bgpd: bgpd-update-delay.patch

COMMAND:

'update-delay <max-delay in seconds> [<establish-wait in seconds>]'

DESCRIPTION:

This feature is used to enable read-only mode on BGP process restart or when
BGP process is cleared using 'clear ip bgp *'. When applicable, read-only mode
would begin as soon as the first peer reaches Established state and a timer
for <max-delay> seconds is started.

During this mode BGP doesn't run any best-path or generate any updates to its
peers. This mode continues until:

1. All the configured peers, except the shutdown peers, have sent explicit EOR
(End-Of-RIB) or an implicit-EOR. The first keep-alive after BGP has reached
Established is considered an implicit-EOR.
   If the <establish-wait> optional value is given, then BGP will wait for
   peers to reach establish from the begining of the update-delay till the
   establish-wait period is over, i.e. the minimum set of established peers for
   which EOR is expected would be peers established during the establish-wait
   window, not necessarily all the configured neighbors.
2. max-delay period is over.

On hitting any of the above two conditions, BGP resumes the decision process
and generates updates to its peers.

Default <max-delay> is 0, i.e. the feature is off by default.

This feature can be useful in reducing CPU/network used as BGP restarts/clears.
Particularly useful in the topologies where BGP learns a prefix from many peers.
Intermediate bestpaths are possible for the same prefix as peers get established
and start receiving updates at different times. This feature should offer a
value-add if the network has a high number of such prefixes.

IMPLEMENTATION OBJECTIVES:

Given this is an optional feature, minimized the code-churn. Used existing
constructs wherever possible (existing queue-plug/unplug were used to achieve
delay and resume of best-paths/update-generation). As a result, no new
data-structure(s) had to be defined and allocated. When the feature is disabled,
the new node is not exercised for the most part.

Signed-off-by: Vipin Kumar <vipin@cumulusnetworks.com>
Reviewed-by: Pradosh Mohapatra <pmohapat@cumulusnetworks.com>
             Dinesh Dutt <ddutt@cumulusnetworks.com>

1 files changed, 17 insertions, 4 deletions

diff --git a/bgpd/bgp_route.c b/bgpd/bgp_route.c
index 6397c5509..15c3b6eab 100644
--- a/bgpd/bgp_route.c
+++ b/bgpd/bgp_route.c
@@ -1664,7 +1664,7 @@ bgp_processq_del (struct work_queue *wq, void *data)
   XFREE (MTYPE_BGP_PROCESS_QUEUE, pq);
 }
 
-static void
+void
 bgp_process_queue_init (void)
 {
   bm->process_main_queue
@@ -2605,9 +2605,19 @@ bgp_announce_table (struct peer *peer, afi_t afi, safi_t safi,
   if (! table)
     table = (rsclient) ? peer->rib[afi][safi] : peer->bgp->rib[afi][safi];
 
-  if (safi != SAFI_MPLS_VPN
-      && CHECK_FLAG (peer->af_flags[afi][safi], PEER_FLAG_DEFAULT_ORIGINATE))
-    bgp_default_originate (peer, afi, safi, 0);
+  if (safi != SAFI_MPLS_VPN)
+    {
+      if (CHECK_FLAG (peer->af_flags[afi][safi], PEER_FLAG_DEFAULT_ORIGINATE))
+        {
+          bgp_default_originate (peer, afi, safi, 0);
+        }
+      else
+        {
+          /* Send the withdraw if it was postponed during read-only mode. */
+          if (CHECK_FLAG (peer->af_flags[afi][safi], PEER_STATUS_DEFAULT_ORIGINATE))
+            bgp_default_originate (peer, afi, safi, 1);
+        }
+    }
 
   /* It's initialized in bgp_announce_[check|check_rsclient]() */
   attr.extra = &extra;
@@ -2659,6 +2669,9 @@ bgp_announce_route_all (struct peer *peer)
   afi_t afi;
   safi_t safi;
   
+  if (bgp_update_delay_active(peer->bgp))
+    return;
+
   for (afi = AFI_IP; afi < AFI_MAX; afi++)
     for (safi = SAFI_UNICAST; safi < SAFI_MAX; safi++)
       bgp_announce_route (peer, afi, safi);