1 files changed, 581 insertions, 0 deletions
diff --git a/net/sched/sch_cbs.c b/net/sched/sch_cbs.c
new file mode 100644
index 000000000..2eaac2ff3
--- /dev/null
+++ b/net/sched/sch_cbs.c
@@ -0,0 +1,581 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * net/sched/sch_cbs.c	Credit Based Shaper
+ *
+ * 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/netevent.h>
+#include <net/netlink.h>
+#include <net/sch_generic.h>
+#include <net/pkt_sched.h>
+
+static LIST_HEAD(cbs_list);
+static DEFINE_SPINLOCK(cbs_list_lock);
+
+#define BYTES_PER_KBIT (1000LL / 8)
+
+struct cbs_sched_data {
+	bool offload;
+	int queue;
+	atomic64_t 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 **to_free);
+	struct sk_buff *(*dequeue)(struct Qdisc *sch);
+	struct Qdisc *qdisc;
+	struct list_head cbs_list;
+};
+
+static int cbs_child_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+			     struct Qdisc *child,
+			     struct sk_buff **to_free)
+{
+	unsigned int len = qdisc_pkt_len(skb);
+	int err;
+
+	err = child->ops->enqueue(skb, child, to_free);
+	if (err != NET_XMIT_SUCCESS)
+		return err;
+
+	sch->qstats.backlog += len;
+	sch->q.qlen++;
+
+	return NET_XMIT_SUCCESS;
+}
+
+static int cbs_enqueue_offload(struct sk_buff *skb, struct Qdisc *sch,
+			       struct sk_buff **to_free)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct Qdisc *qdisc = q->qdisc;
+
+	return cbs_child_enqueue(skb, sch, qdisc, to_free);
+}
+
+static int cbs_enqueue_soft(struct sk_buff *skb, struct Qdisc *sch,
+			    struct sk_buff **to_free)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct Qdisc *qdisc = q->qdisc;
+
+	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 cbs_child_enqueue(skb, sch, qdisc, to_free);
+}
+
+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, to_free);
+}
+
+/* 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_child_dequeue(struct Qdisc *sch, struct Qdisc *child)
+{
+	struct sk_buff *skb;
+
+	skb = child->ops->dequeue(child);
+	if (!skb)
+		return NULL;
+
+	qdisc_qstats_backlog_dec(sch, skb);
+	qdisc_bstats_update(sch, skb);
+	sch->q.qlen--;
+
+	return skb;
+}
+
+static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct Qdisc *qdisc = q->qdisc;
+	s64 now = ktime_get_ns();
+	struct sk_buff *skb;
+	s64 credits;
+	int len;
+
+	/* The previous packet is still being sent */
+	if (now < q->last) {
+		qdisc_watchdog_schedule_ns(&q->watchdog, q->last);
+		return NULL;
+	}
+	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 = cbs_child_dequeue(sch, qdisc);
+	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,
+				   atomic64_read(&q->port_rate));
+	credits += q->credits;
+
+	q->credits = max_t(s64, credits, q->locredit);
+	/* Estimate of the transmission of the last byte of the packet in ns */
+	if (unlikely(atomic64_read(&q->port_rate) == 0))
+		q->last = now;
+	else
+		q->last = now + div64_s64(len * NSEC_PER_SEC,
+					  atomic64_read(&q->port_rate));
+
+	return skb;
+}
+
+static struct sk_buff *cbs_dequeue_offload(struct Qdisc *sch)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct Qdisc *qdisc = q->qdisc;
+
+	return cbs_child_dequeue(sch, qdisc);
+}
+
+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 void cbs_disable_offload(struct net_device *dev,
+				struct cbs_sched_data *q)
+{
+	struct tc_cbs_qopt_offload cbs = { };
+	const struct net_device_ops *ops;
+	int err;
+
+	if (!q->offload)
+		return;
+
+	q->enqueue = cbs_enqueue_soft;
+	q->dequeue = cbs_dequeue_soft;
+
+	ops = dev->netdev_ops;
+	if (!ops->ndo_setup_tc)
+		return;
+
+	cbs.queue = q->queue;
+	cbs.enable = 0;
+
+	err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs);
+	if (err < 0)
+		pr_warn("Couldn't disable CBS offload for queue %d\n",
+			cbs.queue);
+}
+
+static int cbs_enable_offload(struct net_device *dev, struct cbs_sched_data *q,
+			      const struct tc_cbs_qopt *opt,
+			      struct netlink_ext_ack *extack)
+{
+	const struct net_device_ops *ops = dev->netdev_ops;
+	struct tc_cbs_qopt_offload cbs = { };
+	int err;
+
+	if (!ops->ndo_setup_tc) {
+		NL_SET_ERR_MSG(extack, "Specified device does not support cbs offload");
+		return -EOPNOTSUPP;
+	}
+
+	cbs.queue = q->queue;
+
+	cbs.enable = 1;
+	cbs.hicredit = opt->hicredit;
+	cbs.locredit = opt->locredit;
+	cbs.idleslope = opt->idleslope;
+	cbs.sendslope = opt->sendslope;
+
+	err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs);
+	if (err < 0) {
+		NL_SET_ERR_MSG(extack, "Specified device failed to setup cbs hardware offload");
+		return err;
+	}
+
+	q->enqueue = cbs_enqueue_offload;
+	q->dequeue = cbs_dequeue_offload;
+
+	return 0;
+}
+
+static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q)
+{
+	struct ethtool_link_ksettings ecmd;
+	int speed = SPEED_10;
+	int port_rate;
+	int err;
+
+	err = __ethtool_get_link_ksettings(dev, &ecmd);
+	if (err < 0)
+		goto skip;
+
+	if (ecmd.base.speed && ecmd.base.speed != SPEED_UNKNOWN)
+		speed = ecmd.base.speed;
+
+skip:
+	port_rate = speed * 1000 * BYTES_PER_KBIT;
+
+	atomic64_set(&q->port_rate, port_rate);
+	netdev_dbg(dev, "cbs: set %s's port_rate to: %lld, linkspeed: %d\n",
+		   dev->name, (long long)atomic64_read(&q->port_rate),
+		   ecmd.base.speed);
+}
+
+static int cbs_dev_notifier(struct notifier_block *nb, unsigned long event,
+			    void *ptr)
+{
+	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
+	struct cbs_sched_data *q;
+	struct net_device *qdev;
+	bool found = false;
+
+	ASSERT_RTNL();
+
+	if (event != NETDEV_UP && event != NETDEV_CHANGE)
+		return NOTIFY_DONE;
+
+	spin_lock(&cbs_list_lock);
+	list_for_each_entry(q, &cbs_list, cbs_list) {
+		qdev = qdisc_dev(q->qdisc);
+		if (qdev == dev) {
+			found = true;
+			break;
+		}
+	}
+	spin_unlock(&cbs_list_lock);
+
+	if (found)
+		cbs_set_port_rate(dev, q);
+
+	return NOTIFY_DONE;
+}
+
+static int cbs_change(struct Qdisc *sch, struct nlattr *opt,
+		      struct netlink_ext_ack *extack)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+	struct nlattr *tb[TCA_CBS_MAX + 1];
+	struct tc_cbs_qopt *qopt;
+	int err;
+
+	err = nla_parse_nested_deprecated(tb, TCA_CBS_MAX, opt, cbs_policy,
+					  extack);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_CBS_PARMS]) {
+		NL_SET_ERR_MSG(extack, "Missing CBS parameter which are mandatory");
+		return -EINVAL;
+	}
+
+	qopt = nla_data(tb[TCA_CBS_PARMS]);
+
+	if (!qopt->offload) {
+		cbs_set_port_rate(dev, q);
+		cbs_disable_offload(dev, q);
+	} else {
+		err = cbs_enable_offload(dev, q, qopt, extack);
+		if (err < 0)
+			return err;
+	}
+
+	/* Everything went OK, save the parameters used. */
+	q->hicredit = qopt->hicredit;
+	q->locredit = qopt->locredit;
+	q->idleslope = qopt->idleslope * BYTES_PER_KBIT;
+	q->sendslope = qopt->sendslope * BYTES_PER_KBIT;
+	q->offload = qopt->offload;
+
+	return 0;
+}
+
+static int cbs_init(struct Qdisc *sch, struct nlattr *opt,
+		    struct netlink_ext_ack *extack)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+
+	if (!opt) {
+		NL_SET_ERR_MSG(extack, "Missing CBS qdisc options  which are mandatory");
+		return -EINVAL;
+	}
+
+	q->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
+				     sch->handle, extack);
+	if (!q->qdisc)
+		return -ENOMEM;
+
+	spin_lock(&cbs_list_lock);
+	list_add(&q->cbs_list, &cbs_list);
+	spin_unlock(&cbs_list_lock);
+
+	qdisc_hash_add(q->qdisc, false);
+
+	q->queue = sch->dev_queue - netdev_get_tx_queue(dev, 0);
+
+	q->enqueue = cbs_enqueue_soft;
+	q->dequeue = cbs_dequeue_soft;
+
+	qdisc_watchdog_init(&q->watchdog, sch);
+
+	return cbs_change(sch, opt, extack);
+}
+
+static void cbs_destroy(struct Qdisc *sch)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+	struct net_device *dev = qdisc_dev(sch);
+
+	/* Nothing to do if we couldn't create the underlying qdisc */
+	if (!q->qdisc)
+		return;
+
+	qdisc_watchdog_cancel(&q->watchdog);
+	cbs_disable_offload(dev, q);
+
+	spin_lock(&cbs_list_lock);
+	list_del(&q->cbs_list);
+	spin_unlock(&cbs_list_lock);
+
+	qdisc_put(q->qdisc);
+}
+
+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_noflag(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 = q->offload;
+
+	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 int cbs_dump_class(struct Qdisc *sch, unsigned long cl,
+			  struct sk_buff *skb, struct tcmsg *tcm)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	if (cl != 1 || !q->qdisc)	/* only one class */
+		return -ENOENT;
+
+	tcm->tcm_handle |= TC_H_MIN(1);
+	tcm->tcm_info = q->qdisc->handle;
+
+	return 0;
+}
+
+static int cbs_graft(struct Qdisc *sch, unsigned long arg, struct Qdisc *new,
+		     struct Qdisc **old, struct netlink_ext_ack *extack)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	if (!new) {
+		new = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops,
+					sch->handle, NULL);
+		if (!new)
+			new = &noop_qdisc;
+	}
+
+	*old = qdisc_replace(sch, new, &q->qdisc);
+	return 0;
+}
+
+static struct Qdisc *cbs_leaf(struct Qdisc *sch, unsigned long arg)
+{
+	struct cbs_sched_data *q = qdisc_priv(sch);
+
+	return q->qdisc;
+}
+
+static unsigned long cbs_find(struct Qdisc *sch, u32 classid)
+{
+	return 1;
+}
+
+static void cbs_walk(struct Qdisc *sch, struct qdisc_walker *walker)
+{
+	if (!walker->stop) {
+		if (walker->count >= walker->skip) {
+			if (walker->fn(sch, 1, walker) < 0) {
+				walker->stop = 1;
+				return;
+			}
+		}
+		walker->count++;
+	}
+}
+
+static const struct Qdisc_class_ops cbs_class_ops = {
+	.graft		=	cbs_graft,
+	.leaf		=	cbs_leaf,
+	.find		=	cbs_find,
+	.walk		=	cbs_walk,
+	.dump		=	cbs_dump_class,
+};
+
+static struct Qdisc_ops cbs_qdisc_ops __read_mostly = {
+	.id		=	"cbs",
+	.cl_ops		=	&cbs_class_ops,
+	.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 struct notifier_block cbs_device_notifier = {
+	.notifier_call = cbs_dev_notifier,
+};
+
+static int __init cbs_module_init(void)
+{
+	int err;
+
+	err = register_netdevice_notifier(&cbs_device_notifier);
+	if (err)
+		return err;
+
+	err = register_qdisc(&cbs_qdisc_ops);
+	if (err)
+		unregister_netdevice_notifier(&cbs_device_notifier);
+
+	return err;
+}
+
+static void __exit cbs_module_exit(void)
+{
+	unregister_qdisc(&cbs_qdisc_ops);
+	unregister_netdevice_notifier(&cbs_device_notifier);
+}
+module_init(cbs_module_init)
+module_exit(cbs_module_exit)
+MODULE_LICENSE("GPL");