1 files changed, 293 insertions, 0 deletions
diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c
new file mode 100644
index 000000000000..0e85133c5653
--- /dev/null
+++ b/net/sched/sch_cbs.c
@@ -0,0 +1,293 @@
+/*
+ * net/sched/sch_cbs.c	Credit Based Shaper
+ *
+ *		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:	Vinicius Costa Gomes <vinicius.gomes@intel.com>
+ *
+ */
+
+/* Credit Based Shaper (CBS)
+ * =========================
+ *
+ * This is a simple rate-limiting shaper aimed at TSN applications on
+ * systems with known traffic workloads.
+ *
+ * Its algorithm is defined by the IEEE 802.1Q-2014 Specification,
+ * Section 8.6.8.2, and explained in more detail in the Annex L of the
+ * same specification.
+ *
+ * There are four tunables to be considered:
+ *
+ *	'idleslope': Idleslope is the rate of credits that is
+ *	accumulated (in kilobits per second) when there is at least
+ *	one packet waiting for transmission. Packets are transmitted
+ *	when the current value of credits is equal or greater than
+ *	zero. When there is no packet to be transmitted the amount of
+ *	credits is set to zero. This is the main tunable of the CBS
+ *	algorithm.
+ *
+ *	'sendslope':
+ *	Sendslope is the rate of credits that is depleted (it should be a
+ *	negative number of kilobits per second) when a transmission is
+ *	ocurring. It can be calculated as follows, (IEEE 802.1Q-2014 Section
+ *	8.6.8.2 item g):
+ *
+ *	sendslope = idleslope - port_transmit_rate
+ *
+ *	'hicredit': Hicredit defines the maximum amount of credits (in
+ *	bytes) that can be accumulated. Hicredit depends on the
+ *	characteristics of interfering traffic,
+ *	'max_interference_size' is the maximum size of any burst of
+ *	traffic that can delay the transmission of a frame that is
+ *	available for transmission for this traffic class, (IEEE
+ *	802.1Q-2014 Annex L, Equation L-3):
+ *
+ *	hicredit = max_interference_size * (idleslope / port_transmit_rate)
+ *
+ *	'locredit': Locredit is the minimum amount of credits that can
+ *	be reached. It is a function of the traffic flowing through
+ *	this qdisc (IEEE 802.1Q-2014 Annex L, Equation L-2):
+ *
+ *	locredit = max_frame_size * (sendslope / port_transmit_rate)
+ */
+
+#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/sch_generic.h>
+#include <net/pkt_sched.h>
+
+#define BYTES_PER_KBIT (1000LL / 8)
+
+struct cbs_sched_data {
+	s64 port_rate; /* in bytes/s */
+	s64 last; /* timestamp in ns */
+	s64 credits; /* in bytes */
+	s32 locredit; /* in bytes */
+	s32 hicredit; /* in bytes */
+	s64 sendslope; /* in bytes/s */
+	s64 idleslope; /* in bytes/s */
+	struct qdisc_watchdog watchdog;
+	int (*enqueue)(struct sk_buff *skb, struct Qdisc *sch);
+	struct sk_buff *(*dequeue)(struct Qdisc *sch);
+};
+
+static int cbs_enqueue_soft(struct sk_buff *skb, struct Qdisc *sch)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	if (sch->q.qlen == 0 && q->credits > 0) {
+		/* We need to stop accumulating credits when there's
+		 * no enqueued packets and q->credits is positive.
+		 */
+		q->credits = 0;
+		q->last = ktime_get_ns();
+	}
+
+	return qdisc_enqueue_tail(skb, sch);
+}
+
+static int cbs_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+		       struct sk_buff **to_free)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	return q->enqueue(skb, sch);
+}
+
+/* timediff is in ns, slope is in bytes/s */
+static s64 timediff_to_credits(s64 timediff, s64 slope)
+{
+	return div64_s64(timediff * slope, NSEC_PER_SEC);
+}
+
+static s64 delay_from_credits(s64 credits, s64 slope)
+{
+	if (unlikely(slope == 0))
+		return S64_MAX;
+
+	return div64_s64(-credits * NSEC_PER_SEC, slope);
+}
+
+static s64 credits_from_len(unsigned int len, s64 slope, s64 port_rate)
+{
+	if (unlikely(port_rate == 0))
+		return S64_MAX;
+
+	return div64_s64(len * slope, port_rate);
+}
+
+static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	s64 now = ktime_get_ns();
+	struct sk_buff *skb;
+	s64 credits;
+	int len;
+
+	if (q->credits < 0) {
+		credits = timediff_to_credits(now - q->last, q->idleslope);
+
+		credits = q->credits + credits;
+		q->credits = min_t(s64, credits, q->hicredit);
+
+		if (q->credits < 0) {
+			s64 delay;
+
+			delay = delay_from_credits(q->credits, q->idleslope);
+			qdisc_watchdog_schedule_ns(&q->watchdog, now + delay);
+
+			q->last = now;
+
+			return NULL;
+		}
+	}
+
+	skb = qdisc_dequeue_head(sch);
+	if (!skb)
+		return NULL;
+
+	len = qdisc_pkt_len(skb);
+
+	/* As sendslope is a negative number, this will decrease the
+	 * amount of q->credits.
+	 */
+	credits = credits_from_len(len, q->sendslope, q->port_rate);
+	credits += q->credits;
+
+	q->credits = max_t(s64, credits, q->locredit);
+	q->last = now;
+
+	return skb;
+}
+
+static struct sk_buff *cbs_dequeue(struct Qdisc *sch)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	return q->dequeue(sch);
+}
+
+static const struct nla_policy cbs_policy[TCA_CBS_MAX + 1] = {
+	[TCA_CBS_PARMS]	= { .len = sizeof(struct tc_cbs_qopt) },
+};
+
+static int cbs_change(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+	struct nlattr *tb[TCA_CBS_MAX + 1];
+	struct ethtool_link_ksettings ecmd;
+	struct tc_cbs_qopt *qopt;
+	s64 link_speed;
+	int err;
+
+	err = nla_parse_nested(tb, TCA_CBS_MAX, opt, cbs_policy, NULL);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_CBS_PARMS])
+		return -EINVAL;
+
+	qopt = nla_data(tb[TCA_CBS_PARMS]);
+
+	if (qopt->offload)
+		return -EOPNOTSUPP;
+
+	if (!__ethtool_get_link_ksettings(dev, &ecmd))
+		link_speed = ecmd.base.speed;
+	else
+		link_speed = SPEED_1000;
+
+	q->port_rate = link_speed * 1000 * BYTES_PER_KBIT;
+
+	q->enqueue = cbs_enqueue_soft;
+	q->dequeue = cbs_dequeue_soft;
+
+	q->hicredit = qopt->hicredit;
+	q->locredit = qopt->locredit;
+	q->idleslope = qopt->idleslope * BYTES_PER_KBIT;
+	q->sendslope = qopt->sendslope * BYTES_PER_KBIT;
+
+	return 0;
+}
+
+static int cbs_init(struct Qdisc *sch, struct nlattr *opt)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	if (!opt)
+		return -EINVAL;
+
+	qdisc_watchdog_init(&q->watchdog, sch);
+
+	return cbs_change(sch, opt);
+}
+
+static void cbs_destroy(struct Qdisc *sch)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_cancel(&q->watchdog);
+}
+
+static int cbs_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct tc_cbs_qopt opt = { };
+	struct nlattr *nest;
+
+	nest = nla_nest_start(skb, TCA_OPTIONS);
+	if (!nest)
+		goto nla_put_failure;
+
+	opt.hicredit = q->hicredit;
+	opt.locredit = q->locredit;
+	opt.sendslope = div64_s64(q->sendslope, BYTES_PER_KBIT);
+	opt.idleslope = div64_s64(q->idleslope, BYTES_PER_KBIT);
+	opt.offload = 0;
+
+	if (nla_put(skb, TCA_CBS_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	return nla_nest_end(skb, nest);
+
+nla_put_failure:
+	nla_nest_cancel(skb, nest);
+	return -1;
+}
+
+static struct Qdisc_ops cbs_qdisc_ops __read_mostly = {
+	.id		=	"cbs",
+	.priv_size	=	sizeof(struct cbs_sched_data),
+	.enqueue	=	cbs_enqueue,
+	.dequeue	=	cbs_dequeue,
+	.peek		=	qdisc_peek_dequeued,
+	.init		=	cbs_init,
+	.reset		=	qdisc_reset_queue,
+	.destroy	=	cbs_destroy,
+	.change		=	cbs_change,
+	.dump		=	cbs_dump,
+	.owner		=	THIS_MODULE,
+};
+
+static int __init cbs_module_init(void)
+{
+	return register_qdisc(&cbs_qdisc_ops);
+}
+
+static void __exit cbs_module_exit(void)
+{
+	unregister_qdisc(&cbs_qdisc_ops);
+}
+module_init(cbs_module_init)
+module_exit(cbs_module_exit)
+MODULE_LICENSE("GPL");