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 1.18 2003/08/07 16:33:36 agc 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 1.18 2003/08/07 16:33:36 agc 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(m, len) 115 struct mbuf *m; 116 int len; 117 { 118 u_char *p = mtod(m, u_char *); 119 u_long c0 = 0, c1 = 0; 120 int i = 0; 121 int cum = 0;/* cumulative length */ 122 int l; 123 124 l = len; 125 len = min(m->m_len, len); 126 i = 0; 127 128 #ifdef ARGO_DEBUG 129 if (argo_debug[D_CHKSUM]) { 130 printf("iso_check_csum: m %p, l x%x, m->m_len x%x\n", 131 m, l, m->m_len); 132 } 133 #endif 134 135 while (i < l) { 136 cum += len; 137 while (i < cum) { 138 c0 = c0 + *(p++); 139 c1 += c0; 140 i++; 141 } 142 if (i < l) { 143 m = m->m_next; 144 #ifdef ARGO_DEBUG 145 if (argo_debug[D_CHKSUM]) { 146 printf("iso_check_csum: new mbuf\n"); 147 if (l - i < m->m_len) 148 printf( 149 "bad mbuf chain in check csum l 0x%x i 0x%x m_data %p", 150 l, i, m->m_data); 151 } 152 #endif 153 ASSERT(m != NULL); 154 len = min(m->m_len, l - i); 155 p = mtod(m, u_char *); 156 } 157 } 158 if (((int) c0 % 255) || ((int) c1 % 255)) { 159 #ifdef ARGO_DEBUG 160 if (argo_debug[D_CHKSUM]) { 161 printf("BAD iso_check_csum l 0x%x cum 0x%x len 0x%x, i 0x%x", 162 l, cum, len, i); 163 } 164 #endif 165 return ((int) c0 % 255) << 8 | ((int) c1 % 255); 166 } 167 return 0; 168 } 169 170 /* 171 * FUNCTION: iso_gen_csum 172 * 173 * PURPOSE: To generate the checksum of the packet in the mbuf chain (m). 174 * The first of the 2 (logically) adjacent checksum bytes 175 * (x and y) go at offset (n). 176 * (n) is an offset relative to the beginning of the data, 177 * not the beginning of the mbuf. 178 * (l) is the length of the total mbuf chain's data. 179 * Called from tp_emit(), tp_error_emit() 180 * clnp_emit_er(), clnp_forward(), clnp_output(). 181 * 182 * RETURNS: Rien 183 * 184 * SIDE EFFECTS: Puts the 2 checksum bytes into the packet. 185 * 186 * NOTES: Ditto the note for iso_check_csum(). 187 */ 188 189 void 190 iso_gen_csum(m, n, l) 191 struct mbuf *m; 192 int n; /* offset of 2 checksum bytes */ 193 int l; 194 { 195 u_char *p = mtod(m, u_char *); 196 int c0 = 0, c1 = 0; 197 int i = 0; 198 int loc = n++, len = 0; /* n is position, loc is 199 * offset */ 200 u_char *xloc = NULL; 201 u_char *yloc = NULL; 202 int cum = 0;/* cum == cumulative length */ 203 204 #ifdef ARGO_DEBUG 205 if (argo_debug[D_CHKSUM]) { 206 printf("enter gen csum m %p n 0x%x l 0x%x\n", 207 m, n - 1, l); 208 } 209 #endif 210 211 while (i < l) { 212 len = min(m->m_len, PAGE_SIZE); 213 /* RAH: don't cksum more than l bytes */ 214 len = min(len, l - i); 215 216 cum += len; 217 p = mtod(m, u_char *); 218 219 if (loc >= 0) { 220 if (loc < len) { 221 xloc = loc + mtod(m, u_char *); 222 #ifdef ARGO_DEBUG 223 if (argo_debug[D_CHKSUM]) { 224 printf("1: zeroing xloc %p loc 0x%x\n", 225 xloc, loc); 226 } 227 #endif 228 *xloc = (u_char) 0; 229 if (loc + 1 < len) { 230 /* 231 * both xloc and yloc are in same 232 * mbuf 233 */ 234 yloc = 1 + xloc; 235 #ifdef ARGO_DEBUG 236 if (argo_debug[D_CHKSUM]) { 237 printf( 238 "2: zeroing yloc %p loc 0x%x\n", 239 yloc, loc); 240 } 241 #endif 242 *yloc = (u_char) 0; 243 } else { 244 /* crosses boundary of mbufs */ 245 yloc = mtod(m->m_next, u_char *); 246 #ifdef ARGO_DEBUG 247 if (argo_debug[D_CHKSUM]) { 248 printf( 249 "3: zeroing yloc %p \n", yloc); 250 } 251 #endif 252 *yloc = (u_char) 0; 253 } 254 } 255 loc -= len; 256 } 257 while (i < cum) { 258 c0 = (c0 + *p); 259 c1 += c0; 260 i++; 261 p++; 262 } 263 m = m->m_next; 264 } 265 #ifdef ARGO_DEBUG 266 if (argo_debug[D_CHKSUM]) { 267 printf("gen csum final xloc %p yloc %p\n", xloc, yloc); 268 } 269 #endif 270 271 c1 = (((c0 * (l - n)) - c1) % 255); 272 *xloc = (u_char) ((c1 < 0) ? c1 + 255 : c1); 273 274 c1 = (-(int) (c1 + c0)) % 255; 275 *yloc = (u_char) (c1 < 0 ? c1 + 255 : c1); 276 277 #ifdef ARGO_DEBUG 278 if (argo_debug[D_CHKSUM]) { 279 printf("gen csum end \n"); 280 } 281 #endif 282 } 283 284 /* 285 * FUNCTION: m_datalen 286 * 287 * PURPOSE: returns length of the mbuf chain. 288 * used all over the iso code. 289 * 290 * RETURNS: integer 291 * 292 * SIDE EFFECTS: none 293 * 294 * NOTES: 295 */ 296 297 int 298 m_datalen(m) 299 struct mbuf *m; 300 { 301 int datalen; 302 303 for (datalen = 0; m; m = m->m_next) 304 datalen += m->m_len; 305 return datalen; 306 } 307 308 int 309 m_compress(in, out) 310 struct mbuf *in, **out; 311 { 312 int datalen = 0; 313 int s = splnet(); 314 315 if (in->m_next == NULL) { 316 *out = in; 317 #ifdef ARGO_DEBUG 318 if (argo_debug[D_REQUEST]) { 319 printf("m_compress returning 0x%x: A\n", in->m_len); 320 } 321 #endif 322 splx(s); 323 return in->m_len; 324 } 325 MGET((*out), M_DONTWAIT, MT_DATA); 326 if ((*out) == NULL) { 327 *out = in; 328 #ifdef ARGO_DEBUG 329 if (argo_debug[D_REQUEST]) { 330 printf("m_compress returning -1: B\n"); 331 } 332 #endif 333 splx(s); 334 return -1; 335 } 336 (*out)->m_len = 0; 337 (*out)->m_nextpkt = NULL; 338 339 while (in) { 340 #ifdef ARGO_DEBUG 341 if (argo_debug[D_REQUEST]) { 342 printf("m_compress in %p *out %p\n", in, *out); 343 printf("m_compress in: len 0x%x, off %p\n", 344 in->m_len, in->m_data); 345 printf("m_compress *out: len 0x%x, off %p\n", 346 (*out)->m_len, (*out)->m_data); 347 } 348 #endif 349 if (in->m_flags & M_EXT) { 350 ASSERT(in->m_len == 0); 351 } 352 if (in->m_len == 0) { 353 in = in->m_next; 354 continue; 355 } 356 if (((*out)->m_flags & M_EXT) == 0) { 357 int len; 358 359 len = M_TRAILINGSPACE(*out); 360 len = min(len, in->m_len); 361 datalen += len; 362 363 #ifdef ARGO_DEBUG 364 if (argo_debug[D_REQUEST]) { 365 printf("m_compress copying len %d\n", len); 366 } 367 #endif 368 bcopy(mtod(in, caddr_t), mtod((*out), caddr_t) + (*out)->m_len, 369 (unsigned) len); 370 371 (*out)->m_len += len; 372 in->m_len -= len; 373 continue; 374 } else { 375 /* (*out) is full */ 376 if (((*out)->m_next = m_get(M_DONTWAIT, MT_DATA)) == NULL) { 377 m_freem(*out); 378 *out = in; 379 #ifdef ARGO_DEBUG 380 if (argo_debug[D_REQUEST]) { 381 printf("m_compress returning -1: B\n"); 382 } 383 #endif 384 splx(s); 385 return -1; 386 } 387 (*out)->m_len = 0; 388 (*out)->m_nextpkt = NULL; 389 *out = (*out)->m_next; 390 } 391 } 392 m_freem(in); 393 #ifdef ARGO_DEBUG 394 if (argo_debug[D_REQUEST]) { 395 printf("m_compress returning 0x%x: A\n", datalen); 396 } 397 #endif 398 splx(s); 399 return datalen; 400 }
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