summaryrefslogtreecommitdiffstats
path: root/net/sched/sch_skbprio.c
blob: 20ff7386b74bd89c00b50a8f0def91b6c5cce7f4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * net/sched/sch_skbprio.c  SKB Priority Queue.
 *
 * Authors:	Nishanth Devarajan, <ndev2021@gmail.com>
 *		Cody Doucette, <doucette@bu.edu>
 *	        original idea by Michel Machado, Cody Doucette, and Qiaobin Fu
 */

#include <linux/string.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/skbuff.h>
#include <net/pkt_sched.h>
#include <net/sch_generic.h>
#include <net/inet_ecn.h>

/*		SKB Priority Queue
 *	=================================
 *
 * Skbprio (SKB Priority Queue) is a queueing discipline that prioritizes
 * packets according to their skb->priority field. Under congestion,
 * Skbprio drops already-enqueued lower priority packets to make space
 * available for higher priority packets; it was conceived as a solution
 * for denial-of-service defenses that need to route packets with different
 * priorities as a mean to overcome DoS attacks.
 */

struct skbprio_sched_data {
	/* Queue state. */
	struct sk_buff_head qdiscs[SKBPRIO_MAX_PRIORITY];
	struct gnet_stats_queue qstats[SKBPRIO_MAX_PRIORITY];
	u16 highest_prio;
	u16 lowest_prio;
};

static u16 calc_new_high_prio(const struct skbprio_sched_data *q)
{
	int prio;

	for (prio = q->highest_prio - 1; prio >= q->lowest_prio; prio--) {
		if (!skb_queue_empty(&q->qdiscs[prio]))
			return prio;
	}

	/* SKB queue is empty, return 0 (default highest priority setting). */
	return 0;
}

static u16 calc_new_low_prio(const struct skbprio_sched_data *q)
{
	int prio;

	for (prio = q->lowest_prio + 1; prio <= q->highest_prio; prio++) {
		if (!skb_queue_empty(&q->qdiscs[prio]))
			return prio;
	}

	/* SKB queue is empty, return SKBPRIO_MAX_PRIORITY - 1
	 * (default lowest priority setting).
	 */
	return SKBPRIO_MAX_PRIORITY - 1;
}

static int skbprio_enqueue(struct sk_buff *skb, struct Qdisc *sch,
			  struct sk_buff **to_free)
{
	const unsigned int max_priority = SKBPRIO_MAX_PRIORITY - 1;
	struct skbprio_sched_data *q = qdisc_priv(sch);
	struct sk_buff_head *qdisc;
	struct sk_buff_head *lp_qdisc;
	struct sk_buff *to_drop;
	u16 prio, lp;

	/* Obtain the priority of @skb. */
	prio = min(skb->priority, max_priority);

	qdisc = &q->qdiscs[prio];

	/* sch->limit can change under us from skbprio_change() */
	if (sch->q.qlen < READ_ONCE(sch->limit)) {
		__skb_queue_tail(qdisc, skb);
		qdisc_qstats_backlog_inc(sch, skb);
		q->qstats[prio].backlog += qdisc_pkt_len(skb);

		/* Check to update highest and lowest priorities. */
		if (prio > q->highest_prio)
			q->highest_prio = prio;

		if (prio < q->lowest_prio)
			q->lowest_prio = prio;

		sch->q.qlen++;
		return NET_XMIT_SUCCESS;
	}

	/* If this packet has the lowest priority, drop it. */
	lp = q->lowest_prio;
	if (prio <= lp) {
		q->qstats[prio].drops++;
		q->qstats[prio].overlimits++;
		return qdisc_drop(skb, sch, to_free);
	}

	__skb_queue_tail(qdisc, skb);
	qdisc_qstats_backlog_inc(sch, skb);
	q->qstats[prio].backlog += qdisc_pkt_len(skb);

	/* Drop the packet at the tail of the lowest priority qdisc. */
	lp_qdisc = &q->qdiscs[lp];
	to_drop = __skb_dequeue_tail(lp_qdisc);
	BUG_ON(!to_drop);
	qdisc_qstats_backlog_dec(sch, to_drop);
	qdisc_drop(to_drop, sch, to_free);

	q->qstats[lp].backlog -= qdisc_pkt_len(to_drop);
	q->qstats[lp].drops++;
	q->qstats[lp].overlimits++;

	/* Check to update highest and lowest priorities. */
	if (skb_queue_empty(lp_qdisc)) {
		if (q->lowest_prio == q->highest_prio) {
			/* The incoming packet is the only packet in queue. */
			BUG_ON(sch->q.qlen != 1);
			q->lowest_prio = prio;
			q->highest_prio = prio;
		} else {
			q->lowest_prio = calc_new_low_prio(q);
		}
	}

	if (prio > q->highest_prio)
		q->highest_prio = prio;

	return NET_XMIT_CN;
}

static struct sk_buff *skbprio_dequeue(struct Qdisc *sch)
{
	struct skbprio_sched_data *q = qdisc_priv(sch);
	struct sk_buff_head *hpq = &q->qdiscs[q->highest_prio];
	struct sk_buff *skb = __skb_dequeue(hpq);

	if (unlikely(!skb))
		return NULL;

	sch->q.qlen--;
	qdisc_qstats_backlog_dec(sch, skb);
	qdisc_bstats_update(sch, skb);

	q->qstats[q->highest_prio].backlog -= qdisc_pkt_len(skb);

	/* Update highest priority field. */
	if (skb_queue_empty(hpq)) {
		if (q->lowest_prio == q->highest_prio) {
			BUG_ON(sch->q.qlen);
			q->highest_prio = 0;
			q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
		} else {
			q->highest_prio = calc_new_high_prio(q);
		}
	}
	return skb;
}

static int skbprio_change(struct Qdisc *sch, struct nlattr *opt,
			struct netlink_ext_ack *extack)
{
	struct tc_skbprio_qopt *ctl = nla_data(opt);

	if (opt->nla_len != nla_attr_size(sizeof(*ctl)))
		return -EINVAL;

	WRITE_ONCE(sch->limit, ctl->limit);
	return 0;
}

static int skbprio_init(struct Qdisc *sch, struct nlattr *opt,
			struct netlink_ext_ack *extack)
{
	struct skbprio_sched_data *q = qdisc_priv(sch);
	int prio;

	/* Initialise all queues, one for each possible priority. */
	for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
		__skb_queue_head_init(&q->qdiscs[prio]);

	memset(&q->qstats, 0, sizeof(q->qstats));
	q->highest_prio = 0;
	q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
	sch->limit = 64;
	if (!opt)
		return 0;

	return skbprio_change(sch, opt, extack);
}

static int skbprio_dump(struct Qdisc *sch, struct sk_buff *skb)
{
	struct tc_skbprio_qopt opt;

	opt.limit = READ_ONCE(sch->limit);

	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
		return -1;

	return skb->len;
}

static void skbprio_reset(struct Qdisc *sch)
{
	struct skbprio_sched_data *q = qdisc_priv(sch);
	int prio;

	for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
		__skb_queue_purge(&q->qdiscs[prio]);

	memset(&q->qstats, 0, sizeof(q->qstats));
	q->highest_prio = 0;
	q->lowest_prio = SKBPRIO_MAX_PRIORITY - 1;
}

static void skbprio_destroy(struct Qdisc *sch)
{
	struct skbprio_sched_data *q = qdisc_priv(sch);
	int prio;

	for (prio = 0; prio < SKBPRIO_MAX_PRIORITY; prio++)
		__skb_queue_purge(&q->qdiscs[prio]);
}

static struct Qdisc *skbprio_leaf(struct Qdisc *sch, unsigned long arg)
{
	return NULL;
}

static unsigned long skbprio_find(struct Qdisc *sch, u32 classid)
{
	return 0;
}

static int skbprio_dump_class(struct Qdisc *sch, unsigned long cl,
			     struct sk_buff *skb, struct tcmsg *tcm)
{
	tcm->tcm_handle |= TC_H_MIN(cl);
	return 0;
}

static int skbprio_dump_class_stats(struct Qdisc *sch, unsigned long cl,
				   struct gnet_dump *d)
{
	struct skbprio_sched_data *q = qdisc_priv(sch);
	if (gnet_stats_copy_queue(d, NULL, &q->qstats[cl - 1],
		q->qstats[cl - 1].qlen) < 0)
		return -1;
	return 0;
}

static void skbprio_walk(struct Qdisc *sch, struct qdisc_walker *arg)
{
	unsigned int i;

	if (arg->stop)
		return;

	for (i = 0; i < SKBPRIO_MAX_PRIORITY; i++) {
		if (!tc_qdisc_stats_dump(sch, i + 1, arg))
			break;
	}
}

static const struct Qdisc_class_ops skbprio_class_ops = {
	.leaf		=	skbprio_leaf,
	.find		=	skbprio_find,
	.dump		=	skbprio_dump_class,
	.dump_stats	=	skbprio_dump_class_stats,
	.walk		=	skbprio_walk,
};

static struct Qdisc_ops skbprio_qdisc_ops __read_mostly = {
	.cl_ops		=	&skbprio_class_ops,
	.id		=	"skbprio",
	.priv_size	=	sizeof(struct skbprio_sched_data),
	.enqueue	=	skbprio_enqueue,
	.dequeue	=	skbprio_dequeue,
	.peek		=	qdisc_peek_dequeued,
	.init		=	skbprio_init,
	.reset		=	skbprio_reset,
	.change		=	skbprio_change,
	.dump		=	skbprio_dump,
	.destroy	=	skbprio_destroy,
	.owner		=	THIS_MODULE,
};
MODULE_ALIAS_NET_SCH("skbprio");

static int __init skbprio_module_init(void)
{
	return register_qdisc(&skbprio_qdisc_ops);
}

static void __exit skbprio_module_exit(void)
{
	unregister_qdisc(&skbprio_qdisc_ops);
}

module_init(skbprio_module_init)
module_exit(skbprio_module_exit)

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("SKB priority based scheduling qdisc");