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[PKT_SCHED]: netem: reinsert for duplication 

Handle duplication of packets in netem by re-inserting at top of qdisc tree.
This avoid problems with qlen accounting with nested qdisc. This recursion
requires no additional locking but will potentially increase stack depth.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger 2005-05-26 12:53:49 -07:00 committed by David S. Miller
parent cdbbde14cb
commit 0afb51e728
1 changed files with 28 additions and 23 deletions
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51
net/sched/sch_netem.c
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@ -203,42 +203,47 @@ static int netem_run(struct Qdisc *sch)
return 0;
}
/*
* Insert one skb into qdisc.
* Note: parent depends on return value to account for queue length.
* NET_XMIT_DROP: queue length didn't change.
* NET_XMIT_SUCCESS: one skb was queued.
*/
static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch)
{
struct netem_sched_data *q = qdisc_priv(sch);
struct sk_buff *skb2;
int ret;
int count = 1;
pr_debug("netem_enqueue skb=%p\n", skb);
/* Random duplication */
if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor))
++count;
/* Random packet drop 0 => none, ~0 => all */
if (q->loss && q->loss >= get_crandom(&q->loss_cor)) {
pr_debug("netem_enqueue: random loss\n");
if (q->loss && q->loss >= get_crandom(&q->loss_cor))
--count;
if (count == 0) {
sch->qstats.drops++;
kfree_skb(skb);
return 0; /* lie about loss so TCP doesn't know */
return NET_XMIT_DROP;
}
/* Random duplication */
if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor)) {
struct sk_buff *skb2;
/*
* If we need to duplicate packet, then re-insert at top of the
* qdisc tree, since parent queuer expects that only one
* skb will be queued.
*/
if (count > 1 && (skb2 = skb_clone(skb, GFP_ATOMIC)) != NULL) {
struct Qdisc *rootq = sch->dev->qdisc;
u32 dupsave = q->duplicate; /* prevent duplicating a dup... */
q->duplicate = 0;
skb2 = skb_clone(skb, GFP_ATOMIC);
if (skb2 && netem_delay(sch, skb2) == NET_XMIT_SUCCESS) {
struct Qdisc *qp;
/* Since one packet can generate two packets in the
* queue, the parent's qlen accounting gets confused,
* so fix it.
*/
qp = qdisc_lookup(sch->dev, TC_H_MAJ(sch->parent));
if (qp)
qp->q.qlen++;
sch->q.qlen++;
sch->bstats.bytes += skb2->len;
sch->bstats.packets++;
} else
sch->qstats.drops++;
rootq->enqueue(skb2, rootq);
q->duplicate = dupsave;
}
/* If doing simple delay then gap == 0 so all packets