source: mainline/uspace/srv/net/tcp/pdu.c@ a2e3ee6

/*
 * 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 TCP header encoding and decoding
 */

#include <bitops.h>
#include <byteorder.h>
#include <errno.h>
#include <mem.h>
#include <stdlib.h>
#include "pdu.h"
#include "segment.h"
#include "seq_no.h"
#include "std.h"
#include "tcp_type.h"

#define TCP_CHECKSUM_INIT 0xffff

/** One's complement addition.
 *
 * Result is a + b + carry.
 */
static uint16_t tcp_ocadd16(uint16_t a, uint16_t b)
{
        uint32_t s;

        s = (uint32_t)a + (uint32_t)b;
        return (s & 0xffff) + (s >> 16);
}

static uint16_t tcp_checksum_calc(uint16_t ivalue, void *data, size_t size)
{
        uint16_t sum;
        uint16_t w;
        size_t words, i;
        uint8_t *bdata;

        sum = ~ivalue;
        words = size / 2;
        bdata = (uint8_t *)data;

        for (i = 0; i < words; i++) {
                w = ((uint16_t)bdata[2*i] << 8) | bdata[2*i + 1];
                sum = tcp_ocadd16(sum, w);
        }

        if (size % 2 != 0) {
                w = ((uint16_t)bdata[2*words] << 8);
                sum = tcp_ocadd16(sum, w);
        }

        return ~sum;
}

static void tcp_header_decode_flags(uint16_t doff_flags, tcp_control_t *rctl)
{
        tcp_control_t ctl;

        ctl = 0;

        if ((doff_flags & BIT_V(uint16_t, DF_URG)) != 0)
                ctl |= 0 /* XXX */;
        if ((doff_flags & BIT_V(uint16_t, DF_ACK)) != 0)
                ctl |= CTL_ACK;
        if ((doff_flags & BIT_V(uint16_t, DF_PSH)) != 0)
                ctl |= 0 /* XXX */;
        if ((doff_flags & BIT_V(uint16_t, DF_RST)) != 0)
                ctl |= CTL_RST;
        if ((doff_flags & BIT_V(uint16_t, DF_SYN)) != 0)
                ctl |= CTL_SYN;
        if ((doff_flags & BIT_V(uint16_t, DF_FIN)) != 0)
                ctl |= CTL_FIN;

        *rctl = ctl;
}

static void tcp_header_encode_flags(tcp_control_t ctl, uint16_t doff_flags0,
    uint16_t *rdoff_flags)
{
        uint16_t doff_flags;

        doff_flags = doff_flags0;

        if ((ctl & CTL_ACK) != 0)
                doff_flags |= BIT_V(uint16_t, DF_ACK);
        if ((ctl & CTL_RST) != 0)
                doff_flags |= BIT_V(uint16_t, DF_RST);
        if ((ctl & CTL_SYN) != 0)
                doff_flags |= BIT_V(uint16_t, DF_SYN);
        if ((ctl & CTL_FIN) != 0)
                doff_flags |= BIT_V(uint16_t, DF_FIN);

        *rdoff_flags = doff_flags;
}

static void tcp_header_setup(tcp_sockpair_t *sp, tcp_segment_t *seg, tcp_header_t *hdr)
{
        uint16_t doff_flags;
        uint16_t doff;

        hdr->src_port = host2uint16_t_be(sp->local.port);
        hdr->dest_port = host2uint16_t_be(sp->foreign.port);
        hdr->seq = host2uint32_t_be(seg->seq);
        hdr->ack = host2uint32_t_be(seg->ack);

        doff = (sizeof(tcp_header_t) / sizeof(uint32_t)) << DF_DATA_OFFSET_l;
        tcp_header_encode_flags(seg->ctrl, doff, &doff_flags);

        hdr->doff_flags = host2uint16_t_be(doff_flags);
        hdr->window = host2uint16_t_be(seg->wnd);
        hdr->checksum = 0;
        hdr->urg_ptr = host2uint16_t_be(seg->up);
}

static void tcp_phdr_setup(tcp_pdu_t *pdu, tcp_phdr_t *phdr)
{
        // FIXME: Check for correctness
        
        uint32_t src_addr;
        inet_addr_pack(&pdu->src_addr, &src_addr);
        
        uint32_t dest_addr;
        inet_addr_pack(&pdu->dest_addr, &dest_addr);
        
        phdr->src_addr = host2uint32_t_be(src_addr);
        phdr->dest_addr = host2uint32_t_be(dest_addr);
        phdr->zero = 0;
        phdr->protocol = 6; /* XXX Magic number */
        phdr->tcp_length = host2uint16_t_be(pdu->header_size + pdu->text_size);
}

static void tcp_header_decode(tcp_header_t *hdr, tcp_segment_t *seg)
{
        tcp_header_decode_flags(uint16_t_be2host(hdr->doff_flags), &seg->ctrl);
        seg->seq = uint32_t_be2host(hdr->seq);
        seg->ack = uint32_t_be2host(hdr->ack);
        seg->wnd = uint16_t_be2host(hdr->window);
        seg->up = uint16_t_be2host(hdr->urg_ptr);
}

static int tcp_header_encode(tcp_sockpair_t *sp, tcp_segment_t *seg,
    void **header, size_t *size)
{
        tcp_header_t *hdr;

        hdr = calloc(1, sizeof(tcp_header_t));
        if (hdr == NULL)
                return ENOMEM;

        tcp_header_setup(sp, seg, hdr);
        *header = hdr;
        *size = sizeof(tcp_header_t);

        return EOK;
}

static tcp_pdu_t *tcp_pdu_new(void)
{
        return calloc(1, sizeof(tcp_pdu_t));
}

/** Create PDU with the specified header and text data.
 *
 * Note that you still need to set addresses in the returned PDU.
 *
 * @param hdr           Header data
 * @param hdr_size      Header size in bytes
 * @param text          Text data
 * @param text_size     Text size in bytes
 * @return              New PDU
 */
tcp_pdu_t *tcp_pdu_create(void *hdr, size_t hdr_size, void *text,
    size_t text_size)
{
        tcp_pdu_t *pdu;

        pdu = tcp_pdu_new();
        if (pdu == NULL)
                return NULL;

        pdu->header = malloc(hdr_size);
        pdu->text = malloc(text_size);
        if (pdu->header == NULL || pdu->text == NULL)
                goto error;

        memcpy(pdu->header, hdr, hdr_size);
        memcpy(pdu->text, text, text_size);

        pdu->header_size = hdr_size;
        pdu->text_size = text_size;

        return pdu;

error:
        if (pdu->header != NULL)
                free(pdu->header);
        if (pdu->text != NULL)
                free(pdu->text);

        return NULL;
}

void tcp_pdu_delete(tcp_pdu_t *pdu)
{
        free(pdu->header);
        free(pdu->text);
        free(pdu);
}

static uint16_t tcp_pdu_checksum_calc(tcp_pdu_t *pdu)
{
        uint16_t cs_phdr;
        uint16_t cs_headers;
        uint16_t cs_all;
        tcp_phdr_t phdr;

        tcp_phdr_setup(pdu, &phdr);
        cs_phdr = tcp_checksum_calc(TCP_CHECKSUM_INIT, (void *)&phdr,
            sizeof(tcp_phdr_t));
        cs_headers = tcp_checksum_calc(cs_phdr, pdu->header, pdu->header_size);
        cs_all = tcp_checksum_calc(cs_headers, pdu->text, pdu->text_size);

        return cs_all;
}

static void tcp_pdu_set_checksum(tcp_pdu_t *pdu, uint16_t checksum)
{
        tcp_header_t *hdr;

        hdr = (tcp_header_t *)pdu->header;
        hdr->checksum = host2uint16_t_be(checksum);
}

/** Decode incoming PDU */
int tcp_pdu_decode(tcp_pdu_t *pdu, tcp_sockpair_t *sp, tcp_segment_t **seg)
{
        tcp_segment_t *nseg;
        tcp_header_t *hdr;

        nseg = tcp_segment_make_data(0, pdu->text, pdu->text_size);
        if (nseg == NULL)
                return ENOMEM;

        tcp_header_decode(pdu->header, nseg);
        nseg->len += seq_no_control_len(nseg->ctrl);

        hdr = (tcp_header_t *)pdu->header;

        sp->local.port = uint16_t_be2host(hdr->dest_port);
        sp->local.addr = pdu->dest_addr;
        sp->foreign.port = uint16_t_be2host(hdr->src_port);
        sp->foreign.addr = pdu->src_addr;

        *seg = nseg;
        return EOK;
}

/** Encode outgoing PDU */
int tcp_pdu_encode(tcp_sockpair_t *sp, tcp_segment_t *seg, tcp_pdu_t **pdu)
{
        tcp_pdu_t *npdu;
        size_t text_size;
        uint16_t checksum;

        npdu = tcp_pdu_new();
        if (npdu == NULL)
                return ENOMEM;

        npdu->src_addr = sp->local.addr;
        npdu->dest_addr = sp->foreign.addr;
        tcp_header_encode(sp, seg, &npdu->header, &npdu->header_size);

        text_size = tcp_segment_text_size(seg);
        npdu->text = calloc(1, text_size);
        if (npdu->text == NULL)
                return ENOMEM;

        npdu->text_size = text_size;
        memcpy(npdu->text, seg->data, text_size);

        /* Checksum calculation */
        checksum = tcp_pdu_checksum_calc(npdu);
        tcp_pdu_set_checksum(npdu, checksum);

        *pdu = npdu;
        return EOK;
}

/**
 * @}
 */