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58bd26b6cf
This commit converts the license handling to adhere to the REUSE specification. It specifically: 1. Adds used licnses to LICENSES/ directory 2. Add "isc" template for adding the copyright boilerplate 3. Changes all source files to include copyright and SPDX license header, this includes all the C sources, documentation, zone files, configuration files. There are notes in the doc/dev/copyrights file on how to add correct headers to the new files. 4. Handle the rest that can't be modified via .reuse/dep5 file. The binary (or otherwise unmodifiable) files could have license places next to them in <foo>.license file, but this would lead to cluttered repository and most of the files handled in the .reuse/dep5 file are system test files.
83 lines
2.9 KiB
ReStructuredText
83 lines
2.9 KiB
ReStructuredText
.. Copyright (C) Internet Systems Consortium, Inc. ("ISC")
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..
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.. SPDX-License-Identifier: MPL-2.0
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..
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.. This Source Code Form is subject to the terms of the Mozilla Public
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.. License, v. 2.0. If a copy of the MPL was not distributed with this
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.. file, you can obtain one at https://mozilla.org/MPL/2.0/.
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..
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.. See the COPYRIGHT file distributed with this work for additional
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.. information regarding copyright ownership.
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.. _module-info:
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Plugins
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-------
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Plugins are a mechanism to extend the functionality of ``named`` using
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dynamically loadable libraries. By using plugins, core server
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functionality can be kept simple for the majority of users; more complex
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code implementing optional features need only be installed by users that
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need those features.
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The plugin interface is a work in progress, and is expected to evolve as
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more plugins are added. Currently, only "query plugins" are supported;
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these modify the name server query logic. Other plugin types may be
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added in the future.
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The only plugin currently included in BIND is ``filter-aaaa.so``, which
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replaces the ``filter-aaaa`` feature that previously existed natively as
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part of ``named``. The code for this feature has been removed from
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``named`` and can no longer be configured using standard ``named.conf``
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syntax, but linking in the ``filter-aaaa.so`` plugin provides identical
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functionality.
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Configuring Plugins
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~~~~~~~~~~~~~~~~~~~
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A plugin is configured with the ``plugin`` statement in ``named.conf``:
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::
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plugin query "library.so" {
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parameters
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};
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In this example, file ``library.so`` is the plugin library. ``query``
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indicates that this is a query plugin.
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Multiple ``plugin`` statements can be specified, to load different
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plugins or multiple instances of the same plugin.
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``parameters`` are passed as an opaque string to the plugin's initialization
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routine. Configuration syntax differs depending on the module.
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Developing Plugins
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~~~~~~~~~~~~~~~~~~
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Each plugin implements four functions:
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- ``plugin_register``
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to allocate memory, configure a plugin instance, and attach to hook
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points within
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``named``
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,
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- ``plugin_destroy``
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to tear down the plugin instance and free memory,
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- ``plugin_version``
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to check that the plugin is compatible with the current version of
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the plugin API,
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- ``plugin_check``
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to test syntactic correctness of the plugin parameters.
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At various locations within the ``named`` source code, there are "hook
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points" at which a plugin may register itself. When a hook point is
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reached while ``named`` is running, it is checked to see whether any
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plugins have registered themselves there; if so, the associated "hook
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action" - a function within the plugin library - is called. Hook
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actions may examine the runtime state and make changes: for example,
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modifying the answers to be sent back to a client or forcing a query to
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be aborted. More details can be found in the file
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``lib/ns/include/ns/hooks.h``.
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