ofproto: Do not delete datapath flows on exit by default.

Commit e96a5c24e853 ("upcall: Remove datapath flows when setting
n-threads.") caused OVS to delete datapath flows when it exits through
any graceful means.  This is not necessarily desirable, especially when
OVS is being stopped as part of an upgrade.  This commit changes OVS so
that it only removes datapath flows when requested, via "ovs-appctl
exit --cleanup".

Acked-by: Numan Siddique <numans@ovn.org>
Tested-by: Numan Siddique <numans@ovn.org>
Signed-off-by: Ben Pfaff <blp@ovn.org>

2 files changed, 20 insertions, 14 deletions

diff --git a/ofproto/ofproto-dpif-upcall.c b/ofproto/ofproto-dpif-upcall.c
index cff6d4bf3..483cebb52 100644
--- a/ofproto/ofproto-dpif-upcall.c
+++ b/ofproto/ofproto-dpif-upcall.c
@@ -332,7 +332,7 @@ static size_t recv_upcalls(struct handler *);
 static int process_upcall(struct udpif *, struct upcall *,
                           struct ofpbuf *odp_actions, struct flow_wildcards *);
 static void handle_upcalls(struct udpif *, struct upcall *, size_t n_upcalls);
-static void udpif_stop_threads(struct udpif *);
+static void udpif_stop_threads(struct udpif *, bool delete_flows);
 static void udpif_start_threads(struct udpif *, size_t n_handlers,
                                 size_t n_revalidators);
 static void udpif_pause_revalidators(struct udpif *);
@@ -483,7 +483,7 @@ udpif_run(struct udpif *udpif)
 void
 udpif_destroy(struct udpif *udpif)
 {
-    udpif_stop_threads(udpif);
+    udpif_stop_threads(udpif, false);
 
     dpif_register_dp_purge_cb(udpif->dpif, NULL, udpif);
     dpif_register_upcall_cb(udpif->dpif, NULL, udpif);
@@ -504,9 +504,15 @@ udpif_destroy(struct udpif *udpif)
     free(udpif);
 }
 
-/* Stops the handler and revalidator threads. */
+/* Stops the handler and revalidator threads.
+ *
+ * If 'delete_flows' is true, we delete ukeys and delete all flows from the
+ * datapath.  Otherwise, we end up double-counting stats for flows that remain
+ * in the datapath.  If 'delete_flows' is false, we skip this step.  This is
+ * appropriate if OVS is about to exit anyway and it is desirable to let
+ * existing network connections continue being forwarded afterward. */
 static void
-udpif_stop_threads(struct udpif *udpif)
+udpif_stop_threads(struct udpif *udpif, bool delete_flows)
 {
     if (udpif && (udpif->n_handlers != 0 || udpif->n_revalidators != 0)) {
         size_t i;
@@ -526,10 +532,10 @@ udpif_stop_threads(struct udpif *udpif)
         dpif_disable_upcall(udpif->dpif);
         ovsrcu_quiesce_end();
 
-        /* Delete ukeys, and delete all flows from the datapath to prevent
-         * double-counting stats. */
-        for (i = 0; i < udpif->n_revalidators; i++) {
-            revalidator_purge(&udpif->revalidators[i]);
+        if (delete_flows) {
+            for (i = 0; i < udpif->n_revalidators; i++) {
+                revalidator_purge(&udpif->revalidators[i]);
+            }
         }
 
         latch_poll(&udpif->exit_latch);
@@ -627,7 +633,7 @@ udpif_set_threads(struct udpif *udpif, size_t n_handlers_,
 
     if (udpif->n_handlers != n_handlers_
         || udpif->n_revalidators != n_revalidators_) {
-        udpif_stop_threads(udpif);
+        udpif_stop_threads(udpif, true);
     }
 
     if (!udpif->handlers && !udpif->revalidators) {
@@ -681,7 +687,7 @@ udpif_flush(struct udpif *udpif)
     size_t n_handlers_ = udpif->n_handlers;
     size_t n_revalidators_ = udpif->n_revalidators;
 
-    udpif_stop_threads(udpif);
+    udpif_stop_threads(udpif, true);
     dpif_flow_flush(udpif->dpif);
     udpif_start_threads(udpif, n_handlers_, n_revalidators_);
 }
diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
index 08830d837..5d69a4332 100644
--- a/ofproto/ofproto.c
+++ b/ofproto/ofproto.c
@@ -1601,13 +1601,13 @@ ofproto_rule_delete(struct ofproto *ofproto, struct rule *rule)
 }
 
 static void
-ofproto_flush__(struct ofproto *ofproto)
+ofproto_flush__(struct ofproto *ofproto, bool del)
     OVS_EXCLUDED(ofproto_mutex)
 {
     struct oftable *table;
 
     /* This will flush all datapath flows. */
-    if (ofproto->ofproto_class->flush) {
+    if (del && ofproto->ofproto_class->flush) {
         ofproto->ofproto_class->flush(ofproto);
     }
 
@@ -1710,7 +1710,7 @@ ofproto_destroy(struct ofproto *p, bool del)
         return;
     }
 
-    ofproto_flush__(p);
+    ofproto_flush__(p, del);
     HMAP_FOR_EACH_SAFE (ofport, next_ofport, hmap_node, &p->ports) {
         ofport_destroy(ofport, del);
     }
@@ -2288,7 +2288,7 @@ void
 ofproto_flush_flows(struct ofproto *ofproto)
 {
     COVERAGE_INC(ofproto_flush);
-    ofproto_flush__(ofproto);
+    ofproto_flush__(ofproto, false);
     connmgr_flushed(ofproto->connmgr);
 }