1 /*

     2  * Copyright (c) 1988, 1992, 1993

     3  *	The Regents of the University of California.  All rights reserved.

     4  *

     5  * Redistribution and use in source and binary forms, with or without

     6  * modification, are permitted provided that the following conditions

     7  * are met:

     8  * 1. Redistributions of source code must retain the above copyright

     9  *    notice, this list of conditions and the following disclaimer.

    10  * 2. Redistributions in binary form must reproduce the above copyright

    11  *    notice, this list of conditions and the following disclaimer in the

    12  *    documentation and/or other materials provided with the distribution.

    13  * 3. All advertising materials mentioning features or use of this software

    14  *    must display the following acknowledgement:

    15  *	This product includes software developed by the University of

    16  *	California, Berkeley and its contributors.

    17  * 4. Neither the name of the University nor the names of its contributors

    18  *    may be used to endorse or promote products derived from this software

    19  *    without specific prior written permission.

    20  *

    21  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND

    22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

    23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE

    24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE

    25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL

    26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS

    27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)

    28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT

    29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY

    30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

    31  * SUCH DAMAGE.

    32  *

    33  *	@(#)in_cksum.c	8.1 (Berkeley) 6/10/93

    34  * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp

    35  */

    36 

    37 #include <slirp.h>

    38 

    39 /*

    40  * Checksum routine for Internet Protocol family headers (Portable Version).

    41  *

    42  * This routine is very heavily used in the network

    43  * code and should be modified for each CPU to be as fast as possible.

    44  *

    45  * XXX Since we will never span more than 1 mbuf, we can optimise this

    46  */

    47 

    48 #define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)

    49 #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}

    50 

    51 int cksum(struct mbuf *m, int len)

    52 {

    53 	register u_int16_t *w;

    54 	register int sum = 0;

    55 	register int mlen = 0;

    56 	int byte_swapped = 0;

    57 

    58 	union {

    59 		u_int8_t	c[2];

    60 		u_int16_t	s;

    61 	} s_util;

    62 	union {

    63 		u_int16_t s[2];

    64 		u_int32_t l;

    65 	} l_util;

    66 

    67 	if (m->m_len == 0)

    68 	   goto cont;

    69 	w = mtod(m, u_int16_t *);

    70 

    71 	mlen = m->m_len;

    72 

    73 	if (len < mlen)

    74 	   mlen = len;

    75 	len -= mlen;

    76 	/*

    77 	 * Force to even boundary.

    78 	 */

    79 	if ((1 & (long) w) && (mlen > 0)) {

    80 		REDUCE;

    81 		sum <<= 8;

    82 		s_util.c[0] = *(u_int8_t *)w;

    83 		w = (u_int16_t *)((int8_t *)w + 1);

    84 		mlen--;

    85 		byte_swapped = 1;

    86 	}

    87 	/*

    88 	 * Unroll the loop to make overhead from

    89 	 * branches &c small.

    90 	 */

    91 	while ((mlen -= 32) >= 0) {

    92 		sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];

    93 		sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];

    94 		sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];

    95 		sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];

    96 		w += 16;

    97 	}

    98 	mlen += 32;

    99 	while ((mlen -= 8) >= 0) {

   100 		sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];

   101 		w += 4;

   102 	}

   103 	mlen += 8;

   104 	if (mlen == 0 && byte_swapped == 0)

   105 	   goto cont;

   106 	REDUCE;

   107 	while ((mlen -= 2) >= 0) {

   108 		sum += *w++;

   109 	}

   110 

   111 	if (byte_swapped) {

   112 		REDUCE;

   113 		sum <<= 8;

   114 		byte_swapped = 0;

   115 		if (mlen == -1) {

   116 			s_util.c[1] = *(u_int8_t *)w;

   117 			sum += s_util.s;

   118 			mlen = 0;

   119 		} else

   120 

   121 		   mlen = -1;

   122 	} else if (mlen == -1)

   123 	   s_util.c[0] = *(u_int8_t *)w;

   124 

   125 cont:

   126 #ifdef DEBUG

   127 	if (len) {

   128 		DEBUG_ERROR((dfd, "cksum: out of data\n"));

   129 		DEBUG_ERROR((dfd, " len = %d\n", len));

   130 	}

   131 #endif

   132 	if (mlen == -1) {

   133 		/* The last mbuf has odd # of bytes. Follow the

   134 		 standard (the odd byte may be shifted left by 8 bits

   135 			   or not as determined by endian-ness of the machine) */

   136 		s_util.c[1] = 0;

   137 		sum += s_util.s;

   138 	}

   139 	REDUCE;

   140 	return (~sum & 0xffff);

   141 }