netdiff 1.0

Python library for parsing network topology data (eg: dynamic routing protocols, NetJSON, CNML) and detect changes.

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Netdiff is a simple abstraction layer for parsing network topology data of open source dynamic routing protocols or any other networking software which has knowledge about the topology of a network.

Its goal is to allow applications like openwisp-network-topology to collect, visualize and monitor network topology data without having to deal with the details of each networking software from which the data is retrieved.

Features:

• parse different formats

• detect changes in two topologies

• return consistent NetJSON output

• uses the popular networkx library under the hood

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Table of Contents:

• Install stable version from pypi

• Install development version

• Basic Usage Example

• Parsers

  • Initialization arguments

  • Initialization examples

• NetJSON output

• Exceptions

  • ConversionException

  • ParserError

  • NetJsonError

  • TopologyRetrievalError

• Specialized features

• Known Issues

• Running tests

• Contributing

• Support

• Changelog

• License

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Install stable version from pypi

Install from pypi:

pip install netdiff

Install development version

Install tarball:

pip install https://github.com/openwisp/netdiff/tarball/master

Alternatively you can install via pip using git:

pip install -e git+git://github.com/openwisp/netdiff#egg=netdiff

If you want to contribute, install your cloned fork:

git clone [e-mail]:<your_fork>/netdiff.git
cd netdiff
python setup.py develop

Basic Usage Example

Calculate diff of an OLSR 0.6.x topology:

from netdiff import OlsrParser
from netdiff import diff

old = OlsrParser(file='./stored-olsr.json')
new = OlsrParser(url='http://127.0.0.1:9090')
diff(old, new)

In alternative, you may also use the subtraction operator:

from netdiff import OlsrParser
from netdiff import diff

old = OlsrParser(file='./stored-olsr.json')
new = OlsrParser(url='http://127.0.0.1:9090')
old - new

The output will be an ordered dictionary with three keys:

• added

• removed

• changed

Each key will contain a dict compatible with the NetJSON NetworkGraph format representing respectively:

• the nodes and links that have been added to the topology

• the nodes and links that have been removed from the topology

• the nodes and links that are present in both topologies but their attributes have changed

If no changes are present, keys will contain None.

So if between old and new there are no changes, the result will be:

{
    "added": None
    "removed": None,
    "changed": None
}

While if there are changes, the result will look like:

{
    "added": {
        "type": "NetworkGraph",
        "protocol": "OLSR",
        "version": "0.6.6",
        "revision": "5031a799fcbe17f61d57e387bc3806de",
        "metric": "ETX",
        "nodes": [
            {
                "id": "10.150.0.7",
                "label": "Node A",
                "local_addresses": [],
                "properties": {}
            },
            {
                "id": "10.150.0.6",
                "label": "Node B",
                "local_addresses": ["10.56.2.1"],
                "properties": {
                    "hostname": "nodeb.lan"
                }
            }
        ],
        "links": [
            {
                "source": "10.150.0.3",
                "target": "10.150.0.7",
                "cost": 1.50390625,
                "cost_text", "",
                "properties": {}
            },
            {
                "source": "10.150.0.3",
                "target": "10.150.0.6",
                "cost": 1.0
                "cost_text", "",
                "properties": {}
            }
        ]
    },
    "removed": {
        "type": "NetworkGraph",
        "protocol": "OLSR",
        "version": "0.6.6",
        "revision": "5031a799fcbe17f61d57e387bc3806de",
        "metric": "ETX",
        "nodes": [
            {
                "id": "10.150.0.8",
                "label": "Node C",
                "local_addresses": [],
                "properties": {}
            }
        ],
        "links": [
            {
                "source": "10.150.0.7",
                "target": "10.150.0.8",
                "cost": 1.0
                "cost_text", "",
                "properties": {}
            }
        ]
    },
    "changed": {
        "type": "NetworkGraph",
        "protocol": "OLSR",
        "version": "0.6.6",
        "revision": "5031a799fcbe17f61d57e387bc3806de",
        "metric": "ETX",
        "nodes": [],
        "links": [
            {
                "source": "10.150.0.3",
                "target": "10.150.0.2",
                "cost": 1.0
                "cost_text", "",
                "properties": {}
            }
        ]
    }
}

Parsers

Parsers are classes that extend netdiff.base.BaseParser and implement a parse method which is in charge of converting a python data structure into networkx.Graph object and return the result.

Parsers also have a json method which returns valid NetJSON output.

The available parsers are:

• netdiff.OlsrParser: parser for the olsrd jsoninfo plugin or the older txtinfo plugin

• netdiff.BatmanParser: parser for the batman-advanced alfred tool (supports also the legacy txtinfo format inherited from olsrd)

• netdiff.Bmx6Parser: parser for the BMX6 b6m tool

• netdiff.CnmlParser: parser for CNML 0.1

• netdiff.NetJsonParser: parser for the NetJSON NetworkGraph format

• netdiff.OpenvpnParser: parser for the OpenVPN status file

Initialization arguments

Data can be supplied in 3 different ways, in the following order of precedence:

• data: dict or str representing the topology/graph

• url: URL to fetch data from

• file: file path to retrieve data from

Other available arguments:

• timeout: integer representing timeout in seconds for HTTP or telnet requests, defaults to None

• verify: boolean indicating to the request library whether to do SSL certificate verification or not

• directed: boolean that enables the use of a directed graph (networkx.DiGraph), defaults to False

Initialization examples

Local file example:

from netdiff import BatmanParser
BatmanParser(file='./my-stored-topology.json')

HTTP example:

from netdiff import NetJsonParser
url = 'https://raw.githubusercontent.com/interop-dev/netjson/master/examples/network-graph.json'
NetJsonParser(url=url)

Telnet example with timeout:

from netdiff import OlsrParser
OlsrParser(url='telnet://127.0.1', timeout=5)

HTTPS example with self-signed SSL certificate using verify=False:

from netdiff import NetJsonParser
OlsrParser(url='https://myserver.mydomain.com/topology.json', verify=False)

NetJSON output

Netdiff parsers can return a valid NetJSON NetworkGraph object:

from netdiff import OlsrParser

olsr = OlsrParser(url='telnet://127.0.0.1:9090')

# will return a dict
olsr.json(dict=True)

# will return a JSON formatted string
print(olsr.json(indent=4))

Output:

{
    "type": "NetworkGraph",
    "protocol": "OLSR",
    "version": "0.6.6",
    "revision": "5031a799fcbe17f61d57e387bc3806de",
    "metric": "ETX",
    "nodes": [
        {
            "id": "10.150.0.3"
        },
        {
            "id": "10.150.0.2"
        },
        {
            "id": "10.150.0.4"
        }
    ],
    "links": [
        {
            "source": "10.150.0.3",
            "target": "10.150.0.2",
            "cost": 2.4
        },
        {
            "source": "10.150.0.3",
            "target": "10.150.0.4",
            "cost": 1.0
        }
    ]
}

Exceptions

All the exceptions are subclasses of netdiff.exceptions.NetdiffException.

ConversionException

netdiff.exceptions.ConversionException

Raised when netdiff can’t recognize the format passed to the parser.

Not necessarily an error, should be caught and managed in order to support additional formats.

The data which was retrieved from network/storage can be accessed via the “data” attribute, eg:

def to_python(self, data):
    try:
        return super().to_python(data)
    except ConversionException as e:
        return self._txtinfo_to_jsoninfo(e.data)

ParserError

netdiff.exceptions.ParserError

Raised when the format is recognized but the data is invalid.

NetJsonError

netdiff.exceptions.NetJsonError

Raised when the json method of netdiff.parsers.BaseParser does not have enough data to be compliant with the NetJSON NetworkGraph specification.

TopologyRetrievalError

netdiff.exceptions.TopologyRetrievalError

Raised when it is not possible to retrieve the topology data (eg: the URL might be temporary unreachable).

Specialized features

OpenVPN

By default, the OpenVPN parser uses the common name to identify a client, this was chosen because if the public IP address is used, the same client will not be recognized if it connects with a different IP address (very probable since many ISPs use dynamic public IP addresses).

This does not work when the vpn server configuration allows different clients to use the same common name (which is generally not recommended anyway).

If you need to support legacy systems which are configured with the OpenVPN duplicate-cn feature enabled, you can pass duplicate_cn=True during the initialization of OpenvpnParser. This will change the behavior of the parser so that each client is identified by their common name and IP address (and additionally the port used if there are multiple clients with same common name and IP).

Known Issues

ConnectionError: BadStatusLine

If you get a similar error when performing a request to the jsoninfo plugin of olsrd (version 0.6 to 0.9) chances are high that http headers are disabled.

To fix it turn on http headers in your olsrd configuration file, eg:

LoadPlugin "olsrd_jsoninfo.so.0.0"
{
    PlParam "httpheaders" "yes"   # add this line
    PlParam "Port" "9090"
    PlParam "accept" "0.0.0.0"
}

Running tests

Install your forked repo:

git clone git://github.com/<your_fork>/netdiff
cd netdiff/
python setup.py develop

Install test requirements:

pip install -r requirements-test.txt

Run tests with:

./runtests.py
./run-qa-checks

Alternatively, you can use the nose2 command (which has a ton of available options):

nose2
nose2 tests.test_olsr  # run only olsr related tests
nose2 tests/test_olsr.py  # variant form of the previous command
nose2 tests.test_olsr:TestOlsrParser  # variant form of the previous command
nose2 tests.test_olsr:TestOlsrParser.test_parse  # run specific test

See test coverage with:

coverage run --source=netdiff runtests.py && coverage report

Contributing

Please refer to the OpenWISP contributing guidelines.

Support

See OpenWISP Support Channels.

Changelog

See CHANGES.

License

See LICENSE.