Add openvixdisklib as an open NBD replacement for VMware VDDK.

VDDK is no longer publicly distributed, so this library reverse-engineers
the vSphere NFC path and exposes ConnectEx, Open, Read, and Write without
the proprietary SDK.

Co-authored-by: Cursor <[email protected]>

tests/integration/test_crosscheck.py

@@ -0,0 +1,94 @@
+# Copyright 2026 Cloudbase Solutions Srl
+# All Rights Reserved.
+
+"""Compare writes and reads from VDDK with openvixdisklib."""
+
+from typing import Any, Optional
+
+from openvixdisklib import openvixdisklib as open_vix
+from tests.integration import vixdisklib
+from tests.integration.base import TestBase
+
+
+class CrosscheckTest(TestBase):
+    @classmethod
+    def setUpClass(cls) -> None:
+        """Skip when the bundled VDDK shared library is not present."""
+        cls.require_vddk()
+        super().setUpClass()
+
+    def _connect_extra(self, module: Any) -> Optional[dict[str, Any]]:
+        """Return extra ``connect`` kwargs needed by ``module``."""
+        if module is open_vix:
+            return {"allow_untrusted": self.ALLOW_UNTRUSTED}
+        return None
+
+    def _write_sectors(
+            self,
+            module: Any,
+            payloads: dict[int, bytes]) -> None:
+        """Write one sector at each index using a vixdisklib-compatible module."""
+        handle = module.VixDiskLibHandle(
+            vixdisklib_compatibility_version="8.0",
+            config_path=None)
+        buf = module.get_buffer(self.SECTOR_SIZE)
+        kwargs = self.vixdisklib_connect_kwargs(self._connect_extra(module))
+        with handle.connect(**kwargs) as conn:
+            with handle.open(conn, self.DISK_PATH, flags=0) as disk:
+                for start, data in payloads.items():
+                    buf[:self.SECTOR_SIZE] = data
+                    handle.write(disk, start, 1, buf)
+
+    def _read_sectors(
+            self,
+            module: Any,
+            sectors: tuple[int, ...]) -> dict[int, bytes]:
+        """Read one sector at each index using a vixdisklib-compatible module."""
+        handle = module.VixDiskLibHandle(
+            vixdisklib_compatibility_version="8.0",
+            config_path=None)
+        buf = module.get_buffer(self.SECTOR_SIZE)
+        result: dict[int, bytes] = {}
+        kwargs = self.vixdisklib_connect_kwargs(self._connect_extra(module))
+        with handle.connect(**kwargs) as conn:
+            with handle.open(conn, self.DISK_PATH, flags=0) as disk:
+                for start in sectors:
+                    buf[:self.SECTOR_SIZE] = b"\xa5" * self.SECTOR_SIZE
+                    handle.read(disk, start, 1, buf)
+                    result[start] = buf.raw[:self.SECTOR_SIZE]
+        return result
+
+    def _assert_both_read(
+            self,
+            sectors: tuple[int, ...],
+            expected: dict[int, bytes]) -> None:
+        vddk = self._read_sectors(vixdisklib, sectors)
+        replacement = self._read_sectors(open_vix, sectors)
+        for start in sectors:
+            self.assertEqual(
+                vddk[start], expected[start],
+                f"VDDK mismatch at sector {start}")
+            self.assertEqual(
+                replacement[start], expected[start],
+                f"openvixdisklib mismatch at sector {start}")
+
+    def test_openvixdisklib_matches_vddk_sectors(self) -> None:
+        """Writes from either library must be visible to both readers."""
+        sectors = (0, 1, self.SECTOR_AT_1GB)
+        vddk_payloads = {
+            0: self.pattern_bytes(self.SECTOR_SIZE, b"XCHK-VDDK-S0"),
+            1: self.pattern_bytes(self.SECTOR_SIZE, b"XCHK-VDDK-S1"),
+            self.SECTOR_AT_1GB: self.pattern_bytes(
+                self.SECTOR_SIZE, b"XCHK-VDDK-1G"),
+        }
+        self._write_sectors(vixdisklib, vddk_payloads)
+        self._assert_both_read(sectors, vddk_payloads)
+
+        ovdl_payloads = {
+            0: self.pattern_bytes(self.SECTOR_SIZE, b"XCHK-OVDL-S0"),
+            1: self.pattern_bytes(self.SECTOR_SIZE, b"XCHK-OVDL-S1"),
+            self.SECTOR_AT_1GB: self.pattern_bytes(
+                self.SECTOR_SIZE, b"XCHK-OVDL-1G"),
+        }
+        self._write_sectors(open_vix, ovdl_payloads)
+        self._assert_both_read(sectors, ovdl_payloads)