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b42681c4e9
Replace the hard-coded paths for various BIND 9 files (configuration, pid, etc.) in the man pages and ARM with compile-time values using the sphinx-build replace system. This is more complicated, because the restructured text specification doesn't allow |substitions| inside ``code-blocks``, so for each specific file we had to create own substition which is sub-optimal, but it is only way how to do this without adding Sphinx extension.
85 lines
2.8 KiB
ReStructuredText
85 lines
2.8 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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.. highlight: console
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.. _man_filter-a:
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filter-a.so - filter A in DNS responses when AAAA is present
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---------------------------------------------------------------
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Synopsis
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~~~~~~~~
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:program:`plugin query` "filter-a.so" [{ parameters }];
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Description
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~~~~~~~~~~~
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``filter-a.so`` is a query plugin module for ``named``, enabling
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``named`` to omit some IPv4 addresses when responding to clients.
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For example:
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::
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plugin query "filter-a.so" {
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filter-a-on-v6 yes;
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filter-a-on-v4 yes;
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filter-a { 192.0.2.1; 2001:db8:2::1; };
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};
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This module is intended to aid transition from IPv4 to IPv6 by
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withholding IPv4 addresses from DNS clients which are not connected to
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the IPv4 Internet, when the name being looked up has an IPv6 address
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available. Use of this module is not recommended unless absolutely
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necessary.
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Note: This mechanism can erroneously cause other servers not to give
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A records to their clients. If a recursing server with both IPv6 and
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IPv4 network connections queries an authoritative server using this
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mechanism via IPv6, it is denied A records even if its client is
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using IPv4.
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Options
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~~~~~~~
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``filter-a``
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This option specifies a list of client addresses for which A filtering is to
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be applied. The default is ``any``.
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``filter-a-on-v6``
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If set to ``yes``, this option indicates that the DNS client is at an IPv6 address, in
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``filter-a``. If the response does not include DNSSEC
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signatures, then all A records are deleted from the response. This
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filtering applies to all responses, not only authoritative
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ones.
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If set to ``break-dnssec``, then A records are deleted even when
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DNSSEC is enabled. As suggested by the name, this causes the response
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to fail to verify, because the DNSSEC protocol is designed to detect
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deletions.
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This mechanism can erroneously cause other servers not to give A
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records to their clients. If a recursing server with both IPv6 and IPv4
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network connections queries an authoritative server using this
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mechanism via IPv6, it is denied A records even if its client is
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using IPv4.
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``filter-a-on-v4``
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This option is identical to ``filter-a-on-v6``, except that it filters A responses
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to queries from IPv4 clients instead of IPv6 clients. To filter all
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responses, set both options to ``yes``.
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See Also
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~~~~~~~~
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BIND 9 Administrator Reference Manual.
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