net/sctp/tsnmap.c

/* SCTP kernel reference Implementation
 * Copyright (c) 1999-2000 Cisco, Inc.
 * Copyright (c) 1999-2001 Motorola, Inc.
 * Copyright (c) 2001 International Business Machines, Corp.
 * Copyright (c) 2001 Intel Corp.
 * 
 * This file is part of the SCTP kernel reference Implementation
 * 
 * These functions manipulate sctp tsn mapping array.
 * 
 * The SCTP reference 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.
 * 
 * The SCTP reference 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>
 *    Jon Grimm             <jgrimm@us.ibm.com>
 *    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.
 */

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

static void _sctp_tsnmap_update(sctp_tsnmap_t *map);
static void _sctp_tsnmap_update_pending_data(sctp_tsnmap_t *map);
static void _sctp_tsnmap_find_gap_ack(__u8 *map, __u16 off,
				      __u16 len, __u16 base,
				      int *started, __u16 *start,
				      int *ended, __u16 *end);

/* Create a new sctp_tsnmap.
 * Allocate room to store at least 'len' contiguous TSNs.
 */
sctp_tsnmap_t *sctp_tsnmap_new(__u16 len, __u32 initial_tsn, int priority)
{
	sctp_tsnmap_t *retval;

	retval = kmalloc(sizeof(sctp_tsnmap_t) +
			 sctp_tsnmap_storage_size(len),
			 priority);
	if (!retval)
		goto fail;

	if (!sctp_tsnmap_init(retval, len, initial_tsn))
		goto fail_map;
	retval->malloced = 1;
	return retval;

fail_map:
	kfree(retval);

fail:
	return NULL;
}

/* Initialize a block of memory as a tsnmap.  */
sctp_tsnmap_t *sctp_tsnmap_init(sctp_tsnmap_t *map, __u16 len, __u32 initial_tsn)
{
	map->tsn_map = map->raw_map;
	map->overflow_map = map->tsn_map + len;
	map->len = len;

	/* Clear out a TSN ack status.  */
	memset(map->tsn_map, 0x00, map->len + map->len);

	/* Keep track of TSNs represented by tsn_map.  */
	map->base_tsn = initial_tsn;
	map->overflow_tsn = initial_tsn + map->len;
	map->cumulative_tsn_ack_point = initial_tsn - 1;
	map->max_tsn_seen = map->cumulative_tsn_ack_point;
	map->malloced = 0;
	map->pending_data = 0;

	return 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 sctp_tsnmap_t *map, __u32 tsn)
{
	__s32 gap;
	int dup;

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

	/* Verify that we can hold this TSN.  */
	if (gap >= (/* base */ map->len + /* overflow */ map->len)) {
		dup = -1;
		goto out;
	}

	/* Honk if we've already seen this TSN.
	 * We have three cases:
	 *	1. The TSN is ancient or belongs to a previous tsn_map.
	 *	2. The TSN is already marked in the tsn_map.
	 *	3. The TSN is already marked in the tsn_map_overflow.
	 */
	if (gap < 0 ||
	    (gap < map->len && map->tsn_map[gap]) ||
	    (gap >= map->len && map->overflow_map[gap - map->len]))
		dup = 1;
	else
		dup = 0;

out:
	return dup;
}

/* Is there a gap in the TSN map?  */
int sctp_tsnmap_has_gap(const sctp_tsnmap_t *map)
{
	int has_gap;

	has_gap = (map->cumulative_tsn_ack_point != map->max_tsn_seen);
	return has_gap;
}

/* Mark this TSN as seen.  */
void sctp_tsnmap_mark(sctp_tsnmap_t *map, __u32 tsn)
{
	__s32 gap;

	/* Vacuously mark any TSN which precedes the map base or
	 * exceeds the end of the map.
	 */
	if (TSN_lt(tsn, map->base_tsn))
		return;
	if (!TSN_lt(tsn, map->base_tsn + map->len + map->len))
		return;

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

	/* Assert: TSN is in range.  */
	gap = tsn - map->base_tsn;

	/* Mark the TSN as received.  */
	if (gap < map->len)
		map->tsn_map[gap]++;
	else
		map->overflow_map[gap - map->len]++;

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

/* Retrieve the Cumulative TSN Ack Point. */
__u32 sctp_tsnmap_get_ctsn(const sctp_tsnmap_t *map)
{
	return map->cumulative_tsn_ack_point;
}

/* Retrieve the highest TSN we've seen.  */
__u32 sctp_tsnmap_get_max_tsn_seen(const sctp_tsnmap_t *map)
{
	return map->max_tsn_seen;
}

/* Dispose of a tsnmap.  */
void sctp_tsnmap_free(sctp_tsnmap_t *map)
{
	if (map->malloced)
		kfree(map);
}

/* Initialize a Gap Ack Block iterator from memory being provided.  */
void sctp_tsnmap_iter_init(const sctp_tsnmap_t *map, sctp_tsnmap_iter_t *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.
 */
int sctp_tsnmap_next_gap_ack(const sctp_tsnmap_t *map, sctp_tsnmap_iter_t *iter,
			     __u16 *start, __u16 *end)
{
	int started, ended;
	__u16 _start, _end, offset;

	/* We haven't found a gap yet.  */
	started = ended = 0;

	/* Search the first mapping array.  */
	if (iter->start - map->base_tsn < map->len) {
		offset = iter->start - map->base_tsn;
		_sctp_tsnmap_find_gap_ack(map->tsn_map,
					  offset,
					  map->len, 0,
					  &started, &_start,
					  &ended, &_end);
	}

	/* Do we need to check the overflow map? */
	if (!ended) {
		/* Fix up where we'd like to start searching in the
		 * overflow map.
		 */
		if (iter->start - map->base_tsn < map->len)
			offset = 0;
		else
			offset = iter->start - map->base_tsn - map->len;

		/* Search the overflow map.  */
		_sctp_tsnmap_find_gap_ack(map->overflow_map,
					  offset,
					  map->len,
					  map->len,
					  &started, &_start,
					  &ended, &_end);
	}

	/* The Gap Ack Block happens to end at the end of the
	 * overflow map.
	 */
	if (started & !ended) {
		ended++;
		_end = map->len + map->len - 1;
	}

	/* If we found a Gap Ack Block, return the start and end and
	 * bump the iterator forward.
	 */
	if (ended) {
		/* Fix up the start and end based on the
		 * Cumulative TSN Ack offset into the map.
		 */
		int gap = map->cumulative_tsn_ack_point -
			map->base_tsn;

		*start = _start - gap;
		*end = _end - gap;

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

	return ended;
}

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

/* This private helper function updates the tsnmap buffers and
 * the Cumulative TSN Ack Point.
 */
static void _sctp_tsnmap_update(sctp_tsnmap_t *map)
{
	__u32 ctsn;

	ctsn = map->cumulative_tsn_ack_point;
	do {
		ctsn++;
		if (ctsn == map->overflow_tsn) {
			/* Now tsn_map must have been all '1's,
			 * so we swap the map and check the overflow table
			 */
        		__u8 *tmp = map->tsn_map;
			memset(tmp, 0, map->len);
			map->tsn_map = map->overflow_map;
			map->overflow_map = tmp;

			/* Update the tsn_map boundaries.  */
			map->base_tsn += map->len;
			map->overflow_tsn += map->len;
		}
	} while (map->tsn_map[ctsn - map->base_tsn]);

	map->cumulative_tsn_ack_point = ctsn - 1; /* Back up one. */
	_sctp_tsnmap_update_pending_data(map);
}

static void _sctp_tsnmap_update_pending_data(sctp_tsnmap_t *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;
	__s32 gap, start, end, i;

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

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

	start = ((cum_tsn >= base_tsn) ? (cum_tsn - base_tsn + 1) : 0);
	end = ((gap > map->len ) ? map->len : gap + 1);

	for (i = start; i < end; i++) {
		if (map->tsn_map[i])
			pending_data--;
	} 

	if (gap >= map->len) {
		start = 0;
		end = gap - map->len + 1;
		for (i = start; i < end; i++) {
			if (map->overflow_map[i])
				pending_data--;
		}
	}

out:
	map->pending_data = 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(__u8 *map, __u16 off,
				      __u16 len, __u16 base,
				      int *started, __u16 *start,
				      int *ended, __u16 *end)
{
	int i = off;

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

	/* Look for the start. */
	if (!(*started)) {
		for (; i < len; i++) {
			if (map[i]) {
				(*started)++;
				*start = base + i;
				break;
			}
		}
	}

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