// 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>

/* Priority handling
 * RFC DRAFT ndata section 3.2
 */
static void sctp_sched_rr_unsched_all(struct sctp_stream *stream);

static void sctp_sched_rr_next_stream(struct sctp_stream *stream)
{
        struct list_head *pos;

        pos = stream->rr_next->rr_list.next;
        if (pos == &stream->rr_list)
                pos = pos->next;
        stream->rr_next = list_entry(pos, struct sctp_stream_out_ext, rr_list);
}

static void sctp_sched_rr_unsched(struct sctp_stream *stream,
                                  struct sctp_stream_out_ext *soute)
{
        if (stream->rr_next == soute)
                /* Try to move to the next stream */
                sctp_sched_rr_next_stream(stream);

        list_del_init(&soute->rr_list);

        /* If we have no other stream queued, clear next */
        if (list_empty(&stream->rr_list))
                stream->rr_next = NULL;
}

static void sctp_sched_rr_sched(struct sctp_stream *stream,
                                struct sctp_stream_out_ext *soute)
{
        if (!list_empty(&soute->rr_list))
                /* Already scheduled. */
                return;

        /* Schedule the stream */
        list_add_tail(&soute->rr_list, &stream->rr_list);

        if (!stream->rr_next)
                stream->rr_next = soute;
}

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

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

static int sctp_sched_rr_init(struct sctp_stream *stream)
{
        INIT_LIST_HEAD(&stream->rr_list);
        stream->rr_next = NULL;

        return 0;
}

static int sctp_sched_rr_init_sid(struct sctp_stream *stream, __u16 sid,
                                  gfp_t gfp)
{
        INIT_LIST_HEAD(&SCTP_SO(stream, sid)->ext->rr_list);

        return 0;
}

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

static void sctp_sched_rr_enqueue(struct sctp_outq *q,
                                  struct sctp_datamsg *msg)
{
        struct sctp_stream *stream;
        struct sctp_chunk *ch;
        __u16 sid;

        ch = list_first_entry(&msg->chunks, struct sctp_chunk, frag_list);
        sid = sctp_chunk_stream_no(ch);
        stream = &q->asoc->stream;
        sctp_sched_rr_sched(stream, SCTP_SO(stream, sid)->ext);
}

static struct sctp_chunk *sctp_sched_rr_dequeue(struct sctp_outq *q)
{
        struct sctp_stream *stream = &q->asoc->stream;
        struct sctp_stream_out_ext *soute;
        struct sctp_chunk *ch = NULL;

        /* Bail out quickly if queue is empty */
        if (list_empty(&q->out_chunk_list))
                goto out;

        /* Find which chunk is next */
        if (stream->out_curr)
                soute = stream->out_curr->ext;
        else
                soute = stream->rr_next;
        ch = list_entry(soute->outq.next, struct sctp_chunk, stream_list);

        sctp_sched_dequeue_common(q, ch);

out:
        return ch;
}

static void sctp_sched_rr_dequeue_done(struct sctp_outq *q,
                                       struct sctp_chunk *ch)
{
        struct sctp_stream_out_ext *soute;
        __u16 sid;

        /* Last chunk on that msg, move to the next stream */
        sid = sctp_chunk_stream_no(ch);
        soute = SCTP_SO(&q->asoc->stream, sid)->ext;

        sctp_sched_rr_next_stream(&q->asoc->stream);

        if (list_empty(&soute->outq))
                sctp_sched_rr_unsched(&q->asoc->stream, soute);
}

static void sctp_sched_rr_sched_all(struct sctp_stream *stream)
{
        struct sctp_association *asoc;
        struct sctp_stream_out_ext *soute;
        struct sctp_chunk *ch;

        asoc = container_of(stream, struct sctp_association, stream);
        list_for_each_entry(ch, &asoc->outqueue.out_chunk_list, list) {
                __u16 sid;

                sid = sctp_chunk_stream_no(ch);
                soute = SCTP_SO(stream, sid)->ext;
                if (soute)
                        sctp_sched_rr_sched(stream, soute);
        }
}

static void sctp_sched_rr_unsched_all(struct sctp_stream *stream)
{
        struct sctp_stream_out_ext *soute, *tmp;

        list_for_each_entry_safe(soute, tmp, &stream->rr_list, rr_list)
                sctp_sched_rr_unsched(stream, soute);
}

static const struct sctp_sched_ops sctp_sched_rr = {
        .set = sctp_sched_rr_set,
        .get = sctp_sched_rr_get,
        .init = sctp_sched_rr_init,
        .init_sid = sctp_sched_rr_init_sid,
        .free_sid = sctp_sched_rr_free_sid,
        .enqueue = sctp_sched_rr_enqueue,
        .dequeue = sctp_sched_rr_dequeue,
        .dequeue_done = sctp_sched_rr_dequeue_done,
        .sched_all = sctp_sched_rr_sched_all,
        .unsched_all = sctp_sched_rr_unsched_all,
};

void sctp_sched_ops_rr_init(void)
{
        sctp_sched_ops_register(SCTP_SS_RR, &sctp_sched_rr);
}