// SPDX-License-Identifier: GPL-2.0-or-later
/* SCTP kernel implementation
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2002 International Business Machines, Corp.
 *
 * This file is part of the SCTP kernel implementation
 *
 * These functions are the methods for accessing the SCTP inqueue.
 *
 * An SCTP inqueue is a queue into which you push SCTP packets
 * (which might be bundles or fragments of chunks) and out of which you
 * pop SCTP whole chunks.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <linux-sctp@vger.kernel.org>
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson <karl@athena.chicago.il.us>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>
#include <linux/interrupt.h>
#include <linux/slab.h>

/* Initialize an SCTP inqueue.  */
void sctp_inq_init(struct sctp_inq *queue)
{
        INIT_LIST_HEAD(&queue->in_chunk_list);
        queue->in_progress = NULL;

        /* Create a task for delivering data.  */
        INIT_WORK(&queue->immediate, NULL);
}

/* Properly release the chunk which is being worked on. */
static inline void sctp_inq_chunk_free(struct sctp_chunk *chunk)
{
        if (chunk->head_skb)
                chunk->skb = chunk->head_skb;
        sctp_chunk_free(chunk);
}

/* Release the memory associated with an SCTP inqueue.  */
void sctp_inq_free(struct sctp_inq *queue)
{
        struct sctp_chunk *chunk, *tmp;

        /* Empty the queue.  */
        list_for_each_entry_safe(chunk, tmp, &queue->in_chunk_list, list) {
                list_del_init(&chunk->list);
                sctp_chunk_free(chunk);
        }

        /* If there is a packet which is currently being worked on,
         * free it as well.
         */
        if (queue->in_progress) {
                sctp_inq_chunk_free(queue->in_progress);
                queue->in_progress = NULL;
        }
}

/* Put a new packet in an SCTP inqueue.
 * We assume that packet->sctp_hdr is set and in host byte order.
 */
void sctp_inq_push(struct sctp_inq *q, struct sctp_chunk *chunk)
{
        /* Directly call the packet handling routine. */
        if (chunk->rcvr->dead) {
                sctp_chunk_free(chunk);
                return;
        }

        /* We are now calling this either from the soft interrupt
         * or from the backlog processing.
         * Eventually, we should clean up inqueue to not rely
         * on the BH related data structures.
         */
        list_add_tail(&chunk->list, &q->in_chunk_list);
        if (chunk->asoc)
                chunk->asoc->stats.ipackets++;
        q->immediate.func(&q->immediate);
}

/* Peek at the next chunk on the inqeue. */
struct sctp_chunkhdr *sctp_inq_peek(struct sctp_inq *queue)
{
        struct sctp_chunk *chunk;
        struct sctp_chunkhdr *ch = NULL;

        chunk = queue->in_progress;
        /* If there is no more chunks in this packet, say so */
        if (chunk->singleton ||
            chunk->end_of_packet ||
            chunk->pdiscard)
                    return NULL;

        ch = (struct sctp_chunkhdr *)chunk->chunk_end;

        return ch;
}


/* Extract a chunk from an SCTP inqueue.
 *
 * WARNING:  If you need to put the chunk on another queue, you need to
 * make a shallow copy (clone) of it.
 */
struct sctp_chunk *sctp_inq_pop(struct sctp_inq *queue)
{
        struct sctp_chunk *chunk;
        struct sctp_chunkhdr *ch = NULL;

        /* The assumption is that we are safe to process the chunks
         * at this time.
         */

        chunk = queue->in_progress;
        if (chunk) {
                /* There is a packet that we have been working on.
                 * Any post processing work to do before we move on?
                 */
                if (chunk->singleton ||
                    chunk->end_of_packet ||
                    chunk->pdiscard) {
                        if (chunk->head_skb == chunk->skb) {
                                chunk->skb = skb_shinfo(chunk->skb)->frag_list;
                                goto new_skb;
                        }
                        if (chunk->skb->next) {
                                chunk->skb = chunk->skb->next;
                                goto new_skb;
                        }

                        sctp_inq_chunk_free(chunk);
                        chunk = queue->in_progress = NULL;
                } else {
                        /* Nothing to do. Next chunk in the packet, please. */
                        ch = (struct sctp_chunkhdr *)chunk->chunk_end;
                        /* Force chunk->skb->data to chunk->chunk_end.  */
                        skb_pull(chunk->skb, chunk->chunk_end - chunk->skb->data);
                        /* We are guaranteed to pull a SCTP header. */
                }
        }

        /* Do we need to take the next packet out of the queue to process? */
        if (!chunk) {
                struct list_head *entry;

next_chunk:
                /* Is the queue empty?  */
                entry = sctp_list_dequeue(&queue->in_chunk_list);
                if (!entry)
                        return NULL;

                chunk = list_entry(entry, struct sctp_chunk, list);

                if (skb_is_gso(chunk->skb) && skb_is_gso_sctp(chunk->skb)) {
                        /* GSO-marked skbs but without frags, handle
                         * them normally
                         */
                        if (skb_shinfo(chunk->skb)->frag_list)
                                chunk->head_skb = chunk->skb;

                        /* skbs with "cover letter" */
                        if (chunk->head_skb && chunk->skb->data_len == chunk->skb->len) {
                                if (WARN_ON(!skb_shinfo(chunk->skb)->frag_list)) {
                                        __SCTP_INC_STATS(dev_net(chunk->skb->dev),
                                                         SCTP_MIB_IN_PKT_DISCARDS);
                                        sctp_chunk_free(chunk);
                                        goto next_chunk;
                                }
                                chunk->skb = skb_shinfo(chunk->skb)->frag_list;
                        }
                }

                if (chunk->asoc)
                        sock_rps_save_rxhash(chunk->asoc->base.sk, chunk->skb);

                queue->in_progress = chunk;

new_skb:
                /* This is the first chunk in the packet.  */
                ch = (struct sctp_chunkhdr *)chunk->skb->data;
                chunk->singleton = 1;
                chunk->data_accepted = 0;
                chunk->pdiscard = 0;
                chunk->auth = 0;
                chunk->has_asconf = 0;
                chunk->end_of_packet = 0;
                if (chunk->head_skb) {
                        struct sctp_input_cb
                                *cb = SCTP_INPUT_CB(chunk->skb),
                                *head_cb = SCTP_INPUT_CB(chunk->head_skb);

                        cb->chunk = head_cb->chunk;
                        cb->af = head_cb->af;
                }
        }

        chunk->chunk_hdr = ch;
        chunk->chunk_end = ((__u8 *)ch) + SCTP_PAD4(ntohs(ch->length));
        skb_pull(chunk->skb, sizeof(*ch));
        chunk->subh.v = NULL; /* Subheader is no longer valid.  */

        if (chunk->chunk_end + sizeof(*ch) <= skb_tail_pointer(chunk->skb)) {
                /* This is not a singleton */
                chunk->singleton = 0;
        } else if (chunk->chunk_end > skb_tail_pointer(chunk->skb)) {
                /* Discard inside state machine. */
                chunk->pdiscard = 1;
                chunk->chunk_end = skb_tail_pointer(chunk->skb);
        } else {
                /* We are at the end of the packet, so mark the chunk
                 * in case we need to send a SACK.
                 */
                chunk->end_of_packet = 1;
        }

        pr_debug("+++sctp_inq_pop+++ chunk:%p[%s], length:%d, skb->len:%d\n",
                 chunk, sctp_cname(SCTP_ST_CHUNK(chunk->chunk_hdr->type)),
                 ntohs(chunk->chunk_hdr->length), chunk->skb->len);

        return chunk;
}

/* Set a top-half handler.
 *
 * Originally, we the top-half handler was scheduled as a BH.  We now
 * call the handler directly in sctp_inq_push() at a time that
 * we know we are lock safe.
 * The intent is that this routine will pull stuff out of the
 * inqueue and process it.
 */
void sctp_inq_set_th_handler(struct sctp_inq *q, work_func_t callback)
{
        INIT_WORK(&q->immediate, callback);
}