net/sched/sch_fifo.c

   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
  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
  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
  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
  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
  84 static 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
  92 nla_put_failure:
  93         return -1;
  94 }
  95
  96 struct 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 };
 109 EXPORT_SYMBOL(pfifo_qdisc_ops);
 110
 111 struct 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 };
 124 EXPORT_SYMBOL(bfifo_qdisc_ops);
 125
 126 struct 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 */
 141 int 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 }
 161 EXPORT_SYMBOL(fifo_set_limit);
 162
 163 struct 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 }
 180 EXPORT_SYMBOL(fifo_create_dflt);