1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * net/sched/sch_fifo.c	The simplest FIFO queue.
4 *
5 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
6 */
7
8#include <linux/module.h>
9#include <linux/slab.h>
10#include <linux/types.h>
11#include <linux/kernel.h>
12#include <linux/errno.h>
13#include <linux/skbuff.h>
14#include <net/pkt_sched.h>
15#include <net/pkt_cls.h>
16
17/* 1 band FIFO pseudo-"scheduler" */
18
19static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
20			 struct sk_buff **to_free)
21{
22	if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
23		return qdisc_enqueue_tail(skb, sch);
24
25	return qdisc_drop(skb, sch, to_free);
26}
27
28static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
29			 struct sk_buff **to_free)
30{
31	if (likely(sch->q.qlen < sch->limit))
32		return qdisc_enqueue_tail(skb, sch);
33
34	return qdisc_drop(skb, sch, to_free);
35}
36
37static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
38			      struct sk_buff **to_free)
39{
40	unsigned int prev_backlog;
41
42	if (likely(sch->q.qlen < sch->limit))
43		return qdisc_enqueue_tail(skb, sch);
44
45	prev_backlog = sch->qstats.backlog;
46	/* queue full, remove one skb to fulfill the limit */
47	__qdisc_queue_drop_head(sch, &sch->q, to_free);
48	qdisc_qstats_drop(sch);
49	qdisc_enqueue_tail(skb, sch);
50
51	qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
52	return NET_XMIT_CN;
53}
54
55static void fifo_offload_init(struct Qdisc *sch)
56{
57	struct net_device *dev = qdisc_dev(sch);
58	struct tc_fifo_qopt_offload qopt;
59
60	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
61		return;
62
63	qopt.command = TC_FIFO_REPLACE;
64	qopt.handle = sch->handle;
65	qopt.parent = sch->parent;
66	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
67}
68
69static void fifo_offload_destroy(struct Qdisc *sch)
70{
71	struct net_device *dev = qdisc_dev(sch);
72	struct tc_fifo_qopt_offload qopt;
73
74	if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
75		return;
76
77	qopt.command = TC_FIFO_DESTROY;
78	qopt.handle = sch->handle;
79	qopt.parent = sch->parent;
80	dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
81}
82
83static int fifo_offload_dump(struct Qdisc *sch)
84{
85	struct tc_fifo_qopt_offload qopt;
86
87	qopt.command = TC_FIFO_STATS;
88	qopt.handle = sch->handle;
89	qopt.parent = sch->parent;
90	qopt.stats.bstats = &sch->bstats;
91	qopt.stats.qstats = &sch->qstats;
92
93	return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_FIFO, &qopt);
94}
95
96static int __fifo_init(struct Qdisc *sch, struct nlattr *opt,
97		       struct netlink_ext_ack *extack)
98{
99	bool bypass;
100	bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
101
102	if (opt == NULL) {
103		u32 limit = qdisc_dev(sch)->tx_queue_len;
104
105		if (is_bfifo)
106			limit *= psched_mtu(qdisc_dev(sch));
107
108		sch->limit = limit;
109	} else {
110		struct tc_fifo_qopt *ctl = nla_data(opt);
111
112		if (nla_len(opt) < sizeof(*ctl))
113			return -EINVAL;
114
115		sch->limit = ctl->limit;
116	}
117
118	if (is_bfifo)
119		bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
120	else
121		bypass = sch->limit >= 1;
122
123	if (bypass)
124		sch->flags |= TCQ_F_CAN_BYPASS;
125	else
126		sch->flags &= ~TCQ_F_CAN_BYPASS;
127
128	return 0;
129}
130
131static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
132		     struct netlink_ext_ack *extack)
133{
134	int err;
135
136	err = __fifo_init(sch, opt, extack);
137	if (err)
138		return err;
139
140	fifo_offload_init(sch);
141	return 0;
142}
143
144static int fifo_hd_init(struct Qdisc *sch, struct nlattr *opt,
145			struct netlink_ext_ack *extack)
146{
147	return __fifo_init(sch, opt, extack);
148}
149
150static void fifo_destroy(struct Qdisc *sch)
151{
152	fifo_offload_destroy(sch);
153}
154
155static int __fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
156{
157	struct tc_fifo_qopt opt = { .limit = sch->limit };
158
159	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
160		goto nla_put_failure;
161	return skb->len;
162
163nla_put_failure:
164	return -1;
165}
166
167static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
168{
169	int err;
170
171	err = fifo_offload_dump(sch);
172	if (err)
173		return err;
174
175	return __fifo_dump(sch, skb);
176}
177
178static int fifo_hd_dump(struct Qdisc *sch, struct sk_buff *skb)
179{
180	return __fifo_dump(sch, skb);
181}
182
183struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
184	.id		=	"pfifo",
185	.priv_size	=	0,
186	.enqueue	=	pfifo_enqueue,
187	.dequeue	=	qdisc_dequeue_head,
188	.peek		=	qdisc_peek_head,
189	.init		=	fifo_init,
190	.destroy	=	fifo_destroy,
191	.reset		=	qdisc_reset_queue,
192	.change		=	fifo_init,
193	.dump		=	fifo_dump,
194	.owner		=	THIS_MODULE,
195};
196EXPORT_SYMBOL(pfifo_qdisc_ops);
197
198struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
199	.id		=	"bfifo",
200	.priv_size	=	0,
201	.enqueue	=	bfifo_enqueue,
202	.dequeue	=	qdisc_dequeue_head,
203	.peek		=	qdisc_peek_head,
204	.init		=	fifo_init,
205	.destroy	=	fifo_destroy,
206	.reset		=	qdisc_reset_queue,
207	.change		=	fifo_init,
208	.dump		=	fifo_dump,
209	.owner		=	THIS_MODULE,
210};
211EXPORT_SYMBOL(bfifo_qdisc_ops);
212
213struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
214	.id		=	"pfifo_head_drop",
215	.priv_size	=	0,
216	.enqueue	=	pfifo_tail_enqueue,
217	.dequeue	=	qdisc_dequeue_head,
218	.peek		=	qdisc_peek_head,
219	.init		=	fifo_hd_init,
220	.reset		=	qdisc_reset_queue,
221	.change		=	fifo_hd_init,
222	.dump		=	fifo_hd_dump,
223	.owner		=	THIS_MODULE,
224};
225
226/* Pass size change message down to embedded FIFO */
227int fifo_set_limit(struct Qdisc *q, unsigned int limit)
228{
229	struct nlattr *nla;
230	int ret = -ENOMEM;
231
232	/* Hack to avoid sending change message to non-FIFO */
233	if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
234		return 0;
235
236	if (!q->ops->change)
237		return 0;
238
239	nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
240	if (nla) {
241		nla->nla_type = RTM_NEWQDISC;
242		nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
243		((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
244
245		ret = q->ops->change(q, nla, NULL);
246		kfree(nla);
247	}
248	return ret;
249}
250EXPORT_SYMBOL(fifo_set_limit);
251
252struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
253			       unsigned int limit,
254			       struct netlink_ext_ack *extack)
255{
256	struct Qdisc *q;
257	int err = -ENOMEM;
258
259	q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
260			      extack);
261	if (q) {
262		err = fifo_set_limit(q, limit);
263		if (err < 0) {
264			qdisc_put(q);
265			q = NULL;
266		}
267	}
268
269	return q ? : ERR_PTR(err);
270}
271EXPORT_SYMBOL(fifo_create_dflt);
272MODULE_DESCRIPTION("Single queue packet and byte based First In First Out(P/BFIFO) scheduler");
273