bgpd, doc, lib, zebra: nexthop-tracking in zebra

0. Introduction

This is the design specification for next hop tracking feature in
Quagga.

1. Background

Recursive routes are of the form:

   p/m --> n
  [Ex: 1.1.0.0/16 --> 2.2.2.2]

where 'n' itself is resolved through another route as follows:

   p2/m --> h, interface
  [Ex: 2.2.2.0/24 --> 3.3.3.3, eth0]

Usually, BGP routes are recursive in nature and BGP nexthops get
resolved through an IGP route. IGP usually adds its routes pointing to
an interface (these are called non-recursive routes).

When BGP receives a recursive route from a peer, it needs to validate
the nexthop. The path is marked valid or invalid based on the
reachability status of the nexthop.  Nexthop validation is also
important for BGP decision process as the metric to reach the nexthop
is a parameter to best path selection process.

As it goes with routing, this is a dynamic process. Route to the
nexthop can change. The nexthop can become unreachable or
reachable. In the current BGP implementation, the nexthop validation
is done periodically in the scanner run. The default scanner run
interval is one minute. Every minute, the scanner task walks the
entire BGP table. It checks the validity of each nexthop with Zebra
(the routing table manager) through a request and response message
exchange between BGP and Zebra process. BGP process is blocked for
that duration. The mechanism has two major drawbacks:

(1) The scanner task runs to completion. That can potentially starve
    the other tasks for long periods of time, based on the BGP table
    size and number of nexthops.

(2) Convergence around routing changes that affect the nexthops can be
    long (around a minute with the default intervals). The interval
    can be shortened to achieve faster reaction time, but it makes the
    first problem worse, with the scanner task consuming most of the
    CPU resources.

"Next hop tracking" feature makes this process event-driven. It
eliminates periodic nexthop validation and introduces an asynchronous
communication path between BGP and Zebra for route change notifications
that can then be acted upon.

2. Goal

Stating the obvious, the main goal is to remove the two limitations we
discussed in the previous section. The goals, in a constructive tone,
are the following:

- fairness: the scanner run should not consume an unjustly high amount
  of CPU time. This should give an overall good performance and
  response time to other events (route changes, session events,
  IO/user interface).

- convergence: BGP must react to nexthop changes instantly and provide
  sub-second convergence. This may involve diverting the routes from
  one nexthop to another.

3. Overview of the changes

The changes are in both BGP and Zebra modules.  The short summary is
the following:

- Zebra implements a registration mechanism by which clients can
   register for next hop notification. Consequently, it maintains a
   separate table, per (VRF, AF) pair, of next hops and interested
   client-list per next hop.

- When the main routing table changes in Zebra, it evaluates the next
   hop table: for each next hop, it checks if the route table
   modifications have changed its state. If so, it notifies the
   interested clients.

- BGP is one such client. It registers the next hops corresponding to
   all of its received routes/paths. It also threads the paths against
   each nexthop structure.

- When BGP receives a next hop notification from Zebra, it walks the
   corresponding path list. It makes them valid or invalid depending
   on the next hop notification. It then re-computes best path for the
   corresponding destination. This may result in re-announcing those
   destinations to peers.

4. Design

4.1. Modules

The core design introduces an "nht" (next hop tracking) module in BGP
and "rnh" (recursive nexthop) module in Zebra. The "nht" module
provides the following APIs:

bgp_find_or_add_nexthop() : find or add a nexthop in BGP nexthop table
bgp_find_nexthop() : find a nexthop in BGP nexthop table
bgp_parse_nexthop_update() : parse a nexthop update message coming
                              from zebra

The "rnh" module provides the following APIs:

zebra_add_rnh() : add a recursive nexthop
zebra_delete_rnh() : delete a recursive nexthop
zebra_lookup_rnh() : lookup a recursive nexthop

zebra_add_rnh_client() : register a client for nexthop notifications
                         against a recursive nexthop

zebra_remove_rnh_client(): remove the client registration for a
                            recursive nexthop

zebra_evaluate_rnh_table(): (re)evaluate the recursive nexthop table
                            (most probably because the main routing
                            table has changed).

zebra_cleanup_rnh_client(): Cleanup a client from the "rnh" module
                            data structures (most probably because the
                            client is going away).

4.2. Control flow

The next hop registration control flow is the following:

<====      BGP Process       ====>|<====      Zebra Process      ====>
                                  |
receive module     nht module     |  zserv module        rnh module
----------------------------------------------------------------------
              |                   |                  |
bgp_update_   |                   |                  |
      main()  | bgp_find_or_add_  |                  |
              |        nexthop()  |                  |
              |                   |                  |
              |                   | zserv_nexthop_   |
              |                   |       register() |
              |                   |                  | zebra_add_rnh()
              |                   |                  |

The next hop notification control flow is the following:

<====     Zebra Process    ====>|<====      BGP Process       ====>
                                |
rib module         rnh module   |     zebra module        nht module
----------------------------------------------------------------------
              |                 |                   |
meta_queue_   |                 |                   |
    process() | zebra_evaluate_ |                   |
              |     rnh_table() |                   |
              |                 |                   |
              |                 | bgp_read_nexthop_ |
              |                 |          update() |
              |                 |                   | bgp_parse_
              |                 |                   | nexthop_update()
              |                 |                   |

4.3. zclient message format

ZEBRA_NEXTHOP_REGISTER and ZEBRA_NEXTHOP_UNREGISTER messages are
encoded in the following way:

/*
 *     0                   1                   2                   3
 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |     AF                        |  prefix len   |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * .      Nexthop prefix                                           .
 * .                                                               .
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * .                                                               .
 * .                                                               .
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |     AF                        |  prefix len   |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * .      Nexthop prefix                                           .
 * .                                                               .
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 */

ZEBRA_NEXTHOP_UPDATE message is encoded as follows:

/*
 *     0                   1                   2                   3
 *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |     AF                        |  prefix len   |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * .      Nexthop prefix getting resolved                          .
 * .                                                               .
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |        metric                                                 |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * |  #nexthops    |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * | nexthop type  |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * .      resolving Nexthop details                                .
 * .                                                               .
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * .                                                               .
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * | nexthop type  |
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 * .      resolving Nexthop details                                .
 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 */

4.4. BGP data structure

Legend:

/\   struct bgp_node: a BGP destination/route/prefix
\/

[ ]  struct bgp_info: a BGP path (e.g. route received from a peer)

 _
(_)  struct bgp_nexthop_cache: a BGP nexthop

   /\         NULL
   \/--+        ^
       |        :
       +--[ ]--[ ]--[ ]--> NULL
   /\           :
   \/--+        :
       |        :
       +--[ ]--[ ]--> NULL
                :
  _             :
 (_).............

4.5. Zebra data structure

rnh table:

           O
          / \
         O   O
            / \
           O   O

        struct rnh
        {
          u_char flags;
          struct rib *state;
          struct list *client_list;
          struct route_node *node;
        };

5. User interface changes

quagga# show ip nht
3.3.3.3
 resolved via kernel
 via 11.0.0.6, swp1
 Client list: bgp(fd 12)
11.0.0.10
 resolved via connected
 is directly connected, swp2
 Client list: bgp(fd 12)
11.0.0.18
 resolved via connected
 is directly connected, swp4
 Client list: bgp(fd 12)
11.11.11.11
 resolved via kernel
 via 10.0.1.2, eth0
 Client list: bgp(fd 12)

quagga# show ip bgp nexthop
Current BGP nexthop cache:
 3.3.3.3 valid [IGP metric 0], #paths 3
  Last update: Wed Oct 16 04:43:49 2013

 11.0.0.10 valid [IGP metric 1], #paths 1
  Last update: Wed Oct 16 04:43:51 2013

 11.0.0.18 valid [IGP metric 1], #paths 2
  Last update: Wed Oct 16 04:43:47 2013

 11.11.11.11 valid [IGP metric 0], #paths 1
  Last update: Wed Oct 16 04:43:47 2013

quagga# show ipv6 nht
quagga# show ip bgp nexthop detail

quagga# debug bgp nht
quagga# debug zebra nht

6. Sample test cases

     r2----r3
    /  \  /
  r1----r4

- Verify that a change in IGP cost triggers NHT
  + shutdown the r1-r4 and r2-r4 links
  + no shut the r1-r4 and r2-r4 links and wait for OSPF to come back
    up
  + We should be back to the original nexthop via r4 now
- Verify that a NH becoming unreachable triggers NHT
  + Shutdown all links to r4
- Verify that a NH becoming reachable triggers NHT
  + no shut all links to r4

7. Future work

- route-policy for next hop validation (e.g. ignore default route)
- damping for rapid next hop changes
- prioritized handling of nexthop changes ((un)reachability vs. metric
  changes)
- handling recursion loop, e.g.
   11.11.11.11/32 -> 12.12.12.12
   12.12.12.12/32 -> 11.11.11.11
   11.0.0.0/8 -> <interface>
- better statistics
Addresses upstream comments.

"show ip bgp nexthop detail" couldn't display multiple NHs due to a bug.
Fix that.

Fix reference counts for the nexthop cache entries

Signed-off-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
Signed-off-by: Daniel Walton <dwalton@cumulusnetworks.com>
Signed-off-by: Dinesh Dutt <ddutt@cumulusnetworks.com>
Signed-off-by: Donald Sharp <sharpd@cumulusnetworks.com>
Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>

Fix reference counts for the nexthop cache entries.

Signed-off-by: Vivek Venkatraman <vivek@cumulusnetworks.com>

Edited-by: Paul Jakma <paul.jakma@hpe.com>
- Fix nexthop_ipv6_add defs in rib.h not having been modified with rib_ prefix.
- Remove rib_lookup_and_pushup, appears not to be used except for
  !HAVE_NETLINK && HAVE_STRUCT_IFALIASREQ case of ioctl.c::if_set_prefix,
  so it's not being used at all on platform with most testing of RIB.

bgpd/Makefile.am

@@ -16,7 +16,7 @@ libbgp_a_SOURCES = \
 	bgp_packet.c bgp_network.c bgp_filter.c bgp_regex.c bgp_clist.c \
 	bgp_dump.c bgp_snmp.c bgp_ecommunity.c bgp_mplsvpn.c bgp_nexthop.c \
 	bgp_damp.c bgp_table.c bgp_advertise.c bgp_vty.c bgp_mpath.c \
-	bgp_encap.c bgp_encap_tlv.c
+	bgp_encap.c bgp_encap_tlv.c bgp_nht.c
 
 noinst_HEADERS = \
 	bgp_aspath.h bgp_attr.h bgp_community.h bgp_debug.h bgp_fsm.h \
@@ -24,7 +24,7 @@ noinst_HEADERS = \
 	bgpd.h bgp_filter.h bgp_clist.h bgp_dump.h bgp_zebra.h \
 	bgp_ecommunity.h bgp_mplsvpn.h bgp_nexthop.h bgp_damp.h bgp_table.h \
 	bgp_advertise.h bgp_snmp.h bgp_vty.h bgp_mpath.h \
-	bgp_encap.h bgp_encap_tlv.h bgp_encap_types.h
+	bgp_encap.h bgp_encap_tlv.h bgp_encap_types.h bgp_nht.h
 
 bgpd_SOURCES = bgp_main.c
 bgpd_LDADD = libbgp.a ../lib/libzebra.la @LIBCAP@ @LIBM@

bgpd/bgp_debug.c

@@ -47,6 +47,7 @@ unsigned long conf_bgp_debug_update;
 unsigned long conf_bgp_debug_normal;
 unsigned long conf_bgp_debug_zebra;
 unsigned long conf_bgp_debug_allow_martians;
+unsigned long conf_bgp_debug_nht;
 
 unsigned long term_bgp_debug_as4;
 unsigned long term_bgp_debug_fsm;
@@ -58,6 +59,7 @@ unsigned long term_bgp_debug_update;
 unsigned long term_bgp_debug_normal;
 unsigned long term_bgp_debug_zebra;
 unsigned long term_bgp_debug_allow_martians;
+unsigned long term_bgp_debug_nht;
 
 /* messages for BGP-4 status */
 const struct message bgp_status_msg[] = 
@@ -472,6 +474,48 @@ ALIAS (no_debug_bgp_events,
        BGP_STR
        "BGP events\n")
 
+DEFUN (debug_bgp_nht,
+       debug_bgp_nht_cmd,
+       "debug bgp nht",
+       DEBUG_STR
+       BGP_STR
+       "BGP nexthop tracking events\n")
+{
+  if (vty->node == CONFIG_NODE)
+    DEBUG_ON (nht, NHT);
+  else
+    {
+      TERM_DEBUG_ON (nht, NHT);
+      vty_out (vty, "BGP nexthop tracking debugging is on%s", VTY_NEWLINE);
+    }
+  return CMD_SUCCESS;
+}
+
+DEFUN (no_debug_bgp_nht,
+       no_debug_bgp_nht_cmd,
+       "no debug bgp nht",
+       NO_STR
+       DEBUG_STR
+       BGP_STR
+       "BGP nexthop tracking events\n")
+{
+  if (vty->node == CONFIG_NODE)
+    DEBUG_OFF (nht, NHT);
+  else
+    {
+      TERM_DEBUG_OFF (nht, NHT);
+      vty_out (vty, "BGP nexthop tracking debugging is off%s", VTY_NEWLINE);
+    }
+  return CMD_SUCCESS;
+}
+
+ALIAS (no_debug_bgp_nht,
+       undebug_bgp_nht_cmd,
+       "undebug bgp nht",
+       UNDEBUG_STR
+       BGP_STR
+       "BGP next-hop tracking updates\n")
+
 DEFUN (debug_bgp_filter,
        debug_bgp_filter_cmd,
        "debug bgp filters",
@@ -833,6 +877,8 @@ DEFUN (show_debugging_bgp,
     vty_out (vty, "  BGP as4 aspath segment debugging is on%s", VTY_NEWLINE);
   if (BGP_DEBUG (allow_martians, ALLOW_MARTIANS))
     vty_out (vty, "  BGP allow martian next hop debugging is on%s", VTY_NEWLINE);
+  if (BGP_DEBUG (nht, NHT))
+    vty_out (vty, "  BGP next-hop tracking debugging is on%s", VTY_NEWLINE);
   vty_out (vty, "%s", VTY_NEWLINE);
   return CMD_SUCCESS;
 }
@@ -911,6 +957,12 @@ bgp_config_write_debug (struct vty *vty)
       vty_out (vty, "debug bgp allow-martians%s", VTY_NEWLINE);
       write++;
     }
+  
+  if (CONF_BGP_DEBUG (nht, NHT))
+    {
+      vty_out (vty, "debug bgp nht%s", VTY_NEWLINE);
+      write++;
+    }
 
   return write;
 }
@@ -938,6 +990,8 @@ bgp_debug_init (void)
   install_element (CONFIG_NODE, &debug_bgp_fsm_cmd);
   install_element (ENABLE_NODE, &debug_bgp_events_cmd);
   install_element (CONFIG_NODE, &debug_bgp_events_cmd);
+  install_element (ENABLE_NODE, &debug_bgp_nht_cmd);
+  install_element (CONFIG_NODE, &debug_bgp_nht_cmd);
   install_element (ENABLE_NODE, &debug_bgp_filter_cmd);
   install_element (CONFIG_NODE, &debug_bgp_filter_cmd);
   install_element (ENABLE_NODE, &debug_bgp_keepalive_cmd);
@@ -966,6 +1020,9 @@ bgp_debug_init (void)
   install_element (ENABLE_NODE, &no_debug_bgp_events_cmd);
   install_element (ENABLE_NODE, &undebug_bgp_events_cmd);
   install_element (CONFIG_NODE, &no_debug_bgp_events_cmd);
+  install_element (ENABLE_NODE, &no_debug_bgp_nht_cmd);
+  install_element (ENABLE_NODE, &undebug_bgp_nht_cmd);
+  install_element (CONFIG_NODE, &no_debug_bgp_nht_cmd);
   install_element (ENABLE_NODE, &no_debug_bgp_filter_cmd);
   install_element (ENABLE_NODE, &undebug_bgp_filter_cmd);
   install_element (CONFIG_NODE, &no_debug_bgp_filter_cmd);

bgpd/bgp_debug.h

@@ -68,6 +68,7 @@ extern unsigned long conf_bgp_debug_update;
 extern unsigned long conf_bgp_debug_normal;
 extern unsigned long conf_bgp_debug_zebra;
 extern unsigned long conf_bgp_debug_allow_martians;
+extern unsigned long conf_bgp_debug_nht;
 
 extern unsigned long term_bgp_debug_as4;
 extern unsigned long term_bgp_debug_fsm;
@@ -79,6 +80,7 @@ extern unsigned long term_bgp_debug_update;
 extern unsigned long term_bgp_debug_normal;
 extern unsigned long term_bgp_debug_zebra;
 extern unsigned long term_bgp_debug_allow_martians;
+extern unsigned long term_bgp_debug_nht;
 
 #define BGP_DEBUG_AS4                 0x01
 #define BGP_DEBUG_AS4_SEGMENT         0x02
@@ -93,6 +95,7 @@ extern unsigned long term_bgp_debug_allow_martians;
 #define BGP_DEBUG_NORMAL              0x01
 #define BGP_DEBUG_ZEBRA               0x01
 #define BGP_DEBUG_ALLOW_MARTIANS      0x01
+#define BGP_DEBUG_NHT                 0x01
 
 #define BGP_DEBUG_PACKET_SEND         0x01
 #define BGP_DEBUG_PACKET_SEND_DETAIL  0x02

bgpd/bgp_nexthop.c

@@ -31,17 +31,21 @@ Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 #include "hash.h"
 #include "jhash.h"
 #include "filter.h"
+#include "nexthop.h"
 
 #include "bgpd/bgpd.h"
 #include "bgpd/bgp_table.h"
 #include "bgpd/bgp_route.h"
 #include "bgpd/bgp_attr.h"
 #include "bgpd/bgp_nexthop.h"
+#include "bgpd/bgp_nht.h"
 #include "bgpd/bgp_debug.h"
 #include "bgpd/bgp_damp.h"
 #include "zebra/rib.h"
 #include "zebra/zserv.h"	/* For ZEBRA_SERV_PATH. */
 
+extern struct zclient *zclient;
+
 struct bgp_nexthop_cache *zlookup_query (struct in_addr);
 struct bgp_nexthop_cache *zlookup_query_ipv6 (struct in6_addr *);
 
@@ -58,7 +62,7 @@ static int bgp_scan_interval;
 static int bgp_import_interval;
 
 /* Route table for next-hop lookup cache. */
-static struct bgp_table *bgp_nexthop_cache_table[AFI_MAX];
+struct bgp_table *bgp_nexthop_cache_table[AFI_MAX];
 static struct bgp_table *cache1_table[AFI_MAX];
 static struct bgp_table *cache2_table[AFI_MAX];
 
@@ -68,6 +72,13 @@ static struct bgp_table *bgp_connected_table[AFI_MAX];
 /* BGP nexthop lookup query client. */
 struct zclient *zlookup = NULL;
 
+char *
+bnc_str (struct bgp_nexthop_cache *bnc, char *buf, int size)
+{
+  prefix2str(&(bnc->node->p), buf, size);
+  return buf;
+}
+
 /* Add nexthop to the end of the list.  */
 static void
 bnc_nexthop_add (struct bgp_nexthop_cache *bnc, struct nexthop *nexthop)
@@ -83,7 +94,7 @@ bnc_nexthop_add (struct bgp_nexthop_cache *bnc, struct nexthop *nexthop)
   nexthop->prev = last;
 }
 
-static void
+void
 bnc_nexthop_free (struct bgp_nexthop_cache *bnc)
 {
   struct nexthop *nexthop;
@@ -96,59 +107,23 @@ bnc_nexthop_free (struct bgp_nexthop_cache *bnc)
     }
 }
 
-static struct bgp_nexthop_cache *
+struct bgp_nexthop_cache *
 bnc_new (void)
 {
-  return XCALLOC (MTYPE_BGP_NEXTHOP_CACHE, sizeof (struct bgp_nexthop_cache));
+  struct bgp_nexthop_cache *bnc;
+
+  bnc = XCALLOC (MTYPE_BGP_NEXTHOP_CACHE, sizeof (struct bgp_nexthop_cache));
+  LIST_INIT(&(bnc->paths));
+  return bnc;
 }
 
-static void
+void
 bnc_free (struct bgp_nexthop_cache *bnc)
 {
   bnc_nexthop_free (bnc);
   XFREE (MTYPE_BGP_NEXTHOP_CACHE, bnc);
 }
 
-static int
-bgp_nexthop_same (struct nexthop *next1, struct nexthop *next2)
-{
-  if (next1->type != next2->type)
-    return 0;
-
-  switch (next1->type)
-    {
-    case ZEBRA_NEXTHOP_IPV4:
-      if (! IPV4_ADDR_SAME (&next1->gate.ipv4, &next2->gate.ipv4))
-	return 0;
-      break;
-    case ZEBRA_NEXTHOP_IPV4_IFINDEX:
-      if (! IPV4_ADDR_SAME (&next1->gate.ipv4, &next2->gate.ipv4)
-	  || next1->ifindex != next2->ifindex)
-	return 0;
-      break;
-    case ZEBRA_NEXTHOP_IFINDEX:
-    case ZEBRA_NEXTHOP_IFNAME:
-      if (next1->ifindex != next2->ifindex)
-	return 0;
-      break;
-    case ZEBRA_NEXTHOP_IPV6:
-      if (! IPV6_ADDR_SAME (&next1->gate.ipv6, &next2->gate.ipv6))
-	return 0;
-      break;
-    case ZEBRA_NEXTHOP_IPV6_IFINDEX:
-    case ZEBRA_NEXTHOP_IPV6_IFNAME:
-      if (! IPV6_ADDR_SAME (&next1->gate.ipv6, &next2->gate.ipv6))
-	return 0;
-      if (next1->ifindex != next2->ifindex)
-	return 0;
-      break;
-    default:
-      /* do nothing */
-      break;
-    }
-  return 1;
-}
-
 static int
 bgp_nexthop_cache_different (struct bgp_nexthop_cache *bnc1,
 			   struct bgp_nexthop_cache *bnc2)
@@ -164,7 +139,7 @@ bgp_nexthop_cache_different (struct bgp_nexthop_cache *bnc1,
 
   for (i = 0; i < bnc1->nexthop_num; i++)
     {
-      if (! bgp_nexthop_same (next1, next2))
+      if (! nexthop_same_no_recurse (next1, next2))
 	return 1;
 
       next1 = next1->next;
@@ -382,6 +357,7 @@ bgp_nexthop_lookup (afi_t afi, struct peer *peer, struct bgp_info *ri,
   return bnc->valid;
 }
 
+#if BGP_SCAN_NEXTHOP
 /* Reset and free all BGP nexthop cache. */
 static void
 bgp_nexthop_cache_reset (struct bgp_table *table)
@@ -397,6 +373,7 @@ bgp_nexthop_cache_reset (struct bgp_table *table)
 	bgp_unlock_node (rn);
       }
 }
+#endif
 
 static void
 bgp_scan (afi_t afi, safi_t safi)
@@ -407,6 +384,7 @@ bgp_scan (afi_t afi, safi_t safi)
   struct bgp_info *next;
   struct peer *peer;
   struct listnode *node, *nnode;
+#if BGP_SCAN_NEXTHOP
   int valid;
   int current;
   int changed;
@@ -417,6 +395,7 @@ bgp_scan (afi_t afi, safi_t safi)
     bgp_nexthop_cache_table[afi] = cache2_table[afi];
   else
     bgp_nexthop_cache_table[afi] = cache1_table[afi];
+#endif
 
   /* Get default bgp. */
   bgp = bgp_get_default ();
@@ -446,6 +425,7 @@ bgp_scan (afi_t afi, safi_t safi)
 
 	  if (bi->type == ZEBRA_ROUTE_BGP && bi->sub_type == BGP_ROUTE_NORMAL)
 	    {
+#if BGP_SCAN_NEXTHOP
 	      changed = 0;
 	      metricchanged = 0;
 
@@ -478,6 +458,7 @@ bgp_scan (afi_t afi, safi_t safi)
 					       afi, SAFI_UNICAST);
 		    }
 		}
+#endif
 
               if (CHECK_FLAG (bgp->af_flags[afi][SAFI_UNICAST],
 		  BGP_CONFIG_DAMPENING)
@@ -491,11 +472,13 @@ bgp_scan (afi_t afi, safi_t safi)
         bgp_process (bgp, rn, afi, SAFI_UNICAST);
     }
 
+#if BGP_SCAN_NEXTHOP
   /* Flash old cache. */
   if (bgp_nexthop_cache_table[afi] == cache1_table[afi])
     bgp_nexthop_cache_reset (cache2_table[afi]);
   else
     bgp_nexthop_cache_reset (cache1_table[afi]);
+#endif
 
   if (BGP_DEBUG (events, EVENTS))
     {
@@ -1262,9 +1245,7 @@ static int
 show_ip_bgp_scan_tables (struct vty *vty, const char detail)
 {
   struct bgp_node *rn;
-  struct bgp_nexthop_cache *bnc;
   char buf[INET6_ADDRSTRLEN];
-  u_char i;
 
   if (bgp_scan_thread)
     vty_out (vty, "BGP scan is running%s", VTY_NEWLINE);
@@ -1272,6 +1253,7 @@ show_ip_bgp_scan_tables (struct vty *vty, const char detail)
     vty_out (vty, "BGP scan is not running%s", VTY_NEWLINE);
   vty_out (vty, "BGP scan interval is %d%s", bgp_scan_interval, VTY_NEWLINE);
 
+#if BGP_SCAN_NEXTHOP
   vty_out (vty, "Current BGP nexthop cache:%s", VTY_NEWLINE);
   for (rn = bgp_table_top (bgp_nexthop_cache_table[AFI_IP]); rn; rn = bgp_route_next (rn))
     if ((bnc = rn->info) != NULL)
@@ -1281,21 +1263,21 @@ show_ip_bgp_scan_tables (struct vty *vty, const char detail)
 	  vty_out (vty, " %s valid [IGP metric %d]%s",
 		   inet_ntop (AF_INET, &rn->p.u.prefix4, buf, INET6_ADDRSTRLEN), bnc->metric, VTY_NEWLINE);
 	  if (detail)
-	    for (i = 0; i < bnc->nexthop_num; i++)
-	      switch (bnc->nexthop[i].type)
+	    for (nexthop = bnc->nexthop; nexthop; nexthop = nexthop->next)
+	      switch (nexthop->type)
 	      {
 	      case NEXTHOP_TYPE_IPV4:
-		vty_out (vty, "  gate %s%s", inet_ntop (AF_INET, &bnc->nexthop[i].gate.ipv4, buf, INET6_ADDRSTRLEN), VTY_NEWLINE);
+		vty_out (vty, "  gate %s%s", inet_ntop (AF_INET, &nexthop->gate.ipv4, buf, INET6_ADDRSTRLEN), VTY_NEWLINE);
 		break;
 	      case NEXTHOP_TYPE_IPV4_IFINDEX:
-		vty_out (vty, "  gate %s", inet_ntop (AF_INET, &bnc->nexthop[i].gate.ipv4, buf, INET6_ADDRSTRLEN));
-		vty_out (vty, " ifidx %u%s", bnc->nexthop[i].ifindex, VTY_NEWLINE);
+		vty_out (vty, "  gate %s", inet_ntop (AF_INET, &nexthop->gate.ipv4, buf, INET6_ADDRSTRLEN));
+		vty_out (vty, " ifidx %u%s", nexthop->ifindex, VTY_NEWLINE);
 		break;
 	      case NEXTHOP_TYPE_IFINDEX:
-		vty_out (vty, "  ifidx %u%s", bnc->nexthop[i].ifindex, VTY_NEWLINE);
+		vty_out (vty, "  ifidx %u%s", nexthop->ifindex, VTY_NEWLINE);
 		break;
 	      default:
-		vty_out (vty, "  invalid nexthop type %u%s", bnc->nexthop[i].type, VTY_NEWLINE);
+		vty_out (vty, "  invalid nexthop type %u%s", nexthop->type, VTY_NEWLINE);
 	      }
 	}
 	else
@@ -1315,17 +1297,17 @@ show_ip_bgp_scan_tables (struct vty *vty, const char detail)
 		     inet_ntop (AF_INET6, &rn->p.u.prefix6, buf, INET6_ADDRSTRLEN),
 		     bnc->metric, VTY_NEWLINE);
 	    if (detail)
-	      for (i = 0; i < bnc->nexthop_num; i++)
-		switch (bnc->nexthop[i].type)
+	      for (nexthop = bnc->nexthop; nexthop; nexthop = nexthop->next)
+		switch (nexthop->type)
 		{
 		case NEXTHOP_TYPE_IPV6:
-		  vty_out (vty, "  gate %s%s", inet_ntop (AF_INET6, &bnc->nexthop[i].gate.ipv6, buf, INET6_ADDRSTRLEN), VTY_NEWLINE);
+		  vty_out (vty, "  gate %s%s", inet_ntop (AF_INET6, &nexthop->gate.ipv6, buf, INET6_ADDRSTRLEN), VTY_NEWLINE);
 		  break;
 		case NEXTHOP_TYPE_IFINDEX:
-		  vty_out (vty, "  ifidx %u%s", bnc->nexthop[i].ifindex, VTY_NEWLINE);
+		  vty_out (vty, "  ifidx %u%s", nexthop->ifindex, VTY_NEWLINE);
 		  break;
 		default:
-		  vty_out (vty, "  invalid nexthop type %u%s", bnc->nexthop[i].type, VTY_NEWLINE);
+		  vty_out (vty, "  invalid nexthop type %u%s", nexthop->type, VTY_NEWLINE);
 		}
 	  }
 	  else
@@ -1334,7 +1316,9 @@ show_ip_bgp_scan_tables (struct vty *vty, const char detail)
 		     VTY_NEWLINE);
 	}
   }
-
+#else
+  vty_out (vty, "BGP next-hop tracking is on%s", VTY_NEWLINE);
+#endif
   vty_out (vty, "BGP connected route:%s", VTY_NEWLINE);
   for (rn = bgp_table_top (bgp_connected_table[AFI_IP]); 
        rn; 
@@ -1357,6 +1341,80 @@ show_ip_bgp_scan_tables (struct vty *vty, const char detail)
   return CMD_SUCCESS;
 }
 
+static int
+show_ip_bgp_nexthop_table (struct vty *vty, int detail)
+{
+  struct bgp_node *rn;
+  struct bgp_nexthop_cache *bnc;
+  char buf[INET6_ADDRSTRLEN];
+  struct nexthop *nexthop;
+  time_t tbuf;
+  afi_t afi;
+
+  vty_out (vty, "Current BGP nexthop cache:%s", VTY_NEWLINE);
+  for (afi = AFI_IP ; afi < AFI_MAX ; afi++)
+    {
+      for (rn = bgp_table_top (bgp_nexthop_cache_table[afi]); rn; rn = bgp_route_next (rn))
+	{
+	  if ((bnc = rn->info) != NULL)
+	    {
+	      if (CHECK_FLAG(bnc->flags, BGP_NEXTHOP_VALID))
+		{
+		  vty_out (vty, " %s valid [IGP metric %d], #paths %d%s",
+			   inet_ntop (rn->p.family, &rn->p.u.prefix, buf, sizeof (buf)),
+			   bnc->metric, bnc->path_count, VTY_NEWLINE);
+		  if (detail)
+		    for (nexthop = bnc->nexthop ; nexthop; nexthop = nexthop->next)
+		      switch (nexthop->type)
+			{
+			case NEXTHOP_TYPE_IPV6:
+			  vty_out (vty, "  gate %s%s",
+				   inet_ntop (AF_INET6, &nexthop->gate.ipv6,
+					      buf, INET6_ADDRSTRLEN), VTY_NEWLINE);
+			  break;
+			case NEXTHOP_TYPE_IPV6_IFINDEX:
+			  vty_out(vty, "  gate %s, if %s%s",
+				  inet_ntop(AF_INET6, &nexthop->gate.ipv6, buf,
+					    INET6_ADDRSTRLEN),
+				  ifindex2ifname(nexthop->ifindex),
+				  VTY_NEWLINE);
+			  break;
+			case NEXTHOP_TYPE_IPV4:
+			  vty_out (vty, "  gate %s%s",
+				   inet_ntop (AF_INET, &nexthop->gate.ipv4, buf,
+					      INET6_ADDRSTRLEN), VTY_NEWLINE);
+			  break;
+			case NEXTHOP_TYPE_IFINDEX:
+			  vty_out (vty, "  if %s%s",
+				   ifindex2ifname(nexthop->ifindex), VTY_NEWLINE);
+			  break;
+			case NEXTHOP_TYPE_IPV4_IFINDEX:
+			  vty_out (vty, "  gate %s, if %s%s",
+				   inet_ntop(AF_INET, &nexthop->gate.ipv4, buf,
+					     INET6_ADDRSTRLEN),
+				   ifindex2ifname(nexthop->ifindex), VTY_NEWLINE);
+			  break;
+			default:
+			  vty_out (vty, "  invalid nexthop type %u%s",
+				   nexthop->type, VTY_NEWLINE);
+			}
+		}
+	      else
+		vty_out (vty, " %s invalid%s",
+			 inet_ntop (AF_INET, &rn->p.u.prefix, buf, sizeof (buf)), VTY_NEWLINE);
+#ifdef HAVE_CLOCK_MONOTONIC
+	      tbuf = time(NULL) - (bgp_clock() - bnc->last_update);
+	      vty_out (vty, "  Last update: %s", ctime(&tbuf));
+#else
+	      vty_out (vty, "  Last update: %s", ctime(&bnc->uptime));
+#endif /* HAVE_CLOCK_MONOTONIC */
+	      vty_out(vty, "%s", VTY_NEWLINE);
+	    }
+	}
+    }
+  return CMD_SUCCESS;
+}
+
 DEFUN (show_ip_bgp_scan,
        show_ip_bgp_scan_cmd,
        "show ip bgp scan",
@@ -1380,6 +1438,28 @@ DEFUN (show_ip_bgp_scan_detail,
   return show_ip_bgp_scan_tables (vty, 1);
 }
 
+DEFUN (show_ip_bgp_nexthop,
+       show_ip_bgp_nexthop_cmd,
+       "show ip bgp nexthop",
+       SHOW_STR
+       IP_STR
+       BGP_STR
+       "BGP nexthop table\n")
+{
+  return show_ip_bgp_nexthop_table (vty, 0);
+}
+
+DEFUN (show_ip_bgp_nexthop_detail,
+       show_ip_bgp_nexthop_detail_cmd,
+       "show ip bgp nexthop detail",
+       SHOW_STR
+       IP_STR
+       BGP_STR
+       "BGP nexthop table\n")
+{
+  return show_ip_bgp_nexthop_table (vty, 1);
+}
+
 int
 bgp_config_write_scan_time (struct vty *vty)
 {
@@ -1420,8 +1500,12 @@ bgp_scan_init (void)
   install_element (BGP_NODE, &no_bgp_scan_time_val_cmd);
   install_element (VIEW_NODE, &show_ip_bgp_scan_cmd);
   install_element (VIEW_NODE, &show_ip_bgp_scan_detail_cmd);
+  install_element (VIEW_NODE, &show_ip_bgp_nexthop_cmd);
+  install_element (VIEW_NODE, &show_ip_bgp_nexthop_detail_cmd);
   install_element (RESTRICTED_NODE, &show_ip_bgp_scan_cmd);
   install_element (ENABLE_NODE, &show_ip_bgp_scan_cmd);
+  install_element (ENABLE_NODE, &show_ip_bgp_nexthop_cmd);
+  install_element (ENABLE_NODE, &show_ip_bgp_nexthop_detail_cmd);
   install_element (ENABLE_NODE, &show_ip_bgp_scan_detail_cmd);
 }
 

bgpd/bgp_nexthop.h

@@ -22,6 +22,8 @@ Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 #define _QUAGGA_BGP_NEXTHOP_H
 
 #include "if.h"
+#include "queue.h"
+#include "prefix.h"
 
 #define BGP_SCAN_INTERVAL_DEFAULT   60
 #define BGP_IMPORT_INTERVAL_DEFAULT 15
@@ -53,6 +55,20 @@ struct bgp_nexthop_cache
   /* Nexthop number and nexthop linked list.*/
   u_char nexthop_num;
   struct nexthop *nexthop;
+  time_t last_update;
+  u_int16_t flags;
+
+#define BGP_NEXTHOP_VALID (1 << 0)
+#define BGP_NEXTHOP_REGISTERED (1 << 1)
+
+  u_int16_t change_flags;
+
+#define BGP_NEXTHOP_CHANGED (1 << 0)
+#define BGP_NEXTHOP_METRIC_CHANGED (1 << 1)
+
+  struct bgp_node *node;
+  LIST_HEAD(path_list, bgp_info) paths;
+  unsigned int path_count;
 };
 
 extern void bgp_scan_init (void);
@@ -68,5 +84,9 @@ extern int bgp_nexthop_self (struct attr *);
 extern void bgp_address_init (void);
 extern void bgp_address_destroy (void);
 extern void bgp_scan_destroy (void);
+extern struct bgp_nexthop_cache *bnc_new(void);
+extern void bnc_free(struct bgp_nexthop_cache *bnc);
+extern void bnc_nexthop_free(struct bgp_nexthop_cache *bnc);
+extern char *bnc_str(struct bgp_nexthop_cache *bnc, char *buf, int size);
 
 #endif /* _QUAGGA_BGP_NEXTHOP_H */

bgpd/bgp_nht.c

@@ -0,0 +1,477 @@
+/* BGP Nexthop tracking
+ * Copyright (C) 2013 Cumulus Networks, Inc.
+ *
+ * This file is part of GNU Zebra.
+ *
+ * GNU Zebra is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * GNU Zebra is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Zebra; see the file COPYING.  If not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include <zebra.h>
+
+#include "command.h"
+#include "thread.h"
+#include "prefix.h"
+#include "zclient.h"
+#include "stream.h"
+#include "network.h"
+#include "log.h"
+#include "memory.h"
+#include "nexthop.h"
+#include "filter.h"
+
+#include "bgpd/bgpd.h"
+#include "bgpd/bgp_table.h"
+#include "bgpd/bgp_route.h"
+#include "bgpd/bgp_attr.h"
+#include "bgpd/bgp_nexthop.h"
+#include "bgpd/bgp_debug.h"
+#include "bgpd/bgp_nht.h"
+
+extern struct zclient *zclient;
+extern struct bgp_table *bgp_nexthop_cache_table[AFI_MAX];
+
+static void register_nexthop(struct bgp_nexthop_cache *bnc);
+static void unregister_nexthop (struct bgp_nexthop_cache *bnc);
+static void evaluate_paths(struct bgp_nexthop_cache *bnc);
+static int make_prefix(int afi, struct bgp_info *ri, struct prefix *p);
+static void path_nh_map(struct bgp_info *path, struct bgp_nexthop_cache *bnc,
+			int keep);
+
+int
+bgp_find_nexthop (struct bgp_info *path, int *changed, int *metricchanged)
+{
+  struct bgp_nexthop_cache *bnc = path->nexthop;
+
+  if (!bnc)
+    return 0;
+
+  if (changed)
+    *changed = CHECK_FLAG(bnc->change_flags, BGP_NEXTHOP_CHANGED);
+
+  if (metricchanged)
+    *metricchanged = CHECK_FLAG(bnc->change_flags,
+				BGP_NEXTHOP_METRIC_CHANGED);
+
+  return (CHECK_FLAG(bnc->flags, BGP_NEXTHOP_VALID));
+}
+
+void
+bgp_unlink_nexthop (struct bgp_info *path)
+{
+  struct bgp_nexthop_cache *bnc = path->nexthop;
+
+  if (!bnc)
+    return;
+
+  path_nh_map(path, NULL, 0);
+
+  if (LIST_EMPTY(&(bnc->paths)))
+    {
+      if (BGP_DEBUG(nht, NHT))
+	{
+	  char buf[INET6_ADDRSTRLEN];
+	  zlog_debug("bgp_unlink_nexthop: freeing bnc %s",
+		     bnc_str(bnc, buf, INET6_ADDRSTRLEN));
+	}
+      unregister_nexthop(bnc);
+      bnc->node->info = NULL;
+      bgp_unlock_node(bnc->node);
+      bnc_free(bnc);
+    }
+}
+
+int
+bgp_find_or_add_nexthop (afi_t afi, struct bgp_info *ri, int *changed,
+			 int *metricchanged)
+{
+  struct bgp_node *rn;
+  struct bgp_nexthop_cache *bnc;
+  struct prefix p;
+
+  if (make_prefix(afi, ri, &p) < 0)
+    return 1;
+  rn = bgp_node_get (bgp_nexthop_cache_table[afi], &p);
+
+  if (!rn->info)
+    {
+      bnc = bnc_new();
+      rn->info = bnc;
+      bnc->node = rn;
+      bgp_lock_node(rn);
+      register_nexthop(bnc);
+    }
+  bnc = rn->info;
+  bgp_unlock_node (rn);
+  path_nh_map(ri, bnc, 1);
+
+  if (changed)
+    *changed = CHECK_FLAG(bnc->change_flags, BGP_NEXTHOP_CHANGED);
+
+  if (metricchanged)
+    *metricchanged = CHECK_FLAG(bnc->change_flags,
+				BGP_NEXTHOP_METRIC_CHANGED);
+
+  if (CHECK_FLAG(bnc->flags, BGP_NEXTHOP_VALID) && bnc->metric)
+    (bgp_info_extra_get(ri))->igpmetric = bnc->metric;
+  else if (ri->extra)
+    ri->extra->igpmetric = 0;
+
+  return (CHECK_FLAG(bnc->flags, BGP_NEXTHOP_VALID));
+}
+
+void
+bgp_parse_nexthop_update (void)
+{
+  struct stream *s;
+  struct bgp_node *rn;
+  struct bgp_nexthop_cache *bnc;
+  struct nexthop *nexthop;
+  struct nexthop *oldnh;
+  struct nexthop *nhlist_head = NULL;
+  struct nexthop *nhlist_tail = NULL;
+  uint32_t metric;
+  u_char nexthop_num;
+  struct prefix p;
+  int i;
+
+  s = zclient->ibuf;
+
+  memset(&p, 0, sizeof(struct prefix));
+  p.family = stream_getw(s);
+  p.prefixlen = stream_getc(s);
+  switch (p.family)
+    {
+    case AF_INET:
+      p.u.prefix4.s_addr = stream_get_ipv4 (s);
+      break;
+    case AF_INET6:
+      stream_get(&p.u.prefix6, s, 16);
+      break;
+    default:
+      break;
+    }
+
+  rn = bgp_node_lookup(bgp_nexthop_cache_table[family2afi(p.family)], &p);
+  if (!rn || !rn->info)
+    {
+      if (BGP_DEBUG(nht, NHT))
+	{
+	  char buf[INET6_ADDRSTRLEN];
+	  prefix2str(&p, buf, INET6_ADDRSTRLEN);
+	  zlog_debug("parse nexthop update(%s): rn not found", buf);
+	}
+      if (rn)
+        bgp_unlock_node (rn);
+      return;
+    }
+
+  bnc = rn->info;
+  bgp_unlock_node (rn);
+  bnc->last_update = bgp_clock();
+  bnc->change_flags = 0;
+  metric = stream_getl (s);
+  nexthop_num = stream_getc (s);
+
+  /* debug print the input */
+  if (BGP_DEBUG(nht, NHT))
+    {
+      char buf[INET6_ADDRSTRLEN];
+      prefix2str(&p, buf, INET6_ADDRSTRLEN);
+      zlog_debug("parse nexthop update(%s): metric=%d, #nexthop=%d", buf,
+		 metric, nexthop_num);
+    }
+
+  if (metric != bnc->metric)
+    bnc->change_flags |= BGP_NEXTHOP_METRIC_CHANGED;
+
+  if(nexthop_num != bnc->nexthop_num)
+    bnc->change_flags |= BGP_NEXTHOP_CHANGED;
+
+  if (nexthop_num)
+    {
+      bnc->flags |= BGP_NEXTHOP_VALID;
+      bnc->metric = metric;
+      bnc->nexthop_num = nexthop_num;
+
+      for (i = 0; i < nexthop_num; i++)
+	{
+	  nexthop = nexthop_new();
+	  nexthop->type = stream_getc (s);
+	  switch (nexthop->type)
+	    {
+	    case ZEBRA_NEXTHOP_IPV4:
+	      nexthop->gate.ipv4.s_addr = stream_get_ipv4 (s);
+	      break;
+	    case ZEBRA_NEXTHOP_IFINDEX:
+	    case ZEBRA_NEXTHOP_IFNAME:
+	      nexthop->ifindex = stream_getl (s);
+	      break;
+            case ZEBRA_NEXTHOP_IPV4_IFINDEX:
+	    case ZEBRA_NEXTHOP_IPV4_IFNAME:
+	      nexthop->gate.ipv4.s_addr = stream_get_ipv4 (s);
+	      nexthop->ifindex = stream_getl (s);
+	      break;
+#ifdef HAVE_IPV6
+            case ZEBRA_NEXTHOP_IPV6:
+	      stream_get (&nexthop->gate.ipv6, s, 16);
+	      break;
+            case ZEBRA_NEXTHOP_IPV6_IFINDEX:
+	    case ZEBRA_NEXTHOP_IPV6_IFNAME:
+	      stream_get (&nexthop->gate.ipv6, s, 16);
+	      nexthop->ifindex = stream_getl (s);
+	      break;
+#endif
+            default:
+              /* do nothing */
+              break;
+	    }
+
+	  if (nhlist_tail)
+	    {
+	      nhlist_tail->next = nexthop;
+	      nhlist_tail = nexthop;
+	    }
+	  else
+	    {
+	      nhlist_tail = nexthop;
+	      nhlist_head = nexthop;
+	    }
+
+	  /* No need to evaluate the nexthop if we have already determined
+	   * that there has been a change.
+	   */
+	  if (bnc->change_flags & BGP_NEXTHOP_CHANGED)
+	    continue;
+
+	  for (oldnh = bnc->nexthop; oldnh; oldnh = oldnh->next)
+	      if (nexthop_same_no_recurse(oldnh, nexthop))
+		  break;
+
+	  if (!oldnh)
+	    bnc->change_flags |= BGP_NEXTHOP_CHANGED;
+	}
+      bnc_nexthop_free(bnc);
+      bnc->nexthop = nhlist_head;
+    }
+  else
+    {
+      bnc->flags &= ~BGP_NEXTHOP_VALID;
+      bnc_nexthop_free(bnc);
+      bnc->nexthop = NULL;
+    }
+
+  evaluate_paths(bnc);
+}
+
+/**
+ * make_prefix - make a prefix structure from the path (essentially
+ * path's node.
+ */
+static int
+make_prefix (int afi, struct bgp_info *ri, struct prefix *p)
+{
+  memset (p, 0, sizeof (struct prefix));
+  switch (afi)
+    {
+    case AFI_IP:
+      p->family = AF_INET;
+      p->prefixlen = IPV4_MAX_BITLEN;
+      p->u.prefix4 = ri->attr->nexthop;
+      break;
+#ifdef HAVE_IPV6
+    case AFI_IP6:
+      if (ri->attr->extra->mp_nexthop_len != 16
+	  || IN6_IS_ADDR_LINKLOCAL (&ri->attr->extra->mp_nexthop_global))
+	return -1;
+
+      p->family = AF_INET6;
+      p->prefixlen = IPV6_MAX_BITLEN;
+      p->u.prefix6 = ri->attr->extra->mp_nexthop_global;
+      break;
+#endif
+    default:
+      break;
+    }
+  return 0;
+}
+
+/**
+ * sendmsg_nexthop -- Format and send a nexthop register/Unregister
+ *   command to Zebra.
+ * ARGUMENTS:
+ *   struct bgp_nexthop_cache *bnc -- the nexthop structure.
+ *   int command -- either ZEBRA_NEXTHOP_REGISTER or ZEBRA_NEXTHOP_UNREGISTER
+ * RETURNS:
+ *   void.
+ */
+static void
+sendmsg_nexthop (struct bgp_nexthop_cache *bnc, int command)
+{
+  struct stream *s;
+  struct prefix *p;
+  int ret;
+
+  /* Check socket. */
+  if (!zclient || zclient->sock < 0)
+    return;
+
+  p = &(bnc->node->p);
+  s = zclient->obuf;
+  stream_reset (s);
+  zclient_create_header (s, command, VRF_DEFAULT);
+  stream_putw(s, PREFIX_FAMILY(p));
+  stream_putc(s, p->prefixlen);
+  switch (PREFIX_FAMILY(p))
+    {
+    case AF_INET:
+      stream_put_in_addr (s, &p->u.prefix4);
+      break;
+#ifdef HAVE_IPV6
+    case AF_INET6:
+      stream_put(s, &(p->u.prefix6), 16);
+      break;
+#endif
+    default:
+      break;
+    }
+  stream_putw_at (s, 0, stream_get_endp (s));
+
+  ret = zclient_send_message(zclient);
+  /* TBD: handle the failure */
+  if (ret < 0)
+    zlog_warn("sendmsg_nexthop: zclient_send_message() failed");
+  return;
+}
+
+/**
+ * register_nexthop - register a nexthop with Zebra for notification
+ *    when the route to the nexthop changes.
+ * ARGUMENTS:
+ *   struct bgp_nexthop_cache *bnc -- the nexthop structure.
+ * RETURNS:
+ *   void.
+ */
+static void
+register_nexthop (struct bgp_nexthop_cache *bnc)
+{
+  /* Check if we have already registered */
+  if (bnc->flags & BGP_NEXTHOP_REGISTERED)
+    return;
+  sendmsg_nexthop(bnc, ZEBRA_NEXTHOP_REGISTER);
+  SET_FLAG(bnc->flags, BGP_NEXTHOP_REGISTERED);
+}
+
+/**
+ * unregister_nexthop -- Unregister the nexthop from Zebra.
+ * ARGUMENTS:
+ *   struct bgp_nexthop_cache *bnc -- the nexthop structure.
+ * RETURNS:
+ *   void.
+ */
+static void
+unregister_nexthop (struct bgp_nexthop_cache *bnc)
+{
+  /* Check if we have already registered */
+  if (!CHECK_FLAG(bnc->flags, BGP_NEXTHOP_REGISTERED))
+    return;
+
+  sendmsg_nexthop(bnc, ZEBRA_NEXTHOP_UNREGISTER);
+  UNSET_FLAG(bnc->flags, BGP_NEXTHOP_REGISTERED);
+}
+
+/**
+ * evaluate_paths - Evaluate the paths/nets associated with a nexthop.
+ * ARGUMENTS:
+ *   struct bgp_nexthop_cache *bnc -- the nexthop structure.
+ * RETURNS:
+ *   void.
+ */
+static void
+evaluate_paths (struct bgp_nexthop_cache *bnc)
+{
+  struct bgp_node *rn;
+  struct bgp_info *path;
+  struct bgp *bgp = bgp_get_default();
+  int afi;
+
+  LIST_FOREACH(path, &(bnc->paths), nh_thread)
+    {
+      if (!(path->type == ZEBRA_ROUTE_BGP &&
+	    path->sub_type == BGP_ROUTE_NORMAL))
+	continue;
+
+      rn = path->net;
+      afi = family2afi(rn->p.family);
+
+      /* Path becomes valid/invalid depending on whether the nexthop
+       * reachable/unreachable.
+       */
+      if ((CHECK_FLAG(path->flags, BGP_INFO_VALID) ? 1 : 0) !=
+	  (CHECK_FLAG(bnc->flags, BGP_NEXTHOP_VALID) ? 1 : 0))
+	{
+	  if (CHECK_FLAG (path->flags, BGP_INFO_VALID))
+	    {
+	      bgp_aggregate_decrement (bgp, &rn->p, path,
+				       afi, SAFI_UNICAST);
+	      bgp_info_unset_flag (rn, path, BGP_INFO_VALID);
+	    }
+	  else
+	    {
+	      bgp_info_set_flag (rn, path, BGP_INFO_VALID);
+	      bgp_aggregate_increment (bgp, &rn->p, path,
+				       afi, SAFI_UNICAST);
+	    }
+	}
+
+      /* Copy the metric to the path. Will be used for bestpath computation */
+      if (CHECK_FLAG(bnc->flags, BGP_NEXTHOP_VALID) && bnc->metric)
+	(bgp_info_extra_get(path))->igpmetric = bnc->metric;
+      else if (path->extra)
+	path->extra->igpmetric = 0;
+
+      if (CHECK_FLAG(bnc->flags, BGP_NEXTHOP_METRIC_CHANGED) ||
+	  CHECK_FLAG(bnc->flags, BGP_NEXTHOP_CHANGED))
+	SET_FLAG(path->flags, BGP_INFO_IGP_CHANGED);
+
+      bgp_process(bgp, rn, afi, SAFI_UNICAST);
+    }
+  RESET_FLAG(bnc->change_flags);
+}
+
+/**
+ * path_nh_map - make or break path-to-nexthop association.
+ * ARGUMENTS:
+ *   path - pointer to the path structure
+ *   bnc - pointer to the nexthop structure
+ *   make - if set, make the association. if unset, just break the existing
+ *          association.
+ */
+static void
+path_nh_map (struct bgp_info *path, struct bgp_nexthop_cache *bnc, int make)
+{
+  if (path->nexthop)
+    {
+      LIST_REMOVE(path, nh_thread);
+      path->nexthop->path_count--;
+      path->nexthop = NULL;
+    }
+  if (make)
+    {
+      LIST_INSERT_HEAD(&(bnc->paths), path, nh_thread);
+      path->nexthop = bnc;
+      path->nexthop->path_count++;
+    }
+}

bgpd/bgp_nht.h

@@ -0,0 +1,62 @@
+/* BGP Nexthop tracking
+ * Copyright (C) 2013 Cumulus Networks, Inc.
+ *
+ * This file is part of GNU Zebra.
+ *
+ * GNU Zebra is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * GNU Zebra is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Zebra; see the file COPYING.  If not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef _BGP_NHT_H
+#define _BGP_NHT_H
+
+/**
+ * bgp_parse_nexthop_update() - parse a nexthop update message from Zebra.
+ */
+extern void bgp_parse_nexthop_update(void);
+
+/**
+ * bgp_find_nexthop() - lookup the nexthop cache table for the bnc object
+ * ARGUMENTS:
+ *   p - path for which the nexthop object is being looked up
+ *   c - output variable that stores whether the nexthop object has changed
+ *        since last time.
+ *   m - output variable that stores whether the nexthop metric has changed
+ *        since last time.
+ */
+extern int bgp_find_nexthop(struct bgp_info *p, int *c, int *m);
+
+/**
+ * bgp_find_or_add_nexthop() - lookup the nexthop cache table for the bnc
+ *  object. If not found, create a new object and register with ZEBRA for
+ *  nexthop notification.
+ * ARGUMENTS:
+ *   a - afi: AFI_IP or AF_IP6
+ *   p - path for which the nexthop object is being looked up
+ *   c - output variable that stores whether the nexthop object has changed
+ *        since last time.
+ *   m - output variable that stores whether the nexthop metric has changed
+ *        since last time.
+ */
+extern int bgp_find_or_add_nexthop(afi_t a, struct bgp_info *p, int *c, int *m);
+
+/**
+ * bgp_unlink_nexthop() - Unlink the nexthop object from the path structure.
+ * ARGUMENTS:
+ *   p - path structure.
+ */
+extern void bgp_unlink_nexthop(struct bgp_info *p);
+
+#endif /* _BGP_NHT_H */

bgpd/bgp_route.c

@@ -55,6 +55,7 @@ Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 #include "bgpd/bgp_zebra.h"
 #include "bgpd/bgp_vty.h"
 #include "bgpd/bgp_mpath.h"
+#include "bgpd/bgp_nht.c"
 
 /* Extern from bgp_dump.c */
 extern const char *bgp_origin_str[];
@@ -126,20 +127,14 @@ bgp_info_extra_get (struct bgp_info *ri)
   return ri->extra;
 }
 
-/* Allocate new bgp info structure. */
-static struct bgp_info *
-bgp_info_new (void)
-{
-  return XCALLOC (MTYPE_BGP_ROUTE, sizeof (struct bgp_info));
-}
-
 /* Free bgp route information. */
 static void
 bgp_info_free (struct bgp_info *binfo)
 {
   if (binfo->attr)
     bgp_attr_unintern (&binfo->attr);
-  
+
+  bgp_unlink_nexthop(binfo);
   bgp_info_extra_free (&binfo->extra);
   bgp_info_mpath_free (&binfo->mpath);
 
@@ -1882,6 +1877,23 @@ bgp_rib_withdraw (struct bgp_node *rn, struct bgp_info *ri, struct peer *peer,
   bgp_rib_remove (rn, ri, peer, afi, safi);
 }
 
+static struct bgp_info *
+info_make (int type, int sub_type, struct peer *peer, struct attr *attr,
+	   struct bgp_node *rn)
+{
+  struct bgp_info *new;
+
+  /* Make new BGP info. */
+  new = XCALLOC (MTYPE_BGP_ROUTE, sizeof (struct bgp_info));
+  new->type = type;
+  new->sub_type = sub_type;
+  new->peer = peer;
+  new->attr = attr;
+  new->uptime = bgp_clock ();
+  new->net = rn;
+  return new;
+}
+
 static void
 bgp_update_rsclient (struct peer *rsclient, afi_t afi, safi_t safi,
       struct attr *attr, struct peer *peer, struct prefix *p, int type,
@@ -2029,13 +2041,7 @@ bgp_update_rsclient (struct peer *rsclient, afi_t afi, safi_t safi,
               p->prefixlen, rsclient->host);
     }
 
-  /* Make new BGP info. */
-  new = bgp_info_new ();
-  new->type = type;
-  new->sub_type = sub_type;
-  new->peer = peer;
-  new->attr = attr_new;
-  new->uptime = bgp_clock ();
+  new = info_make(type, sub_type, peer, attr_new, rn);
 
   /* Update MPLS tag. */
   if (safi == SAFI_MPLS_VPN)
@@ -2347,7 +2353,7 @@ bgp_update_main (struct peer *peer, struct prefix *p, struct attr *attr,
 	      || (peer->sort == BGP_PEER_EBGP && peer->ttl != 1)
 	      || CHECK_FLAG (peer->flags, PEER_FLAG_DISABLE_CONNECTED_CHECK)))
 	{
-	  if (bgp_nexthop_lookup (afi, peer, ri, NULL, NULL))
+	  if (bgp_find_or_add_nexthop (afi, ri, NULL, NULL))
 	    bgp_info_set_flag (rn, ri, BGP_INFO_VALID);
 	  else
 	    bgp_info_unset_flag (rn, ri, BGP_INFO_VALID);
@@ -2376,12 +2382,7 @@ bgp_update_main (struct peer *peer, struct prefix *p, struct attr *attr,
     }
 
   /* Make new BGP info. */
-  new = bgp_info_new ();
-  new->type = type;
-  new->sub_type = sub_type;
-  new->peer = peer;
-  new->attr = attr_new;
-  new->uptime = bgp_clock ();
+  new = info_make(type, sub_type, peer, attr_new, rn);
 
   /* Update MPLS tag. */
   if (safi == SAFI_MPLS_VPN)
@@ -2395,7 +2396,7 @@ bgp_update_main (struct peer *peer, struct prefix *p, struct attr *attr,
 	  || (peer->sort == BGP_PEER_EBGP && peer->ttl != 1)
 	  || CHECK_FLAG (peer->flags, PEER_FLAG_DISABLE_CONNECTED_CHECK)))
     {
-      if (bgp_nexthop_lookup (afi, peer, new, NULL, NULL))
+      if (bgp_find_or_add_nexthop (afi, new, NULL, NULL))
 	bgp_info_set_flag (rn, new, BGP_INFO_VALID);
       else
         bgp_info_unset_flag (rn, new, BGP_INFO_VALID);
@@ -3538,15 +3539,11 @@ bgp_static_update_rsclient (struct peer *rsclient, struct prefix *p,
           return;
         }
     }
-  
+
   /* Make new BGP info. */
-  new = bgp_info_new ();
-  new->type = ZEBRA_ROUTE_BGP;
-  new->sub_type = BGP_ROUTE_STATIC;
-  new->peer = bgp->peer_self;
+  new = info_make(ZEBRA_ROUTE_BGP, BGP_ROUTE_STATIC, bgp->peer_self,
+		  attr_new, rn);
   SET_FLAG (new->flags, BGP_INFO_VALID);
-  new->attr = attr_new;
-  new->uptime = bgp_clock ();
 
   /* Register new BGP information. */
   bgp_info_add (rn, new);
@@ -3659,13 +3656,9 @@ bgp_static_update_main (struct bgp *bgp, struct prefix *p,
     }
 
   /* Make new BGP info. */
-  new = bgp_info_new ();
-  new->type = ZEBRA_ROUTE_BGP;
-  new->sub_type = BGP_ROUTE_STATIC;
-  new->peer = bgp->peer_self;
+  new = info_make(ZEBRA_ROUTE_BGP, BGP_ROUTE_STATIC, bgp->peer_self, attr_new,
+		  rn);
   SET_FLAG (new->flags, BGP_INFO_VALID);
-  new->attr = attr_new;
-  new->uptime = bgp_clock ();
 
   /* Aggregate address increment. */
   bgp_aggregate_increment (bgp, p, new, afi, safi);
@@ -3706,8 +3699,14 @@ bgp_static_withdraw (struct bgp *bgp, struct prefix *p, afi_t afi,
 {
   struct bgp_node *rn;
   struct bgp_info *ri;
+  struct bgp_info *new;
 
-  rn = bgp_afi_node_get (bgp->rib[afi][safi], afi, safi, p, NULL);
+  /* Make new BGP info. */
+  rn = bgp_node_get (bgp->rib[afi][safi], p);
+  new = info_make(ZEBRA_ROUTE_BGP, BGP_ROUTE_STATIC, bgp->peer_self,
+		  bgp_attr_default_intern(BGP_ORIGIN_IGP), rn);
+
+  SET_FLAG (new->flags, BGP_INFO_VALID);
 
   /* Check selected route and self inserted route. */
   for (ri = rn->info; ri; ri = ri->next)
@@ -3877,13 +3876,9 @@ bgp_static_update_safi (struct bgp *bgp, struct prefix *p,
 
 
   /* Make new BGP info. */
-  new = bgp_info_new ();
-  new->type = ZEBRA_ROUTE_BGP;
-  new->sub_type = BGP_ROUTE_STATIC;
-  new->peer = bgp->peer_self;
-  new->attr = attr_new;
+  new = info_make (ZEBRA_ROUTE_BGP, BGP_ROUTE_STATIC, bgp->peer_self,
+		   attr_new, rn);
   SET_FLAG (new->flags, BGP_INFO_VALID);
-  new->uptime = bgp_clock ();
   new->extra = bgp_info_extra_new();
   memcpy (new->extra->tag, bgp_static->tag, 3);
 
@@ -4881,13 +4876,10 @@ bgp_aggregate_route (struct bgp *bgp, struct prefix *p, struct bgp_info *rinew,
   if (aggregate->count > 0)
     {
       rn = bgp_node_get (table, p);
-      new = bgp_info_new ();
-      new->type = ZEBRA_ROUTE_BGP;
-      new->sub_type = BGP_ROUTE_AGGREGATE;
-      new->peer = bgp->peer_self;
+      new = info_make(ZEBRA_ROUTE_BGP, BGP_ROUTE_AGGREGATE, bgp->peer_self,
+		      bgp_attr_aggregate_intern(bgp, origin, aspath, community,
+						aggregate->as_set), rn);
       SET_FLAG (new->flags, BGP_INFO_VALID);
-      new->attr = bgp_attr_aggregate_intern (bgp, origin, aspath, community, aggregate->as_set);
-      new->uptime = bgp_clock ();
 
       bgp_info_add (rn, new);
       bgp_unlock_node (rn);
@@ -5065,14 +5057,10 @@ bgp_aggregate_add (struct bgp *bgp, struct prefix *p, afi_t afi, safi_t safi,
   if (aggregate->count)
     {
       rn = bgp_node_get (table, p);
-
-      new = bgp_info_new ();
-      new->type = ZEBRA_ROUTE_BGP;
-      new->sub_type = BGP_ROUTE_AGGREGATE;
-      new->peer = bgp->peer_self;
+      new = info_make(ZEBRA_ROUTE_BGP, BGP_ROUTE_AGGREGATE, bgp->peer_self,
+		      bgp_attr_aggregate_intern(bgp, origin, aspath, community,
+						aggregate->as_set), rn);
       SET_FLAG (new->flags, BGP_INFO_VALID);
-      new->attr = bgp_attr_aggregate_intern (bgp, origin, aspath, community, aggregate->as_set);
-      new->uptime = bgp_clock ();
 
       bgp_info_add (rn, new);
       bgp_unlock_node (rn);
@@ -5715,16 +5703,12 @@ bgp_redistribute_add (struct prefix *p, const struct in_addr *nexthop,
  		  aspath_unintern (&attr.aspath);
  		  bgp_attr_extra_free (&attr);
  		  return;
- 		} 
+		}
  	    }
 
-	  new = bgp_info_new ();
-	  new->type = type;
-	  new->sub_type = BGP_ROUTE_REDISTRIBUTE;
-	  new->peer = bgp->peer_self;
+	  new = info_make(type, BGP_ROUTE_REDISTRIBUTE, bgp->peer_self,
+			  new_attr, bn);
 	  SET_FLAG (new->flags, BGP_INFO_VALID);
-	  new->attr = new_attr;
-	  new->uptime = bgp_clock ();
 
 	  bgp_aggregate_increment (bgp, p, new, afi, SAFI_UNICAST);
 	  bgp_info_add (bn, new);

bgpd/bgp_route.h

@@ -21,8 +21,11 @@ Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
 #ifndef _QUAGGA_BGP_ROUTE_H
 #define _QUAGGA_BGP_ROUTE_H
 
+#include "queue.h"
 #include "bgp_table.h"
 
+struct bgp_nexthop_cache;
+
 /* Ancillary information to struct bgp_info, 
  * used for uncommonly used data (aggregation, MPLS, etc.)
  * and lazily allocated to save memory.
@@ -47,7 +50,16 @@ struct bgp_info
   /* For linked list. */
   struct bgp_info *next;
   struct bgp_info *prev;
-  
+
+  /* For nexthop linked list */
+  LIST_ENTRY(bgp_info) nh_thread;
+
+  /* Back pointer to the prefix node */
+  struct bgp_node *net;
+
+  /* Back pointer to the nexthop structure */
+  struct bgp_nexthop_cache *nexthop;
+
   /* Peer structure.  */
   struct peer *peer;
 

bgpd/bgp_zebra.c

@@ -39,6 +39,8 @@ Boston, MA 02111-1307, USA.  */
 #include "bgpd/bgp_fsm.h"
 #include "bgpd/bgp_debug.h"
 #include "bgpd/bgp_mpath.h"
+#include "bgpd/bgp_nexthop.h"
+#include "bgpd/bgp_nht.h"
 
 /* All information about zebra. */
 struct zclient *zclient = NULL;
@@ -70,6 +72,15 @@ bgp_router_id_update (int command, struct zclient *zclient, zebra_size_t length,
   return 0;
 }
 
+/* Nexthop update message from zebra. */
+static int
+bgp_read_nexthop_update (int command, struct zclient *zclient,
+			 zebra_size_t length, vrf_id_t vrf_id)
+{
+  bgp_parse_nexthop_update();
+  return 0;
+}
+
 /* Inteface addition message from zebra. */
 static int
 bgp_interface_add (int command, struct zclient *zclient, zebra_size_t length,
@@ -1160,6 +1171,7 @@ bgp_zebra_init (struct thread_master *master)
   zclient->interface_down = bgp_interface_down;
   zclient->ipv6_route_add = zebra_read_ipv6;
   zclient->ipv6_route_delete = zebra_read_ipv6;
+  zclient->nexthop_update = bgp_read_nexthop_update;
 
   bgp_nexthop_buf = stream_new(BGP_NEXTHOP_BUF_SIZE);
   bgp_ifindices_buf = stream_new(BGP_IFINDICES_BUF_SIZE);

doc/next-hop-tracking.txt

@@ -0,0 +1,326 @@
+0. Introduction
+
+This is the design specification for next hop tracking feature in
+Quagga.
+
+1. Background
+
+Recursive routes are of the form:
+
+   p/m --> n
+  [Ex: 1.1.0.0/16 --> 2.2.2.2]
+
+where 'n' itself is resolved through another route as follows:
+
+   p2/m --> h, interface
+  [Ex: 2.2.2.0/24 --> 3.3.3.3, eth0]
+
+Usually, BGP routes are recursive in nature and BGP nexthops get
+resolved through an IGP route. IGP usually adds its routes pointing to
+an interface (these are called non-recursive routes).
+
+When BGP receives a recursive route from a peer, it needs to validate
+the nexthop. The path is marked valid or invalid based on the
+reachability status of the nexthop.  Nexthop validation is also
+important for BGP decision process as the metric to reach the nexthop
+is a parameter to best path selection process.
+
+As it goes with routing, this is a dynamic process. Route to the
+nexthop can change. The nexthop can become unreachable or
+reachable. In the current BGP implementation, the nexthop validation
+is done periodically in the scanner run. The default scanner run
+interval is one minute. Every minute, the scanner task walks the
+entire BGP table. It checks the validity of each nexthop with Zebra
+(the routing table manager) through a request and response message
+exchange between BGP and Zebra process. BGP process is blocked for
+that duration. The mechanism has two major drawbacks:
+
+(1) The scanner task runs to completion. That can potentially starve
+    the other tasks for long periods of time, based on the BGP table
+    size and number of nexthops.
+
+(2) Convergence around routing changes that affect the nexthops can be
+    long (around a minute with the default intervals). The interval
+    can be shortened to achieve faster reaction time, but it makes the
+    first problem worse, with the scanner task consuming most of the
+    CPU resources.
+
+"Next hop tracking" feature makes this process event-driven. It
+eliminates periodic nexthop validation and introduces an asynchronous
+communication path between BGP and Zebra for route change notifications
+that can then be acted upon.
+
+2. Goal
+
+Stating the obvious, the main goal is to remove the two limitations we
+discussed in the previous section. The goals, in a constructive tone,
+are the following:
+
+- fairness: the scanner run should not consume an unjustly high amount
+  of CPU time. This should give an overall good performance and
+  response time to other events (route changes, session events,
+  IO/user interface).
+
+- convergence: BGP must react to nexthop changes instantly and provide
+  sub-second convergence. This may involve diverting the routes from
+  one nexthop to another.
+
+3. Overview of the changes
+
+The changes are in both BGP and Zebra modules.  The short summary is
+the following:
+
+- Zebra implements a registration mechanism by which clients can
+   register for next hop notification. Consequently, it maintains a
+   separate table, per (VRF, AF) pair, of next hops and interested
+   client-list per next hop.
+
+- When the main routing table changes in Zebra, it evaluates the next
+   hop table: for each next hop, it checks if the route table
+   modifications have changed its state. If so, it notifies the
+   interested clients.
+
+- BGP is one such client. It registers the next hops corresponding to
+   all of its received routes/paths. It also threads the paths against
+   each nexthop structure.
+
+- When BGP receives a next hop notification from Zebra, it walks the
+   corresponding path list. It makes them valid or invalid depending
+   on the next hop notification. It then re-computes best path for the
+   corresponding destination. This may result in re-announcing those
+   destinations to peers.
+
+4. Design
+
+4.1. Modules
+
+The core design introduces an "nht" (next hop tracking) module in BGP
+and "rnh" (recursive nexthop) module in Zebra. The "nht" module
+provides the following APIs:
+
+bgp_find_or_add_nexthop() : find or add a nexthop in BGP nexthop table
+bgp_find_nexthop() : find a nexthop in BGP nexthop table
+bgp_parse_nexthop_update() : parse a nexthop update message coming
+                              from zebra
+
+The "rnh" module provides the following APIs:
+
+zebra_add_rnh() : add a recursive nexthop
+zebra_delete_rnh() : delete a recursive nexthop
+zebra_lookup_rnh() : lookup a recursive nexthop
+
+zebra_add_rnh_client() : register a client for nexthop notifications
+                         against a recursive nexthop
+
+zebra_remove_rnh_client(): remove the client registration for a
+                            recursive nexthop
+
+zebra_evaluate_rnh_table(): (re)evaluate the recursive nexthop table
+                            (most probably because the main routing
+                            table has changed).
+
+zebra_cleanup_rnh_client(): Cleanup a client from the "rnh" module
+                            data structures (most probably because the
+                            client is going away).
+
+4.2. Control flow
+
+The next hop registration control flow is the following:
+
+<====      BGP Process       ====>|<====      Zebra Process      ====>
+                                  |
+receive module     nht module     |  zserv module        rnh module
+----------------------------------------------------------------------
+              |                   |                  |
+bgp_update_   |                   |                  |
+      main()  | bgp_find_or_add_  |                  |
+              |        nexthop()  |                  |
+              |                   |                  |
+              |                   | zserv_nexthop_   |
+              |                   |       register() |
+              |                   |                  | zebra_add_rnh()
+              |                   |                  |
+
+
+The next hop notification control flow is the following:
+
+<====     Zebra Process    ====>|<====      BGP Process       ====>
+                                |
+rib module         rnh module   |     zebra module        nht module
+----------------------------------------------------------------------
+              |                 |                   |
+meta_queue_   |                 |                   |
+    process() | zebra_evaluate_ |                   |
+              |     rnh_table() |                   |
+              |                 |                   |
+              |                 | bgp_read_nexthop_ |
+              |                 |          update() |
+              |                 |                   | bgp_parse_
+              |                 |                   | nexthop_update()
+              |                 |                   |
+
+
+4.3. zclient message format
+
+ZEBRA_NEXTHOP_REGISTER and ZEBRA_NEXTHOP_UNREGISTER messages are
+encoded in the following way:
+
+/*
+ *     0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |     AF                        |  prefix len   |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .      Nexthop prefix                                           .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .                                                               .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |     AF                        |  prefix len   |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .      Nexthop prefix                                           .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+
+ZEBRA_NEXTHOP_UPDATE message is encoded as follows:
+
+/*
+ *     0                   1                   2                   3
+ *  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |     AF                        |  prefix len   |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .      Nexthop prefix getting resolved                          .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |        metric                                                 |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * |  #nexthops    |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | nexthop type  |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .      resolving Nexthop details                                .
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .                                                               .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * | nexthop type  |
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ * .      resolving Nexthop details                                .
+ * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ */
+
+4.4. BGP data structure
+
+Legend:
+
+/\   struct bgp_node: a BGP destination/route/prefix
+\/
+
+[ ]  struct bgp_info: a BGP path (e.g. route received from a peer)
+
+ _
+(_)  struct bgp_nexthop_cache: a BGP nexthop
+
+
+
+   /\         NULL
+   \/--+        ^
+       |        :
+       +--[ ]--[ ]--[ ]--> NULL
+   /\           :
+   \/--+        :
+       |        :
+       +--[ ]--[ ]--> NULL
+                :
+  _             :
+ (_).............
+
+
+4.5. Zebra data structure
+
+rnh table:
+
+           O
+          / \
+         O   O
+            / \
+           O   O
+
+        struct rnh
+        {
+          u_char flags;
+          struct rib *state;
+          struct list *client_list;
+          struct route_node *node;
+        };
+
+5. User interface changes
+
+quagga# show ip nht
+3.3.3.3
+ resolved via kernel
+ via 11.0.0.6, swp1
+ Client list: bgp(fd 12)
+11.0.0.10
+ resolved via connected
+ is directly connected, swp2
+ Client list: bgp(fd 12)
+11.0.0.18
+ resolved via connected
+ is directly connected, swp4
+ Client list: bgp(fd 12)
+11.11.11.11
+ resolved via kernel
+ via 10.0.1.2, eth0
+ Client list: bgp(fd 12)
+
+quagga# show ip bgp nexthop
+Current BGP nexthop cache:
+ 3.3.3.3 valid [IGP metric 0], #paths 3
+  Last update: Wed Oct 16 04:43:49 2013
+
+ 11.0.0.10 valid [IGP metric 1], #paths 1
+  Last update: Wed Oct 16 04:43:51 2013
+
+ 11.0.0.18 valid [IGP metric 1], #paths 2
+  Last update: Wed Oct 16 04:43:47 2013
+
+ 11.11.11.11 valid [IGP metric 0], #paths 1
+  Last update: Wed Oct 16 04:43:47 2013
+
+quagga# show ipv6 nht
+quagga# show ip bgp nexthop detail
+
+quagga# debug bgp nht
+quagga# debug zebra nht
+
+6. Sample test cases
+
+     r2----r3
+    /  \  /
+  r1----r4
+
+- Verify that a change in IGP cost triggers NHT
+  + shutdown the r1-r4 and r2-r4 links
+  + no shut the r1-r4 and r2-r4 links and wait for OSPF to come back
+    up
+  + We should be back to the original nexthop via r4 now
+- Verify that a NH becoming unreachable triggers NHT
+  + Shutdown all links to r4
+- Verify that a NH becoming reachable triggers NHT
+  + no shut all links to r4
+
+7. Future work
+
+- route-policy for next hop validation (e.g. ignore default route)
+- damping for rapid next hop changes
+- prioritized handling of nexthop changes ((un)reachability vs. metric
+  changes)
+- handling recursion loop, e.g.
+   11.11.11.11/32 -> 12.12.12.12
+   12.12.12.12/32 -> 11.11.11.11
+   11.0.0.0/8 -> <interface>
+- better statistics

lib/Makefile.am

@@ -13,7 +13,8 @@ libzebra_la_SOURCES = \
 	sockunion.c prefix.c thread.c if.c memory.c buffer.c table.c hash.c \
 	filter.c routemap.c distribute.c stream.c str.c log.c plist.c \
 	zclient.c sockopt.c smux.c agentx.c snmp.c md5.c if_rmap.c keychain.c privs.c \
-	sigevent.c pqueue.c jhash.c memtypes.c workqueue.c vrf.c event_counter.c
+	sigevent.c pqueue.c jhash.c memtypes.c workqueue.c vrf.c \
+	event_counter.c nexthop.c
 
 BUILT_SOURCES = memtypes.h route_types.h gitversion.h
 
@@ -28,7 +29,8 @@ pkginclude_HEADERS = \
 	str.h stream.h table.h thread.h vector.h version.h vty.h zebra.h \
 	plist.h zclient.h sockopt.h smux.h md5.h if_rmap.h keychain.h \
 	privs.h sigevent.h pqueue.h jhash.h zassert.h memtypes.h \
-	workqueue.h route_types.h libospf.h vrf.h fifo.h event_counter.h
+	workqueue.h route_types.h libospf.h vrf.h fifo.h event_counter.h \
+	nexthop.h
 
 noinst_HEADERS = \
 	plist_int.h

lib/log.c

@@ -895,6 +895,9 @@ static const struct zebra_desc_table command_types[] = {
   DESC_ENTRY	(ZEBRA_ROUTER_ID_DELETE),
   DESC_ENTRY	(ZEBRA_ROUTER_ID_UPDATE),
   DESC_ENTRY	(ZEBRA_HELLO),
+  DESC_ENTRY	(ZEBRA_NEXTHOP_REGISTER),
+  DESC_ENTRY	(ZEBRA_NEXTHOP_UNREGISTER),
+  DESC_ENTRY	(ZEBRA_NEXTHOP_UPDATE),
 };
 #undef DESC_ENTRY
 

lib/memtypes.c

@@ -87,6 +87,7 @@ struct memory_list memory_list_zebra[] =
   { MTYPE_RIB_DEST,		"RIB destination"		},
   { MTYPE_RIB_TABLE_INFO,	"RIB table info"		},
   { MTYPE_NETLINK_NAME,	"Netlink name"			},
+  { MTYPE_RNH,		        "Nexthop tracking object"	},
   { -1, NULL },
 };
 

lib/nexthop.c

@@ -0,0 +1,168 @@
+/* A generic nexthop structure
+ * Copyright (C) 2013 Cumulus Networks, Inc.
+ *
+ * This file is part of Quagga.
+ *
+ * Quagga is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * Quagga is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Quagga; see the file COPYING.  If not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+#include <zebra.h>
+
+#include "prefix.h"
+#include "table.h"
+#include "memory.h"
+#include "str.h"
+#include "command.h"
+#include "if.h"
+#include "log.h"
+#include "sockunion.h"
+#include "linklist.h"
+#include "thread.h"
+#include "prefix.h"
+#include "nexthop.h"
+
+/* check if nexthops are same, non-recursive */
+int
+nexthop_same_no_recurse (struct nexthop *next1, struct nexthop *next2)
+{
+  if (next1->type != next2->type)
+    return 0;
+
+  switch (next1->type)
+    {
+    case NEXTHOP_TYPE_IPV4:
+    case NEXTHOP_TYPE_IPV4_IFINDEX:
+      if (! IPV4_ADDR_SAME (&next1->gate.ipv4, &next2->gate.ipv4))
+	return 0;
+      if (next1->ifindex && (next1->ifindex != next2->ifindex))
+	return 0;
+      break;
+    case NEXTHOP_TYPE_IFINDEX:
+    case NEXTHOP_TYPE_IFNAME:
+      if (next1->ifindex != next2->ifindex)
+	return 0;
+      break;
+#ifdef HAVE_IPV6
+    case NEXTHOP_TYPE_IPV6:
+      if (! IPV6_ADDR_SAME (&next1->gate.ipv6, &next2->gate.ipv6))
+	return 0;
+      break;
+    case NEXTHOP_TYPE_IPV6_IFINDEX:
+    case NEXTHOP_TYPE_IPV6_IFNAME:
+      if (! IPV6_ADDR_SAME (&next1->gate.ipv6, &next2->gate.ipv6))
+	return 0;
+      if (next1->ifindex != next2->ifindex)
+	return 0;
+      break;
+#endif /* HAVE_IPV6 */
+    default:
+      /* do nothing */
+      break;
+    }
+  return 1;
+}
+
+/*
+ * nexthop_type_to_str
+ */
+const char *
+nexthop_type_to_str (enum nexthop_types_t nh_type)
+{
+  static const char *desc[] = {
+    "none",
+    "Directly connected",
+    "Interface route",
+    "IPv4 nexthop",
+    "IPv4 nexthop with ifindex",
+    "IPv4 nexthop with ifname",
+    "IPv6 nexthop",
+    "IPv6 nexthop with ifindex",
+    "IPv6 nexthop with ifname",
+    "Null0 nexthop",
+  };
+
+  if (nh_type >= ZEBRA_NUM_OF (desc))
+    return "<Invalid nh type>";
+
+  return desc[nh_type];
+}
+
+struct nexthop *
+nexthop_new (void)
+{
+  return XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+}
+
+/* Add nexthop to the end of a nexthop list.  */
+void
+nexthop_add (struct nexthop **target, struct nexthop *nexthop)
+{
+  struct nexthop *last;
+
+  for (last = *target; last && last->next; last = last->next)
+    ;
+  if (last)
+    last->next = nexthop;
+  else
+    *target = nexthop;
+  nexthop->prev = last;
+}
+
+void
+copy_nexthops (struct nexthop **tnh, struct nexthop *nh)
+{
+  struct nexthop *nexthop;
+  struct nexthop *nh1;
+
+  for (nh1 = nh; nh1; nh1 = nh1->next)
+    {
+      nexthop = nexthop_new();
+      nexthop->flags = nh->flags;
+      nexthop->type = nh->type;
+      nexthop->ifindex = nh->ifindex;
+      if (nh->ifname)
+	nexthop->ifname = XSTRDUP(0, nh->ifname);
+      memcpy(&(nexthop->gate), &(nh->gate), sizeof(union g_addr));
+      memcpy(&(nexthop->src), &(nh->src), sizeof(union g_addr));
+      nexthop_add(tnh, nexthop);
+
+      if (CHECK_FLAG(nh1->flags, NEXTHOP_FLAG_RECURSIVE))
+	copy_nexthops(&nexthop->resolved, nh1->resolved);
+    }
+}
+
+/* Free nexthop. */
+void
+nexthop_free (struct nexthop *nexthop)
+{
+  if (nexthop->ifname)
+    XFREE (0, nexthop->ifname);
+  if (nexthop->resolved)
+    nexthops_free(nexthop->resolved);
+  XFREE (MTYPE_NEXTHOP, nexthop);
+}
+
+/* Frees a list of nexthops */
+void
+nexthops_free (struct nexthop *nexthop)
+{
+  struct nexthop *nh, *next;
+
+  for (nh = nexthop; nh; nh = next)
+    {
+      next = nh->next;
+      nexthop_free (nh);
+    }
+}

lib/nexthop.h

@@ -0,0 +1,91 @@
+/*
+ * Nexthop structure definition.
+ * Copyright (C) 1997, 98, 99, 2001 Kunihiro Ishiguro
+ * Copyright (C) 2013 Cumulus Networks, Inc.
+ *
+ * This file is part of Quagga.
+ *
+ * Quagga is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2, or (at your option) any
+ * later version.
+ *
+ * Quagga is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Quagga; see the file COPYING.  If not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#ifndef _LIB_NEXTHOP_H
+#define _LIB_NEXTHOP_H
+
+#include "prefix.h"
+
+union g_addr {
+  struct in_addr ipv4;
+#ifdef HAVE_IPV6
+  struct in6_addr ipv6;
+#endif /* HAVE_IPV6 */
+};
+
+enum nexthop_types_t
+{
+  NEXTHOP_TYPE_IFINDEX = 1,      /* Directly connected.  */
+  NEXTHOP_TYPE_IFNAME,           /* Interface route.  */
+  NEXTHOP_TYPE_IPV4,             /* IPv4 nexthop.  */
+  NEXTHOP_TYPE_IPV4_IFINDEX,     /* IPv4 nexthop with ifindex.  */
+  NEXTHOP_TYPE_IPV4_IFNAME,      /* IPv4 nexthop with ifname.  */
+  NEXTHOP_TYPE_IPV6,             /* IPv6 nexthop.  */
+  NEXTHOP_TYPE_IPV6_IFINDEX,     /* IPv6 nexthop with ifindex.  */
+  NEXTHOP_TYPE_IPV6_IFNAME,      /* IPv6 nexthop with ifname.  */
+  NEXTHOP_TYPE_BLACKHOLE,        /* Null0 nexthop.  */
+};
+
+/* Nexthop structure. */
+struct nexthop
+{
+  struct nexthop *next;
+  struct nexthop *prev;
+
+  /* Interface index. */
+  char *ifname;
+  ifindex_t ifindex;
+
+  enum nexthop_types_t type;
+
+  u_char flags;
+#define NEXTHOP_FLAG_ACTIVE     (1 << 0) /* This nexthop is alive. */
+#define NEXTHOP_FLAG_FIB        (1 << 1) /* FIB nexthop. */
+#define NEXTHOP_FLAG_RECURSIVE  (1 << 2) /* Recursive nexthop. */
+#define NEXTHOP_FLAG_ONLINK     (1 << 3) /* Nexthop should be installed onlink. */
+#define NEXTHOP_FLAG_MATCHED    (1 << 4) /* Already matched vs a nexthop */
+
+  /* Nexthop address */
+  union g_addr gate;
+  union g_addr src;
+
+  /* Nexthops obtained by recursive resolution.
+   *
+   * If the nexthop struct needs to be resolved recursively,
+   * NEXTHOP_FLAG_RECURSIVE will be set in flags and the nexthops
+   * obtained by recursive resolution will be added to `resolved'.
+   * Only one level of recursive resolution is currently supported. */
+  struct nexthop *resolved;
+};
+
+struct nexthop *nexthop_new (void);
+void nexthop_add (struct nexthop **target, struct nexthop *nexthop);
+
+void copy_nexthops (struct nexthop **tnh, struct nexthop *nh);
+void nexthop_free (struct nexthop *nexthop);
+void nexthops_free (struct nexthop *nexthop);
+
+extern const char *nexthop_type_to_str (enum nexthop_types_t nh_type);
+extern int nexthop_same_no_recurse (struct nexthop *next1, struct nexthop *next2);
+
+#endif /*_LIB_NEXTHOP_H */

lib/zclient.c

@@ -1181,6 +1181,9 @@ zclient_read (struct thread *thread)
     case ZEBRA_INTERFACE_LINK_PARAMS:
       if (zclient->interface_link_params)
         (*zclient->interface_link_params) (command, zclient, length);
+    case ZEBRA_NEXTHOP_UPDATE:
+      if (zclient->nexthop_update)
+	(*zclient->nexthop_update) (command, zclient, length, vrf_id);
       break;
     default:
       break;

lib/zclient.h

@@ -90,6 +90,7 @@ struct zclient
   int (*ipv4_route_delete) (int, struct zclient *, uint16_t, vrf_id_t);
   int (*ipv6_route_add) (int, struct zclient *, uint16_t, vrf_id_t);
   int (*ipv6_route_delete) (int, struct zclient *, uint16_t, vrf_id_t);
+  int (*nexthop_update) (int, struct zclient *, uint16_t, vrf_id_t);
 };
 
 /* Zebra API message flag. */

lib/zebra.h

@@ -426,7 +426,10 @@ struct in_pktinfo
 #define ZEBRA_IPV4_NEXTHOP_LOOKUP_MRIB    24
 #define ZEBRA_VRF_UNREGISTER              25
 #define ZEBRA_INTERFACE_LINK_PARAMS       26
-#define ZEBRA_MESSAGE_MAX                 27
+#define ZEBRA_NEXTHOP_REGISTER            27
+#define ZEBRA_NEXTHOP_UNREGISTER          28
+#define ZEBRA_NEXTHOP_UPDATE              29
+#define ZEBRA_MESSAGE_MAX                 30
 
 /* Marker value used in new Zserv, in the byte location corresponding
  * the command value in the old zserv header. To allow old and new
@@ -521,6 +524,7 @@ typedef enum {
 #define CHECK_FLAG(V,F)      ((V) & (F))
 #define SET_FLAG(V,F)        (V) |= (F)
 #define UNSET_FLAG(V,F)      (V) &= ~(F)
+#define RESET_FLAG(V)        (V) = 0
 
 typedef u_int8_t safi_t;
 

zebra/Makefile.am

@@ -40,17 +40,18 @@ zebra_SOURCES = \
 	zserv.c main.c interface.c connected.c zebra_rib.c zebra_routemap.c \
 	redistribute.c debug.c rtadv.c zebra_snmp.c zebra_vty.c \
 	irdp_main.c irdp_interface.c irdp_packet.c router-id.c zebra_fpm.c \
+	zebra_rnh.c \
 	$(othersrc) $(protobuf_srcs) $(dev_srcs)
 
 testzebra_SOURCES = test_main.c zebra_rib.c interface.c connected.c debug.c \
 	zebra_vty.c \
-	kernel_null.c  redistribute_null.c ioctl_null.c misc_null.c
+	kernel_null.c  redistribute_null.c ioctl_null.c misc_null.c zebra_rnh_null.c
 
 noinst_HEADERS = \
 	connected.h ioctl.h rib.h rt.h zserv.h redistribute.h debug.h rtadv.h \
 	interface.h ipforward.h irdp.h router-id.h kernel_socket.h \
 	rt_netlink.h zebra_fpm.h zebra_fpm_private.h \
-	ioctl_solaris.h
+	ioctl_solaris.h zebra_rnh.h
 
 zebra_LDADD = $(otherobj) ../lib/libzebra.la $(LIBCAP) $(Q_FPM_PB_CLIENT_LDOPTS)
 

zebra/debug.c

@@ -30,6 +30,7 @@ unsigned long zebra_debug_packet;
 unsigned long zebra_debug_kernel;
 unsigned long zebra_debug_rib;
 unsigned long zebra_debug_fpm;
+unsigned long zebra_debug_nht;
 
 DEFUN (show_debugging_zebra,
        show_debugging_zebra_cmd,
@@ -74,6 +75,8 @@ DEFUN (show_debugging_zebra,
 
   if (IS_ZEBRA_DEBUG_FPM)
     vty_out (vty, "  Zebra FPM debugging is on%s", VTY_NEWLINE);
+  if (IS_ZEBRA_DEBUG_NHT)
+    vty_out (vty, "  Zebra next-hop tracking debugging is on%s", VTY_NEWLINE);
 
   return CMD_SUCCESS;
 }
@@ -89,6 +92,17 @@ DEFUN (debug_zebra_events,
   return CMD_WARNING;
 }
 
+DEFUN (debug_zebra_nht,
+       debug_zebra_nht_cmd,
+       "debug zebra nht",
+       DEBUG_STR
+       "Zebra configuration\n"
+       "Debug option set for zebra next hop tracking\n")
+{
+  zebra_debug_nht = ZEBRA_DEBUG_NHT;
+  return CMD_WARNING;
+}
+
 DEFUN (debug_zebra_packet,
        debug_zebra_packet_cmd,
        "debug zebra packet",
@@ -197,6 +211,18 @@ DEFUN (no_debug_zebra_events,
   return CMD_SUCCESS;
 }
 
+DEFUN (no_debug_zebra_nht,
+       no_debug_zebra_nht_cmd,
+       "no debug zebra nht",
+       NO_STR
+       DEBUG_STR
+       "Zebra configuration\n"
+       "Debug option set for zebra next hop tracking\n")
+{
+  zebra_debug_nht = 0;
+  return CMD_SUCCESS;
+}
+
 DEFUN (no_debug_zebra_packet,
        no_debug_zebra_packet_cmd,
        "no debug zebra packet",
@@ -353,6 +379,7 @@ zebra_debug_init (void)
 
   install_element (ENABLE_NODE, &show_debugging_zebra_cmd);
   install_element (ENABLE_NODE, &debug_zebra_events_cmd);
+  install_element (ENABLE_NODE, &debug_zebra_nht_cmd);
   install_element (ENABLE_NODE, &debug_zebra_packet_cmd);
   install_element (ENABLE_NODE, &debug_zebra_packet_direct_cmd);
   install_element (ENABLE_NODE, &debug_zebra_packet_detail_cmd);
@@ -361,6 +388,7 @@ zebra_debug_init (void)
   install_element (ENABLE_NODE, &debug_zebra_rib_q_cmd);
   install_element (ENABLE_NODE, &debug_zebra_fpm_cmd);
   install_element (ENABLE_NODE, &no_debug_zebra_events_cmd);
+  install_element (ENABLE_NODE, &no_debug_zebra_nht_cmd);
   install_element (ENABLE_NODE, &no_debug_zebra_packet_cmd);
   install_element (ENABLE_NODE, &no_debug_zebra_kernel_cmd);
   install_element (ENABLE_NODE, &no_debug_zebra_rib_cmd);
@@ -368,6 +396,7 @@ zebra_debug_init (void)
   install_element (ENABLE_NODE, &no_debug_zebra_fpm_cmd);
 
   install_element (CONFIG_NODE, &debug_zebra_events_cmd);
+  install_element (CONFIG_NODE, &debug_zebra_nht_cmd);
   install_element (CONFIG_NODE, &debug_zebra_packet_cmd);
   install_element (CONFIG_NODE, &debug_zebra_packet_direct_cmd);
   install_element (CONFIG_NODE, &debug_zebra_packet_detail_cmd);
@@ -376,6 +405,7 @@ zebra_debug_init (void)
   install_element (CONFIG_NODE, &debug_zebra_rib_q_cmd);
   install_element (CONFIG_NODE, &debug_zebra_fpm_cmd);
   install_element (CONFIG_NODE, &no_debug_zebra_events_cmd);
+  install_element (CONFIG_NODE, &no_debug_zebra_nht_cmd);
   install_element (CONFIG_NODE, &no_debug_zebra_packet_cmd);
   install_element (CONFIG_NODE, &no_debug_zebra_kernel_cmd);
   install_element (CONFIG_NODE, &no_debug_zebra_rib_cmd);

zebra/debug.h

@@ -37,6 +37,7 @@
 #define ZEBRA_DEBUG_RIB_Q   0x02
 
 #define ZEBRA_DEBUG_FPM     0x01
+#define ZEBRA_DEBUG_NHT     0x01
 
 /* Debug related macro. */
 #define IS_ZEBRA_DEBUG_EVENT  (zebra_debug_event & ZEBRA_DEBUG_EVENT)
@@ -52,12 +53,14 @@
 #define IS_ZEBRA_DEBUG_RIB_Q  (zebra_debug_rib & ZEBRA_DEBUG_RIB_Q)
 
 #define IS_ZEBRA_DEBUG_FPM (zebra_debug_fpm & ZEBRA_DEBUG_FPM)
+#define IS_ZEBRA_DEBUG_NHT  (zebra_debug_nht & ZEBRA_DEBUG_NHT)
 
 extern unsigned long zebra_debug_event;
 extern unsigned long zebra_debug_packet;
 extern unsigned long zebra_debug_kernel;
 extern unsigned long zebra_debug_rib;
 extern unsigned long zebra_debug_fpm;
+extern unsigned long zebra_debug_nht;
 
 extern void zebra_debug_init (void);
 

zebra/ioctl.c

@@ -196,7 +196,6 @@ if_set_prefix (struct interface *ifp, struct connected *ifc)
   struct prefix_ipv4 *p;
 
   p = (struct prefix_ipv4 *) ifc->address;
-  rib_lookup_and_pushup (p);
 
   memset (&addreq, 0, sizeof addreq);
   strncpy ((char *)&addreq.ifra_name, ifp->name, sizeof addreq.ifra_name);

zebra/rib.h

@@ -27,18 +27,10 @@
 #include "prefix.h"
 #include "table.h"
 #include "queue.h"
+#include "nexthop.h"
 
 #define DISTANCE_INFINITY  255
 
-/* Routing information base. */
-
-union g_addr {
-  struct in_addr ipv4;
-#ifdef HAVE_IPV6
-  struct in6_addr ipv6;
-#endif /* HAVE_IPV6 */
-};
-
 struct rib
 {
   /* Link list. */
@@ -207,50 +199,6 @@ struct static_route
  */
 };
 
-enum nexthop_types_t
-{
-  NEXTHOP_TYPE_IFINDEX = 1,      /* Directly connected.  */
-  NEXTHOP_TYPE_IFNAME,           /* Interface route.  */
-  NEXTHOP_TYPE_IPV4,             /* IPv4 nexthop.  */
-  NEXTHOP_TYPE_IPV4_IFINDEX,     /* IPv4 nexthop with ifindex.  */
-  NEXTHOP_TYPE_IPV4_IFNAME,      /* IPv4 nexthop with ifname.  */
-  NEXTHOP_TYPE_IPV6,             /* IPv6 nexthop.  */
-  NEXTHOP_TYPE_IPV6_IFINDEX,     /* IPv6 nexthop with ifindex.  */
-  NEXTHOP_TYPE_IPV6_IFNAME,      /* IPv6 nexthop with ifname.  */
-  NEXTHOP_TYPE_BLACKHOLE,        /* Null0 nexthop.  */
-};
-
-/* Nexthop structure. */
-struct nexthop
-{
-  struct nexthop *next;
-  struct nexthop *prev;
-
-  /* Interface index. */
-  char *ifname;
-  ifindex_t ifindex;
-  
-  enum nexthop_types_t type;
-
-  u_char flags;
-#define NEXTHOP_FLAG_ACTIVE     (1 << 0) /* This nexthop is alive. */
-#define NEXTHOP_FLAG_FIB        (1 << 1) /* FIB nexthop. */
-#define NEXTHOP_FLAG_RECURSIVE  (1 << 2) /* Recursive nexthop. */
-#define NEXTHOP_FLAG_ONLINK     (1 << 3) /* Nexthop should be installed onlink. */
-
-  /* Nexthop address */
-  union g_addr gate;
-  union g_addr src;
-
-  /* Nexthops obtained by recursive resolution.
-   *
-   * If the nexthop struct needs to be resolved recursively,
-   * NEXTHOP_FLAG_RECURSIVE will be set in flags and the nexthops
-   * obtained by recursive resolution will be added to `resolved'.
-   * Only one level of recursive resolution is currently supported. */
-  struct nexthop *resolved;
-};
-
 /* The following for loop allows to iterate over the nexthop
  * structure of routes.
  *
@@ -370,6 +318,9 @@ struct zebra_vrf
 #if defined (HAVE_RTADV)
   struct rtadv rtadv;
 #endif /* HAVE_RTADV */
+
+  /* Recursive Nexthop table */
+  struct route_table *rnh_table[AFI_MAX];
 };
 
 /*
@@ -425,18 +376,20 @@ extern void multicast_mode_ipv4_set (enum multicast_mode mode);
 extern enum multicast_mode multicast_mode_ipv4_get (void);
 
 extern const char *nexthop_type_to_str (enum nexthop_types_t nh_type);
-extern struct nexthop *nexthop_ifindex_add (struct rib *, ifindex_t);
-extern struct nexthop *nexthop_ifname_add (struct rib *, char *);
-extern struct nexthop *nexthop_blackhole_add (struct rib *);
-extern struct nexthop *nexthop_ipv4_add (struct rib *, struct in_addr *,
-					 struct in_addr *);
-extern struct nexthop *nexthop_ipv4_ifindex_add (struct rib *,
-                                                 struct in_addr *,
-                                                 struct in_addr *,
-                                                 ifindex_t);
+extern struct nexthop *rib_nexthop_ifindex_add (struct rib *, ifindex_t);
+extern struct nexthop *rib_nexthop_ifname_add (struct rib *, char *);
+extern struct nexthop *rib_nexthop_blackhole_add (struct rib *);
+extern struct nexthop *rib_nexthop_ipv4_add (struct rib *, struct in_addr *,
+					     struct in_addr *);
+extern struct nexthop *rib_nexthop_ipv4_ifindex_add (struct rib *,
+						     struct in_addr *,
+						     struct in_addr *,
+						     ifindex_t);
+
+extern void rib_nexthop_add (struct rib *rib, struct nexthop *nexthop);
+
 extern int nexthop_has_fib_child(struct nexthop *);
 extern void rib_lookup_and_dump (struct prefix_ipv4 *);
-extern void rib_lookup_and_pushup (struct prefix_ipv4 *);
 #define rib_dump(prefix ,rib) _rib_dump(__func__, prefix, rib)
 extern void _rib_dump (const char *,
 		       union prefix46constptr, const struct rib *);
@@ -448,11 +401,12 @@ extern int rib_lookup_ipv4_route (struct prefix_ipv4 *, union sockunion *,
 #define ZEBRA_RIB_FOUND_CONNECTED 2
 #define ZEBRA_RIB_NOTFOUND 3
 
-extern struct nexthop *nexthop_ipv6_add (struct rib *, struct in6_addr *);
-extern struct nexthop *nexthop_ipv6_ifindex_add (struct rib *,
-                                                 struct in6_addr *,
-                                                 ifindex_t);
+extern struct nexthop *rib_nexthop_ipv6_add (struct rib *, struct in6_addr *);
+extern struct nexthop *rib_nexthop_ipv6_ifindex_add (struct rib *,
+                                                     struct in6_addr *,
+                                                     ifindex_t);
 
+extern struct zebra_vrf *zebra_vrf_lookup (vrf_id_t vrf_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);

zebra/rt_netlink.c

@@ -38,6 +38,7 @@
 #include "thread.h"
 #include "privs.h"
 #include "vrf.h"
+#include "nexthop.h"
 
 #include "zebra/zserv.h"
 #include "zebra/rt.h"
@@ -851,12 +852,12 @@ netlink_routing_table (struct sockaddr_nl *snl, struct nlmsghdr *h,
               if (gate)
                 {
                   if (index)
-                    nexthop_ipv4_ifindex_add (rib, gate, src, index);
+                    rib_nexthop_ipv4_ifindex_add (rib, gate, src, index);
                   else
-                    nexthop_ipv4_add (rib, gate, src);
+                    rib_nexthop_ipv4_add (rib, gate, src);
                 }
               else
-                nexthop_ifindex_add (rib, index);
+                rib_nexthop_ifindex_add (rib, index);
 
               len -= NLMSG_ALIGN(rtnh->rtnh_len);
               rtnh = RTNH_NEXT(rtnh);
@@ -1065,12 +1066,12 @@ netlink_route_change (struct sockaddr_nl *snl, struct nlmsghdr *h,
                   if (gate)
                     {
                       if (index)
-                        nexthop_ipv4_ifindex_add (rib, gate, src, index);
+                        rib_nexthop_ipv4_ifindex_add (rib, gate, src, index);
                       else
-                        nexthop_ipv4_add (rib, gate, src);
+                        rib_nexthop_ipv4_add (rib, gate, src);
                     }
                   else
-                    nexthop_ifindex_add (rib, index);
+                    rib_nexthop_ifindex_add (rib, index);
 
                   len -= NLMSG_ALIGN(rtnh->rtnh_len);
                   rtnh = RTNH_NEXT(rtnh);

zebra/zebra_fpm_netlink.c

@@ -29,6 +29,7 @@
 #include "rib.h"
 
 #include "rt_netlink.h"
+#include "nexthop.h"
 
 #include "zebra_fpm_private.h"
 

zebra/zebra_rib.c

@@ -35,6 +35,7 @@
 #include "prefix.h"
 #include "routemap.h"
 #include "vrf.h"
+#include "nexthop.h"
 
 #include "zebra/rib.h"
 #include "zebra/rt.h"
@@ -42,6 +43,7 @@
 #include "zebra/redistribute.h"
 #include "zebra/debug.h"
 #include "zebra/zebra_fpm.h"
+#include "zebra/zebra_rnh.h"
 
 /* Default rtm_table for all clients */
 extern struct zebra_t zebrad;
@@ -110,57 +112,17 @@ _rnode_zlog(const char *_func, struct route_node *rn, int priority,
 #define rnode_info(node, ...) \
 	_rnode_zlog(__func__, node, LOG_INFO, __VA_ARGS__)
 
-/*
- * nexthop_type_to_str
- */
-const char *
-nexthop_type_to_str (enum nexthop_types_t nh_type)
-{
-  static const char *desc[] = {
-    "none",
-    "Directly connected",
-    "Interface route",
-    "IPv4 nexthop",
-    "IPv4 nexthop with ifindex",
-    "IPv4 nexthop with ifname",
-    "IPv6 nexthop",
-    "IPv6 nexthop with ifindex",
-    "IPv6 nexthop with ifname",
-    "Null0 nexthop",
-  };
-
-  if (nh_type >= ZEBRA_NUM_OF (desc))
-    return "<Invalid nh type>";
-
-  return desc[nh_type];
-}
-
-/* Add nexthop to the end of a nexthop list.  */
-static void
-_nexthop_add (struct nexthop **target, struct nexthop *nexthop)
-{
-  struct nexthop *last;
-
-  for (last = *target; last && last->next; last = last->next)
-    ;
-  if (last)
-    last->next = nexthop;
-  else
-    *target = nexthop;
-  nexthop->prev = last;
-}
-
 /* Add nexthop to the end of a rib node's nexthop list */
-static void
-nexthop_add (struct rib *rib, struct nexthop *nexthop)
+void
+rib_nexthop_add (struct rib *rib, struct nexthop *nexthop)
 {
-  _nexthop_add(&rib->nexthop, nexthop);
+  nexthop_add(&rib->nexthop, nexthop);
   rib->nexthop_num++;
 }
 
 /* Delete specified nexthop from the list. */
 static void
-nexthop_delete (struct rib *rib, struct nexthop *nexthop)
+rib_nexthop_delete (struct rib *rib, struct nexthop *nexthop)
 {
   if (nexthop->next)
     nexthop->next->prev = nexthop->prev;
@@ -171,150 +133,124 @@ nexthop_delete (struct rib *rib, struct nexthop *nexthop)
   rib->nexthop_num--;
 }
 
-static void nexthops_free(struct nexthop *nexthop);
-
-/* Free nexthop. */
-static void
-nexthop_free (struct nexthop *nexthop)
-{
-  if (nexthop->ifname)
-    XFREE (0, nexthop->ifname);
-  if (nexthop->resolved)
-    nexthops_free(nexthop->resolved);
-  XFREE (MTYPE_NEXTHOP, nexthop);
-}
-
-/* Frees a list of nexthops */
-static void
-nexthops_free (struct nexthop *nexthop)
-{
-  struct nexthop *nh, *next;
-
-  for (nh = nexthop; nh; nh = next)
-    {
-      next = nh->next;
-      nexthop_free (nh);
-    }
-}
-
 struct nexthop *
-nexthop_ifindex_add (struct rib *rib, ifindex_t ifindex)
+rib_nexthop_ifindex_add (struct rib *rib, ifindex_t ifindex)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_IFINDEX;
   nexthop->ifindex = ifindex;
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
 
 struct nexthop *
-nexthop_ifname_add (struct rib *rib, char *ifname)
+rib_nexthop_ifname_add (struct rib *rib, char *ifname)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_IFNAME;
   nexthop->ifname = XSTRDUP (MTYPE_TMP, ifname);
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
 
 struct nexthop *
-nexthop_ipv4_add (struct rib *rib, struct in_addr *ipv4, struct in_addr *src)
+rib_nexthop_ipv4_add (struct rib *rib, struct in_addr *ipv4, struct in_addr *src)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_IPV4;
   nexthop->gate.ipv4 = *ipv4;
   if (src)
     nexthop->src.ipv4 = *src;
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
 
 struct nexthop *
-nexthop_ipv4_ifindex_add (struct rib *rib, struct in_addr *ipv4, 
-                          struct in_addr *src, ifindex_t ifindex)
+rib_nexthop_ipv4_ifindex_add (struct rib *rib, struct in_addr *ipv4, 
+			      struct in_addr *src, ifindex_t ifindex)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_IPV4_IFINDEX;
   nexthop->gate.ipv4 = *ipv4;
   if (src)
     nexthop->src.ipv4 = *src;
   nexthop->ifindex = ifindex;
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
 
 struct nexthop *
-nexthop_ipv6_add (struct rib *rib, struct in6_addr *ipv6)
+rib_nexthop_ipv6_add (struct rib *rib, struct in6_addr *ipv6)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_IPV6;
   nexthop->gate.ipv6 = *ipv6;
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
 
 static struct nexthop *
-nexthop_ipv6_ifname_add (struct rib *rib, struct in6_addr *ipv6,
-			 char *ifname)
+rib_nexthop_ipv6_ifname_add (struct rib *rib, struct in6_addr *ipv6,
+			     char *ifname)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_IPV6_IFNAME;
   nexthop->gate.ipv6 = *ipv6;
   nexthop->ifname = XSTRDUP (MTYPE_TMP, ifname);
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
 
 struct nexthop *
-nexthop_ipv6_ifindex_add (struct rib *rib, struct in6_addr *ipv6,
-			  ifindex_t ifindex)
+rib_nexthop_ipv6_ifindex_add (struct rib *rib, struct in6_addr *ipv6,
+			      ifindex_t ifindex)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_IPV6_IFINDEX;
   nexthop->gate.ipv6 = *ipv6;
   nexthop->ifindex = ifindex;
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
 
 struct nexthop *
-nexthop_blackhole_add (struct rib *rib)
+rib_nexthop_blackhole_add (struct rib *rib)
 {
   struct nexthop *nexthop;
 
-  nexthop = XCALLOC (MTYPE_NEXTHOP, sizeof (struct nexthop));
+  nexthop = nexthop_new ();
   nexthop->type = NEXTHOP_TYPE_BLACKHOLE;
   SET_FLAG (rib->flags, ZEBRA_FLAG_BLACKHOLE);
 
-  nexthop_add (rib, nexthop);
+  rib_nexthop_add (rib, nexthop);
 
   return nexthop;
 }
@@ -455,7 +391,7 @@ nexthop_active_ipv4 (struct rib *rib, struct nexthop *nexthop, int set,
 			    resolved_hop->ifindex = newhop->ifindex;
 			  }
 
-			_nexthop_add(&nexthop->resolved, resolved_hop);
+			nexthop_add(&nexthop->resolved, resolved_hop);
 		      }
 		    resolved = 1;
 		  }
@@ -592,7 +528,7 @@ nexthop_active_ipv6 (struct rib *rib, struct nexthop *nexthop, int set,
 				resolved_hop->ifindex = newhop->ifindex;
 			  }
 
-			_nexthop_add(&nexthop->resolved, resolved_hop);
+			nexthop_add(&nexthop->resolved, resolved_hop);
 		      }
 		    resolved = 1;
 		  }
@@ -1440,6 +1376,18 @@ process_subq (struct list * subq, u_char qindex)
   return 1;
 }
 
+/*
+ * All meta queues have been processed. Trigger next-hop evaluation.
+ */
+static void
+meta_queue_process_complete (struct work_queue *dummy)
+{
+  zebra_evaluate_rnh_table(0, AF_INET);
+#ifdef HAVE_IPV6
+  zebra_evaluate_rnh_table(0, AF_INET6);
+#endif /* HAVE_IPV6 */
+}
+
 /* Dispatch the meta queue by picking, processing and unlocking the next RN from
  * a non-empty sub-queue with lowest priority. wq is equal to zebra->ribq and data
  * is pointed to the meta queue structure.
@@ -1592,6 +1540,7 @@ rib_queue_init (struct zebra_t *zebra)
   /* fill in the work queue spec */
   zebra->ribq->spec.workfunc = &meta_queue_process;
   zebra->ribq->spec.errorfunc = NULL;
+  zebra->ribq->spec.completion_func = &meta_queue_process_complete;
   /* XXX: TODO: These should be runtime configurable via vty */
   zebra->ribq->spec.max_retries = 3;
   zebra->ribq->spec.hold = rib_process_hold_time;
@@ -1815,12 +1764,12 @@ rib_add_ipv4 (int type, int flags, struct prefix_ipv4 *p,
   if (gate)
     {
       if (ifindex)
-	nexthop_ipv4_ifindex_add (rib, gate, src, ifindex);
+	rib_nexthop_ipv4_ifindex_add (rib, gate, src, ifindex);
       else
-	nexthop_ipv4_add (rib, gate, src);
+	rib_nexthop_ipv4_add (rib, gate, src);
     }
   else
-    nexthop_ifindex_add (rib, ifindex);
+    rib_nexthop_ifindex_add (rib, ifindex);
 
   /* If this route is kernel route, set FIB flag to the route. */
   if (type == ZEBRA_ROUTE_KERNEL || type == ZEBRA_ROUTE_CONNECT)