net/dccp/qpolicy.c

   1 /*
   2  *  net/dccp/qpolicy.c
   3  *
   4  *  Policy-based packet dequeueing interface for DCCP.
   5  *
   6  *  Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
   7  *
   8  *  This program is free software; you can redistribute it and/or
   9  *  modify it under the terms of the GNU General Public License v2
  10  *  as published by the Free Software Foundation.
  11  */
  12 #include "dccp.h"
  13
  14 /*
  15  *      Simple Dequeueing Policy:
  16  *      If tx_qlen is different from 0, enqueue up to tx_qlen elements.
  17  */
  18 static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
  19 {
  20         skb_queue_tail(&sk->sk_write_queue, skb);
  21 }
  22
  23 static bool qpolicy_simple_full(struct sock *sk)
  24 {
  25         return dccp_sk(sk)->dccps_tx_qlen &&
  26                sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
  27 }
  28
  29 static struct sk_buff *qpolicy_simple_top(struct sock *sk)
  30 {
  31         return skb_peek(&sk->sk_write_queue);
  32 }
  33
  34 /*
  35  *      Priority-based Dequeueing Policy:
  36  *      If tx_qlen is different from 0 and the queue has reached its upper bound
  37  *      of tx_qlen elements, replace older packets lowest-priority-first.
  38  */
  39 static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
  40 {
  41         struct sk_buff *skb, *best = NULL;
  42
  43         skb_queue_walk(&sk->sk_write_queue, skb)
  44                 if (best == NULL || skb->priority > best->priority)
  45                         best = skb;
  46         return best;
  47 }
  48
  49 static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
  50 {
  51         struct sk_buff *skb, *worst = NULL;
  52
  53         skb_queue_walk(&sk->sk_write_queue, skb)
  54                 if (worst == NULL || skb->priority < worst->priority)
  55                         worst = skb;
  56         return worst;
  57 }
  58
  59 static bool qpolicy_prio_full(struct sock *sk)
  60 {
  61         if (qpolicy_simple_full(sk))
  62                 dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
  63         return false;
  64 }
  65
  66 /**
  67  * struct dccp_qpolicy_operations  -  TX Packet Dequeueing Interface
  68  * @push: add a new @skb to the write queue
  69  * @full: indicates that no more packets will be admitted
  70  * @top:  peeks at whatever the queueing policy defines as its `top'
  71  */
  72 static struct dccp_qpolicy_operations {
  73         void            (*push) (struct sock *sk, struct sk_buff *skb);
  74         bool            (*full) (struct sock *sk);
  75         struct sk_buff* (*top)  (struct sock *sk);
  76         __be32          params;
  77
  78 } qpol_table[DCCPQ_POLICY_MAX] = {
  79         [DCCPQ_POLICY_SIMPLE] = {
  80                 .push   = qpolicy_simple_push,
  81                 .full   = qpolicy_simple_full,
  82                 .top    = qpolicy_simple_top,
  83                 .params = 0,
  84         },
  85         [DCCPQ_POLICY_PRIO] = {
  86                 .push   = qpolicy_simple_push,
  87                 .full   = qpolicy_prio_full,
  88                 .top    = qpolicy_prio_best_skb,
  89                 .params = DCCP_SCM_PRIORITY,
  90         },
  91 };
  92
  93 /*
  94  *      Externally visible interface
  95  */
  96 void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
  97 {
  98         qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
  99 }
 100
 101 bool dccp_qpolicy_full(struct sock *sk)
 102 {
 103         return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
 104 }
 105
 106 void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
 107 {
 108         if (skb != NULL) {
 109                 skb_unlink(skb, &sk->sk_write_queue);
 110                 kfree_skb(skb);
 111         }
 112 }
 113
 114 struct sk_buff *dccp_qpolicy_top(struct sock *sk)
 115 {
 116         return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
 117 }
 118
 119 struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
 120 {
 121         struct sk_buff *skb = dccp_qpolicy_top(sk);
 122
 123         if (skb != NULL) {
 124                 /* Clear any skb fields that we used internally */
 125                 skb->priority = 0;
 126                 skb_unlink(skb, &sk->sk_write_queue);
 127         }
 128         return skb;
 129 }
 130
 131 bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param)
 132 {
 133         /* check if exactly one bit is set */
 134         if (!param || (param & (param - 1)))
 135                 return false;
 136         return (qpol_table[dccp_sk(sk)->dccps_qpolicy].params & param) == param;
 137 }