ovn-nbctl: Monitor nb_cfg to detect and handle potential overflows

ovn-nbctl sync command will increase nb_cfg value each time it is executed
with a specific wait_type, this increment will be handled without testing
the current nb_cfg value because it is not monitored and that could lead
to an overflow issue if nb_cfg == LLONG_MAX.

To avoid such potential overflow cases we must monitor the real value
of nb_cfg each time sync is executed and if there is any overflow issue
it will be handled by function nbctl_pre_execute later on the execution.

Fixes: be3a60f ("ovn-nbctl: Deal with nb_cfg overflows.")
Reported-at: https://bugzilla.redhat.com/show_bug.cgi?id=1979774
Signed-off-by: Mohammad Heib <mheib@redhat.com>
Signed-off-by: Numan Siddique <numans@ovn.org>

AUTHORS.rst

@@ -273,6 +273,7 @@ Miguel Angel Ajo                   majopela@redhat.com
 Mijo Safradin                      mijo@linux.vnet.ibm.com
 Mika Vaisanen                      mika.vaisanen@gmail.com
 Minoru TAKAHASHI                   takahashi.minoru7@gmail.com
+Mohammad Heib                      mheib@redhat.com
 Moshe Levi                         moshele@mellanox.com
 Murphy McCauley                    murphy.mccauley@gmail.com
 Natasha Gude

tests/ovn-controller.at

@@ -392,6 +392,37 @@ OVN_CLEANUP([hv])
 AT_CLEANUP
 ])
 
+# check that nb_cfg overflow cases handled properly
+AT_SETUP([ovn-controller - overflow the nb_cfg value across the tables])
+AT_KEYWORDS([ovn])
+ovn_start
+
+net_add n1
+sim_add hv
+as hv
+ovs-vsctl add-br br-phys
+ovn_attach n1 br-phys 192.168.0.1
+
+check ovn-nbctl --wait=hv sync
+
+# overflow the NB_Global nb_cfg value
+check ovn-nbctl set NB_Global . nb_cfg=9223372036854775806
+
+# nb_cfg must be set to zero if it exceed the value of LLONG_MAX
+# the command below will try incress the value of nb_cfg to be greater than LLONG_MAX and
+# expect zero as a return value
+check ovn-nbctl --wait=hv sync
+check ovn-nbctl --wait=hv sync
+
+# nb_cfg should be set to 1 in the chassis_private/nb_global/sb_global table
+check_column 1 chassis_private nb_cfg
+check_column 1 sb_global nb_cfg
+check_column 1 nb:nb_global nb_cfg
+check_column 0 chassis nb_cfg
+
+OVN_CLEANUP([hv])
+AT_CLEANUP
+
 # Test unix command: debug/delay-nb-cfg-report
 OVN_FOR_EACH_NORTHD([
 AT_SETUP([ovn-controller - debug/delay-nb-cfg-report])

utilities/ovn-nbctl.c

@@ -830,6 +830,8 @@ static void
 nbctl_pre_sync(struct ctl_context *base OVS_UNUSED)
 {
     force_wait = true;
+    /* Monitor nb_cfg to detect and handle potential overflows. */
+    ovsdb_idl_add_column(base->idl, &nbrec_nb_global_col_nb_cfg);
 }
 
 static void