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
19 static 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) <=
23 READ_ONCE(sch->limit)))
24 return qdisc_enqueue_tail(skb, sch);
25
26 return qdisc_drop(skb, sch, to_free);
27 }
28
29 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
30 struct sk_buff **to_free)
31 {
32 if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
33 return qdisc_enqueue_tail(skb, sch);
34
35 return qdisc_drop(skb, sch, to_free);
36 }
37
38 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
39 struct sk_buff **to_free)
40 {
41 unsigned int prev_backlog;
42
43 if (likely(sch->q.qlen < READ_ONCE(sch->limit)))
44 return qdisc_enqueue_tail(skb, sch);
45
46 prev_backlog = sch->qstats.backlog;
47 /* queue full, remove one skb to fulfill the limit */
48 __qdisc_queue_drop_head(sch, &sch->q, to_free);
49 qdisc_qstats_drop(sch);
50 qdisc_enqueue_tail(skb, sch);
51
52 qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
53 return NET_XMIT_CN;
54 }
55
56 static void fifo_offload_init(struct Qdisc *sch)
57 {
58 struct net_device *dev = qdisc_dev(sch);
59 struct tc_fifo_qopt_offload qopt;
60
61 if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
62 return;
63
64 qopt.command = TC_FIFO_REPLACE;
65 qopt.handle = sch->handle;
66 qopt.parent = sch->parent;
67 dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
68 }
69
70 static void fifo_offload_destroy(struct Qdisc *sch)
71 {
72 struct net_device *dev = qdisc_dev(sch);
73 struct tc_fifo_qopt_offload qopt;
74
75 if (!tc_can_offload(dev) || !dev->netdev_ops->ndo_setup_tc)
76 return;
77
78 qopt.command = TC_FIFO_DESTROY;
79 qopt.handle = sch->handle;
80 qopt.parent = sch->parent;
81 dev->netdev_ops->ndo_setup_tc(dev, TC_SETUP_QDISC_FIFO, &qopt);
82 }
83
84 static int fifo_offload_dump(struct Qdisc *sch)
85 {
86 struct tc_fifo_qopt_offload qopt;
87
88 qopt.command = TC_FIFO_STATS;
89 qopt.handle = sch->handle;
90 qopt.parent = sch->parent;
91 qopt.stats.bstats = &sch->bstats;
92 qopt.stats.qstats = &sch->qstats;
93
94 return qdisc_offload_dump_helper(sch, TC_SETUP_QDISC_FIFO, &qopt);
95 }
96
97 static int __fifo_init(struct Qdisc *sch, struct nlattr *opt,
98 struct netlink_ext_ack *extack)
99 {
100 bool bypass;
101 bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
102
103 if (opt == NULL) {
104 u32 limit = qdisc_dev(sch)->tx_queue_len;
105
106 if (is_bfifo)
107 limit *= psched_mtu(qdisc_dev(sch));
108
109 WRITE_ONCE(sch->limit, limit);
110 } else {
111 struct tc_fifo_qopt *ctl = nla_data(opt);
112
113 if (nla_len(opt) < sizeof(*ctl))
114 return -EINVAL;
115
116 WRITE_ONCE(sch->limit, ctl->limit);
117 }
118
119 if (is_bfifo)
120 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
121 else
122 bypass = sch->limit >= 1;
123
124 if (bypass)
125 sch->flags |= TCQ_F_CAN_BYPASS;
126 else
127 sch->flags &= ~TCQ_F_CAN_BYPASS;
128
129 return 0;
130 }
131
132 static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
133 struct netlink_ext_ack *extack)
134 {
135 int err;
136
137 err = __fifo_init(sch, opt, extack);
138 if (err)
139 return err;
140
141 fifo_offload_init(sch);
142 return 0;
143 }
144
145 static int fifo_hd_init(struct Qdisc *sch, struct nlattr *opt,
146 struct netlink_ext_ack *extack)
147 {
148 return __fifo_init(sch, opt, extack);
149 }
150
151 static void fifo_destroy(struct Qdisc *sch)
152 {
153 fifo_offload_destroy(sch);
154 }
155
156 static int __fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
157 {
158 struct tc_fifo_qopt opt = { .limit = READ_ONCE(sch->limit) };
159
160 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
161 goto nla_put_failure;
162 return skb->len;
163
164 nla_put_failure:
165 return -1;
166 }
167
168 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
169 {
170 int err;
171
172 err = fifo_offload_dump(sch);
173 if (err)
174 return err;
175
176 return __fifo_dump(sch, skb);
177 }
178
179 static int fifo_hd_dump(struct Qdisc *sch, struct sk_buff *skb)
180 {
181 return __fifo_dump(sch, skb);
182 }
183
184 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
185 .id = "pfifo",
186 .priv_size = 0,
187 .enqueue = pfifo_enqueue,
188 .dequeue = qdisc_dequeue_head,
189 .peek = qdisc_peek_head,
190 .init = fifo_init,
191 .destroy = fifo_destroy,
192 .reset = qdisc_reset_queue,
193 .change = fifo_init,
194 .dump = fifo_dump,
195 .owner = THIS_MODULE,
196 };
197 EXPORT_SYMBOL(pfifo_qdisc_ops);
198
199 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
200 .id = "bfifo",
201 .priv_size = 0,
202 .enqueue = bfifo_enqueue,
203 .dequeue = qdisc_dequeue_head,
204 .peek = qdisc_peek_head,
205 .init = fifo_init,
206 .destroy = fifo_destroy,
207 .reset = qdisc_reset_queue,
208 .change = fifo_init,
209 .dump = fifo_dump,
210 .owner = THIS_MODULE,
211 };
212 EXPORT_SYMBOL(bfifo_qdisc_ops);
213
214 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
215 .id = "pfifo_head_drop",
216 .priv_size = 0,
217 .enqueue = pfifo_tail_enqueue,
218 .dequeue = qdisc_dequeue_head,
219 .peek = qdisc_peek_head,
220 .init = fifo_hd_init,
221 .reset = qdisc_reset_queue,
222 .change = fifo_hd_init,
223 .dump = fifo_hd_dump,
224 .owner = THIS_MODULE,
225 };
226
227 /* Pass size change message down to embedded FIFO */
228 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
229 {
230 struct nlattr *nla;
231 int ret = -ENOMEM;
232
233 /* Hack to avoid sending change message to non-FIFO */
234 if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
235 return 0;
236
237 if (!q->ops->change)
238 return 0;
239
240 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
241 if (nla) {
242 nla->nla_type = RTM_NEWQDISC;
243 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
244 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
245
246 ret = q->ops->change(q, nla, NULL);
247 kfree(nla);
248 }
249 return ret;
250 }
251 EXPORT_SYMBOL(fifo_set_limit);
252
253 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
254 unsigned int limit,
255 struct netlink_ext_ack *extack)
256 {
257 struct Qdisc *q;
258 int err = -ENOMEM;
259
260 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
261 extack);
262 if (q) {
263 err = fifo_set_limit(q, limit);
264 if (err < 0) {
265 qdisc_put(q);
266 q = NULL;
267 }
268 }
269
270 return q ? : ERR_PTR(err);
271 }
272 EXPORT_SYMBOL(fifo_create_dflt);
273 MODULE_DESCRIPTION("Single queue packet and byte based First In First Out(P/BFIFO) scheduler");
274
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