[ovs-dev] [PATCH ovn] ovn-controller: Relax get_nb_cfg() condition seqno check.

Dumitru Ceara dceara at redhat.com
Thu Dec 3 14:49:02 UTC 2020


The IDL might decide to resend pending monitor condition changes
implicitly (one such case is at reconnect) in which case the client
(ovn-controller) might end waiting for a condition seqno that has
already been satisfied.

In order to avoid this case, we now relax the seqno check in
get_nb_cfg() and if the IDL condition seqno is greater or equal than
what ovn-controller expected after changing monitor conditions it means
that there are no in-flight pending changes.

Fixes: 58e5d32b011b ("ovn-controller: Fix nb_cfg update with monitor_cond_change in flight.")
Signed-off-by: Dumitru Ceara <dceara at redhat.com>
---
CI run with tests passing from the first run (no recheck):
https://github.com/dceara/ovn/actions/runs/398575371
---
 controller/ovn-controller.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/controller/ovn-controller.c b/controller/ovn-controller.c
index 46589e4..a9415b2 100644
--- a/controller/ovn-controller.c
+++ b/controller/ovn-controller.c
@@ -824,8 +824,15 @@ get_nb_cfg(const struct sbrec_sb_global_table *sb_global_table,
     /* Delay getting nb_cfg if there are monitor condition changes
      * in flight.  It might be that those changes would instruct the
      * server to send updates that happened before SB_Global.nb_cfg.
+     *
+     * The IDL can decide to resend pending conditions upon reconnect in
+     * which case the expected_cond_seqno is not updated because the client
+     * (ovn-controller) did not explicitly request it.  That means that we
+     * cannot just check for cond_seqno != expected_cond_seqno and we also
+     * have to take into account potential unsigned int overflows.
      */
-    if (cond_seqno != expected_cond_seqno) {
+    if (cond_seqno < expected_cond_seqno &&
+            (cond_seqno != 0 || expected_cond_seqno != UINT_MAX)) {
         return nb_cfg;
     }
 
-- 
1.8.3.1



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