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/inet.h"
00043 
00044 /* These are some reference implementations of the checksum algorithm, with the
00045  * aim of being simple, correct and fully portable. Checksumming is the
00046  * first thing you would want to optimize for your platform. If you create
00047  * your own version, link it in and in your cc.h put:
00048  * 
00049  * #define LWIP_CHKSUM <your_checksum_routine> 
00050  *
00051  * Or you can select from the implementations below by defining
00052  * LWIP_CHKSUM_ALGORITHM to 1, 2 or 3.
00053  */
00054 
00055 #ifndef LWIP_CHKSUM
00056 # define LWIP_CHKSUM lwip_standard_chksum
00057 # ifndef LWIP_CHKSUM_ALGORITHM
00058 #  define LWIP_CHKSUM_ALGORITHM 1
00059 # endif
00060 #endif
00061 /* If none set: */
00062 #ifndef LWIP_CHKSUM_ALGORITHM
00063 # define LWIP_CHKSUM_ALGORITHM 0
00064 #endif
00065 
00066 /** Like the name says... */
00067 #define SWAP_BYTES_IN_WORD(w) ((w & 0xff) << 8) | ((w & 0xff00) >> 8)
00068 /** Split an u32_t in two u16_ts and add them up */
00069 #define FOLD_U32T(u)          ((u >> 16) + (u & 0x0000ffffUL))
00070 
00071 #if (LWIP_CHKSUM_ALGORITHM == 1) /* Version #1 */
00072 /**
00073  * lwip checksum
00074  *
00075  * @param dataptr points to start of data to be summed at any boundary
00076  * @param len length of data to be summed
00077  * @return host order (!) lwip checksum (non-inverted Internet sum) 
00078  *
00079  * @note accumulator size limits summable length to 64k
00080  * @note host endianess is irrelevant (p3 RFC1071)
00081  */
00082 static u16_t
00083 lwip_standard_chksum(void *dataptr, u16_t len)
00084 {
00085   u32_t acc;
00086   u16_t src;
00087   u8_t *octetptr;
00088 
00089   acc = 0;
00090   /* dataptr may be at odd or even addresses */
00091   octetptr = (u8_t*)dataptr;
00092   while (len > 1) {
00093     /* declare first octet as most significant
00094        thus assume network order, ignoring host order */
00095     src = (*octetptr) << 8;
00096     octetptr++;
00097     /* declare second octet as least significant */
00098     src |= (*octetptr);
00099     octetptr++;
00100     acc += src;
00101     len -= 2;
00102   }
00103   if (len > 0) {
00104     /* accumulate remaining octet */
00105     src = (*octetptr) << 8;
00106     acc += src;
00107   }
00108   /* add deferred carry bits */
00109   acc = (acc >> 16) + (acc & 0x0000ffffUL);
00110   if ((acc & 0xffff0000UL) != 0) {
00111     acc = (acc >> 16) + (acc & 0x0000ffffUL);
00112   }
00113   /* This maybe a little confusing: reorder sum using htons()
00114      instead of ntohs() since it has a little less call overhead.
00115      The caller must invert bits for Internet sum ! */
00116   return htons((u16_t)acc);
00117 }
00118 #endif
00119 
00120 #if (LWIP_CHKSUM_ALGORITHM == 2) /* Alternative version #2 */
00121 /*
00122  * Curt McDowell
00123  * Broadcom Corp.
00124  * csm@broadcom.com
00125  *
00126  * IP checksum two bytes at a time with support for
00127  * unaligned buffer.
00128  * Works for len up to and including 0x20000.
00129  * by Curt McDowell, Broadcom Corp. 12/08/2005
00130  *
00131  * @param dataptr points to start of data to be summed at any boundary
00132  * @param len length of data to be summed
00133  * @return host order (!) lwip checksum (non-inverted Internet sum) 
00134  */
00135 
00136 static u16_t
00137 lwip_standard_chksum(void *dataptr, int len)
00138 {
00139   u8_t *pb = dataptr;
00140   u16_t *ps, t = 0;
00141   u32_t sum = 0;
00142   int odd = ((u32_t)pb & 1);
00143 
00144   /* Get aligned to u16_t */
00145   if (odd && len > 0) {
00146     ((u8_t *)&t)[1] = *pb++;
00147     len--;
00148   }
00149 
00150   /* Add the bulk of the data */
00151   ps = (u16_t *)pb;
00152   while (len > 1) {
00153     sum += *ps++;
00154     len -= 2;
00155   }
00156 
00157   /* Consume left-over byte, if any */
00158   if (len > 0) {
00159     ((u8_t *)&t)[0] = *(u8_t *)ps;;
00160   }
00161 
00162   /* Add end bytes */
00163   sum += t;
00164 
00165   /* Fold 32-bit sum to 16 bits
00166      calling this twice is propably faster than if statements... */
00167   sum = FOLD_U32T(sum);
00168   sum = FOLD_U32T(sum);
00169 
00170   /* Swap if alignment was odd */
00171   if (odd) {
00172     sum = SWAP_BYTES_IN_WORD(sum);
00173   }
00174 
00175   return sum;
00176 }
00177 #endif
00178 
00179 #if (LWIP_CHKSUM_ALGORITHM == 3) /* Alternative version #3 */
00180 /**
00181  * An optimized checksum routine. Basically, it uses loop-unrolling on
00182  * the checksum loop, treating the head and tail bytes specially, whereas
00183  * the inner loop acts on 8 bytes at a time. 
00184  *
00185  * @arg start of buffer to be checksummed. May be an odd byte address.
00186  * @len number of bytes in the buffer to be checksummed.
00187  * @return host order (!) lwip checksum (non-inverted Internet sum) 
00188  * 
00189  * by Curt McDowell, Broadcom Corp. December 8th, 2005
00190  */
00191 
00192 static u16_t
00193 lwip_standard_chksum(void *dataptr, int len)
00194 {
00195   u8_t *pb = dataptr;
00196   u16_t *ps, t = 0;
00197   u32_t *pl;
00198   u32_t sum = 0, tmp;
00199   /* starts at odd byte address? */
00200   int odd = ((u32_t)pb & 1);
00201 
00202   if (odd && len > 0) {
00203     ((u8_t *)&t)[1] = *pb++;
00204     len--;
00205   }
00206 
00207   ps = (u16_t *)pb;
00208 
00209   if (((u32_t)ps & 3) && len > 1) {
00210     sum += *ps++;
00211     len -= 2;
00212   }
00213 
00214   pl = (u32_t *)ps;
00215 
00216   while (len > 7)  {
00217     tmp = sum + *pl++;          /* ping */
00218     if (tmp < sum) {
00219       tmp++;                    /* add back carry */
00220     }
00221 
00222     sum = tmp + *pl++;          /* pong */
00223     if (sum < tmp) {
00224       sum++;                    /* add back carry */
00225     }
00226 
00227     len -= 8;
00228   }
00229 
00230   /* make room in upper bits */
00231   sum = FOLD_U32T(sum);
00232 
00233   ps = (u16_t *)pl;
00234 
00235   /* 16-bit aligned word remaining? */
00236   while (len > 1) {
00237     sum += *ps++;
00238     len -= 2;
00239   }
00240 
00241   /* dangling tail byte remaining? */
00242   if (len > 0) {                /* include odd byte */
00243     ((u8_t *)&t)[0] = *(u8_t *)ps;
00244   }
00245 
00246   sum += t;                     /* add end bytes */
00247 
00248   /* Fold 32-bit sum to 16 bits
00249      calling this twice is propably faster than if statements... */
00250   sum = FOLD_U32T(sum);
00251   sum = FOLD_U32T(sum);
00252 
00253   if (odd) {
00254     sum = SWAP_BYTES_IN_WORD(sum);
00255   }
00256 
00257   return sum;
00258 }
00259 #endif
00260 
00261 /* inet_chksum_pseudo:
00262  *
00263  * Calculates the pseudo Internet checksum used by TCP and UDP for a pbuf chain.
00264  * IP addresses are expected to be in network byte order.
00265  *
00266  * @param p chain of pbufs over that a checksum should be calculated (ip data part)
00267  * @param src source ip address (used for checksum of pseudo header)
00268  * @param dst destination ip address (used for checksum of pseudo header)
00269  * @param proto ip protocol (used for checksum of pseudo header)
00270  * @param proto_len length of the ip data part (used for checksum of pseudo header)
00271  * @return checksum (as u16_t) to be saved directly in the protocol header
00272  */
00273 u16_t
00274 inet_chksum_pseudo(struct pbuf *p,
00275        struct ip_addr *src, struct ip_addr *dest,
00276        u8_t proto, u16_t proto_len)
00277 {
00278   u32_t acc;
00279   struct pbuf *q;
00280   u8_t swapped;
00281 
00282   acc = 0;
00283   swapped = 0;
00284   /* iterate through all pbuf in chain */
00285   for(q = p; q != NULL; q = q->next) {
00286     LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): checksumming pbuf %p (has next %p) \n",
00287       (void *)q, (void *)q->next));
00288     acc += LWIP_CHKSUM(q->payload, q->len);
00289     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): unwrapped lwip_chksum()=%"X32_F" \n", acc));*/
00290     /* just executing this next line is probably faster that the if statement needed
00291        to check whether we really need to execute it, and does no harm */
00292     acc = FOLD_U32T(acc);
00293     if (q->len % 2 != 0) {
00294       swapped = 1 - swapped;
00295       acc = SWAP_BYTES_IN_WORD(acc);
00296     }
00297     /*LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): wrapped lwip_chksum()=%"X32_F" \n", acc));*/
00298   }
00299 
00300   if (swapped) {
00301     acc = SWAP_BYTES_IN_WORD(acc);
00302   }
00303   acc += (src->addr & 0xffffUL);
00304   acc += ((src->addr >> 16) & 0xffffUL);
00305   acc += (dest->addr & 0xffffUL);
00306   acc += ((dest->addr >> 16) & 0xffffUL);
00307   acc += (u32_t)htons((u16_t)proto);
00308   acc += (u32_t)htons(proto_len);
00309 
00310   /* Fold 32-bit sum to 16 bits
00311      calling this twice is propably faster than if statements... */
00312   acc = FOLD_U32T(acc);
00313   acc = FOLD_U32T(acc);
00314   LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
00315   return (u16_t)~(acc & 0xffffUL);
00316 }
00317 
00318 /* inet_chksum_pseudo:
00319  *
00320  * Calculates the pseudo Internet checksum used by TCP and UDP for a pbuf chain.
00321  * IP addresses are expected to be in network byte order.
00322  *
00323  * @param p chain of pbufs over that a checksum should be calculated (ip data part)
00324  * @param src source ip address (used for checksum of pseudo header)
00325  * @param dst destination ip address (used for checksum of pseudo header)
00326  * @param proto ip protocol (used for checksum of pseudo header)
00327  * @param proto_len length of the ip data part (used for checksum of pseudo header)
00328  * @return checksum (as u16_t) to be saved directly in the protocol header
00329  */
00330 /* Currently only used by UDPLITE, although this could change in the future. */
00331 #if LWIP_UDPLITE
00332 u16_t
00333 inet_chksum_pseudo_partial(struct pbuf *p,
00334        struct ip_addr *src, struct ip_addr *dest,
00335        u8_t proto, u16_t proto_len, u16_t chksum_len)
00336 {
00337   u32_t acc;
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   acc += (src->addr & 0xffffUL);
00369   acc += ((src->addr >> 16) & 0xffffUL);
00370   acc += (dest->addr & 0xffffUL);
00371   acc += ((dest->addr >> 16) & 0xffffUL);
00372   acc += (u32_t)htons((u16_t)proto);
00373   acc += (u32_t)htons(proto_len);
00374 
00375   /* Fold 32-bit sum to 16 bits
00376      calling this twice is propably faster than if statements... */
00377   acc = FOLD_U32T(acc);
00378   acc = FOLD_U32T(acc);
00379   LWIP_DEBUGF(INET_DEBUG, ("inet_chksum_pseudo(): pbuf chain lwip_chksum()=%"X32_F"\n", acc));
00380   return (u16_t)~(acc & 0xffffUL);
00381 }
00382 #endif /* LWIP_UDPLITE */
00383 
00384 /* inet_chksum:
00385  *
00386  * Calculates the Internet checksum over a portion of memory. Used primarily for IP
00387  * and ICMP.
00388  *
00389  * @param dataptr start of the buffer to calculate the checksum (no alignment needed)
00390  * @param len length of the buffer to calculate the checksum
00391  * @return checksum (as u16_t) to be saved directly in the protocol header
00392  */
00393 
00394 u16_t
00395 inet_chksum(void *dataptr, u16_t len)
00396 {
00397   return ~LWIP_CHKSUM(dataptr, len);
00398 }
00399 
00400 /**
00401  * Calculate a checksum over a chain of pbufs (without pseudo-header, much like
00402  * inet_chksum only pbufs are used).
00403  *
00404  * @param p pbuf chain over that the checksum should be calculated
00405  * @return checksum (as u16_t) to be saved directly in the protocol header
00406  */
00407 u16_t
00408 inet_chksum_pbuf(struct pbuf *p)
00409 {
00410   u32_t acc;
00411   struct pbuf *q;
00412   u8_t swapped;
00413 
00414   acc = 0;
00415   swapped = 0;
00416   for(q = p; q != NULL; q = q->next) {
00417     acc += LWIP_CHKSUM(q->payload, q->len);
00418     acc = FOLD_U32T(acc);
00419     if (q->len % 2 != 0) {
00420       swapped = 1 - swapped;
00421       acc = SWAP_BYTES_IN_WORD(acc);
00422     }
00423   }
00424 
00425   if (swapped) {
00426     acc = SWAP_BYTES_IN_WORD(acc);
00427   }
00428   return (u16_t)~(acc & 0xffffUL);
00429 }