Check for ovs-vsctl presence when using OVS with clab (fixes #1799) (#…

…1811)

netsim/cli/external_commands.py

@@ -42,6 +42,12 @@ def add_netlab_path() -> None:
 
   return
 
+"""
+has_command: figures out whether a command is available
+"""
+def has_command(cmd: str) -> bool:
+  return bool(run_command(['bash','-c',f'command -v {cmd}'],check_result=True,ignore_errors=True))
+
 """
 run_command: Execute an external command specified as a string or a list of CLI parameters
 

netsim/cli/install.py

@@ -95,12 +95,6 @@ def check_crazy_pip3(args: argparse.Namespace) -> None:
     os.environ['FLAG_PIP']  = os.environ['FLAG_PIP'] + ' --user'
     os.environ['FLAG_USER'] = 'Y'
 
-"""
-has_command: figures out whether a command is available
-"""
-def has_command(cmd: str) -> typing.Union[bool,int,str]:
-  return external_commands.run_command(['bash','-c',f'command -v {cmd}'],check_result=True,ignore_errors=True)
-
 """
 set_sudo_flag: figures out whether we have 'sudo' installed and whether the user
 is a root user if there's no sudo.
@@ -113,7 +107,7 @@ def set_sudo_flag() -> None:
   if os.getuid() == 0:
     return
 
-  if has_command('sudo'):
+  if external_commands.has_command('sudo'):
     os.environ['SUDO'] = "sudo DEBIAN_FRONTEND=noninteractive NEEDRESTART_MODE=a"
     return
 
@@ -138,7 +132,7 @@ def check_script(path: str, args: argparse.Namespace) -> None:
   cmds = script.read_text()
 
   if ' apt-get ' in cmds:
-    if not has_command('apt-get'):
+    if not external_commands.has_command('apt-get'):
       log.error(
         'This script uses apt-get command that is not available on your system',
         more_hints='Most netlab installation scripts work on Ubuntu (and probably on Debian)',
@@ -148,7 +142,7 @@ def check_script(path: str, args: argparse.Namespace) -> None:
   if ' pip3 ' not in cmds:
     return
 
-  if not has_command('pip3'):
+  if not external_commands.has_command('pip3'):
     log.error(
       'This script uses pip3 command that is not available on your system',
       more_hints="Install pip3 (for example, with 'sudo apt-get install python-pip3')",

netsim/providers/clab.py

@@ -19,7 +19,7 @@ def list_bridges( topology: Box ) -> typing.Set[str]:
   return { l.bridge for l in topology.links if l.bridge and l.node_count > 2 and not 'external_bridge' in l.clab }
 
 def use_ovs_bridge( topology: Box ) -> bool:
-    return topology.defaults.providers.clab.bridge_type == "ovs-bridge"
+  return topology.defaults.providers.clab.bridge_type == "ovs-bridge"
 
 def create_linux_bridge( brname: str ) -> bool:
   if external_commands.run_command(
@@ -50,7 +50,26 @@ def destroy_linux_bridge( brname: str ) -> bool:
   log.print_verbose( f"Delete Linux bridge '{brname}': {status}" )
   return True
 
+_OVS_OK: bool = False
+def check_ovs_installation() -> None:
+  global _OVS_OK
+  if _OVS_OK:
+    return
+
+  if not external_commands.has_command('ovs-vsctl'):
+    log.error(
+      'Open vSwitch package is not installed, you cannot use OVS bridges with containerlab',
+      more_hints = [
+        'This error was caused by defaults.providers.clab.bridge_type being set to ovs-bridge',
+        'Use "sudo apt install openvswitch-switch" on Ubuntu or an equivalent command to install Open vSwitch'],
+      category=log.FatalError,
+      module='clab')
+    log.exit_on_error()
+
+  _OVS_OK = True
+
 def create_ovs_bridge( brname: str ) -> bool:
+  check_ovs_installation()
   status = external_commands.run_command(
       ['sudo','ovs-vsctl','add-br',brname],check_result=True,return_stdout=True)
   if status is False:
@@ -168,6 +187,9 @@ def node_post_transform(self, node: Box, topology: Box) -> None:
     self.create_extra_files_mappings(node,topology)
 
   def post_configuration_create(self, topology: Box) -> None:
+    if use_ovs_bridge(topology):
+      check_ovs_installation()
+
     for n in topology.nodes.values():
       if n.get('clab.binds',None):
         self.create_extra_files(n,topology)