

@@ -138,6 +138,9 @@ func haveProgramType(pt ebpf.ProgramType) error {
 	}
 
 	fd, err := sys.ProgLoad(attr)
+	if err == nil {
+		fd.Close()
+	}
 
 	switch {
 	// EINVAL occurs when attempting to create a program with an unknown type.
@@ -147,16 +150,9 @@ func haveProgramType(pt ebpf.ProgramType) error {
 	case errors.Is(err, unix.EINVAL), errors.Is(err, unix.E2BIG):
 		err = fmt.Errorf("%w", ebpf.ErrNotSupported)
 
-	// EPERM is kept as-is and is not converted or wrapped.
-	case errors.Is(err, unix.EPERM):
-		break
-
 	// Wrap unexpected errors.
 	case err != nil:
 		err = fmt.Errorf("unexpected error during feature probe: %w", err)
-
-	default:
-		fd.Close()
 	}
 
 	pc.types[pt] = err
@@ -210,12 +206,11 @@ func haveProgramHelper(pt ebpf.ProgramType, helper asm.BuiltinFunc) error {
 	}
 
 	fd, err := sys.ProgLoad(attr)
-
-	switch {
-	// If there is no error we need to close the FD of the prog.
-	case err == nil:
+	if err == nil {
 		fd.Close()
+	}
 
+	switch {
 	// EACCES occurs when attempting to create a program probe with a helper
 	// while the register args when calling this helper aren't set up properly.
 	// We interpret this as the helper being available, because the verifier
@@ -232,10 +227,6 @@ func haveProgramHelper(pt ebpf.ProgramType, helper asm.BuiltinFunc) error {
 		// TODO: possibly we need to check verifier output here to be sure
 		err = fmt.Errorf("%w", ebpf.ErrNotSupported)
 
-	// EPERM is kept as-is and is not converted or wrapped.
-	case errors.Is(err, unix.EPERM):
-		break
-
 	// Wrap unexpected errors.
 	case err != nil:
 		err = fmt.Errorf("unexpected error during feature probe: %w", err)