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582 lines
14 KiB
582 lines
14 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* net/sched/sch_cbs.c Credit Based Shaper |
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* |
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* Authors: Vinicius Costa Gomes <[email protected]> |
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*/ |
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|
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/* Credit Based Shaper (CBS) |
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* ========================= |
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* |
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* This is a simple rate-limiting shaper aimed at TSN applications on |
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* systems with known traffic workloads. |
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* |
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* Its algorithm is defined by the IEEE 802.1Q-2014 Specification, |
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* Section 8.6.8.2, and explained in more detail in the Annex L of the |
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* same specification. |
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* |
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* There are four tunables to be considered: |
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* |
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* 'idleslope': Idleslope is the rate of credits that is |
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* accumulated (in kilobits per second) when there is at least |
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* one packet waiting for transmission. Packets are transmitted |
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* when the current value of credits is equal or greater than |
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* zero. When there is no packet to be transmitted the amount of |
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* credits is set to zero. This is the main tunable of the CBS |
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* algorithm. |
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* |
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* 'sendslope': |
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* Sendslope is the rate of credits that is depleted (it should be a |
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* negative number of kilobits per second) when a transmission is |
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* ocurring. It can be calculated as follows, (IEEE 802.1Q-2014 Section |
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* 8.6.8.2 item g): |
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* |
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* sendslope = idleslope - port_transmit_rate |
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* |
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* 'hicredit': Hicredit defines the maximum amount of credits (in |
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* bytes) that can be accumulated. Hicredit depends on the |
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* characteristics of interfering traffic, |
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* 'max_interference_size' is the maximum size of any burst of |
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* traffic that can delay the transmission of a frame that is |
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* available for transmission for this traffic class, (IEEE |
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* 802.1Q-2014 Annex L, Equation L-3): |
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* |
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* hicredit = max_interference_size * (idleslope / port_transmit_rate) |
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* |
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* 'locredit': Locredit is the minimum amount of credits that can |
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* be reached. It is a function of the traffic flowing through |
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* this qdisc (IEEE 802.1Q-2014 Annex L, Equation L-2): |
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* |
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* locredit = max_frame_size * (sendslope / port_transmit_rate) |
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*/ |
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|
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#include <linux/ethtool.h> |
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#include <linux/module.h> |
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#include <linux/types.h> |
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#include <linux/kernel.h> |
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#include <linux/string.h> |
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#include <linux/errno.h> |
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#include <linux/skbuff.h> |
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#include <net/netevent.h> |
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#include <net/netlink.h> |
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#include <net/sch_generic.h> |
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#include <net/pkt_sched.h> |
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|
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static LIST_HEAD(cbs_list); |
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static DEFINE_SPINLOCK(cbs_list_lock); |
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|
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#define BYTES_PER_KBIT (1000LL / 8) |
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|
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struct cbs_sched_data { |
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bool offload; |
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int queue; |
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atomic64_t port_rate; /* in bytes/s */ |
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s64 last; /* timestamp in ns */ |
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s64 credits; /* in bytes */ |
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s32 locredit; /* in bytes */ |
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s32 hicredit; /* in bytes */ |
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s64 sendslope; /* in bytes/s */ |
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s64 idleslope; /* in bytes/s */ |
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struct qdisc_watchdog watchdog; |
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int (*enqueue)(struct sk_buff *skb, struct Qdisc *sch, |
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struct sk_buff **to_free); |
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struct sk_buff *(*dequeue)(struct Qdisc *sch); |
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struct Qdisc *qdisc; |
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struct list_head cbs_list; |
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}; |
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|
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static int cbs_child_enqueue(struct sk_buff *skb, struct Qdisc *sch, |
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struct Qdisc *child, |
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struct sk_buff **to_free) |
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{ |
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unsigned int len = qdisc_pkt_len(skb); |
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int err; |
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|
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err = child->ops->enqueue(skb, child, to_free); |
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if (err != NET_XMIT_SUCCESS) |
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return err; |
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|
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sch->qstats.backlog += len; |
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sch->q.qlen++; |
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|
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return NET_XMIT_SUCCESS; |
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} |
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|
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static int cbs_enqueue_offload(struct sk_buff *skb, struct Qdisc *sch, |
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struct sk_buff **to_free) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct Qdisc *qdisc = q->qdisc; |
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|
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return cbs_child_enqueue(skb, sch, qdisc, to_free); |
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} |
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|
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static int cbs_enqueue_soft(struct sk_buff *skb, struct Qdisc *sch, |
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struct sk_buff **to_free) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct Qdisc *qdisc = q->qdisc; |
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|
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if (sch->q.qlen == 0 && q->credits > 0) { |
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/* We need to stop accumulating credits when there's |
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* no enqueued packets and q->credits is positive. |
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*/ |
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q->credits = 0; |
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q->last = ktime_get_ns(); |
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} |
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|
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return cbs_child_enqueue(skb, sch, qdisc, to_free); |
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} |
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|
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static int cbs_enqueue(struct sk_buff *skb, struct Qdisc *sch, |
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struct sk_buff **to_free) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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|
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return q->enqueue(skb, sch, to_free); |
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} |
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|
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/* timediff is in ns, slope is in bytes/s */ |
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static s64 timediff_to_credits(s64 timediff, s64 slope) |
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{ |
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return div64_s64(timediff * slope, NSEC_PER_SEC); |
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} |
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|
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static s64 delay_from_credits(s64 credits, s64 slope) |
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{ |
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if (unlikely(slope == 0)) |
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return S64_MAX; |
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|
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return div64_s64(-credits * NSEC_PER_SEC, slope); |
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} |
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|
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static s64 credits_from_len(unsigned int len, s64 slope, s64 port_rate) |
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{ |
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if (unlikely(port_rate == 0)) |
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return S64_MAX; |
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|
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return div64_s64(len * slope, port_rate); |
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} |
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|
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static struct sk_buff *cbs_child_dequeue(struct Qdisc *sch, struct Qdisc *child) |
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{ |
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struct sk_buff *skb; |
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|
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skb = child->ops->dequeue(child); |
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if (!skb) |
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return NULL; |
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|
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qdisc_qstats_backlog_dec(sch, skb); |
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qdisc_bstats_update(sch, skb); |
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sch->q.qlen--; |
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|
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return skb; |
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} |
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|
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static struct sk_buff *cbs_dequeue_soft(struct Qdisc *sch) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct Qdisc *qdisc = q->qdisc; |
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s64 now = ktime_get_ns(); |
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struct sk_buff *skb; |
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s64 credits; |
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int len; |
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|
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/* The previous packet is still being sent */ |
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if (now < q->last) { |
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qdisc_watchdog_schedule_ns(&q->watchdog, q->last); |
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return NULL; |
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} |
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if (q->credits < 0) { |
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credits = timediff_to_credits(now - q->last, q->idleslope); |
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|
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credits = q->credits + credits; |
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q->credits = min_t(s64, credits, q->hicredit); |
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|
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if (q->credits < 0) { |
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s64 delay; |
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|
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delay = delay_from_credits(q->credits, q->idleslope); |
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qdisc_watchdog_schedule_ns(&q->watchdog, now + delay); |
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|
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q->last = now; |
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|
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return NULL; |
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} |
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} |
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skb = cbs_child_dequeue(sch, qdisc); |
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if (!skb) |
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return NULL; |
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|
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len = qdisc_pkt_len(skb); |
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|
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/* As sendslope is a negative number, this will decrease the |
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* amount of q->credits. |
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*/ |
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credits = credits_from_len(len, q->sendslope, |
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atomic64_read(&q->port_rate)); |
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credits += q->credits; |
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|
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q->credits = max_t(s64, credits, q->locredit); |
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/* Estimate of the transmission of the last byte of the packet in ns */ |
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if (unlikely(atomic64_read(&q->port_rate) == 0)) |
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q->last = now; |
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else |
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q->last = now + div64_s64(len * NSEC_PER_SEC, |
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atomic64_read(&q->port_rate)); |
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|
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return skb; |
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} |
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|
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static struct sk_buff *cbs_dequeue_offload(struct Qdisc *sch) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct Qdisc *qdisc = q->qdisc; |
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|
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return cbs_child_dequeue(sch, qdisc); |
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} |
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|
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static struct sk_buff *cbs_dequeue(struct Qdisc *sch) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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|
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return q->dequeue(sch); |
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} |
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|
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static const struct nla_policy cbs_policy[TCA_CBS_MAX + 1] = { |
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[TCA_CBS_PARMS] = { .len = sizeof(struct tc_cbs_qopt) }, |
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}; |
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|
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static void cbs_disable_offload(struct net_device *dev, |
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struct cbs_sched_data *q) |
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{ |
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struct tc_cbs_qopt_offload cbs = { }; |
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const struct net_device_ops *ops; |
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int err; |
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|
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if (!q->offload) |
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return; |
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q->enqueue = cbs_enqueue_soft; |
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q->dequeue = cbs_dequeue_soft; |
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|
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ops = dev->netdev_ops; |
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if (!ops->ndo_setup_tc) |
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return; |
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|
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cbs.queue = q->queue; |
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cbs.enable = 0; |
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|
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err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs); |
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if (err < 0) |
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pr_warn("Couldn't disable CBS offload for queue %d\n", |
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cbs.queue); |
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} |
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|
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static int cbs_enable_offload(struct net_device *dev, struct cbs_sched_data *q, |
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const struct tc_cbs_qopt *opt, |
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struct netlink_ext_ack *extack) |
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{ |
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const struct net_device_ops *ops = dev->netdev_ops; |
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struct tc_cbs_qopt_offload cbs = { }; |
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int err; |
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|
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if (!ops->ndo_setup_tc) { |
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NL_SET_ERR_MSG(extack, "Specified device does not support cbs offload"); |
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return -EOPNOTSUPP; |
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} |
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cbs.queue = q->queue; |
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|
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cbs.enable = 1; |
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cbs.hicredit = opt->hicredit; |
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cbs.locredit = opt->locredit; |
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cbs.idleslope = opt->idleslope; |
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cbs.sendslope = opt->sendslope; |
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err = ops->ndo_setup_tc(dev, TC_SETUP_QDISC_CBS, &cbs); |
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if (err < 0) { |
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NL_SET_ERR_MSG(extack, "Specified device failed to setup cbs hardware offload"); |
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return err; |
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} |
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q->enqueue = cbs_enqueue_offload; |
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q->dequeue = cbs_dequeue_offload; |
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|
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return 0; |
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} |
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|
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static void cbs_set_port_rate(struct net_device *dev, struct cbs_sched_data *q) |
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{ |
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struct ethtool_link_ksettings ecmd; |
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int speed = SPEED_10; |
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int port_rate; |
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int err; |
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|
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err = __ethtool_get_link_ksettings(dev, &ecmd); |
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if (err < 0) |
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goto skip; |
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|
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if (ecmd.base.speed && ecmd.base.speed != SPEED_UNKNOWN) |
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speed = ecmd.base.speed; |
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skip: |
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port_rate = speed * 1000 * BYTES_PER_KBIT; |
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|
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atomic64_set(&q->port_rate, port_rate); |
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netdev_dbg(dev, "cbs: set %s's port_rate to: %lld, linkspeed: %d\n", |
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dev->name, (long long)atomic64_read(&q->port_rate), |
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ecmd.base.speed); |
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} |
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|
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static int cbs_dev_notifier(struct notifier_block *nb, unsigned long event, |
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void *ptr) |
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{ |
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struct net_device *dev = netdev_notifier_info_to_dev(ptr); |
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struct cbs_sched_data *q; |
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struct net_device *qdev; |
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bool found = false; |
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|
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ASSERT_RTNL(); |
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|
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if (event != NETDEV_UP && event != NETDEV_CHANGE) |
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return NOTIFY_DONE; |
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|
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spin_lock(&cbs_list_lock); |
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list_for_each_entry(q, &cbs_list, cbs_list) { |
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qdev = qdisc_dev(q->qdisc); |
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if (qdev == dev) { |
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found = true; |
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break; |
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} |
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} |
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spin_unlock(&cbs_list_lock); |
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|
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if (found) |
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cbs_set_port_rate(dev, q); |
|
|
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return NOTIFY_DONE; |
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} |
|
|
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static int cbs_change(struct Qdisc *sch, struct nlattr *opt, |
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struct netlink_ext_ack *extack) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct net_device *dev = qdisc_dev(sch); |
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struct nlattr *tb[TCA_CBS_MAX + 1]; |
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struct tc_cbs_qopt *qopt; |
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int err; |
|
|
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err = nla_parse_nested_deprecated(tb, TCA_CBS_MAX, opt, cbs_policy, |
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extack); |
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if (err < 0) |
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return err; |
|
|
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if (!tb[TCA_CBS_PARMS]) { |
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NL_SET_ERR_MSG(extack, "Missing CBS parameter which are mandatory"); |
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return -EINVAL; |
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} |
|
|
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qopt = nla_data(tb[TCA_CBS_PARMS]); |
|
|
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if (!qopt->offload) { |
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cbs_set_port_rate(dev, q); |
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cbs_disable_offload(dev, q); |
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} else { |
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err = cbs_enable_offload(dev, q, qopt, extack); |
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if (err < 0) |
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return err; |
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} |
|
|
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/* Everything went OK, save the parameters used. */ |
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q->hicredit = qopt->hicredit; |
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q->locredit = qopt->locredit; |
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q->idleslope = qopt->idleslope * BYTES_PER_KBIT; |
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q->sendslope = qopt->sendslope * BYTES_PER_KBIT; |
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q->offload = qopt->offload; |
|
|
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return 0; |
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} |
|
|
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static int cbs_init(struct Qdisc *sch, struct nlattr *opt, |
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struct netlink_ext_ack *extack) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct net_device *dev = qdisc_dev(sch); |
|
|
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if (!opt) { |
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NL_SET_ERR_MSG(extack, "Missing CBS qdisc options which are mandatory"); |
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return -EINVAL; |
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} |
|
|
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q->qdisc = qdisc_create_dflt(sch->dev_queue, &pfifo_qdisc_ops, |
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sch->handle, extack); |
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if (!q->qdisc) |
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return -ENOMEM; |
|
|
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spin_lock(&cbs_list_lock); |
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list_add(&q->cbs_list, &cbs_list); |
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spin_unlock(&cbs_list_lock); |
|
|
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qdisc_hash_add(q->qdisc, false); |
|
|
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q->queue = sch->dev_queue - netdev_get_tx_queue(dev, 0); |
|
|
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q->enqueue = cbs_enqueue_soft; |
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q->dequeue = cbs_dequeue_soft; |
|
|
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qdisc_watchdog_init(&q->watchdog, sch); |
|
|
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return cbs_change(sch, opt, extack); |
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} |
|
|
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static void cbs_destroy(struct Qdisc *sch) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct net_device *dev = qdisc_dev(sch); |
|
|
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/* Nothing to do if we couldn't create the underlying qdisc */ |
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if (!q->qdisc) |
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return; |
|
|
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qdisc_watchdog_cancel(&q->watchdog); |
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cbs_disable_offload(dev, q); |
|
|
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spin_lock(&cbs_list_lock); |
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list_del(&q->cbs_list); |
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spin_unlock(&cbs_list_lock); |
|
|
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qdisc_put(q->qdisc); |
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} |
|
|
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static int cbs_dump(struct Qdisc *sch, struct sk_buff *skb) |
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{ |
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struct cbs_sched_data *q = qdisc_priv(sch); |
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struct tc_cbs_qopt opt = { }; |
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struct nlattr *nest; |
|
|
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nest = nla_nest_start_noflag(skb, TCA_OPTIONS); |
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if (!nest) |
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goto nla_put_failure; |
|
|
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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; |
|
|
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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); |
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return -1; |
|
} |
|
|
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static int cbs_dump_class(struct Qdisc *sch, unsigned long cl, |
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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, |
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.leaf = cbs_leaf, |
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.find = cbs_find, |
|
.walk = cbs_walk, |
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.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, |
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.peek = qdisc_peek_dequeued, |
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.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; |
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} |
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static void __exit cbs_module_exit(void) |
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{ |
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unregister_qdisc(&cbs_qdisc_ops); |
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unregister_netdevice_notifier(&cbs_device_notifier); |
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} |
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module_init(cbs_module_init) |
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module_exit(cbs_module_exit) |
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MODULE_LICENSE("GPL");
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