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These files were pulled from the 1.6.3 release tarball. This new version builds against OpenSSL version 1.1 which will be the default in the new Debian Stable which is due to be released RealSoonNow (tm).
300 lines
10 KiB
ReStructuredText
300 lines
10 KiB
ReStructuredText
Inplace callbacks
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=================
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This example shows how to register and use inplace callback functions. These
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functions are going to be called just before unbound replies back to a client.
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They can perform certain actions without interrupting unbound's execution flow
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(e.g. add/remove EDNS options, manipulate the reply).
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Two different scenarios will be shown:
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- If answering from cache and the client used EDNS option code ``65002`` we
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will answer with the same code but with data ``0xdeadbeef``;
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- When answering with a SERVFAIL we also add an empty EDNS option code
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``65003``.
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Key parts
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~~~~~~~~~
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This example relies on the following functionalities:
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Registering inplace callback functions
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--------------------------------------
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There are four types of inplace callback functions:
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- `inplace callback reply functions`_
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- `inplace callback reply_cache functions`_
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- `inplace callback reply_local functions`_
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- `inplace callback reply_servfail functions`_
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Inplace callback reply functions
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................................
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Called when answering with a *resolved* query.
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The callback function's prototype is the following:
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.. code-block:: python
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def inplace_reply_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
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"""Function that will be registered as an inplace callback function.
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It will be called when answering with a resolved query.
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:param qinfo: query_info struct;
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:param qstate: module qstate. It contains the available opt_lists; It
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SHOULD NOT be altered;
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:param rep: reply_info struct;
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:param rcode: return code for the query;
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:param edns: edns_data to be sent to the client side. It SHOULD NOT be
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altered;
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:param opt_list_out: the list with the EDNS options that will be sent as a
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reply. It can be populated with EDNS options;
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:param region: region to allocate temporary data. Needs to be used when we
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want to append a new option to opt_list_out.
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:return: True on success, False on failure.
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"""
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.. note:: The function's name is irrelevant.
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We can register such function as:
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.. code-block:: python
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if not register_inplace_cb_reply(inplace_reply_callback, env, id):
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log_info("python: Could not register inplace callback function.")
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Inplace callback reply_cache functions
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......................................
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Called when answering *from cache*.
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The callback function's prototype is the following:
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.. code-block:: python
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def inplace_cache_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
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"""Function that will be registered as an inplace callback function.
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It will be called when answering from the cache.
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:param qinfo: query_info struct;
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:param qstate: module qstate. None;
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:param rep: reply_info struct;
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:param rcode: return code for the query;
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:param edns: edns_data sent from the client side. The list with the EDNS
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options is accesible through edns.opt_list. It SHOULD NOT be
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altered;
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:param opt_list_out: the list with the EDNS options that will be sent as a
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reply. It can be populated with EDNS options;
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:param region: region to allocate temporary data. Needs to be used when we
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want to append a new option to opt_list_out.
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:return: True on success, False on failure.
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"""
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.. note:: The function's name is irrelevant.
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We can register such function as:
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.. code-block:: python
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if not register_inplace_cb_reply_cache(inplace_cache_callback, env, id):
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log_info("python: Could not register inplace callback function.")
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Inplace callback reply_local functions
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......................................
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Called when answering with *local data* or a *Chaos(CH) reply*.
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The callback function's prototype is the following:
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.. code-block:: python
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def inplace_local_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
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"""Function that will be registered as an inplace callback function.
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It will be called when answering from local data.
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:param qinfo: query_info struct;
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:param qstate: module qstate. None;
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:param rep: reply_info struct;
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:param rcode: return code for the query;
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:param edns: edns_data sent from the client side. The list with the
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EDNS options is accesible through edns.opt_list. It
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SHOULD NOT be altered;
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:param opt_list_out: the list with the EDNS options that will be sent as a
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reply. It can be populated with EDNS options;
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:param region: region to allocate temporary data. Needs to be used when we
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want to append a new option to opt_list_out.
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:return: True on success, False on failure.
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"""
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.. note:: The function's name is irrelevant.
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We can register such function as:
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.. code-block:: python
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if not register_inplace_cb_reply_local(inplace_local_callback, env, id):
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log_info("python: Could not register inplace callback function.")
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Inplace callback reply_servfail functions
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.........................................
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Called when answering with *SERVFAIL*.
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The callback function's prototype is the following:
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.. code-block:: python
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def inplace_servfail_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
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"""Function that will be registered as an inplace callback function.
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It will be called when answering with SERVFAIL.
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:param qinfo: query_info struct;
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:param qstate: module qstate. If not None the relevant opt_lists are
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available here;
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:param rep: reply_info struct. None;
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:param rcode: return code for the query. LDNS_RCODE_SERVFAIL;
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:param edns: edns_data to be sent to the client side. If qstate is None
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edns.opt_list contains the EDNS options sent from the client
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side. It SHOULD NOT be altered;
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:param opt_list_out: the list with the EDNS options that will be sent as a
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reply. It can be populated with EDNS options;
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:param region: region to allocate temporary data. Needs to be used when we
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want to append a new option to opt_list_out.
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:return: True on success, False on failure.
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"""
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.. note:: The function's name is irrelevant.
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We can register such function as:
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.. code-block:: python
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if not register_inplace_cb_reply_servfail(inplace_servfail_callback, env, id):
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log_info("python: Could not register inplace callback function.")
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Testing
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~~~~~~~
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Run the Unbound server: ::
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root@localhost$ unbound -dv -c ./test-inplace_callbacks.conf
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In case you use your own configuration file, don't forget to enable the Python
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module::
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module-config: "validator python iterator"
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and use a valid script path ::
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python-script: "./examples/inplace_callbacks.py"
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On the first query for the nlnetlabs.nl A record we get no EDNS option back:
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::
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root@localhost$ dig @localhost nlnetlabs.nl +ednsopt=65002
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; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost nlnetlabs.nl +ednsopt=65002
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48057
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;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 3
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;; OPT PSEUDOSECTION:
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; EDNS: version: 0, flags:; udp: 4096
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;; QUESTION SECTION:
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;nlnetlabs.nl. IN A
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;; ANSWER SECTION:
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nlnetlabs.nl. 10200 IN A 185.49.140.10
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;; AUTHORITY SECTION:
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nlnetlabs.nl. 10200 IN NS ns.nlnetlabs.nl.
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nlnetlabs.nl. 10200 IN NS sec2.authdns.ripe.net.
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nlnetlabs.nl. 10200 IN NS anyns.pch.net.
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nlnetlabs.nl. 10200 IN NS ns-ext1.sidn.nl.
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;; ADDITIONAL SECTION:
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ns.nlnetlabs.nl. 10200 IN A 185.49.140.60
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ns.nlnetlabs.nl. 10200 IN AAAA 2a04:b900::8:0:0:60
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;; Query time: 813 msec
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;; SERVER: 127.0.0.1#53(127.0.0.1)
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;; WHEN: Mon Dec 05 16:15:32 CET 2016
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;; MSG SIZE rcvd: 204
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When we issue the same query again we get a cached response and the expected
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``65002: 0xdeadbeef`` EDNS option:
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::
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root@localhost$ dig @localhost nlnetlabs.nl +ednsopt=65002
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; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost nlnetlabs.nl +ednsopt=65002
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26489
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;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 3
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;; OPT PSEUDOSECTION:
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; EDNS: version: 0, flags:; udp: 4096
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; OPT=65002: de ad be ef ("....")
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;; QUESTION SECTION:
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;nlnetlabs.nl. IN A
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;; ANSWER SECTION:
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nlnetlabs.nl. 10197 IN A 185.49.140.10
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;; AUTHORITY SECTION:
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nlnetlabs.nl. 10197 IN NS ns.nlnetlabs.nl.
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nlnetlabs.nl. 10197 IN NS sec2.authdns.ripe.net.
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nlnetlabs.nl. 10197 IN NS anyns.pch.net.
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nlnetlabs.nl. 10197 IN NS ns-ext1.sidn.nl.
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;; ADDITIONAL SECTION:
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ns.nlnetlabs.nl. 10197 IN AAAA 2a04:b900::8:0:0:60
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ns.nlnetlabs.nl. 10197 IN A 185.49.140.60
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;; Query time: 0 msec
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;; SERVER: 127.0.0.1#53(127.0.0.1)
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;; WHEN: Mon Dec 05 16:50:04 CET 2016
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;; MSG SIZE rcvd: 212
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By issuing a query for a bogus domain unbound replies with SERVFAIL and an
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empty EDNS option code ``65003``. *For this example to work unbound needs to be
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validating*:
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::
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root@localhost$ dig @localhost bogus.nlnetlabs.nl txt
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; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost bogus.nlnetlabs.nl txt
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; (1 server found)
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;; global options: +cmd
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;; Got answer:
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;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 19865
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;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
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;; OPT PSEUDOSECTION:
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; EDNS: version: 0, flags:; udp: 4096
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; OPT=65003
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;; QUESTION SECTION:
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;bogus.nlnetlabs.nl. IN TXT
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;; Query time: 11 msec
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;; SERVER: 127.0.0.1#53(127.0.0.1)
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;; WHEN: Mon Dec 05 17:06:01 CET 2016
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;; MSG SIZE rcvd: 51
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Complete source code
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~~~~~~~~~~~~~~~~~~~~
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.. literalinclude:: ../../examples/inplace_callbacks.py
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:language: python
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