nixos/cloud-init: fix hostname and resolvconf configuration

- Fix hostname configuration on proxmox, which uses "hostname" in user-data
instead of "local-hostname" in meta-data.
- Allow setting resolv.conf through cloud-init
- Add tests for new changes
- Add timeouts to make tests fail faster

nixos/modules/services/system/cloud-init.nix

···
            - write-files
            - growpart
            - resizefs
-           - update_etc_hosts
+           - update_hostname
+           - resolv_conf
            - ca-certs
            - rsyslog
            - users-groups

nixos/tests/all-tests.nix

···
   cjdns = handleTest ./cjdns.nix {};
   clickhouse = handleTest ./clickhouse.nix {};
   cloud-init = handleTest ./cloud-init.nix {};
+  cloud-init-hostname = handleTest ./cloud-init-hostname.nix {};
   cntr = handleTestOn ["aarch64-linux" "x86_64-linux"] ./cntr.nix {};
   cockroachdb = handleTestOn ["x86_64-linux"] ./cockroachdb.nix {};
   collectd = handleTest ./collectd.nix {};

nixos/tests/cloud-init-hostname.nix

···
+{ system ? builtins.currentSystem,
+  config ? {},
+  pkgs ? import ../.. { inherit system config; }
+}:
+
+with import ../lib/testing-python.nix { inherit system pkgs; };
+with pkgs.lib;
+
+let
+  # Hostname can also be set through "hostname" in user-data.
+  # This is how proxmox configures hostname through cloud-init.
+  metadataDrive = pkgs.stdenv.mkDerivation {
+    name = "metadata";
+    buildCommand = ''
+      mkdir -p $out/iso
+
+      cat << EOF > $out/iso/user-data
+      #cloud-config
+      hostname: testhostname
+      EOF
+
+      cat << EOF > $out/iso/meta-data
+      instance-id: iid-local02
+      EOF
+
+      ${pkgs.cdrkit}/bin/genisoimage -volid cidata -joliet -rock -o $out/metadata.iso $out/iso
+    '';
+  };
+
+in makeTest {
+  name = "cloud-init-hostname";
+  meta = with pkgs.lib.maintainers; {
+    maintainers = [ lewo illustris ];
+  };
+
+  nodes.machine2 = { ... }: {
+    virtualisation.qemu.options = [ "-cdrom" "${metadataDrive}/metadata.iso" ];
+    services.cloud-init.enable = true;
+    networking.hostName = "";
+  };
+
+  testScript = ''
+    unnamed.wait_for_unit("cloud-final.service")
+    assert "testhostname" in unnamed.succeed("hostname")
+  '';
+}

nixos/tests/cloud-init.nix

···
               gateway: '12.34.56.9'
           - type: nameserver
             address:
-            - '8.8.8.8'
+            - '6.7.8.9'
             search:
             - 'example.com'
       EOF
       ${pkgs.cdrkit}/bin/genisoimage -volid cidata -joliet -rock -o $out/metadata.iso $out/iso
       '';
   };
+
 in makeTest {
   name = "cloud-init";
-  meta = with pkgs.lib.maintainers; {
-    maintainers = [ lewo ];
-    broken = true; # almost always times out after spending many hours
-  };
+  meta.maintainers = with pkgs.lib.maintainers; [ lewo illustris ];
   nodes.machine = { ... }:
   {
     virtualisation.qemu.options = [ "-cdrom" "${metadataDrive}/metadata.iso" ];
···
 
     # we should be able to log in as the root user, as well as the created nixos user
     unnamed.succeed(
-        "ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o IdentityFile=~/.ssh/id_snakeoil root@localhost 'true'"
+        "timeout 10 ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o IdentityFile=~/.ssh/id_snakeoil root@localhost 'true'"
     )
     unnamed.succeed(
-        "ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o IdentityFile=~/.ssh/id_snakeoil nixos@localhost 'true'"
+        "timeout 10 ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o IdentityFile=~/.ssh/id_snakeoil nixos@localhost 'true'"
     )
 
     # test changing hostname via cloud-init worked
     assert (
         unnamed.succeed(
-            "ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o IdentityFile=~/.ssh/id_snakeoil nixos@localhost 'hostname'"
+            "timeout 10 ssh -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no -o IdentityFile=~/.ssh/id_snakeoil nixos@localhost 'hostname'"
         ).strip()
         == "test"
     )
 
+    # check IP and route configs
     assert "default via 12.34.56.9 dev eth0 proto static" in unnamed.succeed("ip route")
     assert "12.34.56.0/24 dev eth0 proto kernel scope link src 12.34.56.78" in unnamed.succeed("ip route")
+
+    # check nameserver and search configs
+    assert "6.7.8.9" in unnamed.succeed("resolvectl status")
+    assert "example.com" in unnamed.succeed("resolvectl status")
+
   '';
 }