Adding upstream version 5.10.209.upstream/5.10.209

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 730 insertions, 0 deletions

diff --git a/net/sched/sch_fq_codel.c b/net/sched/sch_fq_codel.c
new file mode 100644
index 000000000..01d6eea5b
--- /dev/null
+++ b/net/sched/sch_fq_codel.c
@@ -0,0 +1,730 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Fair Queue CoDel discipline
+ *
+ *  Copyright (C) 2012,2015 Eric Dumazet <edumazet@google.com>
+ */
+
+#include <linux/module.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/jiffies.h>
+#include <linux/string.h>
+#include <linux/in.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/slab.h>
+#include <linux/vmalloc.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
+#include <net/codel.h>
+#include <net/codel_impl.h>
+#include <net/codel_qdisc.h>
+
+/*	Fair Queue CoDel.
+ *
+ * Principles :
+ * Packets are classified (internal classifier or external) on flows.
+ * This is a Stochastic model (as we use a hash, several flows
+ *			       might be hashed on same slot)
+ * Each flow has a CoDel managed queue.
+ * Flows are linked onto two (Round Robin) lists,
+ * so that new flows have priority on old ones.
+ *
+ * For a given flow, packets are not reordered (CoDel uses a FIFO)
+ * head drops only.
+ * ECN capability is on by default.
+ * Low memory footprint (64 bytes per flow)
+ */
+
+struct fq_codel_flow {
+	struct sk_buff	  *head;
+	struct sk_buff	  *tail;
+	struct list_head  flowchain;
+	int		  deficit;
+	struct codel_vars cvars;
+}; /* please try to keep this structure <= 64 bytes */
+
+struct fq_codel_sched_data {
+	struct tcf_proto __rcu *filter_list; /* optional external classifier */
+	struct tcf_block *block;
+	struct fq_codel_flow *flows;	/* Flows table [flows_cnt] */
+	u32		*backlogs;	/* backlog table [flows_cnt] */
+	u32		flows_cnt;	/* number of flows */
+	u32		quantum;	/* psched_mtu(qdisc_dev(sch)); */
+	u32		drop_batch_size;
+	u32		memory_limit;
+	struct codel_params cparams;
+	struct codel_stats cstats;
+	u32		memory_usage;
+	u32		drop_overmemory;
+	u32		drop_overlimit;
+	u32		new_flow_count;
+
+	struct list_head new_flows;	/* list of new flows */
+	struct list_head old_flows;	/* list of old flows */
+};
+
+static unsigned int fq_codel_hash(const struct fq_codel_sched_data *q,
+				  struct sk_buff *skb)
+{
+	return reciprocal_scale(skb_get_hash(skb), q->flows_cnt);
+}
+
+static unsigned int fq_codel_classify(struct sk_buff *skb, struct Qdisc *sch,
+				      int *qerr)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	struct tcf_proto *filter;
+	struct tcf_result res;
+	int result;
+
+	if (TC_H_MAJ(skb->priority) == sch->handle &&
+	    TC_H_MIN(skb->priority) > 0 &&
+	    TC_H_MIN(skb->priority) <= q->flows_cnt)
+		return TC_H_MIN(skb->priority);
+
+	filter = rcu_dereference_bh(q->filter_list);
+	if (!filter)
+		return fq_codel_hash(q, skb) + 1;
+
+	*qerr = NET_XMIT_SUCCESS | __NET_XMIT_BYPASS;
+	result = tcf_classify(skb, filter, &res, false);
+	if (result >= 0) {
+#ifdef CONFIG_NET_CLS_ACT
+		switch (result) {
+		case TC_ACT_STOLEN:
+		case TC_ACT_QUEUED:
+		case TC_ACT_TRAP:
+			*qerr = NET_XMIT_SUCCESS | __NET_XMIT_STOLEN;
+			fallthrough;
+		case TC_ACT_SHOT:
+			return 0;
+		}
+#endif
+		if (TC_H_MIN(res.classid) <= q->flows_cnt)
+			return TC_H_MIN(res.classid);
+	}
+	return 0;
+}
+
+/* helper functions : might be changed when/if skb use a standard list_head */
+
+/* remove one skb from head of slot queue */
+static inline struct sk_buff *dequeue_head(struct fq_codel_flow *flow)
+{
+	struct sk_buff *skb = flow->head;
+
+	flow->head = skb->next;
+	skb_mark_not_on_list(skb);
+	return skb;
+}
+
+/* add skb to flow queue (tail add) */
+static inline void flow_queue_add(struct fq_codel_flow *flow,
+				  struct sk_buff *skb)
+{
+	if (flow->head == NULL)
+		flow->head = skb;
+	else
+		flow->tail->next = skb;
+	flow->tail = skb;
+	skb->next = NULL;
+}
+
+static unsigned int fq_codel_drop(struct Qdisc *sch, unsigned int max_packets,
+				  struct sk_buff **to_free)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *skb;
+	unsigned int maxbacklog = 0, idx = 0, i, len;
+	struct fq_codel_flow *flow;
+	unsigned int threshold;
+	unsigned int mem = 0;
+
+	/* Queue is full! Find the fat flow and drop packet(s) from it.
+	 * This might sound expensive, but with 1024 flows, we scan
+	 * 4KB of memory, and we dont need to handle a complex tree
+	 * in fast path (packet queue/enqueue) with many cache misses.
+	 * In stress mode, we'll try to drop 64 packets from the flow,
+	 * amortizing this linear lookup to one cache line per drop.
+	 */
+	for (i = 0; i < q->flows_cnt; i++) {
+		if (q->backlogs[i] > maxbacklog) {
+			maxbacklog = q->backlogs[i];
+			idx = i;
+		}
+	}
+
+	/* Our goal is to drop half of this fat flow backlog */
+	threshold = maxbacklog >> 1;
+
+	flow = &q->flows[idx];
+	len = 0;
+	i = 0;
+	do {
+		skb = dequeue_head(flow);
+		len += qdisc_pkt_len(skb);
+		mem += get_codel_cb(skb)->mem_usage;
+		__qdisc_drop(skb, to_free);
+	} while (++i < max_packets && len < threshold);
+
+	/* Tell codel to increase its signal strength also */
+	flow->cvars.count += i;
+	q->backlogs[idx] -= len;
+	q->memory_usage -= mem;
+	sch->qstats.drops += i;
+	sch->qstats.backlog -= len;
+	sch->q.qlen -= i;
+	return idx;
+}
+
+static int fq_codel_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+			    struct sk_buff **to_free)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	unsigned int idx, prev_backlog, prev_qlen;
+	struct fq_codel_flow *flow;
+	int ret;
+	unsigned int pkt_len;
+	bool memory_limited;
+
+	idx = fq_codel_classify(skb, sch, &ret);
+	if (idx == 0) {
+		if (ret & __NET_XMIT_BYPASS)
+			qdisc_qstats_drop(sch);
+		__qdisc_drop(skb, to_free);
+		return ret;
+	}
+	idx--;
+
+	codel_set_enqueue_time(skb);
+	flow = &q->flows[idx];
+	flow_queue_add(flow, skb);
+	q->backlogs[idx] += qdisc_pkt_len(skb);
+	qdisc_qstats_backlog_inc(sch, skb);
+
+	if (list_empty(&flow->flowchain)) {
+		list_add_tail(&flow->flowchain, &q->new_flows);
+		q->new_flow_count++;
+		flow->deficit = q->quantum;
+	}
+	get_codel_cb(skb)->mem_usage = skb->truesize;
+	q->memory_usage += get_codel_cb(skb)->mem_usage;
+	memory_limited = q->memory_usage > q->memory_limit;
+	if (++sch->q.qlen <= sch->limit && !memory_limited)
+		return NET_XMIT_SUCCESS;
+
+	prev_backlog = sch->qstats.backlog;
+	prev_qlen = sch->q.qlen;
+
+	/* save this packet length as it might be dropped by fq_codel_drop() */
+	pkt_len = qdisc_pkt_len(skb);
+	/* fq_codel_drop() is quite expensive, as it performs a linear search
+	 * in q->backlogs[] to find a fat flow.
+	 * So instead of dropping a single packet, drop half of its backlog
+	 * with a 64 packets limit to not add a too big cpu spike here.
+	 */
+	ret = fq_codel_drop(sch, q->drop_batch_size, to_free);
+
+	prev_qlen -= sch->q.qlen;
+	prev_backlog -= sch->qstats.backlog;
+	q->drop_overlimit += prev_qlen;
+	if (memory_limited)
+		q->drop_overmemory += prev_qlen;
+
+	/* As we dropped packet(s), better let upper stack know this.
+	 * If we dropped a packet for this flow, return NET_XMIT_CN,
+	 * but in this case, our parents wont increase their backlogs.
+	 */
+	if (ret == idx) {
+		qdisc_tree_reduce_backlog(sch, prev_qlen - 1,
+					  prev_backlog - pkt_len);
+		return NET_XMIT_CN;
+	}
+	qdisc_tree_reduce_backlog(sch, prev_qlen, prev_backlog);
+	return NET_XMIT_SUCCESS;
+}
+
+/* This is the specific function called from codel_dequeue()
+ * to dequeue a packet from queue. Note: backlog is handled in
+ * codel, we dont need to reduce it here.
+ */
+static struct sk_buff *dequeue_func(struct codel_vars *vars, void *ctx)
+{
+	struct Qdisc *sch = ctx;
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	struct fq_codel_flow *flow;
+	struct sk_buff *skb = NULL;
+
+	flow = container_of(vars, struct fq_codel_flow, cvars);
+	if (flow->head) {
+		skb = dequeue_head(flow);
+		q->backlogs[flow - q->flows] -= qdisc_pkt_len(skb);
+		q->memory_usage -= get_codel_cb(skb)->mem_usage;
+		sch->q.qlen--;
+		sch->qstats.backlog -= qdisc_pkt_len(skb);
+	}
+	return skb;
+}
+
+static void drop_func(struct sk_buff *skb, void *ctx)
+{
+	struct Qdisc *sch = ctx;
+
+	kfree_skb(skb);
+	qdisc_qstats_drop(sch);
+}
+
+static struct sk_buff *fq_codel_dequeue(struct Qdisc *sch)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *skb;
+	struct fq_codel_flow *flow;
+	struct list_head *head;
+
+begin:
+	head = &q->new_flows;
+	if (list_empty(head)) {
+		head = &q->old_flows;
+		if (list_empty(head))
+			return NULL;
+	}
+	flow = list_first_entry(head, struct fq_codel_flow, flowchain);
+
+	if (flow->deficit <= 0) {
+		flow->deficit += q->quantum;
+		list_move_tail(&flow->flowchain, &q->old_flows);
+		goto begin;
+	}
+
+	skb = codel_dequeue(sch, &sch->qstats.backlog, &q->cparams,
+			    &flow->cvars, &q->cstats, qdisc_pkt_len,
+			    codel_get_enqueue_time, drop_func, dequeue_func);
+
+	if (!skb) {
+		/* force a pass through old_flows to prevent starvation */
+		if ((head == &q->new_flows) && !list_empty(&q->old_flows))
+			list_move_tail(&flow->flowchain, &q->old_flows);
+		else
+			list_del_init(&flow->flowchain);
+		goto begin;
+	}
+	qdisc_bstats_update(sch, skb);
+	flow->deficit -= qdisc_pkt_len(skb);
+	/* We cant call qdisc_tree_reduce_backlog() if our qlen is 0,
+	 * or HTB crashes. Defer it for next round.
+	 */
+	if (q->cstats.drop_count && sch->q.qlen) {
+		qdisc_tree_reduce_backlog(sch, q->cstats.drop_count,
+					  q->cstats.drop_len);
+		q->cstats.drop_count = 0;
+		q->cstats.drop_len = 0;
+	}
+	return skb;
+}
+
+static void fq_codel_flow_purge(struct fq_codel_flow *flow)
+{
+	rtnl_kfree_skbs(flow->head, flow->tail);
+	flow->head = NULL;
+}
+
+static void fq_codel_reset(struct Qdisc *sch)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	int i;
+
+	INIT_LIST_HEAD(&q->new_flows);
+	INIT_LIST_HEAD(&q->old_flows);
+	for (i = 0; i < q->flows_cnt; i++) {
+		struct fq_codel_flow *flow = q->flows + i;
+
+		fq_codel_flow_purge(flow);
+		INIT_LIST_HEAD(&flow->flowchain);
+		codel_vars_init(&flow->cvars);
+	}
+	memset(q->backlogs, 0, q->flows_cnt * sizeof(u32));
+	q->memory_usage = 0;
+}
+
+static const struct nla_policy fq_codel_policy[TCA_FQ_CODEL_MAX + 1] = {
+	[TCA_FQ_CODEL_TARGET]	= { .type = NLA_U32 },
+	[TCA_FQ_CODEL_LIMIT]	= { .type = NLA_U32 },
+	[TCA_FQ_CODEL_INTERVAL]	= { .type = NLA_U32 },
+	[TCA_FQ_CODEL_ECN]	= { .type = NLA_U32 },
+	[TCA_FQ_CODEL_FLOWS]	= { .type = NLA_U32 },
+	[TCA_FQ_CODEL_QUANTUM]	= { .type = NLA_U32 },
+	[TCA_FQ_CODEL_CE_THRESHOLD] = { .type = NLA_U32 },
+	[TCA_FQ_CODEL_DROP_BATCH_SIZE] = { .type = NLA_U32 },
+	[TCA_FQ_CODEL_MEMORY_LIMIT] = { .type = NLA_U32 },
+};
+
+static int fq_codel_change(struct Qdisc *sch, struct nlattr *opt,
+			   struct netlink_ext_ack *extack)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	struct nlattr *tb[TCA_FQ_CODEL_MAX + 1];
+	u32 quantum = 0;
+	int err;
+
+	if (!opt)
+		return -EINVAL;
+
+	err = nla_parse_nested_deprecated(tb, TCA_FQ_CODEL_MAX, opt,
+					  fq_codel_policy, NULL);
+	if (err < 0)
+		return err;
+	if (tb[TCA_FQ_CODEL_FLOWS]) {
+		if (q->flows)
+			return -EINVAL;
+		q->flows_cnt = nla_get_u32(tb[TCA_FQ_CODEL_FLOWS]);
+		if (!q->flows_cnt ||
+		    q->flows_cnt > 65536)
+			return -EINVAL;
+	}
+	if (tb[TCA_FQ_CODEL_QUANTUM]) {
+		quantum = max(256U, nla_get_u32(tb[TCA_FQ_CODEL_QUANTUM]));
+		if (quantum > FQ_CODEL_QUANTUM_MAX) {
+			NL_SET_ERR_MSG(extack, "Invalid quantum");
+			return -EINVAL;
+		}
+	}
+	sch_tree_lock(sch);
+
+	if (tb[TCA_FQ_CODEL_TARGET]) {
+		u64 target = nla_get_u32(tb[TCA_FQ_CODEL_TARGET]);
+
+		q->cparams.target = (target * NSEC_PER_USEC) >> CODEL_SHIFT;
+	}
+
+	if (tb[TCA_FQ_CODEL_CE_THRESHOLD]) {
+		u64 val = nla_get_u32(tb[TCA_FQ_CODEL_CE_THRESHOLD]);
+
+		q->cparams.ce_threshold = (val * NSEC_PER_USEC) >> CODEL_SHIFT;
+	}
+
+	if (tb[TCA_FQ_CODEL_INTERVAL]) {
+		u64 interval = nla_get_u32(tb[TCA_FQ_CODEL_INTERVAL]);
+
+		q->cparams.interval = (interval * NSEC_PER_USEC) >> CODEL_SHIFT;
+	}
+
+	if (tb[TCA_FQ_CODEL_LIMIT])
+		sch->limit = nla_get_u32(tb[TCA_FQ_CODEL_LIMIT]);
+
+	if (tb[TCA_FQ_CODEL_ECN])
+		q->cparams.ecn = !!nla_get_u32(tb[TCA_FQ_CODEL_ECN]);
+
+	if (quantum)
+		q->quantum = quantum;
+
+	if (tb[TCA_FQ_CODEL_DROP_BATCH_SIZE])
+		q->drop_batch_size = max(1U, nla_get_u32(tb[TCA_FQ_CODEL_DROP_BATCH_SIZE]));
+
+	if (tb[TCA_FQ_CODEL_MEMORY_LIMIT])
+		q->memory_limit = min(1U << 31, nla_get_u32(tb[TCA_FQ_CODEL_MEMORY_LIMIT]));
+
+	while (sch->q.qlen > sch->limit ||
+	       q->memory_usage > q->memory_limit) {
+		struct sk_buff *skb = fq_codel_dequeue(sch);
+
+		q->cstats.drop_len += qdisc_pkt_len(skb);
+		rtnl_kfree_skbs(skb, skb);
+		q->cstats.drop_count++;
+	}
+	qdisc_tree_reduce_backlog(sch, q->cstats.drop_count, q->cstats.drop_len);
+	q->cstats.drop_count = 0;
+	q->cstats.drop_len = 0;
+
+	sch_tree_unlock(sch);
+	return 0;
+}
+
+static void fq_codel_destroy(struct Qdisc *sch)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+
+	tcf_block_put(q->block);
+	kvfree(q->backlogs);
+	kvfree(q->flows);
+}
+
+static int fq_codel_init(struct Qdisc *sch, struct nlattr *opt,
+			 struct netlink_ext_ack *extack)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	int i;
+	int err;
+
+	sch->limit = 10*1024;
+	q->flows_cnt = 1024;
+	q->memory_limit = 32 << 20; /* 32 MBytes */
+	q->drop_batch_size = 64;
+	q->quantum = psched_mtu(qdisc_dev(sch));
+	INIT_LIST_HEAD(&q->new_flows);
+	INIT_LIST_HEAD(&q->old_flows);
+	codel_params_init(&q->cparams);
+	codel_stats_init(&q->cstats);
+	q->cparams.ecn = true;
+	q->cparams.mtu = psched_mtu(qdisc_dev(sch));
+
+	if (opt) {
+		err = fq_codel_change(sch, opt, extack);
+		if (err)
+			goto init_failure;
+	}
+
+	err = tcf_block_get(&q->block, &q->filter_list, sch, extack);
+	if (err)
+		goto init_failure;
+
+	if (!q->flows) {
+		q->flows = kvcalloc(q->flows_cnt,
+				    sizeof(struct fq_codel_flow),
+				    GFP_KERNEL);
+		if (!q->flows) {
+			err = -ENOMEM;
+			goto init_failure;
+		}
+		q->backlogs = kvcalloc(q->flows_cnt, sizeof(u32), GFP_KERNEL);
+		if (!q->backlogs) {
+			err = -ENOMEM;
+			goto alloc_failure;
+		}
+		for (i = 0; i < q->flows_cnt; i++) {
+			struct fq_codel_flow *flow = q->flows + i;
+
+			INIT_LIST_HEAD(&flow->flowchain);
+			codel_vars_init(&flow->cvars);
+		}
+	}
+	if (sch->limit >= 1)
+		sch->flags |= TCQ_F_CAN_BYPASS;
+	else
+		sch->flags &= ~TCQ_F_CAN_BYPASS;
+	return 0;
+
+alloc_failure:
+	kvfree(q->flows);
+	q->flows = NULL;
+init_failure:
+	q->flows_cnt = 0;
+	return err;
+}
+
+static int fq_codel_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	struct nlattr *opts;
+
+	opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
+	if (opts == NULL)
+		goto nla_put_failure;
+
+	if (nla_put_u32(skb, TCA_FQ_CODEL_TARGET,
+			codel_time_to_us(q->cparams.target)) ||
+	    nla_put_u32(skb, TCA_FQ_CODEL_LIMIT,
+			sch->limit) ||
+	    nla_put_u32(skb, TCA_FQ_CODEL_INTERVAL,
+			codel_time_to_us(q->cparams.interval)) ||
+	    nla_put_u32(skb, TCA_FQ_CODEL_ECN,
+			q->cparams.ecn) ||
+	    nla_put_u32(skb, TCA_FQ_CODEL_QUANTUM,
+			q->quantum) ||
+	    nla_put_u32(skb, TCA_FQ_CODEL_DROP_BATCH_SIZE,
+			q->drop_batch_size) ||
+	    nla_put_u32(skb, TCA_FQ_CODEL_MEMORY_LIMIT,
+			q->memory_limit) ||
+	    nla_put_u32(skb, TCA_FQ_CODEL_FLOWS,
+			q->flows_cnt))
+		goto nla_put_failure;
+
+	if (q->cparams.ce_threshold != CODEL_DISABLED_THRESHOLD &&
+	    nla_put_u32(skb, TCA_FQ_CODEL_CE_THRESHOLD,
+			codel_time_to_us(q->cparams.ce_threshold)))
+		goto nla_put_failure;
+
+	return nla_nest_end(skb, opts);
+
+nla_put_failure:
+	return -1;
+}
+
+static int fq_codel_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	struct tc_fq_codel_xstats st = {
+		.type				= TCA_FQ_CODEL_XSTATS_QDISC,
+	};
+	struct list_head *pos;
+
+	st.qdisc_stats.maxpacket = q->cstats.maxpacket;
+	st.qdisc_stats.drop_overlimit = q->drop_overlimit;
+	st.qdisc_stats.ecn_mark = q->cstats.ecn_mark;
+	st.qdisc_stats.new_flow_count = q->new_flow_count;
+	st.qdisc_stats.ce_mark = q->cstats.ce_mark;
+	st.qdisc_stats.memory_usage  = q->memory_usage;
+	st.qdisc_stats.drop_overmemory = q->drop_overmemory;
+
+	sch_tree_lock(sch);
+	list_for_each(pos, &q->new_flows)
+		st.qdisc_stats.new_flows_len++;
+
+	list_for_each(pos, &q->old_flows)
+		st.qdisc_stats.old_flows_len++;
+	sch_tree_unlock(sch);
+
+	return gnet_stats_copy_app(d, &st, sizeof(st));
+}
+
+static struct Qdisc *fq_codel_leaf(struct Qdisc *sch, unsigned long arg)
+{
+	return NULL;
+}
+
+static unsigned long fq_codel_find(struct Qdisc *sch, u32 classid)
+{
+	return 0;
+}
+
+static unsigned long fq_codel_bind(struct Qdisc *sch, unsigned long parent,
+			      u32 classid)
+{
+	return 0;
+}
+
+static void fq_codel_unbind(struct Qdisc *q, unsigned long cl)
+{
+}
+
+static struct tcf_block *fq_codel_tcf_block(struct Qdisc *sch, unsigned long cl,
+					    struct netlink_ext_ack *extack)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+
+	if (cl)
+		return NULL;
+	return q->block;
+}
+
+static int fq_codel_dump_class(struct Qdisc *sch, unsigned long cl,
+			  struct sk_buff *skb, struct tcmsg *tcm)
+{
+	tcm->tcm_handle |= TC_H_MIN(cl);
+	return 0;
+}
+
+static int fq_codel_dump_class_stats(struct Qdisc *sch, unsigned long cl,
+				     struct gnet_dump *d)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	u32 idx = cl - 1;
+	struct gnet_stats_queue qs = { 0 };
+	struct tc_fq_codel_xstats xstats;
+
+	if (idx < q->flows_cnt) {
+		const struct fq_codel_flow *flow = &q->flows[idx];
+		const struct sk_buff *skb;
+
+		memset(&xstats, 0, sizeof(xstats));
+		xstats.type = TCA_FQ_CODEL_XSTATS_CLASS;
+		xstats.class_stats.deficit = flow->deficit;
+		xstats.class_stats.ldelay =
+			codel_time_to_us(flow->cvars.ldelay);
+		xstats.class_stats.count = flow->cvars.count;
+		xstats.class_stats.lastcount = flow->cvars.lastcount;
+		xstats.class_stats.dropping = flow->cvars.dropping;
+		if (flow->cvars.dropping) {
+			codel_tdiff_t delta = flow->cvars.drop_next -
+					      codel_get_time();
+
+			xstats.class_stats.drop_next = (delta >= 0) ?
+				codel_time_to_us(delta) :
+				-codel_time_to_us(-delta);
+		}
+		if (flow->head) {
+			sch_tree_lock(sch);
+			skb = flow->head;
+			while (skb) {
+				qs.qlen++;
+				skb = skb->next;
+			}
+			sch_tree_unlock(sch);
+		}
+		qs.backlog = q->backlogs[idx];
+		qs.drops = 0;
+	}
+	if (gnet_stats_copy_queue(d, NULL, &qs, qs.qlen) < 0)
+		return -1;
+	if (idx < q->flows_cnt)
+		return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
+	return 0;
+}
+
+static void fq_codel_walk(struct Qdisc *sch, struct qdisc_walker *arg)
+{
+	struct fq_codel_sched_data *q = qdisc_priv(sch);
+	unsigned int i;
+
+	if (arg->stop)
+		return;
+
+	for (i = 0; i < q->flows_cnt; i++) {
+		if (list_empty(&q->flows[i].flowchain) ||
+		    arg->count < arg->skip) {
+			arg->count++;
+			continue;
+		}
+		if (arg->fn(sch, i + 1, arg) < 0) {
+			arg->stop = 1;
+			break;
+		}
+		arg->count++;
+	}
+}
+
+static const struct Qdisc_class_ops fq_codel_class_ops = {
+	.leaf		=	fq_codel_leaf,
+	.find		=	fq_codel_find,
+	.tcf_block	=	fq_codel_tcf_block,
+	.bind_tcf	=	fq_codel_bind,
+	.unbind_tcf	=	fq_codel_unbind,
+	.dump		=	fq_codel_dump_class,
+	.dump_stats	=	fq_codel_dump_class_stats,
+	.walk		=	fq_codel_walk,
+};
+
+static struct Qdisc_ops fq_codel_qdisc_ops __read_mostly = {
+	.cl_ops		=	&fq_codel_class_ops,
+	.id		=	"fq_codel",
+	.priv_size	=	sizeof(struct fq_codel_sched_data),
+	.enqueue	=	fq_codel_enqueue,
+	.dequeue	=	fq_codel_dequeue,
+	.peek		=	qdisc_peek_dequeued,
+	.init		=	fq_codel_init,
+	.reset		=	fq_codel_reset,
+	.destroy	=	fq_codel_destroy,
+	.change		=	fq_codel_change,
+	.dump		=	fq_codel_dump,
+	.dump_stats =	fq_codel_dump_stats,
+	.owner		=	THIS_MODULE,
+};
+
+static int __init fq_codel_module_init(void)
+{
+	return register_qdisc(&fq_codel_qdisc_ops);
+}
+
+static void __exit fq_codel_module_exit(void)
+{
+	unregister_qdisc(&fq_codel_qdisc_ops);
+}
+
+module_init(fq_codel_module_init)
+module_exit(fq_codel_module_exit)
+MODULE_AUTHOR("Eric Dumazet");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Fair Queue CoDel discipline");