return nil, EINVAL
	}
	sa, _, err := parseLinkLayerAddr(b[4:])
	if err != nil {
		return nil, err
	}
	rsa := (*RawSockaddrDatalink)(unsafe.Pointer(&b[0]))
	sa.Len = rsa.Len
	sa.Family = rsa.Family
	sa.Index = rsa.Index
	return sa, nil
}

// parseLinkLayerAddr parses b as a datalink socket address in
// conventional BSD kernel form.
func parseLinkLayerAddr(b []byte) (*SockaddrDatalink, int, error) {