Added Python modules and C++ code interacting with them

Author: migueldgoncalves

README.md

@@ -1,14 +1,31 @@
 # ospf_cplusplus_python_integration
-Experiments on integration of Python extensions with C++ OSPF base implementation.
+Experiments on the integration of Python extensions with C++ OSPF base implementation.
 
 The base code is the Release 2.16 of the ospfd routing software created by John T. Moy, and described in the book [OSPF Complete Implementation](https://dl.acm.org/doi/book/10.5555/1481642).
 
 Executed in Docker containers running Ubuntu 16.04 integrated with GNS3.
 
+## Installing and running
+
+Before running the program, a configuration file `ospfd.conf` must be created or placed inside the /etc directory of the machine or Docker container running the program. A sample [configuration file](https://github.com/migueldgoncalves/ospf_cplusplus_python_integration/blob/main/ospfd.conf) is included in this repository.
+
+It is necessary to provide the absolute path to the /python directory of the source code in the line 98 of the [ospfd_linux.C](https://github.com/migueldgoncalves/ospf_cplusplus_python_integration/blob/cb2ebdbeb76b8e787ac0cff179b629237d9ff22d/linux/ospfd_linux.C#L98) file. Currently, it is assumed that the path is /ospf/python.
+
+After copying the content of this repository to the machine, it is necessary to open a terminal and go to the /linux directory of the source code. The program is compiled by running `make install`, and then executed by running `ospfd`. The command `ospfd` can be executed anywhere, and must be run as `root`.
+
+**Note**: When running Docker containers inside GNS3 networks, an /etc directory can be seen inside the directories for each container, inside the respective GNS3 network directory in the host machine. This /etc directory is different from the Ubuntu /etc directory, and is inaccessible from inside the container.
+
+## Python code
+
+Two Python modules have been created along with C++ code interacting with them, producing some output. The Python code is stored in the /python directory of this repository, while the C++ code interacting with Python is stored in the file [ospfd_linux.C](https://github.com/migueldgoncalves/ospf_cplusplus_python_integration/blob/cb2ebdbeb76b8e787ac0cff179b629237d9ff22d/linux/ospfd_linux.C#L93). The [Makefile](https://github.com/migueldgoncalves/ospf_cplusplus_python_integration/blob/main/linux/Makefile) was also updated with Python-specific flags.
+
+The experiments involve calling Python functions with different types of arguments and returns, and manipulating Python
+objects of different types.
+
 ## See also
 
 * <http://www.ospf.org> - Original source code by John T. Moy, and respective patches
 
-* <https://github.com/pfa/ospfd-diffs> - Most of required changes to run base code in Ubuntu 16.04
+* <https://github.com/pfa/ospfd-diffs> - Most of required changes to run the base code in Ubuntu 16.04
 
 * <https://github.com/migueldgoncalves/ospf_cplusplus_python_integration/releases/tag/Base_code_ubuntu_16> - Base code patched to run in Ubuntu 16, without Python code

linux/Makefile

@@ -7,6 +7,12 @@ CGI_DIR = /usr/lib/cgi-bin
 CPPFLAGS = -I. -I../src -I/usr/local/include "-DUSE_INTERP_ERRORLINE" # ErrorLine is deprecated, requires flag
 CXXFLAGS = -O -g -Wall -Woverloaded-virtual -Wcast-qual -Wuninitialized
 CFLAGS = -O -g -Wall -Woverloaded-virtual -Wcast-qual -Wuninitialized
+# Python recommended compilation flags, as obtained by "python3-config --cflags"
+PCOMPILEFLAGS = -I/usr/include/python3.5m -I/usr/include/python3.5m  -Wno-unused-result -Wsign-compare -g \
+-fstack-protector-strong -Wformat -Werror=format-security  -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes
+# Python recommended linking flags, as obtained by "python3-config --ldflags"
+PLINKFLAGS =  -L/usr/lib/python3.5/config-3.5m-x86_64-linux-gnu -L/usr/lib -lpython3.5m -lpthread -ldl  -lutil -lm  \
+-Xlinker -export-dynamic -Wl,-O1 -Wl,-Bsymbolic-functions
 
 OBJS	= asbrlsa.o \
 	  asexlsa.o \
@@ -56,8 +62,8 @@ install: ospfd ospfd_mon ospfd_browser
 	cp ospfd.tcl ${INSTALL_DIR}
 
 ospfd:	ospfd_linux.C linux.o system.o tcppkt.o ${OBJS}
-	g++ $(CXXFLAGS) $(CPPFLAGS) ospfd_linux.C linux.o system.o \
-	 tcppkt.o ${OBJS} \
+	g++ $(CXXFLAGS) $(CPPFLAGS) $(PCOMPILEFLAGS) ospfd_linux.C linux.o system.o \
+	 tcppkt.o ${OBJS} $(PLINKFLAGS) \
 	-DINSTALL_DIR=\"${INSTALL_DIR}\" -ltcl -lm -ldl -o ospfd
 
 ospfd_mon: tcppkt.o lsa_prn.o
@@ -71,11 +77,11 @@ clean:
 # Stuff to automatically maintain dependency files
 
 .c.o:
-	gcc -MD $(CFLAGS) $(CPPFLAGS) -c $<
+	gcc -MD $(CFLAGS) $(CPPFLAGS) $(PCOMPILEFLAGS) $(PLINKFLAGS) -c $<
 	@mkdir -p .depfiles ; mv $*.d .depfiles
 
 .C.o:
-	g++ -MD $(CXXFLAGS) $(CPPFLAGS) -c $<
+	g++ -MD $(CXXFLAGS) $(CPPFLAGS) $(PCOMPILEFLAGS) $(PLINKFLAGS) -c $<
 	@mkdir -p .depfiles ; mv $*.d .depfiles
 
 -include $(OBJS:%.o=.depfiles/%.d)

linux/ospfd_linux.C

@@ -17,6 +17,7 @@
  *   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+#include <Python.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
@@ -89,6 +90,81 @@ void reconfig(int)
 int main(int, char * [])
 
 {
+    // BEGINNING OF PYTHON-RELATED CODE
+
+    // Initialize the Python interpreter
+    Py_Initialize();
+    // Important: Replace with absolute path to Python files folder
+    PyRun_SimpleString("import sys\nfrom time import time,ctime; sys.path.insert(0, '/ospf/python')\nprint('Python started at',ctime(time()))\n");
+
+    // Run Python function returning a string, with no arguments
+    PyObject *pName, *pModule, *pFunc, *pArgs, *pValue;
+    pName = PyUnicode_FromString((char*)"example");
+    pModule = PyImport_Import(pName);
+    pFunc = PyObject_GetAttrString(pModule, (char*)"no_arguments");
+    pArgs = PyTuple_Pack(0, NULL);
+    pValue = PyObject_CallObject(pFunc, pArgs);
+    char* result = {};
+    result = _PyUnicode_AsString(pValue);
+    printf("%s", result);
+
+    // Run Python function returning a string, with one argument
+    pFunc = PyObject_GetAttrString(PyImport_Import(PyUnicode_FromString((char*)"example")), (char*)"string_example");
+    pArgs = PyTuple_Pack(1, PyUnicode_FromString((char*)"This experiment was successful"));
+    result = _PyUnicode_AsString(PyObject_CallObject(pFunc, pArgs));
+    printf("%s", result);
+
+    // Run Python function returning an int
+    pFunc = PyObject_GetAttrString(PyImport_Import(PyUnicode_FromString((char*)"example")), (char*)"int_example");
+    pArgs = PyTuple_Pack(1, PyLong_FromLong(10));
+    long long_result = 0;
+    long_result = PyLong_AsLong(PyObject_CallObject(pFunc, pArgs));
+    printf("%s%d%s", "The received number was: ", long_result, "\n");
+
+    // Run Python function returning a boolean
+    pFunc = PyObject_GetAttrString(PyImport_Import(PyUnicode_FromString((char*)"example")), (char*)"bool_example");
+    pArgs = PyTuple_Pack(1, Py_False);
+    bool bool_result = 0;
+    bool_result = PyBool_Check(PyObject_CallObject(pFunc, pArgs));
+    printf("%s%d%s", "The received boolean was: ", bool_result, "\n");
+
+    // Run Python function returning a bytes object
+    pFunc = PyObject_GetAttrString(PyImport_Import(PyUnicode_FromString((char*)"example")), (char*)"bytes_example");
+    pArgs = PyTuple_Pack(1, PyBytes_FromString("abcd\x61\x62\x63\x64"));
+    result = PyBytes_AsString(PyObject_CallObject(pFunc, pArgs));
+    printf("%s%s%s", "The received bytes were: ", result, "\n");
+
+    // Run Python function returning a list
+    pFunc = PyObject_GetAttrString(PyImport_Import(PyUnicode_FromString((char*)"example")), (char*)"list_example");
+    PyObject *list = PyList_New(0);
+    PyList_Append(list, PyUnicode_FromString((char*)"a"));
+    PyList_Append(list, PyUnicode_FromString((char*)"b"));
+    pArgs = PyTuple_Pack(1, list);
+    PyObject *list_result = PyObject_CallObject(pFunc, pArgs);
+    printf("%s%d%s", "The length of the received list is: ", PyList_Size(list_result), "\n");
+    const char *element_1 = PyUnicode_AS_DATA(PyList_GetItem(list_result, 0));
+    const char *element_2 = PyUnicode_AS_DATA(PyList_GetItem(list_result, 1));
+    const char *element_3 = PyUnicode_AS_DATA(PyList_GetItem(list_result, 2));
+    printf("%s%s%s%s%s", "The elements of the received list are: ", element_1, element_2, element_3, "\n");
+
+    // Create a custom data object, pack it to bytes, and unpack the bytes back to the original data object
+    PyObject *module = PyImport_ImportModule((char*)"data_object");
+    PyObject *custom_class = PyObject_GetAttrString(module, (char*)"ExtensionAbr");
+    PyObject *instance = PyObject_CallObject(custom_class, PyTuple_Pack(0, NULL));
+    PyObject *metric = PyLong_FromLong(10);
+    PyObject *neighbor_router_id = PyUnicode_FromString((char*)"1.1.1.1");
+    PyObject_CallMethodObjArgs(instance, PyUnicode_FromString((char*)"add_abr_info"), metric, neighbor_router_id, NULL);
+    PyObject *printed_object = PyObject_CallMethodObjArgs(instance, PyUnicode_FromString((char*)"__str__"), NULL);
+    printf("%s%s%s", "The printed custom object is: ", _PyUnicode_AsString(printed_object), "\n");
+    PyObject *object_bytes = PyObject_CallMethodObjArgs(instance, PyUnicode_FromString((char*)"pack_lsa_body"), NULL);
+    PyObject *restored_instance = PyObject_CallMethodObjArgs(instance, PyUnicode_FromString((char*)"unpack_lsa_body"), object_bytes, NULL);
+    printed_object = PyObject_CallMethodObjArgs(restored_instance, PyUnicode_FromString((char*)"__str__"), NULL);
+    printf("%s%s%s", "The restored printed custom object is: ", _PyUnicode_AsString(printed_object), "\n");
+
+    Py_Finalize();
+
+    // END OF PYTHON-RELATED CODE
+
     int n_fd;
     itimerval itim;
     fd_set fdset;

ospfd.conf

@@ -0,0 +1,5 @@
+routerid 1.1.1.1
+area 0.0.0.0
+interface eth0 10
+area 0.0.0.0
+interface eth1 10

python/data_object.py

@@ -0,0 +1,70 @@
+import ipaddress
+import struct
+
+#  > - Big-endian
+#  L - Unsigned long (4 bytes) - struct.pack("> L", 1) -> b'\x00\x00\x00\x01
+BASE_FORMAT_STRING = "> L L"  # Determines the format of the byte object to be created
+
+
+class ExtensionAbr:  # Adapted from https://github.com/migueldgoncalves/ospf-multiarea-arbitrary-topology
+
+    def __init__(self):
+        self.abr_list = []  # 8 bytes / ABR
+
+    #  Adds data for one ABR to the LSA body
+    def add_abr_info(self, metric, neighbor_router_id):
+        abr_info = [metric, neighbor_router_id]
+        if not self.has_abr_info(neighbor_router_id):
+            self.abr_list.append(abr_info)
+
+    def has_abr_info(self, neighbor_router_id):
+        has_abr_info = False
+        for abr_info in self.abr_list:
+            if abr_info[1] == neighbor_router_id:
+                has_abr_info = True
+        return has_abr_info
+
+    def get_abr_info(self, neighbor_router_id):
+        for abr_info in self.abr_list:
+            if abr_info[1] == neighbor_router_id:
+                return abr_info
+        return None
+
+    #  Deletes data for one ABR from the LSA body
+    def delete_abr_info(self, neighbor_router_id):
+        for abr_info in self.abr_list:
+            if abr_info[1] == neighbor_router_id:
+                self.abr_list.remove(abr_info)
+
+    #  Creates byte object suitable to be sent and recognized as the body of an ABR-LSA of the OSPF extension
+    def pack_lsa_body(self):
+        body_bytes = b''
+        for abr_info in self.abr_list:
+            metric = int(abr_info[0])
+            decimal_neighbor_router_id = self.ipv4_to_decimal(abr_info[1])
+            body_bytes += struct.pack(BASE_FORMAT_STRING, metric, decimal_neighbor_router_id)
+        return body_bytes
+
+    #  Converts byte stream to body of an ABR-LSA of the OSPF extension
+    def unpack_lsa_body(self, body_bytes):
+        extension_abr_lsa = ExtensionAbr()
+        while len(body_bytes) > 0:
+            abr_parameters = struct.unpack(BASE_FORMAT_STRING, body_bytes[:8])
+            metric = int(abr_parameters[0])
+            neighbor_router_id = self.decimal_to_ipv4(abr_parameters[1])
+            extension_abr_lsa.add_abr_info(metric, neighbor_router_id)
+            body_bytes = body_bytes[8:]
+        return extension_abr_lsa
+
+    #  Converts IPv4 addresses to numbers between 0 and 4294967295
+    @staticmethod
+    def ipv4_to_decimal(ip_address):
+        return int(ipaddress.IPv4Address(ip_address))
+
+    #  Converts numbers between 0 and 4294967295 to IPv4 addresses
+    @staticmethod
+    def decimal_to_ipv4(decimal):
+        return str(ipaddress.IPv4Address(int(decimal)))
+
+    def __str__(self):
+        return str({"ABRs": self.abr_list})

python/example.py

@@ -0,0 +1,18 @@
+def no_arguments():
+    return "This function receives no arguments\n"
+
+def string_example(input_string):
+    return "This is the string supplied to Python: " + input_string + "\n"
+
+def int_example(input_int):
+    return input_int + 1
+
+def bool_example(input_bool):
+    return not input_bool
+
+def bytes_example(input_bytes):
+    return input_bytes + b'\x31\x32\x33\x34\x01\x02\x31'
+
+def list_example(input_list):
+    input_list.append("c")
+    return input_list