source: mainline/uspace/srv/net/tl/tcp/segment.c@ 032bbe7

/*
 * Copyright (c) 2011 Jiri Svoboda
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup tcp
 * @{
 */

/**
 * @file Segment processing
 */

#include <mem.h>
#include <stdlib.h>
#include "segment.h"
#include "seq_no.h"
#include "tcp_type.h"

/** Alocate new segment structure. */
tcp_segment_t *tcp_segment_new(void)
{
        return calloc(1, sizeof(tcp_segment_t));
}

/** Delete segment. */
void tcp_segment_delete(tcp_segment_t *seg)
{
        free(seg);
}

/** Create a control segment.
 *
  * @return     Control segment
 */
tcp_segment_t *tcp_segment_make_ctrl(tcp_control_t ctrl)
{
        tcp_segment_t *seg;

        seg = tcp_segment_new();
        if (seg == NULL)
                return NULL;

        seg->ctrl = ctrl;
        seg->len = seq_no_control_len(ctrl);

        return seg;
}

/** Create an RST segment.
 *
 * @param seg   Segment we are replying to
 * @return      RST segment
 */
tcp_segment_t *tcp_segment_make_rst(tcp_segment_t *seg)
{
        tcp_segment_t *rseg;

        rseg = tcp_segment_new();
        if (rseg == NULL)
                return NULL;

        rseg->ctrl = CTL_RST;
        rseg->seq = seg->ack;

        return rseg;
}

/** Trim segment from left and right by the specified amount.
 *
 * Trim any text or control to remove the specified amount of sequence
 * numbers from the left (lower sequence numbers) and right side
 * (higher sequence numbers) of the segment.
 *
 * @param seg           Segment, will be modified in place
 * @param left          Amount of sequence numbers to trim from the left
 * @param right         Amount of sequence numbers to trim from the right
 */
void tcp_segment_trim(tcp_segment_t *seg, uint32_t left, uint32_t right)
{
        uint32_t t_size;

        assert(left + right <= seg->len);

        /* Special case, entire segment trimmed from left */
        if (left == seg->len) {
                seg->seq = seg->seq + seg->len;
                seg->len = 0;
                return;
        }

        /* Special case, entire segment trimmed from right */
        if (right == seg->len) {
                seg->len = 0;
                return;
        }

        /* General case */

        t_size = tcp_segment_text_size(seg);

        if (left > 0 && (seg->ctrl & CTL_SYN) != 0) {
                /* Trim SYN */
                seg->ctrl &= ~CTL_SYN;
                seg->seq++;
                seg->len--;
                left--;
        }

        if (right > 0 && (seg->ctrl & CTL_FIN) != 0) {
                /* Trim FIN */
                seg->ctrl &= ~CTL_FIN;
                seg->len--;
                right--;
        }

        if (left > 0 || right > 0) {
                /* Trim segment text */
                assert(left + right <= t_size);

                seg->data += left;
                seg->len -= left + right;
        }
}

/** Copy out text data from segment.
 *
 * Data is copied from the beginning of the segment text up to @a size bytes.
 * @a size must not be greater than the size of the segment text, but
 * it can be less.
 *
 * @param seg   Segment
 * @param buf   Destination buffer
 * @param size  Size of destination buffer
 */
void tcp_segment_text_copy(tcp_segment_t *seg, void *buf, size_t size)
{
        assert(size <= tcp_segment_text_size(seg));
        memcpy(buf, seg->data, size);
}

/** Return number of bytes in segment text.
 *
 * @param seg   Segment
 * @return      Number of bytes in segment text
 */
size_t tcp_segment_text_size(tcp_segment_t *seg)
{
        return seg->len - seq_no_control_len(seg->ctrl);
}

/**
 * @}
 */