/* SPDX-License-Identifier: GPL-2.0-or-later */

#ifndef _LINUX_DROPREASON_QDISC_H
#define _LINUX_DROPREASON_QDISC_H
#include <net/dropreason.h>

#define DEFINE_QDISC_DROP_REASON(FN, FNe)       \
        FN(UNSPEC)                      \
        FN(GENERIC)                     \
        FN(OVERLIMIT)                   \
        FN(CONGESTED)                   \
        FN(MAXFLOWS)                    \
        FN(FLOOD_PROTECTION)            \
        FN(BAND_LIMIT)          \
        FN(HORIZON_LIMIT)               \
        FN(FLOW_LIMIT)                  \
        FN(L4S_STEP_NON_ECN)            \
        FNe(MAX)

#undef FN
#undef FNe
#define FN(reason)      QDISC_DROP_##reason,
#define FNe(reason)     QDISC_DROP_##reason

/**
 * enum qdisc_drop_reason - reason why a qdisc dropped a packet
 *
 * Qdisc-specific drop reasons for packet drops that occur within the
 * traffic control (TC) queueing discipline layer. These reasons provide
 * detailed diagnostics about why packets were dropped by various qdisc
 * algorithms, enabling fine-grained monitoring and troubleshooting of
 * queue behavior.
 */
enum qdisc_drop_reason {
        /**
         * @QDISC_DROP_UNSPEC: unspecified/invalid qdisc drop reason.
         * Value 0 serves as analogous to SKB_NOT_DROPPED_YET for enum skb_drop_reason.
         * Used for catching zero-initialized drop_reason fields.
         */
        QDISC_DROP_UNSPEC = 0,
        /**
         * @__QDISC_DROP_REASON: subsystem base value for qdisc drop reasons
         */
        __QDISC_DROP_REASON = SKB_DROP_REASON_SUBSYS_QDISC <<
                                SKB_DROP_REASON_SUBSYS_SHIFT,
        /**
         * @QDISC_DROP_GENERIC: generic/default qdisc drop, used when no
         * more specific reason applies
         */
        QDISC_DROP_GENERIC,
        /**
         * @QDISC_DROP_OVERLIMIT: packet dropped because the qdisc queue
         * length exceeded its configured limit (sch->limit). This typically
         * indicates the queue is full and cannot accept more packets.
         */
        QDISC_DROP_OVERLIMIT,
        /**
         * @QDISC_DROP_CONGESTED: packet dropped due to active congestion
         * control algorithms (e.g., CoDel, PIE, RED) detecting network
         * congestion. The qdisc proactively dropped the packet to signal
         * congestion to the sender and prevent bufferbloat.
         */
        QDISC_DROP_CONGESTED,
        /**
         * @QDISC_DROP_MAXFLOWS: packet dropped because the qdisc's flow
         * tracking table is full and no free slots are available to allocate
         * for a new flow. This indicates flow table exhaustion in flow-based
         * qdiscs that maintain per-flow state (e.g., SFQ).
         */
        QDISC_DROP_MAXFLOWS,
        /**
         * @QDISC_DROP_FLOOD_PROTECTION: packet dropped by flood protection
         * mechanism detecting unresponsive flows (potential DoS/flood).
         * Used by qdiscs implementing probabilistic drop algorithms like
         * BLUE (e.g., CAKE's Cobalt AQM).
         */
        QDISC_DROP_FLOOD_PROTECTION,
        /**
         * @QDISC_DROP_BAND_LIMIT: packet dropped because the priority band's
         * limit was reached. Used by qdiscs with priority bands that have
         * per-band packet limits (e.g., FQ).
         */
        QDISC_DROP_BAND_LIMIT,
        /**
         * @QDISC_DROP_HORIZON_LIMIT: packet dropped because its timestamp
         * is too far in the future (beyond the configured horizon).
         * Used by qdiscs with time-based scheduling (e.g., FQ).
         */
        QDISC_DROP_HORIZON_LIMIT,
        /**
         * @QDISC_DROP_FLOW_LIMIT: packet dropped because an individual flow
         * exceeded its per-flow packet/depth limit. Used by FQ and SFQ qdiscs
         * to enforce per-flow fairness and prevent a single flow from
         * monopolizing queue resources.
         */
        QDISC_DROP_FLOW_LIMIT,
        /**
         * @QDISC_DROP_L4S_STEP_NON_ECN: DualPI2 qdisc dropped a non-ECN-capable
         * packet because the L4S queue delay exceeded the step threshold.
         * Since the packet cannot be ECN-marked, it must be dropped to signal
         * congestion. See RFC 9332 for the DualQ Coupled AQM step mechanism.
         */
        QDISC_DROP_L4S_STEP_NON_ECN,
        /**
         * @QDISC_DROP_MAX: the maximum of qdisc drop reasons, which
         * shouldn't be used as a real 'reason' - only for tracing code gen
         */
        QDISC_DROP_MAX,
};

#undef FN
#undef FNe

#endif