Merge pull request #4574 from jestabro/merge-config

T7499: update config merge tools

14 files changed, 330 insertions, 197 deletions

diff --git a/libvyosconfig b/libvyosconfig
-Subproject f632edbc947fbcda1916ababacc5f2659cf6cfb
+Subproject 73600f99aa11f01e3f8148da2212abf51a76663
diff --git a/python/vyos/config.py b/python/vyos/config.py
index 6ba8834cb..6f7c76ca7 100644
--- a/python/vyos/config.py
+++ b/python/vyos/config.py
@@ -134,9 +134,11 @@ class Config(object):
     subtrees.
     """
     def __init__(self, session_env=None, config_source=None):
+        self.vyconf_session = None
         if config_source is None:
             if vyconf_backend() and boot_configuration_complete():
                 self._config_source = ConfigSourceVyconfSession(session_env)
+                self.vyconf_session = self._config_source._vyconf_session
             else:
                 self._config_source = ConfigSourceSession(session_env)
         else:
diff --git a/python/vyos/configsession.py b/python/vyos/configsession.py
index 216069992..50f93f890 100644
--- a/python/vyos/configsession.py
+++ b/python/vyos/configsession.py
@@ -182,8 +182,9 @@ class ConfigSession(object):
         self.__run_command([CLI_SHELL_API, 'setupSession'])
 
         if vyconf_backend() and boot_configuration_complete():
-            self._vyconf_session = VyconfSession(pid=session_id,
-                                                 on_error=ConfigSessionError)
+            self._vyconf_session = VyconfSession(
+                pid=session_id, on_error=ConfigSessionError
+            )
         else:
             self._vyconf_session = None
 
@@ -342,7 +343,7 @@ class ConfigSession(object):
         if self._vyconf_session is None:
             out = self.__run_command(LOAD_CONFIG + [file_path])
         else:
-            out, _ = self._vyconf_session.load_config(file=file_path)
+            out, _ = self._vyconf_session.load_config(file_name=file_path)
 
         return out
 
@@ -359,15 +360,18 @@ class ConfigSession(object):
         if self._vyconf_session is None:
             out = self.__run_command(MIGRATE_LOAD_CONFIG + [file_path])
         else:
-            out, _ = self._vyconf_session.load_config(file=file_path, migrate=True)
+            out, _ = self._vyconf_session.load_config(file_name=file_path, migrate=True)
 
         return out
 
-    def merge_config(self, file_path):
+    def merge_config(self, file_path, destructive=False):
         if self._vyconf_session is None:
-            out = self.__run_command(MERGE_CONFIG + [file_path])
+            destr = ['--destructive'] if destructive else []
+            out = self.__run_command(MERGE_CONFIG + [file_path] + destr)
         else:
-            out = 'unimplemented'
+            out, _ = self._vyconf_session.merge_config(
+                file_name=file_path, destructive=destructive
+            )
 
         return out
 
diff --git a/python/vyos/configsource.py b/python/vyos/configsource.py
index 3931f1295..949216722 100644
--- a/python/vyos/configsource.py
+++ b/python/vyos/configsource.py
@@ -345,6 +345,11 @@ class ConfigSourceVyconfSession(ConfigSource):
         self._running_config = ConfigTree(internal=self.running_cache_path)
         self._session_config = ConfigTree(internal=self.session_cache_path)
 
+        if os.path.isfile(self.running_cache_path):
+            os.remove(self.running_cache_path)
+        if os.path.isfile(self.session_cache_path):
+            os.remove(self.session_cache_path)
+
         # N.B. level not yet implemented pending integration with legacy CLI
         # cf. T7374
         self._level = []
diff --git a/python/vyos/configtree.py b/python/vyos/configtree.py
index 9b3755841..ba3f1e368 100644
--- a/python/vyos/configtree.py
+++ b/python/vyos/configtree.py
@@ -233,7 +233,7 @@ class ConfigTree(object):
         return self.__version
 
     def write_cache(self, file_name):
-        self.__write_internal(self._get_config(), file_name)
+        self.__write_internal(self._get_config(), file_name.encode())
 
     def to_string(self, ordered_values=False, no_version=False):
         config_string = self.__to_string(self.__config, ordered_values).decode()
@@ -499,6 +499,28 @@ def union(left, right, libpath=LIBPATH):
     return tree
 
 
+def merge(left, right, destructive=False, libpath=LIBPATH):
+    if left is None:
+        left = ConfigTree(config_string='\n')
+    if right is None:
+        right = ConfigTree(config_string='\n')
+    if not (isinstance(left, ConfigTree) and isinstance(right, ConfigTree)):
+        raise TypeError('Arguments must be instances of ConfigTree')
+
+    __lib = cdll.LoadLibrary(libpath)
+    __tree_merge = __lib.tree_merge
+    __tree_merge.argtypes = [c_bool, c_void_p, c_void_p]
+    __tree_merge.restype = c_void_p
+    __get_error = __lib.get_error
+    __get_error.argtypes = []
+    __get_error.restype = c_char_p
+
+    res = __tree_merge(destructive, left._get_config(), right._get_config())
+    tree = ConfigTree(address=res)
+
+    return tree
+
+
 def mask_inclusive(left, right, libpath=LIBPATH):
     if not (isinstance(left, ConfigTree) and isinstance(right, ConfigTree)):
         raise TypeError('Arguments must be instances of ConfigTree')
diff --git a/python/vyos/proto/vyconf_pb2.py b/python/vyos/proto/vyconf_pb2.py
index 3d5042888..4bf0eb2e0 100644
--- a/python/vyos/proto/vyconf_pb2.py
+++ b/python/vyos/proto/vyconf_pb2.py
@@ -13,17 +13,17 @@ _sym_db = _symbol_database.Default()
 
 
 
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\x01(\x05\x1a\x35\n\x06Rename\x12\x11\n\tEditLevel\x18\x01 \x03(\t\x12\x0c\n\x04\x46rom\x18\x02 \x02(\t\x12\n\n\x02To\x18\x03 \x02(\t\x1a\x33\n\x04\x43opy\x12\x11\n\tEditLevel\x18\x01 \x03(\t\x12\x0c\n\x04\x46rom\x18\x02 \x02(\t\x12\n\n\x02To\x18\x03 \x02(\t\x1a(\n\x07\x43omment\x12\x0c\n\x04Path\x18\x01 \x03(\t\x12\x0f\n\x07\x43omment\x18\x02 \x02(\t\x1aR\n\x06\x43ommit\x12\x0f\n\x07\x43onfirm\x18\x01 \x01(\x08\x12\x16\n\x0e\x43onfirmTimeout\x18\x02 \x01(\x05\x12\x0f\n\x07\x43omment\x18\x03 \x01(\t\x12\x0e\n\x06\x44ryRun\x18\x04 \x01(\x08\x1a\x1c\n\x08Rollback\x12\x10\n\x08Revision\x18\x01 \x02(\x05\x1aO\n\x04Load\x12\x10\n\x08Location\x18\x01 \x02(\t\x12\x0e\n\x06\x63\x61\x63hed\x18\x02 \x02(\x08\x12%\n\x06\x66ormat\x18\x03 \x01(\x0e\x32\x15.Request.ConfigFormat\x1aU\n\x05Merge\x12\x10\n\x08Location\x18\x01 \x02(\t\x12\x13\n\x0b\x64\x65structive\x18\x02 \x02(\x08\x12%\n\x06\x66ormat\x18\x03 \x01(\x0e\x32\x15.Request.ConfigFormat\x1a?\n\x04Save\x12\x10\n\x08Location\x18\x01 \x02(\t\x12%\n\x06\x66ormat\x18\x02 \x01(\x0e\x32\x15.Request.ConfigFormat\x1a\x41\n\nShowConfig\x12\x0c\n\x04Path\x18\x01 \x03(\t\x12%\n\x06\x66ormat\x18\x02 \x01(\x0e\x32\x15.Request.ConfigFormat\x1a\x16\n\x06\x45xists\x12\x0c\n\x04Path\x18\x01 \x03(\t\x1a\x46\n\x08GetValue\x12\x0c\n\x04Path\x18\x01 \x03(\t\x12,\n\routput_format\x18\x02 \x01(\x0e\x32\x15.Request.OutputFormat\x1aG\n\tGetValues\x12\x0c\n\x04Path\x18\x01 \x03(\t\x12,\n\routput_format\x18\x02 \x01(\x0e\x32\x15.Request.OutputFormat\x1aJ\n\x0cListChildren\x12\x0c\n\x04Path\x18\x01 \x03(\t\x12,\n\routput_format\x18\x02 \x01(\x0e\x32\x15.Request.OutputFormat\x1aG\n\tRunOpMode\x12\x0c\n\x04Path\x18\x01 \x03(\t\x12,\n\routput_format\x18\x02 \x01(\x0e\x32\x15.Request.OutputFormat\x1a\t\n\x07\x43onfirm\x1a\x46\n\x16\x45nterConfigurationMode\x12\x11\n\tExclusive\x18\x01 \x02(\x08\x12\x19\n\x11OverrideExclusive\x18\x02 \x02(\x08\x1a\x17\n\x15\x45xitConfigurationMode\x1a#\n\rReloadReftree\x12\x12\n\nOnBehalfOf\x18\x01 \x01(\x05\"#\n\x0c\x43onfigFormat\x12\t\n\x05\x43URLY\x10\x00\x12\x08\n\x04JSON\x10\x01\")\n\x0cOutputFormat\x12\x0c\n\x08OutPlain\x10\x00\x12\x0b\n\x07OutJSON\x10\x01\x42\x05\n\x03msg\";\n\x0fRequestEnvelope\x12\r\n\x05token\x18\x01 \x01(\t\x12\x19\n\x07request\x18\x02 \x02(\x0b\x32\x08.Request\"S\n\x08Response\x12\x17\n\x06status\x18\x01 \x02(\x0e\x32\x07.Errnum\x12\x0e\n\x06output\x18\x02 \x01(\t\x12\r\n\x05\x65rror\x18\x03 \x01(\t\x12\x0f\n\x07warning\x18\x04 \x01(\t*\xd2\x01\n\x06\x45rrnum\x12\x0b\n\x07SUCCESS\x10\x00\x12\x08\n\x04\x46\x41IL\x10\x01\x12\x10\n\x0cINVALID_PATH\x10\x02\x12\x11\n\rINVALID_VALUE\x10\x03\x12\x16\n\x12\x43OMMIT_IN_PROGRESS\x10\x04\x12\x18\n\x14\x43ONFIGURATION_LOCKED\x10\x05\x12\x12\n\x0eINTERNAL_ERROR\x10\x06\x12\x15\n\x11PERMISSION_DENIED\x10\x07\x12\x17\n\x13PATH_ALREADY_EXISTS\x10\x08\x12\x16\n\x12UNCOMMITED_CHANGES\x10\t')
 
 _builder.BuildMessageAndEnumDescriptors(DESCRIPTOR, globals())
 _builder.BuildTopDescriptorsAndMessages(DESCRIPTOR, 'vyconf_pb2', globals())
 if _descriptor._USE_C_DESCRIPTORS == False:
 
   DESCRIPTOR._options = None
-  _ERRNUM._serialized_start=2863
-  _ERRNUM._serialized_end=3073
+  _ERRNUM._serialized_start=2900
+  _ERRNUM._serialized_end=3110
   _REQUEST._serialized_start=17
-  _REQUEST._serialized_end=2714
+  _REQUEST._serialized_end=2751
   _REQUEST_PROMPT._serialized_start=1237
   _REQUEST_PROMPT._serialized_end=1245
   _REQUEST_SETUPSESSION._serialized_start=1247
@@ -57,37 +57,37 @@ if _descriptor._USE_C_DESCRIPTORS == False:
   _REQUEST_ROLLBACK._serialized_start=1873
   _REQUEST_ROLLBACK._serialized_end=1901
   _REQUEST_LOAD._serialized_start=1903
-  _REQUEST_LOAD._serialized_end=1966
-  _REQUEST_MERGE._serialized_start=1968
-  _REQUEST_MERGE._serialized_end=2032
-  _REQUEST_SAVE._serialized_start=2034
-  _REQUEST_SAVE._serialized_end=2097
-  _REQUEST_SHOWCONFIG._serialized_start=2099
-  _REQUEST_SHOWCONFIG._serialized_end=2164
-  _REQUEST_EXISTS._serialized_start=2166
-  _REQUEST_EXISTS._serialized_end=2188
-  _REQUEST_GETVALUE._serialized_start=2190
-  _REQUEST_GETVALUE._serialized_end=2260
-  _REQUEST_GETVALUES._serialized_start=2262
-  _REQUEST_GETVALUES._serialized_end=2333
-  _REQUEST_LISTCHILDREN._serialized_start=2335
-  _REQUEST_LISTCHILDREN._serialized_end=2409
-  _REQUEST_RUNOPMODE._serialized_start=2411
-  _REQUEST_RUNOPMODE._serialized_end=2482
+  _REQUEST_LOAD._serialized_end=1982
+  _REQUEST_MERGE._serialized_start=1984
+  _REQUEST_MERGE._serialized_end=2069
+  _REQUEST_SAVE._serialized_start=2071
+  _REQUEST_SAVE._serialized_end=2134
+  _REQUEST_SHOWCONFIG._serialized_start=2136
+  _REQUEST_SHOWCONFIG._serialized_end=2201
+  _REQUEST_EXISTS._serialized_start=2203
+  _REQUEST_EXISTS._serialized_end=2225
+  _REQUEST_GETVALUE._serialized_start=2227
+  _REQUEST_GETVALUE._serialized_end=2297
+  _REQUEST_GETVALUES._serialized_start=2299
+  _REQUEST_GETVALUES._serialized_end=2370
+  _REQUEST_LISTCHILDREN._serialized_start=2372
+  _REQUEST_LISTCHILDREN._serialized_end=2446
+  _REQUEST_RUNOPMODE._serialized_start=2448
+  _REQUEST_RUNOPMODE._serialized_end=2519
   _REQUEST_CONFIRM._serialized_start=1799
   _REQUEST_CONFIRM._serialized_end=1808
-  _REQUEST_ENTERCONFIGURATIONMODE._serialized_start=2495
-  _REQUEST_ENTERCONFIGURATIONMODE._serialized_end=2565
-  _REQUEST_EXITCONFIGURATIONMODE._serialized_start=2567
-  _REQUEST_EXITCONFIGURATIONMODE._serialized_end=2590
-  _REQUEST_RELOADREFTREE._serialized_start=2592
-  _REQUEST_RELOADREFTREE._serialized_end=2627
-  _REQUEST_CONFIGFORMAT._serialized_start=2629
-  _REQUEST_CONFIGFORMAT._serialized_end=2664
-  _REQUEST_OUTPUTFORMAT._serialized_start=2666
-  _REQUEST_OUTPUTFORMAT._serialized_end=2707
-  _REQUESTENVELOPE._serialized_start=2716
-  _REQUESTENVELOPE._serialized_end=2775
-  _RESPONSE._serialized_start=2777
-  _RESPONSE._serialized_end=2860
+  _REQUEST_ENTERCONFIGURATIONMODE._serialized_start=2532
+  _REQUEST_ENTERCONFIGURATIONMODE._serialized_end=2602
+  _REQUEST_EXITCONFIGURATIONMODE._serialized_start=2604
+  _REQUEST_EXITCONFIGURATIONMODE._serialized_end=2627
+  _REQUEST_RELOADREFTREE._serialized_start=2629
+  _REQUEST_RELOADREFTREE._serialized_end=2664
+  _REQUEST_CONFIGFORMAT._serialized_start=2666
+  _REQUEST_CONFIGFORMAT._serialized_end=2701
+  _REQUEST_OUTPUTFORMAT._serialized_start=2703
+  _REQUEST_OUTPUTFORMAT._serialized_end=2744
+  _REQUESTENVELOPE._serialized_start=2753
+  _REQUESTENVELOPE._serialized_end=2812
+  _RESPONSE._serialized_start=2814
+  _RESPONSE._serialized_end=2897
 # @@protoc_insertion_point(module_scope)
diff --git a/python/vyos/proto/vyconf_proto.py b/python/vyos/proto/vyconf_proto.py
index 404ef2f27..ec62a6e35 100644
--- a/python/vyos/proto/vyconf_proto.py
+++ b/python/vyos/proto/vyconf_proto.py
@@ -100,11 +100,13 @@ class Rollback:
 @dataclass
 class Load:
     Location: str = ""
+    cached: bool = False
     format: ConfigFormat = None
 
 @dataclass
 class Merge:
     Location: str = ""
+    destructive: bool = False
     format: ConfigFormat = None
 
 @dataclass
@@ -298,14 +300,14 @@ def set_request_rollback(token: str = None, revision: int = 0):
     req_env = RequestEnvelope(token, req)
     return req_env
 
-def set_request_load(token: str = None, location: str = "", format: ConfigFormat = None):
-    reqi = Load (location, format)
+def set_request_load(token: str = None, location: str = "", cached: bool = False, format: ConfigFormat = None):
+    reqi = Load (location, cached, format)
     req = Request(load=reqi)
     req_env = RequestEnvelope(token, req)
     return req_env
 
-def set_request_merge(token: str = None, location: str = "", format: ConfigFormat = None):
-    reqi = Merge (location, format)
+def set_request_merge(token: str = None, location: str = "", destructive: bool = False, format: ConfigFormat = None):
+    reqi = Merge (location, destructive, format)
     req = Request(merge=reqi)
     req_env = RequestEnvelope(token, req)
     return req_env
diff --git a/python/vyos/remote.py b/python/vyos/remote.py
index f6ab5c3f9..b73f486c0 100644
--- a/python/vyos/remote.py
+++ b/python/vyos/remote.py
@@ -22,6 +22,7 @@ import stat
 import sys
 import tempfile
 import urllib.parse
+import gzip
 
 from contextlib import contextmanager
 from pathlib import Path
@@ -44,6 +45,7 @@ from vyos.utils.misc import begin
 from vyos.utils.process import cmd, rc_cmd
 from vyos.version import get_version
 from vyos.base import Warning
+from vyos.defaults import directories
 
 CHUNK_SIZE = 8192
 
@@ -478,3 +480,45 @@ def get_remote_config(urlstring, source_host='', source_port=0):
             return f.read()
     finally:
         os.remove(temp)
+
+
+def get_config_file(file_in: str, file_out: str, source_host='', source_port=0):
+    protocols = ['scp', 'sftp', 'http', 'https', 'ftp', 'tftp']
+    config_dir = directories['config']
+
+    with tempfile.NamedTemporaryFile() as tmp_file:
+        if any(file_in.startswith(f'{x}://') for x in protocols):
+            try:
+                download(
+                    tmp_file.name,
+                    file_in,
+                    check_space=True,
+                    source_host='',
+                    source_port=0,
+                    raise_error=True,
+                )
+            except Exception as e:
+                return e
+            file_name = tmp_file.name
+        else:
+            full_path = os.path.realpath(file_in)
+            if os.path.isfile(full_path):
+                file_in = full_path
+            else:
+                file_in = os.path.join(config_dir, file_in)
+                if not os.path.isfile(file_in):
+                    return ValueError(f'No such file {file_in}')
+
+            file_name = file_in
+
+        if file_in.endswith('.gz'):
+            try:
+                with gzip.open(file_name, 'rb') as f_in:
+                    with open(file_out, 'wb') as f_out:
+                        shutil.copyfileobj(f_in, f_out)
+            except Exception as e:
+                return e
+        else:
+            shutil.copyfile(file_name, file_out)
+
+    return None
diff --git a/python/vyos/vyconf_session.py b/python/vyos/vyconf_session.py
index 4a2e6e393..3cf5fb4e3 100644
--- a/python/vyos/vyconf_session.py
+++ b/python/vyos/vyconf_session.py
@@ -17,7 +17,6 @@
 
 import os
 import tempfile
-import shutil
 from functools import wraps
 from typing import Type
 
@@ -30,6 +29,7 @@ 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
 from vyos.utils.commit import call_commit_hooks
+from vyos.remote import get_config_file
 
 
 class VyconfSessionError(Exception):
@@ -142,6 +142,10 @@ class VyconfSession:
     @raise_exception
     @config_mode
     def commit(self) -> tuple[str, int]:
+        if not self.session_changed():
+            out = 'No changes to commit'
+            return out, 0
+
         lock_fd, out = acquire_commit_lock_file()
         if lock_fd is None:
             return out, Errnum.COMMIT_IN_PROGRESS
@@ -163,24 +167,57 @@ class VyconfSession:
 
     @raise_exception
     @config_mode
-    def load_config(self, file: str, migrate: bool = False) -> tuple[str, int]:
+    def load_config(
+        self, file_name: str, migrate: bool = False, cached: bool = False
+    ) -> tuple[str, int]:
         # pylint: disable=consider-using-with
+        file_path = tempfile.NamedTemporaryFile(delete=False).name
+        err = get_config_file(file_name, file_path)
+        if err:
+            os.remove(file_path)
+            return str(err), Errnum.INVALID_VALUE
+        if not cached:
+            if migrate:
+                config_migrate = ConfigMigrate(file_path)
+                try:
+                    config_migrate.run()
+                except ConfigMigrateError as e:
+                    os.remove(file_path)
+                    return repr(e), 1
+
+        out = vyconf_client.send_request(
+            'load', token=self.__token, location=file_path, cached=cached
+        )
+
+        if not cached:
+            os.remove(file_path)
+
+        return self.output(out), out.status
+
+    @raise_exception
+    @config_mode
+    def merge_config(
+        self, file_name: str, migrate: bool = False, destructive: bool = False
+    ) -> tuple[str, int]:
+        # pylint: disable=consider-using-with
+        file_path = tempfile.NamedTemporaryFile(delete=False).name
+        err = get_config_file(file_name, file_path)
+        if err:
+            os.remove(file_path)
+            return str(err), Errnum.INVALID_VALUE
         if migrate:
-            tmp = tempfile.NamedTemporaryFile()
-            shutil.copy2(file, tmp.name)
-            config_migrate = ConfigMigrate(tmp.name)
+            config_migrate = ConfigMigrate(file_path)
             try:
                 config_migrate.run()
             except ConfigMigrateError as e:
-                tmp.close()
+                os.remove(file_path)
                 return repr(e), 1
-            file = tmp.name
-        else:
-            tmp = ''
 
-        out = vyconf_client.send_request('load', token=self.__token, location=file)
-        if tmp:
-            tmp.close()
+        out = vyconf_client.send_request(
+            'merge', token=self.__token, location=file_path, destructive=destructive
+        )
+
+        os.remove(file_path)
 
         return self.output(out), out.status
 
diff --git a/src/helpers/vyos-load-config.py b/src/helpers/vyos-load-config.py
index cd6bff0d4..01a6a88dc 100755
--- a/src/helpers/vyos-load-config.py
+++ b/src/helpers/vyos-load-config.py
@@ -16,84 +16,57 @@
 #
 #
 
-"""Load config file from within config session.
-Config file specified by URI or path (without scheme prefix).
-Example: load https://somewhere.net/some.config
-        or
-         load /tmp/some.config
-"""
-
 import os
 import sys
-import gzip
+import argparse
 import tempfile
-import vyos.defaults
-import vyos.remote
-from vyos.configsource import ConfigSourceSession, VyOSError
+
+from vyos.remote import get_config_file
+from vyos.config import Config
 from vyos.migrate import ConfigMigrate
 from vyos.migrate import ConfigMigrateError
+from vyos.load_config import load as load_config
 
-class LoadConfig(ConfigSourceSession):
-    """A subclass for calling 'loadFile'.
-    This does not belong in configsource.py, and only has a single caller.
-    """
-    def load_config(self, path):
-        return self._run(['/bin/cli-shell-api','loadFile',path])
-
-file_name = sys.argv[1] if len(sys.argv) > 1 else 'config.boot'
-configdir = vyos.defaults.directories['config']
-protocols = ['scp', 'sftp', 'http', 'https', 'ftp', 'tftp']
 
-def get_local_config(filename):
-    if os.path.isfile(filename):
-        fname = filename
-    elif os.path.isfile(os.path.join(configdir, filename)):
-        fname = os.path.join(configdir, filename)
-    else:
-        sys.exit(f"No such file '{filename}'")
+parser = argparse.ArgumentParser()
+parser.add_argument('config_file', help='config file to load')
+parser.add_argument(
+    '--migrate', action='store_true', help='migrate config file before merge'
+)
 
-    if fname.endswith('.gz'):
-        with gzip.open(fname, 'rb') as f:
-            try:
-                config_str = f.read().decode()
-            except OSError as e:
-                sys.exit(e)
-    else:
-        with open(fname, 'r') as f:
-            try:
-                config_str = f.read()
-            except OSError as e:
-                sys.exit(e)
+args = parser.parse_args()
 
-    return config_str
-
-if any(file_name.startswith(f'{x}://') for x in protocols):
-    config_string = vyos.remote.get_remote_config(file_name)
-    if not config_string:
-        sys.exit(f"No such config file at '{file_name}'")
-else:
-    config_string = get_local_config(file_name)
+file_name = args.config_file
 
-config = LoadConfig()
+# pylint: disable=consider-using-with
+file_path = tempfile.NamedTemporaryFile(delete=False).name
+err = get_config_file(file_name, file_path)
+if err:
+    os.remove(file_path)
+    sys.exit(err)
 
-print(f"Loading configuration from '{file_name}'")
+if args.migrate:
+    migrate = ConfigMigrate(file_path)
+    try:
+        migrate.run()
+    except ConfigMigrateError as e:
+        os.remove(file_path)
+        sys.exit(e)
 
-with tempfile.NamedTemporaryFile() as fp:
-    with open(fp.name, 'w') as fd:
-        fd.write(config_string)
+config = Config()
 
-    config_migrate = ConfigMigrate(fp.name)
-    try:
-        config_migrate.run()
-    except ConfigMigrateError as err:
-        sys.exit(err)
+if config.vyconf_session is not None:
+    out, err = config.vyconf_session.load_config(file_path)
+    if err:
+        os.remove(file_path)
+        sys.exit(out)
+    print(out)
+else:
+    load_config(file_path)
 
-    try:
-        config.load_config(fp.name)
-    except VyOSError as err:
-        sys.exit(err)
+os.remove(file_path)
 
 if config.session_changed():
     print("Load complete. Use 'commit' to make changes effective.")
 else:
-    print("No configuration changes to commit.")
+    print('No configuration changes to commit.')
diff --git a/src/helpers/vyos-merge-config.py b/src/helpers/vyos-merge-config.py
index 79b17a261..e8a696eb5 100755
--- a/src/helpers/vyos-merge-config.py
+++ b/src/helpers/vyos-merge-config.py
@@ -2,107 +2,100 @@
 
 # Copyright VyOS maintainers and contributors <maintainers@vyos.io>
 #
-# This library is free software; you can redistribute it and/or
-# modify it under the terms of the GNU Lesser General Public
-# License as published by the Free Software Foundation; either
-# version 2.1 of the License, or (at your option) any later version.
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
 #
-# This library is distributed in the hope that it will be useful,
+# This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-# Lesser General Public License for more details.
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
 #
-# You should have received a copy of the GNU Lesser General Public
-# License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 
+import os
 import sys
+import shlex
+import argparse
 import tempfile
-import vyos.defaults
-import vyos.remote
 
+from vyos.remote import get_config_file
 from vyos.config import Config
 from vyos.configtree import ConfigTree
+from vyos.configtree import mask_inclusive
+from vyos.configtree import merge
 from vyos.migrate import ConfigMigrate
 from vyos.migrate import ConfigMigrateError
-from vyos.utils.process import cmd
-from vyos.utils.process import DEVNULL
+from vyos.load_config import load_explicit
 
-if (len(sys.argv) < 2):
-    print("Need config file name to merge.")
-    print("Usage: merge <config file> [config path]")
-    sys.exit(0)
 
-file_name = sys.argv[1]
+parser = argparse.ArgumentParser()
+parser.add_argument('config_file', help='config file to merge from')
+parser.add_argument(
+    '--destructive', action='store_true', help='replace values with those of merge file'
+)
+parser.add_argument('--paths', nargs='+', help='only merge from listed paths')
+parser.add_argument(
+    '--migrate', action='store_true', help='migrate config file before merge'
+)
 
-configdir = vyos.defaults.directories['config']
+args = parser.parse_args()
 
-protocols = ['scp', 'sftp', 'http', 'https', 'ftp', 'tftp']
+file_name = args.config_file
+paths = [shlex.split(s) for s in args.paths] if args.paths else []
 
-if any(x in file_name for x in protocols):
-    config_file = vyos.remote.get_remote_config(file_name)
-    if not config_file:
-        sys.exit("No config file by that name.")
-else:
-    canonical_path = "{0}/{1}".format(configdir, file_name)
-    first_err = None
-    try:
-        with open(canonical_path, 'r') as f:
-            config_file = f.read()
-    except Exception as err:
-        first_err = err
-        try:
-            with open(file_name, 'r') as f:
-                config_file = f.read()
-        except Exception as err:
-            print(first_err)
-            print(err)
-            sys.exit(1)
-
-with tempfile.NamedTemporaryFile() as file_to_migrate:
-    with open(file_to_migrate.name, 'w') as fd:
-        fd.write(config_file)
-
-    config_migrate = ConfigMigrate(file_to_migrate.name)
+# pylint: disable=consider-using-with
+file_path = tempfile.NamedTemporaryFile(delete=False).name
+err = get_config_file(file_name, file_path)
+if err:
+    os.remove(file_path)
+    sys.exit(err)
+
+if args.migrate:
+    migrate = ConfigMigrate(file_path)
     try:
-        config_migrate.run()
+        migrate.run()
     except ConfigMigrateError as e:
+        os.remove(file_path)
         sys.exit(e)
 
-merge_config_tree = ConfigTree(config_file)
+with open(file_path) as f:
+    merge_str = f.read()
+
+merge_ct = ConfigTree(merge_str)
 
-effective_config = Config()
-effective_config_tree = effective_config._running_config
+if paths:
+    mask = ConfigTree('')
+    for p in paths:
+        mask.set(p)
 
-effective_cmds = effective_config_tree.to_commands()
-merge_cmds = merge_config_tree.to_commands()
+    merge_ct = mask_inclusive(merge_ct, mask)
 
-effective_cmd_list = effective_cmds.splitlines()
-merge_cmd_list =  merge_cmds.splitlines()
+with open(file_path, 'w') as f:
+    f.write(merge_ct.to_string())
 
-effective_cmd_set = set(effective_cmd_list)
-add_cmds = [ cmd for cmd in merge_cmd_list if cmd not in effective_cmd_set ]
+config = Config()
 
-path = None
-if (len(sys.argv) > 2):
-    path = sys.argv[2:]
-    if (not effective_config_tree.exists(path) and not
-            merge_config_tree.exists(path)):
-        print("path {} does not exist in either effective or merge"
-              " config; will use root.".format(path))
-        path = None
-    else:
-        path = " ".join(path)
+if config.vyconf_session is not None:
+    out, err = config.vyconf_session.merge_config(
+        file_path, destructive=args.destructive
+    )
+    if err:
+        os.remove(file_path)
+        sys.exit(out)
+    print(out)
+else:
+    session_ct = config.get_config_tree()
+    merge_res = merge(session_ct, merge_ct, destructive=args.destructive)
 
-if path:
-    add_cmds = [ cmd for cmd in add_cmds if path in cmd ]
+    load_explicit(merge_res)
 
-for add in add_cmds:
-    try:
-        cmd(f'/opt/vyatta/sbin/my_{add}', shell=True, stderr=DEVNULL)
-    except OSError as err:
-        print(err)
+os.remove(file_path)
 
-if effective_config.session_changed():
+if config.session_changed():
     print("Merge complete. Use 'commit' to make changes effective.")
 else:
-    print("No configuration changes to commit.")
+    print('No configuration changes to commit.')
diff --git a/src/services/api/rest/models.py b/src/services/api/rest/models.py
index 7a61ddfd1..70fab03ec 100644
--- a/src/services/api/rest/models.py
+++ b/src/services/api/rest/models.py
@@ -143,6 +143,7 @@ class ConfigFileModel(ApiModel):
     file: StrictStr = None
     string: StrictStr = None
     confirm_time: StrictInt = 0
+    destructive: bool = False
 
     class Config:
         json_schema_extra = {
diff --git a/src/services/api/rest/routers.py b/src/services/api/rest/routers.py
index 48eca8f15..329d6e51f 100644
--- a/src/services/api/rest/routers.py
+++ b/src/services/api/rest/routers.py
@@ -597,7 +597,7 @@ async def config_file_op(data: ConfigFileModel, background_tasks: BackgroundTask
                 case 'load':
                     session.migrate_and_load_config(path)
                 case 'merge':
-                    session.merge_config(path)
+                    session.merge_config(path, destructive=data.destructive)
 
             config = Config(session_env=env)
             d = get_config_diff(config)
diff --git a/src/tests/test_config_merge.py b/src/tests/test_config_merge.py
new file mode 100644
index 000000000..c9b4ad5c8
--- /dev/null
+++ b/src/tests/test_config_merge.py
@@ -0,0 +1,50 @@
+# Copyright VyOS maintainers and contributors <maintainers@vyos.io>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 2 or later as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import vyos.configtree
+
+from unittest import TestCase
+
+class TestConfigDiff(TestCase):
+    def setUp(self):
+        with open('tests/data/config.left', 'r') as f:
+            config_string = f.read()
+            self.config_left = vyos.configtree.ConfigTree(config_string)
+
+        with open('tests/data/config.right', 'r') as f:
+            config_string = f.read()
+            self.config_right = vyos.configtree.ConfigTree(config_string)
+
+    def test_merge_destructive(self):
+        res = vyos.configtree.merge(self.config_left, self.config_right,
+                                    destructive=True)
+        right_value = self.config_right.return_value(['node1', 'tag_node', 'foo', 'single'])
+        merge_value = res.return_value(['node1', 'tag_node', 'foo', 'single'])
+
+        # Check includes new value
+        self.assertEqual(right_value, merge_value)
+
+        # Check preserves non-confliciting paths
+        self.assertTrue(res.exists(['node3']))
+
+    def test_merge_non_destructive(self):
+        res = vyos.configtree.merge(self.config_left, self.config_right)
+        left_value = self.config_left.return_value(['node1', 'tag_node', 'foo', 'single'])
+        merge_value = res.return_value(['node1', 'tag_node', 'foo', 'single'])
+
+        # Check includes original value
+        self.assertEqual(left_value, merge_value)
+
+        # Check preserves non-confliciting paths
+        self.assertTrue(res.exists(['node3']))