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This patch adds a generic infrastructure for policy-based dequeueing of TX packets and provides two policies: * a simple FIFO policy (which is the default) and * a priority based policy (set via socket options). Both policies honour the tx_qlen sysctl for the maximum size of the write queue (can be overridden via socket options). The priority policy uses skb->priority internally to assign an u32 priority identifier, using the same ranking as SO_PRIORITY. The skb->priority field is set to 0 when the packet leaves DCCP. The priority is supplied as ancillary data using cmsg(3), the patch also provides the requisite parsing routines. Signed-off-by: Tomasz Grobelny <tomasz@grobelny.oswiecenia.net> Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
127 lines
3.0 KiB
C
127 lines
3.0 KiB
C
/*
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* net/dccp/qpolicy.c
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*
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* Policy-based packet dequeueing interface for DCCP.
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*
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* Copyright (c) 2008 Tomasz Grobelny <tomasz@grobelny.oswiecenia.net>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License v2
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* as published by the Free Software Foundation.
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*/
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#include "dccp.h"
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/*
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* Simple Dequeueing Policy:
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* If tx_qlen is different from 0, enqueue up to tx_qlen elements.
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*/
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static void qpolicy_simple_push(struct sock *sk, struct sk_buff *skb)
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{
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skb_queue_tail(&sk->sk_write_queue, skb);
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}
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static bool qpolicy_simple_full(struct sock *sk)
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{
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return dccp_sk(sk)->dccps_tx_qlen &&
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sk->sk_write_queue.qlen >= dccp_sk(sk)->dccps_tx_qlen;
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}
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static struct sk_buff *qpolicy_simple_top(struct sock *sk)
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{
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return skb_peek(&sk->sk_write_queue);
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}
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/*
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* Priority-based Dequeueing Policy:
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* If tx_qlen is different from 0 and the queue has reached its upper bound
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* of tx_qlen elements, replace older packets lowest-priority-first.
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*/
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static struct sk_buff *qpolicy_prio_best_skb(struct sock *sk)
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{
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struct sk_buff *skb, *best = NULL;
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skb_queue_walk(&sk->sk_write_queue, skb)
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if (best == NULL || skb->priority > best->priority)
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best = skb;
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return best;
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}
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static struct sk_buff *qpolicy_prio_worst_skb(struct sock *sk)
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{
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struct sk_buff *skb, *worst = NULL;
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skb_queue_walk(&sk->sk_write_queue, skb)
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if (worst == NULL || skb->priority < worst->priority)
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worst = skb;
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return worst;
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}
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static bool qpolicy_prio_full(struct sock *sk)
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{
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if (qpolicy_simple_full(sk))
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dccp_qpolicy_drop(sk, qpolicy_prio_worst_skb(sk));
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return false;
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}
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/**
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* struct dccp_qpolicy_operations - TX Packet Dequeueing Interface
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* @push: add a new @skb to the write queue
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* @full: indicates that no more packets will be admitted
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* @top: peeks at whatever the queueing policy defines as its `top'
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*/
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static struct dccp_qpolicy_operations {
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void (*push) (struct sock *sk, struct sk_buff *skb);
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bool (*full) (struct sock *sk);
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struct sk_buff* (*top) (struct sock *sk);
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} qpol_table[DCCPQ_POLICY_MAX] = {
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[DCCPQ_POLICY_SIMPLE] = {
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.push = qpolicy_simple_push,
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.full = qpolicy_simple_full,
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.top = qpolicy_simple_top,
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},
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[DCCPQ_POLICY_PRIO] = {
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.push = qpolicy_simple_push,
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.full = qpolicy_prio_full,
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.top = qpolicy_prio_best_skb,
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},
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};
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/*
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* Externally visible interface
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*/
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void dccp_qpolicy_push(struct sock *sk, struct sk_buff *skb)
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{
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qpol_table[dccp_sk(sk)->dccps_qpolicy].push(sk, skb);
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}
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bool dccp_qpolicy_full(struct sock *sk)
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{
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return qpol_table[dccp_sk(sk)->dccps_qpolicy].full(sk);
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}
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void dccp_qpolicy_drop(struct sock *sk, struct sk_buff *skb)
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{
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if (skb != NULL) {
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skb_unlink(skb, &sk->sk_write_queue);
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kfree_skb(skb);
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}
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}
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struct sk_buff *dccp_qpolicy_top(struct sock *sk)
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{
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return qpol_table[dccp_sk(sk)->dccps_qpolicy].top(sk);
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}
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struct sk_buff *dccp_qpolicy_pop(struct sock *sk)
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{
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struct sk_buff *skb = dccp_qpolicy_top(sk);
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/* Clear any skb fields that we used internally */
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skb->priority = 0;
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if (skb)
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skb_unlink(skb, &sk->sk_write_queue);
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return skb;
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}
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