/* * 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 * */ /* 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 #define BYTES_PER_KBIT (1000LL / 8) struct cbs_sched_data { bool offload; int queue; 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_offload(struct sk_buff *skb, struct Qdisc *sch) { return qdisc_enqueue_tail(skb, 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_offload(struct Qdisc *sch) { return qdisc_dequeue_head(sch); } 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) { const struct net_device_ops *ops = dev->netdev_ops; struct tc_cbs_qopt_offload cbs = { }; int err; if (!ops->ndo_setup_tc) 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) return err; q->enqueue = cbs_enqueue_offload; q->dequeue = cbs_dequeue_offload; return 0; } 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 tc_cbs_qopt *qopt; 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) { struct ethtool_link_ksettings ecmd; s64 link_speed; 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; cbs_disable_offload(dev, q); } else { err = cbs_enable_offload(dev, q, qopt); 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) return -EINVAL; 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); } static void cbs_destroy(struct Qdisc *sch) { struct cbs_sched_data *q = qdisc_priv(sch); struct net_device *dev = qdisc_dev(sch); qdisc_watchdog_cancel(&q->watchdog); cbs_disable_offload(dev, q); } 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 = 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 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");