Commit 0a7fad23 authored by Petr Machata's avatar Petr Machata Committed by David S. Miller
Browse files

net: sched: RED: Introduce an ECN nodrop mode 



When the RED Qdisc is currently configured to enable ECN, the RED algorithm
is used to decide whether a certain SKB should be marked. If that SKB is
not ECN-capable, it is early-dropped.

It is also possible to keep all traffic in the queue, and just mark the
ECN-capable subset of it, as appropriate under the RED algorithm. Some
switches support this mode, and some installations make use of it.

To that end, add a new RED flag, TC_RED_NODROP. When the Qdisc is
configured with this flag, non-ECT traffic is enqueued instead of being
early-dropped.

Signed-off-by: default avatarPetr Machata <petrm@mellanox.com>
Reviewed-by: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 14bc175d

include/net/pkt_cls.h

+1 −0
Original line number Diff line number Diff line
@@ -740,6 +740,7 @@ struct tc_red_qopt_offload_params { 
	u32 limit;

	bool is_ecn;

	bool is_harddrop;

	bool is_nodrop;

	struct gnet_stats_queue *qstats;

};

include/net/red.h

+5 −0
Original line number Diff line number Diff line
@@ -209,6 +209,11 @@ static inline int red_get_flags(unsigned char qopt_flags, 
static inline int red_validate_flags(unsigned char flags,

				     struct netlink_ext_ack *extack)

{

	if ((flags & TC_RED_NODROP) && !(flags & TC_RED_ECN)) {

		NL_SET_ERR_MSG_MOD(extack, "nodrop mode is only meaningful with ECN");

		return -EINVAL;

	}



	return 0;

}

include/uapi/linux/pkt_sched.h

+1 −0
Original line number Diff line number Diff line
@@ -286,6 +286,7 @@ struct tc_red_qopt { 
#define TC_RED_ECN		1

#define TC_RED_HARDDROP		2

#define TC_RED_ADAPTATIVE	4

#define TC_RED_NODROP		8

};



#define TC_RED_HISTORIC_FLAGS (TC_RED_ECN | TC_RED_HARDDROP | TC_RED_ADAPTATIVE)

net/sched/sch_red.c

+25 −6
Original line number Diff line number Diff line
@@ -48,7 +48,7 @@ struct red_sched_data { 
	struct Qdisc		*qdisc;

};



static const u32 red_supported_flags = TC_RED_HISTORIC_FLAGS;

static const u32 red_supported_flags = TC_RED_HISTORIC_FLAGS | TC_RED_NODROP;



static inline int red_use_ecn(struct red_sched_data *q)

{
@@ -60,6 +60,11 @@ static inline int red_use_harddrop(struct red_sched_data *q) 
	return q->flags & TC_RED_HARDDROP;

}



static int red_use_nodrop(struct red_sched_data *q)

{

	return q->flags & TC_RED_NODROP;

}



static int red_enqueue(struct sk_buff *skb, struct Qdisc *sch,

		       struct sk_buff **to_free)

{
@@ -80,23 +85,36 @@ static int red_enqueue(struct sk_buff *skb, struct Qdisc *sch, 


	case RED_PROB_MARK:

		qdisc_qstats_overlimit(sch);

		if (!red_use_ecn(q) || !INET_ECN_set_ce(skb)) {

		if (!red_use_ecn(q)) {

			q->stats.prob_drop++;

			goto congestion_drop;

		}



		if (INET_ECN_set_ce(skb)) {

			q->stats.prob_mark++;

		} else if (!red_use_nodrop(q)) {

			q->stats.prob_drop++;

			goto congestion_drop;

		}



		/* Non-ECT packet in ECN nodrop mode: queue it. */

		break;



	case RED_HARD_MARK:

		qdisc_qstats_overlimit(sch);

		if (red_use_harddrop(q) || !red_use_ecn(q) ||

		    !INET_ECN_set_ce(skb)) {

		if (red_use_harddrop(q) || !red_use_ecn(q)) {

			q->stats.forced_drop++;

			goto congestion_drop;

		}



		if (INET_ECN_set_ce(skb)) {

			q->stats.forced_mark++;

		} else if (!red_use_nodrop(q)) {

			q->stats.forced_drop++;

			goto congestion_drop;

		}



		/* Non-ECT packet in ECN nodrop mode: queue it. */

		break;

	}
@@ -171,6 +189,7 @@ static int red_offload(struct Qdisc *sch, bool enable) 
		opt.set.limit = q->limit;

		opt.set.is_ecn = red_use_ecn(q);

		opt.set.is_harddrop = red_use_harddrop(q);

		opt.set.is_nodrop = red_use_nodrop(q);

		opt.set.qstats = &sch->qstats;

	} else {

		opt.command = TC_RED_DESTROY;

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