4 * Policy-based packet dequeueing interface for DCCP.
6 * Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
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.
15 * Simple Dequeueing Policy:
16 * If tx_qlen is different from 0, enqueue up to tx_qlen elements.
18 static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
20 skb_queue_tail(&sk->sk_write_queue, skb);
23 static bool qpolicy_simple_full(struct sock *sk)
25 return dccp_sk(sk)->dccps_tx_qlen &&
26 sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
29 static struct sk_buff *qpolicy_simple_top(struct sock *sk)
31 return skb_peek(&sk->sk_write_queue);
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.
39 static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
41 struct sk_buff *skb, *best = NULL;
43 skb_queue_walk(&sk->sk_write_queue, skb)
44 if (best == NULL || skb->priority > best->priority)
49 static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
51 struct sk_buff *skb, *worst = NULL;
53 skb_queue_walk(&sk->sk_write_queue, skb)
54 if (worst == NULL || skb->priority < worst->priority)
59 static bool qpolicy_prio_full(struct sock *sk)
61 if (qpolicy_simple_full(sk))
62 dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
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'
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);
77 } qpol_table[DCCPQ_POLICY_MAX] = {
78 [DCCPQ_POLICY_SIMPLE] = {
79 .push = qpolicy_simple_push,
80 .full = qpolicy_simple_full,
81 .top = qpolicy_simple_top,
83 [DCCPQ_POLICY_PRIO] = {
84 .push = qpolicy_simple_push,
85 .full = qpolicy_prio_full,
86 .top = qpolicy_prio_best_skb,
91 * Externally visible interface
93 void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
95 qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
98 bool dccp_qpolicy_full(struct sock *sk)
100 return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
103 void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
106 skb_unlink(skb, &sk->sk_write_queue);
111 struct sk_buff *dccp_qpolicy_top(struct sock *sk)
113 return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
116 struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
118 struct sk_buff *skb = dccp_qpolicy_top(sk);
120 /* Clear any skb fields that we used internally */
124 skb_unlink(skb, &sk->sk_write_queue);