Annotation of sys/netinet/in4_cksum.c, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: in4_cksum.c,v 1.7 2003/06/02 23:28:13 millert Exp $ */
2: /* $KAME: in4_cksum.c,v 1.10 2001/11/30 10:06:15 itojun Exp $ */
3: /* $NetBSD: in_cksum.c,v 1.13 1996/10/13 02:03:03 christos Exp $ */
4:
5: /*
6: * Copyright (C) 1999 WIDE Project.
7: * All rights reserved.
8: *
9: * Redistribution and use in source and binary forms, with or without
10: * modification, are permitted provided that the following conditions
11: * are met:
12: * 1. Redistributions of source code must retain the above copyright
13: * notice, this list of conditions and the following disclaimer.
14: * 2. Redistributions in binary form must reproduce the above copyright
15: * notice, this list of conditions and the following disclaimer in the
16: * documentation and/or other materials provided with the distribution.
17: * 3. Neither the name of the project 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 PROJECT 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 PROJECT 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:
34: /*
35: * Copyright (c) 1988, 1992, 1993
36: * The Regents of the University of California. All rights reserved.
37: *
38: * Redistribution and use in source and binary forms, with or without
39: * modification, are permitted provided that the following conditions
40: * are met:
41: * 1. Redistributions of source code must retain the above copyright
42: * notice, this list of conditions and the following disclaimer.
43: * 2. Redistributions in binary form must reproduce the above copyright
44: * notice, this list of conditions and the following disclaimer in the
45: * documentation and/or other materials provided with the distribution.
46: * 3. Neither the name of the University nor the names of its contributors
47: * may be used to endorse or promote products derived from this software
48: * without specific prior written permission.
49: *
50: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
51: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
53: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
54: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
55: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
56: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
58: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
59: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
60: * SUCH DAMAGE.
61: *
62: * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
63: */
64:
65: #include <sys/param.h>
66: #include <sys/mbuf.h>
67: #include <sys/systm.h>
68: #include <sys/socket.h>
69: #include <net/route.h>
70: #include <netinet/in.h>
71: #include <netinet/in_systm.h>
72: #include <netinet/ip.h>
73: #include <netinet/ip_var.h>
74:
75: /*
76: * Checksum routine for Internet Protocol family headers (Portable Version).
77: * This is only for IPv4 pseudo header checksum.
78: * No need to clear non-pseudo-header fields in IPv4 header.
79: * len is for actual payload size, and does not include IPv4 header and
80: * skipped header chain (off + len should be equal to the whole packet).
81: *
82: * This routine is very heavily used in the network
83: * code and should be modified for each CPU to be as fast as possible.
84: */
85:
86: #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
87: #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
88:
89: int
90: in4_cksum(m, nxt, off, len)
91: struct mbuf *m;
92: u_int8_t nxt;
93: int off, len;
94: {
95: u_int16_t *w;
96: int sum = 0;
97: int mlen = 0;
98: int byte_swapped = 0;
99: union {
100: struct ipovly ipov;
101: u_int16_t w[10];
102: } u;
103: union {
104: u_int8_t c[2];
105: u_int16_t s;
106: } s_util;
107: union {
108: u_int16_t s[2];
109: u_int32_t l;
110: } l_util;
111:
112: if (nxt != 0) {
113: /* pseudo header */
114: if (off < sizeof(struct ipovly))
115: panic("in4_cksum: offset too short");
116: if (m->m_len < sizeof(struct ip))
117: panic("in4_cksum: bad mbuf chain");
118: bzero(&u.ipov, sizeof(u.ipov));
119: u.ipov.ih_len = htons(len);
120: u.ipov.ih_pr = nxt;
121: u.ipov.ih_src = mtod(m, struct ip *)->ip_src;
122: u.ipov.ih_dst = mtod(m, struct ip *)->ip_dst;
123: w = u.w;
124: /* assumes sizeof(ipov) == 20 */
125: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3]; sum += w[4];
126: sum += w[5]; sum += w[6]; sum += w[7]; sum += w[8]; sum += w[9];
127: }
128:
129: /* skip unnecessary part */
130: while (m && off > 0) {
131: if (m->m_len > off)
132: break;
133: off -= m->m_len;
134: m = m->m_next;
135: }
136:
137: for (;m && len; m = m->m_next) {
138: if (m->m_len == 0)
139: continue;
140: w = (u_int16_t *)(mtod(m, caddr_t) + off);
141: if (mlen == -1) {
142: /*
143: * The first byte of this mbuf is the continuation
144: * of a word spanning between this mbuf and the
145: * last mbuf.
146: *
147: * s_util.c[0] is already saved when scanning previous
148: * mbuf.
149: */
150: s_util.c[1] = *(u_int8_t *)w;
151: sum += s_util.s;
152: w = (u_int16_t *)((u_int8_t *)w + 1);
153: mlen = m->m_len - off - 1;
154: len--;
155: } else
156: mlen = m->m_len - off;
157: off = 0;
158: if (len < mlen)
159: mlen = len;
160: len -= mlen;
161: /*
162: * Force to even boundary.
163: */
164: if ((1 & (long) w) && (mlen > 0)) {
165: REDUCE;
166: sum <<= 8;
167: s_util.c[0] = *(u_int8_t *)w;
168: w = (u_int16_t *)((int8_t *)w + 1);
169: mlen--;
170: byte_swapped = 1;
171: }
172: /*
173: * Unroll the loop to make overhead from
174: * branches &c small.
175: */
176: while ((mlen -= 32) >= 0) {
177: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
178: sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
179: sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
180: sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
181: w += 16;
182: }
183: mlen += 32;
184: while ((mlen -= 8) >= 0) {
185: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
186: w += 4;
187: }
188: mlen += 8;
189: if (mlen == 0 && byte_swapped == 0)
190: continue;
191: REDUCE;
192: while ((mlen -= 2) >= 0) {
193: sum += *w++;
194: }
195: if (byte_swapped) {
196: REDUCE;
197: sum <<= 8;
198: byte_swapped = 0;
199: if (mlen == -1) {
200: s_util.c[1] = *(u_int8_t *)w;
201: sum += s_util.s;
202: mlen = 0;
203: } else
204: mlen = -1;
205: } else if (mlen == -1)
206: s_util.c[0] = *(u_int8_t *)w;
207: }
208: if (len)
209: printf("cksum4: out of data\n");
210: if (mlen == -1) {
211: /* The last mbuf has odd # of bytes. Follow the
212: standard (the odd byte may be shifted left by 8 bits
213: or not as determined by endian-ness of the machine) */
214: s_util.c[1] = 0;
215: sum += s_util.s;
216: }
217: REDUCE;
218: return (~sum & 0xffff);
219: }
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