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/*
* sch_queue.c Queue traffic until an explicit release command
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* The operation of the buffer is as follows:
* When a checkpoint begins, a barrier is inserted into the
* network queue by a netlink request (it operates by storing
* a pointer to the next packet which arrives and blocking dequeue
* when that packet is at the head of the queue).
* When a checkpoint completes (the backup acknowledges receipt),
* currently-queued packets are released.
* So it supports two operations, barrier and release.
*/
#include <linux/config.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <net/pkt_sched.h>
/* xenbus directory */
#define FIFO_BUF (10*1024*1024)
#define TCQ_CHECKPOINT 0
#define TCQ_DEQUEUE 1
struct queue_sched_data {
/* this packet is the first packet which should not be delivered.
* If it is NULL, queue_enqueue will set it to the next packet it sees. */
struct sk_buff *stop;
};
struct tc_queue_qopt {
/* 0: reset stop packet pointer
* 1: dequeue to stop pointer */
int action;
};
/* borrowed from drivers/xen/netback/loopback.c */
#ifdef CONFIG_X86
static int is_foreign(unsigned long pfn)
{
/* NB. Play it safe for auto-translation mode. */
return (xen_feature(XENFEAT_auto_translated_physmap) ||
(phys_to_machine_mapping[pfn] & FOREIGN_FRAME_BIT));
}
#else
/* How to detect a foreign mapping? Play it safe. */
#define is_foreign(pfn) (1)
#endif
static int skb_remove_foreign_references(struct sk_buff *skb)
{
struct page *page;
unsigned long pfn;
int i, off;
char *vaddr;
BUG_ON(skb_shinfo(skb)->frag_list);
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
pfn = page_to_pfn(skb_shinfo(skb)->frags[i].page);
if (!is_foreign(pfn))
continue;
/*
printk("foreign ref found\n");
*/
page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
if (unlikely(!page))
return 0;
vaddr = kmap_skb_frag(&skb_shinfo(skb)->frags[i]);
off = skb_shinfo(skb)->frags[i].page_offset;
memcpy(page_address(page) + off, vaddr + off,
skb_shinfo(skb)->frags[i].size);
kunmap_skb_frag(vaddr);
put_page(skb_shinfo(skb)->frags[i].page);
skb_shinfo(skb)->frags[i].page = page;
}
return 1;
}
static int queue_enqueue(struct sk_buff *skb, struct Qdisc* sch)
{
struct queue_sched_data *q = qdisc_priv(sch);
if (likely(sch->qstats.backlog + skb->len <= FIFO_BUF))
{
if (!q->stop)
q->stop = skb;
if (!skb_remove_foreign_references(skb)) {
printk("error removing foreign ref\n");
return qdisc_reshape_fail(skb, sch);
}
return qdisc_enqueue_tail(skb, sch);
}
printk("queue reported full: %d,%d\n", sch->qstats.backlog, skb->len);
return qdisc_reshape_fail(skb, sch);
}
/* dequeue doesn't actually dequeue until the release command is
* received. */
static inline struct sk_buff *queue_dequeue(struct Qdisc* sch)
{
struct queue_sched_data *q = qdisc_priv(sch);
struct sk_buff* peek;
/*
struct timeval tv;
if (!q->stop) {
do_gettimeofday(&tv);
printk("packet dequeued at %lu.%06lu\n", tv.tv_sec, tv.tv_usec);
}
*/
if (sch->flags & TCQ_F_THROTTLED)
return NULL;
peek = (struct sk_buff *)((sch->q).next);
/* this pointer comparison may be shady */
if (peek == q->stop) {
/*
do_gettimeofday(&tv);
printk("stop packet at %lu.%06lu\n", tv.tv_sec, tv.tv_usec);
*/
/* this is the tail of the last round. Release it and block the queue */
sch->flags |= TCQ_F_THROTTLED;
return NULL;
}
return qdisc_dequeue_head(sch);
}
static int queue_init(struct Qdisc *sch, struct rtattr *opt)
{
sch->flags |= TCQ_F_THROTTLED;
return 0;
}
/* receives two messages:
* 0: checkpoint queue (set stop to next packet)
* 1: dequeue until stop */
static int queue_change(struct Qdisc* sch, struct rtattr* opt)
{
struct queue_sched_data *q = qdisc_priv(sch);
struct tc_queue_qopt* msg;
/*
struct timeval tv;
*/
if (!opt || RTA_PAYLOAD(opt) < sizeof(*msg))
return -EINVAL;
msg = RTA_DATA(opt);
if (msg->action == TCQ_CHECKPOINT) {
/* reset stop */
q->stop = NULL;
} else if (msg->action == TCQ_DEQUEUE) {
/* dequeue */
sch->flags &= ~TCQ_F_THROTTLED;
netif_schedule(sch->dev);
/*
do_gettimeofday(&tv);
printk("queue release at %lu.%06lu (%d bytes)\n", tv.tv_sec, tv.tv_usec,
sch->qstats.backlog);
*/
} else {
return -EINVAL;
}
return 0;
}
struct Qdisc_ops queue_qdisc_ops = {
.id = "queue",
.priv_size = sizeof(struct queue_sched_data),
.enqueue = queue_enqueue,
.dequeue = queue_dequeue,
.init = queue_init,
.change = queue_change,
.owner = THIS_MODULE,
};
static int __init queue_module_init(void)
{
printk("loading queue\n");
return register_qdisc(&queue_qdisc_ops);
}
static void __exit queue_module_exit(void)
{
printk("queue unloaded\n");
unregister_qdisc(&queue_qdisc_ops);
}
module_init(queue_module_init)
module_exit(queue_module_exit)
MODULE_LICENSE("GPL");
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