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netem: fix classful handling
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Commit 10f6dfc (Revert "sch_netem: Remove classful functionality")
reintroduced classful functionality to netem, but broke basic netem
behavior :

netem uses an t(ime)fifo queue, and store timestamps in skb->cb[]

If qdisc is changed, time constraints are not respected and other qdisc
can destroy skb->cb[] and block netem at dequeue time.

Fix this by always using internal tfifo, and optionally attach a child
qdisc to netem (or a tree of qdiscs)

Example of use :

DEV=eth3
tc qdisc del dev $DEV root
tc qdisc add dev $DEV root handle 30: est 1sec 8sec netem delay 20ms 10ms
tc qdisc add dev $DEV handle 40:0 parent 30:0 tbf \
	burst 20480 limit 20480 mtu 1514 rate 32000bps

qdisc netem 30: root refcnt 18 limit 1000 delay 20.0ms  10.0ms
 Sent 190792 bytes 413 pkt (dropped 0, overlimits 0 requeues 0)
 rate 18416bit 3pps backlog 0b 0p requeues 0
qdisc tbf 40: parent 30: rate 256000bit burst 20Kb/8 mpu 0b lat 0us
 Sent 190792 bytes 413 pkt (dropped 6, overlimits 10 requeues 0)
 backlog 0b 5p requeues 0

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
CC: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Eric Dumazet authored and David S. Miller committed Dec 30, 2011
1 parent 32b293a commit 5061253
Showing 1 changed file with 81 additions and 121 deletions.
202 changes: 81 additions & 121 deletions net/sched/sch_netem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,11 @@
*/

struct netem_sched_data {
/* internal t(ime)fifo qdisc uses sch->q and sch->limit */

/* optional qdisc for classful handling (NULL at netem init) */
struct Qdisc *qdisc;

struct qdisc_watchdog watchdog;

psched_tdiff_t latency;
Expand Down Expand Up @@ -117,7 +121,9 @@ struct netem_sched_data {

};

/* Time stamp put into socket buffer control block */
/* Time stamp put into socket buffer control block
* Only valid when skbs are in our internal t(ime)fifo queue.
*/
struct netem_skb_cb {
psched_time_t time_to_send;
};
Expand Down Expand Up @@ -324,6 +330,31 @@ static psched_time_t packet_len_2_sched_time(unsigned int len, struct netem_sche
return PSCHED_NS2TICKS(ticks);
}

static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
{
struct sk_buff_head *list = &sch->q;
psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
struct sk_buff *skb;

if (likely(skb_queue_len(list) < sch->limit)) {
skb = skb_peek_tail(list);
/* Optimize for add at tail */
if (likely(!skb || tnext >= netem_skb_cb(skb)->time_to_send))
return qdisc_enqueue_tail(nskb, sch);

skb_queue_reverse_walk(list, skb) {
if (tnext >= netem_skb_cb(skb)->time_to_send)
break;
}

__skb_queue_after(list, skb, nskb);
sch->qstats.backlog += qdisc_pkt_len(nskb);
return NET_XMIT_SUCCESS;
}

return qdisc_reshape_fail(nskb, sch);
}

/*
* Insert one skb into qdisc.
* Note: parent depends on return value to account for queue length.
Expand Down Expand Up @@ -399,7 +430,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
now = psched_get_time();

if (q->rate) {
struct sk_buff_head *list = &q->qdisc->q;
struct sk_buff_head *list = &sch->q;

delay += packet_len_2_sched_time(skb->len, q);

Expand All @@ -417,7 +448,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)

cb->time_to_send = now + delay;
++q->counter;
ret = qdisc_enqueue(skb, q->qdisc);
ret = tfifo_enqueue(skb, sch);
} else {
/*
* Do re-ordering by putting one out of N packets at the front
Expand All @@ -426,7 +457,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
cb->time_to_send = psched_get_time();
q->counter = 0;

__skb_queue_head(&q->qdisc->q, skb);
__skb_queue_head(&sch->q, skb);
q->qdisc->qstats.backlog += qdisc_pkt_len(skb);
q->qdisc->qstats.requeues++;
ret = NET_XMIT_SUCCESS;
Expand All @@ -439,19 +470,20 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
}
}

sch->q.qlen++;
return NET_XMIT_SUCCESS;
}

static unsigned int netem_drop(struct Qdisc *sch)
{
struct netem_sched_data *q = qdisc_priv(sch);
unsigned int len = 0;
unsigned int len;

if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
sch->q.qlen--;
len = qdisc_queue_drop(sch);
if (!len && q->qdisc && q->qdisc->ops->drop)
len = q->qdisc->ops->drop(q->qdisc);
if (len)
sch->qstats.drops++;
}

return len;
}

Expand All @@ -463,16 +495,16 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
if (qdisc_is_throttled(sch))
return NULL;

skb = q->qdisc->ops->peek(q->qdisc);
tfifo_dequeue:
skb = qdisc_peek_head(sch);
if (skb) {
const struct netem_skb_cb *cb = netem_skb_cb(skb);
psched_time_t now = psched_get_time();

/* if more time remaining? */
if (cb->time_to_send <= now) {
skb = qdisc_dequeue_peeked(q->qdisc);
if (cb->time_to_send <= psched_get_time()) {
skb = qdisc_dequeue_tail(sch);
if (unlikely(!skb))
return NULL;
goto qdisc_dequeue;

#ifdef CONFIG_NET_CLS_ACT
/*
Expand All @@ -483,24 +515,47 @@ static struct sk_buff *netem_dequeue(struct Qdisc *sch)
skb->tstamp.tv64 = 0;
#endif

sch->q.qlen--;
if (q->qdisc) {
int err = qdisc_enqueue(skb, q->qdisc);

if (unlikely(err != NET_XMIT_SUCCESS)) {
if (net_xmit_drop_count(err)) {
sch->qstats.drops++;
qdisc_tree_decrease_qlen(sch, 1);
}
}
goto tfifo_dequeue;
}
deliver:
qdisc_unthrottled(sch);
qdisc_bstats_update(sch, skb);
return skb;
}

if (q->qdisc) {
skb = q->qdisc->ops->dequeue(q->qdisc);
if (skb)
goto deliver;
}
qdisc_watchdog_schedule(&q->watchdog, cb->time_to_send);
}

qdisc_dequeue:
if (q->qdisc) {
skb = q->qdisc->ops->dequeue(q->qdisc);
if (skb)
goto deliver;
}
return NULL;
}

static void netem_reset(struct Qdisc *sch)
{
struct netem_sched_data *q = qdisc_priv(sch);

qdisc_reset(q->qdisc);
sch->q.qlen = 0;
qdisc_reset_queue(sch);
if (q->qdisc)
qdisc_reset(q->qdisc);
qdisc_watchdog_cancel(&q->watchdog);
}

Expand Down Expand Up @@ -690,11 +745,7 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt)
if (ret < 0)
return ret;

ret = fifo_set_limit(q->qdisc, qopt->limit);
if (ret) {
pr_info("netem: can't set fifo limit\n");
return ret;
}
sch->limit = qopt->limit;

q->latency = qopt->latency;
q->jitter = qopt->jitter;
Expand Down Expand Up @@ -735,88 +786,6 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt)
return ret;
}

/*
* Special case version of FIFO queue for use by netem.
* It queues in order based on timestamps in skb's
*/
struct fifo_sched_data {
u32 limit;
psched_time_t oldest;
};

static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
{
struct fifo_sched_data *q = qdisc_priv(sch);
struct sk_buff_head *list = &sch->q;
psched_time_t tnext = netem_skb_cb(nskb)->time_to_send;
struct sk_buff *skb;

if (likely(skb_queue_len(list) < q->limit)) {
/* Optimize for add at tail */
if (likely(skb_queue_empty(list) || tnext >= q->oldest)) {
q->oldest = tnext;
return qdisc_enqueue_tail(nskb, sch);
}

skb_queue_reverse_walk(list, skb) {
const struct netem_skb_cb *cb = netem_skb_cb(skb);

if (tnext >= cb->time_to_send)
break;
}

__skb_queue_after(list, skb, nskb);

sch->qstats.backlog += qdisc_pkt_len(nskb);

return NET_XMIT_SUCCESS;
}

return qdisc_reshape_fail(nskb, sch);
}

static int tfifo_init(struct Qdisc *sch, struct nlattr *opt)
{
struct fifo_sched_data *q = qdisc_priv(sch);

if (opt) {
struct tc_fifo_qopt *ctl = nla_data(opt);
if (nla_len(opt) < sizeof(*ctl))
return -EINVAL;

q->limit = ctl->limit;
} else
q->limit = max_t(u32, qdisc_dev(sch)->tx_queue_len, 1);

q->oldest = PSCHED_PASTPERFECT;
return 0;
}

static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct fifo_sched_data *q = qdisc_priv(sch);
struct tc_fifo_qopt opt = { .limit = q->limit };

NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
return skb->len;

nla_put_failure:
return -1;
}

static struct Qdisc_ops tfifo_qdisc_ops __read_mostly = {
.id = "tfifo",
.priv_size = sizeof(struct fifo_sched_data),
.enqueue = tfifo_enqueue,
.dequeue = qdisc_dequeue_head,
.peek = qdisc_peek_head,
.drop = qdisc_queue_drop,
.init = tfifo_init,
.reset = qdisc_reset_queue,
.change = tfifo_init,
.dump = tfifo_dump,
};

static int netem_init(struct Qdisc *sch, struct nlattr *opt)
{
struct netem_sched_data *q = qdisc_priv(sch);
Expand All @@ -828,18 +797,9 @@ static int netem_init(struct Qdisc *sch, struct nlattr *opt)
qdisc_watchdog_init(&q->watchdog, sch);

q->loss_model = CLG_RANDOM;
q->qdisc = qdisc_create_dflt(sch->dev_queue, &tfifo_qdisc_ops,
TC_H_MAKE(sch->handle, 1));
if (!q->qdisc) {
pr_notice("netem: qdisc create tfifo qdisc failed\n");
return -ENOMEM;
}

ret = netem_change(sch, opt);
if (ret) {
if (ret)
pr_info("netem: change failed\n");
qdisc_destroy(q->qdisc);
}
return ret;
}

Expand All @@ -848,7 +808,8 @@ static void netem_destroy(struct Qdisc *sch)
struct netem_sched_data *q = qdisc_priv(sch);

qdisc_watchdog_cancel(&q->watchdog);
qdisc_destroy(q->qdisc);
if (q->qdisc)
qdisc_destroy(q->qdisc);
dist_free(q->delay_dist);
}

Expand Down Expand Up @@ -952,7 +913,7 @@ static int netem_dump_class(struct Qdisc *sch, unsigned long cl,
{
struct netem_sched_data *q = qdisc_priv(sch);

if (cl != 1) /* only one class */
if (cl != 1 || !q->qdisc) /* only one class */
return -ENOENT;

tcm->tcm_handle |= TC_H_MIN(1);
Expand All @@ -966,14 +927,13 @@ static int netem_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
{
struct netem_sched_data *q = qdisc_priv(sch);

if (new == NULL)
new = &noop_qdisc;

sch_tree_lock(sch);
*old = q->qdisc;
q->qdisc = new;
qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
qdisc_reset(*old);
if (*old) {
qdisc_tree_decrease_qlen(*old, (*old)->q.qlen);
qdisc_reset(*old);
}
sch_tree_unlock(sch);

return 0;
Expand Down

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