T7365: add POSIX-type lock to vyconf_session.commit for compatibility

We maintain compatibility with the legacy commit lock file until all
other references are resolved; this requires a POSIX-type lock instead
of the BSD-type lock of vyos.utils.locking.

2 files changed, 47 insertions, 1 deletions

diff --git a/python/vyos/utils/commit.py b/python/vyos/utils/commit.py
index 2b014c939..9167c78d2 100644
--- a/python/vyos/utils/commit.py
+++ b/python/vyos/utils/commit.py
@@ -15,6 +15,8 @@
 
 # pylint: disable=import-outside-toplevel
 
+from typing import IO
+
 
 def commit_in_progress():
     """Not to be used in normal op mode scripts!"""
@@ -64,3 +66,38 @@ def wait_for_commit_lock():
     # Very synchronous approach to multiprocessing
     while commit_in_progress():
         sleep(1)
+
+
+# For transitional compatibility with the legacy commit locking mechanism,
+# we require a lockf/fcntl (POSIX-type) lock, hence the following in place
+# of vyos.utils.locking
+
+
+def acquire_commit_lock_file() -> tuple[IO, str]:
+    import fcntl
+    from pathlib import Path
+    from vyos.defaults import commit_lock
+
+    try:
+        # pylint: disable=consider-using-with
+        lock_fd = Path(commit_lock).open('w')
+    except IOError as e:
+        out = f'Critical error opening commit lock file {e}'
+        return None, out
+
+    try:
+        fcntl.lockf(lock_fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        return lock_fd, ''
+    except IOError:
+        out = 'Configuration system locked by another commit in progress'
+        lock_fd.close()
+        return None, out
+
+
+def release_commit_lock_file(file_descr):
+    import fcntl
+
+    if file_descr is None:
+        return
+    fcntl.lockf(file_descr, fcntl.LOCK_UN)
+    file_descr.close()
diff --git a/python/vyos/vyconf_session.py b/python/vyos/vyconf_session.py
index 077952a9f..4250f0cfb 100644
--- a/python/vyos/vyconf_session.py
+++ b/python/vyos/vyconf_session.py
@@ -26,6 +26,9 @@ from vyos.migrate import ConfigMigrate
 from vyos.migrate import ConfigMigrateError
 from vyos.component_version import append_system_version
 from vyos.utils.session import in_config_session
+from vyos.proto.vyconf_proto import Errnum
+from vyos.utils.commit import acquire_commit_lock_file
+from vyos.utils.commit import release_commit_lock_file
 
 
 class VyconfSessionError(Exception):
@@ -138,8 +141,14 @@ class VyconfSession:
     @raise_exception
     @config_mode
     def commit(self) -> tuple[str, int]:
+        lock_fd, out = acquire_commit_lock_file()
+        if lock_fd is None:
+            return out, Errnum.COMMIT_IN_PROGRESS
+
         out = vyconf_client.send_request('commit', token=self.__token)
-        return output(out), out.status
+        release_commit_lock_file(lock_fd)
+
+        return self.output(out), out.status
 
     @raise_exception
     @config_mode