sctp_crc32.c revision 211969 
1/*-
2 * Copyright (c) 2001-2007, by Cisco Systems, Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are met:
6 *
7 * a) Redistributions of source code must retain the above copyright notice,
8 *   this list of conditions and the following disclaimer.
9 *
10 * b) Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *   the documentation and/or other materials provided with the distribution.
13 *
14 * c) Neither the name of Cisco Systems, Inc. nor the names of its
15 *    contributors may be used to endorse or promote products derived
16 *    from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
20 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
21 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
22 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
23 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
24 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
25 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
26 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
27 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
28 * THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31/* $KAME: sctp_crc32.c,v 1.12 2005/03/06 16:04:17 itojun Exp $	 */
32
33
34#include <sys/cdefs.h>
35__FBSDID("$FreeBSD: head/sys/netinet/sctp_crc32.c 211969 2010-08-29 18:50:30Z tuexen $");
36
37#include <netinet/sctp_os.h>
38#include <netinet/sctp.h>
39#include <netinet/sctp_crc32.h>
40#include <netinet/sctp_pcb.h>
41
42
43#if !defined(SCTP_WITH_NO_CSUM)
44
45static uint32_t
46sctp_finalize_crc32c(uint32_t crc32c)
47{
48	uint32_t result;
49
50#if BYTE_ORDER == BIG_ENDIAN
51	uint8_t byte0, byte1, byte2, byte3;
52
53#endif
54	/* Complement the result */
55	result = ~crc32c;
56#if BYTE_ORDER == BIG_ENDIAN
57	/*
58	 * For BIG-ENDIAN.. aka Motorola byte order the result is in
59	 * little-endian form. So we must manually swap the bytes. Then we
60	 * can call htonl() which does nothing...
61	 */
62	byte0 = result & 0x000000ff;
63	byte1 = (result >> 8) & 0x000000ff;
64	byte2 = (result >> 16) & 0x000000ff;
65	byte3 = (result >> 24) & 0x000000ff;
66	crc32c = ((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
67#else
68	/*
69	 * For INTEL platforms the result comes out in network order. No
70	 * htonl is required or the swap above. So we optimize out both the
71	 * htonl and the manual swap above.
72	 */
73	crc32c = result;
74#endif
75	return (crc32c);
76}
77
78uint32_t
79sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
80{
81	/*
82	 * given a mbuf chain with a packetheader offset by 'offset'
83	 * pointing at a sctphdr (with csum set to 0) go through the chain
84	 * of SCTP_BUF_NEXT()'s and calculate the SCTP checksum. This also
85	 * has a side bonus as it will calculate the total length of the
86	 * mbuf chain. Note: if offset is greater than the total mbuf
87	 * length, checksum=1, pktlen=0 is returned (ie. no real error code)
88	 */
89	uint32_t base = 0xffffffff;
90	struct mbuf *at;
91
92	at = m;
93	/* find the correct mbuf and offset into mbuf */
94	while ((at != NULL) && (offset > (uint32_t) SCTP_BUF_LEN(at))) {
95		offset -= SCTP_BUF_LEN(at);	/* update remaining offset
96						 * left */
97		at = SCTP_BUF_NEXT(at);
98	}
99	while (at != NULL) {
100		if ((SCTP_BUF_LEN(at) - offset) > 0) {
101			base = calculate_crc32c(base,
102			    (unsigned char *)(SCTP_BUF_AT(at, offset)),
103			    (unsigned int)(SCTP_BUF_LEN(at) - offset));
104		}
105		if (offset) {
106			/* we only offset once into the first mbuf */
107			if (offset < (uint32_t) SCTP_BUF_LEN(at))
108				offset = 0;
109			else
110				offset -= SCTP_BUF_LEN(at);
111		}
112		at = SCTP_BUF_NEXT(at);
113	}
114	base = sctp_finalize_crc32c(base);
115	return (base);
116}
117
118#endif				/* !defined(SCTP_WITH_NO_CSUM) */
119
120
121void
122sctp_delayed_cksum(struct mbuf *m, uint32_t offset)
123{
124#if defined(SCTP_WITH_NO_CSUM)
125	panic("sctp_delayed_cksum() called when using no SCTP CRC.");
126#else
127	struct ip *ip;
128	uint32_t checksum;
129
130	ip = mtod(m, struct ip *);
131	checksum = sctp_calculate_cksum(m, offset);
132	SCTP_STAT_DECR(sctps_sendhwcrc);
133	SCTP_STAT_INCR(sctps_sendswcrc);
134	offset += offsetof(struct sctphdr, checksum);
135
136	if (offset + sizeof(uint32_t) > (uint32_t) (m->m_len)) {
137		printf("delayed m_pullup, m->len: %d  off: %d  p: %d\n",
138		    (uint32_t) m->m_len, offset, ip->ip_p);
139		/*
140		 * XXX this shouldn't happen, but if it does, the correct
141		 * behavior may be to insert the checksum in the appropriate
142		 * next mbuf in the chain.
143		 */
144		return;
145	}
146	*(uint32_t *) (m->m_data + offset) = checksum;
147#endif
148}
149