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. Neither the name of the University nor the names of its contributors
14 *    may be used to endorse or promote products derived from this software
15 *    without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 *	@(#)in_cksum.c	8.1 (Berkeley) 6/10/93
30 * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
31 */
32
33#include <slirp.h>
34
35/*
36 * Checksum routine for Internet Protocol family headers (Portable Version).
37 *
38 * This routine is very heavily used in the network
39 * code and should be modified for each CPU to be as fast as possible.
40 *
41 * XXX Since we will never span more than 1 mbuf, we can optimise this
42 */
43
44#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
45#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
46
47int cksum(struct mbuf *m, int len)
48{
49	register u_int16_t *w;
50	register int sum = 0;
51	register int mlen = 0;
52	int byte_swapped = 0;
53
54	union {
55		u_int8_t	c[2];
56		u_int16_t	s;
57	} s_util;
58	union {
59		u_int16_t s[2];
60		u_int32_t l;
61	} l_util;
62
63	if (m->m_len == 0)
64	   goto cont;
65	w = mtod(m, u_int16_t *);
66
67	mlen = m->m_len;
68
69	if (len < mlen)
70	   mlen = len;
71	len -= mlen;
72	/*
73	 * Force to even boundary.
74	 */
75	if ((1 & (long) w) && (mlen > 0)) {
76		REDUCE;
77		sum <<= 8;
78		s_util.c[0] = *(u_int8_t *)w;
79		w = (u_int16_t *)((int8_t *)w + 1);
80		mlen--;
81		byte_swapped = 1;
82	}
83	/*
84	 * Unroll the loop to make overhead from
85	 * branches &c small.
86	 */
87	while ((mlen -= 32) >= 0) {
88		sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
89		sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
90		sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
91		sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
92		w += 16;
93	}
94	mlen += 32;
95	while ((mlen -= 8) >= 0) {
96		sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
97		w += 4;
98	}
99	mlen += 8;
100	if (mlen == 0 && byte_swapped == 0)
101	   goto cont;
102	REDUCE;
103	while ((mlen -= 2) >= 0) {
104		sum += *w++;
105	}
106
107	if (byte_swapped) {
108		REDUCE;
109		sum <<= 8;
110		byte_swapped = 0;
111		if (mlen == -1) {
112			s_util.c[1] = *(u_int8_t *)w;
113			sum += s_util.s;
114			mlen = 0;
115		} else
116
117		   mlen = -1;
118	} else if (mlen == -1)
119	   s_util.c[0] = *(u_int8_t *)w;
120
121cont:
122#ifdef DEBUG
123	if (len) {
124		DEBUG_ERROR((dfd, "cksum: out of data\n"));
125		DEBUG_ERROR((dfd, " len = %d\n", len));
126	}
127#endif
128	if (mlen == -1) {
129		/* The last mbuf has odd # of bytes. Follow the
130		 standard (the odd byte may be shifted left by 8 bits
131			   or not as determined by endian-ness of the machine) */
132		s_util.c[1] = 0;
133		sum += s_util.s;
134	}
135	REDUCE;
136	return (~sum & 0xffff);
137}
138