nixos/networkd: rename the networkd dhcpConfig option to dhcpV4Config

This follows upstreams change in documentation. While the `[DHCP]`
section might still work it is undocumented and we should probably not
be using it anymore. Users can just upgrade to the new option without
much hassle.

I had to create a bit of custom module deprecation code since the usual
approach doesn't support wildcards in the path.

nixos/doc/manual/release-notes/rl-2009.xml

@@ -300,6 +300,17 @@ environment.systemPackages = [
       <manvolnum>5</manvolnum></citerefentry> for details.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     The <literal>systemd-networkd</literal> option
+     <literal>systemd.network.networks._name_.dhcpConfig</literal>
+     has been renamed to
+     <xref linkend="opt-systemd.network.networks._name_.dhcpV4Config"/>
+     following upstream systemd's documentation change.
+     See <citerefentry><refentrytitle>systemd.network</refentrytitle>
+     <manvolnum>5</manvolnum></citerefentry> for details.
+    </para>
+   </listitem>
   </itemizedlist>
  </section>
 

nixos/modules/system/boot/networkd.nix

@@ -275,13 +275,13 @@ let
     ])
   ];
 
-  checkDhcp = checkUnitConfig "DHCP" [
+  checkDhcpV4 = checkUnitConfig "DHCPv4" [
     (assertOnlyFields [
       "UseDNS" "RoutesToDNS" "UseNTP" "UseMTU" "Anonymize" "SendHostname" "UseHostname"
       "Hostname" "UseDomains" "UseRoutes" "UseTimezone"
       "ClientIdentifier" "VendorClassIdentifier" "UserClass" "MaxAttempts"
       "DUIDType" "DUIDRawData" "IAID" "RequestBroadcast" "RouteMetric" "RouteTable"
-      "ListenPort" "SendRelease" "RapidCommit"
+      "ListenPort" "SendRelease"
     ])
     (assertValueOneOf "UseDNS" boolValues)
     (assertValueOneOf "RoutesToDNS" boolValues)
@@ -298,7 +298,6 @@ let
     (assertInt "RouteTable")
     (assertMinimum "RouteTable" 0)
     (assertValueOneOf "SendRelease" boolValues)
-    (assertValueOneOf "RapidCommit" boolValues)
   ];
 
   checkDhcpV6 = checkUnitConfig "DHCPv6" [
@@ -649,13 +648,20 @@ let
       '';
     };
 
+    # systemd.network.networks.*.dhcpConfig has been deprecated in favor of ….dhcpV4Config
+    # Produce a nice warning message so users know it is gone.
     dhcpConfig = mkOption {
+      visible = false;
+      apply = _: throw "The option `systemd.network.networks.*.dhcpConfig` can no longer be used since it's been removed. Please use `systemd.network.networks.*.dhcpV4Config` instead.";
+    };
+
+    dhcpV4Config = mkOption {
       default = {};
       example = { UseDNS = true; UseRoutes = true; };
-      type = types.addCheck (types.attrsOf unitOption) checkDhcp;
+      type = types.addCheck (types.attrsOf unitOption) checkDhcpV4;
       description = ''
         Each attribute in this set specifies an option in the
-        <literal>[DHCP]</literal> section of the unit.  See
+        <literal>[DHCPv4]</literal> section of the unit.  See
         <citerefentry><refentrytitle>systemd.network</refentrytitle>
         <manvolnum>5</manvolnum></citerefentry> for details.
       '';
@@ -998,9 +1004,9 @@ let
           ${concatStringsSep "\n" (map (s: "Tunnel=${s}") def.tunnel)}
           ${concatStringsSep "\n" (map (s: "Xfrm=${s}") def.xfrm)}
 
-          ${optionalString (def.dhcpConfig != { }) ''
-            [DHCP]
-            ${attrsToSection def.dhcpConfig}
+          ${optionalString (def.dhcpV4Config != { }) ''
+            [DHCPv4]
+            ${attrsToSection def.dhcpV4Config}
 
           ''}
           ${optionalString (def.dhcpV6Config != {}) ''
@@ -1084,6 +1090,7 @@ in
   };
 
   config = mkMerge [
+
     # .link units are honored by udev, no matter if systemd-networkd is enabled or not.
     {
       systemd.network.units = mapAttrs' (n: v: nameValuePair "${n}.link" (linkToUnit n v)) cfg.links;

nixos/modules/virtualisation/nixos-containers.nix

@@ -546,7 +546,7 @@ in
 
                 Note that this option might require to do some adjustments to the container configuration,
                 e.g. you might want to set
-                <varname>systemd.network.networks.$interface.dhcpConfig.ClientIdentifier</varname> to "mac"
+                <varname>systemd.network.networks.$interface.dhcpV4Config.ClientIdentifier</varname> to "mac"
                 if you use <varname>macvlans</varname> option.
                 This way dhcp client identifier will be stable between the container restarts.