[NETEM]: Support time based reordering

Change netem to support packets getting reordered because of variations in
delay. Introduce a special case version of FIFO that queues packets in order
based on the netem delay.

Since netem is classful, those users that don't want jitter based reordering
can just insert a pfifo instead of the default.

This required changes to generic skbuff code to allow finer grain manipulation
of sk_buff_head.  Insertion into the middle and reverse walk.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@mandriva.com>
This commit is contained in:
Stephen Hemminger 2005-10-30 13:47:34 -08:00 committed by Arnaldo Carvalho de Melo
parent 07aaa11540
commit 300ce174eb
2 changed files with 114 additions and 9 deletions

View File

@ -602,6 +602,30 @@ static inline void skb_queue_head_init(struct sk_buff_head *list)
* can only be called with interrupts disabled.
*/
/**
* __skb_queue_after - queue a buffer at the list head
* @list: list to use
* @prev: place after this buffer
* @newsk: buffer to queue
*
* Queue a buffer int the middle of a list. This function takes no locks
* and you must therefore hold required locks before calling it.
*
* A buffer cannot be placed on two lists at the same time.
*/
static inline void __skb_queue_after(struct sk_buff_head *list,
struct sk_buff *prev,
struct sk_buff *newsk)
{
struct sk_buff *next;
list->qlen++;
next = prev->next;
newsk->next = next;
newsk->prev = prev;
next->prev = prev->next = newsk;
}
/**
* __skb_queue_head - queue a buffer at the list head
* @list: list to use
@ -616,14 +640,7 @@ extern void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk);
static inline void __skb_queue_head(struct sk_buff_head *list,
struct sk_buff *newsk)
{
struct sk_buff *prev, *next;
list->qlen++;
prev = (struct sk_buff *)list;
next = prev->next;
newsk->next = next;
newsk->prev = prev;
next->prev = prev->next = newsk;
__skb_queue_after(list, (struct sk_buff *)list, newsk);
}
/**
@ -1203,6 +1220,11 @@ static inline void kunmap_skb_frag(void *vaddr)
prefetch(skb->next), (skb != (struct sk_buff *)(queue)); \
skb = skb->next)
#define skb_queue_reverse_walk(queue, skb) \
for (skb = (queue)->prev; \
prefetch(skb->prev), (skb != (struct sk_buff *)(queue)); \
skb = skb->prev)
extern struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
int noblock, int *err);

View File

@ -300,11 +300,16 @@ static void netem_reset(struct Qdisc *sch)
del_timer_sync(&q->timer);
}
/* Pass size change message down to embedded FIFO */
static int set_fifo_limit(struct Qdisc *q, int limit)
{
struct rtattr *rta;
int ret = -ENOMEM;
/* Hack to avoid sending change message to non-FIFO */
if (strncmp(q->ops->id + 1, "fifo", 4) != 0)
return 0;
rta = kmalloc(RTA_LENGTH(sizeof(struct tc_fifo_qopt)), GFP_KERNEL);
if (rta) {
rta->rta_type = RTM_NEWQDISC;
@ -436,6 +441,84 @@ static int netem_change(struct Qdisc *sch, struct rtattr *opt)
return 0;
}
/*
* Special case version of FIFO queue for use by netem.
* It queues in order based on timestamps in skb's
*/
struct fifo_sched_data {
u32 limit;
};
static int tfifo_enqueue(struct sk_buff *nskb, struct Qdisc *sch)
{
struct fifo_sched_data *q = qdisc_priv(sch);
struct sk_buff_head *list = &sch->q;
const struct netem_skb_cb *ncb
= (const struct netem_skb_cb *)nskb->cb;
struct sk_buff *skb;
if (likely(skb_queue_len(list) < q->limit)) {
skb_queue_reverse_walk(list, skb) {
const struct netem_skb_cb *cb
= (const struct netem_skb_cb *)skb->cb;
if (PSCHED_TLESS(cb->time_to_send, ncb->time_to_send))
break;
}
__skb_queue_after(list, skb, nskb);
sch->qstats.backlog += nskb->len;
sch->bstats.bytes += nskb->len;
sch->bstats.packets++;
return NET_XMIT_SUCCESS;
}
return qdisc_drop(nskb, sch);
}
static int tfifo_init(struct Qdisc *sch, struct rtattr *opt)
{
struct fifo_sched_data *q = qdisc_priv(sch);
if (opt) {
struct tc_fifo_qopt *ctl = RTA_DATA(opt);
if (RTA_PAYLOAD(opt) < sizeof(*ctl))
return -EINVAL;
q->limit = ctl->limit;
} else
q->limit = max_t(u32, sch->dev->tx_queue_len, 1);
return 0;
}
static int tfifo_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct fifo_sched_data *q = qdisc_priv(sch);
struct tc_fifo_qopt opt = { .limit = q->limit };
RTA_PUT(skb, TCA_OPTIONS, sizeof(opt), &opt);
return skb->len;
rtattr_failure:
return -1;
}
static struct Qdisc_ops tfifo_qdisc_ops = {
.id = "tfifo",
.priv_size = sizeof(struct fifo_sched_data),
.enqueue = tfifo_enqueue,
.dequeue = qdisc_dequeue_head,
.requeue = qdisc_requeue,
.drop = qdisc_queue_drop,
.init = tfifo_init,
.reset = qdisc_reset_queue,
.change = tfifo_init,
.dump = tfifo_dump,
};
static int netem_init(struct Qdisc *sch, struct rtattr *opt)
{
struct netem_sched_data *q = qdisc_priv(sch);
@ -448,7 +531,7 @@ static int netem_init(struct Qdisc *sch, struct rtattr *opt)
q->timer.function = netem_watchdog;
q->timer.data = (unsigned long) sch;
q->qdisc = qdisc_create_dflt(sch->dev, &pfifo_qdisc_ops);
q->qdisc = qdisc_create_dflt(sch->dev, &tfifo_qdisc_ops);
if (!q->qdisc) {
pr_debug("netem: qdisc create failed\n");
return -ENOMEM;