Fix DFS recurision for missing files (#239)

The code that handles a missing path does not currently record existing
DFS target servers that have been tried resulting in a recursion error.
By ensuring a DFS target is only retried if it hasn't already it should
avoid this recursion problem.

Fixes: #228

CHANGELOG.md

@@ -5,6 +5,7 @@
 * Fix up pre authenticated session id lookups that were failing with Linux ksmbd
 * Removes `logging.NullHandler()` being set in the root `smbprotocol` namespace
 * Adds basic support for remote to local and vice versa file operations with `smbclient.shutil.copytree`
+* Fixes DFS infinite recursion error when dealing with a file that does not exist on a DFS namespace
 
 ## 1.10.1 - 2022-11-14
 

src/smbclient/_io.py

@@ -244,6 +244,7 @@ def __init__(self, raw):
         self.raw = raw
         self.results = None
         self._actions = []
+        self._attempted_dfs_paths = set()
 
     def __add__(self, other):
         send_msg = other[0]
@@ -306,6 +307,14 @@ def commit(self):
                         if smb_open.tree_connect.share_name == self.raw.fd.tree_connect.share_name:
                             continue
 
+                        # Ensure we don't continuously try the same DFS referral targets if it's already been attempted.
+                        # https://github.com/jborean93/smbprotocol/issues/228
+                        tested_path = f"{smb_open.tree_connect.share_name}{smb_open.file_name}".lower()
+                        if tested_path in self._attempted_dfs_paths:
+                            continue
+
+                        self._attempted_dfs_paths.add(tested_path)
+
                         self.raw.fd = smb_open
 
                         # In case this is a transaction with an explicit open we want to reopen it with the new params

tests/test_smbclient_os.py

@@ -2131,3 +2131,10 @@ def test_broken_dfs_path(smb_real):
     # error and that it doesn't continuously loop.
     with pytest.raises(SMBOSError):
         smbclient.listdir(dfs_path, username=smb_real[0], password=smb_real[1], port=smb_real[3])
+
+
+def test_dfs_nonexisting_path(smb_dfs_share):
+    fake_file = ntpath.join(smb_dfs_share, "missing file.txt")
+
+    with pytest.raises(SMBOSError):
+        smbclient.lstat(fake_file)