/* 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.
 *
 * This SCTP implementation is free software;
 * you can redistribute it and/or modify it under the terms of
 * the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This SCTP implementation is distributed in the hope that it
 * will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *                 ************************
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU CC; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 *
 * Please send any bug reports or fixes you make to the
 * email address(es):
 *    lksctp developers <lksctp-developers@lists.sourceforge.net>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    La Monte H.P. Yarroll <piggy@acm.org>
 *    Karl Knutson <karl@athena.chicago.il.us>
 *
 * Any bugs reported given to us we will try to fix... any fixes shared will
 * be incorporated into the next SCTP release.
 */

#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);

        queue->malloced = 0;
}

/* 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_chunk_free(queue->in_progress);
                queue->in_progress = NULL;
        }

        if (queue->malloced) {
                /* Dump the master memory segment.  */
                kfree(queue);
        }
}

/* 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;
        sctp_chunkhdr_t *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 = (sctp_chunkhdr_t *)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;
        sctp_chunkhdr_t *ch = NULL;

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

        if ((chunk = queue->in_progress)) {
                /* 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) {
                        sctp_chunk_free(chunk);
                        chunk = queue->in_progress = NULL;
                } else {
                        /* Nothing to do. Next chunk in the packet, please. */
                        ch = (sctp_chunkhdr_t *) chunk->chunk_end;

                        /* Force chunk->skb->data to chunk->chunk_end.  */
                        skb_pull(chunk->skb,
                                 chunk->chunk_end - chunk->skb->data);

                        /* Verify that we have at least chunk headers
                         * worth of buffer left.
                         */
                        if (skb_headlen(chunk->skb) < sizeof(sctp_chunkhdr_t)) {
                                sctp_chunk_free(chunk);
                                chunk = queue->in_progress = NULL;
                        }
                }
        }

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

                /* Is the queue empty?  */
                if (list_empty(&queue->in_chunk_list))
                        return NULL;

                entry = queue->in_chunk_list.next;
                chunk = queue->in_progress =
                        list_entry(entry, struct sctp_chunk, list);
                list_del_init(entry);

                /* This is the first chunk in the packet.  */
                chunk->singleton = 1;
                ch = (sctp_chunkhdr_t *) chunk->skb->data;
                chunk->data_accepted = 0;
        }

        chunk->chunk_hdr = ch;
        chunk->chunk_end = ((__u8 *)ch) + WORD_ROUND(ntohs(ch->length));
        /* In the unlikely case of an IP reassembly, the skb could be
         * non-linear. If so, update chunk_end so that it doesn't go past
         * the skb->tail.
         */
        if (unlikely(skb_is_nonlinear(chunk->skb))) {
                if (chunk->chunk_end > skb_tail_pointer(chunk->skb))
                        chunk->chunk_end = skb_tail_pointer(chunk->skb);
        }
        skb_pull(chunk->skb, sizeof(sctp_chunkhdr_t));
        chunk->subh.v = NULL; /* Subheader is no longer valid.  */

        if (chunk->chunk_end < skb_tail_pointer(chunk->skb)) {
                /* This is not a singleton */
                chunk->singleton = 0;
        } else if (chunk->chunk_end > skb_tail_pointer(chunk->skb)) {
                /* RFC 2960, Section 6.10  Bundling
                 *
                 * Partial chunks MUST NOT be placed in an SCTP packet.
                 * If the receiver detects a partial chunk, it MUST drop
                 * the chunk.
                 *
                 * Since the end of the chunk is past the end of our buffer
                 * (which contains the whole packet, we can freely discard
                 * the whole packet.
                 */
                sctp_chunk_free(chunk);
                chunk = queue->in_progress = NULL;

                return NULL;
        } 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;
        }

        SCTP_DEBUG_PRINTK("+++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);
}