// SPDX-License-Identifier: GPL-2.0-or-later
/* SCTP kernel implementation
 * (C) Copyright Red Hat Inc. 2017
 *
 * This file is part of the SCTP kernel implementation
 *
 * These functions manipulate sctp stream queue/scheduling.
 *
 * Please send any bug reports or fixes you make to the
 * email addresched(es):
 *    lksctp developers <linux-sctp@vger.kernel.org>
 *
 * Written or modified by:
 *    Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
 */

#include <linux/list.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>
#include <net/sctp/stream_sched.h>

/* First Come First Serve (a.k.a. FIFO)
 * RFC DRAFT ndata Section 3.1
 */
static int sctp_sched_fcfs_set(struct sctp_stream *stream, __u16 sid,
                               __u16 value, gfp_t gfp)
{
        return 0;
}

static int sctp_sched_fcfs_get(struct sctp_stream *stream, __u16 sid,
                               __u16 *value)
{
        *value = 0;
        return 0;
}

static int sctp_sched_fcfs_init(struct sctp_stream *stream)
{
        return 0;
}

static int sctp_sched_fcfs_init_sid(struct sctp_stream *stream, __u16 sid,
                                    gfp_t gfp)
{
        return 0;
}

static void sctp_sched_fcfs_free_sid(struct sctp_stream *stream, __u16 sid)
{
}

static void sctp_sched_fcfs_enqueue(struct sctp_outq *q,
                                    struct sctp_datamsg *msg)
{
}

static struct sctp_chunk *sctp_sched_fcfs_dequeue(struct sctp_outq *q)
{
        struct sctp_stream *stream = &q->asoc->stream;
        struct sctp_chunk *ch = NULL;
        struct list_head *entry;

        if (list_empty(&q->out_chunk_list))
                goto out;

        if (stream->out_curr) {
                ch = list_entry(stream->out_curr->ext->outq.next,
                                struct sctp_chunk, stream_list);
        } else {
                entry = q->out_chunk_list.next;
                ch = list_entry(entry, struct sctp_chunk, list);
        }

        sctp_sched_dequeue_common(q, ch);

out:
        return ch;
}

static void sctp_sched_fcfs_dequeue_done(struct sctp_outq *q,
                                         struct sctp_chunk *chunk)
{
}

static void sctp_sched_fcfs_sched_all(struct sctp_stream *stream)
{
}

static void sctp_sched_fcfs_unsched_all(struct sctp_stream *stream)
{
}

static const struct sctp_sched_ops sctp_sched_fcfs = {
        .set = sctp_sched_fcfs_set,
        .get = sctp_sched_fcfs_get,
        .init = sctp_sched_fcfs_init,
        .init_sid = sctp_sched_fcfs_init_sid,
        .free_sid = sctp_sched_fcfs_free_sid,
        .enqueue = sctp_sched_fcfs_enqueue,
        .dequeue = sctp_sched_fcfs_dequeue,
        .dequeue_done = sctp_sched_fcfs_dequeue_done,
        .sched_all = sctp_sched_fcfs_sched_all,
        .unsched_all = sctp_sched_fcfs_unsched_all,
};

static void sctp_sched_ops_fcfs_init(void)
{
        sctp_sched_ops_register(SCTP_SS_FCFS, &sctp_sched_fcfs);
}

/* API to other parts of the stack */

static const struct sctp_sched_ops *sctp_sched_ops[SCTP_SS_MAX + 1];

void sctp_sched_ops_register(enum sctp_sched_type sched,
                             const struct sctp_sched_ops *sched_ops)
{
        sctp_sched_ops[sched] = sched_ops;
}

void sctp_sched_ops_init(void)
{
        sctp_sched_ops_fcfs_init();
        sctp_sched_ops_prio_init();
        sctp_sched_ops_rr_init();
        sctp_sched_ops_fc_init();
        sctp_sched_ops_wfq_init();
}

static void sctp_sched_free_sched(struct sctp_stream *stream)
{
        const struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
        struct sctp_stream_out_ext *soute;
        int i;

        sched->unsched_all(stream);
        for (i = 0; i < stream->outcnt; i++) {
                soute = SCTP_SO(stream, i)->ext;
                if (!soute)
                        continue;
                sched->free_sid(stream, i);
                /* Give the next scheduler a clean slate. */
                memset_after(soute, 0, outq);
        }
}

int sctp_sched_set_sched(struct sctp_association *asoc,
                         enum sctp_sched_type sched)
{
        const struct sctp_sched_ops *old = asoc->outqueue.sched;
        struct sctp_datamsg *msg = NULL;
        const struct sctp_sched_ops *n;
        struct sctp_chunk *ch;
        int i, ret = 0;

        if (sched > SCTP_SS_MAX)
                return -EINVAL;

        n = sctp_sched_ops[sched];
        if (old == n)
                return ret;

        if (old)
                sctp_sched_free_sched(&asoc->stream);

        asoc->outqueue.sched = n;
        n->init(&asoc->stream);
        for (i = 0; i < asoc->stream.outcnt; i++) {
                if (!SCTP_SO(&asoc->stream, i)->ext)
                        continue;

                ret = n->init_sid(&asoc->stream, i, GFP_ATOMIC);
                if (ret)
                        goto err;
        }

        /* We have to requeue all chunks already queued. */
        list_for_each_entry(ch, &asoc->outqueue.out_chunk_list, list) {
                if (ch->msg == msg)
                        continue;
                msg = ch->msg;
                n->enqueue(&asoc->outqueue, msg);
        }

        return ret;

err:
        sctp_sched_free_sched(&asoc->stream);
        asoc->outqueue.sched = &sctp_sched_fcfs; /* Always safe */

        return ret;
}

int sctp_sched_get_sched(struct sctp_association *asoc)
{
        int i;

        for (i = 0; i <= SCTP_SS_MAX; i++)
                if (asoc->outqueue.sched == sctp_sched_ops[i])
                        return i;

        return 0;
}

int sctp_sched_set_value(struct sctp_association *asoc, __u16 sid,
                         __u16 value, gfp_t gfp)
{
        if (sid >= asoc->stream.outcnt)
                return -EINVAL;

        if (!SCTP_SO(&asoc->stream, sid)->ext) {
                int ret;

                ret = sctp_stream_init_ext(&asoc->stream, sid);
                if (ret)
                        return ret;
        }

        return asoc->outqueue.sched->set(&asoc->stream, sid, value, gfp);
}

int sctp_sched_get_value(struct sctp_association *asoc, __u16 sid,
                         __u16 *value)
{
        if (sid >= asoc->stream.outcnt)
                return -EINVAL;

        if (!SCTP_SO(&asoc->stream, sid)->ext)
                return 0;

        return asoc->outqueue.sched->get(&asoc->stream, sid, value);
}

void sctp_sched_dequeue_done(struct sctp_outq *q, struct sctp_chunk *ch)
{
        if (!list_is_last(&ch->frag_list, &ch->msg->chunks) &&
            !q->asoc->peer.intl_capable) {
                struct sctp_stream_out *sout;
                __u16 sid;

                /* datamsg is not finish, so save it as current one,
                 * in case application switch scheduler or a higher
                 * priority stream comes in.
                 */
                sid = sctp_chunk_stream_no(ch);
                sout = SCTP_SO(&q->asoc->stream, sid);
                q->asoc->stream.out_curr = sout;
                return;
        }

        q->asoc->stream.out_curr = NULL;
        q->sched->dequeue_done(q, ch);
}

/* Auxiliary functions for the schedulers */
void sctp_sched_dequeue_common(struct sctp_outq *q, struct sctp_chunk *ch)
{
        list_del_init(&ch->list);
        list_del_init(&ch->stream_list);
        q->out_qlen -= ch->skb->len;
}

int sctp_sched_init_sid(struct sctp_stream *stream, __u16 sid, gfp_t gfp)
{
        const struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
        struct sctp_stream_out_ext *ext = SCTP_SO(stream, sid)->ext;

        INIT_LIST_HEAD(&ext->outq);
        return sched->init_sid(stream, sid, gfp);
}

const struct sctp_sched_ops *sctp_sched_ops_from_stream(struct sctp_stream *stream)
{
        struct sctp_association *asoc;

        asoc = container_of(stream, struct sctp_association, stream);

        return asoc->outqueue.sched;
}