nixos/boot: rename network interfaces already in stage 1

nixos/doc/manual/release-notes/rl-1809.xml

@@ -200,6 +200,21 @@ $ nix-instantiate -E '(import <nixpkgsunstable> {}).gitFull'
       from your config without any issues.
     </para>
    </listitem>
+   <listitem>
+    <para>
+     The following changes apply if <literal>system.stateVersion</literal> is
+     changed to 18.09 or higher. For <literal>system.stateVersion = "18.03"</literal> or lower
+     the old behavior is preserved.
+    </para>
+    <itemizedlist>
+     <listitem>
+      <para>
+        If predictable interface names are enabled (<literal>networking.usePredictableInterfaceNames = true </literal>), interfaces are already renamed in Stage 1 (initrd).
+        <emphasis role="strong">This may break existing configurations that require networking in Stage 1 (initrd) to boot. In the worst case, your system may become unbootable.</emphasis> Before updating <literal>stateVersion</literal> to 18.09 or higher, make sure your configuration is not affected.
+      </para>
+     </listitem>
+    </itemizedlist>
+   </listitem>
   </itemizedlist>
  </section>
 

nixos/modules/services/hardware/udev.nix

@@ -266,6 +266,9 @@ in
         change randomly across reboots; for instance, you may find
         <literal>eth0</literal> and <literal>eth1</literal> flipping
         unpredictably.
+        For newer configurations with <literal>system.stateVersion >= 18.09</literal>,
+        interfaces are renamed to predictable names in Stage 1 (initrd), and
+        changing this option's value requires a reboot to take effect.
       '';
     };
 

nixos/modules/system/boot/networkd.nix

@@ -844,7 +844,10 @@ in
     systemd.services.systemd-networkd = {
       wantedBy = [ "multi-user.target" ];
       restartTriggers = map (f: f.source) (unitFiles);
+    } // optionalAttrs (versionOlder config.system.stateVersion "18.09") {
       # prevent race condition with interface renaming (#39069)
+      # This is not necessary for newer configs (stateVersion>=18.09)
+      # since they do interface renaming in stage 1
       requires = [ "systemd-udev-settle.service" ];
       after = [ "systemd-udev-settle.service" ];
     };

nixos/modules/system/boot/stage-1.nix

@@ -195,9 +195,11 @@ let
       fi
     ''; # */
 
+  # use same rules as stage 2 for renaming network interfaces to predictable names
+  netSetupLinkRules = ../../services/hardware/80-net-setup-link.rules;
 
   udevRules = pkgs.runCommand "udev-rules"
-    { allowedReferences = [ extraUtils ]; }
+    { allowedReferences = [ netSetupLinkRules extraUtils ]; }
     ''
       mkdir -p $out
 
@@ -206,6 +208,12 @@ let
       cp -v ${udev}/lib/udev/rules.d/60-cdrom_id.rules $out/
       cp -v ${udev}/lib/udev/rules.d/60-persistent-storage.rules $out/
       cp -v ${udev}/lib/udev/rules.d/80-drivers.rules $out/
+      # rename interfaces to predictable names in stage 1 for newer configs
+      ${optionalString (config.networking.usePredictableInterfaceNames &&
+                        lib.versionAtLeast config.system.stateVersion "18.09") ''
+        cp -v ${udev}/lib/udev/rules.d/75-net-description.rules $out/
+        cp -v ${netSetupLinkRules} $out/80-net-setup-link.rules
+      ''}
       cp -v ${pkgs.lvm2}/lib/udev/rules.d/*.rules $out/
       ${config.boot.initrd.extraUdevRulesCommands}
 

nixos/release.nix

@@ -314,7 +314,7 @@ in rec {
   tests.hydra = callTest tests/hydra {};
   tests.i3wm = callTest tests/i3wm.nix {};
   tests.iftop = callTest tests/iftop.nix {};
-  tests.initrd-network-ssh = callTest tests/initrd-network-ssh {};
+  tests.initrd-network-ssh = callSubTests tests/initrd-network-ssh {};
   tests.installer = callSubTests tests/installer.nix {};
   tests.influxdb = callTest tests/influxdb.nix {};
   tests.ipv6 = callTest tests/ipv6.nix {};

nixos/tests/initrd-network-ssh/default.nix

@@ -1,59 +1,76 @@
-import ../make-test.nix ({ lib, ... }:
+{ system ? builtins.currentSystem }:
 
-{
-  name = "initrd-network-ssh";
-  meta = with lib.maintainers; {
-    maintainers = [ willibutz ];
-  };
+let
+  inherit (import ../../lib/testing.nix { inherit system; }) makeTest pkgs;
+in
+  with pkgs; lib.listToAttrs ( map (predictable: {
 
-  nodes = with lib; rec {
-    server =
-      { config, ... }:
-      {
-        boot.kernelParams = [
-          "ip=${config.networking.primaryIPAddress}:::255.255.255.0::eth1:none"
-        ];
-        boot.initrd.network = {
-          enable = true;
-          ssh = {
-            enable = true;
-            authorizedKeys = [ "${readFile ./openssh.pub}" ];
-            port = 22;
-            hostRSAKey = ./dropbear.priv;
-          };
-        };
-        boot.initrd.preLVMCommands = ''
-          while true; do
-            if [ -f fnord ]; then
-              poweroff
-            fi
-            sleep 1
-          done
-        '';
+    name = if predictable then "predictable" else "unpredictable";
+
+    value = makeTest {
+      name = "initrd-network-ssh"+ lib.optionalString predictable "predictable";
+      meta = with lib.maintainers; {
+        maintainers = [ willibutz xeji ];
       };
 
-    client =
-      { config, ... }:
-      {
-        environment.etc.knownHosts = {
-          text = concatStrings [
-            "server,"
-            "${toString (head (splitString " " (
-              toString (elemAt (splitString "\n" config.networking.extraHosts) 2)
-            )))} "
-            "${readFile ./dropbear.pub}"
-          ];
-        };
+      nodes = with lib;
+        let interface2 = if predictable then "ens4" else "eth1";
+        in rec {
+        server =
+          { config, ... }:
+          {
+            # for stateVersion < 18.09 this doesn't make a difference in initrd
+            system.stateVersion = "18.09";
+            networking.usePredictableInterfaceNames = mkForce predictable;
+            boot.kernelParams = [
+              "ip=${config.networking.primaryIPAddress}:::255.255.255.0::${interface2}:none"
+            ];
+            boot.initrd.network = {
+              enable = true;
+              # for initrd networking with predictable interface names,
+              # udhcpc must be given the name as an argument
+              udhcpc.extraArgs = [ (lib.optionalString predictable "-i ${interface2}")];
+              ssh = {
+                enable = true;
+                authorizedKeys = [ "${readFile ./openssh.pub}" ];
+                port = 22;
+                hostRSAKey = ./dropbear.priv;
+              };
+            };
+            boot.initrd.preLVMCommands = ''
+              while true; do
+                if [ -f fnord ]; then
+                  poweroff
+                fi
+                sleep 1
+              done
+            '';
+          };
+
+        client =
+          { config, ... }:
+          {
+            environment.etc.knownHosts = {
+              text = concatStrings [
+                "server,"
+                "${toString (head (splitString " " (
+                  toString (elemAt (splitString "\n" config.networking.extraHosts) 2)
+                )))} "
+                "${readFile ./dropbear.pub}"
+              ];
+            };
+          };
       };
-  };
 
-  testScript = ''
-    startAll;
-    $client->waitForUnit("network.target");
-    $client->copyFileFromHost("${./openssh.priv}","/etc/sshKey");
-    $client->succeed("chmod 0600 /etc/sshKey");
-    $client->waitUntilSucceeds("ping -c 1 server");
-    $client->succeed("ssh -i /etc/sshKey -o UserKnownHostsFile=/etc/knownHosts server 'touch /fnord'");
-    $client->shutdown;
-  '';
-})
+      testScript = ''
+        $client->waitForUnit("network.target");
+        $client->copyFileFromHost("${./openssh.priv}","/etc/sshKey");
+        $client->succeed("chmod 0600 /etc/sshKey");
+        $server->start;
+        $client->waitUntilSucceeds("ping -c 1 server");
+        $client->succeed("ssh -i /etc/sshKey -o UserKnownHostsFile=/etc/knownHosts server 'touch /fnord'");
+        $client->shutdown;
+      '';
+    };
+  }) [false true] 
+)

nixos/tests/predictable-interface-names.nix

@@ -13,6 +13,11 @@ in pkgs.lib.listToAttrs (pkgs.lib.crossLists (predictable: withNetworkd: {
       networking.usePredictableInterfaceNames = lib.mkForce predictable;
       networking.useNetworkd = withNetworkd;
       networking.dhcpcd.enable = !withNetworkd;
+      # So we can see the initrd device names in the log
+      # although we don't add an automated test here
+      boot.initrd.network.enable = true;
+      # test new behavior for 18.09
+      system.stateVersion = "18.09";
     };
 
     testScript = ''