Test all IOU requirements at VM startup

This allow user to create the node and upload the image after

gns3server/modules/iou/iou_vm.py

@@ -142,27 +142,6 @@ class IOUVM(BaseVM):
             if os.path.isfile(fix_path):
                 self._path = fix_path
 
-        if not os.path.isfile(self._path) or not os.path.exists(self._path):
-            if os.path.islink(self._path):
-                raise IOUError("IOU image '{}' linked to '{}' is not accessible".format(self._path, os.path.realpath(self._path)))
-            else:
-                raise IOUError("IOU image '{}' is not accessible".format(self._path))
-
-        try:
-            with open(self._path, "rb") as f:
-                # read the first 7 bytes of the file.
-                elf_header_start = f.read(7)
-        except OSError as e:
-            raise IOUError("Cannot read ELF header for IOU image '{}': {}".format(self._path, e))
-
-        # IOU images must start with the ELF magic number, be 32-bit, little endian
-        # and have an ELF version of 1 normal IOS image are big endian!
-        if elf_header_start != b'\x7fELF\x01\x01\x01':
-            raise IOUError("'{}' is not a valid IOU image".format(self._path))
-
-        if not os.access(self._path, os.X_OK):
-            raise IOUError("IOU image '{}' is not executable".format(self._path))
-
     @property
     def use_default_iou_values(self):
         """
@@ -189,9 +168,30 @@ class IOUVM(BaseVM):
 
     def _check_requirements(self):
         """
-        Checks if IOUYAP executable is available.
+        Checks if IOUYAP executable is available and if image is accessible.
         """
 
+        if not os.path.isfile(self._path) or not os.path.exists(self._path):
+            if os.path.islink(self._path):
+                raise IOUError("IOU image '{}' linked to '{}' is not accessible".format(self._path, os.path.realpath(self._path)))
+            else:
+                raise IOUError("IOU image '{}' is not accessible".format(self._path))
+
+        try:
+            with open(self._path, "rb") as f:
+                # read the first 7 bytes of the file.
+                elf_header_start = f.read(7)
+        except OSError as e:
+            raise IOUError("Cannot read ELF header for IOU image '{}': {}".format(self._path, e))
+
+        # IOU images must start with the ELF magic number, be 32-bit, little endian
+        # and have an ELF version of 1 normal IOS image are big endian!
+        if elf_header_start != b'\x7fELF\x01\x01\x01':
+            raise IOUError("'{}' is not a valid IOU image".format(self._path))
+
+        if not os.access(self._path, os.X_OK):
+            raise IOUError("IOU image '{}' is not executable".format(self._path))
+
         path = self.iouyap_path
         if not path:
             raise IOUError("No path to iouyap program has been set")

tests/modules/iou/test_iou_vm.py

@@ -96,9 +96,10 @@ def test_vm_startup_config_content(project, manager):
 
 
 @patch("gns3server.config.Config.get_section_config", return_value={"iouyap_path": "/bin/test_fake"})
-def test_vm_invalid_iouyap_path(project, manager, loop):
+def test_vm_invalid_iouyap_path(project, manager, loop, fake_iou_bin):
     with pytest.raises(IOUError):
         vm = IOUVM("test", "00010203-0405-0607-0809-0a0b0c0d0e0e", project, manager)
+        vm.path = fake_iou_bin
         loop.run_until_complete(asyncio.async(vm.start()))
 
 
@@ -231,12 +232,14 @@ def test_path_invalid_bin(vm, tmpdir):
     path = str(tmpdir / "test.bin")
     with pytest.raises(IOUError):
         vm.path = path
+        vm._check_requirements()
 
     with open(path, "w+") as f:
         f.write("BUG")
 
     with pytest.raises(IOUError):
         vm.path = path
+        vm._check_requirements()
 
 
 def test_create_netmap_config(vm):
@@ -255,6 +258,7 @@ def test_build_command(vm, loop):
 
     assert loop.run_until_complete(asyncio.async(vm._build_command())) == [vm.path, "-L", str(vm.application_id)]
 
+
 def test_get_startup_config(vm):
 
     content = "service timestamps debug datetime msec\nservice timestamps log datetime msec\nno service password-encryption"