/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2003, 2004
 *
 * This file is part of the SCTP kernel implementation
 *
 * This file contains the code relating the chunk abstraction.
 *
 * 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, see
 * <http://www.gnu.org/licenses/>.
 *
 * 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:
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    Sridhar Samudrala     <sri@us.ibm.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>

/* This file is mostly in anticipation of future work, but initially
 * populate with fragment tracking for an outbound message.
 */

/* Initialize datamsg from memory. */
static void sctp_datamsg_init(struct sctp_datamsg *msg)
{
        atomic_set(&msg->refcnt, 1);
        msg->send_failed = 0;
        msg->send_error = 0;
        msg->can_abandon = 0;
        msg->can_delay = 1;
        msg->expires_at = 0;
        INIT_LIST_HEAD(&msg->chunks);
}

/* Allocate and initialize datamsg. */
static struct sctp_datamsg *sctp_datamsg_new(gfp_t gfp)
{
        struct sctp_datamsg *msg;
        msg = kmalloc(sizeof(struct sctp_datamsg), gfp);
        if (msg) {
                sctp_datamsg_init(msg);
                SCTP_DBG_OBJCNT_INC(datamsg);
        }
        return msg;
}

/* Final destructruction of datamsg memory. */
static void sctp_datamsg_destroy(struct sctp_datamsg *msg)
{
        struct list_head *pos, *temp;
        struct sctp_chunk *chunk;
        struct sctp_sock *sp;
        struct sctp_ulpevent *ev;
        struct sctp_association *asoc = NULL;
        int error = 0, notify;

        /* If we failed, we may need to notify. */
        notify = msg->send_failed ? -1 : 0;

        /* Release all references. */
        list_for_each_safe(pos, temp, &msg->chunks) {
                list_del_init(pos);
                chunk = list_entry(pos, struct sctp_chunk, frag_list);
                /* Check whether we _really_ need to notify. */
                if (notify < 0) {
                        asoc = chunk->asoc;
                        if (msg->send_error)
                                error = msg->send_error;
                        else
                                error = asoc->outqueue.error;

                        sp = sctp_sk(asoc->base.sk);
                        notify = sctp_ulpevent_type_enabled(SCTP_SEND_FAILED,
                                                            &sp->subscribe);
                }

                /* Generate a SEND FAILED event only if enabled. */
                if (notify > 0) {
                        int sent;
                        if (chunk->has_tsn)
                                sent = SCTP_DATA_SENT;
                        else
                                sent = SCTP_DATA_UNSENT;

                        ev = sctp_ulpevent_make_send_failed(asoc, chunk, sent,
                                                            error, GFP_ATOMIC);
                        if (ev)
                                sctp_ulpq_tail_event(&asoc->ulpq, ev);
                }

                sctp_chunk_put(chunk);
        }

        SCTP_DBG_OBJCNT_DEC(datamsg);
        kfree(msg);
}

/* Hold a reference. */
static void sctp_datamsg_hold(struct sctp_datamsg *msg)
{
        atomic_inc(&msg->refcnt);
}

/* Release a reference. */
void sctp_datamsg_put(struct sctp_datamsg *msg)
{
        if (atomic_dec_and_test(&msg->refcnt))
                sctp_datamsg_destroy(msg);
}

/* Assign a chunk to this datamsg. */
static void sctp_datamsg_assign(struct sctp_datamsg *msg, struct sctp_chunk *chunk)
{
        sctp_datamsg_hold(msg);
        chunk->msg = msg;
}


/* A data chunk can have a maximum payload of (2^16 - 20).  Break
 * down any such message into smaller chunks.  Opportunistically, fragment
 * the chunks down to the current MTU constraints.  We may get refragmented
 * later if the PMTU changes, but it is _much better_ to fragment immediately
 * with a reasonable guess than always doing our fragmentation on the
 * soft-interrupt.
 */
struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
                                            struct sctp_sndrcvinfo *sinfo,
                                            struct iov_iter *from)
{
        int max, whole, i, offset, over, err;
        int len, first_len;
        int max_data;
        struct sctp_chunk *chunk;
        struct sctp_datamsg *msg;
        struct list_head *pos, *temp;
        size_t msg_len = iov_iter_count(from);
        __u8 frag;

        msg = sctp_datamsg_new(GFP_KERNEL);
        if (!msg)
                return ERR_PTR(-ENOMEM);

        /* Note: Calculate this outside of the loop, so that all fragments
         * have the same expiration.
         */
        if (sinfo->sinfo_timetolive) {
                /* sinfo_timetolive is in milliseconds */
                msg->expires_at = jiffies +
                                    msecs_to_jiffies(sinfo->sinfo_timetolive);
                msg->can_abandon = 1;

                pr_debug("%s: msg:%p expires_at:%ld jiffies:%ld\n", __func__,
                         msg, msg->expires_at, jiffies);
        }

        /* This is the biggest possible DATA chunk that can fit into
         * the packet
         */
        max_data = (asoc->pathmtu -
                sctp_sk(asoc->base.sk)->pf->af->net_header_len -
                sizeof(struct sctphdr) - sizeof(struct sctp_data_chunk)) & ~3;

        max = asoc->frag_point;
        /* If the the peer requested that we authenticate DATA chunks
         * we need to account for bundling of the AUTH chunks along with
         * DATA.
         */
        if (sctp_auth_send_cid(SCTP_CID_DATA, asoc)) {
                struct sctp_hmac *hmac_desc = sctp_auth_asoc_get_hmac(asoc);

                if (hmac_desc)
                        max_data -= WORD_ROUND(sizeof(sctp_auth_chunk_t) +
                                            hmac_desc->hmac_len);
        }

        /* Now, check if we need to reduce our max */
        if (max > max_data)
                max = max_data;

        whole = 0;
        first_len = max;

        /* Check to see if we have a pending SACK and try to let it be bundled
         * with this message.  Do this if we don't have any data queued already.
         * To check that, look at out_qlen and retransmit list.
         * NOTE: we will not reduce to account for SACK, if the message would
         * not have been fragmented.
         */
        if (timer_pending(&asoc->timers[SCTP_EVENT_TIMEOUT_SACK]) &&
            asoc->outqueue.out_qlen == 0 &&
            list_empty(&asoc->outqueue.retransmit) &&
            msg_len > max)
                max_data -= WORD_ROUND(sizeof(sctp_sack_chunk_t));

        /* Encourage Cookie-ECHO bundling. */
        if (asoc->state < SCTP_STATE_COOKIE_ECHOED)
                max_data -= SCTP_ARBITRARY_COOKIE_ECHO_LEN;

        /* Now that we adjusted completely, reset first_len */
        if (first_len > max_data)
                first_len = max_data;

        /* Account for a different sized first fragment */
        if (msg_len >= first_len) {
                msg_len -= first_len;
                whole = 1;
                msg->can_delay = 0;
        }

        /* How many full sized?  How many bytes leftover? */
        whole += msg_len / max;
        over = msg_len % max;
        offset = 0;

        if ((whole > 1) || (whole && over))
                SCTP_INC_STATS_USER(sock_net(asoc->base.sk), SCTP_MIB_FRAGUSRMSGS);

        /* Create chunks for all the full sized DATA chunks. */
        for (i = 0, len = first_len; i < whole; i++) {
                frag = SCTP_DATA_MIDDLE_FRAG;

                if (0 == i)
                        frag |= SCTP_DATA_FIRST_FRAG;

                if ((i == (whole - 1)) && !over) {
                        frag |= SCTP_DATA_LAST_FRAG;

                        /* The application requests to set the I-bit of the
                         * last DATA chunk of a user message when providing
                         * the user message to the SCTP implementation.
                         */
                        if ((sinfo->sinfo_flags & SCTP_EOF) ||
                            (sinfo->sinfo_flags & SCTP_SACK_IMMEDIATELY))
                                frag |= SCTP_DATA_SACK_IMM;
                }

                chunk = sctp_make_datafrag_empty(asoc, sinfo, len, frag,
                                                 0, GFP_KERNEL);

                if (!chunk) {
                        err = -ENOMEM;
                        goto errout;
                }

                err = sctp_user_addto_chunk(chunk, len, from);
                if (err < 0)
                        goto errout_chunk_free;

                /* Put the chunk->skb back into the form expected by send.  */
                __skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr
                           - (__u8 *)chunk->skb->data);

                sctp_datamsg_assign(msg, chunk);
                list_add_tail(&chunk->frag_list, &msg->chunks);

                /* The first chunk, the first chunk was likely short
                 * to allow bundling, so reset to full size.
                 */
                if (0 == i)
                        len = max;
        }

        /* .. now the leftover bytes. */
        if (over) {
                if (!whole)
                        frag = SCTP_DATA_NOT_FRAG;
                else
                        frag = SCTP_DATA_LAST_FRAG;

                if ((sinfo->sinfo_flags & SCTP_EOF) ||
                    (sinfo->sinfo_flags & SCTP_SACK_IMMEDIATELY))
                        frag |= SCTP_DATA_SACK_IMM;

                chunk = sctp_make_datafrag_empty(asoc, sinfo, over, frag,
                                                 0, GFP_KERNEL);

                if (!chunk) {
                        err = -ENOMEM;
                        goto errout;
                }

                err = sctp_user_addto_chunk(chunk, over, from);

                /* Put the chunk->skb back into the form expected by send.  */
                __skb_pull(chunk->skb, (__u8 *)chunk->chunk_hdr
                           - (__u8 *)chunk->skb->data);
                if (err < 0)
                        goto errout_chunk_free;

                sctp_datamsg_assign(msg, chunk);
                list_add_tail(&chunk->frag_list, &msg->chunks);
        }

        return msg;

errout_chunk_free:
        sctp_chunk_free(chunk);

errout:
        list_for_each_safe(pos, temp, &msg->chunks) {
                list_del_init(pos);
                chunk = list_entry(pos, struct sctp_chunk, frag_list);
                sctp_chunk_free(chunk);
        }
        sctp_datamsg_put(msg);
        return ERR_PTR(err);
}

/* Check whether this message has expired. */
int sctp_chunk_abandoned(struct sctp_chunk *chunk)
{
        struct sctp_datamsg *msg = chunk->msg;

        if (!msg->can_abandon)
                return 0;

        if (time_after(jiffies, msg->expires_at))
                return 1;

        return 0;
}

/* This chunk (and consequently entire message) has failed in its sending. */
void sctp_chunk_fail(struct sctp_chunk *chunk, int error)
{
        chunk->msg->send_failed = 1;
        chunk->msg->send_error = error;
}