inet_chksum.c

00001 /**
00002  * @file
00003  * Incluse internet checksum functions.
00004  *
00005  */
00006 
00007 /*
00008  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
00009  * All rights reserved.
00010  *
00011  * Redistribution and use in source and binary forms, with or without modification,
00012  * are permitted provided that the following conditions are met:
00013  *
00014  * 1. Redistributions of source code must retain the above copyright notice,
00015  *    this list of conditions and the following disclaimer.
00016  * 2. Redistributions in binary form must reproduce the above copyright notice,
00017  *    this list of conditions and the following disclaimer in the documentation
00018  *    and/or other materials provided with the distribution.
00019  * 3. The name of the author may not be used to endorse or promote products
00020  *    derived from this software without specific prior written permission.
00021  *
00022  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00023  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00024  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00025  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00026  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00027  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00028  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00029  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00030  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00031  * OF SUCH DAMAGE.
00032  *
00033  * This file is part of the lwIP TCP/IP stack.
00034  *
00035  * Author: Adam Dunkels <adam@sics.se>
00036  *
00037  */
00038 
00039 #include "lwip/opt.h"
00040 
00041 #include "lwip/inet_chksum.h"
00042 #include "lwip/def.h"
00043 
00044 #include <stddef.h>
00045 #include <string.h>
00046 
00047 /* These are some reference implementations of the checksum algorithm, with the
00048  * aim of being simple, correct and fully portable. Checksumming is the
00049  * first thing you would want to optimize for your platform. If you create
00050  * your own version, link it in and in your cc.h put:
00051  * 
00052  * #define LWIP_CHKSUM <your_checksum_routine> 
00053  *
00054  * Or you can select from the implementations below by defining
00055  * LWIP_CHKSUM_ALGORITHM to 1, 2 or 3.
00056  */
00057 
00058 #ifndef LWIP_CHKSUM
00059 # define LWIP_CHKSUM lwip_standard_chksum
00060 # ifndef LWIP_CHKSUM_ALGORITHM
00061 #  define LWIP_CHKSUM_ALGORITHM 2
00062 # endif
00063 #endif
00064 /* If none set: */
00065 #ifndef LWIP_CHKSUM_ALGORITHM
00066 # define LWIP_CHKSUM_ALGORITHM 0
00067 #endif
00068 
00069 #if (LWIP_CHKSUM_ALGORITHM == 1) /* Version #1 */
00070 /**
00071  * lwip checksum
00072  *
00073  * @param dataptr points to start of data to be summed at any boundary
00074  * @param len length of data to be summed
00075  * @return host order (!) lwip checksum (non-inverted Internet sum) 
00076  *
00077  * @note accumulator size limits summable length to 64k
00078  * @note host endianess is irrelevant (p3 RFC1071)
00079  */
00080 static u16_t
00081 lwip_standard_chksum(void *dataptr, u16_t len)
00082 {
00083   u32_t acc;
00084   u16_t src;
00085   u8_t *octetptr;
00086 
00087   acc = 0;
00088   /* dataptr may be at odd or even addresses */
00089   octetptr = (u8_t*)dataptr;
00090   while (len > 1) {
00091     /* declare first octet as most significant
00092        thus assume network order, ignoring host order */
00093     src = (*octetptr) << 8;
00094     octetptr++;
00095     /* declare second octet as least significant */
00096     src |= (*octetptr);
00097     octetptr++;
00098     acc += src;
00099     len -= 2;
00100   }
00101   if (len > 0) {
00102     /* accumulate remaining octet */
00103     src = (*octetptr) << 8;
00104     acc += src;
00105   }
00106   /* add deferred carry bits */
00107   acc = (acc >> 16) + (acc & 0x0000ffffUL);
00108   if ((acc & 0xffff0000UL) != 0) {
00109     acc = (acc >> 16) + (acc & 0x0000ffffUL);
00110   }
00111   /* This maybe a little confusing: reorder sum using htons()
00112      instead of ntohs() since it has a little less call overhead.
00113      The caller must invert bits for Internet sum ! */
00114   return htons((u16_t)acc);
00115 }
00116 #endif
00117 
00118 #if (LWIP_CHKSUM_ALGORITHM == 2) /* Alternative version #2 */
00119 /*
00120  * Curt McDowell
00121  * Broadcom Corp.
00122  * csm@broadcom.com
00123  *
00124  * IP checksum two bytes at a time with support for
00125  * unaligned buffer.
00126  * Works for len up to and including 0x20000.
00127  * by Curt McDowell, Broadcom Corp. 12/08/2005
00128  *
00129  * @param dataptr points to start of data to be summed at any boundary
00130  * @param len length of data to be summed
00131  * @return host order (!) lwip checksum (non-inverted Internet sum) 
00132  */
00133 
00134 static u16_t
00135 lwip_standard_chksum(void *dataptr, int len)
00136 {
00137   u8_t *pb = (u8_t *)dataptr;
00138   u16_t *ps, t = 0;
00139   u32_t sum = 0;
00140   int odd = ((mem_ptr_t)pb & 1);
00141 
00142   /* Get aligned to u16_t */
00143   if (odd && len > 0) {
00144     ((u8_t *)&t)[1] = *pb++;
00145     len--;
00146   }
00147 
00148   /* Add the bulk of the data */
00149   ps = (u16_t *)(void *)pb;
00150   while (len > 1) {
00151     sum += *ps++;
00152     len -= 2;
00153   }
00154 
00155   /* Consume left-over byte, if any */
00156   if (len > 0) {
00157     ((u8_t *)&t)[0] = *(u8_t *)ps;
00158   }
00159 
00160   /* Add end bytes */
00161   sum += t;
00162 
00163   /* Fold 32-bit sum to 16 bits
00164      calling this twice is propably faster than if statements... */
00165   sum = FOLD_U32T(sum);
00166   sum = FOLD_U32T(sum);
00167 
00168   /* Swap if alignment was odd */
00169   if (odd) {
00170     sum = SWAP_BYTES_IN_WORD(sum);
00171   }
00172 
00173   return (u16_t)sum;
00174 }
00175 #endif
00176 
00177 #if (LWIP_CHKSUM_ALGORITHM == 3) /* Alternative version #3 */
00178 /**
00179  * An optimized checksum routine. Basically, it uses loop-unrolling on
00180  * the checksum loop, treating the head and tail bytes specially, whereas
00181  * the inner loop acts on 8 bytes at a time. 
00182  *
00183  * @arg start of buffer to be checksummed. May be an odd byte address.
00184  * @len number of bytes in the buffer to be checksummed.
00185  * @return host order (!) lwip checksum (non-inverted Internet sum) 
00186  * 
00187  * by Curt McDowell, Broadcom Corp. December 8th, 2005
00188  */
00189 
00190 static u16_t
00191 lwip_standard_chksum(void *dataptr, int len)
00192 {
00193   u8_t *pb = (u8_t *)dataptr;
00194   u16_t *ps, t = 0;
00195   u32_t *pl;
00196   u32_t sum = 0, tmp;
00197   /* starts at odd byte address? */
00198   int odd = ((mem_ptr_t)pb & 1);
00199 
00200   if (odd && len > 0) {
00201     ((u8_t *)&t)[1] = *pb++;
00202     len--;
00203   }
00204 
00205   ps = (u16_t *)pb;
00206 
00207   if (((mem_ptr_t)ps & 3) && len > 1) {
00208     sum += *ps++;
00209     len -= 2;
00210   }
00211 
00212   pl = (u32_t *)ps;
00213 
00214   while (len > 7)  {
00215     tmp = sum + *pl++;          /* ping */
00216     if (tmp < sum) {
00217       tmp++;                    /* add back carry */
00218     }
00219 
00220     sum = tmp + *pl++;          /* pong */
00221     if (sum < tmp) {
00222       sum++;                    /* add back carry */
00223     }
00224 
00225     len -= 8;
00226   }
00227 
00228   /* make room in upper bits */
00229   sum = FOLD_U32T(sum);
00230 
00231   ps = (u16_t *)pl;
00232 
00233   /* 16-bit aligned word remaining? */
00234   while (len > 1) {
00235     sum += *ps++;
00236     len -= 2;
00237   }
00238 
00239   /* dangling tail byte remaining? */
00240   if (len > 0) {                /* include odd byte */
00241     ((u8_t *)&t)[0] = *(u8_t *)ps;
00242   }
00243 
00244   sum += t;                     /* add end bytes */
00245 
00246   /* Fold 32-bit sum to 16 bits
00247      calling this twice is propably faster than if statements... */
00248   sum = FOLD_U32T(sum);
00249   sum = FOLD_U32T(sum);
00250 
00251   if (odd) {
00252     sum = SWAP_BYTES_IN_WORD(sum);
00253   }
00254 
00255   return (u16_t)sum;
00256 }
00257 #endif
00258 
00259 /* inet_chksum_pseudo:
00260  *
00261  * Calculates the pseudo Internet checksum used by TCP and UDP for a pbuf chain.
00262  * IP addresses are expected to be in network byte order.
00263  *
00264  * @param p chain of pbufs over that a checksum should be calculated (ip data part)
00265  * @param src source ip address (used for checksum of pseudo header)
00266  * @param dst destination ip address (used for checksum of pseudo header)
00267  * @param proto ip protocol (used for checksum of pseudo header)
00268  * @param proto_len length of the ip data part (used for checksum of pseudo header)
00269  * @return checksum (as u16_t) to be saved directly in the protocol header
00270  */
00271 u16_t
00272 inet_chksum_pseudo(struct pbuf *p,
00273        ip_addr_t *src, ip_addr_t *dest,
00274        u8_t proto, u16_t proto_len)
00275 {
00276   u32_t acc;
00277   u32_t addr;
00278   struct pbuf *q;
00279   u8_t swapped;
00280 
00281   acc = 0;
00282   swapped = 0;
00283   /* iterate through all pbuf in chain */
00284   for(q = p; q != NULL; q = q->next) {
00285     LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
00286       (void *)q, (void *)q->next));
00287     acc += LWIP_CHKSUM(q->payload, q->len);
00288     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
00289     /* just executing this next line is probably faster that the if statement needed
00290        to check whether we really need to execute it, and does no harm */
00291     acc = FOLD_U32T(acc);
00292     if (q->len % 2 != 0) {
00293       swapped = 1 - swapped;
00294       acc = SWAP_BYTES_IN_WORD(acc);
00295     }
00296     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
00297   }
00298 
00299   if (swapped) {
00300     acc = SWAP_BYTES_IN_WORD(acc);
00301   }
00302   addr = ip4_addr_get_u32(src);
00303   acc += (addr & 0xffffUL);
00304   acc += ((addr >> 16) & 0xffffUL);
00305   addr = ip4_addr_get_u32(dest);
00306   acc += (addr & 0xffffUL);
00307   acc += ((addr >> 16) & 0xffffUL);
00308   acc += (u32_t)htons((u16_t)proto);
00309   acc += (u32_t)htons(proto_len);
00310 
00311   /* Fold 32-bit sum to 16 bits
00312      calling this twice is propably faster than if statements... */
00313   acc = FOLD_U32T(acc);
00314   acc = FOLD_U32T(acc);
00315   LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
00316   return (u16_t)~(acc & 0xffffUL);
00317 }
00318 
00319 /* inet_chksum_pseudo:
00320  *
00321  * Calculates the pseudo Internet checksum used by TCP and UDP for a pbuf chain.
00322  * IP addresses are expected to be in network byte order.
00323  *
00324  * @param p chain of pbufs over that a checksum should be calculated (ip data part)
00325  * @param src source ip address (used for checksum of pseudo header)
00326  * @param dst destination ip address (used for checksum of pseudo header)
00327  * @param proto ip protocol (used for checksum of pseudo header)
00328  * @param proto_len length of the ip data part (used for checksum of pseudo header)
00329  * @return checksum (as u16_t) to be saved directly in the protocol header
00330  */
00331 u16_t
00332 inet_chksum_pseudo_partial(struct pbuf *p,
00333        ip_addr_t *src, ip_addr_t *dest,
00334        u8_t proto, u16_t proto_len, u16_t chksum_len)
00335 {
00336   u32_t acc;
00337   u32_t addr;
00338   struct pbuf *q;
00339   u8_t swapped;
00340   u16_t chklen;
00341 
00342   acc = 0;
00343   swapped = 0;
00344   /* iterate through all pbuf in chain */
00345   for(q = p; (q != NULL) && (chksum_len > 0); q = q->next) {
00346     LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
00347       (void *)q, (void *)q->next));
00348     chklen = q->len;
00349     if (chklen > chksum_len) {
00350       chklen = chksum_len;
00351     }
00352     acc += LWIP_CHKSUM(q->payload, chklen);
00353     chksum_len -= chklen;
00354     LWIP_ASSERT("delete me", chksum_len < 0x7fff);
00355     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
00356     /* fold the upper bit down */
00357     acc = FOLD_U32T(acc);
00358     if (q->len % 2 != 0) {
00359       swapped = 1 - swapped;
00360       acc = SWAP_BYTES_IN_WORD(acc);
00361     }
00362     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
00363   }
00364 
00365   if (swapped) {
00366     acc = SWAP_BYTES_IN_WORD(acc);
00367   }
00368   addr = ip4_addr_get_u32(src);
00369   acc += (addr & 0xffffUL);
00370   acc += ((addr >> 16) & 0xffffUL);
00371   addr = ip4_addr_get_u32(dest);
00372   acc += (addr & 0xffffUL);
00373   acc += ((addr >> 16) & 0xffffUL);
00374   acc += (u32_t)htons((u16_t)proto);
00375   acc += (u32_t)htons(proto_len);
00376 
00377   /* Fold 32-bit sum to 16 bits
00378      calling this twice is propably faster than if statements... */
00379   acc = FOLD_U32T(acc);
00380   acc = FOLD_U32T(acc);
00381   LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
00382   return (u16_t)~(acc & 0xffffUL);
00383 }
00384 
00385 /* inet_chksum:
00386  *
00387  * Calculates the Internet checksum over a portion of memory. Used primarily for IP
00388  * and ICMP.
00389  *
00390  * @param dataptr start of the buffer to calculate the checksum (no alignment needed)
00391  * @param len length of the buffer to calculate the checksum
00392  * @return checksum (as u16_t) to be saved directly in the protocol header
00393  */
00394 
00395 u16_t
00396 inet_chksum(void *dataptr, u16_t len)
00397 {
00398   return ~LWIP_CHKSUM(dataptr, len);
00399 }
00400 
00401 /**
00402  * Calculate a checksum over a chain of pbufs (without pseudo-header, much like
00403  * inet_chksum only pbufs are used).
00404  *
00405  * @param p pbuf chain over that the checksum should be calculated
00406  * @return checksum (as u16_t) to be saved directly in the protocol header
00407  */
00408 u16_t
00409 inet_chksum_pbuf(struct pbuf *p)
00410 {
00411   u32_t acc;
00412   struct pbuf *q;
00413   u8_t swapped;
00414 
00415   acc = 0;
00416   swapped = 0;
00417   for(q = p; q != NULL; q = q->next) {
00418     acc += LWIP_CHKSUM(q->payload, q->len);
00419     acc = FOLD_U32T(acc);
00420     if (q->len % 2 != 0) {
00421       swapped = 1 - swapped;
00422       acc = SWAP_BYTES_IN_WORD(acc);
00423     }
00424   }
00425 
00426   if (swapped) {
00427     acc = SWAP_BYTES_IN_WORD(acc);
00428   }
00429   return (u16_t)~(acc & 0xffffUL);
00430 }
00431 
00432 /* These are some implementations for LWIP_CHKSUM_COPY, which copies data
00433  * like MEMCPY but generates a checksum at the same time. Since this is a
00434  * performance-sensitive function, you might want to create your own version
00435  * in assembly targeted at your hardware by defining it in lwipopts.h:
00436  *   #define LWIP_CHKSUM_COPY(dst, src, len) your_chksum_copy(dst, src, len)
00437  */
00438 
00439 #if (LWIP_CHKSUM_COPY_ALGORITHM == 1) /* Version #1 */
00440 /** Safe but slow: first call MEMCPY, then call LWIP_CHKSUM.
00441  * For architectures with big caches, data might still be in cache when
00442  * generating the checksum after copying.
00443  */
00444 u16_t
00445 lwip_chksum_copy(void *dst, const void *src, u16_t len)
00446 {
00447   MEMCPY(dst, src, len);
00448   return LWIP_CHKSUM(dst, len);
00449 }
00450 #endif /* (LWIP_CHKSUM_COPY_ALGORITHM == 1) */