chunk.c

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/* 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, 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 <[email protected]>
 *
 * Or submit a bug report through the following website:
 *    http://www.sf.net/projects/lksctp
 *
 * Written or modified by:
 *    Jon Grimm             <[email protected]>
 *    Sridhar Samudrala     <[email protected]>
 *
 * 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 <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. */
SCTP_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;
}

void sctp_datamsg_free(struct sctp_datamsg *msg)
{
    struct sctp_chunk *chunk;

    /* This doesn't have to be a _safe vairant because
     * sctp_chunk_free() only drops the refs.
     */
    list_for_each_entry(chunk, &msg->chunks, frag_list)
        sctp_chunk_free(chunk);

    sctp_datamsg_put(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 msghdr *msgh, int msg_len)
{
    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;
    __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;
        SCTP_DEBUG_PRINTK("%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);

    max = asoc->frag_point;
    /* If the the peer requested that we authenticate DATA chunks
     * we need to accound 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);

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

        err = sctp_user_addto_chunk(chunk, offset, len, msgh->msg_iov);
        if (err < 0)
            goto errout_chunk_free;

        offset += len;

        /* 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);

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

        err = sctp_user_addto_chunk(chunk, offset, over,msgh->msg_iov);

        /* 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;
}