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/*
* net/sched/sch_tbf.c Token Bucket Filter queue.
*
* 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: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
* Dmitry Torokhov <dtor@mail.ru> - allow attaching inner qdiscs -
* original idea by Martin Devera
*
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <net/netlink.h>
#include <net/pkt_sched.h>
/* Simple Token Bucket Filter.
=======================================
SOURCE.
-------
None.
Description.
------------
A data flow obeys TBF with rate R and depth B, if for any
time interval t_i...t_f the number of transmitted bits
does not exceed B + R*(t_f-t_i).
Packetized version of this definition:
The sequence of packets of sizes s_i served at moments t_i
obeys TBF, if for any i<=k:
s_i+....+s_k <= B + R*(t_k - t_i)
Algorithm.
----------
Let N(t_i) be B/R initially and N(t) grow continuously with time as:
N(t+delta) = min{B/R, N(t) + delta}
If the first packet in queue has length S, it may be
transmitted only at the time t_* when S/R <= N(t_*),
and in this case N(t) jumps:
N(t_* + 0) = N(t_* - 0) - S/R.
Actually, QoS requires two TBF to be applied to a data stream.
One of them controls steady state burst size, another
one with rate P (peak rate) and depth M (equal to link MTU)
limits bursts at a smaller time scale.
It is easy to see that P>R, and B>M. If P is infinity, this double
TBF is equivalent to a single one.
When TBF works in reshaping mode, latency is estimated as:
lat = max ((L-B)/R, (L-M)/P)
NOTES.
------
If TBF throttles, it starts a watchdog timer, which will wake it up
when it is ready to transmit.
Note that the minimal timer resolution is 1/HZ.
If no new packets arrive during this period,
or if the device is not awaken by EOI for some previous packet,
TBF can stop its activity for 1/HZ.
This means, that with depth B, the maximal rate is
R_crit = B*HZ
F.e. for 10Mbit ethernet and HZ=100 the minimal allowed B is ~10Kbytes.
Note that the peak rate TBF is much more tough: with MTU 1500
P_crit = 150Kbytes/sec. So, if you need greater peak
rates, use alpha with HZ=1000 :-)
With classful TBF, limit is just kept for backwards compatibility.
It is passed to the default bfifo qdisc - if the inner qdisc is
changed the limit is not effective anymore.
*/
struct tbf_sched_data {
/* Parameters */
u32 limit; /* Maximal length of backlog: bytes */
u32 buffer; /* Token bucket depth/rate: MUST BE >= MTU/B */
u32 mtu;
u32 max_size;
struct qdisc_rate_table *R_tab;
struct qdisc_rate_table *P_tab;
/* Variables */
long tokens; /* Current number of B tokens */
long ptokens; /* Current number of P tokens */
psched_time_t t_c; /* Time check-point */
struct Qdisc *qdisc; /* Inner qdisc, default - bfifo queue */
struct qdisc_watchdog watchdog; /* Watchdog timer */
};
#define L2T(q, L) qdisc_l2t((q)->R_tab, L)
#define L2T_P(q, L) qdisc_l2t((q)->P_tab, L)
static int tbf_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
struct tbf_sched_data *q = qdisc_priv(sch);
int ret;
if (qdisc_pkt_len(skb) > q->max_size)
return qdisc_reshape_fail(skb, sch);
ret = qdisc_enqueue(skb, q->qdisc);
if (ret != NET_XMIT_SUCCESS) {
if (net_xmit_drop_count(ret))
sch->qstats.drops++;
return ret;
}
sch->q.qlen++;
qdisc_bstats_update(sch, skb);
return NET_XMIT_SUCCESS;
}
static unsigned int tbf_drop(struct Qdisc *sch)
{
struct tbf_sched_data *q = qdisc_priv(sch);
unsigned int len = 0;
if (q->qdisc->ops->drop && (len = q->qdisc->ops->drop(q->qdisc)) != 0) {
sch->q.qlen--;
sch->qstats.drops++;
}
return len;
}
static struct sk_buff *tbf_dequeue(struct Qdisc *sch)
{
struct tbf_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb;
skb = q->qdisc->ops->peek(q->qdisc);
if (skb) {
psched_time_t now;
long toks;
long ptoks = 0;
unsigned int len = qdisc_pkt_len(skb);
now = psched_get_time();
toks = psched_tdiff_bounded(now, q->t_c, q->buffer);
if (q->P_tab) {
ptoks = toks + q->ptokens;
if (ptoks > (long)q->mtu)
ptoks = q->mtu;
ptoks -= L2T_P(q, len);
}
toks += q->tokens;
if (toks > (long)q->buffer)
toks = q->buffer;
toks -= L2T(q, len);
if ((toks|ptoks) >= 0) {
skb = qdisc_dequeue_peeked(q->qdisc);
if (unlikely(!skb))
return NULL;
q->t_c = now;
q->tokens = toks;
q->ptokens = ptoks;
sch->q.qlen--;
qdisc_unthrottled(sch);
return skb;
}
qdisc_watchdog_schedule(&q->watchdog,
now + max_t(long, -toks, -ptoks));
/* Maybe we have a shorter packet in the queue,
which can be sent now. It sounds cool,
but, however, this is wrong in principle.
We MUST NOT reorder packets under these circumstances.
Really, if we split the flow into independent
subflows, it would be a very good solution.
This is the main idea of all FQ algorithms
(cf. CSZ, HPFQ, HFSC)
*/
sch->qstats.overlimits++;
}
return NULL;
}
static void tbf_reset(struct Qdisc *sch)
{
struct tbf_sched_data *q = qdisc_priv(sch);
qdisc_reset(q->qdisc);
sch->q.qlen = 0;
q->t_c = psched_get_time();
q->tokens = q->buffer;
q->ptokens = q->mtu;
qdisc_watchdog_cancel(&q->watchdog);
}
static const struct nla_policy tbf_policy[TCA_TBF_MAX + 1] = {
[TCA_TBF_PARMS] = { .len = sizeof(struct tc_tbf_qopt) },
[TCA_TBF_RTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
[TCA_TBF_PTAB] = { .type = NLA_BINARY, .len = TC_RTAB_SIZE },
};
static int tbf_change(struct Qdisc *sch, struct nlattr *opt)
{
int err;
struct tbf_sched_data *q = qdisc_priv(sch);
struct nlattr *tb[TCA_TBF_PTAB + 1];
struct tc_tbf_qopt *qopt;
struct qdisc_rate_table *rtab = NULL;
struct qdisc_rate_table *ptab = NULL;
struct Qdisc *child = NULL;
int max_size, n;
err = nla_parse_nested(tb, TCA_TBF_PTAB, opt, tbf_policy);
if (err < 0)
return err;
err = -EINVAL;
if (tb[TCA_TBF_PARMS] == NULL)
goto done;
qopt = nla_data(tb[TCA_TBF_PARMS]);
rtab = qdisc_get_rtab(&qopt->rate, tb[TCA_TBF_RTAB]);
if (rtab == NULL)
goto done;
if (qopt->peakrate.rate) {
if (qopt->peakrate.rate > qopt->rate.rate)
ptab = qdisc_get_rtab(&qopt->peakrate, tb[TCA_TBF_PTAB]);
if (ptab == NULL)
goto done;
}
for (n = 0; n < 256; n++)
if (rtab->data[n] > qopt->buffer)
break;
max_size = (n << qopt->rate.cell_log) - 1;
if (ptab) {
int size;
for (n = 0; n < 256; n++)
if (ptab->data[n] > qopt->mtu)
break;
size = (n << qopt->peakrate.cell_log) - 1;
if (size < max_size)
max_size = size;
}
if (max_size < 0)
goto done;
if (q->qdisc != &noop_qdisc) {
err = fifo_set_limit(q->qdisc, qopt->limit);
if (err)
goto done;
} else if (qopt->limit > 0) {
child = fifo_create_dflt<
|