net/dccp/qpolicy.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *  net/dccp/qpolicy.c
   4  *
   5  *  Policy-based packet dequeueing interface for DCCP.
   6  *
   7  *  Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
   8  */
   9 #include "dccp.h"
  10
  11 /*
  12  *      Simple Dequeueing Policy:
  13  *      If tx_qlen is different from 0, enqueue up to tx_qlen elements.
  14  */
  15 static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
  16 {
  17         skb_queue_tail(&sk->sk_write_queue, skb);
  18 }
  19
  20 static bool qpolicy_simple_full(struct sock *sk)
  21 {
  22         return dccp_sk(sk)->dccps_tx_qlen &&
  23                sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
  24 }
  25
  26 static struct sk_buff *qpolicy_simple_top(struct sock *sk)
  27 {
  28         return skb_peek(&sk->sk_write_queue);
  29 }
  30
  31 /*
  32  *      Priority-based Dequeueing Policy:
  33  *      If tx_qlen is different from 0 and the queue has reached its upper bound
  34  *      of tx_qlen elements, replace older packets lowest-priority-first.
  35  */
  36 static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
  37 {
  38         struct sk_buff *skb, *best = NULL;
  39
  40         skb_queue_walk(&sk->sk_write_queue, skb)
  41                 if (best == NULL || skb->priority > best->priority)
  42                         best = skb;
  43         return best;
  44 }
  45
  46 static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
  47 {
  48         struct sk_buff *skb, *worst = NULL;
  49
  50         skb_queue_walk(&sk->sk_write_queue, skb)
  51                 if (worst == NULL || skb->priority < worst->priority)
  52                         worst = skb;
  53         return worst;
  54 }
  55
  56 static bool qpolicy_prio_full(struct sock *sk)
  57 {
  58         if (qpolicy_simple_full(sk))
  59                 dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
  60         return false;
  61 }
  62
  63 /**
  64  * struct dccp_qpolicy_operations  -  TX Packet Dequeueing Interface
  65  * @push: add a new @skb to the write queue
  66  * @full: indicates that no more packets will be admitted
  67  * @top:  peeks at whatever the queueing policy defines as its `top'
  68  * @params: parameter passed to policy operation
  69  */
  70 struct dccp_qpolicy_operations {
  71         void            (*push) (struct sock *sk, struct sk_buff *skb);
  72         bool            (*full) (struct sock *sk);
  73         struct sk_buff* (*top)  (struct sock *sk);
  74         __be32          params;
  75 };
  76
  77 static struct dccp_qpolicy_operations qpol_table[DCCPQ_POLICY_MAX] = {
  78         [DCCPQ_POLICY_SIMPLE] = {
  79                 .push   = qpolicy_simple_push,
  80                 .full   = qpolicy_simple_full,
  81                 .top    = qpolicy_simple_top,
  82                 .params = 0,
  83         },
  84         [DCCPQ_POLICY_PRIO] = {
  85                 .push   = qpolicy_simple_push,
  86                 .full   = qpolicy_prio_full,
  87                 .top    = qpolicy_prio_best_skb,
  88                 .params = DCCP_SCM_PRIORITY,
  89         },
  90 };
  91
  92 /*
  93  *      Externally visible interface
  94  */
  95 void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
  96 {
  97         qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
  98 }
  99
 100 bool dccp_qpolicy_full(struct sock *sk)
 101 {
 102         return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
 103 }
 104
 105 void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
 106 {
 107         if (skb != NULL) {
 108                 skb_unlink(skb, &sk->sk_write_queue);
 109                 kfree_skb(skb);
 110         }
 111 }
 112
 113 struct sk_buff *dccp_qpolicy_top(struct sock *sk)
 114 {
 115         return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
 116 }
 117
 118 struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
 119 {
 120         struct sk_buff *skb = dccp_qpolicy_top(sk);
 121
 122         if (skb != NULL) {
 123                 /* Clear any skb fields that we used internally */
 124                 skb->priority = 0;
 125                 skb_unlink(skb, &sk->sk_write_queue);
 126         }
 127         return skb;
 128 }
 129
 130 bool dccp_qpolicy_param_ok(struct sock *sk, __be32 param)
 131 {
 132         /* check if exactly one bit is set */
 133         if (!param || (param & (param - 1)))
 134                 return false;
 135         return (qpol_table[dccp_sk(sk)->dccps_qpolicy].params & param) == param;
 136 }