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This add an additional queuing strategy, called pfifo_head_drop,
to remove the oldest skb in the case of an overflow within the queue -
the head element - instead of the last skb (tail). To remove the oldest
skb in a congested situations is useful for sensor network environments
where newer packets reflects the superior information.
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
---
include/net/pkt_sched.h | 2 ++
net/sched/sch_api.c | 2 ++
net/sched/sch_fifo.c | 37 +++++++++++++++++++++++++++++++++++++
3 files changed, 41 insertions(+), 0 deletions(-)
diff --git a/include/net/pkt_sched.h b/include/net/pkt_sched.h
index 2d56726..42dc85a 100644
--- a/include/net/pkt_sched.h
+++ b/include/net/pkt_sched.h
@@ -71,6 +71,8 @@ extern void qdisc_watchdog_cancel(struct qdisc_watchdog *wd);
extern struct Qdisc_ops pfifo_qdisc_ops;
extern struct Qdisc_ops bfifo_qdisc_ops;
+extern struct Qdisc_ops pfifo_head_drop_qdisc_ops;
+extern struct Qdisc_ops bfifo_head_drop_qdisc_ops;
extern int fifo_set_limit(struct Qdisc *q, unsigned int limit);
extern struct Qdisc *fifo_create_dflt(struct Qdisc *sch, struct Qdisc_ops *ops,
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 75fd1c6..6eaa35d 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1707,6 +1707,8 @@ static int __init pktsched_init(void)
{
register_qdisc(&pfifo_qdisc_ops);
register_qdisc(&bfifo_qdisc_ops);
+ register_qdisc(&pfifo_head_drop_qdisc_ops);
+ register_qdisc(&bfifo_head_drop_qdisc_ops);
register_qdisc(&mq_qdisc_ops);
proc_net_fops_create(&init_net, "psched", 0, &psched_fops);
diff --git a/net/sched/sch_fifo.c b/net/sched/sch_fifo.c
index 69188e8..44f80ca 100644
--- a/net/sched/sch_fifo.c
+++ b/net/sched/sch_fifo.c
@@ -43,6 +43,28 @@ static int pfifo_enqueue(struct sk_buff *skb, struct Qdisc* sch)
return qdisc_reshape_fail(skb, sch);
}
+static int pfifo_front_enqueue(struct sk_buff *skb, struct Qdisc* sch)
+{
+ struct sk_buff *skb_head;
+ struct fifo_sched_data *q = qdisc_priv(sch);
+
+ if (likely(skb_queue_len(&sch->q) < q->limit))
+ return qdisc_enqueue_tail(skb, sch);
+
+ /* queue full, remove one skb to fulfill the limit */
+ skb_head = qdisc_dequeue_head(sch);
+ sch->bstats.bytes -= qdisc_pkt_len(skb_head);
+ sch->bstats.packets--;
+ sch->q.qlen--;
+ sch->qstats.drops++;
+ kfree_skb(skb_head);
+
+ qdisc_enqueue_tail(skb, sch);
+
+ return NET_XMIT_CN;
+}
+
+
static int fifo_init(struct Qdisc *sch, struct nlattr *opt)
{
struct fifo_sched_data *q = qdisc_priv(sch);
@@ -108,6 +130,21 @@ struct Qdisc_ops bfifo_qdisc_ops __read_mostly = {
};
EXPORT_SYMBOL(bfifo_qdisc_ops);
+struct Qdisc_ops pfifo_head_drop_qdisc_ops __read_mostly = {
+ .id = "pfifo_head_drop",
+ .priv_size = sizeof(struct fifo_sched_data),
+ .enqueue = pfifo_front_enqueue,
+ .dequeue = qdisc_dequeue_head,
+ .peek = qdisc_peek_head,
+ .drop = qdisc_queue_drop,
+ .init = fifo_init,
+ .reset = qdisc_reset_queue,
+ .change = fifo_init,
+ .dump = fifo_dump,
+ .owner = THIS_MODULE,
+};
+EXPORT_SYMBOL(pfifo_head_drop_qdisc_ops);
+
/* Pass size change message down to embedded FIFO */
int fifo_set_limit(struct Qdisc *q, unsigned int limit)
{
--
1.6.6.196.g1f735.dirty
--
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