From 0a7fad2376ba6b37c6b1a1072ed2a2381d82cd18 Mon Sep 17 00:00:00 2001 From: Petr Machata Date: Fri, 13 Mar 2020 01:10:57 +0200 Subject: 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: Petr Machata Reviewed-by: Jakub Kicinski Signed-off-by: David S. Miller --- include/net/pkt_cls.h | 1 + include/net/red.h | 5 +++++ include/uapi/linux/pkt_sched.h | 1 + net/sched/sch_red.c | 31 +++++++++++++++++++++++++------ 4 files changed, 32 insertions(+), 6 deletions(-) diff --git a/include/net/pkt_cls.h b/include/net/pkt_cls.h index dbc89452f90b..1db8b27d4515 100644 --- a/include/net/pkt_cls.h +++ b/include/net/pkt_cls.h @@ -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; }; diff --git a/include/net/red.h b/include/net/red.h index 6a2aaa6c7c41..fc455445f4b2 100644 --- a/include/net/red.h +++ b/include/net/red.h @@ -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; } diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index 6325507935ea..ea39287d59c8 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -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) diff --git a/net/sched/sch_red.c b/net/sched/sch_red.c index d4ce111704dc..3ef0a4f7399b 100644 --- a/net/sched/sch_red.c +++ b/net/sched/sch_red.c @@ -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; } - q->stats.prob_mark++; + 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; } - q->stats.forced_mark++; + /* 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; -- cgit v1.2.3