[ovs-dev] [patch v1] conntrack: Fix minimum connections to clean.

[Darrell Ball]

If there is low maximum connection count configuration and less than 10
connections in a bucket, the calculation of the maximum number of
connections to clean for the bucket could be zero, leading to these
connections not being cleaned until and if the connection count in the
bucket increases.

Fix this by checking for low maximum connection count configuration
and do this outside of the buckets loop, thereby simplifying the loop.

Fixes: e6ef6cc6349b ("conntrack: Periodically delete expired connections.")
CC: Daniele Di Proietto <diproiettod at ovn.org>
Reported-by: Liujiaxin <liujiaxin.2019 at bytedance.com>
Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-March/357703.html
Signed-off-by: Darrell Ball <dlu998 at gmail.com>
---

Backport to 2.6.

 lib/conntrack.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/conntrack.c b/lib/conntrack.c
index 9c2abd1..2368fe8 100644
--- a/lib/conntrack.c
+++ b/lib/conntrack.c
@@ -1489,6 +1489,8 @@ conntrack_clean(struct conntrack *ct, long long now)
     size_t clean_count = 0;
 
     atomic_read_relaxed(&ct->n_conn_limit, &n_conn_limit);
+    size_t clean_min = n_conn_limit > CONNTRACK_BUCKETS * 10
+        ? n_conn_limit / (CONNTRACK_BUCKETS * 10) : 1;
 
     for (unsigned i = 0; i < CONNTRACK_BUCKETS; i++) {
         struct conntrack_bucket *ctb = &ct->buckets[i];
@@ -1506,8 +1508,7 @@ conntrack_clean(struct conntrack *ct, long long now)
          * limit to 10% of the global limit equally split among buckets. If
          * the bucket is busier than the others, we limit to 10% of its
          * current size. */
-        min_exp = sweep_bucket(ct, ctb, now,
-                MAX(prev_count/10, n_conn_limit/(CONNTRACK_BUCKETS*10)));
+        min_exp = sweep_bucket(ct, ctb, now, MAX(prev_count / 10, clean_min));
         clean_count += prev_count - hmap_count(&ctb->connections);
 
         if (min_exp > now) {
-- 
1.9.1