Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/netiso/iso_chksum.c
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1 /* $NetBSD: iso_chksum.c,v 1.20 2005/02/26 22:39:49 perry Exp $ */ 2 3 /*- 4 * Copyright (c) 1991, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)iso_chksum.c 8.1 (Berkeley) 6/10/93 32 */ 33 34 /*********************************************************** 35 Copyright IBM Corporation 1987 36 37 All Rights Reserved 38 39 Permission to use, copy, modify, and distribute this software and its 40 documentation for any purpose and without fee is hereby granted, 41 provided that the above copyright notice appear in all copies and that 42 both that copyright notice and this permission notice appear in 43 supporting documentation, and that the name of IBM not be 44 used in advertising or publicity pertaining to distribution of the 45 software without specific, written prior permission. 46 47 IBM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING 48 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL 49 IBM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR 50 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, 51 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, 52 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS 53 SOFTWARE. 54 55 ******************************************************************/ 56 57 /* 58 * ARGO Project, Computer Sciences Dept., University of Wisconsin - Madison 59 */ 60 /* 61 * ISO CHECKSUM 62 * 63 * The checksum generation and check routines are here. The checksum is 2 bytes 64 * such that the sum of all the bytes b(i) == 0 and the sum of i * b(i) == 0. 65 * The whole thing is complicated by the fact that the data are in mbuf 66 * chains. Furthermore, there is the possibility of wraparound in the running 67 * sums after adding up 4102 octets. In order to avoid doing a mod operation 68 * after EACH add, we have restricted this implementation to negotiating a 69 * maximum of 4096-octets per TPDU (for the transport layer). The routine 70 * iso_check_csum doesn't need to know where the checksum octets are. The 71 * routine iso_gen_csum takes a pointer to an mbuf chain (logically a chunk 72 * of data), an offset into the chunk at which the 2 octets are to be 73 * stuffed, and the length of the chunk. The 2 octets have to be logically 74 * adjacent, but may be physically located in separate mbufs. 75 */ 76 77 #include <sys/cdefs.h> 78 __KERNEL_RCSID(1, "$NetBSD: iso_chksum.c,v 1.20 2005/02/26 22:39:49 perry Exp $"); 79 80 #include "opt_iso.h" 81 82 #ifdef ISO 83 #include <sys/param.h> 84 #include <sys/systm.h> 85 #include <sys/mbuf.h> 86 #include <sys/socket.h> 87 88 #include <uvm/uvm_extern.h> 89 90 #include <net/if.h> 91 #include <netiso/argo_debug.h> 92 #include <netiso/iso.h> 93 #include <netiso/iso_var.h> 94 #endif /* ISO */ 95 96 /* 97 * FUNCTION: iso_check_csum 98 * 99 * PURPOSE: To check the checksum of the packet in the mbuf chain (m). 100 * The total length of the packet is (len). 101 * Called from tp_input() and clnp_intr() 102 * 103 * RETURNS: TRUE (something non-zero) if there is a checksum error, 104 * FALSE if there was NO checksum error. 105 * 106 * SIDE EFFECTS: none 107 * 108 * NOTES: It might be possible to gain something by optimizing 109 * this routine (unrolling loops, etc). But it is such 110 * a horrible thing to fiddle with anyway, it probably 111 * isn't worth it. 112 */ 113 int 114 iso_check_csum(struct mbuf *m, int len) 115 { 116 u_char *p = mtod(m, u_char *); 117 u_long c0 = 0, c1 = 0; 118 int i = 0; 119 int cum = 0;/* cumulative length */ 120 int l; 121 122 l = len; 123 len = min(m->m_len, len); 124 i = 0; 125 126 #ifdef ARGO_DEBUG 127 if (argo_debug[D_CHKSUM]) { 128 printf("iso_check_csum: m %p, l x%x, m->m_len x%x\n", 129 m, l, m->m_len); 130 } 131 #endif 132 133 while (i < l) { 134 cum += len; 135 while (i < cum) { 136 c0 = c0 + *(p++); 137 c1 += c0; 138 i++; 139 } 140 if (i < l) { 141 m = m->m_next; 142 #ifdef ARGO_DEBUG 143 if (argo_debug[D_CHKSUM]) { 144 printf("iso_check_csum: new mbuf\n"); 145 if (l - i < m->m_len) 146 printf( 147 "bad mbuf chain in check csum l 0x%x i 0x%x m_data %p", 148 l, i, m->m_data); 149 } 150 #endif 151 ASSERT(m != NULL); 152 len = min(m->m_len, l - i); 153 p = mtod(m, u_char *); 154 } 155 } 156 if (((int) c0 % 255) || ((int) c1 % 255)) { 157 #ifdef ARGO_DEBUG 158 if (argo_debug[D_CHKSUM]) { 159 printf("BAD iso_check_csum l 0x%x cum 0x%x len 0x%x, i 0x%x", 160 l, cum, len, i); 161 } 162 #endif 163 return ((int) c0 % 255) << 8 | ((int) c1 % 255); 164 } 165 return 0; 166 } 167 168 /* 169 * FUNCTION: iso_gen_csum 170 * 171 * PURPOSE: To generate the checksum of the packet in the mbuf chain (m). 172 * The first of the 2 (logically) adjacent checksum bytes 173 * (x and y) go at offset (n). 174 * (n) is an offset relative to the beginning of the data, 175 * not the beginning of the mbuf. 176 * (l) is the length of the total mbuf chain's data. 177 * Called from tp_emit(), tp_error_emit() 178 * clnp_emit_er(), clnp_forward(), clnp_output(). 179 * 180 * RETURNS: Rien 181 * 182 * SIDE EFFECTS: Puts the 2 checksum bytes into the packet. 183 * 184 * NOTES: Ditto the note for iso_check_csum(). 185 */ 186 187 void 188 iso_gen_csum( 189 struct mbuf *m, 190 int n, /* offset of 2 checksum bytes */ 191 int l) 192 { 193 u_char *p = mtod(m, u_char *); 194 int c0 = 0, c1 = 0; 195 int i = 0; 196 int loc = n++, len = 0; /* n is position, loc is 197 * offset */ 198 u_char *xloc = NULL; 199 u_char *yloc = NULL; 200 int cum = 0;/* cum == cumulative length */ 201 202 #ifdef ARGO_DEBUG 203 if (argo_debug[D_CHKSUM]) { 204 printf("enter gen csum m %p n 0x%x l 0x%x\n", 205 m, n - 1, l); 206 } 207 #endif 208 209 while (i < l) { 210 len = min(m->m_len, PAGE_SIZE); 211 /* RAH: don't cksum more than l bytes */ 212 len = min(len, l - i); 213 214 cum += len; 215 p = mtod(m, u_char *); 216 217 if (loc >= 0) { 218 if (loc < len) { 219 xloc = loc + mtod(m, u_char *); 220 #ifdef ARGO_DEBUG 221 if (argo_debug[D_CHKSUM]) { 222 printf("1: zeroing xloc %p loc 0x%x\n", 223 xloc, loc); 224 } 225 #endif 226 *xloc = (u_char) 0; 227 if (loc + 1 < len) { 228 /* 229 * both xloc and yloc are in same 230 * mbuf 231 */ 232 yloc = 1 + xloc; 233 #ifdef ARGO_DEBUG 234 if (argo_debug[D_CHKSUM]) { 235 printf( 236 "2: zeroing yloc %p loc 0x%x\n", 237 yloc, loc); 238 } 239 #endif 240 *yloc = (u_char) 0; 241 } else { 242 /* crosses boundary of mbufs */ 243 yloc = mtod(m->m_next, u_char *); 244 #ifdef ARGO_DEBUG 245 if (argo_debug[D_CHKSUM]) { 246 printf( 247 "3: zeroing yloc %p \n", yloc); 248 } 249 #endif 250 *yloc = (u_char) 0; 251 } 252 } 253 loc -= len; 254 } 255 while (i < cum) { 256 c0 = (c0 + *p); 257 c1 += c0; 258 i++; 259 p++; 260 } 261 m = m->m_next; 262 } 263 #ifdef ARGO_DEBUG 264 if (argo_debug[D_CHKSUM]) { 265 printf("gen csum final xloc %p yloc %p\n", xloc, yloc); 266 } 267 #endif 268 269 c1 = (((c0 * (l - n)) - c1) % 255); 270 *xloc = (u_char) ((c1 < 0) ? c1 + 255 : c1); 271 272 c1 = (-(int) (c1 + c0)) % 255; 273 *yloc = (u_char) (c1 < 0 ? c1 + 255 : c1); 274 275 #ifdef ARGO_DEBUG 276 if (argo_debug[D_CHKSUM]) { 277 printf("gen csum end \n"); 278 } 279 #endif 280 } 281 282 /* 283 * FUNCTION: m_datalen 284 * 285 * PURPOSE: returns length of the mbuf chain. 286 * used all over the iso code. 287 * 288 * RETURNS: integer 289 * 290 * SIDE EFFECTS: none 291 * 292 * NOTES: 293 */ 294 295 int 296 m_datalen(struct mbuf *m) 297 { 298 int datalen; 299 300 for (datalen = 0; m; m = m->m_next) 301 datalen += m->m_len; 302 return datalen; 303 } 304 305 int 306 m_compress(struct mbuf *in, struct mbuf **out) 307 { 308 int datalen = 0; 309 int s = splnet(); 310 311 if (in->m_next == NULL) { 312 *out = in; 313 #ifdef ARGO_DEBUG 314 if (argo_debug[D_REQUEST]) { 315 printf("m_compress returning 0x%x: A\n", in->m_len); 316 } 317 #endif 318 splx(s); 319 return in->m_len; 320 } 321 MGET((*out), M_DONTWAIT, MT_DATA); 322 if ((*out) == NULL) { 323 *out = in; 324 #ifdef ARGO_DEBUG 325 if (argo_debug[D_REQUEST]) { 326 printf("m_compress returning -1: B\n"); 327 } 328 #endif 329 splx(s); 330 return -1; 331 } 332 (*out)->m_len = 0; 333 (*out)->m_nextpkt = NULL; 334 335 while (in) { 336 #ifdef ARGO_DEBUG 337 if (argo_debug[D_REQUEST]) { 338 printf("m_compress in %p *out %p\n", in, *out); 339 printf("m_compress in: len 0x%x, off %p\n", 340 in->m_len, in->m_data); 341 printf("m_compress *out: len 0x%x, off %p\n", 342 (*out)->m_len, (*out)->m_data); 343 } 344 #endif 345 if (in->m_flags & M_EXT) { 346 ASSERT(in->m_len == 0); 347 } 348 if (in->m_len == 0) { 349 in = in->m_next; 350 continue; 351 } 352 if (((*out)->m_flags & M_EXT) == 0) { 353 int len; 354 355 len = M_TRAILINGSPACE(*out); 356 len = min(len, in->m_len); 357 datalen += len; 358 359 #ifdef ARGO_DEBUG 360 if (argo_debug[D_REQUEST]) { 361 printf("m_compress copying len %d\n", len); 362 } 363 #endif 364 bcopy(mtod(in, caddr_t), mtod((*out), caddr_t) + (*out)->m_len, 365 (unsigned) len); 366 367 (*out)->m_len += len; 368 in->m_len -= len; 369 continue; 370 } else { 371 /* (*out) is full */ 372 if (((*out)->m_next = m_get(M_DONTWAIT, MT_DATA)) == NULL) { 373 m_freem(*out); 374 *out = in; 375 #ifdef ARGO_DEBUG 376 if (argo_debug[D_REQUEST]) { 377 printf("m_compress returning -1: B\n"); 378 } 379 #endif 380 splx(s); 381 return -1; 382 } 383 (*out)->m_len = 0; 384 (*out)->m_nextpkt = NULL; 385 *out = (*out)->m_next; 386 } 387 } 388 m_freem(in); 389 #ifdef ARGO_DEBUG 390 if (argo_debug[D_REQUEST]) { 391 printf("m_compress returning 0x%x: A\n", datalen); 392 } 393 #endif 394 splx(s); 395 return datalen; 396 }
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