170 lines
4.4 KiB
C
170 lines
4.4 KiB
C
/*-
|
|
* Copyright (c) 2001 Charles Mott <cm@linktel.net>
|
|
* 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.
|
|
*/
|
|
|
|
#include <sys/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
|
|
/*
|
|
Alias_util.c contains general utilities used by other functions
|
|
in the packet aliasing module. At the moment, there are functions
|
|
for computing IP header and TCP packet checksums.
|
|
|
|
The checksum routines are based upon example code in a Unix networking
|
|
text written by Stevens (sorry, I can't remember the title -- but
|
|
at least this is a good author).
|
|
|
|
Initial Version: August, 1996 (cjm)
|
|
|
|
Version 1.7: January 9, 1997
|
|
Added differential checksum update function.
|
|
*/
|
|
|
|
/*
|
|
Note: the checksum routines assume that the actual checksum word has
|
|
been zeroed out. If the checksum word is filled with the proper value,
|
|
then these routines will give a result of zero (useful for testing
|
|
purposes);
|
|
*/
|
|
|
|
#include <sys/types.h>
|
|
#include <netinet/in_systm.h>
|
|
#include <netinet/in.h>
|
|
#include <netinet/ip.h>
|
|
#include <netinet/tcp.h>
|
|
|
|
#include "alias.h"
|
|
#include "alias_local.h"
|
|
|
|
u_short
|
|
PacketAliasInternetChecksum(u_short *ptr, int nbytes)
|
|
{
|
|
int sum, oddbyte;
|
|
|
|
sum = 0;
|
|
while (nbytes > 1)
|
|
{
|
|
sum += *ptr++;
|
|
nbytes -= 2;
|
|
}
|
|
if (nbytes == 1)
|
|
{
|
|
oddbyte = 0;
|
|
((u_char *) &oddbyte)[0] = *(u_char *) ptr;
|
|
((u_char *) &oddbyte)[1] = 0;
|
|
sum += oddbyte;
|
|
}
|
|
sum = (sum >> 16) + (sum & 0xffff);
|
|
sum += (sum >> 16);
|
|
return(~sum);
|
|
}
|
|
|
|
u_short
|
|
IpChecksum(struct ip *pip)
|
|
{
|
|
return( PacketAliasInternetChecksum((u_short *) pip,
|
|
(pip->ip_hl << 2)) );
|
|
|
|
}
|
|
|
|
u_short
|
|
TcpChecksum(struct ip *pip)
|
|
{
|
|
u_short *ptr;
|
|
struct tcphdr *tc;
|
|
int nhdr, ntcp, nbytes;
|
|
int sum, oddbyte;
|
|
|
|
nhdr = pip->ip_hl << 2;
|
|
ntcp = ntohs(pip->ip_len) - nhdr;
|
|
|
|
tc = (struct tcphdr *) ((char *) pip + nhdr);
|
|
ptr = (u_short *) tc;
|
|
|
|
/* Add up TCP header and data */
|
|
nbytes = ntcp;
|
|
sum = 0;
|
|
while (nbytes > 1)
|
|
{
|
|
sum += *ptr++;
|
|
nbytes -= 2;
|
|
}
|
|
if (nbytes == 1)
|
|
{
|
|
oddbyte = 0;
|
|
((u_char *) &oddbyte)[0] = *(u_char *) ptr;
|
|
((u_char *) &oddbyte)[1] = 0;
|
|
sum += oddbyte;
|
|
}
|
|
|
|
/* "Pseudo-header" data */
|
|
ptr = (u_short *) &(pip->ip_dst);
|
|
sum += *ptr++;
|
|
sum += *ptr;
|
|
ptr = (u_short *) &(pip->ip_src);
|
|
sum += *ptr++;
|
|
sum += *ptr;
|
|
sum += htons((u_short) ntcp);
|
|
sum += htons((u_short) pip->ip_p);
|
|
|
|
/* Roll over carry bits */
|
|
sum = (sum >> 16) + (sum & 0xffff);
|
|
sum += (sum >> 16);
|
|
|
|
/* Return checksum */
|
|
return((u_short) ~sum);
|
|
}
|
|
|
|
|
|
void
|
|
DifferentialChecksum(u_short *cksum, u_short *new, u_short *old, int n)
|
|
{
|
|
int i;
|
|
int accumulate;
|
|
|
|
accumulate = *cksum;
|
|
for (i=0; i<n; i++)
|
|
{
|
|
accumulate -= *new++;
|
|
accumulate += *old++;
|
|
}
|
|
|
|
if (accumulate < 0)
|
|
{
|
|
accumulate = -accumulate;
|
|
accumulate = (accumulate >> 16) + (accumulate & 0xffff);
|
|
accumulate += accumulate >> 16;
|
|
*cksum = (u_short) ~accumulate;
|
|
}
|
|
else
|
|
{
|
|
accumulate = (accumulate >> 16) + (accumulate & 0xffff);
|
|
accumulate += accumulate >> 16;
|
|
*cksum = (u_short) accumulate;
|
|
}
|
|
}
|
|
|