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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , linux-kernel@vger.kernel.org (open list) Subject: [PATCH v4 5/5] net/sched: netem: add per-impairment extended statistics Date: Thu, 7 May 2026 18:55:21 -0700 Message-ID: <20260508015940.554462-6-stephen@networkplumber.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260508015940.554462-1-stephen@networkplumber.org> References: <20260508015940.554462-1-stephen@networkplumber.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Adds new counters that keep track of when netem applied impairments (delay, loss, corruption, duplication, reordering). Add a struct tc_netem_xstats reported via TCA_STATS_APP so that userspace (tc -s qdisc show) can display per-impairment counters. The READ_ONCE/WRITE_ONCE pairing here matches the model used elsewhere for xstats in the qdisc layer. Also fixes a pre-existing accounting bug: ECN CE-marked packets were being counted as drops (that is not what other qdisc's do). Instead, now that there is a proper ecn_marked counter, the spurious qdisc_qstats_drop() call can be removed. Signed-off-by: Stephen Hemminger --- Note to reviewers. The READ_ONCE/WRITE_ONCE pattern is allowed. For some reason current AI prompts are obsessed with complaining about 64 bit torn read/write on these, since the counters are informational only, any such complaints are false positive. Addition to iproute2 will be sent seperately. include/uapi/linux/pkt_sched.h | 9 +++++++++ net/sched/sch_netem.c | 37 ++++++++++++++++++++++++++++++++-- 2 files changed, 44 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/pkt_sched.h b/include/uapi/linux/pkt_sched.h index 66e8072f44df..1c84c8076e22 100644 --- a/include/uapi/linux/pkt_sched.h +++ b/include/uapi/linux/pkt_sched.h @@ -569,6 +569,15 @@ struct tc_netem_gemodel { #define NETEM_DIST_SCALE 8192 #define NETEM_DIST_MAX 16384 +struct tc_netem_xstats { + __u64 delayed; /* packets delayed */ + __u64 dropped; /* packets dropped by loss model */ + __u64 corrupted; /* packets with bit errors injected */ + __u64 duplicated; /* duplicate packets generated */ + __u64 reordered; /* packets sent out of order */ + __u64 ecn_marked; /* packets ECN CE-marked (not dropped)*/ +}; + /* DRR */ enum { diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 37df05bf43ee..6d8f4c4cedf3 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -152,6 +152,14 @@ struct netem_sched_data { u8 state; } clg; + /* Impairment counters */ + u64 delayed; + u64 dropped; + u64 corrupted; + u64 duplicated; + u64 ecn_marked; + u64 reordered; + /* Cold tail: slot reschedule config and the watchdog timer. */ struct tc_netem_slot slot_config; struct qdisc_watchdog watchdog; @@ -462,17 +470,21 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, skb->prev = NULL; /* Random duplication */ - if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor, &q->prng)) + if (q->duplicate && q->duplicate >= get_crandom(&q->dup_cor, &q->prng)) { ++count; + WRITE_ONCE(q->duplicated, q->duplicated + 1); + } /* Drop packet? */ if (loss_event(q)) { if (q->ecn && INET_ECN_set_ce(skb)) - qdisc_qstats_drop(sch); /* mark packet */ + WRITE_ONCE(q->ecn_marked, q->ecn_marked + 1); else --count; } + if (count == 0) { + WRITE_ONCE(q->dropped, q->dropped + 1); qdisc_qstats_drop(sch); __qdisc_drop(skb, to_free); return NET_XMIT_SUCCESS | __NET_XMIT_BYPASS; @@ -523,6 +535,7 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, if (skb->len) { u32 offset = get_random_u32_below(skb->len); skb->data[offset] ^= 1 << get_random_u32_below(8); + WRITE_ONCE(q->corrupted, q->corrupted + 1); } } @@ -604,12 +617,16 @@ static int netem_enqueue(struct sk_buff *skb, struct Qdisc *sch, cb->time_to_send = now + delay; ++q->counter; + if (delay) + WRITE_ONCE(q->delayed, q->delayed + 1); + tfifo_enqueue(skb, sch); } else { /* * Do re-ordering by putting one out of N packets at the front * of the queue. */ + WRITE_ONCE(q->reordered, q->reordered + 1); cb->time_to_send = ktime_get_ns(); q->counter = 0; @@ -1350,6 +1367,21 @@ static int netem_dump(struct Qdisc *sch, struct sk_buff *skb) return -1; } +static int netem_dump_stats(struct Qdisc *sch, struct gnet_dump *d) +{ + struct netem_sched_data *q = qdisc_priv(sch); + struct tc_netem_xstats st = { + .delayed = READ_ONCE(q->delayed), + .dropped = READ_ONCE(q->dropped), + .corrupted = READ_ONCE(q->corrupted), + .duplicated = READ_ONCE(q->duplicated), + .reordered = READ_ONCE(q->reordered), + .ecn_marked = READ_ONCE(q->ecn_marked), + }; + + return gnet_stats_copy_app(d, &st, sizeof(st)); +} + static int netem_dump_class(struct Qdisc *sch, unsigned long cl, struct sk_buff *skb, struct tcmsg *tcm) { @@ -1412,6 +1444,7 @@ static struct Qdisc_ops netem_qdisc_ops __read_mostly = { .destroy = netem_destroy, .change = netem_change, .dump = netem_dump, + .dump_stats = netem_dump_stats, .owner = THIS_MODULE, }; MODULE_ALIAS_NET_SCH("netem"); -- 2.53.0