File:  [Qemu by Fabrice Bellard] / qemu / slirp / cksum.c
Revision 1.1.1.2 (vendor branch): download - view: text, annotated - select for diffs
Tue Apr 24 16:49:24 2018 UTC (3 years, 1 month ago) by root
Branches: qemu, MAIN
CVS tags: qemu0091, HEAD
qemu 0.9.1

    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: }

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