NixOS · Sep 24, 2019 · Sep 24, 2019 · Sep 24, 2019 · Sep 25, 2019 · Oct 7, 2019
diff --git a/nixos/doc/manual/release-notes/rl-1909.xml b/nixos/doc/manual/release-notes/rl-1909.xml
@@ -512,6 +512,12 @@
        is set to <literal>/var/lib/gitlab/state</literal>, <literal>gitlab</literal> and all parent directories
        must be owned by either <literal>root</literal> or the user specified in <option>services.gitlab.user</option>.
      </para>
+     <para>
+      The <option>networking.useDHCP</option> option is unsupported in combination with
+      <option>networking.useNetworkd</option> in anticipation of defaulting to it by default.
+      It has to be set to <literal>false</literal> and enabled per
+      interface with <option>networking.interfaces.&lt;name&gt;.useDHCP = true;</option>
+    </para>
    </listitem>
    <listitem>
      <para>

diff --git a/nixos/modules/installer/tools/nixos-generate-config.pl b/nixos/modules/installer/tools/nixos-generate-config.pl
@@ -563,6 +563,24 @@ sub multiLineList {
 ${\join "", (map { "  $_\n" } (uniq @attrs))}}
 EOF
 
+sub generateNetworkingDhcpConfig {
+    my $config = <<EOF;
+  # The global useDHCP flag is deprecated, therefore explicitly set to false here.
+  # Per-interface useDHCP will be mandatory in the future, so this generated config
+  # replicates the default behaviour.
+  networking.useDHCP = false;
+EOF
+
+    foreach my $path (glob "/sys/class/net/*") {
+        my $dev = basename($path);
+        if ($dev ne "lo") {
+            $config .= "  networking.interfaces.$dev.useDHCP = true;\n";
+        }
+    }
+
+    return $config;
+}
+
 
 if ($showHardwareConfig) {
     print STDOUT $hwConfig;
@@ -606,6 +624,8 @@ sub multiLineList {
 EOF
         }
 
+        my $networkingDhcpConfig = generateNetworkingDhcpConfig();
+
         write_file($fn, <<EOF);
 @configuration@
 EOF

diff --git a/nixos/modules/installer/tools/tools.nix b/nixos/modules/installer/tools/tools.nix
@@ -96,6 +96,7 @@ in
         # networking.hostName = "nixos"; # Define your hostname.
         # networking.wireless.enable = true;  # Enables wireless support via wpa_supplicant.
 
+      $networkingDhcpConfig
         # Configure network proxy if necessary
         # networking.proxy.default = "http://user:password\@proxy:port/";
         # networking.proxy.noProxy = "127.0.0.1,localhost,internal.domain";

diff --git a/nixos/modules/tasks/network-interfaces-systemd.nix b/nixos/modules/tasks/network-interfaces-systemd.nix
@@ -38,6 +38,12 @@ in
     } {
       assertion = cfg.defaultGateway6 == null || cfg.defaultGateway6.interface == null;
       message = "networking.defaultGateway6.interface is not supported by networkd.";
+    } {
+      assertion = cfg.useDHCP == false;
+      message = ''
+        networking.useDHCP is not supported by networkd.
+        Please use per interface configuration and set the global option to false.
+      '';
     } ] ++ flip mapAttrsToList cfg.bridges (n: { rstp, ... }: {
       assertion = !rstp;
       message = "networking.bridges.${n}.rstp is not supported by networkd.";
@@ -56,9 +62,7 @@ in
         genericNetwork = override:
           let gateway = optional (cfg.defaultGateway != null) cfg.defaultGateway.address
             ++ optional (cfg.defaultGateway6 != null) cfg.defaultGateway6.address;
-          in {
-            DHCP = override (dhcpStr cfg.useDHCP);
-          } // optionalAttrs (gateway != [ ]) {
+          in optionalAttrs (gateway != [ ]) {
             routes = override [
               {
                 routeConfig = {
@@ -97,7 +101,7 @@ in
         networks."40-${i.name}" = mkMerge [ (genericNetwork mkDefault) {
           name = mkDefault i.name;
           DHCP = mkForce (dhcpStr
-            (if i.useDHCP != null then i.useDHCP else cfg.useDHCP && interfaceIps i == [ ]));
+            (if i.useDHCP != null then i.useDHCP else false));
           address = forEach (interfaceIps i)
             (ip: "${ip.address}/${toString ip.prefixLength}");
           networkConfig.IPv6PrivacyExtensions = "kernel";

diff --git a/nixos/modules/tasks/network-interfaces.nix b/nixos/modules/tasks/network-interfaces.nix
@@ -903,6 +903,11 @@ in
         Whether to use DHCP to obtain an IP address and other
         configuration for all network interfaces that are not manually
         configured.
+
+        Using this option is highly discouraged and also incompatible with
+        <option>networking.useNetworkd</option>. Please use
+        <option>networking.interfaces.&lt;name&gt;.useDHCP</option> instead
+        and set this to false.
       '';
     };
 

diff --git a/nixos/tests/networking.nix b/nixos/tests/networking.nix
@@ -72,6 +72,7 @@ let
   testCases = {
     loopback = {
       name = "Loopback";
+      machine.networking.useDHCP = false;
       machine.networking.useNetworkd = networkd;
       testScript = ''
         startAll;
@@ -139,14 +140,16 @@ let
         virtualisation.vlans = [ 1 2 ];
         networking = {
           useNetworkd = networkd;
-          useDHCP = true;
+          useDHCP = false;
           interfaces.eth1 = {
             ipv4.addresses = mkOverride 0 [ ];
             ipv6.addresses = mkOverride 0 [ ];
+            useDHCP = true;
           };
           interfaces.eth2 = {
             ipv4.addresses = mkOverride 0 [ ];
             ipv6.addresses = mkOverride 0 [ ];
+            useDHCP = true;
           };
         };
       };
@@ -320,13 +323,19 @@ let
         virtualisation.vlans = [ 1 ];
         networking = {
           useNetworkd = networkd;
+          useDHCP = false;
           firewall.logReversePathDrops = true; # to debug firewall rules
           # reverse path filtering rules for the macvlan interface seem
           # to be incorrect, causing the test to fail. Disable temporarily.
           firewall.checkReversePath = false;
-          useDHCP = true;
           macvlans.macvlan.interface = "eth1";
-          interfaces.eth1.ipv4.addresses = mkOverride 0 [ ];
+          interfaces.eth1 = {
+            ipv4.addresses = mkOverride 0 [ ];
+            useDHCP = true;
+          };
+          interfaces.macvlan = {
+            useDHCP = true;
+          };
         };
       };
       testScript = { ... }:
@@ -440,6 +449,7 @@ let
     virtual = {
       name = "Virtual";
       machine = {
+        networking.useNetworkd = networkd;
         networking.interfaces.tap0 = {
           ipv4.addresses = [ { address = "192.168.1.1"; prefixLength = 24; } ];
           ipv6.addresses = [ { address = "2001:1470:fffd:2096::"; prefixLength = 64; } ];
@@ -489,6 +499,7 @@ let
         boot.kernel.sysctl."net.ipv6.conf.all.forwarding" = true;
         networking = {
           useNetworkd = networkd;
+          useDHCP = false;
           interfaces.eth1.ipv6.addresses = singleton {
             address = "fd00:1234:5678:1::1";
             prefixLength = 64;
@@ -514,23 +525,25 @@ let
         virtualisation.vlans = [ 1 ];
         networking = {
           useNetworkd = networkd;
-          useDHCP = true;
+          useDHCP = false;
           interfaces.eth1 = {
             preferTempAddress = true;
             ipv4.addresses = mkOverride 0 [ ];
             ipv6.addresses = mkOverride 0 [ ];
+            useDHCP = true;
           };
         };
       };
       nodes.client = { pkgs, ... }: with pkgs.lib; {
         virtualisation.vlans = [ 1 ];
         networking = {
           useNetworkd = networkd;
-          useDHCP = true;
+          useDHCP = false;
           interfaces.eth1 = {
             preferTempAddress = false;
             ipv4.addresses = mkOverride 0 [ ];
             ipv6.addresses = mkOverride 0 [ ];
+            useDHCP = true;
           };
         };
       };

diff --git a/nixos/tests/predictable-interface-names.nix b/nixos/tests/predictable-interface-names.nix
@@ -16,6 +16,7 @@ in pkgs.lib.listToAttrs (pkgs.lib.crossLists (predictable: withNetworkd: {
       networking.usePredictableInterfaceNames = lib.mkForce predictable;
       networking.useNetworkd = withNetworkd;
       networking.dhcpcd.enable = !withNetworkd;
+      networking.useDHCP = !withNetworkd;
     };
 
     testScript = ''

diff --git a/nixos/tests/systemd-networkd-wireguard.nix b/nixos/tests/systemd-networkd-wireguard.nix
@@ -2,6 +2,7 @@ let generateNodeConf = { lib, pkgs, config, privkpath, pubk, peerId, nodeId, ...
       imports = [ common/user-account.nix ];
       systemd.services.systemd-networkd.environment.SYSTEMD_LOG_LEVEL = "debug";
       networking.useNetworkd = true;
+      networking.useDHCP = false;
       networking.firewall.enable = false;
       virtualisation.vlans = [ 1 ];
       environment.systemPackages = with pkgs; [ wireguard-tools ];