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/*
* net/dccp/qpolicy.c
*
* Policy-based packet dequeueing interface for DCCP.
*
* Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License v2
* as published by the Free Software Foundation.
*/
#include "dccp.h"
/*
* Simple Dequeueing Policy:
* If tx_qlen is different from 0, enqueue up to tx_qlen elements.
*/
static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
{
skb_queue_tail(&sk->sk_write_queue, skb);
}
static bool qpolicy_simple_full(struct sock *sk)
{
return dccp_sk(sk)->dccps_tx_qlen &&
sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
}
static struct sk_buff *qpolicy_simple_top(struct sock *sk)
{
return skb_peek(&sk->sk_write_queue);
}
/*
* Priority-based Dequeueing Policy:
* If tx_qlen is different from 0 and the queue has reached its upper bound
* of tx_qlen elements, replace older packets lowest-priority-first.
*/
static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
{
struct sk_buff *skb, *best = NULL;
skb_queue_walk(&sk->sk_write_queue, skb)
if (best == NULL || skb->priority > best->priority)
best = skb;
return best;
}
static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
{
struct sk_buff *skb, *worst = NULL;
skb_queue_walk(&sk->sk_write_queue, skb)
if (worst == NULL || skb->priority < worst->priority)
worst = skb;
return worst;
}
static bool qpolicy_prio_full(struct sock *sk)
{
if (qpolicy_simple_full(sk))
dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
return false;
}
/**
* struct dccp_qpolicy_operations - TX Packet Dequeueing Interface
* @push: add a new @skb to the write queue
* @full: indicates that no more packets will be admitted
* @top: peeks at whatever the queueing policy defines as its `top'
*/
static struct dccp_qpolicy_operations {
void (*push) (struct sock *sk, struct sk_buff *skb);
bool (*full) (struct sock *sk);
struct sk_buff* (*top) (struct sock *sk);
} qpol_table[DCCPQ_POLICY_MAX] = {
[DCCPQ_POLICY_SIMPLE] = {
.push = qpolicy_simple_push,
.full = qpolicy_simple_full,
.top = qpolicy_simple_top,
},
[DCCPQ_POLICY_PRIO] = {
.push = qpolicy_simple_push,
.full = qpolicy_prio_full,
.top = qpolicy_prio_best_skb,
},
};
/*
* Externally visible interface
*/
void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
{
qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
}
bool dccp_qpolicy_full(struct sock *sk)
{
return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
}
void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
{
if (skb != NULL) {
skb_unlink(skb, &sk->sk_write_queue);
kfree_skb(skb);
}
}
struct sk_buff *dccp_qpolicy_top(struct sock *sk)
{
return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
}
struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
{
struct sk_buff *skb = dccp_qpolicy_top(sk);
if (skb != NULL) {
/* Clear any skb fields that we used internally */
skb->priority = 0;
skb_unlink(skb, &sk->sk_write_queue);
}
return skb;
}
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