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
bfifo_enqueue(struct sk_buff * skb,struct Qdisc * sch)22 static 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
pfifo_enqueue(struct sk_buff * skb,struct Qdisc * sch)30 static 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
pfifo_tail_enqueue(struct sk_buff * skb,struct Qdisc * sch)38 static 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 sch->qstats.drops++;
46 qdisc_enqueue_tail(skb, sch);
47
48 return NET_XMIT_CN;
49 }
50
fifo_init(struct Qdisc * sch,struct nlattr * opt)51 static 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
fifo_dump(struct Qdisc * sch,struct sk_buff * skb)84 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
85 {
86 struct tc_fifo_qopt opt = { .limit = sch->limit };
87
88 NLA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
89 return skb->len;
90
91 nla_put_failure:
92 return -1;
93 }
94
95 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
96 .id = "pfifo",
97 .priv_size = 0,
98 .enqueue = pfifo_enqueue,
99 .dequeue = qdisc_dequeue_head,
100 .peek = qdisc_peek_head,
101 .drop = qdisc_queue_drop,
102 .init = fifo_init,
103 .reset = qdisc_reset_queue,
104 .change = fifo_init,
105 .dump = fifo_dump,
106 .owner = THIS_MODULE,
107 };
108 EXPORT_SYMBOL(pfifo_qdisc_ops);
109
110 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
111 .id = "bfifo",
112 .priv_size = 0,
113 .enqueue = bfifo_enqueue,
114 .dequeue = qdisc_dequeue_head,
115 .peek = qdisc_peek_head,
116 .drop = qdisc_queue_drop,
117 .init = fifo_init,
118 .reset = qdisc_reset_queue,
119 .change = fifo_init,
120 .dump = fifo_dump,
121 .owner = THIS_MODULE,
122 };
123 EXPORT_SYMBOL(bfifo_qdisc_ops);
124
125 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
126 .id = "pfifo_head_drop",
127 .priv_size = 0,
128 .enqueue = pfifo_tail_enqueue,
129 .dequeue = qdisc_dequeue_head,
130 .peek = qdisc_peek_head,
131 .drop = qdisc_queue_drop_head,
132 .init = fifo_init,
133 .reset = qdisc_reset_queue,
134 .change = fifo_init,
135 .dump = fifo_dump,
136 .owner = THIS_MODULE,
137 };
138
139 /* Pass size change message down to embedded FIFO */
fifo_set_limit(struct Qdisc * q,unsigned int limit)140 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
141 {
142 struct nlattr *nla;
143 int ret = -ENOMEM;
144
145 /* Hack to avoid sending change message to non-FIFO */
146 if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
147 return 0;
148
149 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
150 if (nla) {
151 nla->nla_type = RTM_NEWQDISC;
152 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
153 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
154
155 ret = q->ops->change(q, nla);
156 kfree(nla);
157 }
158 return ret;
159 }
160 EXPORT_SYMBOL(fifo_set_limit);
161
fifo_create_dflt(struct Qdisc * sch,struct Qdisc_ops * ops,unsigned int limit)162 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
163 unsigned int limit)
164 {
165 struct Qdisc *q;
166 int err = -ENOMEM;
167
168 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1));
169 if (q) {
170 err = fifo_set_limit(q, limit);
171 if (err < 0) {
172 qdisc_destroy(q);
173 q = NULL;
174 }
175 }
176
177 return q ? : ERR_PTR(err);
178 }
179 EXPORT_SYMBOL(fifo_create_dflt);
180