ieee8021q_helpers.c

// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2024 Pengutronix, Oleksij Rempel <[email protected]>

#include <linux/array_size.h>
#include <linux/printk.h>
#include <linux/types.h>
#include <net/dscp.h>
#include <net/ieee8021q.h>

/* verify that table covers all 8 traffic types */
#define TT_MAP_SIZE_OK(tbl)                                 \
	compiletime_assert(ARRAY_SIZE(tbl) == IEEE8021Q_TT_MAX, \
			   #tbl " size mismatch")

/* The following arrays map Traffic Types (TT) to traffic classes (TC) for
 * different number of queues as shown in the example provided by
 * IEEE 802.1Q-2022 in Annex I "I.3 Traffic type to traffic class mapping" and
 * Table I-1 "Traffic type to traffic class mapping".
 */
static const u8 ieee8021q_8queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0,
	[IEEE8021Q_TT_BE] = 1,
	[IEEE8021Q_TT_EE] = 2,
	[IEEE8021Q_TT_CA] = 3,
	[IEEE8021Q_TT_VI] = 4,
	[IEEE8021Q_TT_VO] = 5,
	[IEEE8021Q_TT_IC] = 6,
	[IEEE8021Q_TT_NC] = 7,
};

static const u8 ieee8021q_7queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0,
	[IEEE8021Q_TT_BE] = 1,
	[IEEE8021Q_TT_EE] = 2,
	[IEEE8021Q_TT_CA] = 3,
	[IEEE8021Q_TT_VI] = 4,	[IEEE8021Q_TT_VO] = 4,
	[IEEE8021Q_TT_IC] = 5,
	[IEEE8021Q_TT_NC] = 6,
};

static const u8 ieee8021q_6queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0,
	[IEEE8021Q_TT_BE] = 1,
	[IEEE8021Q_TT_EE] = 2,	[IEEE8021Q_TT_CA] = 2,
	[IEEE8021Q_TT_VI] = 3,	[IEEE8021Q_TT_VO] = 3,
	[IEEE8021Q_TT_IC] = 4,
	[IEEE8021Q_TT_NC] = 5,
};

static const u8 ieee8021q_5queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
	[IEEE8021Q_TT_EE] = 1, [IEEE8021Q_TT_CA] = 1,
	[IEEE8021Q_TT_VI] = 2, [IEEE8021Q_TT_VO] = 2,
	[IEEE8021Q_TT_IC] = 3,
	[IEEE8021Q_TT_NC] = 4,
};

static const u8 ieee8021q_4queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
	[IEEE8021Q_TT_EE] = 1, [IEEE8021Q_TT_CA] = 1,
	[IEEE8021Q_TT_VI] = 2, [IEEE8021Q_TT_VO] = 2,
	[IEEE8021Q_TT_IC] = 3, [IEEE8021Q_TT_NC] = 3,
};

static const u8 ieee8021q_3queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
	[IEEE8021Q_TT_EE] = 0, [IEEE8021Q_TT_CA] = 0,
	[IEEE8021Q_TT_VI] = 1, [IEEE8021Q_TT_VO] = 1,
	[IEEE8021Q_TT_IC] = 2, [IEEE8021Q_TT_NC] = 2,
};

static const u8 ieee8021q_2queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
	[IEEE8021Q_TT_EE] = 0, [IEEE8021Q_TT_CA] = 0,
	[IEEE8021Q_TT_VI] = 1, [IEEE8021Q_TT_VO] = 1,
	[IEEE8021Q_TT_IC] = 1, [IEEE8021Q_TT_NC] = 1,
};

static const u8 ieee8021q_1queue_tt_tc_map[] = {
	[IEEE8021Q_TT_BK] = 0, [IEEE8021Q_TT_BE] = 0,
	[IEEE8021Q_TT_EE] = 0, [IEEE8021Q_TT_CA] = 0,
	[IEEE8021Q_TT_VI] = 0, [IEEE8021Q_TT_VO] = 0,
	[IEEE8021Q_TT_IC] = 0, [IEEE8021Q_TT_NC] = 0,
};

/**
 * ieee8021q_tt_to_tc - Map IEEE 802.1Q Traffic Type to Traffic Class
 * @tt: IEEE 802.1Q Traffic Type
 * @num_queues: Number of queues
 *
 * This function maps an IEEE 802.1Q Traffic Type to a Traffic Class (TC) based
 * on the number of queues configured on the NIC. The mapping is based on the
 * example provided by IEEE 802.1Q-2022 in Annex I "I.3 Traffic type to traffic
 * class mapping" and Table I-1 "Traffic type to traffic class mapping".
 *
 * Return: Traffic Class corresponding to the given Traffic Type or negative
 * value in case of error.
 */
int ieee8021q_tt_to_tc(enum ieee8021q_traffic_type tt, unsigned int num_queues)
{
	if (tt < 0 || tt >= IEEE8021Q_TT_MAX) {
		pr_err("Requested Traffic Type (%d) is out of range (%d)\n", tt,
		       IEEE8021Q_TT_MAX);
		return -EINVAL;
	}

	switch (num_queues) {
	case 8:
		TT_MAP_SIZE_OK(ieee8021q_8queue_tt_tc_map);
		return ieee8021q_8queue_tt_tc_map[tt];
	case 7:
		TT_MAP_SIZE_OK(ieee8021q_7queue_tt_tc_map);
		return ieee8021q_7queue_tt_tc_map[tt];
	case 6:
		TT_MAP_SIZE_OK(ieee8021q_6queue_tt_tc_map);
		return ieee8021q_6queue_tt_tc_map[tt];
	case 5:
		TT_MAP_SIZE_OK(ieee8021q_5queue_tt_tc_map);
		return ieee8021q_5queue_tt_tc_map[tt];
	case 4:
		TT_MAP_SIZE_OK(ieee8021q_4queue_tt_tc_map);
		return ieee8021q_4queue_tt_tc_map[tt];
	case 3:
		TT_MAP_SIZE_OK(ieee8021q_3queue_tt_tc_map);
		return ieee8021q_3queue_tt_tc_map[tt];
	case 2:
		TT_MAP_SIZE_OK(ieee8021q_2queue_tt_tc_map);
		return ieee8021q_2queue_tt_tc_map[tt];
	case 1:
		TT_MAP_SIZE_OK(ieee8021q_1queue_tt_tc_map);
		return ieee8021q_1queue_tt_tc_map[tt];
	}

	pr_err("Invalid number of queues %d\n", num_queues);

	return -EINVAL;
}
EXPORT_SYMBOL_GPL(ieee8021q_tt_to_tc);

/**
 * ietf_dscp_to_ieee8021q_tt - Map IETF DSCP to IEEE 802.1Q Traffic Type
 * @dscp: IETF DSCP value
 *
 * This function maps an IETF DSCP value to an IEEE 802.1Q Traffic Type (TT).
 * Since there is no corresponding mapping between DSCP and IEEE 802.1Q Traffic
 * Type, this function is inspired by the RFC8325 documentation which describe
 * the mapping between DSCP and 802.11 User Priority (UP) values.
 *
 * Return: IEEE 802.1Q Traffic Type corresponding to the given DSCP value
 */
int ietf_dscp_to_ieee8021q_tt(u8 dscp)
{
	switch (dscp) {
	case DSCP_CS0:
	/* Comment from RFC8325:
	 * [RFC4594], Section 4.8, recommends High-Throughput Data be marked
	 * AF1x (that is, AF11, AF12, and AF13, according to the rules defined
	 * in [RFC2475]).
	 *
	 * By default (as described in Section 2.3), High-Throughput Data will
	 * map to UP 1 and, thus, to the Background Access Category (AC_BK),
	 * which is contrary to the intent expressed in [RFC4594].

	 * Unfortunately, there really is no corresponding fit for the High-
	 * Throughput Data service class within the constrained 4 Access
	 * Category [IEEE.802.11-2016] model.  If the High-Throughput Data
	 * service class is assigned to the Best Effort Access Category (AC_BE),
	 * then it would contend with Low-Latency Data (while [RFC4594]
	 * recommends a distinction in servicing between these service classes)
	 * as well as with the default service class; alternatively, if it is
	 * assigned to the Background Access Category (AC_BK), then it would
	 * receive a less-then-best-effort service and contend with Low-Priority
	 * Data (as discussed in Section 4.2.10).
	 *
	 * As such, since there is no directly corresponding fit for the High-
	 * Throughout Data service class within the [IEEE.802.11-2016] model, it
	 * is generally RECOMMENDED to map High-Throughput Data to UP 0, thereby
	 * admitting it to the Best Effort Access Category (AC_BE).
	 *
	 * Note: The above text is from RFC8325 which is describing the mapping
	 * between DSCP and 802.11 User Priority (UP) values. The mapping
	 * between UP and IEEE 802.1Q Traffic Type is not defined in the RFC but
	 * the 802.11 AC_BK and AC_BE are closely related to the IEEE 802.1Q
	 * Traffic Types BE and BK.
	 */
	case DSCP_AF11:
	case DSCP_AF12:
	case DSCP_AF13:
		return IEEE8021Q_TT_BE;
	/* Comment from RFC8325:
	 * RFC3662 and RFC4594 both recommend Low-Priority Data be marked
	 * with DSCP CS1. The Low-Priority Data service class loosely
	 * corresponds to the [IEEE.802.11-2016] Background Access Category
	 */
	case DSCP_CS1:
		return IEEE8021Q_TT_BK;
	case DSCP_CS2:
	case DSCP_AF21:
	case DSCP_AF22:
	case DSCP_AF23:
		return IEEE8021Q_TT_EE;
	case DSCP_CS3:
	case DSCP_AF31:
	case DSCP_AF32:
	case DSCP_AF33:
		return IEEE8021Q_TT_CA;
	case DSCP_CS4:
	case DSCP_AF41:
	case DSCP_AF42:
	case DSCP_AF43:
		return IEEE8021Q_TT_VI;
	case DSCP_CS5:
	case DSCP_EF:
	case DSCP_VOICE_ADMIT:
		return IEEE8021Q_TT_VO;
	case DSCP_CS6:
		return IEEE8021Q_TT_IC;
	case DSCP_CS7:
		return IEEE8021Q_TT_NC;
	}

	return SIMPLE_IETF_DSCP_TO_IEEE8021Q_TT(dscp);
}
EXPORT_SYMBOL_GPL(ietf_dscp_to_ieee8021q_tt);