Re: [PATCH] Fixed NetEm's reorder option

The reorder option wasn't working correctly. It would only kick in if
the gap option was set. In that case it would only lower the
probability of reordering packets because of how the if conditional
was stated.

This patch separetes the algorithm for reordering with gap from the
rest, rendering the code more readable and correct.

Signed-off-by: Rafael C. de Almeida <redacted>
---
 net/sched/sch_netem.c |   45 ++++++++++++++++++++++++++++++++-------------
 1 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index c9c649b..477ee09 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c

@@ -206,27 +206,46 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
       }

       cb = (struct netem_skb_cb *)skb->cb;
-       if (q->gap == 0                 /* not doing reordering */
-           || q->counter < q->gap      /* inside last reordering gap */
-           || q->reorder < get_crandom(&q->reorder_cor)) {
+       if (q->gap) {
+               /* The comparison of reorder is here to keep compatibility with
+                * the old behaviour when one had reorder and gap set, maybe it
+                * could be removed.
+                */
+               if (q->counter < q->gap
+                   || q->reorder < get_crandom(&q->reorder_cor)) {
+                       psched_time_t now;
+                       psched_tdiff_t delay;
+
+                       delay = tabledist(q->latency, q->jitter,
+                                         &q->delay_cor, q->delay_dist);
+
+                       now = psched_get_time();
+                       cb->time_to_send = now + delay;
+                       ++q->counter;
+                       ret = q->qdisc->enqueue(skb, q->qdisc);
+               } else {
+                       /*
+                        * Do re-ordering by putting one out of N packets at the front
+                        * of the queue.
+                        */
+                       cb->time_to_send = psched_get_time();
+                       q->counter = 0;
+                       ret = q->qdisc->ops->requeue(skb, q->qdisc);
+               }
+       } else {
               psched_time_t now;
               psched_tdiff_t delay;

-               delay = tabledist(q->latency, q->jitter,
-                                 &q->delay_cor, q->delay_dist);
+               if (!q->reorder || q->reorder < get_crandom(&q->reorder_cor))
+                       delay = tabledist(q->latency, q->jitter,
+                                         &q->delay_cor, q->delay_dist);
+               else
+                       delay = 0;

               now = psched_get_time();
               cb->time_to_send = now + delay;
               ++q->counter;
               ret = q->qdisc->enqueue(skb, q->qdisc);
-       } else {
-               /*
-                * Do re-ordering by putting one out of N packets at the front
-                * of the queue.
-                */
-               cb->time_to_send = psched_get_time();
-               q->counter = 0;
-               ret = q->qdisc->ops->requeue(skb, q->qdisc);
       }

       if (likely(ret == NET_XMIT_SUCCESS)) {
--

1.5.5.GIT