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[PATCH] packet delay scheduler

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: [PATCH] packet delay scheduler
From: Stephen Hemminger <shemminger@xxxxxxxx>
Date: Thu, 18 Mar 2004 12:04:51 -0800
Cc: netdev@xxxxxxxxxxx, lartc@xxxxxxxxxxxxxxx
In-reply-to: <20040316174134.2f1da12a.davem@xxxxxxxxxx>
Organization: Open Source Development Lab
References: <20040316151058.3cc2fa28@xxxxxxxxxxxxxxxxxxxxx> <20040316174134.2f1da12a.davem@xxxxxxxxxx>
Sender: netdev-bounce@xxxxxxxxxxx
Okay, here is a very simple QOS scheduler that delays packets for 2.6.
It is good for testing, and might be useful for people who want to put
some class of traffic into a "penalty box".

Alexey's tc command is really easy to extend to new disciplines.  There is
a version which knows about this scheduler at:
        http://developer.osdl.org/shemminger/tcp/iproute2-delay.tar.bz2
The only changes were to tc/Makefile and new file tc/q_delay.c

A trivial example is:
         tc qdisc add dev eth0 root delay latency 25ms rate 100mbit

Try it, if others find it useful please consider adding it.

diff -Nru a/include/linux/pkt_sched.h b/include/linux/pkt_sched.h
--- a/include/linux/pkt_sched.h Thu Mar 18 12:04:02 2004
+++ b/include/linux/pkt_sched.h Thu Mar 18 12:04:02 2004
@@ -432,4 +432,10 @@
 
 #define TCA_ATM_MAX    TCA_ATM_STATE
 
+/* Delay section */
+struct tc_dly_qopt
+{
+       __u32   latency;
+       __u32   limit;
+};     
 #endif
diff -Nru a/net/sched/Kconfig b/net/sched/Kconfig
--- a/net/sched/Kconfig Thu Mar 18 12:04:02 2004
+++ b/net/sched/Kconfig Thu Mar 18 12:04:02 2004
@@ -164,6 +164,17 @@
          To compile this code as a module, choose M here: the
          module will be called sch_dsmark.
 
+config NET_SCH_DELAY
+       tristate "Delay simulator"
+       depends on NET_SCHED
+       help
+         Say Y if you want to delay packets by a fixed amount of
+         time. This is often useful to simulate network delay when
+         testing applications or protocols.
+
+         To compile this driver as a module, choose M here: the module
+         will be called sch_delay.
+
 config NET_SCH_INGRESS
        tristate "Ingress Qdisc"
        depends on NET_SCHED && NETFILTER
diff -Nru a/net/sched/Makefile b/net/sched/Makefile
--- a/net/sched/Makefile        Thu Mar 18 12:04:02 2004
+++ b/net/sched/Makefile        Thu Mar 18 12:04:02 2004
@@ -22,6 +22,7 @@
 obj-$(CONFIG_NET_SCH_TEQL)     += sch_teql.o
 obj-$(CONFIG_NET_SCH_PRIO)     += sch_prio.o
 obj-$(CONFIG_NET_SCH_ATM)      += sch_atm.o
+obj-$(CONFIG_NET_SCH_DELAY)    += sch_delay.o
 obj-$(CONFIG_NET_CLS_U32)      += cls_u32.o
 obj-$(CONFIG_NET_CLS_ROUTE4)   += cls_route.o
 obj-$(CONFIG_NET_CLS_FW)       += cls_fw.o
diff -Nru a/net/sched/sch_delay.c b/net/sched/sch_delay.c
--- /dev/null   Wed Dec 31 16:00:00 1969
+++ b/net/sched/sch_delay.c     Thu Mar 18 12:04:02 2004
@@ -0,0 +1,269 @@
+/*
+ * net/sched/sch_delay.c       Simple constant delay
+ *
+ *             This program is free software; you can redistribute it and/or
+ *             modify it under the terms of the GNU General Public License
+ *             as published by the Free Software Foundation; either version
+ *             2 of the License, or (at your option) any later version.
+ *
+ * Authors:    Stephen Hemminger <shemminger@xxxxxxxx>
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/socket.h>
+#include <linux/sockios.h>
+#include <linux/in.h>
+#include <linux/errno.h>
+#include <linux/interrupt.h>
+#include <linux/if_ether.h>
+#include <linux/inet.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/notifier.h>
+#include <net/ip.h>
+#include <net/route.h>
+#include <linux/skbuff.h>
+#include <net/sock.h>
+#include <net/pkt_sched.h>
+
+/*     Network delay simulator
+       This scheduler adds a fixed delay to all packets.
+       Similar to NISTnet and BSD Dummynet.
+
+       It uses byte fifo underneath similar to TBF */
+struct dly_sched_data {
+       u32     latency;
+       u32     limit;
+       struct timer_list timer;
+       struct Qdisc *qdisc;
+};
+
+/* Time stamp put into socket buffer control block */
+struct dly_skb_cb {
+       psched_time_t   queuetime;
+};
+
+/* Enqueue packets with underlying discipline (fifo)
+ * but mark them with current time first.
+ */
+static int dly_enqueue(struct sk_buff *skb, struct Qdisc *sch)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+       struct dly_skb_cb *cb = (struct dly_skb_cb *)skb->cb;
+       int ret;
+
+       PSCHED_GET_TIME(cb->queuetime);
+
+       /* Queue to underlying scheduler */
+       ret = q->qdisc->enqueue(skb, q->qdisc);
+       if (ret)
+               sch->stats.drops++;
+       else {
+               sch->q.qlen++;
+               sch->stats.bytes += skb->len;
+               sch->stats.packets++;
+       }
+       return 0;
+}
+
+/* Requeue packets but don't change time stamp */
+static int dly_requeue(struct sk_buff *skb, struct Qdisc *sch)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+       int ret;
+
+       ret = q->qdisc->ops->requeue(skb, q->qdisc);
+       if (ret == 0)
+               sch->q.qlen++;
+       return ret;
+}
+
+static unsigned int dly_drop(struct Qdisc *sch)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+       unsigned int len;
+
+       len = q->qdisc->ops->drop(q->qdisc);
+       if (len) {
+               sch->q.qlen--;
+               sch->stats.drops++;
+       }
+       return len;
+}
+
+/* Dequeue packet.
+ * If packet needs to be held up, then stop the
+ * queue and set timer to wakeup later.
+ */
+static struct sk_buff *dly_dequeue(struct Qdisc *sch)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+       struct sk_buff *skb = q->qdisc->dequeue(q->qdisc);
+
+       if (skb) {
+               struct dly_skb_cb *cb = (struct dly_skb_cb *)skb->cb;
+               psched_time_t now;
+               long diff;
+
+               PSCHED_GET_TIME(now);
+               diff = q->latency - PSCHED_TDIFF(now, cb->queuetime);
+
+               if (diff <= 0) {
+                       sch->q.qlen--;
+                       sch->flags &= ~TCQ_F_THROTTLED;
+                       return skb;
+               }
+
+               if (!netif_queue_stopped(sch->dev)) {
+                       long delay = PSCHED_US2JIFFIE(diff);
+                       if (delay <= 0)
+                               delay = 1;
+                       mod_timer(&q->timer, jiffies+delay);
+               }
+
+               if (q->qdisc->ops->requeue(skb, q->qdisc) != NET_XMIT_SUCCESS) {
+                       sch->q.qlen--;
+                       sch->stats.drops++;
+               }
+               sch->flags |= TCQ_F_THROTTLED;
+       }
+       return NULL;
+}
+
+static void dly_reset(struct Qdisc *sch)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+
+       qdisc_reset(q->qdisc);
+       sch->q.qlen = 0;
+       sch->flags &= ~TCQ_F_THROTTLED;
+       del_timer(&q->timer);
+}
+
+static void dly_timer(unsigned long arg)
+{
+       struct Qdisc *sch = (struct Qdisc *)arg;
+
+       sch->flags &= ~TCQ_F_THROTTLED;
+       netif_schedule(sch->dev);
+}
+
+/* Tell Fifo the new limit. */
+static int change_limit(struct Qdisc *q, u32 limit)
+{
+       struct rtattr *rta;
+       int ret;
+
+       rta = kmalloc(RTA_LENGTH(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
+       if (!rta)
+               return -ENOMEM;
+
+       rta->rta_type = RTM_NEWQDISC;
+       ((struct tc_fifo_qopt *)RTA_DATA(rta))->limit = limit;
+       ret = q->ops->change(q, rta);
+       kfree(rta);
+
+       return ret;
+}
+
+/* Setup underlying FIFO discipline */
+static int dly_change(struct Qdisc *sch, struct rtattr *opt)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+       struct tc_dly_qopt *qopt = RTA_DATA(opt);
+       int err;
+
+       if (q->qdisc == &noop_qdisc) {
+               struct Qdisc *child
+                       = qdisc_create_dflt(sch->dev, &bfifo_qdisc_ops);
+               if (!child)
+                       return -EINVAL;
+               q->qdisc = child;
+       }
+
+       err = change_limit(q->qdisc, qopt->limit);
+       if (err) {
+               qdisc_destroy(q->qdisc);
+               q->qdisc = &noop_qdisc;
+       } else {
+               q->latency = qopt->latency;
+               q->limit = qopt->limit;
+       }
+       return err;
+}
+
+static int dly_init(struct Qdisc *sch, struct rtattr *opt)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+
+       if (!opt)
+               return -EINVAL;
+
+       init_timer(&q->timer);
+       q->timer.function = dly_timer;
+       q->timer.data = (unsigned long) sch;
+       q->qdisc = &noop_qdisc;
+
+       return dly_change(sch, opt);
+}
+
+static void dly_destroy(struct Qdisc *sch)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+
+       del_timer(&q->timer);
+       qdisc_destroy(q->qdisc);
+       q->qdisc = &noop_qdisc;
+}
+
+static int dly_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+       struct dly_sched_data *q = (struct dly_sched_data *)sch->data;
+       unsigned char    *b = skb->tail;
+       struct tc_dly_qopt qopt;
+
+       qopt.latency = q->latency;
+       qopt.limit = q->limit;
+
+       RTA_PUT(skb, TCA_OPTIONS, sizeof(qopt), &qopt);
+
+       return skb->len;
+
+rtattr_failure:
+       skb_trim(skb, b - skb->data);
+       return -1;
+}
+
+static struct Qdisc_ops dly_qdisc_ops = {
+       .id             =       "delay",
+       .priv_size      =       sizeof(struct dly_sched_data),
+       .enqueue        =       dly_enqueue,
+       .dequeue        =       dly_dequeue,
+       .requeue        =       dly_requeue,
+       .drop           =       dly_drop,
+       .init           =       dly_init,
+       .reset          =       dly_reset,
+       .destroy        =       dly_destroy,
+       .change         =       dly_change,
+       .dump           =       dly_dump,
+       .owner          =       THIS_MODULE,
+};
+
+
+static int __init dly_module_init(void)
+{
+       return register_qdisc(&dly_qdisc_ops);
+}
+static void __exit dly_module_exit(void)
+{
+       unregister_qdisc(&dly_qdisc_ops);
+}
+module_init(dly_module_init)
+module_exit(dly_module_exit)
+MODULE_LICENSE("GPL");

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