| // 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; |
| |
| 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); |
| q->last = now; |
| |
| 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 != 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"); |