/*
* $Id: libnet_build_tcp.c,v 1.11 2004/01/28 19:45:00 mike Exp $
*
* libnet
* libnet_build_tcp.c - TCP packet assembler
*
* Copyright (c) 1998 - 2004 Mike D. Schiffman <mike@infonexus.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
*
*/
#if (HAVE_CONFIG_H)
#include "../include/config.h"
#endif
#if (!(_WIN32) || (__CYGWIN__))
#include "../include/libnet.h"
#else
#include "../include/win32/libnet.h"
#endif
libnet_ptag_t
libnet_build_tcp(
uint16_t sp, uint16_t dp, uint32_t seq, uint32_t ack,
uint8_t control, uint16_t win, uint16_t sum, uint16_t urg, uint16_t h_len,
const uint8_t *payload, uint32_t payload_s, libnet_t *l, libnet_ptag_t ptag)
{
int n, offset;
libnet_pblock_t *p = NULL;
libnet_ptag_t ptag_data = 0;
struct libnet_tcp_hdr tcp_hdr;
if (l == NULL)
return -1;
if (payload_s && !payload)
{
snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,
"%s(): payload inconsistency\n", __func__);
return -1;
}
p = libnet_pblock_probe(l, ptag, LIBNET_TCP_H, LIBNET_PBLOCK_TCP_H);
if (p == NULL)
return -1;
memset(&tcp_hdr, 0, sizeof(tcp_hdr));
tcp_hdr.th_sport = htons(sp); /* source port */
tcp_hdr.th_dport = htons(dp); /* destination port */
tcp_hdr.th_seq = htonl(seq); /* sequence number */
tcp_hdr.th_ack = htonl(ack); /* acknowledgement number */
tcp_hdr.th_flags = control; /* control flags */
tcp_hdr.th_x2 = 0; /* UNUSED */
tcp_hdr.th_off = 5; /* 20 byte header */
/* check to see if there are TCP options to include */
if (p->prev && p->prev->type == LIBNET_PBLOCK_TCPO_H)
{
/* Note that the tcp options pblock is already padded */
tcp_hdr.th_off += (p->prev->b_len/4);
}
tcp_hdr.th_win = htons(win); /* window size */
tcp_hdr.th_sum = (sum ? htons(sum) : 0); /* checksum */
tcp_hdr.th_urp = htons(urg); /* urgent pointer */
n = libnet_pblock_append(l, p, (uint8_t *)&tcp_hdr, LIBNET_TCP_H);
if (n == -1)
{
goto bad;
}
if (ptag == LIBNET_PTAG_INITIALIZER)
{
libnet_pblock_update(l, p, h_len, LIBNET_PBLOCK_TCP_H);
}
offset = payload_s;
/* If we are going to modify a TCP data block, find it, and figure out the
* "offset", the possibly negative amount by which we are increasing the ip
* data length. */
if (ptag)
{
libnet_pblock_t* datablock = p->prev;
if (datablock && datablock->type == LIBNET_PBLOCK_TCPO_H)
datablock = datablock->prev;
if (datablock && datablock->type == LIBNET_PBLOCK_TCPDATA)
{
ptag_data = datablock->ptag;
offset -= datablock->b_len;
}
p->h_len += offset;
}
/* If we are modifying a TCP block, we should look forward and apply the offset
* to our IPv4 header, if we have one.
*/
if (p->next)
{
libnet_pblock_t* ipblock = p->next;
if(ipblock->type == LIBNET_PBLOCK_IPO_H)
ipblock = ipblock->next;
if(ipblock && ipblock->type == LIBNET_PBLOCK_IPV4_H)
{
struct libnet_ipv4_hdr * ip_hdr = (struct libnet_ipv4_hdr *)ipblock->buf;
int ip_len = ntohs(ip_hdr->ip_len) + offset;
ip_hdr->ip_len = htons(ip_len);
}
}
/* if there is a payload, add it in the context */
if (payload_s)
{
/* update ptag_data with the new payload */
libnet_pblock_t* p_data = libnet_pblock_probe(l, ptag_data, payload_s, LIBNET_PBLOCK_TCPDATA);
if (!p_data)
{
goto bad;
}
n = libnet_pblock_append(l, p_data, payload, payload_s);
if (n == -1)
{
goto bad;
}
if (ptag_data == LIBNET_PTAG_INITIALIZER)
{
int insertbefore = p->ptag;
/* Then we created it, and we need to shuffle it back until it's before
* the tcp header and options. */
libnet_pblock_update(l, p_data, payload_s, LIBNET_PBLOCK_TCPDATA);
if(p->prev && p->prev->type == LIBNET_PBLOCK_TCPO_H)
insertbefore = p->prev->ptag;
libnet_pblock_insert_before(l, insertbefore, p_data->ptag);
}
}
else
{
libnet_pblock_t* p_data = libnet_pblock_find(l, ptag_data);
libnet_pblock_delete(l, p_data);
}
if (sum == 0)
{
/*
* If checksum is zero, by default libnet will compute a checksum
* for the user. The programmer can override this by calling
* libnet_toggle_checksum(l, ptag, 1);
*/
libnet_pblock_setflags(p, LIBNET_PBLOCK_DO_CHECKSUM);
}
return (p->ptag);
bad:
libnet_pblock_delete(l, p);
return (-1);
}
libnet_ptag_t
libnet_build_tcp_options(const uint8_t *options, uint32_t options_s, libnet_t *l,
libnet_ptag_t ptag)
{
static const uint8_t padding[] = { 0 };
int n, offset, underflow;
uint32_t i, j, adj_size;
libnet_pblock_t *p, *p_temp;
struct libnet_ipv4_hdr *ip_hdr;
struct libnet_tcp_hdr *tcp_hdr;
if (l == NULL)
{
return (-1);
}
underflow = 0;
offset = 0;
/* check options list size */
if (options_s > LIBNET_MAXOPTION_SIZE)
{
snprintf(l->err_buf, LIBNET_ERRBUF_SIZE,
"%s(): options list is too large %d\n", __func__, options_s);
return (-1);
}
adj_size = options_s;
if (adj_size % 4)
{
/* size of memory block with padding */
adj_size += 4 - (options_s % 4);
}
/* if this pblock already exists, determine if there is a size diff */
if (ptag)
{
p_temp = libnet_pblock_find(l, ptag);
if (p_temp)
{
if (adj_size >= p_temp->b_len)
{
offset = adj_size - p_temp->b_len;
}
else
{
offset = p_temp->b_len - adj_size;
underflow = 1;
}
}
}
/*
* Find the existing protocol block if a ptag is specified, or create
* a new one.
*/
p = libnet_pblock_probe(l, ptag, adj_size, LIBNET_PBLOCK_TCPO_H);
if (p == NULL)
{
return (-1);
}
n = libnet_pblock_append(l, p, options, options_s);
if (n == -1)
{
goto bad;
}
n = libnet_pblock_append(l, p, padding, adj_size - options_s);
if (n == -1)
{
goto bad;
}
if (ptag && p->next)
{
p_temp = p->next;
while ((p_temp->next) && (p_temp->type != LIBNET_PBLOCK_TCP_H))
{
p_temp = p_temp->next;
}
if (p_temp->type == LIBNET_PBLOCK_TCP_H)
{
/*
* Count up number of 32-bit words in options list, padding if
* neccessary.
*/
for (i = 0, j = 0; i < p->b_len; i++)
{
(i % 4) ? j : j++;
}
tcp_hdr = (struct libnet_tcp_hdr *)p_temp->buf;
tcp_hdr->th_off = j + 5;
if (!underflow)
{
p_temp->h_len += offset;
}
else
{
p_temp->h_len -= offset;
}
}
while ((p_temp->next) && (p_temp->type != LIBNET_PBLOCK_IPV4_H))
{
p_temp = p_temp->next;
}
if (p_temp->type == LIBNET_PBLOCK_IPV4_H)
{
ip_hdr = (struct libnet_ipv4_hdr *)p_temp->buf;
if (!underflow)
{
ip_hdr->ip_len += htons(offset);
}
else
{
ip_hdr->ip_len -= htons(offset);
}
}
}
return (ptag ? ptag : libnet_pblock_update(l, p, adj_size,
LIBNET_PBLOCK_TCPO_H));
bad:
libnet_pblock_delete(l, p);
return (-1);
}
/* EOF */