sctp_crc32.c revision 191845 
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 191845 2009-05-06 08:49:39Z zec $");
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#if !defined(SCTP_WITH_NO_CSUM)
43
44static uint32_t
45sctp_finalize_crc32c(uint32_t crc32c)
46{
47	uint32_t result;
48
49#if BYTE_ORDER == BIG_ENDIAN
50	uint8_t byte0, byte1, byte2, byte3;
51
52#endif
53	/* Complement the result */
54	result = ~crc32c;
55#if BYTE_ORDER == BIG_ENDIAN
56	/*
57	 * For BIG-ENDIAN.. aka Motorola byte order the result is in
58	 * little-endian form. So we must manually swap the bytes. Then we
59	 * can call htonl() which does nothing...
60	 */
61	byte0 = result & 0x000000ff;
62	byte1 = (result >> 8) & 0x000000ff;
63	byte2 = (result >> 16) & 0x000000ff;
64	byte3 = (result >> 24) & 0x000000ff;
65	crc32c = ((byte0 << 24) | (byte1 << 16) | (byte2 << 8) | byte3);
66#else
67	/*
68	 * For INTEL platforms the result comes out in network order. No
69	 * htonl is required or the swap above. So we optimize out both the
70	 * htonl and the manual swap above.
71	 */
72	crc32c = result;
73#endif
74	return (crc32c);
75}
76
77uint32_t
78sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
79{
80	/*
81	 * given a mbuf chain with a packetheader offset by 'offset'
82	 * pointing at a sctphdr (with csum set to 0) go through the chain
83	 * of SCTP_BUF_NEXT()'s and calculate the SCTP checksum. This also
84	 * has a side bonus as it will calculate the total length of the
85	 * mbuf chain. Note: if offset is greater than the total mbuf
86	 * length, checksum=1, pktlen=0 is returned (ie. no real error code)
87	 */
88	uint32_t base = 0xffffffff;
89	struct mbuf *at;
90
91	at = m;
92	/* find the correct mbuf and offset into mbuf */
93	while ((at != NULL) && (offset > (uint32_t) SCTP_BUF_LEN(at))) {
94		offset -= SCTP_BUF_LEN(at);	/* update remaining offset
95						 * left */
96		at = SCTP_BUF_NEXT(at);
97	}
98	while (at != NULL) {
99		if ((SCTP_BUF_LEN(at) - offset) > 0) {
100			base = calculate_crc32c(base,
101			    (unsigned char *)(SCTP_BUF_AT(at, offset)),
102			    (unsigned int)(SCTP_BUF_LEN(at) - offset));
103		}
104		if (offset) {
105			/* we only offset once into the first mbuf */
106			if (offset < (uint32_t) SCTP_BUF_LEN(at))
107				offset = 0;
108			else
109				offset -= SCTP_BUF_LEN(at);
110		}
111		at = SCTP_BUF_NEXT(at);
112	}
113	base = sctp_finalize_crc32c(base);
114	return (base);
115}
116
117#else
118
119uint32_t
120sctp_calculate_cksum(struct mbuf *m, uint32_t offset)
121{
122	return (0);
123}
124
125#endif				/* !defined(SCTP_WITH_NO_CSUM) */
126
127
128void
129sctp_delayed_cksum(struct mbuf *m)
130{
131	struct ip *ip;
132	uint32_t checksum;
133	uint32_t offset;
134
135	ip = mtod(m, struct ip *);
136	offset = ip->ip_hl << 2;
137	checksum = sctp_calculate_cksum(m, offset);
138	SCTP_STAT_DECR(sctps_sendhwcrc);
139	SCTP_STAT_INCR(sctps_sendswcrc);
140	offset += offsetof(struct sctphdr, checksum);
141
142	if (offset + sizeof(uint32_t) > (uint32_t) (m->m_len)) {
143		printf("delayed m_pullup, m->len: %d  off: %d  p: %d\n",
144		    (uint32_t) m->m_len, offset, ip->ip_p);
145		/*
146		 * XXX this shouldn't happen, but if it does, the correct
147		 * behavior may be to insert the checksum in the appropriate
148		 * next mbuf in the chain.
149		 */
150		return;
151	}
152	*(uint32_t *) (m->m_data + offset) = checksum;
153}
154