sctp_ss_functions.c

Go to the documentation of this file.

/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2010-2012, by Michael Tuexen. All rights reserved.
 * Copyright (c) 2010-2012, by Randall Stewart. All rights reserved.
 * Copyright (c) 2010-2012, by Robin Seggelmann. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * a) Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * b) 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 COPYRIGHT HOLDERS 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 COPYRIGHT OWNER 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.
 */
 
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
 
#include <netinet/sctp_pcb.h>
 
/*
 * Default simple round-robin algorithm.
 * Just interates the streams in the order they appear.
 */
 
static void
sctp_ss_default_add(struct sctp_tcb *, struct sctp_association *,
    struct sctp_stream_out *,
    struct sctp_stream_queue_pending *);
 
static void
sctp_ss_default_remove(struct sctp_tcb *, struct sctp_association *,
    struct sctp_stream_out *,
    struct sctp_stream_queue_pending *);
 
static void
sctp_ss_default_init(struct sctp_tcb *stcb, struct sctp_association *asoc)
{
        uint16_t i;
 
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        asoc->ss_data.locked_on_sending = NULL;
        asoc->ss_data.last_out_stream = NULL;
        TAILQ_INIT(&asoc->ss_data.out.wheel);
        /*
         * If there is data in the stream queues already, the scheduler of
         * an existing association has been changed. We need to add all
         * stream queues to the wheel.
         */
        for (i = 0; i < asoc->streamoutcnt; i++) {
                stcb->asoc.ss_functions.sctp_ss_add_to_stream(stcb, asoc,
                    &asoc->strmout[i],
                    NULL);
        }
        return;
}
 
static void
sctp_ss_default_clear(struct sctp_tcb *stcb, struct sctp_association *asoc,
    bool clear_values SCTP_UNUSED)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        while (!TAILQ_EMPTY(&asoc->ss_data.out.wheel)) {
                struct sctp_stream_out *strq;
 
                strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                KASSERT(strq->ss_params.scheduled, ("strq %p not scheduled", (void *)strq));
                TAILQ_REMOVE(&asoc->ss_data.out.wheel, strq, ss_params.ss.rr.next_spoke);
                strq->ss_params.scheduled = false;
        }
        asoc->ss_data.last_out_stream = NULL;
        return;
}
 
static void
sctp_ss_default_init_stream(struct sctp_tcb *stcb, struct sctp_stream_out *strq, struct sctp_stream_out *with_strq)
{
        if (with_strq != NULL) {
                if (stcb->asoc.ss_data.locked_on_sending == with_strq) {
                        stcb->asoc.ss_data.locked_on_sending = strq;
                }
                if (stcb->asoc.ss_data.last_out_stream == with_strq) {
                        stcb->asoc.ss_data.last_out_stream = strq;
                }
        }
        strq->ss_params.scheduled = false;
        return;
}
 
static void
sctp_ss_default_add(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq,
    struct sctp_stream_queue_pending *sp SCTP_UNUSED)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        /* Add to wheel if not already on it and stream queue not empty */
        if (!TAILQ_EMPTY(&strq->outqueue) && !strq->ss_params.scheduled) {
                TAILQ_INSERT_TAIL(&asoc->ss_data.out.wheel,
                    strq, ss_params.ss.rr.next_spoke);
                strq->ss_params.scheduled = true;
        }
        return;
}
 
static bool
sctp_ss_default_is_empty(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_association *asoc)
{
        return (TAILQ_EMPTY(&asoc->ss_data.out.wheel));
}
 
static void
sctp_ss_default_remove(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq,
    struct sctp_stream_queue_pending *sp SCTP_UNUSED)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        /*
         * Remove from wheel if stream queue is empty and actually is on the
         * wheel
         */
        if (TAILQ_EMPTY(&strq->outqueue) && strq->ss_params.scheduled) {
                if (asoc->ss_data.last_out_stream == strq) {
                        asoc->ss_data.last_out_stream = TAILQ_PREV(asoc->ss_data.last_out_stream,
                            sctpwheel_listhead,
                            ss_params.ss.rr.next_spoke);
                        if (asoc->ss_data.last_out_stream == NULL) {
                                asoc->ss_data.last_out_stream = TAILQ_LAST(&asoc->ss_data.out.wheel,
                                    sctpwheel_listhead);
                        }
                        if (asoc->ss_data.last_out_stream == strq) {
                                asoc->ss_data.last_out_stream = NULL;
                        }
                }
                if (asoc->ss_data.locked_on_sending == strq) {
                        asoc->ss_data.locked_on_sending = NULL;
                }
                TAILQ_REMOVE(&asoc->ss_data.out.wheel, strq, ss_params.ss.rr.next_spoke);
                strq->ss_params.scheduled = false;
        }
        return;
}
 
static struct sctp_stream_out *
sctp_ss_default_select(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_nets *net,
    struct sctp_association *asoc)
{
        struct sctp_stream_out *strq, *strqt;
 
        if (asoc->ss_data.locked_on_sending != NULL) {
                KASSERT(asoc->ss_data.locked_on_sending->ss_params.scheduled,
                    ("locked_on_sending %p not scheduled",
                    (void *)asoc->ss_data.locked_on_sending));
                return (asoc->ss_data.locked_on_sending);
        }
        strqt = asoc->ss_data.last_out_stream;
        KASSERT(strqt == NULL || strqt->ss_params.scheduled,
            ("last_out_stream %p not scheduled", (void *)strqt));
default_again:
        /* Find the next stream to use */
        if (strqt == NULL) {
                strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
        } else {
                strq = TAILQ_NEXT(strqt, ss_params.ss.rr.next_spoke);
                if (strq == NULL) {
                        strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                }
        }
        KASSERT(strq == NULL || strq->ss_params.scheduled,
            ("strq %p not scheduled", (void *)strq));
 
        /*
         * If CMT is off, we must validate that the stream in question has
         * the first item pointed towards are network destination requested
         * by the caller. Note that if we turn out to be locked to a stream
         * (assigning TSN's then we must stop, since we cannot look for
         * another stream with data to send to that destination). In CMT's
         * case, by skipping this check, we will send one data packet
         * towards the requested net.
         */
        if (net != NULL && strq != NULL &&
            SCTP_BASE_SYSCTL(sctp_cmt_on_off) == 0) {
                if (TAILQ_FIRST(&strq->outqueue) &&
                    TAILQ_FIRST(&strq->outqueue)->net != NULL &&
                    TAILQ_FIRST(&strq->outqueue)->net != net) {
                        if (strq == asoc->ss_data.last_out_stream) {
                                return (NULL);
                        } else {
                                strqt = strq;
                                goto default_again;
                        }
                }
        }
        return (strq);
}
 
static void
sctp_ss_default_scheduled(struct sctp_tcb *stcb,
    struct sctp_nets *net SCTP_UNUSED,
    struct sctp_association *asoc,
    struct sctp_stream_out *strq,
    int moved_how_much SCTP_UNUSED)
{
        struct sctp_stream_queue_pending *sp;
 
        KASSERT(strq != NULL, ("strq is NULL"));
        KASSERT(strq->ss_params.scheduled, ("strq %p is not scheduled", (void *)strq));
        asoc->ss_data.last_out_stream = strq;
        if (asoc->idata_supported == 0) {
                sp = TAILQ_FIRST(&strq->outqueue);
                if ((sp != NULL) && (sp->some_taken == 1)) {
                        asoc->ss_data.locked_on_sending = strq;
                } else {
                        asoc->ss_data.locked_on_sending = NULL;
                }
        } else {
                asoc->ss_data.locked_on_sending = NULL;
        }
        return;
}
 
static void
sctp_ss_default_packet_done(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_nets *net SCTP_UNUSED,
    struct sctp_association *asoc SCTP_UNUSED)
{
        /* Nothing to be done here */
        return;
}
 
static int
sctp_ss_default_get_value(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_association *asoc SCTP_UNUSED,
    struct sctp_stream_out *strq SCTP_UNUSED, uint16_t *value SCTP_UNUSED)
{
        /* Nothing to be done here */
        return (-1);
}
 
static int
sctp_ss_default_set_value(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_association *asoc SCTP_UNUSED,
    struct sctp_stream_out *strq SCTP_UNUSED, uint16_t value SCTP_UNUSED)
{
        /* Nothing to be done here */
        return (-1);
}
 
static bool
sctp_ss_default_is_user_msgs_incomplete(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_association *asoc)
{
        struct sctp_stream_out *strq;
        struct sctp_stream_queue_pending *sp;
 
        if (asoc->stream_queue_cnt != 1) {
                return (false);
        }
        strq = asoc->ss_data.locked_on_sending;
        if (strq == NULL) {
                return (false);
        }
        sp = TAILQ_FIRST(&strq->outqueue);
        if (sp == NULL) {
                return (false);
        }
        return (sp->msg_is_complete == 0);
}
 
/*
 * Real round-robin algorithm.
 * Always interates the streams in ascending order.
 */
static void
sctp_ss_rr_add(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq,
    struct sctp_stream_queue_pending *sp SCTP_UNUSED)
{
        struct sctp_stream_out *strqt;
 
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        if (!TAILQ_EMPTY(&strq->outqueue) && !strq->ss_params.scheduled) {
                if (TAILQ_EMPTY(&asoc->ss_data.out.wheel)) {
                        TAILQ_INSERT_HEAD(&asoc->ss_data.out.wheel, strq, ss_params.ss.rr.next_spoke);
                } else {
                        strqt = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                        while (strqt != NULL && (strqt->sid < strq->sid)) {
                                strqt = TAILQ_NEXT(strqt, ss_params.ss.rr.next_spoke);
                        }
                        if (strqt != NULL) {
                                TAILQ_INSERT_BEFORE(strqt, strq, ss_params.ss.rr.next_spoke);
                        } else {
                                TAILQ_INSERT_TAIL(&asoc->ss_data.out.wheel, strq, ss_params.ss.rr.next_spoke);
                        }
                }
                strq->ss_params.scheduled = true;
        }
        return;
}
 
/*
 * Real round-robin per packet algorithm.
 * Always interates the streams in ascending order and
 * only fills messages of the same stream in a packet.
 */
static struct sctp_stream_out *
sctp_ss_rrp_select(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_nets *net SCTP_UNUSED,
    struct sctp_association *asoc)
{
        return (asoc->ss_data.last_out_stream);
}
 
static void
sctp_ss_rrp_packet_done(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_nets *net,
    struct sctp_association *asoc)
{
        struct sctp_stream_out *strq, *strqt;
 
        strqt = asoc->ss_data.last_out_stream;
        KASSERT(strqt == NULL || strqt->ss_params.scheduled,
            ("last_out_stream %p not scheduled", (void *)strqt));
rrp_again:
        /* Find the next stream to use */
        if (strqt == NULL) {
                strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
        } else {
                strq = TAILQ_NEXT(strqt, ss_params.ss.rr.next_spoke);
                if (strq == NULL) {
                        strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                }
        }
        KASSERT(strq == NULL || strq->ss_params.scheduled,
            ("strq %p not scheduled", (void *)strq));
 
        /*
         * If CMT is off, we must validate that the stream in question has
         * the first item pointed towards are network destination requested
         * by the caller. Note that if we turn out to be locked to a stream
         * (assigning TSN's then we must stop, since we cannot look for
         * another stream with data to send to that destination). In CMT's
         * case, by skipping this check, we will send one data packet
         * towards the requested net.
         */
        if (net != NULL && strq != NULL &&
            SCTP_BASE_SYSCTL(sctp_cmt_on_off) == 0) {
                if (TAILQ_FIRST(&strq->outqueue) &&
                    TAILQ_FIRST(&strq->outqueue)->net != NULL &&
                    TAILQ_FIRST(&strq->outqueue)->net != net) {
                        if (strq == asoc->ss_data.last_out_stream) {
                                strq = NULL;
                        } else {
                                strqt = strq;
                                goto rrp_again;
                        }
                }
        }
        asoc->ss_data.last_out_stream = strq;
        return;
}
 
/*
 * Priority algorithm.
 * Always prefers streams based on their priority id.
 */
static void
sctp_ss_prio_clear(struct sctp_tcb *stcb, struct sctp_association *asoc,
    bool clear_values)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        while (!TAILQ_EMPTY(&asoc->ss_data.out.wheel)) {
                struct sctp_stream_out *strq;
 
                strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                KASSERT(strq->ss_params.scheduled, ("strq %p not scheduled", (void *)strq));
                if (clear_values) {
                        strq->ss_params.ss.prio.priority = 0;
                }
                TAILQ_REMOVE(&asoc->ss_data.out.wheel, strq, ss_params.ss.prio.next_spoke);
                strq->ss_params.scheduled = false;
        }
        asoc->ss_data.last_out_stream = NULL;
        return;
}
 
static void
sctp_ss_prio_init_stream(struct sctp_tcb *stcb, struct sctp_stream_out *strq, struct sctp_stream_out *with_strq)
{
        if (with_strq != NULL) {
                if (stcb->asoc.ss_data.locked_on_sending == with_strq) {
                        stcb->asoc.ss_data.locked_on_sending = strq;
                }
                if (stcb->asoc.ss_data.last_out_stream == with_strq) {
                        stcb->asoc.ss_data.last_out_stream = strq;
                }
        }
        strq->ss_params.scheduled = false;
        if (with_strq != NULL) {
                strq->ss_params.ss.prio.priority = with_strq->ss_params.ss.prio.priority;
        } else {
                strq->ss_params.ss.prio.priority = 0;
        }
        return;
}
 
static void
sctp_ss_prio_add(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq, struct sctp_stream_queue_pending *sp SCTP_UNUSED)
{
        struct sctp_stream_out *strqt;
 
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        /* Add to wheel if not already on it and stream queue not empty */
        if (!TAILQ_EMPTY(&strq->outqueue) && !strq->ss_params.scheduled) {
                if (TAILQ_EMPTY(&asoc->ss_data.out.wheel)) {
                        TAILQ_INSERT_HEAD(&asoc->ss_data.out.wheel, strq, ss_params.ss.prio.next_spoke);
                } else {
                        strqt = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                        while (strqt != NULL && strqt->ss_params.ss.prio.priority < strq->ss_params.ss.prio.priority) {
                                strqt = TAILQ_NEXT(strqt, ss_params.ss.prio.next_spoke);
                        }
                        if (strqt != NULL) {
                                TAILQ_INSERT_BEFORE(strqt, strq, ss_params.ss.prio.next_spoke);
                        } else {
                                TAILQ_INSERT_TAIL(&asoc->ss_data.out.wheel, strq, ss_params.ss.prio.next_spoke);
                        }
                }
                strq->ss_params.scheduled = true;
        }
        return;
}
 
static void
sctp_ss_prio_remove(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq, struct sctp_stream_queue_pending *sp SCTP_UNUSED)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        /*
         * Remove from wheel if stream queue is empty and actually is on the
         * wheel
         */
        if (TAILQ_EMPTY(&strq->outqueue) && strq->ss_params.scheduled) {
                if (asoc->ss_data.last_out_stream == strq) {
                        asoc->ss_data.last_out_stream = TAILQ_PREV(asoc->ss_data.last_out_stream,
                            sctpwheel_listhead,
                            ss_params.ss.prio.next_spoke);
                        if (asoc->ss_data.last_out_stream == NULL) {
                                asoc->ss_data.last_out_stream = TAILQ_LAST(&asoc->ss_data.out.wheel,
                                    sctpwheel_listhead);
                        }
                        if (asoc->ss_data.last_out_stream == strq) {
                                asoc->ss_data.last_out_stream = NULL;
                        }
                }
                if (asoc->ss_data.locked_on_sending == strq) {
                        asoc->ss_data.locked_on_sending = NULL;
                }
                TAILQ_REMOVE(&asoc->ss_data.out.wheel, strq, ss_params.ss.prio.next_spoke);
                strq->ss_params.scheduled = false;
        }
        return;
}
 
static struct sctp_stream_out *
sctp_ss_prio_select(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_nets *net,
    struct sctp_association *asoc)
{
        struct sctp_stream_out *strq, *strqt, *strqn;
 
        if (asoc->ss_data.locked_on_sending != NULL) {
                KASSERT(asoc->ss_data.locked_on_sending->ss_params.scheduled,
                    ("locked_on_sending %p not scheduled",
                    (void *)asoc->ss_data.locked_on_sending));
                return (asoc->ss_data.locked_on_sending);
        }
        strqt = asoc->ss_data.last_out_stream;
        KASSERT(strqt == NULL || strqt->ss_params.scheduled,
            ("last_out_stream %p not scheduled", (void *)strqt));
prio_again:
        /* Find the next stream to use */
        if (strqt == NULL) {
                strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
        } else {
                strqn = TAILQ_NEXT(strqt, ss_params.ss.prio.next_spoke);
                if (strqn != NULL &&
                    strqn->ss_params.ss.prio.priority == strqt->ss_params.ss.prio.priority) {
                        strq = strqn;
                } else {
                        strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                }
        }
        KASSERT(strq == NULL || strq->ss_params.scheduled,
            ("strq %p not scheduled", (void *)strq));
 
        /*
         * If CMT is off, we must validate that the stream in question has
         * the first item pointed towards are network destination requested
         * by the caller. Note that if we turn out to be locked to a stream
         * (assigning TSN's then we must stop, since we cannot look for
         * another stream with data to send to that destination). In CMT's
         * case, by skipping this check, we will send one data packet
         * towards the requested net.
         */
        if (net != NULL && strq != NULL &&
            SCTP_BASE_SYSCTL(sctp_cmt_on_off) == 0) {
                if (TAILQ_FIRST(&strq->outqueue) &&
                    TAILQ_FIRST(&strq->outqueue)->net != NULL &&
                    TAILQ_FIRST(&strq->outqueue)->net != net) {
                        if (strq == asoc->ss_data.last_out_stream) {
                                return (NULL);
                        } else {
                                strqt = strq;
                                goto prio_again;
                        }
                }
        }
        return (strq);
}
 
static int
sctp_ss_prio_get_value(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_association *asoc SCTP_UNUSED,
    struct sctp_stream_out *strq, uint16_t *value)
{
        if (strq == NULL) {
                return (-1);
        }
        *value = strq->ss_params.ss.prio.priority;
        return (1);
}
 
static int
sctp_ss_prio_set_value(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq, uint16_t value)
{
        if (strq == NULL) {
                return (-1);
        }
        strq->ss_params.ss.prio.priority = value;
        sctp_ss_prio_remove(stcb, asoc, strq, NULL);
        sctp_ss_prio_add(stcb, asoc, strq, NULL);
        return (1);
}
 
/*
 * Fair bandwidth algorithm.
 * Maintains an equal throughput per stream.
 */
static void
sctp_ss_fb_clear(struct sctp_tcb *stcb, struct sctp_association *asoc,
    bool clear_values)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        while (!TAILQ_EMPTY(&asoc->ss_data.out.wheel)) {
                struct sctp_stream_out *strq;
 
                strq = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                KASSERT(strq->ss_params.scheduled, ("strq %p not scheduled", (void *)strq));
                if (clear_values) {
                        strq->ss_params.ss.fb.rounds = -1;
                }
                TAILQ_REMOVE(&asoc->ss_data.out.wheel, strq, ss_params.ss.fb.next_spoke);
                strq->ss_params.scheduled = false;
        }
        asoc->ss_data.last_out_stream = NULL;
        return;
}
 
static void
sctp_ss_fb_init_stream(struct sctp_tcb *stcb, struct sctp_stream_out *strq, struct sctp_stream_out *with_strq)
{
        if (with_strq != NULL) {
                if (stcb->asoc.ss_data.locked_on_sending == with_strq) {
                        stcb->asoc.ss_data.locked_on_sending = strq;
                }
                if (stcb->asoc.ss_data.last_out_stream == with_strq) {
                        stcb->asoc.ss_data.last_out_stream = strq;
                }
        }
        strq->ss_params.scheduled = false;
        if (with_strq != NULL) {
                strq->ss_params.ss.fb.rounds = with_strq->ss_params.ss.fb.rounds;
        } else {
                strq->ss_params.ss.fb.rounds = -1;
        }
        return;
}
 
static void
sctp_ss_fb_add(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq, struct sctp_stream_queue_pending *sp SCTP_UNUSED)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        if (!TAILQ_EMPTY(&strq->outqueue) && !strq->ss_params.scheduled) {
                if (strq->ss_params.ss.fb.rounds < 0)
                        strq->ss_params.ss.fb.rounds = TAILQ_FIRST(&strq->outqueue)->length;
                TAILQ_INSERT_TAIL(&asoc->ss_data.out.wheel, strq, ss_params.ss.fb.next_spoke);
                strq->ss_params.scheduled = true;
        }
        return;
}
 
static void
sctp_ss_fb_remove(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq, struct sctp_stream_queue_pending *sp SCTP_UNUSED)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        /*
         * Remove from wheel if stream queue is empty and actually is on the
         * wheel
         */
        if (TAILQ_EMPTY(&strq->outqueue) && strq->ss_params.scheduled) {
                if (asoc->ss_data.last_out_stream == strq) {
                        asoc->ss_data.last_out_stream = TAILQ_PREV(asoc->ss_data.last_out_stream,
                            sctpwheel_listhead,
                            ss_params.ss.fb.next_spoke);
                        if (asoc->ss_data.last_out_stream == NULL) {
                                asoc->ss_data.last_out_stream = TAILQ_LAST(&asoc->ss_data.out.wheel,
                                    sctpwheel_listhead);
                        }
                        if (asoc->ss_data.last_out_stream == strq) {
                                asoc->ss_data.last_out_stream = NULL;
                        }
                }
                if (asoc->ss_data.locked_on_sending == strq) {
                        asoc->ss_data.locked_on_sending = NULL;
                }
                TAILQ_REMOVE(&asoc->ss_data.out.wheel, strq, ss_params.ss.fb.next_spoke);
                strq->ss_params.scheduled = false;
        }
        return;
}
 
static struct sctp_stream_out *
sctp_ss_fb_select(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_nets *net,
    struct sctp_association *asoc)
{
        struct sctp_stream_out *strq = NULL, *strqt;
 
        if (asoc->ss_data.locked_on_sending != NULL) {
                KASSERT(asoc->ss_data.locked_on_sending->ss_params.scheduled,
                    ("locked_on_sending %p not scheduled",
                    (void *)asoc->ss_data.locked_on_sending));
                return (asoc->ss_data.locked_on_sending);
        }
        if (asoc->ss_data.last_out_stream == NULL ||
            TAILQ_FIRST(&asoc->ss_data.out.wheel) == TAILQ_LAST(&asoc->ss_data.out.wheel, sctpwheel_listhead)) {
                strqt = TAILQ_FIRST(&asoc->ss_data.out.wheel);
        } else {
                strqt = TAILQ_NEXT(asoc->ss_data.last_out_stream, ss_params.ss.fb.next_spoke);
        }
        do {
                if ((strqt != NULL) &&
                    ((SCTP_BASE_SYSCTL(sctp_cmt_on_off) > 0) ||
                    (SCTP_BASE_SYSCTL(sctp_cmt_on_off) == 0 &&
                    (net == NULL || (TAILQ_FIRST(&strqt->outqueue) && TAILQ_FIRST(&strqt->outqueue)->net == NULL) ||
                    (net != NULL && TAILQ_FIRST(&strqt->outqueue) && TAILQ_FIRST(&strqt->outqueue)->net != NULL &&
                    TAILQ_FIRST(&strqt->outqueue)->net == net))))) {
                        if ((strqt->ss_params.ss.fb.rounds >= 0) &&
                            ((strq == NULL) ||
                            (strqt->ss_params.ss.fb.rounds < strq->ss_params.ss.fb.rounds))) {
                                strq = strqt;
                        }
                }
                if (strqt != NULL) {
                        strqt = TAILQ_NEXT(strqt, ss_params.ss.fb.next_spoke);
                } else {
                        strqt = TAILQ_FIRST(&asoc->ss_data.out.wheel);
                }
        } while (strqt != strq);
        return (strq);
}
 
static void
sctp_ss_fb_scheduled(struct sctp_tcb *stcb, struct sctp_nets *net SCTP_UNUSED,
    struct sctp_association *asoc, struct sctp_stream_out *strq,
    int moved_how_much SCTP_UNUSED)
{
        struct sctp_stream_queue_pending *sp;
        struct sctp_stream_out *strqt;
        int subtract;
 
        if (asoc->idata_supported == 0) {
                sp = TAILQ_FIRST(&strq->outqueue);
                if ((sp != NULL) && (sp->some_taken == 1)) {
                        asoc->ss_data.locked_on_sending = strq;
                } else {
                        asoc->ss_data.locked_on_sending = NULL;
                }
        } else {
                asoc->ss_data.locked_on_sending = NULL;
        }
        subtract = strq->ss_params.ss.fb.rounds;
        TAILQ_FOREACH(strqt, &asoc->ss_data.out.wheel, ss_params.ss.fb.next_spoke) {
                strqt->ss_params.ss.fb.rounds -= subtract;
                if (strqt->ss_params.ss.fb.rounds < 0)
                        strqt->ss_params.ss.fb.rounds = 0;
        }
        if (TAILQ_FIRST(&strq->outqueue)) {
                strq->ss_params.ss.fb.rounds = TAILQ_FIRST(&strq->outqueue)->length;
        } else {
                strq->ss_params.ss.fb.rounds = -1;
        }
        asoc->ss_data.last_out_stream = strq;
        return;
}
 
/*
 * First-come, first-serve algorithm.
 * Maintains the order provided by the application.
 */
static void
sctp_ss_fcfs_add(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq SCTP_UNUSED,
    struct sctp_stream_queue_pending *sp);
 
static void
sctp_ss_fcfs_init(struct sctp_tcb *stcb, struct sctp_association *asoc)
{
        uint32_t x, n = 0, add_more = 1;
        struct sctp_stream_queue_pending *sp;
        uint16_t i;
 
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        TAILQ_INIT(&asoc->ss_data.out.list);
        /*
         * If there is data in the stream queues already, the scheduler of
         * an existing association has been changed. We can only cycle
         * through the stream queues and add everything to the FCFS queue.
         */
        while (add_more) {
                add_more = 0;
                for (i = 0; i < asoc->streamoutcnt; i++) {
                        sp = TAILQ_FIRST(&asoc->strmout[i].outqueue);
                        x = 0;
                        /* Find n. message in current stream queue */
                        while (sp != NULL && x < n) {
                                sp = TAILQ_NEXT(sp, next);
                                x++;
                        }
                        if (sp != NULL) {
                                sctp_ss_fcfs_add(stcb, asoc, &asoc->strmout[i], sp);
                                add_more = 1;
                        }
                }
                n++;
        }
        return;
}
 
static void
sctp_ss_fcfs_clear(struct sctp_tcb *stcb, struct sctp_association *asoc,
    bool clear_values SCTP_UNUSED)
{
        struct sctp_stream_queue_pending *sp;
 
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        while (!TAILQ_EMPTY(&asoc->ss_data.out.list)) {
                sp = TAILQ_FIRST(&asoc->ss_data.out.list);
                KASSERT(sp->scheduled, ("sp %p not scheduled", (void *)sp));
                TAILQ_REMOVE(&asoc->ss_data.out.list, sp, ss_next);
                sp->scheduled = false;
        }
        asoc->ss_data.last_out_stream = NULL;
        return;
}
 
static void
sctp_ss_fcfs_init_stream(struct sctp_tcb *stcb, struct sctp_stream_out *strq, struct sctp_stream_out *with_strq)
{
        if (with_strq != NULL) {
                if (stcb->asoc.ss_data.locked_on_sending == with_strq) {
                        stcb->asoc.ss_data.locked_on_sending = strq;
                }
                if (stcb->asoc.ss_data.last_out_stream == with_strq) {
                        stcb->asoc.ss_data.last_out_stream = strq;
                }
        }
        strq->ss_params.scheduled = false;
        return;
}
 
static void
sctp_ss_fcfs_add(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq SCTP_UNUSED, struct sctp_stream_queue_pending *sp)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        if (!sp->scheduled) {
                TAILQ_INSERT_TAIL(&asoc->ss_data.out.list, sp, ss_next);
                sp->scheduled = true;
        }
        return;
}
 
static bool
sctp_ss_fcfs_is_empty(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_association *asoc)
{
        return (TAILQ_EMPTY(&asoc->ss_data.out.list));
}
 
static void
sctp_ss_fcfs_remove(struct sctp_tcb *stcb, struct sctp_association *asoc,
    struct sctp_stream_out *strq SCTP_UNUSED, struct sctp_stream_queue_pending *sp)
{
        SCTP_TCB_SEND_LOCK_ASSERT(stcb);
 
        if (sp->scheduled) {
                TAILQ_REMOVE(&asoc->ss_data.out.list, sp, ss_next);
                sp->scheduled = false;
        }
        return;
}
 
static struct sctp_stream_out *
sctp_ss_fcfs_select(struct sctp_tcb *stcb SCTP_UNUSED, struct sctp_nets *net,
    struct sctp_association *asoc)
{
        struct sctp_stream_out *strq;
        struct sctp_stream_queue_pending *sp;
 
        if (asoc->ss_data.locked_on_sending) {
                return (asoc->ss_data.locked_on_sending);
        }
        sp = TAILQ_FIRST(&asoc->ss_data.out.list);
default_again:
        if (sp != NULL) {
                strq = &asoc->strmout[sp->sid];
        } else {
                strq = NULL;
        }
 
        /*
         * If CMT is off, we must validate that the stream in question has
         * the first item pointed towards are network destination requested
         * by the caller. Note that if we turn out to be locked to a stream
         * (assigning TSN's then we must stop, since we cannot look for
         * another stream with data to send to that destination). In CMT's
         * case, by skipping this check, we will send one data packet
         * towards the requested net.
         */
        if (net != NULL && strq != NULL &&
            SCTP_BASE_SYSCTL(sctp_cmt_on_off) == 0) {
                if (TAILQ_FIRST(&strq->outqueue) &&
                    TAILQ_FIRST(&strq->outqueue)->net != NULL &&
                    TAILQ_FIRST(&strq->outqueue)->net != net) {
                        sp = TAILQ_NEXT(sp, ss_next);
                        goto default_again;
                }
        }
        return (strq);
}
 
static void
sctp_ss_fcfs_scheduled(struct sctp_tcb *stcb,
    struct sctp_nets *net SCTP_UNUSED,
    struct sctp_association *asoc,
    struct sctp_stream_out *strq,
    int moved_how_much SCTP_UNUSED)
{
        struct sctp_stream_queue_pending *sp;
 
        KASSERT(strq != NULL, ("strq is NULL"));
        asoc->ss_data.last_out_stream = strq;
        if (asoc->idata_supported == 0) {
                sp = TAILQ_FIRST(&strq->outqueue);
                if ((sp != NULL) && (sp->some_taken == 1)) {
                        asoc->ss_data.locked_on_sending = strq;
                } else {
                        asoc->ss_data.locked_on_sending = NULL;
                }
        } else {
                asoc->ss_data.locked_on_sending = NULL;
        }
        return;
}
 
const struct sctp_ss_functions sctp_ss_functions[] = {
/* SCTP_SS_DEFAULT */
        {
                .sctp_ss_init = sctp_ss_default_init,
                .sctp_ss_clear = sctp_ss_default_clear,
                .sctp_ss_init_stream = sctp_ss_default_init_stream,
                .sctp_ss_add_to_stream = sctp_ss_default_add,
                .sctp_ss_is_empty = sctp_ss_default_is_empty,
                .sctp_ss_remove_from_stream = sctp_ss_default_remove,
                .sctp_ss_select_stream = sctp_ss_default_select,
                .sctp_ss_scheduled = sctp_ss_default_scheduled,
                .sctp_ss_packet_done = sctp_ss_default_packet_done,
                .sctp_ss_get_value = sctp_ss_default_get_value,
                .sctp_ss_set_value = sctp_ss_default_set_value,
                .sctp_ss_is_user_msgs_incomplete = sctp_ss_default_is_user_msgs_incomplete
        },
/* SCTP_SS_ROUND_ROBIN */
        {
                .sctp_ss_init = sctp_ss_default_init,
                .sctp_ss_clear = sctp_ss_default_clear,
                .sctp_ss_init_stream = sctp_ss_default_init_stream,
                .sctp_ss_add_to_stream = sctp_ss_rr_add,
                .sctp_ss_is_empty = sctp_ss_default_is_empty,
                .sctp_ss_remove_from_stream = sctp_ss_default_remove,
                .sctp_ss_select_stream = sctp_ss_default_select,
                .sctp_ss_scheduled = sctp_ss_default_scheduled,
                .sctp_ss_packet_done = sctp_ss_default_packet_done,
                .sctp_ss_get_value = sctp_ss_default_get_value,
                .sctp_ss_set_value = sctp_ss_default_set_value,
                .sctp_ss_is_user_msgs_incomplete = sctp_ss_default_is_user_msgs_incomplete
        },
/* SCTP_SS_ROUND_ROBIN_PACKET */
        {
                .sctp_ss_init = sctp_ss_default_init,
                .sctp_ss_clear = sctp_ss_default_clear,
                .sctp_ss_init_stream = sctp_ss_default_init_stream,
                .sctp_ss_add_to_stream = sctp_ss_rr_add,
                .sctp_ss_is_empty = sctp_ss_default_is_empty,
                .sctp_ss_remove_from_stream = sctp_ss_default_remove,
                .sctp_ss_select_stream = sctp_ss_rrp_select,
                .sctp_ss_scheduled = sctp_ss_default_scheduled,
                .sctp_ss_packet_done = sctp_ss_rrp_packet_done,
                .sctp_ss_get_value = sctp_ss_default_get_value,
                .sctp_ss_set_value = sctp_ss_default_set_value,
                .sctp_ss_is_user_msgs_incomplete = sctp_ss_default_is_user_msgs_incomplete
        },
/* SCTP_SS_PRIORITY */
        {
                .sctp_ss_init = sctp_ss_default_init,
                .sctp_ss_clear = sctp_ss_prio_clear,
                .sctp_ss_init_stream = sctp_ss_prio_init_stream,
                .sctp_ss_add_to_stream = sctp_ss_prio_add,
                .sctp_ss_is_empty = sctp_ss_default_is_empty,
                .sctp_ss_remove_from_stream = sctp_ss_prio_remove,
                .sctp_ss_select_stream = sctp_ss_prio_select,
                .sctp_ss_scheduled = sctp_ss_default_scheduled,
                .sctp_ss_packet_done = sctp_ss_default_packet_done,
                .sctp_ss_get_value = sctp_ss_prio_get_value,
                .sctp_ss_set_value = sctp_ss_prio_set_value,
                .sctp_ss_is_user_msgs_incomplete = sctp_ss_default_is_user_msgs_incomplete
        },
/* SCTP_SS_FAIR_BANDWITH */
        {
                .sctp_ss_init = sctp_ss_default_init,
                .sctp_ss_clear = sctp_ss_fb_clear,
                .sctp_ss_init_stream = sctp_ss_fb_init_stream,
                .sctp_ss_add_to_stream = sctp_ss_fb_add,
                .sctp_ss_is_empty = sctp_ss_default_is_empty,
                .sctp_ss_remove_from_stream = sctp_ss_fb_remove,
                .sctp_ss_select_stream = sctp_ss_fb_select,
                .sctp_ss_scheduled = sctp_ss_fb_scheduled,
                .sctp_ss_packet_done = sctp_ss_default_packet_done,
                .sctp_ss_get_value = sctp_ss_default_get_value,
                .sctp_ss_set_value = sctp_ss_default_set_value,
                .sctp_ss_is_user_msgs_incomplete = sctp_ss_default_is_user_msgs_incomplete
        },
/* SCTP_SS_FIRST_COME */
        {
                .sctp_ss_init = sctp_ss_fcfs_init,
                .sctp_ss_clear = sctp_ss_fcfs_clear,
                .sctp_ss_init_stream = sctp_ss_fcfs_init_stream,
                .sctp_ss_add_to_stream = sctp_ss_fcfs_add,
                .sctp_ss_is_empty = sctp_ss_fcfs_is_empty,
                .sctp_ss_remove_from_stream = sctp_ss_fcfs_remove,
                .sctp_ss_select_stream = sctp_ss_fcfs_select,
                .sctp_ss_scheduled = sctp_ss_fcfs_scheduled,
                .sctp_ss_packet_done = sctp_ss_default_packet_done,
                .sctp_ss_get_value = sctp_ss_default_get_value,
                .sctp_ss_set_value = sctp_ss_default_set_value,
                .sctp_ss_is_user_msgs_incomplete = sctp_ss_default_is_user_msgs_incomplete
        }
};