// SPDX-License-Identifier: GPL-2.0-or-later /* * net/sched/sch_cbs.c Credit Based Shaper * * Authors: Vinicius Costa Gomes */ /* 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 #include #include #include #include #include #include #include #include #include #include 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) { tc_qdisc_stats_dump(sch, 1, walker); } } 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"); MODULE_DESCRIPTION("Credit Based shaper");