1/*	$OpenBSD: in_cksum.c,v 1.9 2019/04/22 22:47:49 bluhm Exp $	*/
2/*	$NetBSD: in_cksum.c,v 1.11 1996/04/08 19:55:37 jonathan Exp $	*/
3
4/*
5 * Copyright (c) 1988, 1992, 1993
6 *	The Regents of the University of California.  All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 *
32 *	@(#)in_cksum.c	8.1 (Berkeley) 6/10/93
33 */
34
35#include <sys/param.h>
36#include <sys/mbuf.h>
37#include <sys/systm.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
46#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
47#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
48
49int
50in_cksum(struct mbuf *m, int len)
51{
52	uint16_t *w;
53	int sum = 0;
54	int mlen = 0;
55	int byte_swapped = 0;
56	union {
57		uint8_t  c[2];
58		uint16_t s;
59	} s_util;
60	union {
61		uint16_t s[2];
62		uint32_t l;
63	} l_util;
64
65	for (;m && len; m = m->m_next) {
66		if (m->m_len == 0)
67			continue;
68		w = mtod(m, uint16_t *);
69		if (mlen == -1) {
70			/*
71			 * The first byte of this mbuf is the continuation
72			 * of a word spanning between this mbuf and the
73			 * last mbuf.
74			 *
75			 * s_util.c[0] is already saved when scanning previous
76			 * mbuf.
77			 */
78			s_util.c[1] = *(uint8_t *)w;
79			sum += s_util.s;
80			w = (uint16_t *)((uint8_t *)w + 1);
81			mlen = m->m_len - 1;
82			len--;
83		} else
84			mlen = m->m_len;
85		if (len < mlen)
86			mlen = len;
87		len -= mlen;
88		/*
89		 * Force to even boundary.
90		 */
91		if ((1 & (long) w) && (mlen > 0)) {
92			REDUCE;
93			sum <<= 8;
94			s_util.c[0] = *(uint8_t *)w;
95			w = (uint16_t *)((uint8_t *)w + 1);
96			mlen--;
97			byte_swapped = 1;
98		}
99		/*
100		 * Unroll the loop to make overhead from
101		 * branches &c small.
102		 */
103		while ((mlen -= 32) >= 0) {
104			sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
105			sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
106			sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
107			sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
108			w += 16;
109		}
110		mlen += 32;
111		while ((mlen -= 8) >= 0) {
112			sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
113			w += 4;
114		}
115		mlen += 8;
116		if (mlen == 0 && byte_swapped == 0)
117			continue;
118		REDUCE;
119		while ((mlen -= 2) >= 0) {
120			sum += *w++;
121		}
122		if (byte_swapped) {
123			REDUCE;
124			sum <<= 8;
125			byte_swapped = 0;
126			if (mlen == -1) {
127				s_util.c[1] = *(uint8_t *)w;
128				sum += s_util.s;
129				mlen = 0;
130			} else
131				mlen = -1;
132		} else if (mlen == -1)
133			s_util.c[0] = *(uint8_t *)w;
134	}
135	if (len)
136		panic("%s: out of data, len %d", __func__, len);
137	if (mlen == -1) {
138		/* The last mbuf has odd # of bytes. Follow the
139		   standard (the odd byte may be shifted left by 8 bits
140		   or not as determined by endian-ness of the machine) */
141		s_util.c[1] = 0;
142		sum += s_util.s;
143	}
144	REDUCE;
145	return (~sum & 0xffff);
146}
147