1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License, Version 1.0 only
6 * (the "License"). You may not use this file except in compliance
7 * with the License.
8 *
9 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10 * or http://www.opensolaris.org/os/licensing.
11 * See the License for the specific language governing permissions
12 * and limitations under the License.
13 *
14 * When distributing Covered Code, include this CDDL HEADER in each
15 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16 * If applicable, add the following below this CDDL HEADER, with the
17 * fields enclosed by brackets "[]" replaced with your own identifying
18 * information: Portions Copyright [yyyy] [name of copyright owner]
19 *
20 * CDDL HEADER END
21 */
22 /*
23 * Copyright (c) 1996-2001 by Sun Microsystems, Inc.
24 * All rights reserved.
25 */
26
27 #pragma ident "%Z%%M% %I% %E% SMI"
28
29 #include <sys/types.h>
30 #include <strings.h>
31 #include <netinet/in.h>
32 #include "v4_sum_impl.h"
33
34 /*
35 * RFC 768 pseudo header. Used in calculating UDP checksums.
36 */
37 struct pseudo_udp {
38 struct in_addr src;
39 struct in_addr dst;
40 uint8_t notused; /* always zero */
41 uint8_t proto; /* protocol used */
42 uint16_t len; /* UDP len */
43 };
44
45 /*
46 * One's complement checksum of pseudo header, udp header, and data.
47 * Must be MT SAFE.
48 */
49 uint16_t
udp_chksum(struct udphdr * udph,const struct in_addr * src,const struct in_addr * dst,uint8_t proto)50 udp_chksum(struct udphdr *udph, const struct in_addr *src,
51 const struct in_addr *dst, uint8_t proto)
52 {
53 struct pseudo_udp ck;
54 uint16_t *end_pseudo_hdr = (uint16_t *)(&ck + 1);
55 uint16_t *sp = (uint16_t *)&ck;
56 uint_t sum = 0;
57 uint16_t cnt;
58
59 /*
60 * Start on the pseudo header. Note that pseudo_udp already takes
61 * acount for the udphdr...
62 */
63
64 bzero(&ck, sizeof (ck));
65
66 /* struct copies */
67 ck.src = *src;
68 ck.dst = *dst;
69 ck.len = udph->uh_ulen;
70 ck.proto = proto;
71
72 /*
73 * If the packet is an odd length, zero the pad byte for checksum
74 * purposes [doesn't hurt data]
75 */
76
77 cnt = ntohs(ck.len) + sizeof (ck);
78 if (cnt & 1) {
79 ((caddr_t)udph)[ntohs(udph->uh_ulen)] = '\0';
80 cnt++; /* make even */
81 }
82
83 for (cnt >>= 1; cnt != 0; cnt--) {
84
85 sum += *sp++;
86 if (sum >= BIT_WRAP) {
87 /* Wrap carries into low bit */
88 sum -= BIT_WRAP;
89 sum++;
90 }
91
92 /*
93 * If we've finished checking the pseudo-header, move
94 * onto the udp header and data.
95 */
96
97 if (sp == end_pseudo_hdr)
98 sp = (uint16_t *)udph;
99 }
100
101 return (~sum == 0 ? ~0 : ~sum);
102 }
103