+++ /dev/null
-DNS-based language dictionary
-===============================
-
-This example shows how to create a simple language dictionary based on **DNS**
-service within 15 minutes. The translation will be performed using TXT resource records.
-
-Key parts
------------
-
-Initialization
-~~~~~~~~~~~~~~~~~~~~~~~
-On **init()** module loads dictionary from a text file containing records in ``word [tab] translation`` format.
-::
-
- def init(id, cfg):
- log_info("pythonmod: dict init")
- f = open("examples/dict_data.txt", "r")
- ...
-
-The suitable file can be found at http://slovnik.zcu.cz
-
-DNS query and word lookup
-~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Let's define the following format od DNS queries: ``word1[.]word2[.] ... wordN[.]{en,cs}[._dict_.cz.]``.
-Word lookup is done by simple ``dict`` lookup from broken DNS request.
-Query name is divided into a list of labels. This list is accesible as qname_list attribute.
-::
-
- aword = ' '.join(qstate.qinfo.qname_list[0:-4]) #skip last four labels
- adict = qstate.qinfo.qname_list[-4] #get 4th label from the end
-
- words = [] #list of words
- if (adict == "en") and (aword in en_dict):
- words = en_dict[aword]
-
- if (adict == "cs") and (aword in cz_dict):
- words = cz_dict[aword] # CS -> EN
-
-In the first step, we get a string in the form: ``word1[space]word2[space]...word[space]``.
-In the second assignment, fourth label from the end is obtained. This label should contains *"cs"* or *"en"*.
-This label determines the direction of translation.
-
-
-Forming of a DNS reply
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-DNS reply is formed only on valid match and added as TXT answer.
-::
-
- msg = DNSMessage(qstate.qinfo.qname_str, RR_TYPE_TXT, RR_CLASS_IN, PKT_AA)
-
- for w in words:
- msg.answer.append("%s 300 IN TXT \"%s\"" % (qstate.qinfo.qname_str, w.replace("\"", "\\\"")))
-
- if not msg.set_return_msg(qstate):
- qstate.ext_state[id] = MODULE_ERROR
- return True
-
- qstate.return_rcode = RCODE_NOERROR
- qstate.ext_state[id] = MODULE_FINISHED
- return True
-
-In the first step, a :class:`DNSMessage` instance is created for a given query *(type TXT)*.
-The fourth argument specifies the flags *(authoritative answer)*.
-In the second step, we append TXT records containing the translation *(on the right side of RR)*.
-Then, the response is finished and ``qstate.return_msg`` contains new response.
-If no error, the module sets :attr:`module_qstate.return_rcode` and :attr:`module_qstate.ext_state`.
-
-**Steps:**
-
-1. create :class:`DNSMessage` instance
-2. append TXT records containing the translation
-3. set response to ``qstate.return_msg``
-
-Testing
--------
-
-Run the Unbound server:
-
-``root@localhost>unbound -dv -c ./test-dict.conf``
-
-In case you use own configuration file, don't forget to enable Python module::
-
- module-config: "validator python iterator"
-
-and use valid script path::
-
- python-script: "./examples/dict.py"
-
-The translation from english word *"a bar fly"* to Czech can be done by doing:
-
-``>>>dig TXT @127.0.0.1 a.bar.fly.en._dict_.cz``
-
-::
-
- ; (1 server found)
- ;; global options: printcmd
- ;; Got answer:
- ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48691
- ;; flags: aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
-
- ;; QUESTION SECTION:
- ;a.bar.fly.en._dict_.cz. IN TXT
-
- ;; ANSWER SECTION:
- a.bar.fly.en._dict_.cz. 300 IN TXT "barov\253 povale\232"
-
- ;; Query time: 5 msec
- ;; SERVER: 127.0.0.1#53(127.0.0.1)
- ;; WHEN: Mon Jan 01 17:44:18 2009
- ;; MSG SIZE rcvd: 67
-
-``>>>dig TXT @127.0.0.1 nic.cs._dict_.cz``
-::
-
- ; <<>> DiG 9.5.0-P2 <<>> TXT @127.0.0.1 nic.cs._dict_.cz
- ; (1 server found)
- ;; global options: printcmd
- ;; Got answer:
- ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 58710
- ;; flags: aa rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0
-
- ;; QUESTION SECTION:
- ;nic.cs._dict_.cz. IN TXT
-
- ;; ANSWER SECTION:
- nic.cs._dict_.cz. 300 IN TXT "aught"
- nic.cs._dict_.cz. 300 IN TXT "naught"
- nic.cs._dict_.cz. 300 IN TXT "nihil"
- nic.cs._dict_.cz. 300 IN TXT "nix"
- nic.cs._dict_.cz. 300 IN TXT "nothing"
- nic.cs._dict_.cz. 300 IN TXT "zilch"
-
- ;; Query time: 0 msec
- ;; SERVER: 127.0.0.1#53(127.0.0.1)
- ;; WHEN: Mon Jan 01 17:45:39 2009
- ;; MSG SIZE rcvd: 143
-
-Proof that the unbound still works as resolver.
-
-``>>>dig A @127.0.0.1 www.nic.cz``
-::
-
- ; (1 server found)
- ;; global options: printcmd
- ;; Got answer:
- ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19996
- ;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 3, ADDITIONAL: 5
-
- ;; QUESTION SECTION:
- ;www.nic.cz. IN A
-
- ;; ANSWER SECTION:
- www.nic.cz. 1662 IN A 217.31.205.50
-
- ;; AUTHORITY SECTION:
- ...
-
-Complete source code
---------------------
-
-.. literalinclude:: ../../examples/dict.py
- :language: python
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