From 39d010504e6b4485d7ceee167743620dd33f4417 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Fri, 1 May 2020 07:07:41 -0700 Subject: net_sched: sch_fq: add horizon attribute QUIC servers would like to use SO_TXTIME, without having CAP_NET_ADMIN, to efficiently pace UDP packets. As far as sch_fq is concerned, we need to add safety checks, so that a buggy application does not fill the qdisc with packets having delivery time far in the future. This patch adds a configurable horizon (default: 10 seconds), and a configurable policy when a packet is beyond the horizon at enqueue() time: - either drop the packet (default policy) - or cap its delivery time to the horizon. $ tc -s -d qd sh dev eth0 qdisc fq 8022: root refcnt 257 limit 10000p flow_limit 100p buckets 1024 orphan_mask 1023 quantum 10Kb initial_quantum 51160b low_rate_threshold 550Kbit refill_delay 40.0ms timer_slack 10.000us horizon 10.000s Sent 1234215879 bytes 837099 pkt (dropped 21, overlimits 0 requeues 6) backlog 0b 0p requeues 6 flows 1191 (inactive 1177 throttled 0) gc 0 highprio 0 throttled 692 latency 11.480us pkts_too_long 0 alloc_errors 0 horizon_drops 21 horizon_caps 0 v2: fixed an overflow on 32bit kernels in fq_init(), reported by kbuild test robot Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Signed-off-by: David S. Miller --- include/uapi/linux/pkt_sched.h | 6 +++++ net/sched/sch_fq.c | 59 ++++++++++++++++++++++++++++++++++++++---- 2 files changed, 60 insertions(+), 5 deletions(-) diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index 0c02737c8f47..a95f3ae7ab37 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -913,6 +913,10 @@ enum { TCA_FQ_TIMER_SLACK, /* timer slack */ + TCA_FQ_HORIZON, /* time horizon in us */ + + TCA_FQ_HORIZON_DROP, /* drop packets beyond horizon, or cap their EDT */ + __TCA_FQ_MAX }; @@ -932,6 +936,8 @@ struct tc_fq_qd_stats { __u32 throttled_flows; __u32 unthrottle_latency_ns; __u64 ce_mark; /* packets above ce_threshold */ + __u64 horizon_drops; + __u64 horizon_caps; }; /* Heavy-Hitter Filter */ diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c index 4f0104243cc2..8f06a808c59a 100644 --- a/net/sched/sch_fq.c +++ b/net/sched/sch_fq.c @@ -100,6 +100,7 @@ struct fq_sched_data { struct rb_root delayed; /* for rate limited flows */ u64 time_next_delayed_flow; + u64 ktime_cache; /* copy of last ktime_get_ns() */ unsigned long unthrottle_latency_ns; struct fq_flow internal; /* for non classified or high prio packets */ @@ -109,12 +110,13 @@ struct fq_sched_data { u32 flow_plimit; /* max packets per flow */ unsigned long flow_max_rate; /* optional max rate per flow */ u64 ce_threshold; + u64 horizon; /* horizon in ns */ u32 orphan_mask; /* mask for orphaned skb */ u32 low_rate_threshold; struct rb_root *fq_root; u8 rate_enable; u8 fq_trees_log; - + u8 horizon_drop; u32 flows; u32 inactive_flows; u32 throttled_flows; @@ -123,6 +125,8 @@ struct fq_sched_data { u64 stat_internal_packets; u64 stat_throttled; u64 stat_ce_mark; + u64 stat_horizon_drops; + u64 stat_horizon_caps; u64 stat_flows_plimit; u64 stat_pkts_too_long; u64 stat_allocation_errors; @@ -402,8 +406,6 @@ static void flow_queue_add(struct fq_flow *flow, struct sk_buff *skb) struct rb_node **p, *parent; struct sk_buff *head, *aux; - fq_skb_cb(skb)->time_to_send = skb->tstamp ?: ktime_get_ns(); - head = flow->head; if (!head || fq_skb_cb(skb)->time_to_send >= fq_skb_cb(flow->tail)->time_to_send) { @@ -431,6 +433,12 @@ static void flow_queue_add(struct fq_flow *flow, struct sk_buff *skb) rb_insert_color(&skb->rbnode, &flow->t_root); } +static bool fq_packet_beyond_horizon(const struct sk_buff *skb, + const struct fq_sched_data *q) +{ + return unlikely((s64)skb->tstamp > (s64)(q->ktime_cache + q->horizon)); +} + static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free) { @@ -440,6 +448,28 @@ static int fq_enqueue(struct sk_buff *skb, struct Qdisc *sch, if (unlikely(sch->q.qlen >= sch->limit)) return qdisc_drop(skb, sch, to_free); + if (!skb->tstamp) { + fq_skb_cb(skb)->time_to_send = q->ktime_cache = ktime_get_ns(); + } else { + /* Check if packet timestamp is too far in the future. + * Try first if our cached value, to avoid ktime_get_ns() + * cost in most cases. + */ + if (fq_packet_beyond_horizon(skb, q)) { + /* Refresh our cache and check another time */ + q->ktime_cache = ktime_get_ns(); + if (fq_packet_beyond_horizon(skb, q)) { + if (q->horizon_drop) { + q->stat_horizon_drops++; + return qdisc_drop(skb, sch, to_free); + } + q->stat_horizon_caps++; + skb->tstamp = q->ktime_cache + q->horizon; + } + } + fq_skb_cb(skb)->time_to_send = skb->tstamp; + } + f = fq_classify(skb, q); if (unlikely(f->qlen >= q->flow_plimit && f != &q->internal)) { q->stat_flows_plimit++; @@ -512,7 +542,7 @@ static struct sk_buff *fq_dequeue(struct Qdisc *sch) goto out; } - now = ktime_get_ns(); + q->ktime_cache = now = ktime_get_ns(); fq_check_throttled(q, now); begin: head = &q->new_flows; @@ -765,6 +795,8 @@ static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = { [TCA_FQ_LOW_RATE_THRESHOLD] = { .type = NLA_U32 }, [TCA_FQ_CE_THRESHOLD] = { .type = NLA_U32 }, [TCA_FQ_TIMER_SLACK] = { .type = NLA_U32 }, + [TCA_FQ_HORIZON] = { .type = NLA_U32 }, + [TCA_FQ_HORIZON_DROP] = { .type = NLA_U8 }, }; static int fq_change(struct Qdisc *sch, struct nlattr *opt, @@ -854,7 +886,15 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt, if (tb[TCA_FQ_TIMER_SLACK]) q->timer_slack = nla_get_u32(tb[TCA_FQ_TIMER_SLACK]); + if (tb[TCA_FQ_HORIZON]) + q->horizon = (u64)NSEC_PER_USEC * + nla_get_u32(tb[TCA_FQ_HORIZON]); + + if (tb[TCA_FQ_HORIZON_DROP]) + q->horizon_drop = nla_get_u8(tb[TCA_FQ_HORIZON_DROP]); + if (!err) { + sch_tree_unlock(sch); err = fq_resize(sch, fq_log); sch_tree_lock(sch); @@ -907,6 +947,9 @@ static int fq_init(struct Qdisc *sch, struct nlattr *opt, q->timer_slack = 10 * NSEC_PER_USEC; /* 10 usec of hrtimer slack */ + q->horizon = 10ULL * NSEC_PER_SEC; /* 10 seconds */ + q->horizon_drop = 1; /* by default, drop packets beyond horizon */ + /* Default ce_threshold of 4294 seconds */ q->ce_threshold = (u64)NSEC_PER_USEC * ~0U; @@ -924,6 +967,7 @@ static int fq_dump(struct Qdisc *sch, struct sk_buff *skb) { struct fq_sched_data *q = qdisc_priv(sch); u64 ce_threshold = q->ce_threshold; + u64 horizon = q->horizon; struct nlattr *opts; opts = nla_nest_start_noflag(skb, TCA_OPTIONS); @@ -933,6 +977,7 @@ static int fq_dump(struct Qdisc *sch, struct sk_buff *skb) /* TCA_FQ_FLOW_DEFAULT_RATE is not used anymore */ do_div(ce_threshold, NSEC_PER_USEC); + do_div(horizon, NSEC_PER_USEC); if (nla_put_u32(skb, TCA_FQ_PLIMIT, sch->limit) || nla_put_u32(skb, TCA_FQ_FLOW_PLIMIT, q->flow_plimit) || @@ -948,7 +993,9 @@ static int fq_dump(struct Qdisc *sch, struct sk_buff *skb) q->low_rate_threshold) || nla_put_u32(skb, TCA_FQ_CE_THRESHOLD, (u32)ce_threshold) || nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log) || - nla_put_u32(skb, TCA_FQ_TIMER_SLACK, q->timer_slack)) + nla_put_u32(skb, TCA_FQ_TIMER_SLACK, q->timer_slack) || + nla_put_u32(skb, TCA_FQ_HORIZON, (u32)horizon) || + nla_put_u8(skb, TCA_FQ_HORIZON_DROP, q->horizon_drop)) goto nla_put_failure; return nla_nest_end(skb, opts); @@ -979,6 +1026,8 @@ static int fq_dump_stats(struct Qdisc *sch, struct gnet_dump *d) st.unthrottle_latency_ns = min_t(unsigned long, q->unthrottle_latency_ns, ~0U); st.ce_mark = q->stat_ce_mark; + st.horizon_drops = q->stat_horizon_drops; + st.horizon_caps = q->stat_horizon_caps; sch_tree_unlock(sch); return gnet_stats_copy_app(d, &st, sizeof(st)); -- cgit v1.2.3-59-g8ed1b