On Wed, 8 Jul 2020 23:26:34 -0700
Stephen Hemminger <step...@networkplumber.org> wrote:
> On Thu, 9 Jul 2020 16:10:34 +1000
> Russell Strong <russ...@strong.id.au> wrote:
>
> > Hi,
> >
> > I'm attempting to fill a link with background traffic that is sent
> > whenever the link is idle. To do this I've creates a qdisc that
> > will repeat the last packet in the queue for a defined number of
> > times (possibly infinite in the future). I am able to control the
> > contents of the fill traffic by sending the occasional packet
> > through this qdisc.
> >
> > This is works as the root qdisc and below a TBF. When I try it as a
> > leaf of HTB unexpected behaviour ensues. I suspect my approach is
> > violating some rules for qdiscs? Any help/ideas/pointers would be
> > appreciated.
>
> Netem can already do things like this. Why not add to that
>
Hi,
Tried doing this within netem as follows; but run into similar
problems. Works as the root qdisc (except for "Route cache is full:
consider increasing sysctl net.ipv[4|6].route.max_size.") but not under
htb. I am attempting to duplicate at dequeue, rather than enqueue to
get an infinite stream of packets rather than a fixed number of
duplicates. Is this possible?
Thanks
Russell
diff --git a/sch_netem.c b/sch_netem.c
index 42e557d..9a674df 100644
--- a/sch_netem.c
+++ b/sch_netem.c
@@ -98,6 +98,7 @@ struct netem_sched_data {
u32 cell_size;
struct reciprocal_value cell_size_reciprocal;
s32 cell_overhead;
+ u32 repeat_last;
struct crndstate {
u32 last;
@@ -697,9 +698,13 @@ deliver:
get_slot_next(q, now);
if (time_to_send <= now && q->slot.slot_next <= now) {
- netem_erase_head(q, skb);
- sch->q.qlen--;
- qdisc_qstats_backlog_dec(sch, skb);
+ if (sch->q.qlen == 1 && q->repeat_last)
+ skb = skb_clone(skb, GFP_ATOMIC);
+ else {
+ netem_erase_head(q, skb);
+ sch->q.qlen--;
+ qdisc_qstats_backlog_dec(sch, skb);
+ }
skb->next = NULL;
skb->prev = NULL;
/* skb->dev shares skb->rbnode area,
@@ -1061,6 +1066,7 @@ static int netem_init(struct Qdisc *sch, struct
nlattr *opt, return -EINVAL;
q->loss_model = CLG_RANDOM;
+ q->repeat_last = 1;
ret = netem_change(sch, opt, extack);
if (ret)
pr_info("netem: change failed\n");
