1 /* $OpenBSD: in_cksum.c,v 1.5 2022/02/01 15:30:10 miod Exp $ */
2
3 /*
4 * Copyright (C) 1995, 1996 Wolfgang Solfrank.
5 * Copyright (C) 1995, 1996 TooLs GmbH.
6 * 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. All advertising materials mentioning features or use of this software
17 * must display the following acknowledgement:
18 * This product includes software developed by TooLs GmbH.
19 * 4. The name of TooLs GmbH may not be used to endorse or promote products
20 * derived from this software without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
23 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25 * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
26 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
27 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
28 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
29 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
30 * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
31 * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32 */
33
34 #include <sys/param.h>
35 #include <sys/systm.h>
36 #include <sys/mbuf.h>
37 #include <sys/socketvar.h>
38 #include <netinet/in.h>
39 #include <netinet/ip.h>
40 #include <netinet/ip_var.h>
41
42 #define REDUCE (sum = (sum & 0xffff) + (sum >> 16))
43 #define ROL (sum <<= 8)
44 #define ADDB (ROL, sum += *w, byte_swapped ^= 1)
45 #define ADDS (sum += *(u_short *)w)
46 #define SHIFT(n) (w += (n), mlen -= (n))
47 #define ADDCARRY do { REDUCE; REDUCE; } while (0)
48
49 static __inline__ int
in_cksum_internal(struct mbuf * m,int off,int len,u_int sum)50 in_cksum_internal(struct mbuf *m, int off, int len, u_int sum)
51 {
52 u_char *w;
53 int mlen;
54 int byte_swapped = 0;
55
56 for (; m && len; m = m->m_next) {
57 if (m->m_len == 0)
58 continue;
59 w = mtod(m, u_char *) + off;
60 mlen = m->m_len - off;
61 off = 0;
62 if (len < mlen)
63 mlen = len;
64 len -= mlen;
65
66 if ((long)w & 1) {
67 REDUCE;
68 ADDB;
69 SHIFT(1);
70 }
71 while (mlen >= 2) {
72 ADDS;
73 SHIFT(2);
74 }
75 REDUCE;
76 if (mlen == 1)
77 ADDB;
78 }
79 if (byte_swapped) {
80 REDUCE;
81 ROL;
82 }
83 ADDCARRY;
84 return (0xffff ^ sum);
85 }
86
87 int
in_cksum(struct mbuf * m,int len)88 in_cksum(struct mbuf *m, int len)
89 {
90 return (in_cksum_internal(m, 0, len, 0));
91 }
92
93 int
in4_cksum(struct mbuf * m,uint8_t nxt,int off,int len)94 in4_cksum(struct mbuf *m, uint8_t nxt, int off, int len)
95 {
96 u_int16_t *w;
97 u_int sum = 0;
98 union {
99 struct ipovly ipov;
100 u_int16_t w[10];
101 } u;
102
103 if (nxt != 0) {
104 /* pseudo header */
105 u.ipov.ih_x1[8] = 0;
106 u.ipov.ih_pr = nxt;
107 u.ipov.ih_len = htons(len);
108 u.ipov.ih_src = mtod(m, struct ip *)->ip_src;
109 u.ipov.ih_dst = mtod(m, struct ip *)->ip_dst;
110 w = u.w;
111 /* assumes sizeof(ipov) == 20 and first 8 bytes are zeroes */
112 sum += w[4]; sum += w[5]; sum += w[6];
113 sum += w[7]; sum += w[8]; sum += w[9];
114 }
115
116 /* skip unnecessary part */
117 while (m && off > 0) {
118 if (m->m_len > off)
119 break;
120 off -= m->m_len;
121 m = m->m_next;
122 }
123
124 return (in_cksum_internal(m, off, len, sum));
125 }
126