Run neutron-vpn-netns-wrapper in venv

When neutron is installed inside venv, neutron-vpn-netns-wrapper
is placed inside venv as well. Currently vpn creation will fail due to
missing wrapper inside $PATH. So we should respect venvs and launch
neutron-vpn-netns-wrapper from the venv when applicable.

Closes-Bug: 1848201
Change-Id: I9c50bfc2cefdd97c6d54e8bfabe97748c8dfce13

neutron_vpnaas/services/vpn/device_drivers/ipsec.py

@@ -20,6 +20,7 @@ import os
 import re
 import shutil
 import socket
+import sys
 
 import eventlet
 import jinja2
@@ -175,6 +176,8 @@ class BaseSwanProcess(object, metaclass=abc.ABCMeta):
         "v1": "never"
     }
 
+    NS_WRAPPER = 'neutron-vpn-netns-wrapper'
+
     STATUS_DICT = {
         'erouted': constants.ACTIVE,
         'unrouted': constants.DOWN
@@ -234,6 +237,18 @@ class BaseSwanProcess(object, metaclass=abc.ABCMeta):
             psk = encodeutils.safe_decode(encoded_psk, incoming='utf_8')
             ipsec_site_conn['psk'] = PSK_BASE64_PREFIX + psk
 
+    def get_ns_wrapper(self):
+        """
+        Check if we're inside a virtualenv. If we are, then we should
+        respect this and launch wrapper from venv as well.
+        """
+        if (hasattr(sys, 'real_prefix') or
+            (hasattr(sys, 'base_prefix') and sys.base_prefix != sys.prefix)):
+            ns_wrapper = os.path.join(sys.prefix, "bin/", self.NS_WRAPPER)
+        else:
+            ns_wrapper = self.NS_WRAPPER
+        return ns_wrapper
+
     def update_vpnservice(self, vpnservice):
         self.vpnservice = vpnservice
         self.translate_dialect()

neutron_vpnaas/services/vpn/device_drivers/libreswan_ipsec.py

@@ -19,8 +19,6 @@ from neutron.agent.linux import ip_lib
 
 from neutron_vpnaas.services.vpn.device_drivers import ipsec
 
-NS_WRAPPER = 'neutron-vpn-netns-wrapper'
-
 
 class LibreSwanProcess(ipsec.OpenSwanProcess):
     """Libreswan Process manager class.
@@ -45,8 +43,9 @@ class LibreSwanProcess(ipsec.OpenSwanProcess):
         mount_paths_str = ','.join(
             "%s:%s" % (source, target)
             for source, target in mount_paths.items())
+        ns_wrapper = self.get_ns_wrapper()
         return ip_wrapper.netns.execute(
-            [NS_WRAPPER,
+            [ns_wrapper,
              '--mount_paths=%s' % mount_paths_str,
              ('--rootwrap_config=%s' % self._rootwrap_cfg
                  if self._rootwrap_cfg else ''),

neutron_vpnaas/services/vpn/device_drivers/strongswan_ipsec.py

@@ -57,8 +57,6 @@ strongswan_opts = [
 ]
 cfg.CONF.register_opts(strongswan_opts, 'strongswan')
 
-NS_WRAPPER = 'neutron-vpn-netns-wrapper'
-
 
 class StrongSwanProcess(ipsec.BaseSwanProcess):
 
@@ -112,8 +110,9 @@ class StrongSwanProcess(ipsec.BaseSwanProcess):
         The namespace wrapper will bind /etc/ and /var/run
         """
         ip_wrapper = ip_lib.IPWrapper(namespace=self.namespace)
+        ns_wrapper = self.get_ns_wrapper()
         return ip_wrapper.netns.execute(
-            [NS_WRAPPER,
+            [ns_wrapper,
              '--mount_paths=/etc:%s/etc,%s:%s/var/run' % (
                  self.config_dir, self._strongswan_piddir, self.config_dir),
              ('--rootwrap_config=%s' % self._rootwrap_cfg