zebra, lib/memtypes.c: the netlink sockets work per VRF

This patch lets the netlink sockets work per VRF.

* The definition of "struct nlsock" is moved into zebra/rib.h.

* The previous global variables "netlink" and "netlink_cmd" now
  become the members of "struct zebra_vrf", and are initialized
  in zebra_vrf_alloc().

* All relative functions now work for a specific VRF, by adding
  a new parameter which specifies the working VRF, except those
  functions in which the VRF ID can be obtained from the interface.

* kernel_init(), interface_list() and route_read() are now also
  working per VRF, and moved from main() to zebra_vrf_enable().

* A new function kernel_terminate() is added to release the
  netlink sockets. It is called from zebra_vrf_disable().

* Correct VRF ID, instead of the previous VRF_DEFAULT, are now
  passed to the functions of processing interfaces or route
  entries.

Signed-off-by: Feng Lu <lu.feng@6wind.com>
Reviewed-by: Alain Ritoux <alain.ritoux@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Acked-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/zebra/rib.h b/zebra/rib.h
index 9972941..8328f23 100644
--- a/zebra/rib.h
+++ b/zebra/rib.h
@@ -355,6 +355,17 @@
 };
 #endif /* RTADV && HAVE_IPV6 */
 
+#ifdef HAVE_NETLINK
+/* Socket interface to kernel */
+struct nlsock
+{
+  int sock;
+  int seq;
+  struct sockaddr_nl snl;
+  const char *name;
+};
+#endif
+
 /* Routing table instance.  */
 struct zebra_vrf
 {
@@ -376,6 +387,12 @@
   /* Static route configuration.  */
   struct route_table *stable[AFI_MAX][SAFI_MAX];
 
+#ifdef HAVE_NETLINK
+  struct nlsock netlink;     /* kernel messages */
+  struct nlsock netlink_cmd; /* command channel */
+  struct thread *t_netlink;
+#endif
+
   /* 2nd pointer type used primarily to quell a warning on
    * ALL_LIST_ELEMENTS_RO
    */