src/slirp/cksum.c

/*
 * Copyright (c) 1988, 1992, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)in_cksum.c  8.1 (Berkeley) 6/10/93
 * in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
 */

#include <slirp.h>

/*
 * Checksum routine for Internet Protocol family headers (Portable Version).
 *
 * This routine is very heavily used in the network
 * code and should be modified for each CPU to be as fast as possible.
 * 
 * XXX Since we will never span more than 1 mbuf, we can optimise this
 */

#define ADDCARRY(x)  (x > 65535 ? x -= 65535 : x)
#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}

int cksum(struct mbuf *m, int len)
{
        register u_int16_t *w;
        register int sum = 0;
        register int mlen = 0;
        int byte_swapped = 0;

        union {
                u_int8_t        c[2];
                u_int16_t       s;
        } s_util;
        union {
                u_int16_t s[2];
                u_int32_t l;
        } l_util;
        
        if (m->m_len == 0)
           goto cont;
        w = mtod(m, u_int16_t *);
        
        mlen = m->m_len;
        
        if (len < mlen)
           mlen = len;
        len -= mlen;
        /*
         * Force to even boundary.
         */
        if ((1 & (long) w) && (mlen > 0)) {
                REDUCE;
                sum <<= 8;
                s_util.c[0] = *(u_int8_t *)w;
                w = (u_int16_t *)((int8_t *)w + 1);
                mlen--;
                byte_swapped = 1;
        }
        /*
         * Unroll the loop to make overhead from
         * branches &c small.
         */
        while ((mlen -= 32) >= 0) {
                sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
                sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
                sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
                sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
                w += 16;
        }
        mlen += 32;
        while ((mlen -= 8) >= 0) {
                sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
                w += 4;
        }
        mlen += 8;
        if (mlen == 0 && byte_swapped == 0)
           goto cont;
        REDUCE;
        while ((mlen -= 2) >= 0) {
                sum += *w++;
        }
        
        if (byte_swapped) {
                REDUCE;
                sum <<= 8;
                byte_swapped = 0;
                if (mlen == -1) {
                        s_util.c[1] = *(u_int8_t *)w;
                        sum += s_util.s;
                        mlen = 0;
                } else
                   
                   mlen = -1;
        } else if (mlen == -1)
           s_util.c[0] = *(u_int8_t *)w;
        
cont:
#ifdef DEBUG
        if (len) {
                DEBUG_ERROR((dfd, "cksum: out of data\n"));
                DEBUG_ERROR((dfd, " len = %d\n", len));
        }
#endif
        if (mlen == -1) {
                /* The last mbuf has odd # of bytes. Follow the
                 standard (the odd byte may be shifted left by 8 bits
                           or not as determined by endian-ness of the machine) */
                s_util.c[1] = 0;
                sum += s_util.s;
        }
        REDUCE;
        return (~sum & 0xffff);
}
Revision:	1.1
Committed:	2005-05-13T09:00:59Z (19 years, 6 months ago) by gbeauche
Content type:	text/plain
Branch:	MAIN
CVS Tags:	nigel-build-19, nigel-build-17
Log Message:	slirp user mode network emulation code from qemu
#	Content
1	/*
2	* Copyright (c) 1988, 1992, 1993
3	* The Regents of the University of California. All rights reserved.
4	*
5	* Redistribution and use in source and binary forms, with or without
6	* modification, are permitted provided that the following conditions
7	* are met:
8	* 1. Redistributions of source code must retain the above copyright
9	* notice, this list of conditions and the following disclaimer.
10	* 2. Redistributions in binary form must reproduce the above copyright
11	* notice, this list of conditions and the following disclaimer in the
12	* documentation and/or other materials provided with the distribution.
13	* 3. All advertising materials mentioning features or use of this software
14	* must display the following acknowledgement:
15	* This product includes software developed by the University of
16	* California, Berkeley and its contributors.
17	* 4. Neither the name of the University nor the names of its contributors
18	* may be used to endorse or promote products derived from this software
19	* without specific prior written permission.
20	*
21	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31	* SUCH DAMAGE.
32	*
33	* @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
34	* in_cksum.c,v 1.2 1994/08/02 07:48:16 davidg Exp
35	*/
36
37	#include <slirp.h>
38
39	/*
40	* Checksum routine for Internet Protocol family headers (Portable Version).
41	*
42	* This routine is very heavily used in the network
43	* code and should be modified for each CPU to be as fast as possible.
44	*
45	* XXX Since we will never span more than 1 mbuf, we can optimise this
46	*/
47
48	#define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
49	#define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
50
51	int cksum(struct mbuf *m, int len)
52	{
53	register u_int16_t *w;
54	register int sum = 0;
55	register int mlen = 0;
56	int byte_swapped = 0;
57
58	union {
59	u_int8_t c[2];
60	u_int16_t s;
61	} s_util;
62	union {
63	u_int16_t s[2];
64	u_int32_t l;
65	} l_util;
66
67	if (m->m_len == 0)
68	goto cont;
69	w = mtod(m, u_int16_t *);
70
71	mlen = m->m_len;
72
73	if (len < mlen)
74	mlen = len;
75	len -= mlen;
76	/*
77	* Force to even boundary.
78	*/
79	if ((1 & (long) w) && (mlen > 0)) {
80	REDUCE;
81	sum <<= 8;
82	s_util.c[0] = (u_int8_t )w;
83	w = (u_int16_t )((int8_t )w + 1);
84	mlen--;
85	byte_swapped = 1;
86	}
87	/*
88	* Unroll the loop to make overhead from
89	* branches &c small.
90	*/
91	while ((mlen -= 32) >= 0) {
92	sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
93	sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
94	sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
95	sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
96	w += 16;
97	}
98	mlen += 32;
99	while ((mlen -= 8) >= 0) {
100	sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
101	w += 4;
102	}
103	mlen += 8;
104	if (mlen == 0 && byte_swapped == 0)
105	goto cont;
106	REDUCE;
107	while ((mlen -= 2) >= 0) {
108	sum += *w++;
109	}
110
111	if (byte_swapped) {
112	REDUCE;
113	sum <<= 8;
114	byte_swapped = 0;
115	if (mlen == -1) {
116	s_util.c[1] = (u_int8_t )w;
117	sum += s_util.s;
118	mlen = 0;
119	} else
120
121	mlen = -1;
122	} else if (mlen == -1)
123	s_util.c[0] = (u_int8_t )w;
124
125	cont:
126	#ifdef DEBUG
127	if (len) {
128	DEBUG_ERROR((dfd, "cksum: out of data\n"));
129	DEBUG_ERROR((dfd, " len = %d\n", len));
130	}
131	#endif
132	if (mlen == -1) {
133	/* The last mbuf has odd # of bytes. Follow the
134	standard (the odd byte may be shifted left by 8 bits
135	or not as determined by endian-ness of the machine) */
136	s_util.c[1] = 0;
137	sum += s_util.s;
138	}
139	REDUCE;
140	return (~sum & 0xffff);
141	}