Annotation of sys/netinet6/in6_cksum.c, Revision 1.1.1.1
1.1 nbrk 1: /* $OpenBSD: in6_cksum.c,v 1.14 2006/11/17 01:11:23 itojun Exp $ */
2: /* $KAME: in6_cksum.c,v 1.10 2000/12/03 00:53:59 itojun Exp $ */
3:
4: /*
5: * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
6: * All rights reserved.
7: *
8: * Redistribution and use in source and binary forms, with or without
9: * modification, are permitted provided that the following conditions
10: * are met:
11: * 1. Redistributions of source code must retain the above copyright
12: * notice, this list of conditions and the following disclaimer.
13: * 2. Redistributions in binary form must reproduce the above copyright
14: * notice, this list of conditions and the following disclaimer in the
15: * documentation and/or other materials provided with the distribution.
16: * 3. Neither the name of the project nor the names of its contributors
17: * may be used to endorse or promote products derived from this software
18: * without specific prior written permission.
19: *
20: * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
21: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23: * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
24: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30: * SUCH DAMAGE.
31: */
32:
33: /*
34: * Copyright (c) 1988, 1992, 1993
35: * The Regents of the University of California. All rights reserved.
36: *
37: * Redistribution and use in source and binary forms, with or without
38: * modification, are permitted provided that the following conditions
39: * are met:
40: * 1. Redistributions of source code must retain the above copyright
41: * notice, this list of conditions and the following disclaimer.
42: * 2. Redistributions in binary form must reproduce the above copyright
43: * notice, this list of conditions and the following disclaimer in the
44: * documentation and/or other materials provided with the distribution.
45: * 3. Neither the name of the University nor the names of its contributors
46: * may be used to endorse or promote products derived from this software
47: * without specific prior written permission.
48: *
49: * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
50: * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
51: * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
52: * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
53: * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
54: * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
55: * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
56: * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
57: * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
58: * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
59: * SUCH DAMAGE.
60: *
61: * @(#)in_cksum.c 8.1 (Berkeley) 6/10/93
62: */
63:
64: #include <sys/param.h>
65: #include <sys/mbuf.h>
66: #include <sys/systm.h>
67: #include <netinet/in.h>
68: #include <netinet/ip6.h>
69:
70: /*
71: * Checksum routine for Internet Protocol family headers (Portable Version).
72: *
73: * This routine is very heavily used in the network
74: * code and should be modified for each CPU to be as fast as possible.
75: */
76:
77: #define ADDCARRY(x) (x > 65535 ? x -= 65535 : x)
78: #define REDUCE {l_util.l = sum; sum = l_util.s[0] + l_util.s[1]; ADDCARRY(sum);}
79:
80: /*
81: * m MUST contain a continuous IP6 header.
82: * off is a offset where TCP/UDP/ICMP6 header starts.
83: * len is a total length of a transport segment.
84: * (e.g. TCP header + TCP payload)
85: */
86:
87: int
88: in6_cksum(m, nxt, off, len)
89: struct mbuf *m;
90: u_int8_t nxt;
91: u_int32_t off, len;
92: {
93: u_int16_t *w;
94: int sum = 0;
95: int mlen = 0;
96: int byte_swapped = 0;
97: struct ip6_hdr *ip6;
98: union {
99: u_int16_t phs[4];
100: struct {
101: u_int32_t ph_len;
102: u_int8_t ph_zero[3];
103: u_int8_t ph_nxt;
104: } ph __packed;
105: } uph;
106: union {
107: u_int8_t c[2];
108: u_int16_t s;
109: } s_util;
110: union {
111: u_int16_t s[2];
112: u_int32_t l;
113: } l_util;
114:
115: /* sanity check */
116: if (m->m_pkthdr.len < off + len) {
117: panic("in6_cksum: mbuf len (%d) < off+len (%d+%d)",
118: m->m_pkthdr.len, off, len);
119: }
120:
121: bzero(&uph, sizeof(uph));
122:
123: /*
124: * First create IP6 pseudo header and calculate a summary.
125: */
126: ip6 = mtod(m, struct ip6_hdr *);
127: w = (u_int16_t *)&ip6->ip6_src;
128: uph.ph.ph_len = htonl(len);
129: uph.ph.ph_nxt = nxt;
130:
131: /* IPv6 source address */
132: sum += w[0];
133: if (!IN6_IS_SCOPE_EMBED(&ip6->ip6_src))
134: sum += w[1];
135: sum += w[2]; sum += w[3]; sum += w[4]; sum += w[5];
136: sum += w[6]; sum += w[7];
137: /* IPv6 destination address */
138: sum += w[8];
139: if (!IN6_IS_SCOPE_EMBED(&ip6->ip6_dst))
140: sum += w[9];
141: sum += w[10]; sum += w[11]; sum += w[12]; sum += w[13];
142: sum += w[14]; sum += w[15];
143: /* Payload length and upper layer identifier */
144: sum += uph.phs[0]; sum += uph.phs[1];
145: sum += uph.phs[2]; sum += uph.phs[3];
146:
147: /*
148: * Secondly calculate a summary of the first mbuf excluding offset.
149: */
150: while (m != NULL && off > 0) {
151: if (m->m_len <= off)
152: off -= m->m_len;
153: else
154: break;
155: m = m->m_next;
156: }
157: w = (u_int16_t *)(mtod(m, u_char *) + off);
158: mlen = m->m_len - off;
159: if (len < mlen)
160: mlen = len;
161: len -= mlen;
162: /*
163: * Force to even boundary.
164: */
165: if ((1 & (long) w) && (mlen > 0)) {
166: REDUCE;
167: sum <<= 8;
168: s_util.c[0] = *(u_char *)w;
169: w = (u_int16_t *)((char *)w + 1);
170: mlen--;
171: byte_swapped = 1;
172: }
173: /*
174: * Unroll the loop to make overhead from
175: * branches &c small.
176: */
177: while ((mlen -= 32) >= 0) {
178: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
179: sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
180: sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
181: sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
182: w += 16;
183: }
184: mlen += 32;
185: while ((mlen -= 8) >= 0) {
186: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
187: w += 4;
188: }
189: mlen += 8;
190: if (mlen == 0 && byte_swapped == 0)
191: goto next;
192: REDUCE;
193: while ((mlen -= 2) >= 0) {
194: sum += *w++;
195: }
196: if (byte_swapped) {
197: REDUCE;
198: sum <<= 8;
199: byte_swapped = 0;
200: if (mlen == -1) {
201: s_util.c[1] = *(char *)w;
202: sum += s_util.s;
203: mlen = 0;
204: } else
205: mlen = -1;
206: } else if (mlen == -1)
207: s_util.c[0] = *(char *)w;
208: next:
209: m = m->m_next;
210:
211: /*
212: * Lastly calculate a summary of the rest of mbufs.
213: */
214:
215: for (;m && len; m = m->m_next) {
216: if (m->m_len == 0)
217: continue;
218: w = mtod(m, u_int16_t *);
219: if (mlen == -1) {
220: /*
221: * The first byte of this mbuf is the continuation
222: * of a word spanning between this mbuf and the
223: * last mbuf.
224: *
225: * s_util.c[0] is already saved when scanning previous
226: * mbuf.
227: */
228: s_util.c[1] = *(char *)w;
229: sum += s_util.s;
230: w = (u_int16_t *)((char *)w + 1);
231: mlen = m->m_len - 1;
232: len--;
233: } else
234: mlen = m->m_len;
235: if (len < mlen)
236: mlen = len;
237: len -= mlen;
238: /*
239: * Force to even boundary.
240: */
241: if ((1 & (long) w) && (mlen > 0)) {
242: REDUCE;
243: sum <<= 8;
244: s_util.c[0] = *(u_char *)w;
245: w = (u_int16_t *)((char *)w + 1);
246: mlen--;
247: byte_swapped = 1;
248: }
249: /*
250: * Unroll the loop to make overhead from
251: * branches &c small.
252: */
253: while ((mlen -= 32) >= 0) {
254: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
255: sum += w[4]; sum += w[5]; sum += w[6]; sum += w[7];
256: sum += w[8]; sum += w[9]; sum += w[10]; sum += w[11];
257: sum += w[12]; sum += w[13]; sum += w[14]; sum += w[15];
258: w += 16;
259: }
260: mlen += 32;
261: while ((mlen -= 8) >= 0) {
262: sum += w[0]; sum += w[1]; sum += w[2]; sum += w[3];
263: w += 4;
264: }
265: mlen += 8;
266: if (mlen == 0 && byte_swapped == 0)
267: continue;
268: REDUCE;
269: while ((mlen -= 2) >= 0) {
270: sum += *w++;
271: }
272: if (byte_swapped) {
273: REDUCE;
274: sum <<= 8;
275: byte_swapped = 0;
276: if (mlen == -1) {
277: s_util.c[1] = *(char *)w;
278: sum += s_util.s;
279: mlen = 0;
280: } else
281: mlen = -1;
282: } else if (mlen == -1)
283: s_util.c[0] = *(char *)w;
284: }
285: if (len)
286: panic("in6_cksum: out of data");
287: if (mlen == -1) {
288: /* The last mbuf has odd # of bytes. Follow the
289: standard (the odd byte may be shifted left by 8 bits
290: or not as determined by endian-ness of the machine) */
291: s_util.c[1] = 0;
292: sum += s_util.s;
293: }
294: REDUCE;
295: return (~sum & 0xffff);
296: }
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