netflow: Back-out optimization that could lead to infinite loop

Commit 924282 (netflow: Do 64-bit division less often.) attempted to
remove the 64-bit division used to break flow records with large byte
counts into multiple NetFlow records.  The calculation to determine the
number of records was incorrect and should have shifted "byte_delta" by
31 instead of 32.  This commit reverts the change (while keeping commit
f22a24 (netflow: Avoid (theoretically) looping 2**32 times.) ), since
the logic is more straight-forward than the optimized version.

Bug #3813

diff --git a/ofproto/netflow.c b/ofproto/netflow.c
index 4881c5f..d9f52ba 100644 (file)
--- a/ofproto/netflow.c
+++ b/ofproto/netflow.c
@@ -190,8 +190,8 @@ netflow_expire(struct netflow *nf, struct netflow_flow *nf_flow,
          * traffic.  We try to evenly distribute the packet and byte counters,
          * so that the bytes-per-packet lengths don't look wonky across the
          * records. */
-        while (byte_delta > UINT32_MAX) {
-            uint32_t n_recs = byte_delta >> 32;
+        while (byte_delta) {
+            int n_recs = (byte_delta + UINT32_MAX - 1) / UINT32_MAX;
             uint32_t pkt_count = pkt_delta / n_recs;
             uint32_t byte_count = byte_delta / n_recs;
 
@@ -200,9 +200,6 @@ netflow_expire(struct netflow *nf, struct netflow_flow *nf_flow,
             pkt_delta -= pkt_count;
             byte_delta -= byte_count;
         }
-        if (byte_delta > 0) {
-            gen_netflow_rec(nf, nf_flow, expired, pkt_delta, byte_delta);
-        }
     } else {
         /* In 600 seconds, a 10GbE link can theoretically transmit 75 * 10**10
          * == 175 * 2**32 bytes.  The byte counter is bigger than that, so it's