addons: vrf: redo iproute2 vrf interface map handling

Ticket: CM-10188, CM-10061
Reviewed By: dsa, nikhil, julien
Testing Done: Tested static routes with vrf names for tables

This patch does the following:
- if a single vrf device is present in the config,
builds the vrf map by reading vrf interfaces from the kernel (with
existing link cache. Builds a shadow vrf only attribute cache)
- reads existing table map and adjusts it if required
- main change is the iproute2 map file on disk is updated
immediately on vrf creation, so that static routes used along with the
vrf slaves can use the vrf name for the table. This also helps dhclient dns
hook script which may use mgmt table name directly.
- cleans up default routes on down

Signed-off-by: Roopa Prabhu <roopa@cumulusnetworks.com>

ifupdownaddons/iproute2.py

@@ -24,10 +24,16 @@ class iproute2(utilsBase):
 
     def __init__(self, *args, **kargs):
         utilsBase.__init__(self, *args, **kargs)
-        if self.CACHE and not iproute2._cache_fill_done:
+        if self.CACHE:
+            self._fill_cache()
+
+    def _fill_cache(self):
+        if not iproute2._cache_fill_done:
             self._link_fill()
             self._addr_fill()
             iproute2._cache_fill_done = True
+            return True
+        return False
         
     def _link_fill(self, ifacename=None, refresh=False):
         """ fills cache with link information
@@ -99,6 +105,7 @@ class iproute2(utilsBase):
                     vattrs = {'table' : citems[i+2]}
                     linkattrs['linkinfo'] = vattrs
                     linkattrs['kind'] = 'vrf'
+                    linkCache.vrfs[ifname] = vattrs
                     break
                 elif citems[i] == 'vrf_slave':
                     linkattrs['kind'] = 'vrf_slave'
@@ -173,10 +180,8 @@ class iproute2(utilsBase):
             if self.DRYRUN:
                 return False
             if self.CACHE:
-                if not iproute2._cache_fill_done: 
-                    self._link_fill()
-                    self._addr_fill()
-                    iproute2._cache_fill_done = True
+                if self._fill_cache():
+                    # if we filled the cache, return new data
                     return linkCache.get_attr(attrlist)
                 if not refresh:
                     return linkCache.get_attr(attrlist)
@@ -847,3 +852,7 @@ class iproute2(utilsBase):
             return os.path.basename(upper[0])[6:]
         except:
             return None
+
+    def link_get_vrfs(self):
+        self._fill_cache()
+        return linkCache.vrfs