knot-dns/python/libknot

Libknot API in Python

A Python interface for managing the Knot DNS daemon.

Table of contents

• Introduction
• Control module
  • Usage
  • Example
• Probe module
  • Usage
  • Example
• Dname module
  • Usage
  • Example

Introduction

If the shared libknot.so library isn't available in the library search path, it's necessary to load the library first, e.g.:

import libknot
libknot.Knot("/usr/lib/libknot.so")

Control module

Using this module it's possible to create scripts for efficient tasks that would require complex shell scripts with multiple calls of knotc. For communication with the daemon it uses the same mechanism as the knotc utility, i.e. communication via a Unix socket.

The module API is stored in libknot.control.

Using the Control module

The module usage consists of several steps:

• Initialization and connection to the daemon control socket.
• One or more control operations. An operation is called by sending a command with optional data to the daemon. The operation result has to be received afterwards.
• Closing the connection and deinitialization.

Control module example

import json
import libknot.control

# Initialization
ctl = libknot.control.KnotCtl()
ctl.connect("/var/run/knot/knot.sock")
ctl.set_timeout(60)

try:
    # Operation without parameters
    ctl.send_block(cmd="conf-begin")
    resp = ctl.receive_block()

    # Operation with parameters
    ctl.send_block(cmd="conf-set", section="zone", item="domain", data="test")
    resp = ctl.receive_block()

    ctl.send_block(cmd="conf-commit")
    resp = ctl.receive_block()

    # Operation with a result displayed in JSON format
    ctl.send_block(cmd="conf-read", section="zone", item="domain")
    resp = ctl.receive_block()
    print(json.dumps(resp, indent=4))
except libknot.control.KnotCtlError as exc:
    # Print libknot error
    print(exc)
finally:
    # Deinitialization
    ctl.send(libknot.control.KnotCtlType.END)
    ctl.close()

    # List configured zones (including catalog member ones)
    ctl.send_block(cmd="conf-list", flags="z")
    resp = ctl.receive_block()
    for zone in resp['zone']:
        print(zone)

    # Print expirations as unixtime for all secondary zones
    ctl.send_block(cmd="zone-status", flags="u")
    resp = ctl.receive_block()
    for zone in resp:
        if resp[zone]["role"] == "master":
            continue

        expiration = resp[zone]["expiration"]
        if expiration == "-":
            print("Zone %s not loaded" % zone)
        else:
            print("Zone %s expires at %s" % (zone, resp[zone]["expiration"]))

Probe module

Using this module it's possible to receive traffic data from a running daemon with active probe module.

The module API is stored in libknot.probe.

Using the Probe module

The module usage consists of several steps:

• Initialization of one or more probe channels
• Periodical receiving of data units from the channels and data processing

Probe module example

import libknot.probe

# Initialization of the first probe channel stored in `/run/knot`
probe = libknot.probe.KnotProbe("/run/knot", 1)

# Array for storing up to 8 data units
data = libknot.probe.KnotProbeDataArray(8)
while (True):
    # Receiving data units with timeout of 1000 ms
    if probe.consume(data, 1000) > 0:
        # Printing received data units in the default format
        for item in data:
            print(item)

Dname module

This module provides a few dname-related operations.

Using the Dname module

The dname object is initialized from a string with textual dname. Then the dname can be reformatted to wire format or back to textual format.

Dname module example

import libknot.dname

dname1 = libknot.dname.KnotDname("knot-dns.cz")
print("%s: wire: %s size: %u" % (dname1.str(), dname1.wire(), dname1.size()))

dname2 = libknot.dname.KnotDname("e\\120ample.c\om.")
print("%s: wire: %s size: %u" % (dname2.str(), dname2.wire(), dname2.size()))

dname3 = libknot.dname.KnotDname(dname_wire=b'\x02cz\x00')
print("%s: wire: %s size: %u" % (dname3.str(), dname3.wire(), dname3.size()))

knot-dns.cz.: wire: b'\x08knot-dns\x02cz\x00' size: 13
example.com.: wire: b'\x07example\x03com\x00' size: 13
cz.: wire: b'\x02cz\x00' size: 4