alias_util.c

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    1 /*-
    2  * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
    3  *
    4  * Copyright (c) 2001 Charles Mott <cm@linktel.net>
    5  * All rights reserved.
    6  *
    7  * Redistribution and use in source and binary forms, with or without
    8  * modification, are permitted provided that the following conditions
    9  * are met:
   10  * 1. Redistributions of source code must retain the above copyright
   11  *    notice, this list of conditions and the following disclaimer.
   12  * 2. Redistributions in binary form must reproduce the above copyright
   13  *    notice, this list of conditions and the following disclaimer in the
   14  *    documentation and/or other materials provided with the distribution.
   15  *
   16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
   17  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
   18  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
   19  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
   20  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   21  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   22  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   23  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   24  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
   25  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   26  * SUCH DAMAGE.
   27  */
   28 
   29 #include <sys/cdefs.h>
   30 __FBSDID("$FreeBSD$");
   31 
   32 /*
   33     Alias_util.c contains general utilities used by other functions
   34     in the packet aliasing module.  At the moment, there are functions
   35     for computing IP header and TCP packet checksums.
   36 
   37     The checksum routines are based upon example code in a Unix networking
   38     text written by Stevens (sorry, I can't remember the title -- but
   39     at least this is a good author).
   40 
   41     Initial Version:  August, 1996  (cjm)
   42 
   43     Version 1.7:  January 9, 1997
   44          Added differential checksum update function.
   45 */
   46 
   47 #ifdef _KERNEL
   48 #include <sys/param.h>
   49 #include <sys/proc.h>
   50 #else
   51 #include <sys/types.h>
   52 #include <stdio.h>
   53 #endif
   54 
   55 #include <netinet/in_systm.h>
   56 #include <netinet/in.h>
   57 #include <netinet/ip.h>
   58 #include <netinet/tcp.h>
   59 
   60 #ifdef _KERNEL
   61 #include <netinet/libalias/alias.h>
   62 #include <netinet/libalias/alias_local.h>
   63 #else
   64 #include "alias.h"
   65 #include "alias_local.h"
   66 #endif
   67 
   68 /*
   69  * Note: the checksum routines assume that the actual checksum word has
   70  * been zeroed out.  If the checksum word is filled with the proper value,
   71  * then these routines will give a result of zero (useful for testing
   72  * purposes);
   73  */
   74 u_short
   75 LibAliasInternetChecksum(struct libalias *la __unused, u_short *ptr,
   76     int nbytes)
   77 {
   78         int sum, oddbyte;
   79 
   80         LIBALIAS_LOCK(la);
   81         sum = 0;
   82         while (nbytes > 1) {
   83                 sum += *ptr++;
   84                 nbytes -= 2;
   85         }
   86         if (nbytes == 1) {
   87                 oddbyte = 0;
   88                 ((u_char *)&oddbyte)[0] = *(u_char *)ptr;
   89                 ((u_char *)&oddbyte)[1] = 0;
   90                 sum += oddbyte;
   91         }
   92         sum = (sum >> 16) + (sum & 0xffff);
   93         sum += (sum >> 16);
   94         LIBALIAS_UNLOCK(la);
   95         return (~sum);
   96 }
   97 
   98 #ifndef _KERNEL
   99 u_short
  100 IpChecksum(struct ip *pip)
  101 {
  102         return (LibAliasInternetChecksum(NULL, (u_short *)pip,
  103             (pip->ip_hl << 2)));
  104 
  105 }
  106 
  107 u_short
  108 TcpChecksum(struct ip *pip)
  109 {
  110         u_short *ptr;
  111         struct tcphdr *tc;
  112         int nhdr, ntcp, nbytes;
  113         int sum, oddbyte;
  114 
  115         nhdr = pip->ip_hl << 2;
  116         ntcp = ntohs(pip->ip_len) - nhdr;
  117 
  118         tc = (struct tcphdr *)ip_next(pip);
  119         ptr = (u_short *)tc;
  120 
  121 /* Add up TCP header and data */
  122         nbytes = ntcp;
  123         sum = 0;
  124         while (nbytes > 1) {
  125                 sum += *ptr++;
  126                 nbytes -= 2;
  127         }
  128         if (nbytes == 1) {
  129                 oddbyte = 0;
  130                 ((u_char *)&oddbyte)[0] = *(u_char *)ptr;
  131                 ((u_char *)&oddbyte)[1] = 0;
  132                 sum += oddbyte;
  133         }
  134 /* "Pseudo-header" data */
  135         ptr = (void *)&pip->ip_dst;
  136         sum += *ptr++;
  137         sum += *ptr;
  138         ptr = (void *)&pip->ip_src;
  139         sum += *ptr++;
  140         sum += *ptr;
  141         sum += htons((u_short)ntcp);
  142         sum += htons((u_short)pip->ip_p);
  143 
  144 /* Roll over carry bits */
  145         sum = (sum >> 16) + (sum & 0xffff);
  146         sum += (sum >> 16);
  147 
  148 /* Return checksum */
  149         return ((u_short)~sum);
  150 }
  151 #endif  /* not _KERNEL */
  152 
  153 void
  154 DifferentialChecksum(u_short *cksum, void *newp, void *oldp, int n)
  155 {
  156         int i;
  157         int accumulate;
  158         u_short *new = newp;
  159         u_short *old = oldp;
  160 
  161         accumulate = *cksum;
  162         for (i = 0; i < n; i++) {
  163                 accumulate -= *new++;
  164                 accumulate += *old++;
  165         }
  166 
  167         if (accumulate < 0) {
  168                 accumulate = -accumulate;
  169                 accumulate = (accumulate >> 16) + (accumulate & 0xffff);
  170                 accumulate += accumulate >> 16;
  171                 *cksum = (u_short)~accumulate;
  172         } else {
  173                 accumulate = (accumulate >> 16) + (accumulate & 0xffff);
  174                 accumulate += accumulate >> 16;
  175                 *cksum = (u_short)accumulate;
  176         }
  177 }

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FreeBSD/Linux Kernel Cross Reference sys/netinet/libalias/alias_util.c

FreeBSD/Linux Kernel Cross Reference
sys/netinet/libalias/alias_util.c