[PATCH] (4/4) add loss option to network delay scheduler

[Stephen Hemminger <shemminger@xxxxxxxx>]

This enhances the network simulation scheduler to do simple random loss.

The loss parameter is a simple 32 bit value such that 0 means no loss, and
0xffffffff is always drop.  I have a new version of the tc command which takes
care of conversion from percent to this value.

Same patch for 2.4 and 2.6

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

diff -Nru a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
--- a/include/linux/pkt_sched.h 2004-06-17 15:26:51 -07:00
+++ b/include/linux/pkt_sched.h 2004-06-17 15:26:51 -07:00
@@ -437,5 +437,6 @@
 {
        __u32   latency;
        __u32   limit;
-};     
+       __u32   loss;
+};
 #endif
diff -Nru a/net/sched/sch_delay.c b/net/sched/sch_delay.c
--- a/net/sched/sch_delay.c     2004-06-17 15:26:51 -07:00
+++ b/net/sched/sch_delay.c     2004-06-17 15:26:51 -07:00
@@ -40,6 +40,7 @@
 struct dly_sched_data {
        u32     latency;
        u32     limit;
+       u32     loss;
        struct timer_list timer;
        struct Qdisc *qdisc;
 };
@@ -58,6 +59,12 @@
        struct dly_skb_cb *cb = (struct dly_skb_cb *)skb->cb;
        int ret;
 
+       /* Random packet drop 0 => none, ~0 => all */
+       if (q->loss >= net_random()) {
+               sch->stats.drops++;
+               return 0;       /* lie about loss so TCP doesn't know */
+       }
+
        PSCHED_GET_TIME(cb->queuetime);
 
        /* Queue to underlying scheduler */
@@ -196,6 +203,7 @@
        } else {
                q->latency = qopt->latency;
                q->limit = qopt->limit;
+               q->loss = qopt->loss;
        }
        return err;
 }
@@ -232,6 +240,7 @@
 
        qopt.latency = q->latency;
        qopt.limit = q->limit;
+       qopt.loss = q->loss;
 
        RTA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);