ofproto-dpif: Make sure one-packet flows have zero duration.

A Nicira internal build recently failed the "ofproto-dpif - NetFlow flow
expiration" test because of the following difference in output:

     header: v5, seq 0, engine 2,1
    -rec: [...], 1 pkts, 60 bytes, ICMP 8:0, time <moment>
    +rec: [...], 1 pkts, 60 bytes, ICMP 8:0, time <range>

Looking at the actual output, it is:
    rec: 192.168.0.1 > 192.168.0.2, if 1 > 65535, 1 pkts, 60 bytes,
    ICMP 8:0, time 8...9

That is, a one-packet flow was shown to have more than a momentary
duration, which doesn't make sense.

This commit fixes the problem by making sure that creating a facet and then
its initial subfacet only checks the current time once.

Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index 6da74c4..7737800 100644 (file)
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -4257,6 +4257,14 @@ subfacet_create(struct facet *facet, enum odp_key_fitness key_fitness,
 
     if (list_is_empty(&facet->subfacets)) {
         subfacet = &facet->one_subfacet;
+
+        /* This subfacet should conceptually be created, and have its first
+         * packet pass through, at the same time that its facet was created.
+         * If we called time_msec() here, then the subfacet could look
+         * (occasionally) as though it was used some time after the facet was
+         * used.  That can make a one-packet flow look like it has a nonzero
+         * duration, which looks odd in e.g. NetFlow statistics. */
+        subfacet->used = facet->used;
     } else {
         subfacet = subfacet_find__(ofproto, key, key_len, key_hash,
                                    &facet->flow);
@@ -4271,6 +4279,7 @@ subfacet_create(struct facet *facet, enum odp_key_fitness key_fitness,
         }
 
         subfacet = xmalloc(sizeof *subfacet);
+        subfacet->used = time_msec();
     }
 
     hmap_insert(&ofproto->subfacets, &subfacet->hmap_node, key_hash);
@@ -4284,7 +4293,6 @@ subfacet_create(struct facet *facet, enum odp_key_fitness key_fitness,
         subfacet->key = NULL;
         subfacet->key_len = 0;
     }
-    subfacet->used = time_msec();
     subfacet->dp_packet_count = 0;
     subfacet->dp_byte_count = 0;
     subfacet->actions_len = 0;