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 } 138