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diff --git a/external/unbound/pythonmod/doc/examples/example4.rst b/external/unbound/pythonmod/doc/examples/example4.rst new file mode 100644 index 000000000..6cc484797 --- /dev/null +++ b/external/unbound/pythonmod/doc/examples/example4.rst @@ -0,0 +1,164 @@ +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 |