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
16 /* 1 band FIFO pseudo-"scheduler" */
17
bfifo_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)18 static int bfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
19 struct sk_buff **to_free)
20 {
21 if (likely(sch->qstats.backlog + qdisc_pkt_len(skb) <= sch->limit))
22 return qdisc_enqueue_tail(skb, sch);
23
24 return qdisc_drop(skb, sch, to_free);
25 }
26
pfifo_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)27 static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc *sch,
28 struct sk_buff **to_free)
29 {
30 if (likely(sch->q.qlen < sch->limit))
31 return qdisc_enqueue_tail(skb, sch);
32
33 return qdisc_drop(skb, sch, to_free);
34 }
35
pfifo_tail_enqueue(struct sk_buff * skb,struct Qdisc * sch,struct sk_buff ** to_free)36 static int pfifo_tail_enqueue(struct sk_buff *skb, struct Qdisc *sch,
37 struct sk_buff **to_free)
38 {
39 unsigned int prev_backlog;
40
41 if (likely(sch->q.qlen < sch->limit))
42 return qdisc_enqueue_tail(skb, sch);
43
44 prev_backlog = sch->qstats.backlog;
45 /* queue full, remove one skb to fulfill the limit */
46 __qdisc_queue_drop_head(sch, &sch->q, to_free);
47 qdisc_qstats_drop(sch);
48 qdisc_enqueue_tail(skb, sch);
49
50 qdisc_tree_reduce_backlog(sch, 0, prev_backlog - sch->qstats.backlog);
51 return NET_XMIT_CN;
52 }
53
fifo_init(struct Qdisc * sch,struct nlattr * opt,struct netlink_ext_ack * extack)54 static int fifo_init(struct Qdisc *sch, struct nlattr *opt,
55 struct netlink_ext_ack *extack)
56 {
57 bool bypass;
58 bool is_bfifo = sch->ops == &bfifo_qdisc_ops;
59
60 if (opt == NULL) {
61 u32 limit = qdisc_dev(sch)->tx_queue_len;
62
63 if (is_bfifo)
64 limit *= psched_mtu(qdisc_dev(sch));
65
66 sch->limit = limit;
67 } else {
68 struct tc_fifo_qopt *ctl = nla_data(opt);
69
70 if (nla_len(opt) < sizeof(*ctl))
71 return -EINVAL;
72
73 sch->limit = ctl->limit;
74 }
75
76 if (is_bfifo)
77 bypass = sch->limit >= psched_mtu(qdisc_dev(sch));
78 else
79 bypass = sch->limit >= 1;
80
81 if (bypass)
82 sch->flags |= TCQ_F_CAN_BYPASS;
83 else
84 sch->flags &= ~TCQ_F_CAN_BYPASS;
85 return 0;
86 }
87
fifo_dump(struct Qdisc * sch,struct sk_buff * skb)88 static int fifo_dump(struct Qdisc *sch, struct sk_buff *skb)
89 {
90 struct tc_fifo_qopt opt = { .limit = sch->limit };
91
92 if (nla_put(skb, TCA_OPTIONS, sizeof(opt), &opt))
93 goto nla_put_failure;
94 return skb->len;
95
96 nla_put_failure:
97 return -1;
98 }
99
100 struct Qdisc_ops pfifo_qdisc_ops __read_mostly = {
101 .id = "pfifo",
102 .priv_size = 0,
103 .enqueue = pfifo_enqueue,
104 .dequeue = qdisc_dequeue_head,
105 .peek = qdisc_peek_head,
106 .init = fifo_init,
107 .reset = qdisc_reset_queue,
108 .change = fifo_init,
109 .dump = fifo_dump,
110 .owner = THIS_MODULE,
111 };
112 EXPORT_SYMBOL(pfifo_qdisc_ops);
113
114 struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
115 .id = "bfifo",
116 .priv_size = 0,
117 .enqueue = bfifo_enqueue,
118 .dequeue = qdisc_dequeue_head,
119 .peek = qdisc_peek_head,
120 .init = fifo_init,
121 .reset = qdisc_reset_queue,
122 .change = fifo_init,
123 .dump = fifo_dump,
124 .owner = THIS_MODULE,
125 };
126 EXPORT_SYMBOL(bfifo_qdisc_ops);
127
128 struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
129 .id = "pfifo_head_drop",
130 .priv_size = 0,
131 .enqueue = pfifo_tail_enqueue,
132 .dequeue = qdisc_dequeue_head,
133 .peek = qdisc_peek_head,
134 .init = fifo_init,
135 .reset = qdisc_reset_queue,
136 .change = fifo_init,
137 .dump = fifo_dump,
138 .owner = THIS_MODULE,
139 };
140
141 /* Pass size change message down to embedded FIFO */
fifo_set_limit(struct Qdisc * q,unsigned int limit)142 int fifo_set_limit(struct Qdisc *q, unsigned int limit)
143 {
144 struct nlattr *nla;
145 int ret = -ENOMEM;
146
147 /* Hack to avoid sending change message to non-FIFO */
148 if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
149 return 0;
150
151 nla = kmalloc(nla_attr_size(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
152 if (nla) {
153 nla->nla_type = RTM_NEWQDISC;
154 nla->nla_len = nla_attr_size(sizeof(struct tc_fifo_qopt));
155 ((struct tc_fifo_qopt *)nla_data(nla))->limit = limit;
156
157 ret = q->ops->change(q, nla, NULL);
158 kfree(nla);
159 }
160 return ret;
161 }
162 EXPORT_SYMBOL(fifo_set_limit);
163
fifo_create_dflt(struct Qdisc * sch,struct Qdisc_ops * ops,unsigned int limit,struct netlink_ext_ack * extack)164 struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
165 unsigned int limit,
166 struct netlink_ext_ack *extack)
167 {
168 struct Qdisc *q;
169 int err = -ENOMEM;
170
171 q = qdisc_create_dflt(sch->dev_queue, ops, TC_H_MAKE(sch->handle, 1),
172 extack);
173 if (q) {
174 err = fifo_set_limit(q, limit);
175 if (err < 0) {
176 qdisc_put(q);
177 q = NULL;
178 }
179 }
180
181 return q ? : ERR_PTR(err);
182 }
183 EXPORT_SYMBOL(fifo_create_dflt);
184
