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/zebra_snmp.c b/zebra/zebra_snmp.c
index f0d3e7e..3d005aa 100644
--- a/zebra/zebra_snmp.c
+++ b/zebra/zebra_snmp.c
@@ -19,6 +19,10 @@
  * 02111-1307, USA.  
  */
 
+/*
+ * Currently SNMP is only running properly for MIBs in the default VRF.
+ */
+
 #include <zebra.h>
 
 #ifdef HAVE_SNMP
@@ -31,6 +35,7 @@
 #include "command.h"
 #include "smux.h"
 #include "table.h"
+#include "vrf.h"
 
 #include "zebra/rib.h"
 #include "zebra/zserv.h"
@@ -143,7 +148,7 @@
   if (smux_header_generic(v, objid, objid_len, exact, val_len, write_method) == MATCH_FAILED)
     return NULL;
 
-  table = vrf_table (AFI_IP, SAFI_UNICAST, 0);
+  table = zebra_vrf_table (AFI_IP, SAFI_UNICAST, VRF_DEFAULT);
   if (! table)
     return NULL;
 
@@ -168,7 +173,7 @@
   if (smux_header_generic(v, objid, objid_len, exact, val_len, write_method) == MATCH_FAILED)
     return NULL;
 
-  table = vrf_table (AFI_IP, SAFI_UNICAST, 0);
+  table = zebra_vrf_table (AFI_IP, SAFI_UNICAST, VRF_DEFAULT);
   if (! table)
     return 0;
 
@@ -330,7 +335,7 @@
   if (exact && (*objid_len != (unsigned) v->namelen + 10))
     return;
 
-  table = vrf_table (AFI_IP, SAFI_UNICAST, 0);
+  table = zebra_vrf_table (AFI_IP, SAFI_UNICAST, VRF_DEFAULT);
   if (! table)
     return;