tsnmap.c

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/* SCTP kernel implementation
 * (C) Copyright IBM Corp. 2001, 2004
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001 Intel Corp.
 *
 * This file is part of the SCTP kernel implementation
 *
 * These functions manipulate sctp tsn mapping array.
 *
 * 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:
 *    La Monte H.P. Yarroll <[email protected]>
 *    Jon Grimm             <[email protected]>
 *    Karl Knutson          <[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.
 */

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

static void sctp_tsnmap_update(struct sctp_tsnmap *map);
static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
                     __u16 len, __u16 *start, __u16 *end);
static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 gap);

/* Initialize a block of memory as a tsnmap.  */
struct sctp_tsnmap *sctp_tsnmap_init(struct sctp_tsnmap *map, __u16 len,
                     __u32 initial_tsn, gfp_t gfp)
{
    if (!map->tsn_map) {
        map->tsn_map = kzalloc(len>>3, gfp);
        if (map->tsn_map == NULL)
            return NULL;

        map->len = len;
    } else {
        bitmap_zero(map->tsn_map, map->len);
    }

    /* Keep track of TSNs represented by tsn_map.  */
    map->base_tsn = initial_tsn;
    map->cumulative_tsn_ack_point = initial_tsn - 1;
    map->max_tsn_seen = map->cumulative_tsn_ack_point;
    map->num_dup_tsns = 0;

    return map;
}

void sctp_tsnmap_free(struct sctp_tsnmap *map)
{
    map->len = 0;
    kfree(map->tsn_map);
}

/* Test the tracking state of this TSN.
 * Returns:
 *   0 if the TSN has not yet been seen
 *  >0 if the TSN has been seen (duplicate)
 *  <0 if the TSN is invalid (too large to track)
 */
int sctp_tsnmap_check(const struct sctp_tsnmap *map, __u32 tsn)
{
    u32 gap;

    /* Check to see if this is an old TSN */
    if (TSN_lte(tsn, map->cumulative_tsn_ack_point))
        return 1;

    /* Verify that we can hold this TSN and that it will not
     * overlfow our map
     */
    if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
        return -1;

    /* Calculate the index into the mapping arrays.  */
    gap = tsn - map->base_tsn;

    /* Check to see if TSN has already been recorded.  */
    if (gap < map->len && test_bit(gap, map->tsn_map))
        return 1;
    else
        return 0;
}


/* Mark this TSN as seen.  */
int sctp_tsnmap_mark(struct sctp_tsnmap *map, __u32 tsn,
             struct sctp_transport *trans)
{
    u16 gap;

    if (TSN_lt(tsn, map->base_tsn))
        return 0;

    gap = tsn - map->base_tsn;

    if (gap >= map->len && !sctp_tsnmap_grow(map, gap))
        return -ENOMEM;

    if (!sctp_tsnmap_has_gap(map) && gap == 0) {
        /* In this case the map has no gaps and the tsn we are
         * recording is the next expected tsn.  We don't touch
         * the map but simply bump the values.
         */
        map->max_tsn_seen++;
        map->cumulative_tsn_ack_point++;
        if (trans)
            trans->sack_generation =
                trans->asoc->peer.sack_generation;
        map->base_tsn++;
    } else {
        /* Either we already have a gap, or about to record a gap, so
         * have work to do.
         *
         * Bump the max.
         */
        if (TSN_lt(map->max_tsn_seen, tsn))
            map->max_tsn_seen = tsn;

        /* Mark the TSN as received.  */
        set_bit(gap, map->tsn_map);

        /* Go fixup any internal TSN mapping variables including
         * cumulative_tsn_ack_point.
         */
        sctp_tsnmap_update(map);
    }

    return 0;
}


/* Initialize a Gap Ack Block iterator from memory being provided.  */
SCTP_STATIC void sctp_tsnmap_iter_init(const struct sctp_tsnmap *map,
                       struct sctp_tsnmap_iter *iter)
{
    /* Only start looking one past the Cumulative TSN Ack Point.  */
    iter->start = map->cumulative_tsn_ack_point + 1;
}

/* Get the next Gap Ack Blocks. Returns 0 if there was not another block
 * to get.
 */
SCTP_STATIC int sctp_tsnmap_next_gap_ack(const struct sctp_tsnmap *map,
                     struct sctp_tsnmap_iter *iter,
                     __u16 *start, __u16 *end)
{
    int ended = 0;
    __u16 start_ = 0, end_ = 0, offset;

    /* If there are no more gap acks possible, get out fast.  */
    if (TSN_lte(map->max_tsn_seen, iter->start))
        return 0;

    offset = iter->start - map->base_tsn;
    sctp_tsnmap_find_gap_ack(map->tsn_map, offset, map->len,
                 &start_, &end_);

    /* The Gap Ack Block happens to end at the end of the map. */
    if (start_ && !end_)
        end_ = map->len - 1;

    /* If we found a Gap Ack Block, return the start and end and
     * bump the iterator forward.
     */
    if (end_) {
        /* Fix up the start and end based on the
         * Cumulative TSN Ack which is always 1 behind base.
         */
        *start = start_ + 1;
        *end = end_ + 1;

        /* Move the iterator forward.  */
        iter->start = map->cumulative_tsn_ack_point + *end + 1;
        ended = 1;
    }

    return ended;
}

/* Mark this and any lower TSN as seen.  */
void sctp_tsnmap_skip(struct sctp_tsnmap *map, __u32 tsn)
{
    u32 gap;

    if (TSN_lt(tsn, map->base_tsn))
        return;
    if (!TSN_lt(tsn, map->base_tsn + SCTP_TSN_MAP_SIZE))
        return;

    /* Bump the max.  */
    if (TSN_lt(map->max_tsn_seen, tsn))
        map->max_tsn_seen = tsn;

    gap = tsn - map->base_tsn + 1;

    map->base_tsn += gap;
    map->cumulative_tsn_ack_point += gap;
    if (gap >= map->len) {
        /* If our gap is larger then the map size, just
         * zero out the map.
         */
        bitmap_zero(map->tsn_map, map->len);
    } else {
        /* If the gap is smaller than the map size,
         * shift the map by 'gap' bits and update further.
         */
        bitmap_shift_right(map->tsn_map, map->tsn_map, gap, map->len);
        sctp_tsnmap_update(map);
    }
}

/********************************************************************
 * 2nd Level Abstractions
 ********************************************************************/

/* This private helper function updates the tsnmap buffers and
 * the Cumulative TSN Ack Point.
 */
static void sctp_tsnmap_update(struct sctp_tsnmap *map)
{
    u16 len;
    unsigned long zero_bit;


    len = map->max_tsn_seen - map->cumulative_tsn_ack_point;
    zero_bit = find_first_zero_bit(map->tsn_map, len);
    if (!zero_bit)
        return;     /* The first 0-bit is bit 0.  nothing to do */

    map->base_tsn += zero_bit;
    map->cumulative_tsn_ack_point += zero_bit;

    bitmap_shift_right(map->tsn_map, map->tsn_map, zero_bit, map->len);
}

/* How many data chunks  are we missing from our peer?
 */
__u16 sctp_tsnmap_pending(struct sctp_tsnmap *map)
{
    __u32 cum_tsn = map->cumulative_tsn_ack_point;
    __u32 max_tsn = map->max_tsn_seen;
    __u32 base_tsn = map->base_tsn;
    __u16 pending_data;
    u32 gap, i;

    pending_data = max_tsn - cum_tsn;
    gap = max_tsn - base_tsn;

    if (gap == 0 || gap >= map->len)
        goto out;

    for (i = 0; i < gap+1; i++) {
        if (test_bit(i, map->tsn_map))
            pending_data--;
    }

out:
    return pending_data;
}

/* This is a private helper for finding Gap Ack Blocks.  It searches a
 * single array for the start and end of a Gap Ack Block.
 *
 * The flags "started" and "ended" tell is if we found the beginning
 * or (respectively) the end of a Gap Ack Block.
 */
static void sctp_tsnmap_find_gap_ack(unsigned long *map, __u16 off,
                     __u16 len, __u16 *start, __u16 *end)
{
    int i = off;

    /* Look through the entire array, but break out
     * early if we have found the end of the Gap Ack Block.
     */

    /* Also, stop looking past the maximum TSN seen. */

    /* Look for the start. */
    i = find_next_bit(map, len, off);
    if (i < len)
        *start = i;

    /* Look for the end.  */
    if (*start) {
        /* We have found the start, let's find the
         * end.  If we find the end, break out.
         */
        i = find_next_zero_bit(map, len, i);
        if (i < len)
            *end = i - 1;
    }
}

/* Renege that we have seen a TSN.  */
void sctp_tsnmap_renege(struct sctp_tsnmap *map, __u32 tsn)
{
    u32 gap;

    if (TSN_lt(tsn, map->base_tsn))
        return;
    /* Assert: TSN is in range.  */
    if (!TSN_lt(tsn, map->base_tsn + map->len))
        return;

    gap = tsn - map->base_tsn;

    /* Pretend we never saw the TSN.  */
    clear_bit(gap, map->tsn_map);
}

/* How many gap ack blocks do we have recorded? */
__u16 sctp_tsnmap_num_gabs(struct sctp_tsnmap *map,
               struct sctp_gap_ack_block *gabs)
{
    struct sctp_tsnmap_iter iter;
    int ngaps = 0;

    /* Refresh the gap ack information. */
    if (sctp_tsnmap_has_gap(map)) {
        __u16 start = 0, end = 0;
        sctp_tsnmap_iter_init(map, &iter);
        while (sctp_tsnmap_next_gap_ack(map, &iter,
                        &start,
                        &end)) {

            gabs[ngaps].start = htons(start);
            gabs[ngaps].end = htons(end);
            ngaps++;
            if (ngaps >= SCTP_MAX_GABS)
                break;
        }
    }
    return ngaps;
}

static int sctp_tsnmap_grow(struct sctp_tsnmap *map, u16 gap)
{
    unsigned long *new;
    unsigned long inc;
    u16  len;

    if (gap >= SCTP_TSN_MAP_SIZE)
        return 0;

    inc = ALIGN((gap - map->len),BITS_PER_LONG) + SCTP_TSN_MAP_INCREMENT;
    len = min_t(u16, map->len + inc, SCTP_TSN_MAP_SIZE);

    new = kzalloc(len>>3, GFP_ATOMIC);
    if (!new)
        return 0;

    bitmap_copy(new, map->tsn_map, map->max_tsn_seen - map->base_tsn);
    kfree(map->tsn_map);
    map->tsn_map = new;
    map->len = len;

    return 1;
}