Add SSH port-forwarded test driver wrapper via QEMU_NET_OPTS

Uses SLiRP hostfwd to forward host:2222 -> VM:22, allowing SSH into
test VMs from upterm without TAP/bridge setup. No per-VM config changes
needed, preserves VDE inter-VM networking for future multi-VM tests.

Author: Lillecarl

.github/workflows/test-nixos.yaml

@@ -67,7 +67,7 @@ jobs:
 
       - name: Start nixos test (background)
         run: |
-          nix run --file . nixosTests.containerd.driverInteractive --option sandbox false -- --no-interactive > /tmp/test.log 2>&1 &
+          nix run --file . nixosTestsSSH.containerd.driverInteractive --option sandbox false -- --no-interactive > /tmp/test.log 2>&1 &
           echo $! > /tmp/test.pid
           echo "Test running in background (PID: $(cat /tmp/test.pid))"
           sleep 5

default.nix

@@ -172,6 +172,19 @@ rec {
     };
   };
 
+  # Wrapped test drivers with SSH port forwarding via QEMU_NET_OPTS
+  # Forwards host:2222 → VM:22 through SLiRP so you can SSH into the VM
+  nixosTestsSSH = lib.mapAttrs (
+    _: test:
+    let
+      wrappedDriver = pkgs.writeShellScriptBin "nixos-test-driver" ''
+        export QEMU_NET_OPTS="hostfwd=tcp::2222-:22"
+        exec ${test.driverInteractive}/bin/nixos-test-driver "$@"
+      '';
+    in
+    test // { driverInteractive = wrappedDriver; }
+  ) nixosTests;
+
   lixImage = pkgs.callPackage ./liximage.nix { };
   scratchImage = pkgs.callPackage ./scratchimage.nix { };
 }