xref: /illumos-gate/usr/src/common/net/dhcp/udp_sum.c (revision 7c478bd9)
1*7c478bd9Sstevel@tonic-gate /*
2*7c478bd9Sstevel@tonic-gate  * CDDL HEADER START
3*7c478bd9Sstevel@tonic-gate  *
4*7c478bd9Sstevel@tonic-gate  * The contents of this file are subject to the terms of the
5*7c478bd9Sstevel@tonic-gate  * Common Development and Distribution License, Version 1.0 only
6*7c478bd9Sstevel@tonic-gate  * (the "License").  You may not use this file except in compliance
7*7c478bd9Sstevel@tonic-gate  * with the License.
8*7c478bd9Sstevel@tonic-gate  *
9*7c478bd9Sstevel@tonic-gate  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
10*7c478bd9Sstevel@tonic-gate  * or http://www.opensolaris.org/os/licensing.
11*7c478bd9Sstevel@tonic-gate  * See the License for the specific language governing permissions
12*7c478bd9Sstevel@tonic-gate  * and limitations under the License.
13*7c478bd9Sstevel@tonic-gate  *
14*7c478bd9Sstevel@tonic-gate  * When distributing Covered Code, include this CDDL HEADER in each
15*7c478bd9Sstevel@tonic-gate  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
16*7c478bd9Sstevel@tonic-gate  * If applicable, add the following below this CDDL HEADER, with the
17*7c478bd9Sstevel@tonic-gate  * fields enclosed by brackets "[]" replaced with your own identifying
18*7c478bd9Sstevel@tonic-gate  * information: Portions Copyright [yyyy] [name of copyright owner]
19*7c478bd9Sstevel@tonic-gate  *
20*7c478bd9Sstevel@tonic-gate  * CDDL HEADER END
21*7c478bd9Sstevel@tonic-gate  */
22*7c478bd9Sstevel@tonic-gate /*
23*7c478bd9Sstevel@tonic-gate  * Copyright (c) 1996-2001 by Sun Microsystems, Inc.
24*7c478bd9Sstevel@tonic-gate  * All rights reserved.
25*7c478bd9Sstevel@tonic-gate  */
26*7c478bd9Sstevel@tonic-gate 
27*7c478bd9Sstevel@tonic-gate #pragma ident	"%Z%%M%	%I%	%E% SMI"
28*7c478bd9Sstevel@tonic-gate 
29*7c478bd9Sstevel@tonic-gate #include <sys/types.h>
30*7c478bd9Sstevel@tonic-gate #include <strings.h>
31*7c478bd9Sstevel@tonic-gate #include <netinet/in.h>
32*7c478bd9Sstevel@tonic-gate #include "v4_sum_impl.h"
33*7c478bd9Sstevel@tonic-gate 
34*7c478bd9Sstevel@tonic-gate /*
35*7c478bd9Sstevel@tonic-gate  * RFC 768 pseudo header. Used in calculating UDP checksums.
36*7c478bd9Sstevel@tonic-gate  */
37*7c478bd9Sstevel@tonic-gate struct pseudo_udp {
38*7c478bd9Sstevel@tonic-gate 	struct in_addr	src;
39*7c478bd9Sstevel@tonic-gate 	struct in_addr	dst;
40*7c478bd9Sstevel@tonic-gate 	uint8_t		notused;	/* always zero */
41*7c478bd9Sstevel@tonic-gate 	uint8_t		proto;		/* protocol used */
42*7c478bd9Sstevel@tonic-gate 	uint16_t	len;		/* UDP len */
43*7c478bd9Sstevel@tonic-gate };
44*7c478bd9Sstevel@tonic-gate 
45*7c478bd9Sstevel@tonic-gate /*
46*7c478bd9Sstevel@tonic-gate  * One's complement checksum of pseudo header, udp header, and data.
47*7c478bd9Sstevel@tonic-gate  * Must be MT SAFE.
48*7c478bd9Sstevel@tonic-gate  */
49*7c478bd9Sstevel@tonic-gate uint16_t
udp_chksum(struct udphdr * udph,const struct in_addr * src,const struct in_addr * dst,uint8_t proto)50*7c478bd9Sstevel@tonic-gate udp_chksum(struct udphdr *udph, const struct in_addr *src,
51*7c478bd9Sstevel@tonic-gate     const struct in_addr *dst, uint8_t proto)
52*7c478bd9Sstevel@tonic-gate {
53*7c478bd9Sstevel@tonic-gate 	struct pseudo_udp	ck;
54*7c478bd9Sstevel@tonic-gate 	uint16_t		*end_pseudo_hdr = (uint16_t *)(&ck + 1);
55*7c478bd9Sstevel@tonic-gate 	uint16_t		*sp = (uint16_t *)&ck;
56*7c478bd9Sstevel@tonic-gate 	uint_t			sum = 0;
57*7c478bd9Sstevel@tonic-gate 	uint16_t		cnt;
58*7c478bd9Sstevel@tonic-gate 
59*7c478bd9Sstevel@tonic-gate 	/*
60*7c478bd9Sstevel@tonic-gate 	 * Start on the pseudo header. Note that pseudo_udp already takes
61*7c478bd9Sstevel@tonic-gate 	 * acount for the udphdr...
62*7c478bd9Sstevel@tonic-gate 	 */
63*7c478bd9Sstevel@tonic-gate 
64*7c478bd9Sstevel@tonic-gate 	bzero(&ck, sizeof (ck));
65*7c478bd9Sstevel@tonic-gate 
66*7c478bd9Sstevel@tonic-gate 	/* struct copies */
67*7c478bd9Sstevel@tonic-gate 	ck.src	 = *src;
68*7c478bd9Sstevel@tonic-gate 	ck.dst	 = *dst;
69*7c478bd9Sstevel@tonic-gate 	ck.len	 = udph->uh_ulen;
70*7c478bd9Sstevel@tonic-gate 	ck.proto = proto;
71*7c478bd9Sstevel@tonic-gate 
72*7c478bd9Sstevel@tonic-gate 	/*
73*7c478bd9Sstevel@tonic-gate 	 * If the packet is an odd length, zero the pad byte for checksum
74*7c478bd9Sstevel@tonic-gate 	 * purposes [doesn't hurt data]
75*7c478bd9Sstevel@tonic-gate 	 */
76*7c478bd9Sstevel@tonic-gate 
77*7c478bd9Sstevel@tonic-gate 	cnt = ntohs(ck.len) + sizeof (ck);
78*7c478bd9Sstevel@tonic-gate 	if (cnt & 1) {
79*7c478bd9Sstevel@tonic-gate 		((caddr_t)udph)[ntohs(udph->uh_ulen)] = '\0';
80*7c478bd9Sstevel@tonic-gate 		cnt++;	/* make even */
81*7c478bd9Sstevel@tonic-gate 	}
82*7c478bd9Sstevel@tonic-gate 
83*7c478bd9Sstevel@tonic-gate 	for (cnt >>= 1; cnt != 0; cnt--) {
84*7c478bd9Sstevel@tonic-gate 
85*7c478bd9Sstevel@tonic-gate 		sum += *sp++;
86*7c478bd9Sstevel@tonic-gate 		if (sum >= BIT_WRAP) {
87*7c478bd9Sstevel@tonic-gate 			/* Wrap carries into low bit */
88*7c478bd9Sstevel@tonic-gate 			sum -= BIT_WRAP;
89*7c478bd9Sstevel@tonic-gate 			sum++;
90*7c478bd9Sstevel@tonic-gate 		}
91*7c478bd9Sstevel@tonic-gate 
92*7c478bd9Sstevel@tonic-gate 		/*
93*7c478bd9Sstevel@tonic-gate 		 * If we've finished checking the pseudo-header, move
94*7c478bd9Sstevel@tonic-gate 		 * onto the udp header and data.
95*7c478bd9Sstevel@tonic-gate 		 */
96*7c478bd9Sstevel@tonic-gate 
97*7c478bd9Sstevel@tonic-gate 		if (sp == end_pseudo_hdr)
98*7c478bd9Sstevel@tonic-gate 			sp = (uint16_t *)udph;
99*7c478bd9Sstevel@tonic-gate 	}
100*7c478bd9Sstevel@tonic-gate 
101*7c478bd9Sstevel@tonic-gate 	return (~sum == 0 ? ~0 : ~sum);
102*7c478bd9Sstevel@tonic-gate }
103