2 * $Id: libnet_insert_tcpo.c,v 1.1.1.1 2000/05/25 00:28:49 route Exp $
5 * libnet_insert_tcpo.c - inserts TCP options into a prebuilt IP packet
7 * Copyright (c) 1998 - 2001 Mike D. Schiffman <mike@infonexus.com>
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
13 * 1. Redistributions of source code must retain the above copyright
14 * notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in the
17 * documentation and/or other materials provided with the distribution.
19 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 #include "../include/config.h"
36 #include "../include/libnet.h"
39 libnet_insert_tcpo(struct tcpoption *opt, u_char opt_len, u_char *buf)
41 struct libnet_ip_hdr *ip_hdr;
42 struct libnet_tcp_hdr *tcp_hdr;
45 u_char i, opt_padded_len;
46 u_char opt_padded_buf[MAX_IPOPTLEN];
53 ip_hdr = (struct libnet_ip_hdr *)(buf);
55 if (ip_hdr->ip_p != IPPROTO_TCP)
58 * Hey retard, where's the TCP header?
61 libnet_error(LIBNET_ERR_WARNING,
62 "insert_tcpo: tried to insert TCP options into a NON-TCP packet!\n");
67 if (opt_len > MAX_IPOPTLEN)
70 * Hey retard, TCP options can only be 20 octets long!
73 libnet_error(LIBNET_ERR_WARNING,
74 "insert_tcpo: options list too long!\n");
79 s = ntohs(ip_hdr->ip_len);
82 * Figure out length of options with any necessary padding.
86 opt_padded_len = opt_len + 4 - (opt_len % 4);
90 opt_padded_len = opt_len;
93 if ((s + opt_padded_len) > IP_MAXPACKET)
99 libnet_error(LIBNET_ERR_WARNING,
100 "insert_tcpo: options list would result in too large of a packet\n");
107 * Fixed pointer math -- now uses ip_hl instead of IP_H to calculate
110 tcp_hdr = (struct libnet_tcp_hdr *)(buf + (ip_hdr->ip_hl << 2));
113 * Do we have more then just an TCP header? (We are ignoring the IP
114 * header at this point).
116 if (s > (ip_hdr->ip_hl << 2) + LIBNET_TCP_H)
119 * Move over whatever's in the way.
121 memmove((u_char *)tcp_hdr + LIBNET_TCP_H + opt_padded_len,
122 (u_char *)tcp_hdr + LIBNET_TCP_H,
123 (s - (ip_hdr->ip_hl << 2) - LIBNET_TCP_H));
127 * Copy over option list. We rely on the programmer having been
128 * smart enough to allocate enough heap memory here. Uh oh.
130 p = (u_char *)tcp_hdr + LIBNET_TCP_H;
131 memcpy(opt_padded_buf, (u_char *)opt->tcpopt_list, opt_len);
132 memcpy((u_char *)p, opt_padded_buf, opt_padded_len);
135 * Count up number of 32-bit words in options list, padding if
138 for (i = 0, j = 0; i < opt_padded_len; i++) (i % 4) ? j : j++;
140 tcp_hdr->th_off += j;
142 ip_hdr->ip_len = htons(opt_padded_len + s);