| 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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| 4 | <!ENTITY % general-entities SYSTEM "../../general.ent">
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| 5 | %general-entities;
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| 6 |
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| 7 | <!ENTITY nftables-download-http "https://netfilter.org/projects/nftables/files/nftables-&nftables-version;.tar.bz2">
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| 8 | <!ENTITY nftables-download-ftp " ">
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| 9 | <!ENTITY nftables-md5sum "9913b2b46864394d41916b74638e0875">
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| 10 | <!ENTITY nftables-size "772 KB">
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| 11 | <!ENTITY nftables-buildsize "34 MB">
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| 12 | <!ENTITY nftables-time "0.2 SBU">
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| 13 | ]>
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| 14 |
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| 15 | <sect1 id="nftables" xreflabel="nftables-&nftables-version;">
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| 16 | <?dbhtml filename="nftables.html"?>
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| 17 |
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| 18 |
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| 19 | <title>nftables-&nftables-version;</title>
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| 20 |
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| 21 | <indexterm zone="nftables">
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| 22 | <primary sortas="a-nftables">nftables</primary>
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| 23 | </indexterm>
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| 24 |
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| 25 | <sect2 role="package">
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| 26 | <title>Introduction to nftables</title>
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| 27 |
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| 28 | <para>
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| 29 | The <application>nftables</application> package, intended to be the
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| 30 | successor to <xref linkend="iptables"/>, provides a low-level netlink
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| 31 | programming interface (API), and userspace uitlities for the in-kernel
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| 32 | nf_tables subsystem.
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| 33 | </para>
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| 34 |
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| 35 | &lfs90_checked;
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| 36 |
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| 37 | <bridgehead renderas="sect3">Package Information</bridgehead>
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| 38 | <itemizedlist spacing='compact'>
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| 39 | <listitem>
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| 40 | <para>
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| 41 | Download (HTTP): <ulink url="&nftables-download-http;"/>
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| 42 | </para>
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| 43 | </listitem>
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| 44 | <listitem>
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| 45 | <para>
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| 46 | Download (FTP): <ulink url="&nftables-download-ftp;"/>
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| 47 | </para>
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| 48 | </listitem>
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| 49 | <listitem>
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| 50 | <para>
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| 51 | Download MD5 sum: &nftables-md5sum;
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| 52 | </para>
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| 53 | </listitem>
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| 54 | <listitem>
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| 55 | <para>
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| 56 | Download size: &nftables-size;
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| 57 | </para>
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| 58 | </listitem>
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| 59 | <listitem>
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| 60 | <para>
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| 61 | Estimated disk space required: &nftables-buildsize;
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| 62 | </para>
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| 63 | </listitem>
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| 64 | <listitem>
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| 65 | <para>
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| 66 | Estimated build time: &nftables-time;
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| 67 | </para>
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| 68 | </listitem>
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| 69 | </itemizedlist>
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| 70 |
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| 71 | <bridgehead renderas="sect3">nftables Dependencies</bridgehead>
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| 72 |
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| 73 | <bridgehead renderas="sect4">Required</bridgehead>
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| 74 | <para role="required">
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| 75 | <xref linkend="libnftnl"/>
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| 76 | </para>
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| 77 |
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| 78 | <bridgehead renderas="sect4">Recommended</bridgehead>
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| 79 | <para role="recommended">
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| 80 | <xref linkend="jansson"/> (for JSON rules table support)
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| 81 | </para>
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| 82 |
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| 83 | <bridgehead renderas="sect4">Optional</bridgehead>
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| 84 | <para role="optional">
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| 85 | <xref linkend="iptables"/> and
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| 86 | <xref linkend="docbook-utils"/>
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| 87 | </para>
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| 88 |
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| 89 | <bridgehead renderas="sect4">Optional (runtime)</bridgehead>
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| 90 |
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| 91 | <para role="optional">
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| 92 | <ulink url="https://netfilter.org/projects/conntrack-tools/index.html">
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| 93 | contrack-tools</ulink>
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| 94 | <ulink url="https://netfilter.org/projects/nfacct/index.html">
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| 95 | nfacct</ulink>
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| 96 | <ulink url="https://netfilter.org/projects/ulogd/index.html">
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| 97 | ulogd</ulink>
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| 98 | </para>
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| 99 |
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| 100 | <para condition="html" role="usernotes">User Notes:
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| 101 | <ulink url="&blfs-wiki;/nftables"/>
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| 102 | </para>
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| 103 | </sect2>
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| 104 |
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| 105 | <sect2 role="kernel">
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| 106 | <title>Kernel Configuration</title>
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| 107 |
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| 108 | <para>
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| 109 | Enable the following options in the kernel configuration and recompile the
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| 110 | kernel if necessary (add any additional nf_tables features as needed):
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| 111 | </para>
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| 112 |
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| 113 | <screen><literal>[*] Networking support [CONFIG_NET] --->
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| 114 | Networking options --->
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| 115 | [*] Network packet filtering framework (Netfilter) [CONFIG_NETFILTER] --->
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| 116 | Core Netfilter Configuration --->
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| 117 | <*> * protocol support [CONFIG_NF_CONNTRACK_*]
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| 118 | <*> Netfilter nf_tables support [CONFIG_NF_TABLES]
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| 119 | [*] Netfilter nf_tables * support [CONFIG_NF_TABLES_*]</literal></screen>
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| 120 |
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| 121 | <para>
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| 122 | Include any connection tracking protocols that will be used, and
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| 123 | any protocols that you wish to use for match suppport under the
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| 124 | "Core Netfilter Configuration" section. Additionally, include any
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| 125 | "Netfilter nf_tables * module" that will be used under the
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| 126 | "Netfilter nf_tables support" section.
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| 127 | </para>
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| 128 |
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| 129 |
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| 130 | </sect2>
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| 131 |
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| 132 | <sect2 role="installation">
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| 133 | <title>Installation of nftables</title>
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| 134 |
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| 135 | <para>
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| 136 | Install <application>nftables</application> by running the following
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| 137 | commands:
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| 138 | </para>
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| 139 |
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| 140 | <screen><userinput>./configure --prefix=/usr \
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| 141 | --sbindir=/sbin \
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| 142 | --sysconfdir=/etc \
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| 143 | --with-json \
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| 144 | --with-python-bin=/usr/bin/python3 &&
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| 145 | make</userinput></screen>
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| 146 |
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| 147 | <para>
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| 148 | This package does not come with a test suite.
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| 149 | </para>
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| 150 |
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| 151 | <para>
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| 152 | Now, as the <systemitem class="username">root</systemitem> user:
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| 153 | </para>
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| 154 |
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| 155 | <screen role="root"><userinput>make install &&
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| 156 | mv /usr/lib/libnftables.so.* /lib &&
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| 157 | ln -sfv ../../lib/$(readlink /usr/lib/libnftables.so) /usr/lib/libnftables.so</userinput></screen>
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| 158 |
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| 159 | </sect2>
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| 160 |
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| 161 | <sect2 role="commands">
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| 162 | <title>Command Explanations</title>
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| 163 |
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| 164 | <!-- there is no disable-static option in the configure string
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| 165 | <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
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| 166 | href="../../xincludes/static-libraries.xml"/>
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| 167 | -->
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| 168 | <para>
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| 169 | <parameter>--with-json</parameter>: build with support for JSON rules.
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| 170 | Omit if <xref linkend="jansson"/> is not available.
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| 171 | </para>
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| 172 |
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| 173 | <para>
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| 174 | <parameter>--with-python-bin=/usr/bin/python3</parameter>: force use of
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| 175 | <application>Python3</application>.
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| 176 | </para>
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| 177 |
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| 178 | <para>
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| 179 | <option>--enable-man-doc</option>: build man pages if
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| 180 | <xref linkend="asciidoc"/> is installed (required if adding
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| 181 | json support).
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| 182 | </para>
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| 183 |
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| 184 | <para>
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| 185 | <option>--with-xtables</option>: build with
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| 186 | <xref linkend="iptables"/> libxtables support.
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| 187 | </para>
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| 188 |
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| 189 | <para>
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| 190 | <command>mv -v /usr/lib/nftables.so.* ...</command>: Move shared
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| 191 | libraries into /lib so they are available before /usr is mounted.
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| 192 | </para>
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| 193 |
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| 194 | </sect2>
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| 195 |
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| 196 | <sect2 role="configuration">
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| 197 | <title>Configuring nftables</title>
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| 198 |
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| 199 | <note>
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| 200 | <para>
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| 201 | If you intend to use <xref linkend="firewalld"/> to configure your
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| 202 | firewall rules, you should not use the example configuration provided
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| 203 | here, nor should you enable the
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| 204 | <phrase revision="sysv">bootscript.</phrase>
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| 205 | <phrase revision="systemd">systemd unit.</phrase>
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| 206 | </para>
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| 207 | </note>
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| 208 |
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| 209 | <sect3 id="fw-masqRouter-nft"
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| 210 | xreflabel="Creating a Masquerading Router With nftables">
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| 211 | <title>Masquerading Router</title>
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| 212 |
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| 213 | <para>
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| 214 | A network Firewall has two interfaces, one connected to an
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| 215 | intranet, in this example <emphasis role="strong">LAN1</emphasis>,
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| 216 | and one connected to the Internet, here <emphasis
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| 217 | role="strong">WAN1</emphasis>. You will need to adjust these value to
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| 218 | match your particular system. To provide the maximum security
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| 219 | for the firewall itself, make sure that there are no unnecessary
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| 220 | servers running on it such as <application>X11</application> et al.
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| 221 | As a general principle, the firewall itself should not access
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| 222 | any untrusted service (think of a remote server giving answers that
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| 223 | makes a daemon on your system crash, or even worse, that implements
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| 224 | a worm via a buffer-overflow).
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| 225 | </para>
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| 226 |
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| 227 | <note>
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| 228 | <para>
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| 229 | In the following example configuration, <emphasis
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| 230 | role="strong">LAN1</emphasis> is used for the internal LAN interface,
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| 231 | and <emphasis role="strong">WAN1</emphasis> is used for the external
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| 232 | interface connected to the Internet. You will need to replace these
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| 233 | values with appropriate interface names for your system.
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| 234 | </para>
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| 235 | </note>
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| 236 |
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| 237 |
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| 238 | <screen role="root"><?dbfo keep-together="auto"?><userinput>cat > /etc/nftables/nftables.conf << "EOF"
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| 239 | <literal>#!/sbin/nft -f
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| 240 |
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| 241 | # You're using the example configuration for a setup of a firewall
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| 242 | # from Beyond Linux From Scratch.
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| 243 | #
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| 244 | # This example is far from being complete, it is only meant
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| 245 | # to be a reference.
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| 246 | #
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| 247 | # Firewall security is a complex issue, that exceeds the scope
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| 248 | # of the configuration rules below.
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| 249 | #
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| 250 | # You can find additional information
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| 251 | # about firewalls in Chapter 4 of the BLFS book.
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| 252 | # https://www.&lfs-domainname;/blfs
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| 253 |
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| 254 | # Drop all existing rules
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| 255 | flush ruleset
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| 256 |
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| 257 | # Filter for both ip4 and ip6 (inet)
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| 258 | table inet filter {
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| 259 |
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| 260 | # filter incomming packets
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| 261 | chain input {
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| 262 |
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| 263 | # Drop everything that doesn't match policy
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| 264 | type filter hook input priority 0; policy drop;
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| 265 |
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| 266 | # accept packets for established connections
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| 267 | ct state { established, related } accept
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| 268 |
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| 269 | # Drop packets that have a connection state of invalid
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| 270 | ct state invalid drop
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| 271 |
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| 272 | # Allow connections to the loopback adapter
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| 273 | iifname "lo" accept
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| 274 |
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| 275 | # Allow connections to the LAN1 interface
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| 276 | iifname "LAN1" accept
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| 277 |
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| 278 | # Accept icmp requests
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| 279 | ip protocol icmp accept
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| 280 |
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| 281 | # Allow ssh connections on LAN1
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| 282 | iifname "LAN1" tcp dport ssh accept
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| 283 |
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| 284 | # Drop everything else
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| 285 | drop
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| 286 | }
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| 287 |
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| 288 | # Allow forwarding for external connections to WAN1
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| 289 | chain forward {
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| 290 |
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| 291 | # Drop if it doesn't match policy
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| 292 | type filter hook forward priority 0; policy drop;
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| 293 |
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| 294 | # Accept connections on WAN1
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| 295 | oifname "WAN1" accept
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| 296 |
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| 297 | # Allow forwarding to another host via this interface
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| 298 | # Uncomment the following line to allow connections
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| 299 | # ip daddr 192.168.0.2 ct status dnat accept
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| 300 |
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| 301 | # Allow established and related connections
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| 302 | iifname "WAN1" ct state { established, related } accept
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| 303 | }
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| 304 |
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| 305 | # Filter output traffic
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| 306 | chain output {
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| 307 |
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| 308 | # Allow everything outbound
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| 309 | type filter hook output priority 0; policy accept;
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| 310 | }
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| 311 | }
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| 312 |
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| 313 | # Allow NAT for ip protocol (both ip4 and ip6)
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| 314 | table ip nat {
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| 315 |
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| 316 | chain prerouting {
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| 317 |
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| 318 | # Accept on inbound interface for policy match
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| 319 | type nat hook prerouting priority 0; policy accept;
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| 320 |
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| 321 | # Accept http and https on 192.168.0.2
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| 322 | # Uncomment the following line to allow http and https
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| 323 | #iifname "WAN1" tcp dport { http, https } dnat to 192.168.0.2
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| 324 | }
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| 325 |
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| 326 | chain postrouting {
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| 327 |
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| 328 | # accept outbound
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| 329 | type nat hook postrouting priority 0; policy accept;
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| 330 |
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| 331 | # Masquerade on WAN1 outbound
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| 332 | oifname "WAN1" masquerade
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| 333 | }
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| 334 | }</literal>
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| 335 | EOF</userinput></screen>
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| 336 |
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| 337 | <para>
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| 338 | With this configuration your intranet should be reasonably secure
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| 339 | against external attacks. No one should be able to setup a new
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| 340 | connection to any internal service not configured above.
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| 341 | </para>
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| 342 |
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| 343 | <para>
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| 344 | There are several other examples in the
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| 345 | <filename class="directory">/etc/nftables</filename> directory.
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| 346 | </para>
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| 347 |
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| 348 | </sect3>
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| 349 |
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| 350 | <sect3 id="nftables-init">
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| 351 | <title><phrase revision="sysv">Boot Script</phrase>
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| 352 | <phrase revision="systemd">Systemd Unit</phrase></title>
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| 353 |
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| 354 | <para revision="sysv">
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| 355 | To set up the nftables firewall at boot, install the
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| 356 | <filename>/etc/rc.d/init.d/nftables</filename> init script included
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| 357 | in the <xref linkend="bootscripts"/> package.
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| 358 | </para>
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| 359 |
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| 360 | <para revision="systemd">
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| 361 | To set up the nftables firewall at boot, install the
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| 362 | <filename>nftables.service</filename> unit included in the
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| 363 | <xref linkend="systemd-units"/> package.
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| 364 | </para>
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| 365 |
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| 366 | <indexterm zone="nftables nftables-init">
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| 367 | <primary sortas="f-nftables">nftables</primary>
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| 368 | </indexterm>
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| 369 |
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| 370 | <screen role="root"><userinput>make install-nftables</userinput></screen>
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| 371 |
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| 372 | </sect3>
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| 373 |
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| 374 | </sect2>
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| 375 |
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| 376 | <sect2 role="content">
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| 377 | <title>Contents</title>
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| 378 |
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| 379 | <segmentedlist>
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| 380 | <segtitle>Installed Programs</segtitle>
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| 381 | <segtitle>Installed Libraries</segtitle>
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| 382 | <segtitle>Installed Directories</segtitle>
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| 383 |
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| 384 | <seglistitem>
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| 385 | <seg>
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| 386 | nft
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| 387 | </seg>
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| 388 | <seg>
|
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| 389 | libnftables.{a,so}
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| 390 | </seg>
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| 391 | <seg>
|
|---|
| 392 | /etc/nftables
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| 393 | </seg>
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| 394 | </seglistitem>
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| 395 | </segmentedlist>
|
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| 396 |
|
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| 397 | <variablelist>
|
|---|
| 398 | <bridgehead renderas="sect3">Short Descriptions</bridgehead>
|
|---|
| 399 | <?dbfo list-presentation="list"?>
|
|---|
| 400 | <?dbhtml list-presentation="table"?>
|
|---|
| 401 |
|
|---|
| 402 | <varlistentry id="nft">
|
|---|
| 403 | <term><filename>nft</filename></term>
|
|---|
| 404 | <listitem>
|
|---|
| 405 | <para>
|
|---|
| 406 | command line interface for the nf_tables subsystem.
|
|---|
| 407 | </para>
|
|---|
| 408 | <indexterm zone="nftables nft">
|
|---|
| 409 | <primary sortas="a-nft">nft</primary>
|
|---|
| 410 | </indexterm>
|
|---|
| 411 | </listitem>
|
|---|
| 412 | </varlistentry>
|
|---|
| 413 |
|
|---|
| 414 | <varlistentry id="libnftables">
|
|---|
| 415 | <term><filename class="libraryfile">libnftables.{a,so}</filename></term>
|
|---|
| 416 | <listitem>
|
|---|
| 417 | <para>
|
|---|
| 418 | provides functions for manipulating the nf_tables subsystem.
|
|---|
| 419 | </para>
|
|---|
| 420 | <indexterm zone="nftables libnftables">
|
|---|
| 421 | <primary sortas="c-libnftables">libnftables.so</primary>
|
|---|
| 422 | </indexterm>
|
|---|
| 423 | </listitem>
|
|---|
| 424 | </varlistentry>
|
|---|
| 425 |
|
|---|
| 426 | </variablelist>
|
|---|
| 427 |
|
|---|
| 428 | </sect2>
|
|---|
| 429 |
|
|---|
| 430 | </sect1>
|
|---|
