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Date: Sun, 27 Jun 2021 19:12:13 +0000
From: Niclas Hedam <nhed@....dk>
To: Cong Wang <xiyou.wangcong@...il.com>
CC: "stephen@...workplumber.org" <stephen@...workplumber.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] net: sched: Add support for packet bursting.
Hi Cong,
Good point.
Here is a new patch.
>From 71843907bdb9cdc4e24358f0c16a8778f2762dc7 Mon Sep 17 00:00:00 2001
From: Niclas Hedam <nhed@....dk>
Date: Fri, 25 Jun 2021 13:37:18 +0200
Subject: [PATCH] net: sched: Add support for packet bursting.
This commit implements packet bursting in the NetEm scheduler.
This allows system administrators to hold back outgoing
packets and release them at a multiple of a time quantum.
This feature can be used to prevent timing attacks caused
by network latency.
Signed-off-by: Niclas Hedam <niclas@....am>
---
include/uapi/linux/pkt_sched.h | 2 ++
net/sched/sch_netem.c | 24 +++++++++++++++++++++---
2 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
index 79a699f106b1..1ba49f141dae 100644
--- a/include/uapi/linux/pkt_sched.h
+++ b/include/uapi/linux/pkt_sched.h
@@ -603,6 +603,7 @@ enum {
TCA_NETEM_JITTER64,
TCA_NETEM_SLOT,
TCA_NETEM_SLOT_DIST,
+ TCA_NETEM_BURSTING,
__TCA_NETEM_MAX,
};
@@ -615,6 +616,7 @@ struct tc_netem_qopt {
__u32 gap; /* re-ordering gap (0 for none) */
__u32 duplicate; /* random packet dup (0=none ~0=100%) */
__u32 jitter; /* random jitter in latency (us) */
+ __u32 bursting; /* send packets in bursts (us) */
};
struct tc_netem_corr {
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c
index 0c345e43a09a..52d796287b86 100644
--- a/net/sched/sch_netem.c
+++ b/net/sched/sch_netem.c
@@ -85,6 +85,7 @@ struct netem_sched_data {
s64 latency;
s64 jitter;
+ u32 bursting;
u32 loss;
u32 ecn;
u32 limit;
@@ -467,7 +468,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
/* If a delay is expected, orphan the skb. (orphaning usually takes
* place at TX completion time, so _before_ the link transit delay)
*/
- if (q->latency || q->jitter || q->rate)
+ if (q->latency || q->jitter || q->rate || q->bursting)
skb_orphan_partial(skb);
/*
@@ -527,8 +528,17 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch,
qdisc_qstats_backlog_inc(sch, skb);
cb = netem_skb_cb(skb);
- if (q->gap == 0 || /* not doing reordering */
- q->counter < q->gap - 1 || /* inside last reordering gap */
+ if (q->bursting > 0) {
+ u64 now;
+
+ now = ktime_get_ns();
+
+ cb->time_to_send = now - (now % q->bursting) + q->bursting;
+
+ ++q->counter;
+ tfifo_enqueue(skb, sch);
+ } else if (q->gap == 0 || /* not doing reordering */
+ q->counter < q->gap - 1 || /* inside last reordering gap */
q->reorder < get_crandom(&q->reorder_cor)) {
u64 now;
s64 delay;
@@ -927,6 +937,7 @@ static const struct nla_policy netem_policy[TCA_NETEM_MAX + 1] = {
[TCA_NETEM_ECN] = { .type = NLA_U32 },
[TCA_NETEM_RATE64] = { .type = NLA_U64 },
[TCA_NETEM_LATENCY64] = { .type = NLA_S64 },
+ [TCA_NETEM_BURSTING] = { .type = NLA_U64 },
[TCA_NETEM_JITTER64] = { .type = NLA_S64 },
[TCA_NETEM_SLOT] = { .len = sizeof(struct tc_netem_slot) },
};
@@ -1001,6 +1012,7 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt,
q->latency = PSCHED_TICKS2NS(qopt->latency);
q->jitter = PSCHED_TICKS2NS(qopt->jitter);
+ q->bursting = PSCHED_TICKS2NS(qopt->bursting);
q->limit = qopt->limit;
q->gap = qopt->gap;
q->counter = 0;
@@ -1032,6 +1044,9 @@ static int netem_change(struct Qdisc *sch, struct nlattr *opt,
if (tb[TCA_NETEM_LATENCY64])
q->latency = nla_get_s64(tb[TCA_NETEM_LATENCY64]);
+ if (tb[TCA_NETEM_BURSTING])
+ q->bursting = nla_get_u64(tb[TCA_NETEM_BURSTING]);
+
if (tb[TCA_NETEM_JITTER64])
q->jitter = nla_get_s64(tb[TCA_NETEM_JITTER64]);
@@ -1150,6 +1165,9 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb)
UINT_MAX);
qopt.jitter = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->jitter),
UINT_MAX);
+ qopt.bursting = min_t(psched_tdiff_t, PSCHED_NS2TICKS(q->bursting),
+ UINT_MAX);
+
qopt.limit = q->limit;
qopt.loss = q->loss;
qopt.gap = q->gap;
--
2.25.1
> On 27 Jun 2021, at 20:32, Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Fri, Jun 25, 2021 at 5:03 AM Niclas Hedam <nhed@....dk> wrote:
>> diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h
>> index 79a699f106b1..826d1dee6601 100644
>> --- a/include/uapi/linux/pkt_sched.h
>> +++ b/include/uapi/linux/pkt_sched.h
>> @@ -594,6 +594,7 @@ enum {
>> TCA_NETEM_DELAY_DIST,
>> TCA_NETEM_REORDER,
>> TCA_NETEM_CORRUPT,
>> + TCA_NETEM_BURSTING,
>> TCA_NETEM_LOSS,
>> TCA_NETEM_RATE,
>> TCA_NETEM_ECN,
>
> You can't add a new enum in the middle, as it is UAPI.
>
> Thanks.
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