Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

1 files changed, 721 insertions, 0 deletions

diff --git a/net/sched/sch_hhf.c b/net/sched/sch_hhf.c
new file mode 100644
index 000000000..d26cd436c
--- /dev/null
+++ b/net/sched/sch_hhf.c
@@ -0,0 +1,721 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* net/sched/sch_hhf.c		Heavy-Hitter Filter (HHF)
+ *
+ * Copyright (C) 2013 Terry Lam <vtlam@google.com>
+ * Copyright (C) 2013 Nandita Dukkipati <nanditad@google.com>
+ */
+
+#include <linux/jiffies.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/vmalloc.h>
+#include <linux/siphash.h>
+#include <net/pkt_sched.h>
+#include <net/sock.h>
+
+/*	Heavy-Hitter Filter (HHF)
+ *
+ * Principles :
+ * Flows are classified into two buckets: non-heavy-hitter and heavy-hitter
+ * buckets. Initially, a new flow starts as non-heavy-hitter. Once classified
+ * as heavy-hitter, it is immediately switched to the heavy-hitter bucket.
+ * The buckets are dequeued by a Weighted Deficit Round Robin (WDRR) scheduler,
+ * in which the heavy-hitter bucket is served with less weight.
+ * In other words, non-heavy-hitters (e.g., short bursts of critical traffic)
+ * are isolated from heavy-hitters (e.g., persistent bulk traffic) and also have
+ * higher share of bandwidth.
+ *
+ * To capture heavy-hitters, we use the "multi-stage filter" algorithm in the
+ * following paper:
+ * [EV02] C. Estan and G. Varghese, "New Directions in Traffic Measurement and
+ * Accounting", in ACM SIGCOMM, 2002.
+ *
+ * Conceptually, a multi-stage filter comprises k independent hash functions
+ * and k counter arrays. Packets are indexed into k counter arrays by k hash
+ * functions, respectively. The counters are then increased by the packet sizes.
+ * Therefore,
+ *    - For a heavy-hitter flow: *all* of its k array counters must be large.
+ *    - For a non-heavy-hitter flow: some of its k array counters can be large
+ *      due to hash collision with other small flows; however, with high
+ *      probability, not *all* k counters are large.
+ *
+ * By the design of the multi-stage filter algorithm, the false negative rate
+ * (heavy-hitters getting away uncaptured) is zero. However, the algorithm is
+ * susceptible to false positives (non-heavy-hitters mistakenly classified as
+ * heavy-hitters).
+ * Therefore, we also implement the following optimizations to reduce false
+ * positives by avoiding unnecessary increment of the counter values:
+ *    - Optimization O1: once a heavy-hitter is identified, its bytes are not
+ *        accounted in the array counters. This technique is called "shielding"
+ *        in Section 3.3.1 of [EV02].
+ *    - Optimization O2: conservative update of counters
+ *                       (Section 3.3.2 of [EV02]),
+ *        New counter value = max {old counter value,
+ *                                 smallest counter value + packet bytes}
+ *
+ * Finally, we refresh the counters periodically since otherwise the counter
+ * values will keep accumulating.
+ *
+ * Once a flow is classified as heavy-hitter, we also save its per-flow state
+ * in an exact-matching flow table so that its subsequent packets can be
+ * dispatched to the heavy-hitter bucket accordingly.
+ *
+ *
+ * At a high level, this qdisc works as follows:
+ * Given a packet p:
+ *   - If the flow-id of p (e.g., TCP 5-tuple) is already in the exact-matching
+ *     heavy-hitter flow table, denoted table T, then send p to the heavy-hitter
+ *     bucket.
+ *   - Otherwise, forward p to the multi-stage filter, denoted filter F
+ *        + If F decides that p belongs to a non-heavy-hitter flow, then send p
+ *          to the non-heavy-hitter bucket.
+ *        + Otherwise, if F decides that p belongs to a new heavy-hitter flow,
+ *          then set up a new flow entry for the flow-id of p in the table T and
+ *          send p to the heavy-hitter bucket.
+ *
+ * In this implementation:
+ *   - T is a fixed-size hash-table with 1024 entries. Hash collision is
+ *     resolved by linked-list chaining.
+ *   - F has four counter arrays, each array containing 1024 32-bit counters.
+ *     That means 4 * 1024 * 32 bits = 16KB of memory.
+ *   - Since each array in F contains 1024 counters, 10 bits are sufficient to
+ *     index into each array.
+ *     Hence, instead of having four hash functions, we chop the 32-bit
+ *     skb-hash into three 10-bit chunks, and the remaining 10-bit chunk is
+ *     computed as XOR sum of those three chunks.
+ *   - We need to clear the counter arrays periodically; however, directly
+ *     memsetting 16KB of memory can lead to cache eviction and unwanted delay.
+ *     So by representing each counter by a valid bit, we only need to reset
+ *     4K of 1 bit (i.e. 512 bytes) instead of 16KB of memory.
+ *   - The Deficit Round Robin engine is taken from fq_codel implementation
+ *     (net/sched/sch_fq_codel.c). Note that wdrr_bucket corresponds to
+ *     fq_codel_flow in fq_codel implementation.
+ *
+ */
+
+/* Non-configurable parameters */
+#define HH_FLOWS_CNT	 1024  /* number of entries in exact-matching table T */
+#define HHF_ARRAYS_CNT	 4     /* number of arrays in multi-stage filter F */
+#define HHF_ARRAYS_LEN	 1024  /* number of counters in each array of F */
+#define HHF_BIT_MASK_LEN 10    /* masking 10 bits */
+#define HHF_BIT_MASK	 0x3FF /* bitmask of 10 bits */
+
+#define WDRR_BUCKET_CNT  2     /* two buckets for Weighted DRR */
+enum wdrr_bucket_idx {
+	WDRR_BUCKET_FOR_HH	= 0, /* bucket id for heavy-hitters */
+	WDRR_BUCKET_FOR_NON_HH	= 1  /* bucket id for non-heavy-hitters */
+};
+
+#define hhf_time_before(a, b)	\
+	(typecheck(u32, a) && typecheck(u32, b) && ((s32)((a) - (b)) < 0))
+
+/* Heavy-hitter per-flow state */
+struct hh_flow_state {
+	u32		 hash_id;	/* hash of flow-id (e.g. TCP 5-tuple) */
+	u32		 hit_timestamp;	/* last time heavy-hitter was seen */
+	struct list_head flowchain;	/* chaining under hash collision */
+};
+
+/* Weighted Deficit Round Robin (WDRR) scheduler */
+struct wdrr_bucket {
+	struct sk_buff	  *head;
+	struct sk_buff	  *tail;
+	struct list_head  bucketchain;
+	int		  deficit;
+};
+
+struct hhf_sched_data {
+	struct wdrr_bucket buckets[WDRR_BUCKET_CNT];
+	siphash_key_t	   perturbation;   /* hash perturbation */
+	u32		   quantum;        /* psched_mtu(qdisc_dev(sch)); */
+	u32		   drop_overlimit; /* number of times max qdisc packet
+					    * limit was hit
+					    */
+	struct list_head   *hh_flows;       /* table T (currently active HHs) */
+	u32		   hh_flows_limit;            /* max active HH allocs */
+	u32		   hh_flows_overlimit; /* num of disallowed HH allocs */
+	u32		   hh_flows_total_cnt;          /* total admitted HHs */
+	u32		   hh_flows_current_cnt;        /* total current HHs  */
+	u32		   *hhf_arrays[HHF_ARRAYS_CNT]; /* HH filter F */
+	u32		   hhf_arrays_reset_timestamp;  /* last time hhf_arrays
+							 * was reset
+							 */
+	unsigned long	   *hhf_valid_bits[HHF_ARRAYS_CNT]; /* shadow valid bits
+							     * of hhf_arrays
+							     */
+	/* Similar to the "new_flows" vs. "old_flows" concept in fq_codel DRR */
+	struct list_head   new_buckets; /* list of new buckets */
+	struct list_head   old_buckets; /* list of old buckets */
+
+	/* Configurable HHF parameters */
+	u32		   hhf_reset_timeout; /* interval to reset counter
+					       * arrays in filter F
+					       * (default 40ms)
+					       */
+	u32		   hhf_admit_bytes;   /* counter thresh to classify as
+					       * HH (default 128KB).
+					       * With these default values,
+					       * 128KB / 40ms = 25 Mbps
+					       * i.e., we expect to capture HHs
+					       * sending > 25 Mbps.
+					       */
+	u32		   hhf_evict_timeout; /* aging threshold to evict idle
+					       * HHs out of table T. This should
+					       * be large enough to avoid
+					       * reordering during HH eviction.
+					       * (default 1s)
+					       */
+	u32		   hhf_non_hh_weight; /* WDRR weight for non-HHs
+					       * (default 2,
+					       *  i.e., non-HH : HH = 2 : 1)
+					       */
+};
+
+static u32 hhf_time_stamp(void)
+{
+	return jiffies;
+}
+
+/* Looks up a heavy-hitter flow in a chaining list of table T. */
+static struct hh_flow_state *seek_list(const u32 hash,
+				       struct list_head *head,
+				       struct hhf_sched_data *q)
+{
+	struct hh_flow_state *flow, *next;
+	u32 now = hhf_time_stamp();
+
+	if (list_empty(head))
+		return NULL;
+
+	list_for_each_entry_safe(flow, next, head, flowchain) {
+		u32 prev = flow->hit_timestamp + q->hhf_evict_timeout;
+
+		if (hhf_time_before(prev, now)) {
+			/* Delete expired heavy-hitters, but preserve one entry
+			 * to avoid kzalloc() when next time this slot is hit.
+			 */
+			if (list_is_last(&flow->flowchain, head))
+				return NULL;
+			list_del(&flow->flowchain);
+			kfree(flow);
+			q->hh_flows_current_cnt--;
+		} else if (flow->hash_id == hash) {
+			return flow;
+		}
+	}
+	return NULL;
+}
+
+/* Returns a flow state entry for a new heavy-hitter.  Either reuses an expired
+ * entry or dynamically alloc a new entry.
+ */
+static struct hh_flow_state *alloc_new_hh(struct list_head *head,
+					  struct hhf_sched_data *q)
+{
+	struct hh_flow_state *flow;
+	u32 now = hhf_time_stamp();
+
+	if (!list_empty(head)) {
+		/* Find an expired heavy-hitter flow entry. */
+		list_for_each_entry(flow, head, flowchain) {
+			u32 prev = flow->hit_timestamp + q->hhf_evict_timeout;
+
+			if (hhf_time_before(prev, now))
+				return flow;
+		}
+	}
+
+	if (q->hh_flows_current_cnt >= q->hh_flows_limit) {
+		q->hh_flows_overlimit++;
+		return NULL;
+	}
+	/* Create new entry. */
+	flow = kzalloc(sizeof(struct hh_flow_state), GFP_ATOMIC);
+	if (!flow)
+		return NULL;
+
+	q->hh_flows_current_cnt++;
+	INIT_LIST_HEAD(&flow->flowchain);
+	list_add_tail(&flow->flowchain, head);
+
+	return flow;
+}
+
+/* Assigns packets to WDRR buckets.  Implements a multi-stage filter to
+ * classify heavy-hitters.
+ */
+static enum wdrr_bucket_idx hhf_classify(struct sk_buff *skb, struct Qdisc *sch)
+{
+	struct hhf_sched_data *q = qdisc_priv(sch);
+	u32 tmp_hash, hash;
+	u32 xorsum, filter_pos[HHF_ARRAYS_CNT], flow_pos;
+	struct hh_flow_state *flow;
+	u32 pkt_len, min_hhf_val;
+	int i;
+	u32 prev;
+	u32 now = hhf_time_stamp();
+
+	/* Reset the HHF counter arrays if this is the right time. */
+	prev = q->hhf_arrays_reset_timestamp + q->hhf_reset_timeout;
+	if (hhf_time_before(prev, now)) {
+		for (i = 0; i < HHF_ARRAYS_CNT; i++)
+			bitmap_zero(q->hhf_valid_bits[i], HHF_ARRAYS_LEN);
+		q->hhf_arrays_reset_timestamp = now;
+	}
+
+	/* Get hashed flow-id of the skb. */
+	hash = skb_get_hash_perturb(skb, &q->perturbation);
+
+	/* Check if this packet belongs to an already established HH flow. */
+	flow_pos = hash & HHF_BIT_MASK;
+	flow = seek_list(hash, &q->hh_flows[flow_pos], q);
+	if (flow) { /* found its HH flow */
+		flow->hit_timestamp = now;
+		return WDRR_BUCKET_FOR_HH;
+	}
+
+	/* Now pass the packet through the multi-stage filter. */
+	tmp_hash = hash;
+	xorsum = 0;
+	for (i = 0; i < HHF_ARRAYS_CNT - 1; i++) {
+		/* Split the skb_hash into three 10-bit chunks. */
+		filter_pos[i] = tmp_hash & HHF_BIT_MASK;
+		xorsum ^= filter_pos[i];
+		tmp_hash >>= HHF_BIT_MASK_LEN;
+	}
+	/* The last chunk is computed as XOR sum of other chunks. */
+	filter_pos[HHF_ARRAYS_CNT - 1] = xorsum ^ tmp_hash;
+
+	pkt_len = qdisc_pkt_len(skb);
+	min_hhf_val = ~0U;
+	for (i = 0; i < HHF_ARRAYS_CNT; i++) {
+		u32 val;
+
+		if (!test_bit(filter_pos[i], q->hhf_valid_bits[i])) {
+			q->hhf_arrays[i][filter_pos[i]] = 0;
+			__set_bit(filter_pos[i], q->hhf_valid_bits[i]);
+		}
+
+		val = q->hhf_arrays[i][filter_pos[i]] + pkt_len;
+		if (min_hhf_val > val)
+			min_hhf_val = val;
+	}
+
+	/* Found a new HH iff all counter values > HH admit threshold. */
+	if (min_hhf_val > q->hhf_admit_bytes) {
+		/* Just captured a new heavy-hitter. */
+		flow = alloc_new_hh(&q->hh_flows[flow_pos], q);
+		if (!flow) /* memory alloc problem */
+			return WDRR_BUCKET_FOR_NON_HH;
+		flow->hash_id = hash;
+		flow->hit_timestamp = now;
+		q->hh_flows_total_cnt++;
+
+		/* By returning without updating counters in q->hhf_arrays,
+		 * we implicitly implement "shielding" (see Optimization O1).
+		 */
+		return WDRR_BUCKET_FOR_HH;
+	}
+
+	/* Conservative update of HHF arrays (see Optimization O2). */
+	for (i = 0; i < HHF_ARRAYS_CNT; i++) {
+		if (q->hhf_arrays[i][filter_pos[i]] < min_hhf_val)
+			q->hhf_arrays[i][filter_pos[i]] = min_hhf_val;
+	}
+	return WDRR_BUCKET_FOR_NON_HH;
+}
+
+/* Removes one skb from head of bucket. */
+static struct sk_buff *dequeue_head(struct wdrr_bucket *bucket)
+{
+	struct sk_buff *skb = bucket->head;
+
+	bucket->head = skb->next;
+	skb_mark_not_on_list(skb);
+	return skb;
+}
+
+/* Tail-adds skb to bucket. */
+static void bucket_add(struct wdrr_bucket *bucket, struct sk_buff *skb)
+{
+	if (bucket->head == NULL)
+		bucket->head = skb;
+	else
+		bucket->tail->next = skb;
+	bucket->tail = skb;
+	skb->next = NULL;
+}
+
+static unsigned int hhf_drop(struct Qdisc *sch, struct sk_buff **to_free)
+{
+	struct hhf_sched_data *q = qdisc_priv(sch);
+	struct wdrr_bucket *bucket;
+
+	/* Always try to drop from heavy-hitters first. */
+	bucket = &q->buckets[WDRR_BUCKET_FOR_HH];
+	if (!bucket->head)
+		bucket = &q->buckets[WDRR_BUCKET_FOR_NON_HH];
+
+	if (bucket->head) {
+		struct sk_buff *skb = dequeue_head(bucket);
+
+		sch->q.qlen--;
+		qdisc_qstats_backlog_dec(sch, skb);
+		qdisc_drop(skb, sch, to_free);
+	}
+
+	/* Return id of the bucket from which the packet was dropped. */
+	return bucket - q->buckets;
+}
+
+static int hhf_enqueue(struct sk_buff *skb, struct Qdisc *sch,
+		       struct sk_buff **to_free)
+{
+	struct hhf_sched_data *q = qdisc_priv(sch);
+	enum wdrr_bucket_idx idx;
+	struct wdrr_bucket *bucket;
+	unsigned int prev_backlog;
+
+	idx = hhf_classify(skb, sch);
+
+	bucket = &q->buckets[idx];
+	bucket_add(bucket, skb);
+	qdisc_qstats_backlog_inc(sch, skb);
+
+	if (list_empty(&bucket->bucketchain)) {
+		unsigned int weight;
+
+		/* The logic of new_buckets vs. old_buckets is the same as
+		 * new_flows vs. old_flows in the implementation of fq_codel,
+		 * i.e., short bursts of non-HHs should have strict priority.
+		 */
+		if (idx == WDRR_BUCKET_FOR_HH) {
+			/* Always move heavy-hitters to old bucket. */
+			weight = 1;
+			list_add_tail(&bucket->bucketchain, &q->old_buckets);
+		} else {
+			weight = q->hhf_non_hh_weight;
+			list_add_tail(&bucket->bucketchain, &q->new_buckets);
+		}
+		bucket->deficit = weight * q->quantum;
+	}
+	if (++sch->q.qlen <= sch->limit)
+		return NET_XMIT_SUCCESS;
+
+	prev_backlog = sch->qstats.backlog;
+	q->drop_overlimit++;
+	/* Return Congestion Notification only if we dropped a packet from this
+	 * bucket.
+	 */
+	if (hhf_drop(sch, to_free) == idx)
+		return NET_XMIT_CN;
+
+	/* As we dropped a packet, better let upper stack know this. */
+	qdisc_tree_reduce_backlog(sch, 1, prev_backlog - sch->qstats.backlog);
+	return NET_XMIT_SUCCESS;
+}
+
+static struct sk_buff *hhf_dequeue(struct Qdisc *sch)
+{
+	struct hhf_sched_data *q = qdisc_priv(sch);
+	struct sk_buff *skb = NULL;
+	struct wdrr_bucket *bucket;
+	struct list_head *head;
+
+begin:
+	head = &q->new_buckets;
+	if (list_empty(head)) {
+		head = &q->old_buckets;
+		if (list_empty(head))
+			return NULL;
+	}
+	bucket = list_first_entry(head, struct wdrr_bucket, bucketchain);
+
+	if (bucket->deficit <= 0) {
+		int weight = (bucket - q->buckets == WDRR_BUCKET_FOR_HH) ?
+			      1 : q->hhf_non_hh_weight;
+
+		bucket->deficit += weight * q->quantum;
+		list_move_tail(&bucket->bucketchain, &q->old_buckets);
+		goto begin;
+	}
+
+	if (bucket->head) {
+		skb = dequeue_head(bucket);
+		sch->q.qlen--;
+		qdisc_qstats_backlog_dec(sch, skb);
+	}
+
+	if (!skb) {
+		/* Force a pass through old_buckets to prevent starvation. */
+		if ((head == &q->new_buckets) && !list_empty(&q->old_buckets))
+			list_move_tail(&bucket->bucketchain, &q->old_buckets);
+		else
+			list_del_init(&bucket->bucketchain);
+		goto begin;
+	}
+	qdisc_bstats_update(sch, skb);
+	bucket->deficit -= qdisc_pkt_len(skb);
+
+	return skb;
+}
+
+static void hhf_reset(struct Qdisc *sch)
+{
+	struct sk_buff *skb;
+
+	while ((skb = hhf_dequeue(sch)) != NULL)
+		rtnl_kfree_skbs(skb, skb);
+}
+
+static void hhf_destroy(struct Qdisc *sch)
+{
+	int i;
+	struct hhf_sched_data *q = qdisc_priv(sch);
+
+	for (i = 0; i < HHF_ARRAYS_CNT; i++) {
+		kvfree(q->hhf_arrays[i]);
+		kvfree(q->hhf_valid_bits[i]);
+	}
+
+	if (!q->hh_flows)
+		return;
+
+	for (i = 0; i < HH_FLOWS_CNT; i++) {
+		struct hh_flow_state *flow, *next;
+		struct list_head *head = &q->hh_flows[i];
+
+		if (list_empty(head))
+			continue;
+		list_for_each_entry_safe(flow, next, head, flowchain) {
+			list_del(&flow->flowchain);
+			kfree(flow);
+		}
+	}
+	kvfree(q->hh_flows);
+}
+
+static const struct nla_policy hhf_policy[TCA_HHF_MAX + 1] = {
+	[TCA_HHF_BACKLOG_LIMIT]	 = { .type = NLA_U32 },
+	[TCA_HHF_QUANTUM]	 = { .type = NLA_U32 },
+	[TCA_HHF_HH_FLOWS_LIMIT] = { .type = NLA_U32 },
+	[TCA_HHF_RESET_TIMEOUT]	 = { .type = NLA_U32 },
+	[TCA_HHF_ADMIT_BYTES]	 = { .type = NLA_U32 },
+	[TCA_HHF_EVICT_TIMEOUT]	 = { .type = NLA_U32 },
+	[TCA_HHF_NON_HH_WEIGHT]	 = { .type = NLA_U32 },
+};
+
+static int hhf_change(struct Qdisc *sch, struct nlattr *opt,
+		      struct netlink_ext_ack *extack)
+{
+	struct hhf_sched_data *q = qdisc_priv(sch);
+	struct nlattr *tb[TCA_HHF_MAX + 1];
+	unsigned int qlen, prev_backlog;
+	int err;
+	u64 non_hh_quantum;
+	u32 new_quantum = q->quantum;
+	u32 new_hhf_non_hh_weight = q->hhf_non_hh_weight;
+
+	err = nla_parse_nested_deprecated(tb, TCA_HHF_MAX, opt, hhf_policy,
+					  NULL);
+	if (err < 0)
+		return err;
+
+	if (tb[TCA_HHF_QUANTUM])
+		new_quantum = nla_get_u32(tb[TCA_HHF_QUANTUM]);
+
+	if (tb[TCA_HHF_NON_HH_WEIGHT])
+		new_hhf_non_hh_weight = nla_get_u32(tb[TCA_HHF_NON_HH_WEIGHT]);
+
+	non_hh_quantum = (u64)new_quantum * new_hhf_non_hh_weight;
+	if (non_hh_quantum == 0 || non_hh_quantum > INT_MAX)
+		return -EINVAL;
+
+	sch_tree_lock(sch);
+
+	if (tb[TCA_HHF_BACKLOG_LIMIT])
+		sch->limit = nla_get_u32(tb[TCA_HHF_BACKLOG_LIMIT]);
+
+	q->quantum = new_quantum;
+	q->hhf_non_hh_weight = new_hhf_non_hh_weight;
+
+	if (tb[TCA_HHF_HH_FLOWS_LIMIT])
+		q->hh_flows_limit = nla_get_u32(tb[TCA_HHF_HH_FLOWS_LIMIT]);
+
+	if (tb[TCA_HHF_RESET_TIMEOUT]) {
+		u32 us = nla_get_u32(tb[TCA_HHF_RESET_TIMEOUT]);
+
+		q->hhf_reset_timeout = usecs_to_jiffies(us);
+	}
+
+	if (tb[TCA_HHF_ADMIT_BYTES])
+		q->hhf_admit_bytes = nla_get_u32(tb[TCA_HHF_ADMIT_BYTES]);
+
+	if (tb[TCA_HHF_EVICT_TIMEOUT]) {
+		u32 us = nla_get_u32(tb[TCA_HHF_EVICT_TIMEOUT]);
+
+		q->hhf_evict_timeout = usecs_to_jiffies(us);
+	}
+
+	qlen = sch->q.qlen;
+	prev_backlog = sch->qstats.backlog;
+	while (sch->q.qlen > sch->limit) {
+		struct sk_buff *skb = hhf_dequeue(sch);
+
+		rtnl_kfree_skbs(skb, skb);
+	}
+	qdisc_tree_reduce_backlog(sch, qlen - sch->q.qlen,
+				  prev_backlog - sch->qstats.backlog);
+
+	sch_tree_unlock(sch);
+	return 0;
+}
+
+static int hhf_init(struct Qdisc *sch, struct nlattr *opt,
+		    struct netlink_ext_ack *extack)
+{
+	struct hhf_sched_data *q = qdisc_priv(sch);
+	int i;
+
+	sch->limit = 1000;
+	q->quantum = psched_mtu(qdisc_dev(sch));
+	get_random_bytes(&q->perturbation, sizeof(q->perturbation));
+	INIT_LIST_HEAD(&q->new_buckets);
+	INIT_LIST_HEAD(&q->old_buckets);
+
+	/* Configurable HHF parameters */
+	q->hhf_reset_timeout = HZ / 25; /* 40  ms */
+	q->hhf_admit_bytes = 131072;    /* 128 KB */
+	q->hhf_evict_timeout = HZ;      /* 1  sec */
+	q->hhf_non_hh_weight = 2;
+
+	if (opt) {
+		int err = hhf_change(sch, opt, extack);
+
+		if (err)
+			return err;
+	}
+
+	if (!q->hh_flows) {
+		/* Initialize heavy-hitter flow table. */
+		q->hh_flows = kvcalloc(HH_FLOWS_CNT, sizeof(struct list_head),
+				       GFP_KERNEL);
+		if (!q->hh_flows)
+			return -ENOMEM;
+		for (i = 0; i < HH_FLOWS_CNT; i++)
+			INIT_LIST_HEAD(&q->hh_flows[i]);
+
+		/* Cap max active HHs at twice len of hh_flows table. */
+		q->hh_flows_limit = 2 * HH_FLOWS_CNT;
+		q->hh_flows_overlimit = 0;
+		q->hh_flows_total_cnt = 0;
+		q->hh_flows_current_cnt = 0;
+
+		/* Initialize heavy-hitter filter arrays. */
+		for (i = 0; i < HHF_ARRAYS_CNT; i++) {
+			q->hhf_arrays[i] = kvcalloc(HHF_ARRAYS_LEN,
+						    sizeof(u32),
+						    GFP_KERNEL);
+			if (!q->hhf_arrays[i]) {
+				/* Note: hhf_destroy() will be called
+				 * by our caller.
+				 */
+				return -ENOMEM;
+			}
+		}
+		q->hhf_arrays_reset_timestamp = hhf_time_stamp();
+
+		/* Initialize valid bits of heavy-hitter filter arrays. */
+		for (i = 0; i < HHF_ARRAYS_CNT; i++) {
+			q->hhf_valid_bits[i] = kvzalloc(HHF_ARRAYS_LEN /
+							  BITS_PER_BYTE, GFP_KERNEL);
+			if (!q->hhf_valid_bits[i]) {
+				/* Note: hhf_destroy() will be called
+				 * by our caller.
+				 */
+				return -ENOMEM;
+			}
+		}
+
+		/* Initialize Weighted DRR buckets. */
+		for (i = 0; i < WDRR_BUCKET_CNT; i++) {
+			struct wdrr_bucket *bucket = q->buckets + i;
+
+			INIT_LIST_HEAD(&bucket->bucketchain);
+		}
+	}
+
+	return 0;
+}
+
+static int hhf_dump(struct Qdisc *sch, struct sk_buff *skb)
+{
+	struct hhf_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_HHF_BACKLOG_LIMIT, sch->limit) ||
+	    nla_put_u32(skb, TCA_HHF_QUANTUM, q->quantum) ||
+	    nla_put_u32(skb, TCA_HHF_HH_FLOWS_LIMIT, q->hh_flows_limit) ||
+	    nla_put_u32(skb, TCA_HHF_RESET_TIMEOUT,
+			jiffies_to_usecs(q->hhf_reset_timeout)) ||
+	    nla_put_u32(skb, TCA_HHF_ADMIT_BYTES, q->hhf_admit_bytes) ||
+	    nla_put_u32(skb, TCA_HHF_EVICT_TIMEOUT,
+			jiffies_to_usecs(q->hhf_evict_timeout)) ||
+	    nla_put_u32(skb, TCA_HHF_NON_HH_WEIGHT, q->hhf_non_hh_weight))
+		goto nla_put_failure;
+
+	return nla_nest_end(skb, opts);
+
+nla_put_failure:
+	return -1;
+}
+
+static int hhf_dump_stats(struct Qdisc *sch, struct gnet_dump *d)
+{
+	struct hhf_sched_data *q = qdisc_priv(sch);
+	struct tc_hhf_xstats st = {
+		.drop_overlimit = q->drop_overlimit,
+		.hh_overlimit	= q->hh_flows_overlimit,
+		.hh_tot_count	= q->hh_flows_total_cnt,
+		.hh_cur_count	= q->hh_flows_current_cnt,
+	};
+
+	return gnet_stats_copy_app(d, &st, sizeof(st));
+}
+
+static struct Qdisc_ops hhf_qdisc_ops __read_mostly = {
+	.id		=	"hhf",
+	.priv_size	=	sizeof(struct hhf_sched_data),
+
+	.enqueue	=	hhf_enqueue,
+	.dequeue	=	hhf_dequeue,
+	.peek		=	qdisc_peek_dequeued,
+	.init		=	hhf_init,
+	.reset		=	hhf_reset,
+	.destroy	=	hhf_destroy,
+	.change		=	hhf_change,
+	.dump		=	hhf_dump,
+	.dump_stats	=	hhf_dump_stats,
+	.owner		=	THIS_MODULE,
+};
+
+static int __init hhf_module_init(void)
+{
+	return register_qdisc(&hhf_qdisc_ops);
+}
+
+static void __exit hhf_module_exit(void)
+{
+	unregister_qdisc(&hhf_qdisc_ops);
+}
+
+module_init(hhf_module_init)
+module_exit(hhf_module_exit)
+MODULE_AUTHOR("Terry Lam");
+MODULE_AUTHOR("Nandita Dukkipati");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Heavy-Hitter Filter (HHF)");