// SPDX-License-Identifier: GPL-2.0-or-later
/* SCTP kernel implementation
 * (C) Copyright Red Hat Inc. 2022
 *
 * 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:
 *    Xin Long <lucien.xin@gmail.com>
 */

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

/* Fair Capacity and Weighted Fair Queueing handling
 * RFC 8260 section 3.5 and 3.6
 */
static void sctp_sched_fc_unsched_all(struct sctp_stream *stream);

static int sctp_sched_wfq_set(struct sctp_stream *stream, __u16 sid,
                              __u16 weight, gfp_t gfp)
{
        struct sctp_stream_out_ext *soute = SCTP_SO(stream, sid)->ext;

        if (!weight)
                return -EINVAL;

        soute->fc_weight = weight;
        return 0;
}

static int sctp_sched_wfq_get(struct sctp_stream *stream, __u16 sid,
                              __u16 *value)
{
        struct sctp_stream_out_ext *soute = SCTP_SO(stream, sid)->ext;

        *value = soute->fc_weight;
        return 0;
}

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

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

static int sctp_sched_fc_init(struct sctp_stream *stream)
{
        INIT_LIST_HEAD(&stream->fc_list);

        return 0;
}

static int sctp_sched_fc_init_sid(struct sctp_stream *stream, __u16 sid,
                                  gfp_t gfp)
{
        struct sctp_stream_out_ext *soute = SCTP_SO(stream, sid)->ext;

        INIT_LIST_HEAD(&soute->fc_list);
        soute->fc_length = 0;
        soute->fc_weight = 1;

        return 0;
}

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

static void sctp_sched_fc_sched(struct sctp_stream *stream,
                                struct sctp_stream_out_ext *soute)
{
        struct sctp_stream_out_ext *pos;

        if (!list_empty(&soute->fc_list))
                return;

        list_for_each_entry(pos, &stream->fc_list, fc_list)
                if ((__u64)pos->fc_length * soute->fc_weight >=
                    (__u64)soute->fc_length * pos->fc_weight)
                        break;
        list_add_tail(&soute->fc_list, &pos->fc_list);
}

static void sctp_sched_fc_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_fc_sched(stream, SCTP_SO(stream, sid)->ext);
}

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

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

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

        sctp_sched_dequeue_common(q, ch);
        return ch;
}

static void sctp_sched_fc_dequeue_done(struct sctp_outq *q,
                                       struct sctp_chunk *ch)
{
        struct sctp_stream *stream = &q->asoc->stream;
        struct sctp_stream_out_ext *soute, *pos;
        __u16 sid, i;

        sid = sctp_chunk_stream_no(ch);
        soute = SCTP_SO(stream, sid)->ext;
        /* reduce all fc_lengths by U32_MAX / 4 if the current fc_length overflows. */
        if (soute->fc_length > U32_MAX - ch->skb->len) {
                for (i = 0; i < stream->outcnt; i++) {
                        pos = SCTP_SO(stream, i)->ext;
                        if (!pos)
                                continue;
                        if (pos->fc_length <= (U32_MAX >> 2)) {
                                pos->fc_length = 0;
                                continue;
                        }
                        pos->fc_length -= (U32_MAX >> 2);
                }
        }
        soute->fc_length += ch->skb->len;

        if (list_empty(&soute->outq)) {
                list_del_init(&soute->fc_list);
                return;
        }

        pos = soute;
        list_for_each_entry_continue(pos, &stream->fc_list, fc_list)
                if ((__u64)pos->fc_length * soute->fc_weight >=
                    (__u64)soute->fc_length * pos->fc_weight)
                        break;
        list_move_tail(&soute->fc_list, &pos->fc_list);
}

static void sctp_sched_fc_sched_all(struct sctp_stream *stream)
{
        struct sctp_association *asoc;
        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 = sctp_chunk_stream_no(ch);

                if (SCTP_SO(stream, sid)->ext)
                        sctp_sched_fc_sched(stream, SCTP_SO(stream, sid)->ext);
        }
}

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

        list_for_each_entry_safe(soute, tmp, &stream->fc_list, fc_list)
                list_del_init(&soute->fc_list);
}

static const struct sctp_sched_ops sctp_sched_fc = {
        .set = sctp_sched_fc_set,
        .get = sctp_sched_fc_get,
        .init = sctp_sched_fc_init,
        .init_sid = sctp_sched_fc_init_sid,
        .free_sid = sctp_sched_fc_free_sid,
        .enqueue = sctp_sched_fc_enqueue,
        .dequeue = sctp_sched_fc_dequeue,
        .dequeue_done = sctp_sched_fc_dequeue_done,
        .sched_all = sctp_sched_fc_sched_all,
        .unsched_all = sctp_sched_fc_unsched_all,
};

void sctp_sched_ops_fc_init(void)
{
        sctp_sched_ops_register(SCTP_SS_FC, &sctp_sched_fc);
}

static const struct sctp_sched_ops sctp_sched_wfq = {
        .set = sctp_sched_wfq_set,
        .get = sctp_sched_wfq_get,
        .init = sctp_sched_fc_init,
        .init_sid = sctp_sched_fc_init_sid,
        .free_sid = sctp_sched_fc_free_sid,
        .enqueue = sctp_sched_fc_enqueue,
        .dequeue = sctp_sched_fc_dequeue,
        .dequeue_done = sctp_sched_fc_dequeue_done,
        .sched_all = sctp_sched_fc_sched_all,
        .unsched_all = sctp_sched_fc_unsched_all,
};

void sctp_sched_ops_wfq_init(void)
{
        sctp_sched_ops_register(SCTP_SS_WFQ, &sctp_sched_wfq);
}