kea/src/lib/dns/python/name_python.cc

// Copyright (C) 2010  Internet Systems Consortium, Inc. ("ISC")
//
// Permission to use, copy, modify, and/or distribute this software for any
// purpose with or without fee is hereby granted, provided that the above
// copyright notice and this permission notice appear in all copies.
//
// THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
// REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
// AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
// INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
// LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
// OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
// PERFORMANCE OF THIS SOFTWARE.

// $Id$

//
// Declaration of the custom exceptions
// Initialization and addition of these go in the module init at the
// end
//
static PyObject* po_EmptyLabel;
static PyObject* po_TooLongName;
static PyObject* po_TooLongLabel;
static PyObject* po_BadLabelType;
static PyObject* po_BadEscape;
static PyObject* po_IncompleteName;
static PyObject* po_InvalidBufferPosition;
static PyObject* po_DNSMessageFORMERR;

//
// Declaration of enums
// Initialization and addition of these go in the module init at the
// end
//
static PyObject* po_NameRelation;

//
// Definition of the classes
//

// For each class, we need a struct, a helper functions (init, destroy,
// and static wrappers around the methods we export), a list of methods,
// and a type description
using namespace isc::dns;

// NameComparisonResult
class s_NameComparisonResult : public PyObject {
public:
    isc::dns::NameComparisonResult* ncr;
};

static int NameComparisonResult_init(s_NameComparisonResult* self UNUSED_PARAM, PyObject* args UNUSED_PARAM);
static void NameComparisonResult_destroy(s_NameComparisonResult* self);
static PyObject* NameComparisonResult_getOrder(s_NameComparisonResult* self);
static PyObject* NameComparisonResult_getCommonLabels(s_NameComparisonResult* self);
static PyObject* NameComparisonResult_getRelation(s_NameComparisonResult* self);

static PyMethodDef NameComparisonResult_methods[] = {
    { "get_order", reinterpret_cast<PyCFunction>(NameComparisonResult_getOrder), METH_NOARGS,
      "Returns the order" },
    { "get_common_labels", reinterpret_cast<PyCFunction>(NameComparisonResult_getCommonLabels), METH_NOARGS,
      "Returns the number of common labels" },
    { "get_relation", reinterpret_cast<PyCFunction>(NameComparisonResult_getRelation), METH_NOARGS,
      "Returns the relation" },
    { NULL, NULL, 0, NULL }
};

static PyTypeObject name_comparison_result_type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "libdns_python.NameComparisonResult",
    sizeof(s_NameComparisonResult),           // tp_basicsize
    0,                                        // tp_itemsize
    (destructor)NameComparisonResult_destroy, // tp_dealloc
    NULL,                                     // tp_print
    NULL,                                     // tp_getattr
    NULL,                                     // tp_setattr
    NULL,                                     // tp_reserved
    NULL,                                     // tp_repr
    NULL,                                     // tp_as_number
    NULL,                                     // tp_as_sequence
    NULL,                                     // tp_as_mapping
    NULL,                                     // tp_hash 
    NULL,                                     // tp_call
    NULL,                                     // tp_str
    NULL,                                     // tp_getattro
    NULL,                                     // tp_setattro
    NULL,                                     // tp_as_buffer
    Py_TPFLAGS_DEFAULT,                       // tp_flags
    "This is a supplemental class used only as a return value of Name.compare(). "
    "It encapsulate a tuple of the comparison: ordering, number of common labels, "
    "and relationship as follows:\n"
    "- ordering: relative ordering under the DNSSEC order relation\n"
    "- labels: the number of common significant labels of the two names being"
    "  compared\n"
    "- relationship: see NameComparisonResult.NameRelation\n",
    NULL,                                     // tp_traverse
    NULL,                                     // tp_clear
    NULL,                                     // tp_richcompare
    0,                                        // tp_weaklistoffset
    NULL,                                     // tp_iter
    NULL,                                     // tp_iternext
    NameComparisonResult_methods,             // tp_methods
    NULL,                                     // tp_members
    NULL,                                     // tp_getset
    NULL,                                     // tp_base
    NULL,                                     // tp_dict
    NULL,                                     // tp_descr_get
    NULL,                                     // tp_descr_set
    0,                                        // tp_dictoffset
    (initproc)NameComparisonResult_init,      // tp_init
    NULL,                                     // tp_alloc
    PyType_GenericNew,                        // tp_new
    NULL,                                     // tp_free
    NULL,                                     // tp_is_gc
    NULL,                                     // tp_bases
    NULL,                                     // tp_mro
    NULL,                                     // tp_cache
    NULL,                                     // tp_subclasses
    NULL,                                     // tp_weaklist
    NULL,                                     // tp_del
    0                                         // tp_version_tag
};

static int
NameComparisonResult_init(s_NameComparisonResult* self UNUSED_PARAM,
                          PyObject* args UNUSED_PARAM)
{
    PyErr_SetString(PyExc_NotImplementedError,
                    "NameComparisonResult can't be built directly");
    return (-1);
}

static void
NameComparisonResult_destroy(s_NameComparisonResult* self) {
    delete self->ncr;
    self->ncr = NULL;
    Py_TYPE(self)->tp_free(self);
}

static PyObject* 
NameComparisonResult_getOrder(s_NameComparisonResult* self) {
    return (Py_BuildValue("i", self->ncr->getOrder()));
}

static PyObject* 
NameComparisonResult_getCommonLabels(s_NameComparisonResult* self) {
    return (Py_BuildValue("I", self->ncr->getCommonLabels()));
}

static PyObject* 
NameComparisonResult_getRelation(s_NameComparisonResult* self) {
    return (Py_BuildValue("I", self->ncr->getRelation()));
}

// end of NameComparisonResult

// Name

class s_Name : public PyObject {
public:
    isc::dns::Name* name;
    size_t position;
};

static int Name_init(s_Name* self, PyObject* args);
static void Name_destroy(s_Name* self);

static PyObject* Name_toWire(s_Name* self, PyObject* args);
static PyObject* Name_toText(s_Name* self);
static PyObject* Name_str(PyObject* self);
static PyObject* Name_getLabelCount(s_Name* self);
static PyObject* Name_at(s_Name* self, PyObject* args);
static PyObject* Name_getLength(s_Name* self);

static PyObject* Name_compare(s_Name* self, PyObject* args);
static PyObject* Name_equals(s_Name* self, PyObject* args);

static PyObject* Name_richcmp(s_Name* self, s_Name* other, int op);
static PyObject* Name_split(s_Name* self, PyObject* args);
static PyObject* Name_reverse(s_Name* self);
static PyObject* Name_concatenate(s_Name* self, PyObject* args);
static PyObject* Name_downcase(s_Name* self);
static PyObject* Name_isWildCard(s_Name* self);

static PyMethodDef Name_methods[] = {
    { "at", reinterpret_cast<PyCFunction>(Name_at), METH_VARARGS,
      "Returns the integer value of the name data at the specified position" },
    { "get_length", reinterpret_cast<PyCFunction>(Name_getLength), METH_NOARGS,
      "Returns the length" },
    { "get_labelcount", reinterpret_cast<PyCFunction>(Name_getLabelCount), METH_NOARGS,
      "Returns the number of labels" },
    { "to_text", reinterpret_cast<PyCFunction>(Name_toText), METH_NOARGS,
      "Returns the string representation" },
    { "to_wire", reinterpret_cast<PyCFunction>(Name_toWire), METH_VARARGS,
      "Converts the Name object to wire format.\n"
      "The argument can be either a MessageRenderer or an object that "
      "implements the sequence interface. If the object is mutable "
      "(for instance a bytearray()), the wire data is added in-place.\n"
      "If it is not (for instance a bytes() object), a new object is "
      "returned" },
    { "compare", reinterpret_cast<PyCFunction>(Name_compare), METH_VARARGS,
      "Returns a NameComparisonResult object. The argument must be another Name object" },
    { "equals", reinterpret_cast<PyCFunction>(Name_equals), METH_VARARGS,
      "Returns true if the given Name object is equal to this one" },
    { "split", reinterpret_cast<PyCFunction>(Name_split), METH_VARARGS,
      "Splits the name, takes two arguments, the first is an integer "
      "specifying the first label to place in the result. The second "
      "is an integer specifying the number of labels to put in the "
      "result. Returns a new Name object" },
    { "reverse", reinterpret_cast<PyCFunction>(Name_reverse), METH_NOARGS,
      "Returns a new Name object that is the reverse of this one" },
    { "concatenate", reinterpret_cast<PyCFunction>(Name_concatenate), METH_VARARGS,
      "Concatenates the given Name object to this one and returns the "
      "result as a new Name object" },
    { "downcase", reinterpret_cast<PyCFunction>(Name_downcase), METH_NOARGS,
      "Downcases this name object (in-place). Returns a new reference to the Name." },
    { "is_wildcard", reinterpret_cast<PyCFunction>(Name_isWildCard), METH_NOARGS,
      "Returns True if the Name object represents a wildcard name." },
    { NULL, NULL, 0, NULL }
};

static PyTypeObject name_type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "libdns_python.Name",
    sizeof(s_Name),                     // tp_basicsize
    0,                                  // tp_itemsize
    (destructor)Name_destroy,           // tp_dealloc
    NULL,                               // tp_print
    NULL,                               // tp_getattr
    NULL,                               // tp_setattr
    NULL,                               // tp_reserved
    NULL,                               // tp_repr
    NULL,                               // tp_as_number
    NULL,                               // tp_as_sequence
    NULL,                               // tp_as_mapping
    NULL,                               // tp_hash 
    NULL,                               // tp_call
    Name_str,                           // tp_str
    NULL,                               // tp_getattro
    NULL,                               // tp_setattro
    NULL,                               // tp_as_buffer
    Py_TPFLAGS_DEFAULT,                 // tp_flags
    "The Name class encapsulates DNS names.\n"
    "It provides interfaces to construct a name from string or wire-format data, "
    "transform a name into a string or wire-format data, compare two names, get "
    "access to various properties of a name, etc.",
    NULL,                               // tp_traverse
    NULL,                               // tp_clear
    (richcmpfunc)Name_richcmp,          // tp_richcompare
    0,                                  // tp_weaklistoffset
    NULL,                               // tp_iter
    NULL,                               // tp_iternext
    Name_methods,                       // tp_methods
    NULL,                               // tp_members
    NULL,                               // tp_getset
    NULL,                               // tp_base
    NULL,                               // tp_dict
    NULL,                               // tp_descr_get
    NULL,                               // tp_descr_set
    0,                                  // tp_dictoffset
    (initproc)Name_init,                // tp_init
    NULL,                               // tp_alloc
    PyType_GenericNew,                  // tp_new
    NULL,                               // tp_free
    NULL,                               // tp_is_gc
    NULL,                               // tp_bases
    NULL,                               // tp_mro
    NULL,                               // tp_cache
    NULL,                               // tp_subclasses
    NULL,                               // tp_weaklist
    // Note: not sure if the following are correct.  Added them just to
    // make the compiler happy.
    NULL,                               // tp_del
    0                                   // tp_version_tag
};


static int
Name_init(s_Name* self, PyObject* args) {
    const char* s;
    PyObject* downcase = Py_False;

    // Depending on the arguments in *args, we decide which of the
    // constructors is meant. If the first argument is of type string,
    // we use the string-based constructor. If it is a bytes object,
    // we use the wire-based one.
    if (PyArg_ParseTuple(args, "s|O!", &s, &PyBool_Type, &downcase)) {
        try {
            const std::string n(s);

            self->name = new Name(n, downcase == Py_True);
            self->position = 0;
        } catch (const EmptyLabel&) {
            PyErr_SetString(po_EmptyLabel, "EmptyLabel");
            return (-1);
        } catch (const TooLongLabel&) {
            PyErr_SetString(po_TooLongLabel, "TooLongLabel");
            return (-1);
        } catch (const BadLabelType&) {
            PyErr_SetString(po_BadLabelType, "BadLabelType");
            return (-1);
        } catch (const BadEscape&) {
            PyErr_SetString(po_BadEscape, "BadEscape");
            return (-1);
        } catch (const TooLongName&) {
            PyErr_SetString(po_TooLongName, "TooLongName");
            return (-1);
        } catch (const IncompleteName&) {
            PyErr_SetString(po_IncompleteName, "IncompleteName");
            return (-1);
#ifdef CATCHMEMERR
        } catch (const std::bad_alloc&) {
            PyErr_NoMemory();
            return (-1);
#endif
        } catch (...) {
            PyErr_SetString(po_IscException, "Unexpected?!");
            return (-1);
        }
        return (0);
    }
    PyErr_Clear();

    PyObject* bytes_obj;
    const char* bytes;
    Py_ssize_t len;
    unsigned int position = 0;

    // It was not a string (see comment above), so try bytes, and
    // create with buffer object
    if (PyArg_ParseTuple(args, "O|IO!", &bytes_obj, &position,
                         &PyBool_Type, &downcase) &&
                         PyObject_AsCharBuffer(bytes_obj, &bytes, &len) != -1) {
        try {
            InputBuffer buffer(bytes, len);

            buffer.setPosition(position);
            self->name = new Name(buffer, downcase == Py_True);
            self->position = buffer.getPosition();
        } catch (const InvalidBufferPosition&) {
            PyErr_SetString(po_InvalidBufferPosition,
                            "InvalidBufferPosition");
            return (-1);
        } catch (const DNSMessageFORMERR&) {
            PyErr_SetString(po_DNSMessageFORMERR, "DNSMessageFORMERR");
            return (-1);
        } catch (...) {
            PyErr_SetString(po_IscException, "Unexpected?!");
            return (-1);
        }
        return (0);
    }

    PyErr_Clear();
    PyErr_SetString(PyExc_TypeError,
                    "No valid types in Name constructor (should be string or sequence and offset");
    return (-1);
}

static void
Name_destroy(s_Name* self) {
    delete self->name;
    self->name = NULL;
    Py_TYPE(self)->tp_free(self);
}

static PyObject*
Name_at(s_Name* self, PyObject* args) {
    unsigned int pos;
    if (!PyArg_ParseTuple(args, "I", &pos)) {
        return (NULL);
    }
    try {
        return (Py_BuildValue("I", self->name->at(pos)));
    } catch (const isc::OutOfRange&) {
        PyErr_SetString(PyExc_IndexError,
                        "name index out of range");
        return (NULL);
    }
}

static PyObject*
Name_getLength(s_Name* self) {
    return (Py_BuildValue("i", self->name->getLength()));
}

static PyObject*
Name_getLabelCount(s_Name* self) {
    return (Py_BuildValue("i", self->name->getLabelCount()));
}

static PyObject*
Name_toText(s_Name* self) {
    return (Py_BuildValue("s", self->name->toText().c_str()));
}

static PyObject*
Name_str(PyObject* self) {
    // Simply call the to_text method we already defined
    // str() is not defined in the c++ version, only to_text
    // and we already have a wrapper for that one.
    return PyObject_CallMethod(self,
                               const_cast<char*>("to_text"),
                               const_cast<char*>(""));
}

static PyObject*
Name_toWire(s_Name* self, PyObject* args) {
    PyObject* bytes;
    s_MessageRenderer* mr;
    
    if (PyArg_ParseTuple(args, "O", &bytes) && PySequence_Check(bytes)) {
        PyObject* bytes_o = bytes;
        
        OutputBuffer buffer(Name::MAX_WIRE);
        self->name->toWire(buffer);
        PyObject* name_bytes = PyBytes_FromStringAndSize(static_cast<const char*>(buffer.getData()), buffer.getLength());
        PyObject* result = PySequence_InPlaceConcat(bytes_o, name_bytes);
        // We need to release the object we temporarily created here
        // to prevent memory leak
        Py_DECREF(name_bytes);
        return (result);
    } else if (PyArg_ParseTuple(args, "O!", &messagerenderer_type, (PyObject**) &mr)) {
        self->name->toWire(*mr->messagerenderer);
        // If we return NULL it is seen as an error, so use this for
        // None returns
        Py_RETURN_NONE;
    }
    PyErr_Clear();
    PyErr_SetString(PyExc_TypeError,
                    "toWire argument must be a sequence object or a MessageRenderer");
    return (NULL);
}

static PyObject*
Name_compare(s_Name* self, PyObject* args) {
    s_Name* other;

    if (!PyArg_ParseTuple(args, "O!", &name_type, (PyObject* *) &other))
        return (NULL);

    s_NameComparisonResult* ret = PyObject_New(s_NameComparisonResult, &name_comparison_result_type);
    if (ret != NULL) {
        ret->ncr = new NameComparisonResult(
            self->name->compare(*other->name));
    }
    return (ret);
}

static PyObject* 
Name_equals(s_Name* self, PyObject* args) {
    s_Name* other;

    if (!PyArg_ParseTuple(args, "O!", &name_type, (PyObject* *) &other))
        return (NULL);

    if (self->name->equals(*other->name))
        Py_RETURN_TRUE;
    else
        Py_RETURN_FALSE;
}

static PyObject* 
Name_split(s_Name* self, PyObject* args) {
    unsigned int first, n;
    s_Name* ret = NULL;
    
    if (PyArg_ParseTuple(args, "II", &first, &n)) {
        ret = PyObject_New(s_Name, &name_type);
        if (ret != NULL) {
            ret->name = NULL;
            try {
                ret->name = new Name(self->name->split(first, n));
            } catch(const isc::OutOfRange& oor) {
                PyErr_SetString(PyExc_IndexError, oor.what());
                ret->name = NULL;
            }
            if (ret->name == NULL) {
                Py_DECREF(ret);
                return (NULL);
            }
        }
    } else if (PyArg_ParseTuple(args, "I", &n)) {
        ret = PyObject_New(s_Name, &name_type);
        if (ret != NULL) {
            ret->name = NULL;
            try {
                ret->name = new Name(self->name->split(n));
            } catch(const isc::OutOfRange& oor) {
                PyErr_SetString(PyExc_IndexError, oor.what());
                ret->name = NULL;
            }
            if (ret->name == NULL) {
                Py_DECREF(ret);
                return (NULL);
            }
        }
    }
    return (ret);
}
#include <iostream>

//
// richcmp defines the ==, !=, >, <, >= and <= operators in python
// It is translated to a function that gets 3 arguments, an object,
// an object to compare to, and an operator.
//
static PyObject* 
Name_richcmp(s_Name* self, s_Name* other, int op) {
    bool c;

    // Check for null and if the types match. If different type,
    // simply return False
    if (!other || (self->ob_type != other->ob_type)) {
        Py_RETURN_FALSE;
    }

    switch (op) {
    case Py_LT:
        c = *self->name < *other->name;
        break;
    case Py_LE:
        c = *self->name <= *other->name;
        break;
    case Py_EQ:
        c = *self->name == *other->name;
        break;
    case Py_NE:
        c = *self->name != *other->name;
        break;
    case Py_GT:
        c = *self->name > *other->name;
        break;
    case Py_GE:
        c = *self->name >= *other->name;
        break;
    default:
        PyErr_SetString(PyExc_IndexError,
                        "Unhandled rich comparison operator");
        return (NULL);
    }
    if (c) {
        Py_RETURN_TRUE;
    } else {
        Py_RETURN_FALSE;
    }
}

static PyObject*
Name_reverse(s_Name* self) {
    s_Name* ret = PyObject_New(s_Name, &name_type);

    if (ret != NULL) {
        ret->name = new Name(self->name->reverse());
        if (ret->name == NULL) {
            Py_DECREF(ret);
            return (NULL);
        }
    }
    return (ret);
}

static PyObject*
Name_concatenate(s_Name* self, PyObject* args) {
    s_Name* other;

    if (!PyArg_ParseTuple(args, "O!", &name_type, (PyObject**) &other))
        return (NULL);

    s_Name* ret = PyObject_New(s_Name, &name_type);
    if (ret != NULL) {
        try {
            ret->name = new Name(self->name->concatenate(*other->name));
        } catch (const TooLongName& tln) {
            PyErr_SetString(po_TooLongName, tln.what());
            return (NULL);
        }
    }
    return (ret);
}

static PyObject*
Name_downcase(s_Name* self) {
    self->name->downcase();
    Py_INCREF(self);
    return (self);
}

static PyObject*
Name_isWildCard(s_Name* self) {
    if (self->name->isWildcard()) {
        Py_RETURN_TRUE;
    } else {
        Py_RETURN_FALSE;
    }
}
// end of Name


// Module Initialization, all statics are initialized here
bool
initModulePart_Name(PyObject* mod) {
    // Add the classes to the module
    // We initialize the static description object with PyType_Ready(),
    // then add it to the module

    //
    // NameComparisonResult
    //
    if (PyType_Ready(&name_comparison_result_type) < 0) {
        return (false);
    }
    Py_INCREF(&name_comparison_result_type);

    // Add the enums to the module
    po_NameRelation = Py_BuildValue("{i:s,i:s,i:s,i:s}",
                                    NameComparisonResult::SUPERDOMAIN, "SUPERDOMAIN",
                                    NameComparisonResult::SUBDOMAIN, "SUBDOMAIN",
                                    NameComparisonResult::EQUAL, "EQUAL",
                                    NameComparisonResult::COMMONANCESTOR, "COMMONANCESTOR");
    addClassVariable(name_comparison_result_type, "NameRelation", po_NameRelation);

    PyModule_AddObject(mod, "NameComparisonResult",
                       reinterpret_cast<PyObject*>(&name_comparison_result_type));

    //
    // Name
    //
    
    if (PyType_Ready(&name_type) < 0) {
        return (false);
    }
    Py_INCREF(&name_type);

    // Add the constants to the module
    addClassVariable(name_type, "MAX_WIRE", Py_BuildValue("I", Name::MAX_WIRE));
    addClassVariable(name_type, "MAX_LABELS", Py_BuildValue("I", Name::MAX_LABELS));
    addClassVariable(name_type, "MAX_LABELLEN", Py_BuildValue("I", Name::MAX_LABELLEN));
    addClassVariable(name_type, "MAX_COMPRESS_POINTER", Py_BuildValue("I", Name::MAX_COMPRESS_POINTER));
    addClassVariable(name_type, "COMPRESS_POINTER_MARK8", Py_BuildValue("I", Name::COMPRESS_POINTER_MARK8));
    addClassVariable(name_type, "COMPRESS_POINTER_MARK16", Py_BuildValue("I", Name::COMPRESS_POINTER_MARK16));

    s_Name* root_name = PyObject_New(s_Name, &name_type);
    root_name->name = new Name(Name::ROOT_NAME());
    PyObject* po_ROOT_NAME = root_name;
    addClassVariable(name_type, "ROOT_NAME", po_ROOT_NAME);

    PyModule_AddObject(mod, "Name",
                       reinterpret_cast<PyObject*>(&name_type));
    

    // Add the exceptions to the module
    po_EmptyLabel = PyErr_NewException("libdns_python.EmptyLabel", NULL, NULL);
    PyModule_AddObject(mod, "EmptyLabel", po_EmptyLabel);

    po_TooLongName = PyErr_NewException("libdns_python.TooLongName", NULL, NULL);
    PyModule_AddObject(mod, "TooLongName", po_TooLongName);

    po_TooLongLabel = PyErr_NewException("libdns_python.TooLongLabel", NULL, NULL);
    PyModule_AddObject(mod, "TooLongLabel", po_TooLongLabel);

    po_BadLabelType = PyErr_NewException("libdns_python.BadLabelType", NULL, NULL);
    PyModule_AddObject(mod, "BadLabelType", po_BadLabelType);

    po_BadEscape = PyErr_NewException("libdns_python.BadEscape", NULL, NULL);
    PyModule_AddObject(mod, "BadEscape", po_BadEscape);

    po_IncompleteName = PyErr_NewException("libdns_python.IncompleteName", NULL, NULL);
    PyModule_AddObject(mod, "IncompleteName", po_IncompleteName);

    po_InvalidBufferPosition = PyErr_NewException("libdns_python.InvalidBufferPosition", NULL, NULL);
    PyModule_AddObject(mod, "InvalidBufferPosition", po_InvalidBufferPosition);

    // This one could have gone into the message_python.cc file, but is
    // already needed here.
    po_DNSMessageFORMERR = PyErr_NewException("libdns_python.DNSMessageFORMERR", NULL, NULL);
    PyModule_AddObject(mod, "DNSMessageFORMERR", po_DNSMessageFORMERR);

    return (true);
}