Merge pull request #161682 from NixOS/backport-161426-to-release-21.11

[Backport release-21.11] nixos/doc: improve release notes for iptables-nft and systemd with nftables backend

nixos/doc/manual/from_md/release-notes/rl-2111.section.xml

@@ -34,8 +34,26 @@
       </listitem>
       <listitem>
         <para>
-          <literal>iptables</literal> now uses
-          <literal>nf_tables</literal> backend.
+          <literal>iptables</literal> is now using
+          <literal>nf_tables</literal> under the hood, by using
+          <literal>iptables-nft</literal>, similar to
+          <link xlink:href="https://wiki.debian.org/nftables#Current_status">Debian</link>
+          and
+          <link xlink:href="https://fedoraproject.org/wiki/Changes/iptables-nft-default">Fedora</link>.
+          This means, <literal>ip[6]tables</literal>,
+          <literal>arptables</literal> and <literal>ebtables</literal>
+          commands will actually show rules from some specific tables in
+          the <literal>nf_tables</literal> kernel subsystem.
+        </para>
+      </listitem>
+      <listitem>
+        <para>
+          systemd got an <literal>nftables</literal> backend, and
+          configures (networkd) rules in their own
+          <literal>io.systemd.*</literal> tables. Check
+          <literal>nft list ruleset</literal> to see these rules, not
+          <literal>iptables-save</literal> (which only shows
+          <literal>iptables</literal>-created rules.
         </para>
       </listitem>
       <listitem>

nixos/doc/manual/release-notes/rl-2111.section.md

@@ -8,7 +8,15 @@ In addition to numerous new and upgraded packages, this release has the followin
 
 - The default Nix version remains at 2.3.16. Nix has not been updated to version 2.4 due to regressions in non-experimental behavior. To upgrade to 2.4, use the `nixos-unstable` branch or set the `nix.package` option to either of `nixFlakes` or `nix_2_4` packages. The `nixUnstable` attribute is a pre-release of Nix 2.5. Read the [release notes](https://discourse.nixos.org/t/nix-2-4-released/15822) for more information on upcoming changes. Please help us improve Nix by providing any [breakage reports](https://github.com/NixOS/nix/issues).
 
-- `iptables` now uses `nf_tables` backend.
+- `iptables` is now using `nf_tables` under the hood, by using `iptables-nft`,
+  similar to [Debian](https://wiki.debian.org/nftables#Current_status) and
+  [Fedora](https://fedoraproject.org/wiki/Changes/iptables-nft-default).
+  This means, `ip[6]tables`, `arptables` and `ebtables` commands  will actually
+  show rules from some specific tables in the `nf_tables` kernel subsystem.
+
+- systemd got an `nftables` backend, and configures (networkd) rules in their
+  own `io.systemd.*` tables. Check `nft list ruleset` to see these rules, not
+  `iptables-save` (which only shows `iptables`-created rules.
 
 - PHP now defaults to PHP 8.0, updated from 7.4.