lib, zebra: move "struct vrf" to be a lib module

Previously "struct vrf" is defined locally in zebra. Now it is moved
to be a lib module.

This is the first step to support multi-VRF in quagga. The
implementation is splitted into small patches for the purpose of
easy review.

* lib:
    "struct vrf" with basic members is defined in vrf.c. The member
    "void *info" is for user data.

    Some basic functions are defined in vrf.c for adding/deleting/
    looking up a VRF, scanning the VRF table and initializing the
    VRF module.

    The type "vrf_id_t" is defined specificly for VRF ID.

* zebra:
    The previous "struct vrf" is re-defined as "struct zebra_vrf";
    and previous "vrf" variables are renamed to "zvrf".

    The previous "struct vrf" related functions are removed from
    zbera_rib.c. New functions are defined to maintain the new
    "struct zebra_vrf".

    The names vrf_xxx are reserved for the functions in VRF module.
    So:
    - the previous vrf_table() are renamed to zebra_vrf_table();
    - the previous vrf_static_table() are renamed to
      zebra_vrf_static_table().

    The main logic is not changed.

    BTW: Add a statement to zebra_snmp.c telling that the SNMP is
         running only for the MIBs in the default VRF.

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: Vincent JARDIN <vincent.jardin@6wind.com>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/zebra/rib.h b/zebra/rib.h
index 94a7419..802d875 100644
--- a/zebra/rib.h
+++ b/zebra/rib.h
@@ -315,10 +315,10 @@
                        : (((recursing) = 0),((tnexthop) = (tnexthop)->next)))
 
 /* Routing table instance.  */
-struct vrf
+struct zebra_vrf
 {
-  /* Identifier.  This is same as routing table vector index.  */
-  u_int32_t id;
+  /* Identifier. */
+  vrf_id_t vrf_id;
 
   /* Routing table name.  */
   char *name;
@@ -346,9 +346,9 @@
 {
 
   /*
-   * Back pointer to vrf.
+   * Back pointer to zebra_vrf.
    */
-  struct vrf *vrf;
+  struct zebra_vrf *zvrf;
   afi_t afi;
   safi_t safi;
 
@@ -367,7 +367,7 @@
  */
 typedef struct rib_tables_iter_t_
 {
-  uint32_t vrf_id;
+  vrf_id_t vrf_id;
   int afi_safi_ix;
 
   rib_tables_iter_state_t state;
@@ -415,9 +415,9 @@
 extern struct nexthop *nexthop_ipv6_add (struct rib *, struct in6_addr *);
 #endif /* HAVE_IPV6 */
 
-extern struct vrf *vrf_lookup (u_int32_t);
-extern struct route_table *vrf_table (afi_t afi, safi_t safi, u_int32_t id);
-extern struct route_table *vrf_static_table (afi_t afi, safi_t safi, u_int32_t id);
+extern struct zebra_vrf *zebra_vrf_alloc (vrf_id_t);
+extern struct route_table *zebra_vrf_table (afi_t, safi_t, vrf_id_t);
+extern struct route_table *zebra_vrf_static_table (afi_t, safi_t, vrf_id_t);
 
 /* NOTE:
  * All rib_add_ipv[46]* functions will not just add prefix into RIB, but
@@ -557,10 +557,10 @@
 /*
  * rib_dest_vrf
  */
-static inline struct vrf *
+static inline struct zebra_vrf *
 rib_dest_vrf (rib_dest_t *dest)
 {
-  return rib_table_info (rib_dest_table (dest))->vrf;
+  return rib_table_info (rib_dest_table (dest))->zvrf;
 }
 
 /*