1/*
2 * net/sched/sch_fifo.c	The simplest FIFO queue.
3 *
4 *		This program is free software; you can redistribute it and/or
5 *		modify it under the terms of the GNU General Public License
6 *		as published by the Free Software Foundation; either version
7 *		2 of the License, or (at your option) any later version.
8 *
9 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10 */
11
12#include <linux/module.h>
13#include <linux/slab.h>
14#include <linux/types.h>
15#include <linux/kernel.h>
16#include <linux/errno.h>
17#include <linux/skbuff.h>
18#include <net/pkt_sched.h>
19
20/* 1 band FIFO pseudo-"scheduler" */
21
22static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch)
23{
24	if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
25		return qdisc_enqueue_tail(skb, sch);
26
27	return qdisc_reshape_fail(skb, sch);
28}
29
30static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch)
31{
32	if (likely(skb_queue_len(&sch->q) < sch->limit))
33		return qdisc_enqueue_tail(skb, sch);
34
35	return qdisc_reshape_fail(skb, sch);
36}
37
38static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch)
39{
40	if (likely(skb_queue_len(&sch->q) < sch->limit))
41		return qdisc_enqueue_tail(skb, sch);
42
43	/* queue full, remove one skb to fulfill the limit */
44	__qdisc_queue_drop_head(sch, &sch->q);
45	qdisc_qstats_drop(sch);
46	qdisc_enqueue_tail(skb, sch);
47
48	return NET_XMIT_CN;
49}
50
51static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
52{
53	bool bypass;
54	bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
55
56	if (opt == NULL) {
57		u32 limit = qdisc_dev(sch)->tx_queue_len ? : 1;
58
59		if (is_bfifo)
60			limit *= psched_mtu(qdisc_dev(sch));
61
62		sch->limit = limit;
63	} else {
64		struct tc_fifo_qopt *ctl = nla_data(opt);
65
66		if (nla_len(opt) < sizeof(*ctl))
67			return -EINVAL;
68
69		sch->limit = ctl->limit;
70	}
71
72	if (is_bfifo)
73		bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
74	else
75		bypass = sch->limit >= 1;
76
77	if (bypass)
78		sch->flags |= TCQ_F_CAN_BYPASS;
79	else
80		sch->flags &= ~TCQ_F_CAN_BYPASS;
81	return 0;
82}
83
84static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
85{
86	struct tc_fifo_qopt opt = { .limit = sch->limit };
87
88	if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
89		goto nla_put_failure;
90	return skb->len;
91
92nla_put_failure:
93	return -1;
94}
95
96struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
97	.id		=	"pfifo",
98	.priv_size	=	0,
99	.enqueue	=	pfifo_enqueue,
100	.dequeue	=	qdisc_dequeue_head,
101	.peek		=	qdisc_peek_head,
102	.drop		=	qdisc_queue_drop,
103	.init		=	fifo_init,
104	.reset		=	qdisc_reset_queue,
105	.change		=	fifo_init,
106	.dump		=	fifo_dump,
107	.owner		=	THIS_MODULE,
108};
109EXPORT_SYMBOL(pfifo_qdisc_ops);
110
111struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
112	.id		=	"bfifo",
113	.priv_size	=	0,
114	.enqueue	=	bfifo_enqueue,
115	.dequeue	=	qdisc_dequeue_head,
116	.peek		=	qdisc_peek_head,
117	.drop		=	qdisc_queue_drop,
118	.init		=	fifo_init,
119	.reset		=	qdisc_reset_queue,
120	.change		=	fifo_init,
121	.dump		=	fifo_dump,
122	.owner		=	THIS_MODULE,
123};
124EXPORT_SYMBOL(bfifo_qdisc_ops);
125
126struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
127	.id		=	"pfifo_head_drop",
128	.priv_size	=	0,
129	.enqueue	=	pfifo_tail_enqueue,
130	.dequeue	=	qdisc_dequeue_head,
131	.peek		=	qdisc_peek_head,
132	.drop		=	qdisc_queue_drop_head,
133	.init		=	fifo_init,
134	.reset		=	qdisc_reset_queue,
135	.change		=	fifo_init,
136	.dump		=	fifo_dump,
137	.owner		=	THIS_MODULE,
138};
139
140/* Pass size change message down to embedded FIFO */
141int fifo_set_limit(struct Qdisc *q, unsigned int limit)
142{
143	struct nlattr *nla;
144	int ret = -ENOMEM;
145
146	/* Hack to avoid sending change message to non-FIFO */
147	if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
148		return 0;
149
150	nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
151	if (nla) {
152		nla->nla_type = RTM_NEWQDISC;
153		nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
154		((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
155
156		ret = q->ops->change(q, nla);
157		kfree(nla);
158	}
159	return ret;
160}
161EXPORT_SYMBOL(fifo_set_limit);
162
163struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
164			       unsigned int limit)
165{
166	struct Qdisc *q;
167	int err = -ENOMEM;
168
169	q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1));
170	if (q) {
171		err = fifo_set_limit(q, limit);
172		if (err < 0) {
173			qdisc_destroy(q);
174			q = NULL;
175		}
176	}
177
178	return q ? : ERR_PTR(err);
179}
180EXPORT_SYMBOL(fifo_create_dflt);
181