mirror of
https://codeberg.org/anoncontributorxmr/monero.git
synced 2024-12-05 21:40:50 +00:00
300 lines
10 KiB
ReStructuredText
300 lines
10 KiB
ReStructuredText
|
Inplace callbacks
|
||
|
=================
|
||
|
|
||
|
This example shows how to register and use inplace callback functions. These
|
||
|
functions are going to be called just before unbound replies back to a client.
|
||
|
They can perform certain actions without interrupting unbound's execution flow
|
||
|
(e.g. add/remove EDNS options, manipulate the reply).
|
||
|
|
||
|
Two different scenarios will be shown:
|
||
|
|
||
|
- If answering from cache and the client used EDNS option code ``65002`` we
|
||
|
will answer with the same code but with data ``0xdeadbeef``;
|
||
|
- When answering with a SERVFAIL we also add an empty EDNS option code
|
||
|
``65003``.
|
||
|
|
||
|
|
||
|
Key parts
|
||
|
~~~~~~~~~
|
||
|
|
||
|
This example relies on the following functionalities:
|
||
|
|
||
|
|
||
|
Registering inplace callback functions
|
||
|
--------------------------------------
|
||
|
|
||
|
There are four types of inplace callback functions:
|
||
|
|
||
|
- `inplace callback reply functions`_
|
||
|
- `inplace callback reply_cache functions`_
|
||
|
- `inplace callback reply_local functions`_
|
||
|
- `inplace callback reply_servfail functions`_
|
||
|
|
||
|
|
||
|
Inplace callback reply functions
|
||
|
................................
|
||
|
|
||
|
Called when answering with a *resolved* query.
|
||
|
|
||
|
The callback function's prototype is the following:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
def inplace_reply_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
|
||
|
"""Function that will be registered as an inplace callback function.
|
||
|
It will be called when answering with a resolved query.
|
||
|
:param qinfo: query_info struct;
|
||
|
:param qstate: module qstate. It contains the available opt_lists; It
|
||
|
SHOULD NOT be altered;
|
||
|
:param rep: reply_info struct;
|
||
|
:param rcode: return code for the query;
|
||
|
:param edns: edns_data to be sent to the client side. It SHOULD NOT be
|
||
|
altered;
|
||
|
:param opt_list_out: the list with the EDNS options that will be sent as a
|
||
|
reply. It can be populated with EDNS options;
|
||
|
:param region: region to allocate temporary data. Needs to be used when we
|
||
|
want to append a new option to opt_list_out.
|
||
|
:return: True on success, False on failure.
|
||
|
"""
|
||
|
|
||
|
.. note:: The function's name is irrelevant.
|
||
|
|
||
|
We can register such function as:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
if not register_inplace_cb_reply(inplace_reply_callback, env, id):
|
||
|
log_info("python: Could not register inplace callback function.")
|
||
|
|
||
|
|
||
|
Inplace callback reply_cache functions
|
||
|
......................................
|
||
|
|
||
|
Called when answering *from cache*.
|
||
|
|
||
|
The callback function's prototype is the following:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
def inplace_cache_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
|
||
|
"""Function that will be registered as an inplace callback function.
|
||
|
It will be called when answering from the cache.
|
||
|
:param qinfo: query_info struct;
|
||
|
:param qstate: module qstate. None;
|
||
|
:param rep: reply_info struct;
|
||
|
:param rcode: return code for the query;
|
||
|
:param edns: edns_data sent from the client side. The list with the EDNS
|
||
|
options is accesible through edns.opt_list. It SHOULD NOT be
|
||
|
altered;
|
||
|
:param opt_list_out: the list with the EDNS options that will be sent as a
|
||
|
reply. It can be populated with EDNS options;
|
||
|
:param region: region to allocate temporary data. Needs to be used when we
|
||
|
want to append a new option to opt_list_out.
|
||
|
:return: True on success, False on failure.
|
||
|
"""
|
||
|
|
||
|
.. note:: The function's name is irrelevant.
|
||
|
|
||
|
We can register such function as:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
if not register_inplace_cb_reply_cache(inplace_cache_callback, env, id):
|
||
|
log_info("python: Could not register inplace callback function.")
|
||
|
|
||
|
|
||
|
Inplace callback reply_local functions
|
||
|
......................................
|
||
|
|
||
|
Called when answering with *local data* or a *Chaos(CH) reply*.
|
||
|
|
||
|
The callback function's prototype is the following:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
def inplace_local_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
|
||
|
"""Function that will be registered as an inplace callback function.
|
||
|
It will be called when answering from local data.
|
||
|
:param qinfo: query_info struct;
|
||
|
:param qstate: module qstate. None;
|
||
|
:param rep: reply_info struct;
|
||
|
:param rcode: return code for the query;
|
||
|
:param edns: edns_data sent from the client side. The list with the
|
||
|
EDNS options is accesible through edns.opt_list. It
|
||
|
SHOULD NOT be altered;
|
||
|
:param opt_list_out: the list with the EDNS options that will be sent as a
|
||
|
reply. It can be populated with EDNS options;
|
||
|
:param region: region to allocate temporary data. Needs to be used when we
|
||
|
want to append a new option to opt_list_out.
|
||
|
:return: True on success, False on failure.
|
||
|
"""
|
||
|
|
||
|
.. note:: The function's name is irrelevant.
|
||
|
|
||
|
We can register such function as:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
if not register_inplace_cb_reply_local(inplace_local_callback, env, id):
|
||
|
log_info("python: Could not register inplace callback function.")
|
||
|
|
||
|
|
||
|
Inplace callback reply_servfail functions
|
||
|
.........................................
|
||
|
|
||
|
Called when answering with *SERVFAIL*.
|
||
|
|
||
|
The callback function's prototype is the following:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
def inplace_servfail_callback(qinfo, qstate, rep, rcode, edns, opt_list_out, region):
|
||
|
"""Function that will be registered as an inplace callback function.
|
||
|
It will be called when answering with SERVFAIL.
|
||
|
:param qinfo: query_info struct;
|
||
|
:param qstate: module qstate. If not None the relevant opt_lists are
|
||
|
available here;
|
||
|
:param rep: reply_info struct. None;
|
||
|
:param rcode: return code for the query. LDNS_RCODE_SERVFAIL;
|
||
|
:param edns: edns_data to be sent to the client side. If qstate is None
|
||
|
edns.opt_list contains the EDNS options sent from the client
|
||
|
side. It SHOULD NOT be altered;
|
||
|
:param opt_list_out: the list with the EDNS options that will be sent as a
|
||
|
reply. It can be populated with EDNS options;
|
||
|
:param region: region to allocate temporary data. Needs to be used when we
|
||
|
want to append a new option to opt_list_out.
|
||
|
:return: True on success, False on failure.
|
||
|
"""
|
||
|
|
||
|
.. note:: The function's name is irrelevant.
|
||
|
|
||
|
We can register such function as:
|
||
|
|
||
|
.. code-block:: python
|
||
|
|
||
|
if not register_inplace_cb_reply_servfail(inplace_servfail_callback, env, id):
|
||
|
log_info("python: Could not register inplace callback function.")
|
||
|
|
||
|
|
||
|
Testing
|
||
|
~~~~~~~
|
||
|
|
||
|
Run the Unbound server: ::
|
||
|
|
||
|
root@localhost$ unbound -dv -c ./test-inplace_callbacks.conf
|
||
|
|
||
|
In case you use your own configuration file, don't forget to enable the Python
|
||
|
module::
|
||
|
|
||
|
module-config: "validator python iterator"
|
||
|
|
||
|
and use a valid script path ::
|
||
|
|
||
|
python-script: "./examples/inplace_callbacks.py"
|
||
|
|
||
|
On the first query for the nlnetlabs.nl A record we get no EDNS option back:
|
||
|
|
||
|
::
|
||
|
|
||
|
root@localhost$ dig @localhost nlnetlabs.nl +ednsopt=65002
|
||
|
|
||
|
; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost nlnetlabs.nl +ednsopt=65002
|
||
|
; (1 server found)
|
||
|
;; global options: +cmd
|
||
|
;; Got answer:
|
||
|
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48057
|
||
|
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 3
|
||
|
|
||
|
;; OPT PSEUDOSECTION:
|
||
|
; EDNS: version: 0, flags:; udp: 4096
|
||
|
;; QUESTION SECTION:
|
||
|
;nlnetlabs.nl. IN A
|
||
|
|
||
|
;; ANSWER SECTION:
|
||
|
nlnetlabs.nl. 10200 IN A 185.49.140.10
|
||
|
|
||
|
;; AUTHORITY SECTION:
|
||
|
nlnetlabs.nl. 10200 IN NS ns.nlnetlabs.nl.
|
||
|
nlnetlabs.nl. 10200 IN NS sec2.authdns.ripe.net.
|
||
|
nlnetlabs.nl. 10200 IN NS anyns.pch.net.
|
||
|
nlnetlabs.nl. 10200 IN NS ns-ext1.sidn.nl.
|
||
|
|
||
|
;; ADDITIONAL SECTION:
|
||
|
ns.nlnetlabs.nl. 10200 IN A 185.49.140.60
|
||
|
ns.nlnetlabs.nl. 10200 IN AAAA 2a04:b900::8:0:0:60
|
||
|
|
||
|
;; Query time: 813 msec
|
||
|
;; SERVER: 127.0.0.1#53(127.0.0.1)
|
||
|
;; WHEN: Mon Dec 05 16:15:32 CET 2016
|
||
|
;; MSG SIZE rcvd: 204
|
||
|
|
||
|
When we issue the same query again we get a cached response and the expected
|
||
|
``65002: 0xdeadbeef`` EDNS option:
|
||
|
|
||
|
::
|
||
|
|
||
|
root@localhost$ dig @localhost nlnetlabs.nl +ednsopt=65002
|
||
|
|
||
|
; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost nlnetlabs.nl +ednsopt=65002
|
||
|
; (1 server found)
|
||
|
;; global options: +cmd
|
||
|
;; Got answer:
|
||
|
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26489
|
||
|
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 3
|
||
|
|
||
|
;; OPT PSEUDOSECTION:
|
||
|
; EDNS: version: 0, flags:; udp: 4096
|
||
|
; OPT=65002: de ad be ef ("....")
|
||
|
;; QUESTION SECTION:
|
||
|
;nlnetlabs.nl. IN A
|
||
|
|
||
|
;; ANSWER SECTION:
|
||
|
nlnetlabs.nl. 10197 IN A 185.49.140.10
|
||
|
|
||
|
;; AUTHORITY SECTION:
|
||
|
nlnetlabs.nl. 10197 IN NS ns.nlnetlabs.nl.
|
||
|
nlnetlabs.nl. 10197 IN NS sec2.authdns.ripe.net.
|
||
|
nlnetlabs.nl. 10197 IN NS anyns.pch.net.
|
||
|
nlnetlabs.nl. 10197 IN NS ns-ext1.sidn.nl.
|
||
|
|
||
|
;; ADDITIONAL SECTION:
|
||
|
ns.nlnetlabs.nl. 10197 IN AAAA 2a04:b900::8:0:0:60
|
||
|
ns.nlnetlabs.nl. 10197 IN A 185.49.140.60
|
||
|
|
||
|
;; Query time: 0 msec
|
||
|
;; SERVER: 127.0.0.1#53(127.0.0.1)
|
||
|
;; WHEN: Mon Dec 05 16:50:04 CET 2016
|
||
|
;; MSG SIZE rcvd: 212
|
||
|
|
||
|
By issuing a query for a bogus domain unbound replies with SERVFAIL and an
|
||
|
empty EDNS option code ``65003``. *For this example to work unbound needs to be
|
||
|
validating*:
|
||
|
|
||
|
::
|
||
|
|
||
|
root@localhost$ dig @localhost bogus.nlnetlabs.nl txt
|
||
|
|
||
|
; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost bogus.nlnetlabs.nl txt
|
||
|
; (1 server found)
|
||
|
;; global options: +cmd
|
||
|
;; Got answer:
|
||
|
;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 19865
|
||
|
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 1
|
||
|
|
||
|
;; OPT PSEUDOSECTION:
|
||
|
; EDNS: version: 0, flags:; udp: 4096
|
||
|
; OPT=65003
|
||
|
;; QUESTION SECTION:
|
||
|
;bogus.nlnetlabs.nl. IN TXT
|
||
|
|
||
|
;; Query time: 11 msec
|
||
|
;; SERVER: 127.0.0.1#53(127.0.0.1)
|
||
|
;; WHEN: Mon Dec 05 17:06:01 CET 2016
|
||
|
;; MSG SIZE rcvd: 51
|
||
|
|
||
|
|
||
|
Complete source code
|
||
|
~~~~~~~~~~~~~~~~~~~~
|
||
|
.. literalinclude:: ../../examples/inplace_callbacks.py
|
||
|
:language: python
|