nixos/tests/networking: test hostname via DHCP

nixos/modules/services/networking/dhcpcd.nix

@@ -284,7 +284,8 @@ in
           [
             dhcpcd
             config.networking.resolvconf.package
-          ] ++ lib.optional cfg.setHostname (
+          ]
+          ++ lib.optional cfg.setHostname (
             pkgs.writeShellScriptBin "hostname" ''
               ${lib.getExe' pkgs.systemd "hostnamectl"} set-hostname --transient $1
             ''

nixos/tests/networking/networkd-and-scripted.nix

@@ -178,6 +178,29 @@ let
             router.wait_until_succeeds("ping -c 1 fd00:1234:5678:2::2")
       '';
     };
+    dhcpHostname = {
+      name = "hostnameDHCP";
+      nodes.router = router;
+      nodes.client = clientConfig {
+        # use the name given by the DHCP server
+        system.name = "client";
+        networking.hostName = lib.mkForce "";
+        security.polkit.enable = true;
+        virtualisation.interfaces.enp1s0.vlan = 1;
+        networking.interfaces.enp1s0.useDHCP = true;
+      };
+      testScript = ''
+        router.start()
+        router.systemctl("start network-online.target")
+        router.wait_for_unit("network-online.target")
+
+        client.start()
+        client.wait_for_unit("network.target")
+
+        with subtest("Wait until we have received the hostname"):
+            client.wait_until_succeeds("hostname | grep -q 'client1'")
+      '';
+    };
     dhcpOneIf = {
       name = "OneInterfaceDHCP";
       nodes.router = router;

pkgs/by-name/dh/dhcpcd/package.nix

@@ -63,7 +63,12 @@ stdenv.mkDerivation rec {
   ) "[ -e ${placeholder "out"}/lib/dhcpcd/dev/udev.so ]";
 
   passthru.tests = {
-    inherit (nixosTests.networking.scripted) macvlan dhcpSimple dhcpOneIf;
+    inherit (nixosTests.networking.scripted)
+      macvlan
+      dhcpSimple
+      dhcpHostname
+      dhcpOneIf
+      ;
   };
 
   meta = with lib; {