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[PATCH] (3/3) netem: allow random reordering

To: "David S. Miller" <davem@xxxxxxxxxxxxx>
Subject: [PATCH] (3/3) netem: allow random reordering
From: Stephen Hemminger <shemminger@xxxxxxxx>
Date: Thu, 19 May 2005 15:12:54 -0700
Cc: netdev@xxxxxxxxxxx, netem@xxxxxxxx
Organization: Open Source Development Lab
Sender: netdev-bounce@xxxxxxxxxxx
Enhance the reorder feature of netem to allow random percent to be reordered.
Has expected backwards compatibility behaviour.

Signed-off-by: Stephen Hemminger <shemminger@xxxxxxxx>

Index: netem-2.6.12-rc4/include/linux/pkt_sched.h
===================================================================
--- netem-2.6.12-rc4.orig/include/linux/pkt_sched.h
+++ netem-2.6.12-rc4/include/linux/pkt_sched.h
@@ -427,6 +427,7 @@ enum
        TCA_NETEM_UNSPEC,
        TCA_NETEM_CORR,
        TCA_NETEM_DELAY_DIST,
+       TCA_NETEM_REORDER,
        __TCA_NETEM_MAX,
 };
 
@@ -437,7 +438,7 @@ struct tc_netem_qopt
        __u32   latency;        /* added delay (us) */
        __u32   limit;          /* fifo limit (packets) */
        __u32   loss;           /* random packet loss (0=none ~0=100%) */
-       __u32   gap;            /* re-ordering gap (0 for delay all) */
+       __u32   gap;            /* re-ordering gap (0 for none) */
        __u32   duplicate;      /* random packet dup  (0=none ~0=100%) */
        __u32   jitter;         /* random jitter in latency (us) */
 };
@@ -449,6 +450,12 @@ struct tc_netem_corr
        __u32   dup_corr;       /* duplicate correlation  */
 };
 
+struct tc_netem_reorder
+{
+       __u32   probability;
+       __u32   correlation;
+};
+
 #define NETEM_DIST_SCALE       8192
 
 #endif
Index: netem-2.6.12-rc4/net/sched/sch_netem.c
===================================================================
--- netem-2.6.12-rc4.orig/net/sched/sch_netem.c
+++ netem-2.6.12-rc4/net/sched/sch_netem.c
@@ -62,11 +62,12 @@ struct netem_sched_data {
        u32 gap;
        u32 jitter;
        u32 duplicate;
+       u32 reorder;
 
        struct crndstate {
                unsigned long last;
                unsigned long rho;
-       } delay_cor, loss_cor, dup_cor;
+       } delay_cor, loss_cor, dup_cor, reorder_cor;
 
        struct disttable {
                u32  size;
@@ -185,18 +186,18 @@ static int netem_enqueue(struct sk_buff 
         * of the queue.
         * gap == 0 is special case for no-reordering.
         */
-       if (q->gap == 0 || q->counter != q->gap) {
+       if (q->gap == 0 && q->counter < q->gap && 
+           q->reorder < get_crandom(&q->reorder_cor)) {
                psched_time_t now;
                PSCHED_GET_TIME(now);
-               PSCHED_TADD2(now, 
-                            tabledist(q->latency, q->jitter, &q->delay_cor, 
q->delay_dist),
+               PSCHED_TADD2(now, tabledist(q->latency, q->jitter, 
+                                           &q->delay_cor, q->delay_dist),
                             cb->time_to_send);
-               
                ++q->counter;
                ret = q->qdisc->enqueue(skb, q->qdisc);
        } else {
-               q->counter = 0;
                PSCHED_GET_TIME(cb->time_to_send);
+               q->counter = 0;
                ret = q->qdisc->ops->requeue(skb, q->qdisc);
        }
 
@@ -351,6 +352,19 @@ static int get_correlation(struct Qdisc 
        return 0;
 }
 
+static int get_reorder(struct Qdisc *sch, const struct rtattr *attr)
+{
+       struct netem_sched_data *q = qdisc_priv(sch);
+       const struct tc_netem_reorder *r = RTA_DATA(attr);
+
+       if (RTA_PAYLOAD(attr) != sizeof(*r))
+               return -EINVAL;
+
+       q->reorder = r->probability;
+       init_crandom(&q->reorder_cor, r->correlation);
+       return 0;
+}
+
 static int netem_change(struct Qdisc *sch, struct rtattr *opt)
 {
        struct netem_sched_data *q = qdisc_priv(sch);
@@ -371,9 +385,15 @@ static int netem_change(struct Qdisc *sc
        q->jitter = qopt->jitter;
        q->limit = qopt->limit;
        q->gap = qopt->gap;
+       q->counter = 0;
        q->loss = qopt->loss;
        q->duplicate = qopt->duplicate;
 
+       /* for compatiablity with earlier versions.
+        * if gap is set, need to assume 100% probablity
+        */
+       q->reorder = ~0;
+
        /* Handle nested options after initial queue options.
         * Should have put all options in nested format but too late now.
         */ 
@@ -395,6 +415,11 @@ static int netem_change(struct Qdisc *sc
                        if (ret)
                                return ret;
                }
+               if (tb[TCA_NETEM_REORDER-1]) {
+                       ret = get_reorder(sch, tb[TCA_NETEM_REORDER-1]);
+                       if (ret)
+                               return ret;
+               }
        }
 
 
@@ -412,7 +437,6 @@ static int netem_init(struct Qdisc *sch,
        init_timer(&q->timer);
        q->timer.function = netem_watchdog;
        q->timer.data = (unsigned long) sch;
-       q->counter = 0;
 
        q->qdisc = qdisc_create_dflt(sch->dev, &pfifo_qdisc_ops);
        if (!q->qdisc) {
@@ -444,6 +468,7 @@ static int netem_dump(struct Qdisc *sch,
        struct rtattr *rta = (struct rtattr *) b;
        struct tc_netem_qopt qopt;
        struct tc_netem_corr cor;
+       struct tc_netem_reorder reorder;
 
        qopt.latency = q->latency;
        qopt.jitter = q->jitter;
@@ -457,6 +482,11 @@ static int netem_dump(struct Qdisc *sch,
        cor.loss_corr = q->loss_cor.rho;
        cor.dup_corr = q->dup_cor.rho;
        RTA_PUT(skb, TCA_NETEM_CORR, sizeof(cor), &cor);
+
+       reorder.probability = q->reorder;
+       reorder.correlation = q->reorder_cor.rho;
+       RTA_PUT(skb, TCA_NETEM_REORDER, sizeof(reorder), &reorder);
+
        rta->rta_len = skb->tail - b;
 
        return skb->len;

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