nixos/tests/mtp: init

Adds a fully fledged NixOS VM integration test which uses jmtpfs and
gvfs to test the functionality of MTP inside of NixOS. It uses USB
device emulation in QEMU to create MTP device(s) which can be tested
against.

Co-authored-by: nixinator <33lockdown33@protonmail.com>

nixos/tests/all-tests.nix

@@ -277,6 +277,7 @@ in
   mosquitto = handleTest ./mosquitto.nix {};
   mpd = handleTest ./mpd.nix {};
   mpv = handleTest ./mpv.nix {};
+  mtp = handleTest ./mtp.nix {};
   mumble = handleTest ./mumble.nix {};
   musescore = handleTest ./musescore.nix {};
   munin = handleTest ./munin.nix {};

nixos/tests/mtp.nix

@@ -0,0 +1,108 @@
+import ./make-test-python.nix ({ pkgs, ... }: {
+  name = "mtp";
+  meta = with pkgs.lib.maintainers; {
+    maintainers = [ matthewcroughan nixinator ];
+  };
+
+  nodes =
+  {
+    client = { config, pkgs, ... }: {
+      # DBUS runs only once a user session is created, which means a user has to
+      # login. Here, we log in as root. Once logged in, the gvfs-daemon service runs
+      # as UID 0 in User-0.service
+      services.getty.autologinUser = "root";
+
+      # XDG_RUNTIME_DIR is needed for running systemd-user services such as
+      # gvfs-daemon as root.
+      environment.variables.XDG_RUNTIME_DIR = "/run/user/0";
+
+      environment.systemPackages = with pkgs; [ usbutils glib jmtpfs tree ];
+      services.gvfs.enable = true;
+
+      # Creates a usb-mtp device inside the VM, which is mapped to the host's
+      # /tmp folder, it is able to write files to this location, but only has
+      # permissions to read its own creations.
+      virtualisation.qemu.options = [
+        "-usb"
+        "-device usb-mtp,rootdir=/tmp,readonly=false"
+      ];
+    };
+  };
+
+
+  testScript = { nodes, ... }:
+    let
+      # Creates a list of QEMU MTP devices matching USB ID (46f4:0004). This
+      # value can be sourced in a shell script. This is so we can loop over the
+      # devices we find, as this test may want to use more than one MTP device
+      # in future.
+      mtpDevices = pkgs.writeScript "mtpDevices.sh" ''
+        export mtpDevices=$(lsusb -d 46f4:0004 | awk {'print $2","$4'} | sed 's/[:-]/ /g')
+      '';
+      # Qemu is only capable of creating an MTP device with Picture Transfer
+      # Protocol. This means that gvfs must use gphoto2:// rather than mtp://
+      # when mounting.
+      # https://github.com/qemu/qemu/blob/970bc16f60937bcfd334f14c614bd4407c247961/hw/usb/dev-mtp.c#L278
+      gvfs = rec {
+        mountAllMtpDevices = pkgs.writeScript "mountAllMtpDevices.sh" ''
+          set -e
+          source ${mtpDevices}
+          for i in $mtpDevices
+          do
+            gio mount "gphoto2://[usb:$i]/"
+          done
+        '';
+        unmountAllMtpDevices = pkgs.writeScript "unmountAllMtpDevices.sh" ''
+          set -e
+          source ${mtpDevices}
+          for i in $mtpDevices
+          do
+            gio mount -u "gphoto2://[usb:$i]/"
+          done
+        '';
+        # gvfsTest:
+        # 1. Creates a 10M test file
+        # 2. Copies it to the device using GIO tools
+        # 3. Checks for corruption with `diff`
+        # 4. Removes the file, then unmounts the disks.
+        gvfsTest = pkgs.writeScript "gvfsTest.sh" ''
+          set -e
+          source ${mtpDevices}
+          ${mountAllMtpDevices}
+          dd if=/dev/urandom of=testFile10M bs=1M count=10
+          for i in $mtpDevices
+          do
+            gio copy ./testFile10M gphoto2://[usb:$i]/
+            ls -lah /run/user/0/gvfs/*/testFile10M
+            gio remove gphoto2://[usb:$i]/testFile10M
+          done
+          ${unmountAllMtpDevices}
+        '';
+      };
+      jmtpfs = {
+        # jmtpfsTest:
+        # 1. Mounts the device on a dir named `phone` using jmtpfs
+        # 2. Puts the current Nixpkgs libmtp version into a file
+        # 3. Checks for corruption with `diff`
+        # 4. Prints the directory tree
+        jmtpfsTest = pkgs.writeScript "jmtpfsTest.sh" ''
+          mkdir phone
+          jmtpfs phone
+          echo "${pkgs.libmtp.version}" > phone/tmp/testFile
+          echo "${pkgs.libmtp.version}" > testFile
+          diff phone/tmp/testFile testFile
+          tree phone
+        '';
+      };
+    in
+    # Using >&2 allows the results of the scripts to be printed to the terminal
+    # when building this test with Nix. Scripts would otherwise complete
+    # silently.
+    ''
+    start_all()
+    client.wait_for_unit("multi-user.target")
+    client.wait_for_unit("dbus.service")
+    client.succeed("${gvfs.gvfsTest} >&2")
+    client.succeed("${jmtpfs.jmtpfsTest} >&2")
+  '';
+})