mdoc.7/MANUAL STRUCTURE: add HARDWARE

[freebsd/src.git] / sys / netinet / tcp_ratelimit.c

/*-
 *
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 2018-2020
 *      Netflix Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */
/**
 * Author: Randall Stewart <rrs@netflix.com>
 */

#include <sys/cdefs.h>
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include "opt_ratelimit.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/eventhandler.h>
#include <sys/mutex.h>
#include <sys/ck.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/if_private.h>
#include <netinet/in.h>
#include <netinet/in_pcb.h>
#define TCPSTATES               /* for logging */
#include <netinet/tcp_var.h>
#include <netinet/tcp_hpts.h>
#include <netinet/tcp_log_buf.h>
#include <netinet/tcp_ratelimit.h>
#ifndef USECS_IN_SECOND
#define USECS_IN_SECOND 1000000
#endif
/*
 * For the purposes of each send, what is the size
 * of an ethernet frame.
 */
MALLOC_DEFINE(M_TCPPACE, "tcp_hwpace", "TCP Hardware pacing memory");
#ifdef RATELIMIT

/*
 * The following preferred table will seem weird to
 * the casual viewer. Why do we not have any rates below
 * 1Mbps? Why do we have a rate at 1.44Mbps called common?
 * Why do the rates cluster in the 1-100Mbps range more
 * than others? Why does the table jump around at the beginnign
 * and then be more consistently raising?
 *
 * Let me try to answer those questions. A lot of
 * this is dependant on the hardware. We have three basic
 * supporters of rate limiting
 *
 * Chelsio - Supporting 16 configurable rates.
 * Mlx  - c4 supporting 13 fixed rates.
 * Mlx  - c5 & c6 supporting 127 configurable rates.
 *
 * The c4 is why we have a common rate that is available
 * in all rate tables. This is a selected rate from the
 * c4 table and we assure its available in all ratelimit
 * tables. This way the tcp_ratelimit code has an assured
 * rate it should always be able to get. This answers a
 * couple of the questions above.
 *
 * So what about the rest, well the table is built to
 * try to get the most out of a joint hardware/software
 * pacing system.  The software pacer will always pick
 * a rate higher than the b/w that it is estimating
 *
 * on the path. This is done for two reasons.
 * a) So we can discover more b/w
 * and
 * b) So we can send a block of MSS's down and then
 *    have the software timer go off after the previous
 *    send is completely out of the hardware.
 *
 * But when we do <b> we don't want to have the delay
 * between the last packet sent by the hardware be
 * excessively long (to reach our desired rate).
 *
 * So let me give an example for clarity.
 *
 * Lets assume that the tcp stack sees that 29,110,000 bps is
 * what the bw of the path is. The stack would select the
 * rate 31Mbps. 31Mbps means that each send that is done
 * by the hardware will cause a 390 micro-second gap between
 * the packets sent at that rate. For 29,110,000 bps we
 * would need 416 micro-seconds gap between each send.
 *
 * Note that are calculating a complete time for pacing
 * which includes the ethernet, IP and TCP overhead. So
 * a full 1514 bytes is used for the above calculations.
 * My testing has shown that both cards are also using this
 * as their basis i.e. full payload size of the ethernet frame.
 * The TCP stack caller needs to be aware of this and make the
 * appropriate overhead calculations be included in its choices.
 *
 * Now, continuing our example, we pick a MSS size based on the
 * delta between the two rates (416 - 390) divided into the rate
 * we really wish to send at rounded up.  That results in a MSS
 * send of 17 mss's at once. The hardware then will
 * run out of data in a single 17MSS send in 6,630 micro-seconds.
 *
 * On the other hand the software pacer will send more data
 * in 7,072 micro-seconds. This means that we will refill
 * the hardware 52 microseconds after it would have sent
 * next if it had not ran out of data. This is a win since we are
 * only sending every 7ms or so and yet all the packets are spaced on
 * the wire with 94% of what they should be and only
 * the last packet is delayed extra to make up for the
 * difference.
 *
 * Note that the above formula has two important caveat.
 * If we are above (b/w wise) over 100Mbps we double the result
 * of the MSS calculation. The second caveat is if we are 500Mbps
 * or more we just send the maximum MSS at once i.e. 45MSS. At
 * the higher b/w's even the cards have limits to what times (timer granularity)
 * they can insert between packets and start to send more than one
 * packet at a time on the wire.
 *
 */
#define COMMON_RATE 180500
const uint64_t desired_rates[] = {
        122500,                 /* 1Mbps  - rate 1 */
        180500,                 /* 1.44Mpbs - rate 2  common rate */
        375000,                 /* 3Mbps    - rate 3 */
        625000,                 /* 5Mbps    - rate 4 */
        1250000,                /* 10Mbps   - rate 5 */
        1875000,                /* 15Mbps   - rate 6 */
        2500000,                /* 20Mbps   - rate 7 */
        3125000,                /* 25Mbps   - rate 8 */
        3750000,                /* 30Mbps   - rate 9 */
        4375000,                /* 35Mbps   - rate 10 */
        5000000,                /* 40Meg    - rate 11 */
        6250000,                /* 50Mbps   - rate 12 */
        12500000,               /* 100Mbps  - rate 13 */
        25000000,               /* 200Mbps  - rate 14 */
        50000000,               /* 400Mbps  - rate 15 */
        100000000,              /* 800Mbps  - rate 16 */
        5625000,                /* 45Mbps   - rate 17 */
        6875000,                /* 55Mbps   - rate 19 */
        7500000,                /* 60Mbps   - rate 20 */
        8125000,                /* 65Mbps   - rate 21 */
        8750000,                /* 70Mbps   - rate 22 */
        9375000,                /* 75Mbps   - rate 23 */
        10000000,               /* 80Mbps   - rate 24 */
        10625000,               /* 85Mbps   - rate 25 */
        11250000,               /* 90Mbps   - rate 26 */
        11875000,               /* 95Mbps   - rate 27 */
        12500000,               /* 100Mbps  - rate 28 */
        13750000,               /* 110Mbps  - rate 29 */
        15000000,               /* 120Mbps  - rate 30 */
        16250000,               /* 130Mbps  - rate 31 */
        17500000,               /* 140Mbps  - rate 32 */
        18750000,               /* 150Mbps  - rate 33 */
        20000000,               /* 160Mbps  - rate 34 */
        21250000,               /* 170Mbps  - rate 35 */
        22500000,               /* 180Mbps  - rate 36 */
        23750000,               /* 190Mbps  - rate 37 */
        26250000,               /* 210Mbps  - rate 38 */
        27500000,               /* 220Mbps  - rate 39 */
        28750000,               /* 230Mbps  - rate 40 */
        30000000,               /* 240Mbps  - rate 41 */
        31250000,               /* 250Mbps  - rate 42 */
        34375000,               /* 275Mbps  - rate 43 */
        37500000,               /* 300Mbps  - rate 44 */
        40625000,               /* 325Mbps  - rate 45 */
        43750000,               /* 350Mbps  - rate 46 */
        46875000,               /* 375Mbps  - rate 47 */
        53125000,               /* 425Mbps  - rate 48 */
        56250000,               /* 450Mbps  - rate 49 */
        59375000,               /* 475Mbps  - rate 50 */
        62500000,               /* 500Mbps  - rate 51 */
        68750000,               /* 550Mbps  - rate 52 */
        75000000,               /* 600Mbps  - rate 53 */
        81250000,               /* 650Mbps  - rate 54 */
        87500000,               /* 700Mbps  - rate 55 */
        93750000,               /* 750Mbps  - rate 56 */
        106250000,              /* 850Mbps  - rate 57 */
        112500000,              /* 900Mbps  - rate 58 */
        125000000,              /* 1Gbps    - rate 59 */
        156250000,              /* 1.25Gps  - rate 60 */
        187500000,              /* 1.5Gps   - rate 61 */
        218750000,              /* 1.75Gps  - rate 62 */
        250000000,              /* 2Gbps    - rate 63 */
        281250000,              /* 2.25Gps  - rate 64 */
        312500000,              /* 2.5Gbps  - rate 65 */
        343750000,              /* 2.75Gbps - rate 66 */
        375000000,              /* 3Gbps    - rate 67 */
        500000000,              /* 4Gbps    - rate 68 */
        625000000,              /* 5Gbps    - rate 69 */
        750000000,              /* 6Gbps    - rate 70 */
        875000000,              /* 7Gbps    - rate 71 */
        1000000000,             /* 8Gbps    - rate 72 */
        1125000000,             /* 9Gbps    - rate 73 */
        1250000000,             /* 10Gbps   - rate 74 */
        1875000000,             /* 15Gbps   - rate 75 */
        2500000000              /* 20Gbps   - rate 76 */
};

#define MAX_HDWR_RATES (sizeof(desired_rates)/sizeof(uint64_t))
#define RS_ORDERED_COUNT 16     /*
                                 * Number that are in order
                                 * at the beginning of the table,
                                 * over this a sort is required.
                                 */
#define RS_NEXT_ORDER_GROUP 16  /*
                                 * The point in our table where
                                 * we come fill in a second ordered
                                 * group (index wise means -1).
                                 */
#define ALL_HARDWARE_RATES 1004 /*
                                 * 1Meg - 1Gig in 1 Meg steps
                                 * plus 100, 200k  and 500k and
                                 * 10Gig
                                 */

#define RS_ONE_MEGABIT_PERSEC 1000000
#define RS_ONE_GIGABIT_PERSEC 1000000000
#define RS_TEN_GIGABIT_PERSEC 10000000000

static struct head_tcp_rate_set int_rs;
static struct mtx rs_mtx;
uint32_t rs_number_alive;
uint32_t rs_number_dead;
static uint32_t rs_floor_mss = 0;
static uint32_t wait_time_floor = 8000; /* 8 ms */
static uint32_t rs_hw_floor_mss = 16;
static uint32_t num_of_waits_allowed = 1; /* How many time blocks are we willing to wait */

static uint32_t mss_divisor = RL_DEFAULT_DIVISOR;
static uint32_t even_num_segs = 1;
static uint32_t even_threshold = 4;

SYSCTL_NODE(_net_inet_tcp, OID_AUTO, rl, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "TCP Ratelimit stats");
SYSCTL_UINT(_net_inet_tcp_rl, OID_AUTO, alive, CTLFLAG_RW,
    &rs_number_alive, 0,
    "Number of interfaces initialized for ratelimiting");
SYSCTL_UINT(_net_inet_tcp_rl, OID_AUTO, dead, CTLFLAG_RW,
    &rs_number_dead, 0,
    "Number of interfaces departing from ratelimiting");
SYSCTL_UINT(_net_inet_tcp_rl, OID_AUTO, floor_mss, CTLFLAG_RW,
    &rs_floor_mss, 0,
    "Number of MSS that will override the normal minimums (0 means don't enforce)");
SYSCTL_UINT(_net_inet_tcp_rl, OID_AUTO, wait_floor, CTLFLAG_RW,
    &wait_time_floor, 2000,
    "Has b/w increases what is the wait floor we are willing to wait at the end?");
SYSCTL_UINT(_net_inet_tcp_rl, OID_AUTO, time_blocks, CTLFLAG_RW,
    &num_of_waits_allowed, 1,
    "How many time blocks on the end should software pacing be willing to wait?");

SYSCTL_UINT(_net_inet_tcp_rl, OID_AUTO, hw_floor_mss, CTLFLAG_RW,
    &rs_hw_floor_mss, 16,
    "Number of mss that are a minum for hardware pacing?");

SYSCTL_INT(_net_inet_tcp_rl, OID_AUTO, divisor, CTLFLAG_RW,
    &mss_divisor, RL_DEFAULT_DIVISOR,
    "The value divided into bytes per second to help establish mss size");
SYSCTL_INT(_net_inet_tcp_rl, OID_AUTO, even, CTLFLAG_RW,
    &even_num_segs, 1,
    "Do we round mss size up to an even number of segments for delayed ack");
SYSCTL_INT(_net_inet_tcp_rl, OID_AUTO, eventhresh, CTLFLAG_RW,
    &even_threshold, 4,
    "At what number of mss do we start rounding up to an even number of mss?");

static void
rl_add_syctl_entries(struct sysctl_oid *rl_sysctl_root, struct tcp_rate_set *rs)
{
        /*
         * Add sysctl entries for thus interface.
         */
        if (rs->rs_flags & RS_INTF_NO_SUP) {
                SYSCTL_ADD_S32(&rs->sysctl_ctx,
                   SYSCTL_CHILDREN(rl_sysctl_root),
                   OID_AUTO, "disable", CTLFLAG_RD,
                   &rs->rs_disable, 0,
                   "Disable this interface from new hdwr limiting?");
        } else {
                SYSCTL_ADD_S32(&rs->sysctl_ctx,
                   SYSCTL_CHILDREN(rl_sysctl_root),
                   OID_AUTO, "disable", CTLFLAG_RW,
                   &rs->rs_disable, 0,
                   "Disable this interface from new hdwr limiting?");
        }
        SYSCTL_ADD_S32(&rs->sysctl_ctx,
            SYSCTL_CHILDREN(rl_sysctl_root),
            OID_AUTO, "minseg", CTLFLAG_RW,
            &rs->rs_min_seg, 0,
            "What is the minimum we need to send on this interface?");
        SYSCTL_ADD_U64(&rs->sysctl_ctx,
            SYSCTL_CHILDREN(rl_sysctl_root),
            OID_AUTO, "flow_limit", CTLFLAG_RW,
            &rs->rs_flow_limit, 0,
            "What is the limit for number of flows (0=unlimited)?");
        SYSCTL_ADD_S32(&rs->sysctl_ctx,
            SYSCTL_CHILDREN(rl_sysctl_root),
            OID_AUTO, "highest", CTLFLAG_RD,
            &rs->rs_highest_valid, 0,
            "Highest valid rate");
        SYSCTL_ADD_S32(&rs->sysctl_ctx,
            SYSCTL_CHILDREN(rl_sysctl_root),
            OID_AUTO, "lowest", CTLFLAG_RD,
            &rs->rs_lowest_valid, 0,
            "Lowest valid rate");
        SYSCTL_ADD_S32(&rs->sysctl_ctx,
            SYSCTL_CHILDREN(rl_sysctl_root),
            OID_AUTO, "flags", CTLFLAG_RD,
            &rs->rs_flags, 0,
            "What lags are on the entry?");
        SYSCTL_ADD_S32(&rs->sysctl_ctx,
            SYSCTL_CHILDREN(rl_sysctl_root),
            OID_AUTO, "numrates", CTLFLAG_RD,
            &rs->rs_rate_cnt, 0,
            "How many rates re there?");
        SYSCTL_ADD_U64(&rs->sysctl_ctx,
            SYSCTL_CHILDREN(rl_sysctl_root),
            OID_AUTO, "flows_using", CTLFLAG_RD,
            &rs->rs_flows_using, 0,
            "How many flows are using this interface now?");
#ifdef DETAILED_RATELIMIT_SYSCTL
        if (rs->rs_rlt && rs->rs_rate_cnt > 0) {
                /*  Lets display the rates */
                int i;
                struct sysctl_oid *rl_rates;
                struct sysctl_oid *rl_rate_num;
                char rate_num[16];
                rl_rates = SYSCTL_ADD_NODE(&rs->sysctl_ctx,
                                            SYSCTL_CHILDREN(rl_sysctl_root),
                                            OID_AUTO,
                                            "rate",
                                            CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
                                            "Ratelist");
                for( i = 0; i < rs->rs_rate_cnt; i++) {
                        sprintf(rate_num, "%d", i);
                        rl_rate_num = SYSCTL_ADD_NODE(&rs->sysctl_ctx,
                                            SYSCTL_CHILDREN(rl_rates),
                                            OID_AUTO,
                                            rate_num,
                                            CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
                                            "Individual Rate");
                        SYSCTL_ADD_U32(&rs->sysctl_ctx,
                                       SYSCTL_CHILDREN(rl_rate_num),
                                       OID_AUTO, "flags", CTLFLAG_RD,
                                       &rs->rs_rlt[i].flags, 0,
                                       "Flags on this rate");
                        SYSCTL_ADD_U32(&rs->sysctl_ctx,
                                       SYSCTL_CHILDREN(rl_rate_num),
                                       OID_AUTO, "pacetime", CTLFLAG_RD,
                                       &rs->rs_rlt[i].time_between, 0,
                                       "Time hardware inserts between 1500 byte sends");
                        SYSCTL_ADD_LONG(&rs->sysctl_ctx,
                                       SYSCTL_CHILDREN(rl_rate_num),
                                       OID_AUTO, "rate", CTLFLAG_RD,
                                       &rs->rs_rlt[i].rate,
                                       "Rate in bytes per second");
                        SYSCTL_ADD_LONG(&rs->sysctl_ctx,
                                       SYSCTL_CHILDREN(rl_rate_num),
                                       OID_AUTO, "using", CTLFLAG_RD,
                                       &rs->rs_rlt[i].using,
                                       "Number of flows using");
                        SYSCTL_ADD_LONG(&rs->sysctl_ctx,
                                       SYSCTL_CHILDREN(rl_rate_num),
                                       OID_AUTO, "enobufs", CTLFLAG_RD,
                                       &rs->rs_rlt[i].rs_num_enobufs,
                                       "Number of enobufs logged on this rate");

                }
        }
#endif
}

static void
rs_destroy(epoch_context_t ctx)
{
        struct tcp_rate_set *rs;
        bool do_free_rs;

        rs = __containerof(ctx, struct tcp_rate_set, rs_epoch_ctx);

        mtx_lock(&rs_mtx);
        rs->rs_flags &= ~RS_FUNERAL_SCHD;
        /*
         * In theory its possible (but unlikely)
         * that while the delete was occuring
         * and we were applying the DEAD flag
         * someone slipped in and found the
         * interface in a lookup. While we
         * decided rs_flows_using were 0 and
         * scheduling the epoch_call, the other
         * thread incremented rs_flow_using. This
         * is because users have a pointer and
         * we only use the rs_flows_using in an
         * atomic fashion, i.e. the other entities
         * are not protected. To assure this did
         * not occur, we check rs_flows_using here
         * before deleting.
         */
        do_free_rs = (rs->rs_flows_using == 0);
        rs_number_dead--;
        mtx_unlock(&rs_mtx);

        if (do_free_rs) {
                sysctl_ctx_free(&rs->sysctl_ctx);
                free(rs->rs_rlt, M_TCPPACE);
                free(rs, M_TCPPACE);
        }
}

static void
rs_defer_destroy(struct tcp_rate_set *rs)
{

        mtx_assert(&rs_mtx, MA_OWNED);

        /* Check if already pending. */
        if (rs->rs_flags & RS_FUNERAL_SCHD)
                return;

        rs_number_dead++;

        /* Set flag to only defer once. */
        rs->rs_flags |= RS_FUNERAL_SCHD;
        NET_EPOCH_CALL(rs_destroy, &rs->rs_epoch_ctx);
}

#ifdef INET
extern counter_u64_t rate_limit_new;
extern counter_u64_t rate_limit_chg;
extern counter_u64_t rate_limit_set_ok;
extern counter_u64_t rate_limit_active;
extern counter_u64_t rate_limit_alloc_fail;
#endif

static int
rl_attach_txrtlmt(struct ifnet *ifp,
    uint32_t flowtype,
    int flowid,
    uint64_t cfg_rate,
    struct m_snd_tag **tag)
{
        int error;
        union if_snd_tag_alloc_params params = {
                .rate_limit.hdr.type = IF_SND_TAG_TYPE_RATE_LIMIT,
                .rate_limit.hdr.flowid = flowid,
                .rate_limit.hdr.flowtype = flowtype,
                .rate_limit.max_rate = cfg_rate,
                .rate_limit.flags = M_NOWAIT,
        };

        error = m_snd_tag_alloc(ifp, &params, tag);
#ifdef INET
        if (error == 0) {
                counter_u64_add(rate_limit_set_ok, 1);
                counter_u64_add(rate_limit_active, 1);
        } else if (error != EOPNOTSUPP)
                counter_u64_add(rate_limit_alloc_fail, 1);
#endif
        return (error);
}

static void
populate_canned_table(struct tcp_rate_set *rs, const uint64_t *rate_table_act)
{
        /*
         * The internal table is "special", it
         * is two seperate ordered tables that
         * must be merged. We get here when the
         * adapter specifies a number of rates that
         * covers both ranges in the table in some
         * form.
         */
        int i, at_low, at_high;
        uint8_t low_disabled = 0, high_disabled = 0;

        for(i = 0, at_low = 0, at_high = RS_NEXT_ORDER_GROUP; i < rs->rs_rate_cnt; i++) {
                rs->rs_rlt[i].flags = 0;
                rs->rs_rlt[i].time_between = 0;
                if ((low_disabled == 0) &&
                    (high_disabled ||
                     (rate_table_act[at_low] < rate_table_act[at_high]))) {
                        rs->rs_rlt[i].rate = rate_table_act[at_low];
                        at_low++;
                        if (at_low == RS_NEXT_ORDER_GROUP)
                                low_disabled = 1;
                } else if (high_disabled == 0) {
                        rs->rs_rlt[i].rate = rate_table_act[at_high];
                        at_high++;
                        if (at_high == MAX_HDWR_RATES)
                                high_disabled = 1;
                }
        }
}

static struct tcp_rate_set *
rt_setup_new_rs(struct ifnet *ifp, int *error)
{
        struct tcp_rate_set *rs;
        const uint64_t *rate_table_act;
        uint64_t lentim, res;
        size_t sz;
        uint32_t hash_type;
        int i;
        struct if_ratelimit_query_results rl;
        struct sysctl_oid *rl_sysctl_root;
        struct epoch_tracker et;
        /*
         * We expect to enter with the
         * mutex locked.
         */

        if (ifp->if_ratelimit_query == NULL) {
                /*
                 * We can do nothing if we cannot
                 * get a query back from the driver.
                 */
                printf("Warning:No query functions for %s:%d-- failed\n",
                       ifp->if_dname, ifp->if_dunit);
                return (NULL);
        }
        rs = malloc(sizeof(struct tcp_rate_set), M_TCPPACE, M_NOWAIT | M_ZERO);
        if (rs == NULL) {
                if (error)
                        *error = ENOMEM;
                printf("Warning:No memory for malloc of tcp_rate_set\n");
                return (NULL);
        }
        memset(&rl, 0, sizeof(rl));
        rl.flags = RT_NOSUPPORT;
        ifp->if_ratelimit_query(ifp, &rl);
        if (rl.flags & RT_IS_UNUSABLE) {
                /*
                 * The interface does not really support
                 * the rate-limiting.
                 */
                memset(rs, 0, sizeof(struct tcp_rate_set));
                rs->rs_ifp = ifp;
                rs->rs_if_dunit = ifp->if_dunit;
                rs->rs_flags = RS_INTF_NO_SUP;
                rs->rs_disable = 1;
                rs_number_alive++;
                sysctl_ctx_init(&rs->sysctl_ctx);
                rl_sysctl_root = SYSCTL_ADD_NODE(&rs->sysctl_ctx,
                    SYSCTL_STATIC_CHILDREN(_net_inet_tcp_rl),
                    OID_AUTO,
                    rs->rs_ifp->if_xname,
                    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
                    "");
                rl_add_syctl_entries(rl_sysctl_root, rs);
                NET_EPOCH_ENTER(et);
                mtx_lock(&rs_mtx);
                CK_LIST_INSERT_HEAD(&int_rs, rs, next);
                mtx_unlock(&rs_mtx);
                NET_EPOCH_EXIT(et);
                return (rs);
        } else if ((rl.flags & RT_IS_INDIRECT) == RT_IS_INDIRECT) {
                memset(rs, 0, sizeof(struct tcp_rate_set));
                rs->rs_ifp = ifp;
                rs->rs_if_dunit = ifp->if_dunit;
                rs->rs_flags = RS_IS_DEFF;
                rs_number_alive++;
                sysctl_ctx_init(&rs->sysctl_ctx);
                rl_sysctl_root = SYSCTL_ADD_NODE(&rs->sysctl_ctx,
                    SYSCTL_STATIC_CHILDREN(_net_inet_tcp_rl),
                    OID_AUTO,
                    rs->rs_ifp->if_xname,
                    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
                    "");
                rl_add_syctl_entries(rl_sysctl_root, rs);
                NET_EPOCH_ENTER(et);
                mtx_lock(&rs_mtx);
                CK_LIST_INSERT_HEAD(&int_rs, rs, next);
                mtx_unlock(&rs_mtx);
                NET_EPOCH_EXIT(et);
                return (rs);
        } else if ((rl.flags & RT_IS_FIXED_TABLE) == RT_IS_FIXED_TABLE) {
                /* Mellanox C4 likely */
                rs->rs_ifp = ifp;
                rs->rs_if_dunit = ifp->if_dunit;
                rs->rs_rate_cnt = rl.number_of_rates;
                rs->rs_min_seg = rl.min_segment_burst;
                rs->rs_highest_valid = 0;
                rs->rs_flow_limit = rl.max_flows;
                rs->rs_flags = RS_IS_INTF | RS_NO_PRE;
                rs->rs_disable = 0;
                rate_table_act = rl.rate_table;
        } else if ((rl.flags & RT_IS_SELECTABLE) == RT_IS_SELECTABLE) {
                /* Chelsio, C5 and C6 of Mellanox? */
                rs->rs_ifp = ifp;
                rs->rs_if_dunit = ifp->if_dunit;
                rs->rs_rate_cnt = rl.number_of_rates;
                rs->rs_min_seg = rl.min_segment_burst;
                rs->rs_disable = 0;
                rs->rs_flow_limit = rl.max_flows;
                rate_table_act = desired_rates;
                if ((rs->rs_rate_cnt > MAX_HDWR_RATES) &&
                    (rs->rs_rate_cnt < ALL_HARDWARE_RATES)) {
                        /*
                         * Our desired table is not big
                         * enough, do what we can.
                         */
                        rs->rs_rate_cnt = MAX_HDWR_RATES;
                 }
                if (rs->rs_rate_cnt <= RS_ORDERED_COUNT)
                        rs->rs_flags = RS_IS_INTF;
                else
                        rs->rs_flags = RS_IS_INTF | RS_INT_TBL;
                if (rs->rs_rate_cnt >= ALL_HARDWARE_RATES)
                        rs->rs_rate_cnt = ALL_HARDWARE_RATES;
        } else {
                free(rs, M_TCPPACE);
                return (NULL);
        }
        sz = sizeof(struct tcp_hwrate_limit_table) * rs->rs_rate_cnt;
        rs->rs_rlt = malloc(sz, M_TCPPACE, M_NOWAIT);
        if (rs->rs_rlt == NULL) {
                if (error)
                        *error = ENOMEM;
bail:
                free(rs, M_TCPPACE);
                return (NULL);
        }
        if (rs->rs_rate_cnt >= ALL_HARDWARE_RATES) {
                /*
                 * The interface supports all
                 * the rates we could possibly want.
                 */
                uint64_t rat;

                rs->rs_rlt[0].rate = 12500;     /* 100k */
                rs->rs_rlt[1].rate = 25000;     /* 200k */
                rs->rs_rlt[2].rate = 62500;     /* 500k */
                /* Note 125000 == 1Megabit
                 * populate 1Meg - 1000meg.
                 */
                for(i = 3, rat = 125000; i< (ALL_HARDWARE_RATES-1); i++) {
                        rs->rs_rlt[i].rate = rat;
                        rat += 125000;
                }
                rs->rs_rlt[(ALL_HARDWARE_RATES-1)].rate = 1250000000;
        } else if (rs->rs_flags & RS_INT_TBL) {
                /* We populate this in a special way */
                populate_canned_table(rs, rate_table_act);
        } else {
                /*
                 * Just copy in the rates from
                 * the table, it is in order.
                 */
                for (i=0; i<rs->rs_rate_cnt; i++) {
                        rs->rs_rlt[i].rate = rate_table_act[i];
                        rs->rs_rlt[i].time_between = 0;
                        rs->rs_rlt[i].flags = 0;
                }
        }
        for (i = (rs->rs_rate_cnt - 1); i >= 0; i--) {
                /*
                 * We go backwards through the list so that if we can't get
                 * a rate and fail to init one, we have at least a chance of
                 * getting the highest one.
                 */
                rs->rs_rlt[i].ptbl = rs;
                rs->rs_rlt[i].tag = NULL;
                rs->rs_rlt[i].using = 0;
                rs->rs_rlt[i].rs_num_enobufs = 0;
                /*
                 * Calculate the time between.
                 */
                lentim = ETHERNET_SEGMENT_SIZE * USECS_IN_SECOND;
                res = lentim / rs->rs_rlt[i].rate;
                if (res > 0)
                        rs->rs_rlt[i].time_between = res;
                else
                        rs->rs_rlt[i].time_between = 1;
                if (rs->rs_flags & RS_NO_PRE) {
                        rs->rs_rlt[i].flags = HDWRPACE_INITED;
                        rs->rs_lowest_valid = i;
                } else {
                        int err;

                        if ((rl.flags & RT_IS_SETUP_REQ)  &&
                            (ifp->if_ratelimit_query)) {
                                err = ifp->if_ratelimit_setup(ifp,
                                         rs->rs_rlt[i].rate, i);
                                if (err)
                                        goto handle_err;
                        }
#ifdef RSS
                        hash_type = M_HASHTYPE_RSS_TCP_IPV4;
#else
                        hash_type = M_HASHTYPE_OPAQUE_HASH;
#endif
                        err = rl_attach_txrtlmt(ifp,
                            hash_type,
                            (i + 1),
                            rs->rs_rlt[i].rate,
                            &rs->rs_rlt[i].tag);
                        if (err) {
handle_err:
                                if (i == (rs->rs_rate_cnt - 1)) {
                                        /*
                                         * Huh - first rate and we can't get
                                         * it?
                                         */
                                        free(rs->rs_rlt, M_TCPPACE);
                                        if (error)
                                                *error = err;
                                        goto bail;
                                } else {
                                        if (error)
                                                *error = err;
                                }
                                break;
                        } else {
                                rs->rs_rlt[i].flags = HDWRPACE_INITED | HDWRPACE_TAGPRESENT;
                                rs->rs_lowest_valid = i;
                        }
                }
        }
        /* Did we get at least 1 rate? */
        if (rs->rs_rlt[(rs->rs_rate_cnt - 1)].flags & HDWRPACE_INITED)
                rs->rs_highest_valid = rs->rs_rate_cnt - 1;
        else {
                free(rs->rs_rlt, M_TCPPACE);
                goto bail;
        }
        rs_number_alive++;
        sysctl_ctx_init(&rs->sysctl_ctx);
        rl_sysctl_root = SYSCTL_ADD_NODE(&rs->sysctl_ctx,
            SYSCTL_STATIC_CHILDREN(_net_inet_tcp_rl),
            OID_AUTO,
            rs->rs_ifp->if_xname,
            CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
            "");
        rl_add_syctl_entries(rl_sysctl_root, rs);
        NET_EPOCH_ENTER(et);
        mtx_lock(&rs_mtx);
        CK_LIST_INSERT_HEAD(&int_rs, rs, next);
        mtx_unlock(&rs_mtx);
        NET_EPOCH_EXIT(et);
        return (rs);
}

/*
 * For an explanation of why the argument is volatile please
 * look at the comments around rt_setup_rate().
 */
static const struct tcp_hwrate_limit_table *
tcp_int_find_suitable_rate(const volatile struct tcp_rate_set *rs,
    uint64_t bytes_per_sec, uint32_t flags, uint64_t *lower_rate)
{
        struct tcp_hwrate_limit_table *arte = NULL, *rte = NULL;
        uint64_t mbits_per_sec, ind_calc, previous_rate = 0;
        int i;

        mbits_per_sec = (bytes_per_sec * 8);
        if (flags & RS_PACING_LT) {
                if ((mbits_per_sec < RS_ONE_MEGABIT_PERSEC) &&
                    (rs->rs_lowest_valid <= 2)){
                        /*
                         * Smaller than 1Meg, only
                         * 3 entries can match it.
                         */
                        previous_rate = 0;
                        for(i = rs->rs_lowest_valid; i < 3; i++) {
                                if (bytes_per_sec <= rs->rs_rlt[i].rate) {
                                        rte = &rs->rs_rlt[i];
                                        break;
                                } else if (rs->rs_rlt[i].flags & HDWRPACE_INITED) {
                                        arte = &rs->rs_rlt[i];
                                }
                                previous_rate = rs->rs_rlt[i].rate;
                        }
                        goto done;
                } else if ((mbits_per_sec > RS_ONE_GIGABIT_PERSEC) &&
                           (rs->rs_rlt[(ALL_HARDWARE_RATES-1)].flags & HDWRPACE_INITED)){
                        /*
                         * Larger than 1G (the majority of
                         * our table.
                         */
                        if (mbits_per_sec < RS_TEN_GIGABIT_PERSEC)
                                rte = &rs->rs_rlt[(ALL_HARDWARE_RATES-1)];
                        else
                                arte = &rs->rs_rlt[(ALL_HARDWARE_RATES-1)];
                        previous_rate = rs->rs_rlt[(ALL_HARDWARE_RATES-2)].rate;
                        goto done;
                }
                /*
                 * If we reach here its in our table (between 1Meg - 1000Meg),
                 * just take the rounded down mbits per second, and add
                 * 1Megabit to it, from this we can calculate
                 * the index in the table.
                 */
                ind_calc = mbits_per_sec/RS_ONE_MEGABIT_PERSEC;
                if ((ind_calc * RS_ONE_MEGABIT_PERSEC) != mbits_per_sec)
                        ind_calc++;
                /* our table is offset by 3, we add 2 */
                ind_calc += 2;
                if (ind_calc > (ALL_HARDWARE_RATES-1)) {
                        /* This should not happen */
                        ind_calc = ALL_HARDWARE_RATES-1;
                }
                if ((ind_calc >= rs->rs_lowest_valid) &&
                    (ind_calc <= rs->rs_highest_valid)) {
                        rte = &rs->rs_rlt[ind_calc];
                        if (ind_calc >= 1)
                                previous_rate = rs->rs_rlt[(ind_calc-1)].rate;
                }
        } else if (flags & RS_PACING_EXACT_MATCH) {
                if ((mbits_per_sec < RS_ONE_MEGABIT_PERSEC) &&
                    (rs->rs_lowest_valid <= 2)){
                        for(i = rs->rs_lowest_valid; i < 3; i++) {
                                if (bytes_per_sec == rs->rs_rlt[i].rate) {
                                        rte = &rs->rs_rlt[i];
                                        break;
                                }
                        }
                } else if ((mbits_per_sec > RS_ONE_GIGABIT_PERSEC) &&
                           (rs->rs_rlt[(ALL_HARDWARE_RATES-1)].flags & HDWRPACE_INITED)) {
                        /* > 1Gbps only one rate */
                        if (bytes_per_sec == rs->rs_rlt[(ALL_HARDWARE_RATES-1)].rate) {
                                /* Its 10G wow */
                                rte = &rs->rs_rlt[(ALL_HARDWARE_RATES-1)];
                        }
                } else {
                        /* Ok it must be a exact meg (its between 1G and 1Meg) */
                        ind_calc = mbits_per_sec/RS_ONE_MEGABIT_PERSEC;
                        if ((ind_calc * RS_ONE_MEGABIT_PERSEC) == mbits_per_sec) {
                                /* its an exact Mbps */
                                ind_calc += 2;
                                if (ind_calc > (ALL_HARDWARE_RATES-1)) {
                                        /* This should not happen */
                                        ind_calc = ALL_HARDWARE_RATES-1;
                                }
                                if (rs->rs_rlt[ind_calc].flags & HDWRPACE_INITED)
                                        rte = &rs->rs_rlt[ind_calc];
                        }
                }
        } else {
                /* we want greater than the requested rate */
                if ((mbits_per_sec < RS_ONE_MEGABIT_PERSEC) &&
                    (rs->rs_lowest_valid <= 2)){
                        arte = &rs->rs_rlt[3]; /* set alternate to 1Meg */
                        for (i=2; i>=rs->rs_lowest_valid; i--) {
                                if (bytes_per_sec < rs->rs_rlt[i].rate) {
                                        rte = &rs->rs_rlt[i];
                                        if (i >= 1) {
                                                previous_rate = rs->rs_rlt[(i-1)].rate;
                                        }
                                        break;
                                } else if ((flags & RS_PACING_GEQ) &&
                                           (bytes_per_sec == rs->rs_rlt[i].rate)) {
                                        rte = &rs->rs_rlt[i];
                                        if (i >= 1) {
                                                previous_rate = rs->rs_rlt[(i-1)].rate;
                                        }
                                        break;
                                } else {
                                        arte = &rs->rs_rlt[i]; /* new alternate */
                                }
                        }
                } else if (mbits_per_sec > RS_ONE_GIGABIT_PERSEC) {
                        if ((bytes_per_sec < rs->rs_rlt[(ALL_HARDWARE_RATES-1)].rate) &&
                            (rs->rs_rlt[(ALL_HARDWARE_RATES-1)].flags & HDWRPACE_INITED)){
                                /* Our top rate is larger than the request */
                                rte = &rs->rs_rlt[(ALL_HARDWARE_RATES-1)];
                        } else if ((flags & RS_PACING_GEQ) &&
                                   (bytes_per_sec == rs->rs_rlt[(ALL_HARDWARE_RATES-1)].rate) &&
                                   (rs->rs_rlt[(ALL_HARDWARE_RATES-1)].flags & HDWRPACE_INITED)) {
                                /* It matches our top rate */
                                rte = &rs->rs_rlt[(ALL_HARDWARE_RATES-1)];
                        } else if (rs->rs_rlt[(ALL_HARDWARE_RATES-1)].flags & HDWRPACE_INITED) {
                                /* The top rate is an alternative */
                                arte = &rs->rs_rlt[(ALL_HARDWARE_RATES-1)];
                        }
                        previous_rate = rs->rs_rlt[(ALL_HARDWARE_RATES-2)].rate;
                } else {
                        /* Its in our range 1Meg - 1Gig */
                        if (flags & RS_PACING_GEQ) {
                                ind_calc = mbits_per_sec/RS_ONE_MEGABIT_PERSEC;
                                if ((ind_calc * RS_ONE_MEGABIT_PERSEC) == mbits_per_sec) {
                                        if (ind_calc > (ALL_HARDWARE_RATES-1)) {
                                                /* This should not happen */
                                                ind_calc = (ALL_HARDWARE_RATES-1);
                                        }
                                        rte = &rs->rs_rlt[ind_calc];
                                        if (ind_calc >= 1)
                                                previous_rate = rs->rs_rlt[(ind_calc-1)].rate;
                                }
                                goto done;
                        }
                        ind_calc = (mbits_per_sec + (RS_ONE_MEGABIT_PERSEC-1))/RS_ONE_MEGABIT_PERSEC;
                        ind_calc += 2;
                        if (ind_calc > (ALL_HARDWARE_RATES-1)) {
                                /* This should not happen */
                                ind_calc = ALL_HARDWARE_RATES-1;
                        }
                        if (rs->rs_rlt[ind_calc].flags & HDWRPACE_INITED) {
                                rte = &rs->rs_rlt[ind_calc];
                                if (ind_calc >= 1)
                                        previous_rate = rs->rs_rlt[(ind_calc-1)].rate;
                        }
                }
        }
done:
        if ((rte == NULL) &&
            (arte != NULL) &&
            (flags & RS_PACING_SUB_OK)) {
                /* We can use the substitute */
                rte = arte;
        }
        if (lower_rate)
                *lower_rate = previous_rate;
        return (rte);
}

/*
 * For an explanation of why the argument is volatile please
 * look at the comments around rt_setup_rate().
 */
static const struct tcp_hwrate_limit_table *
tcp_find_suitable_rate(const volatile struct tcp_rate_set *rs, uint64_t bytes_per_sec, uint32_t flags, uint64_t *lower_rate)
{
        /**
         * Hunt the rate table with the restrictions in flags and find a
         * suitable rate if possible.
         * RS_PACING_EXACT_MATCH - look for an exact match to rate.
         * RS_PACING_GT     - must be greater than.
         * RS_PACING_GEQ    - must be greater than or equal.
         * RS_PACING_LT     - must be less than.
         * RS_PACING_SUB_OK - If we don't meet criteria a
         *                    substitute is ok.
         */
        int i, matched;
        struct tcp_hwrate_limit_table *rte = NULL;
        uint64_t previous_rate = 0;

        if ((rs->rs_flags & RS_INT_TBL) &&
            (rs->rs_rate_cnt >= ALL_HARDWARE_RATES)) {
                /*
                 * Here we don't want to paw thru
                 * a big table, we have everything
                 * from 1Meg - 1000Meg in 1Meg increments.
                 * Use an alternate method to "lookup".
                 */
                return (tcp_int_find_suitable_rate(rs, bytes_per_sec, flags, lower_rate));
        }
        if ((flags & RS_PACING_LT) ||
            (flags & RS_PACING_EXACT_MATCH)) {
                /*
                 * For exact and less than we go forward through the table.
                 * This way when we find one larger we stop (exact was a
                 * toss up).
                 */
                for (i = rs->rs_lowest_valid, matched = 0; i <= rs->rs_highest_valid; i++) {
                        if ((flags & RS_PACING_EXACT_MATCH) &&
                            (bytes_per_sec == rs->rs_rlt[i].rate)) {
                                rte = &rs->rs_rlt[i];
                                matched = 1;
                                if (lower_rate != NULL)
                                        *lower_rate = previous_rate;
                                break;
                        } else if ((flags & RS_PACING_LT) &&
                            (bytes_per_sec <= rs->rs_rlt[i].rate)) {
                                rte = &rs->rs_rlt[i];
                                matched = 1;
                                if (lower_rate != NULL)
                                        *lower_rate = previous_rate;
                                break;
                        }
                        previous_rate = rs->rs_rlt[i].rate;
                        if (bytes_per_sec > rs->rs_rlt[i].rate)
                                break;
                }
                if ((matched == 0) &&
                    (flags & RS_PACING_LT) &&
                    (flags & RS_PACING_SUB_OK)) {
                        /* Kick in a substitute (the lowest) */
                        rte = &rs->rs_rlt[rs->rs_lowest_valid];
                }
        } else {
                /*
                 * Here we go backward through the table so that we can find
                 * the one greater in theory faster (but its probably a
                 * wash).
                 */
                for (i = rs->rs_highest_valid, matched = 0; i >= rs->rs_lowest_valid; i--) {
                        if (rs->rs_rlt[i].rate > bytes_per_sec) {
                                /* A possible candidate */
                                rte = &rs->rs_rlt[i];
                        }
                        if ((flags & RS_PACING_GEQ) &&
                            (bytes_per_sec == rs->rs_rlt[i].rate)) {
                                /* An exact match and we want equal */
                                matched = 1;
                                rte = &rs->rs_rlt[i];
                                break;
                        } else if (rte) {
                                /*
                                 * Found one that is larger than but don't
                                 * stop, there may be a more closer match.
                                 */
                                matched = 1;
                        }
                        if (rs->rs_rlt[i].rate < bytes_per_sec) {
                                /*
                                 * We found a table entry that is smaller,
                                 * stop there will be none greater or equal.
                                 */
                                if (lower_rate != NULL)
                                        *lower_rate = rs->rs_rlt[i].rate;
                                break;
                        }
                }
                if ((matched == 0) &&
                    (flags & RS_PACING_SUB_OK)) {
                        /* Kick in a substitute (the highest) */
                        rte = &rs->rs_rlt[rs->rs_highest_valid];
                }
        }
        return (rte);
}

static struct ifnet *
rt_find_real_interface(struct ifnet *ifp, struct inpcb *inp, int *error)
{
        struct ifnet *tifp;
        struct m_snd_tag *tag, *ntag;
        union if_snd_tag_alloc_params params = {
                .rate_limit.hdr.type = IF_SND_TAG_TYPE_RATE_LIMIT,
                .rate_limit.hdr.flowid = inp->inp_flowid,
                .rate_limit.hdr.numa_domain = inp->inp_numa_domain,
                .rate_limit.max_rate = COMMON_RATE,
                .rate_limit.flags = M_NOWAIT,
        };
        int err;
#ifdef RSS
        params.rate_limit.hdr.flowtype = ((inp->inp_vflag & INP_IPV6) ?
            M_HASHTYPE_RSS_TCP_IPV6 : M_HASHTYPE_RSS_TCP_IPV4);
#else
        params.rate_limit.hdr.flowtype = M_HASHTYPE_OPAQUE_HASH;
#endif
        err = m_snd_tag_alloc(ifp, &params, &tag);
        if (err) {
                /* Failed to setup a tag? */
                if (error)
                        *error = err;
                return (NULL);
        }
        ntag = tag;
        while (ntag->sw->next_snd_tag != NULL) {
                ntag = ntag->sw->next_snd_tag(ntag);
        }
        tifp = ntag->ifp;
        m_snd_tag_rele(tag);
        return (tifp);
}

static void
rl_increment_using(const struct tcp_hwrate_limit_table *rte)
{
        struct tcp_hwrate_limit_table *decon_rte;

        decon_rte = __DECONST(struct tcp_hwrate_limit_table *, rte);
        atomic_add_long(&decon_rte->using, 1);
}

static void
rl_decrement_using(const struct tcp_hwrate_limit_table *rte)
{
        struct tcp_hwrate_limit_table *decon_rte;

        decon_rte = __DECONST(struct tcp_hwrate_limit_table *, rte);
        atomic_subtract_long(&decon_rte->using, 1);
}

void
tcp_rl_log_enobuf(const struct tcp_hwrate_limit_table *rte)
{
        struct tcp_hwrate_limit_table *decon_rte;

        decon_rte = __DECONST(struct tcp_hwrate_limit_table *, rte);
        atomic_add_long(&decon_rte->rs_num_enobufs, 1);
}

/*
 * Do NOT take the __noinline out of the
 * find_rs_for_ifp() function. If you do the inline
 * of it for the rt_setup_rate() will show you a
 * compiler bug. For some reason the compiler thinks
 * the list can never be empty. The consequence of
 * this will be a crash when we dereference NULL
 * if an ifp is removed just has a hw rate limit
 * is attempted. If you are working on the compiler
 * and want to "test" this go ahead and take the noinline
 * out otherwise let sleeping dogs ly until such time
 * as we get a compiler fix 10/2/20 -- RRS
 */
static __noinline struct tcp_rate_set *
find_rs_for_ifp(struct ifnet *ifp)
{
        struct tcp_rate_set *rs;

        CK_LIST_FOREACH(rs, &int_rs, next) {
                if ((rs->rs_ifp == ifp) &&
                    (rs->rs_if_dunit == ifp->if_dunit)) {
                        /* Ok we found it */
                        return (rs);
                }
        }
        return (NULL);
}


static const struct tcp_hwrate_limit_table *
rt_setup_rate(struct inpcb *inp, struct ifnet *ifp, uint64_t bytes_per_sec,
    uint32_t flags, int *error, uint64_t *lower_rate)
{
        /* First lets find the interface if it exists */
        const struct tcp_hwrate_limit_table *rte;
        /*
         * So why is rs volatile? This is to defeat a
         * compiler bug where in the compiler is convinced
         * that rs can never be NULL (which is not true). Because
         * of its conviction it nicely optimizes out the if ((rs == NULL
         * below which means if you get a NULL back you dereference it.
         */
        volatile struct tcp_rate_set *rs;
        struct epoch_tracker et;
        struct ifnet *oifp = ifp;
        int err;

        NET_EPOCH_ENTER(et);
use_real_interface:
        rs = find_rs_for_ifp(ifp);
        if ((rs == NULL) ||
            (rs->rs_flags & RS_INTF_NO_SUP) ||
            (rs->rs_flags & RS_IS_DEAD)) {
                /*
                 * This means we got a packet *before*
                 * the IF-UP was processed below, <or>
                 * while or after we already received an interface
                 * departed event. In either case we really don't
                 * want to do anything with pacing, in
                 * the departing case the packet is not
                 * going to go very far. The new case
                 * might be arguable, but its impossible
                 * to tell from the departing case.
                 */
                if (error)
                        *error = ENODEV;
                NET_EPOCH_EXIT(et);
                return (NULL);
        }

        if ((rs == NULL) || (rs->rs_disable != 0)) {
                if (error)
                        *error = ENOSPC;
                NET_EPOCH_EXIT(et);
                return (NULL);
        }
        if (rs->rs_flags & RS_IS_DEFF) {
                /* We need to find the real interface */
                struct ifnet *tifp;

                tifp = rt_find_real_interface(ifp, inp, error);
                if (tifp == NULL) {
                        if (rs->rs_disable && error)
                                *error = ENOTSUP;
                        NET_EPOCH_EXIT(et);
                        return (NULL);
                }
                KASSERT((tifp != ifp),
                        ("Lookup failure ifp:%p inp:%p rt_find_real_interface() returns the same interface tifp:%p?\n",
                         ifp, inp, tifp));
                ifp = tifp;
                goto use_real_interface;
        }
        if (rs->rs_flow_limit &&
            ((rs->rs_flows_using + 1) > rs->rs_flow_limit)) {
                if (error)
                        *error = ENOSPC;
                NET_EPOCH_EXIT(et);
                return (NULL);
        }
        rte = tcp_find_suitable_rate(rs, bytes_per_sec, flags, lower_rate);
        if (rte) {
                err = in_pcbattach_txrtlmt(inp, oifp,
                    inp->inp_flowtype,
                    inp->inp_flowid,
                    rte->rate,
                    &inp->inp_snd_tag);
                if (err) {
                        /* Failed to attach */
                        if (error)
                                *error = err;
                        rte = NULL;
                } else {
                        KASSERT((inp->inp_snd_tag != NULL) ,
                                ("Setup rate has no snd_tag inp:%p rte:%p rate:%llu rs:%p",
                                 inp, rte, (unsigned long long)rte->rate, rs));
#ifdef INET
                        counter_u64_add(rate_limit_new, 1);
#endif
                }
        }
        if (rte) {
                /*
                 * We use an atomic here for accounting so we don't have to
                 * use locks when freeing.
                 */
                atomic_add_64(&rs->rs_flows_using, 1);
        }
        NET_EPOCH_EXIT(et);
        return (rte);
}

static void
tcp_rl_ifnet_link(void *arg __unused, struct ifnet *ifp, int link_state)
{
        int error;
        struct tcp_rate_set *rs;
        struct epoch_tracker et;

        if (((ifp->if_capenable & IFCAP_TXRTLMT) == 0) ||
            (link_state != LINK_STATE_UP)) {
                /*
                 * We only care on an interface going up that is rate-limit
                 * capable.
                 */
                return;
        }
        NET_EPOCH_ENTER(et);
        mtx_lock(&rs_mtx);
        rs = find_rs_for_ifp(ifp);
        if (rs) {
                /* We already have initialized this guy */
                mtx_unlock(&rs_mtx);
                NET_EPOCH_EXIT(et);
                return;
        }
        mtx_unlock(&rs_mtx);
        NET_EPOCH_EXIT(et);
        rt_setup_new_rs(ifp, &error);
}

static void
tcp_rl_ifnet_departure(void *arg __unused, struct ifnet *ifp)
{
        struct tcp_rate_set *rs;
        struct epoch_tracker et;
        int i;

        NET_EPOCH_ENTER(et);
        mtx_lock(&rs_mtx);
        rs = find_rs_for_ifp(ifp);
        if (rs) {
                CK_LIST_REMOVE(rs, next);
                rs_number_alive--;
                rs->rs_flags |= RS_IS_DEAD;
                for (i = 0; i < rs->rs_rate_cnt; i++) {
                        if (rs->rs_rlt[i].flags & HDWRPACE_TAGPRESENT) {
                                in_pcbdetach_tag(rs->rs_rlt[i].tag);
                                rs->rs_rlt[i].tag = NULL;
                        }
                        rs->rs_rlt[i].flags = HDWRPACE_IFPDEPARTED;
                }
                if (rs->rs_flows_using == 0)
                        rs_defer_destroy(rs);
        }
        mtx_unlock(&rs_mtx);
        NET_EPOCH_EXIT(et);
}

void
tcp_rl_release_ifnet(struct ifnet *ifp)
{
        tcp_rl_ifnet_departure(NULL, ifp);
}

static void
tcp_rl_shutdown(void *arg __unused, int howto __unused)
{
        struct tcp_rate_set *rs, *nrs;
        struct epoch_tracker et;
        int i;

        NET_EPOCH_ENTER(et);
        mtx_lock(&rs_mtx);
        CK_LIST_FOREACH_SAFE(rs, &int_rs, next, nrs) {
                CK_LIST_REMOVE(rs, next);
                rs_number_alive--;
                rs->rs_flags |= RS_IS_DEAD;
                for (i = 0; i < rs->rs_rate_cnt; i++) {
                        if (rs->rs_rlt[i].flags & HDWRPACE_TAGPRESENT) {
                                in_pcbdetach_tag(rs->rs_rlt[i].tag);
                                rs->rs_rlt[i].tag = NULL;
                        }
                        rs->rs_rlt[i].flags = HDWRPACE_IFPDEPARTED;
                }
                if (rs->rs_flows_using == 0)
                        rs_defer_destroy(rs);
        }
        mtx_unlock(&rs_mtx);
        NET_EPOCH_EXIT(et);
}

const struct tcp_hwrate_limit_table *
tcp_set_pacing_rate(struct tcpcb *tp, struct ifnet *ifp,
    uint64_t bytes_per_sec, int flags, int *error, uint64_t *lower_rate)
{
        struct inpcb *inp = tptoinpcb(tp);
        const struct tcp_hwrate_limit_table *rte;
#ifdef KERN_TLS
        struct ktls_session *tls;
#endif

        INP_WLOCK_ASSERT(inp);

        if (inp->inp_snd_tag == NULL) {
                /*
                 * We are setting up a rate for the first time.
                 */
                if ((ifp->if_capenable & IFCAP_TXRTLMT) == 0) {
                        /* Not supported by the egress */
                        if (error)
                                *error = ENODEV;
                        return (NULL);
                }
#ifdef KERN_TLS
                tls = NULL;
                if (tp->t_nic_ktls_xmit != 0) {
                        tls = tptosocket(tp)->so_snd.sb_tls_info;

                        if ((ifp->if_capenable & IFCAP_TXTLS_RTLMT) == 0 ||
                            tls->mode != TCP_TLS_MODE_IFNET) {
                                if (error)
                                        *error = ENODEV;
                                return (NULL);
                        }
                }
#endif
                rte = rt_setup_rate(inp, ifp, bytes_per_sec, flags, error, lower_rate);
                if (rte)
                        rl_increment_using(rte);
#ifdef KERN_TLS
                if (rte != NULL && tls != NULL && tls->snd_tag != NULL) {
                        /*
                         * Fake a route change error to reset the TLS
                         * send tag.  This will convert the existing
                         * tag to a TLS ratelimit tag.
                         */
                        MPASS(tls->snd_tag->sw->type == IF_SND_TAG_TYPE_TLS);
                        ktls_output_eagain(inp, tls);
                }
#endif
        } else {
                /*
                 * We are modifying a rate, wrong interface?
                 */
                if (error)
                        *error = EINVAL;
                rte = NULL;
        }
        if (rte != NULL) {
                tp->t_pacing_rate = rte->rate;
                *error = 0;
        }
        return (rte);
}

const struct tcp_hwrate_limit_table *
tcp_chg_pacing_rate(const struct tcp_hwrate_limit_table *crte,
    struct tcpcb *tp, struct ifnet *ifp,
    uint64_t bytes_per_sec, int flags, int *error, uint64_t *lower_rate)
{
        struct inpcb *inp = tptoinpcb(tp);
        const struct tcp_hwrate_limit_table *nrte;
        const struct tcp_rate_set *rs;
#ifdef KERN_TLS
        struct ktls_session *tls = NULL;
#endif
        int err;

        INP_WLOCK_ASSERT(inp);

        if (crte == NULL) {
                /* Wrong interface */
                if (error)
                        *error = EINVAL;
                return (NULL);
        }

#ifdef KERN_TLS
        if (tp->t_nic_ktls_xmit) {
                tls = tptosocket(tp)->so_snd.sb_tls_info;
                if (tls->mode != TCP_TLS_MODE_IFNET)
                        tls = NULL;
                else if (tls->snd_tag != NULL &&
                    tls->snd_tag->sw->type != IF_SND_TAG_TYPE_TLS_RATE_LIMIT) {
                        if (!tls->reset_pending) {
                                /*
                                 * NIC probably doesn't support
                                 * ratelimit TLS tags if it didn't
                                 * allocate one when an existing rate
                                 * was present, so ignore.
                                 */
                                tcp_rel_pacing_rate(crte, tp);
                                if (error)
                                        *error = EOPNOTSUPP;
                                return (NULL);
                        }

                        /*
                         * The send tag is being converted, so set the
                         * rate limit on the inpcb tag.  There is a
                         * race that the new NIC send tag might use
                         * the current rate instead of this one.
                         */
                        tls = NULL;
                }
        }
#endif
        if (inp->inp_snd_tag == NULL) {
                /* Wrong interface */
                tcp_rel_pacing_rate(crte, tp);
                if (error)
                        *error = EINVAL;
                return (NULL);
        }
        rs = crte->ptbl;
        if ((rs->rs_flags & RS_IS_DEAD) ||
            (crte->flags & HDWRPACE_IFPDEPARTED)) {
                /* Release the rate, and try anew */

                tcp_rel_pacing_rate(crte, tp);
                nrte = tcp_set_pacing_rate(tp, ifp,
                    bytes_per_sec, flags, error, lower_rate);
                return (nrte);
        }
        nrte = tcp_find_suitable_rate(rs, bytes_per_sec, flags, lower_rate);
        if (nrte == crte) {
                /* No change */
                if (error)
                        *error = 0;
                return (crte);
        }
        if (nrte == NULL) {
                /* Release the old rate */
                if (error)
                        *error = ENOENT;
                tcp_rel_pacing_rate(crte, tp);
                return (NULL);
        }
        rl_decrement_using(crte);
        rl_increment_using(nrte);
        /* Change rates to our new entry */
#ifdef KERN_TLS
        if (tls != NULL)
                err = ktls_modify_txrtlmt(tls, nrte->rate);
        else
#endif
                err = in_pcbmodify_txrtlmt(inp, nrte->rate);
        if (err) {
                struct tcp_rate_set *lrs;
                uint64_t pre;

                rl_decrement_using(nrte);
                lrs = __DECONST(struct tcp_rate_set *, rs);
                pre = atomic_fetchadd_64(&lrs->rs_flows_using, -1);
                /* Do we still have a snd-tag attached? */
                if (inp->inp_snd_tag)
                        in_pcbdetach_txrtlmt(inp);

                if (pre == 1) {
                        struct epoch_tracker et;

                        NET_EPOCH_ENTER(et);
                        mtx_lock(&rs_mtx);
                        /*
                         * Is it dead?
                         */
                        if (lrs->rs_flags & RS_IS_DEAD)
                                rs_defer_destroy(lrs);
                        mtx_unlock(&rs_mtx);
                        NET_EPOCH_EXIT(et);
                }
                if (error)
                        *error = err;
                return (NULL);
        } else {
#ifdef INET
                counter_u64_add(rate_limit_chg, 1);
#endif
        }
        if (error)
                *error = 0;
        tp->t_pacing_rate = nrte->rate;
        return (nrte);
}

void
tcp_rel_pacing_rate(const struct tcp_hwrate_limit_table *crte, struct tcpcb *tp)
{
        struct inpcb *inp = tptoinpcb(tp);
        const struct tcp_rate_set *crs;
        struct tcp_rate_set *rs;
        uint64_t pre;

        INP_WLOCK_ASSERT(inp);

        tp->t_pacing_rate = -1;
        crs = crte->ptbl;
        /*
         * Now we must break the const
         * in order to release our refcount.
         */
        rs = __DECONST(struct tcp_rate_set *, crs);
        rl_decrement_using(crte);
        pre = atomic_fetchadd_64(&rs->rs_flows_using, -1);
        if (pre == 1) {
                struct epoch_tracker et;

                NET_EPOCH_ENTER(et);
                mtx_lock(&rs_mtx);
                /*
                 * Is it dead?
                 */
                if (rs->rs_flags & RS_IS_DEAD)
                        rs_defer_destroy(rs);
                mtx_unlock(&rs_mtx);
                NET_EPOCH_EXIT(et);
        }

        /*
         * XXX: If this connection is using ifnet TLS, should we
         * switch it to using an unlimited rate, or perhaps use
         * ktls_output_eagain() to reset the send tag to a plain
         * TLS tag?
         */
        in_pcbdetach_txrtlmt(inp);
}

#define ONE_POINT_TWO_MEG 150000 /* 1.2 megabits in bytes */
#define ONE_HUNDRED_MBPS 12500000       /* 100Mbps in bytes per second */
#define FIVE_HUNDRED_MBPS 62500000      /* 500Mbps in bytes per second */
#define MAX_MSS_SENT 43 /* 43 mss = 43 x 1500 = 64,500 bytes */

static void
tcp_log_pacing_size(struct tcpcb *tp, uint64_t bw, uint32_t segsiz, uint32_t new_tso,
                    uint64_t hw_rate, uint32_t time_between, uint32_t calc_time_between,
                    uint32_t segs, uint32_t res_div, uint16_t mult, uint8_t mod)
{
        if (tcp_bblogging_on(tp)) {
                union tcp_log_stackspecific log;
                struct timeval tv;

                memset(&log, 0, sizeof(log));
                log.u_bbr.flex1 = segsiz;
                log.u_bbr.flex2 = new_tso;
                log.u_bbr.flex3 = time_between;
                log.u_bbr.flex4 = calc_time_between;
                log.u_bbr.flex5 = segs;
                log.u_bbr.flex6 = res_div;
                log.u_bbr.flex7 = mult;
                log.u_bbr.flex8 = mod;
                log.u_bbr.timeStamp = tcp_get_usecs(&tv);
                log.u_bbr.cur_del_rate = bw;
                log.u_bbr.delRate = hw_rate;
                TCP_LOG_EVENTP(tp, NULL,
                    &tptosocket(tp)->so_rcv,
                    &tptosocket(tp)->so_snd,
                    TCP_HDWR_PACE_SIZE, 0,
                    0, &log, false, &tv);
        }
}

uint32_t
tcp_get_pacing_burst_size_w_divisor(struct tcpcb *tp, uint64_t bw, uint32_t segsiz, int can_use_1mss,
   const struct tcp_hwrate_limit_table *te, int *err, int divisor)
{
        /*
         * We use the google formula to calculate the
         * TSO size. I.E.
         * bw < 24Meg
         *   tso = 2mss
         * else
         *   tso = min(bw/(div=1000), 64k)
         *
         * Note for these calculations we ignore the
         * packet overhead (enet hdr, ip hdr and tcp hdr).
         * We only get the google formula when we have
         * divisor = 1000, which is the default for now.
         */
        uint64_t lentim, res, bytes;
        uint32_t new_tso, min_tso_segs;

        /* It can't be zero */
        if ((divisor == 0) ||
            (divisor < RL_MIN_DIVISOR)) {
                if (mss_divisor)
                        bytes = bw / mss_divisor;
                else
                        bytes = bw / 1000;
        } else
                bytes = bw / divisor;
        /* We can't ever send more than 65k in a TSO */
        if (bytes > 0xffff) {
                bytes = 0xffff;
        }
        /* Round up */
        new_tso = (bytes + segsiz - 1) / segsiz;
        /* Are we enforcing even boundaries? */
        if (even_num_segs && (new_tso & 1) && (new_tso > even_threshold))
                new_tso++;
        if (can_use_1mss)
                min_tso_segs = 1;
        else
                min_tso_segs = 2;
        if (rs_floor_mss && (new_tso < rs_floor_mss))
                new_tso = rs_floor_mss;
        else if (new_tso < min_tso_segs)
                new_tso = min_tso_segs;
        if (new_tso > MAX_MSS_SENT)
                new_tso = MAX_MSS_SENT;
        new_tso *= segsiz;
        tcp_log_pacing_size(tp, bw, segsiz, new_tso,
                            0, 0, 0, 0, 0, 0, 1);
        /*
         * If we are not doing hardware pacing
         * then we are done.
         */
        if (te == NULL) {
                if (err)
                        *err = 0;
                return(new_tso);
        }
        /*
         * For hardware pacing we look at the
         * rate you are sending at and compare
         * that to the rate you have in hardware.
         *
         * If the hardware rate is slower than your
         * software rate then you are in error and
         * we will build a queue in our hardware whic
         * is probably not desired, in such a case
         * just return the non-hardware TSO size.
         *
         * If the rate in hardware is faster (which
         * it should be) then look at how long it
         * takes to send one ethernet segment size at
         * your b/w and compare that to the time it
         * takes to send at the rate you had selected.
         *
         * If your time is greater (which we hope it is)
         * we get the delta between the two, and then
         * divide that into your pacing time. This tells
         * us how many MSS you can send down at once (rounded up).
         *
         * Note we also double this value if the b/w is over
         * 100Mbps. If its over 500meg we just set you to the
         * max (43 segments).
         */
        if (te->rate > FIVE_HUNDRED_MBPS)
                goto max;
        if (te->rate == bw) {
                /* We are pacing at exactly the hdwr rate */
max:
                tcp_log_pacing_size(tp, bw, segsiz, new_tso,
                                    te->rate, te->time_between, (uint32_t)0,
                                    (segsiz * MAX_MSS_SENT), 0, 0, 3);
                return (segsiz * MAX_MSS_SENT);
        }
        lentim = ETHERNET_SEGMENT_SIZE * USECS_IN_SECOND;
        res = lentim / bw;
        if (res > te->time_between) {
                uint32_t delta, segs, res_div;

                res_div = ((res * num_of_waits_allowed) + wait_time_floor);
                delta = res - te->time_between;
                segs = (res_div + delta - 1)/delta;
                if (segs < min_tso_segs)
                        segs = min_tso_segs;
                if (segs < rs_hw_floor_mss)
                        segs = rs_hw_floor_mss;
                if (segs > MAX_MSS_SENT)
                        segs = MAX_MSS_SENT;
                segs *= segsiz;
                tcp_log_pacing_size(tp, bw, segsiz, new_tso,
                                    te->rate, te->time_between, (uint32_t)res,
                                    segs, res_div, 1, 3);
                if (err)
                        *err = 0;
                if (segs < new_tso) {
                        /* unexpected ? */
                        return(new_tso);
                } else {
                        return (segs);
                }
        } else {
                /*
                 * Your time is smaller which means
                 * we will grow a queue on our
                 * hardware. Send back the non-hardware
                 * rate.
                 */
                tcp_log_pacing_size(tp, bw, segsiz, new_tso,
                                    te->rate, te->time_between, (uint32_t)res,
                                    0, 0, 0, 4);
                if (err)
                        *err = -1;
                return (new_tso);
        }
}

uint64_t
tcp_hw_highest_rate_ifp(struct ifnet *ifp, struct inpcb *inp)
{
        struct epoch_tracker et;
        struct tcp_rate_set *rs;
        uint64_t rate_ret;

        NET_EPOCH_ENTER(et);
use_next_interface:
        rs = find_rs_for_ifp(ifp);
        if (rs == NULL) {
                /* This interface does not do ratelimiting */
                rate_ret = 0;
        } else if (rs->rs_flags & RS_IS_DEFF) {
                /* We need to find the real interface */
                struct ifnet *tifp;

                tifp = rt_find_real_interface(ifp, inp, NULL);
                if (tifp == NULL) {
                        NET_EPOCH_EXIT(et);
                        return (0);
                }
                ifp = tifp;
                goto use_next_interface;
        } else {
                /* Lets return the highest rate this guy has */
                rate_ret = rs->rs_rlt[rs->rs_highest_valid].rate;
        }
        NET_EPOCH_EXIT(et);
        return(rate_ret);
}

static eventhandler_tag rl_ifnet_departs;
static eventhandler_tag rl_ifnet_arrives;
static eventhandler_tag rl_shutdown_start;

static void
tcp_rs_init(void *st __unused)
{
        CK_LIST_INIT(&int_rs);
        rs_number_alive = 0;
        rs_number_dead = 0;
        mtx_init(&rs_mtx, "tcp_rs_mtx", "rsmtx", MTX_DEF);
        rl_ifnet_departs = EVENTHANDLER_REGISTER(ifnet_departure_event,
            tcp_rl_ifnet_departure,
            NULL, EVENTHANDLER_PRI_ANY);
        rl_ifnet_arrives = EVENTHANDLER_REGISTER(ifnet_link_event,
            tcp_rl_ifnet_link,
            NULL, EVENTHANDLER_PRI_ANY);
        rl_shutdown_start = EVENTHANDLER_REGISTER(shutdown_pre_sync,
            tcp_rl_shutdown, NULL,
            SHUTDOWN_PRI_FIRST);
        printf("TCP_ratelimit: Is now initialized\n");
}

SYSINIT(tcp_rl_init, SI_SUB_SMP + 1, SI_ORDER_ANY, tcp_rs_init, NULL);
#endif