dlls/icmp/icmp_main.c

   1 /*
   2  * ICMP
   3  *
   4  * Francois Gouget, 1999, based on the work of
   5  *   RW Hall, 1999, based on public domain code PING.C by Mike Muus (1983)
   6  *   and later works (c) 1989 Regents of Univ. of California - see copyright
   7  *   notice at end of source-code.
   8  */
   9
  10 /* Future work:
  11  * - Systems like FreeBSD don't seem to support the IP_TTL option and maybe others.
  12  *   But using IP_HDRINCL and building the IP header by hand might work.
  13  * - Not all IP options are supported.
  14  * - Are ICMP handles real handles, i.e. inheritable and all? There might be some
  15  *   more work to do here, including server side stuff with synchronization.
  16  * - Is it correct to use malloc for the internal buffer, for allocating the
  17  *   handle's structure?
  18  * - This API should probably be thread safe. Is it really?
  19  * - Using the winsock functions has not been tested.
  20  */
  21
  22 #include "config.h"
  23
  24 #include <sys/types.h>
  25 #ifdef HAVE_SYS_SOCKET_H
  26 # include <sys/socket.h>
  27 #endif
  28 #include <netdb.h>
  29 #include <netinet/in_systm.h>
  30 #ifdef HAVE_NETINET_IN_H
  31 # include <netinet/in.h>
  32 #endif
  33
  34 #include <sys/time.h>
  35 #include <malloc.h>
  36 #include <string.h>
  37 #include <errno.h>
  38 #include <unistd.h>
  39 #ifdef HAVE_ARPA_INET_H
  40 # include <arpa/inet.h>
  41 #endif
  42
  43 #include "windef.h"
  44 #include "winbase.h"
  45 #ifdef ICMP_WIN
  46 #include "winsock.h"
  47 #endif
  48
  49 #include "winerror.h"
  50 #include "wine/ipexport.h"
  51 #include "wine/icmpapi.h"
  52 #include "debugtools.h"
  53
  54 /* Set up endiannes macros for the ip and ip_icmp BSD headers */
  55 #ifndef BIG_ENDIAN
  56 #define BIG_ENDIAN       4321
  57 #endif
  58 #ifndef LITTLE_ENDIAN
  59 #define LITTLE_ENDIAN    1234
  60 #endif
  61 #ifndef BYTE_ORDER
  62 #ifdef WORDS_BIGENDIAN
  63 #define BYTE_ORDER       BIG_ENDIAN
  64 #else
  65 #define BYTE_ORDER       LITTLE_ENDIAN
  66 #endif
  67 #endif /* BYTE_ORDER */
  68
  69 #define u_int16_t  WORD
  70 #define u_int32_t  DWORD
  71
  72 /* These are BSD headers. We use these here because they are needed on
  73  * libc5 Linux systems. On other platforms they are usually simply more
  74  * complete than the native stuff, and cause less portability problems
  75  * so we use them anyway.
  76  */
  77 #include "ip.h"
  78 #include "ip_icmp.h"
  79
  80
  81 DEFAULT_DEBUG_CHANNEL(icmp)
  82
  83 /* Define the following macro to use the winsock functions */
  84 /*#define ICMP_WIN*/
  85
  86 #ifdef ICMP_WIN
  87 /* FIXME: should we include winsock.h ???*/
  88 SOCKET WINAPI WINSOCK_socket(INT af, INT type, INT protocol);
  89 INT WINAPI WINSOCK_sendto(SOCKET s, char *buf, INT len, INT flags, struct sockaddr *to, INT tolen);
  90 INT WINAPI WINSOCK_recvfrom(SOCKET s, char *buf,INT len, INT flags, struct sockaddr *from, INT *fromlen32);
  91 INT WINAPI WINSOCK_shutdown(SOCKET s, INT how);
  92 #endif
  93
  94
  95 #ifdef ICMP_WIN
  96 #define ISOCK_SOCKET                SOCKET
  97 #define ISOCK_ISVALID(a)            ((a)!=INVALID_SOCKET)
  98 #define ISOCK_getsockopt(a,b,c,d,e) WINSOCK_getsockopt(a,b,c,d,e)
  99 #define ISOCK_recvfrom(a,b,c,d,e,f) WINSOCK_recvfrom(a,b,c,d,e,f)
 100 #define ISOCK_select(a,b,c,d,e)     WINSOCK_select(a,b,c,d,e)
 101 #define ISOCK_sendto(a,b,c,d,e,f)   WINSOCK_sendto(a,b,c,d,e,f)
 102 #define ISOCK_setsockopt(a,b,c,d,e) WINSOCK_setsockopt(a,b,c,d,e)
 103 #define ISOCK_shutdown(a,b)         WINSOCK_shutdown(a,b)
 104 #define ISOCK_socket(a,b,c)         WINSOCK_socket(a,b,c)
 105 #else
 106 #define ISOCK_SOCKET                int
 107 #define ISOCK_ISVALID(a)            ((a)>=0)
 108 #define ISOCK_getsockopt(a,b,c,d,e) getsockopt(a,b,c,d,e)
 109 #define ISOCK_recvfrom(a,b,c,d,e,f) recvfrom(a,b,c,d,e,f)
 110 #define ISOCK_select(a,b,c,d,e)     select(a,b,c,d,e)
 111 #define ISOCK_setsockopt(a,b,c,d,e) setsockopt(a,b,c,d,e)
 112 #define ISOCK_sendto(a,b,c,d,e,f)   sendto(a,b,c,d,e,f)
 113 #define ISOCK_shutdown(a,b)         shutdown(a,b)
 114 #define ISOCK_socket(a,b,c)         socket(a,b,c)
 115 #endif
 116
 117 typedef struct {
 118     ISOCK_SOCKET sid;
 119     IP_OPTION_INFORMATION default_opts;
 120 } icmp_t;
 121
 122 #define IP_OPTS_UNKNOWN     0
 123 #define IP_OPTS_DEFAULT     1
 124 #define IP_OPTS_CUSTOM      2
 125
 126 /* The sequence number is unique process wide, so that all threads
 127  * have a distinct sequence number.
 128  */
 129 static LONG icmp_sequence=0;
 130
 131 static int in_cksum(u_short *addr, int len)
 132 {
 133     int nleft=len;
 134     u_short *w = addr;
 135     int sum = 0;
 136     u_short answer = 0;
 137
 138     while (nleft > 1) {
 139         sum += *w++;
 140         nleft -= 2;
 141     }
 142
 143     if (nleft == 1) {
 144         *(u_char *)(&answer) = *(u_char *)w;
 145         sum += answer;
 146     }
 147
 148     sum = (sum >> 16) + (sum & 0xffff);
 149     sum  += (sum >> 16);
 150     answer = ~sum;
 151     return(answer);
 152 }
 153
 154
 155
 156 /*
 157  * Exported Routines.
 158  */
 159
 160 HANDLE WINAPI IcmpCreateFile(VOID)
 161 {
 162     icmp_t* icp;
 163
 164     ISOCK_SOCKET sid=ISOCK_socket(AF_INET,SOCK_RAW,IPPROTO_ICMP);
 165     if (!ISOCK_ISVALID(sid)) {
 166         MESSAGE("WARNING: Trying to use ICMP will fail unless running as root\n");
 167         SetLastError(ERROR_ACCESS_DENIED);
 168         return INVALID_HANDLE_VALUE;
 169     }
 170
 171     icp=malloc(sizeof(*icp));
 172     if (icp==NULL) {
 173         SetLastError(IP_NO_RESOURCES);
 174         return INVALID_HANDLE_VALUE;
 175     }
 176     icp->sid=sid;
 177     icp->default_opts.OptionsSize=IP_OPTS_UNKNOWN;
 178     return (HANDLE)icp;
 179 }
 180
 181
 182 BOOL WINAPI IcmpCloseHandle(HANDLE  IcmpHandle)
 183 {
 184     icmp_t* icp=(icmp_t*)IcmpHandle;
 185     if (IcmpHandle==INVALID_HANDLE_VALUE) {
 186         /* FIXME: in fact win98 seems to ignore the handle value !!! */
 187         SetLastError(ERROR_INVALID_HANDLE);
 188         return FALSE;
 189     }
 190
 191     ISOCK_shutdown(icp->sid,2);
 192     free(icp);
 193     return TRUE;
 194 }
 195
 196
 197 DWORD WINAPI IcmpSendEcho(
 198     HANDLE                   IcmpHandle,
 199     IPAddr                   DestinationAddress,
 200     LPVOID                   RequestData,
 201     WORD                     RequestSize,
 202     PIP_OPTION_INFORMATION   RequestOptions,
 203     LPVOID                   ReplyBuffer,
 204     DWORD                    ReplySize,
 205     DWORD                    Timeout
 206     )
 207 {
 208     icmp_t* icp=(icmp_t*)IcmpHandle;
 209     unsigned char* reqbuf;
 210     int reqsize;
 211
 212     struct icmp_echo_reply* ier;
 213     struct ip* ip_header;
 214     struct icmp* icmp_header;
 215     char* endbuf;
 216     int ip_header_len;
 217     int maxlen;
 218     fd_set fdr;
 219     struct timeval timeout,send_time,recv_time;
 220     struct sockaddr_in addr;
 221     int addrlen;
 222     unsigned short id,seq,cksum;
 223     int res;
 224
 225     if (IcmpHandle==INVALID_HANDLE_VALUE) {
 226         /* FIXME: in fact win98 seems to ignore the handle value !!! */
 227         SetLastError(ERROR_INVALID_HANDLE);
 228         return 0;
 229     }
 230
 231     if (ReplySize<sizeof(ICMP_ECHO_REPLY)+ICMP_MINLEN) {
 232         SetLastError(IP_BUF_TOO_SMALL);
 233         return 0;
 234     }
 235     /* check the request size against SO_MAX_MSG_SIZE using getsockopt */
 236
 237     /* Prepare the request */
 238     id=getpid() & 0xFFFF;
 239     seq=InterlockedIncrement(&icmp_sequence) & 0xFFFF;
 240
 241     reqsize=ICMP_MINLEN+RequestSize;
 242     reqbuf=malloc(reqsize);
 243     if (reqbuf==NULL) {
 244         SetLastError(ERROR_OUTOFMEMORY);
 245         return 0;
 246     }
 247
 248     icmp_header=(struct icmp*)reqbuf;
 249     icmp_header->icmp_type=ICMP_ECHO;
 250     icmp_header->icmp_code=0;
 251     icmp_header->icmp_cksum=0;
 252     icmp_header->icmp_id=id;
 253     icmp_header->icmp_seq=seq;
 254     memcpy(reqbuf+ICMP_MINLEN, RequestData, RequestSize);
 255     icmp_header->icmp_cksum=cksum=in_cksum((u_short*)reqbuf,reqsize);
 256
 257     addr.sin_family=AF_INET;
 258     addr.sin_addr.s_addr=DestinationAddress;
 259     addr.sin_port=0;
 260
 261     if (RequestOptions!=NULL) {
 262         int val;
 263         if (icp->default_opts.OptionsSize==IP_OPTS_UNKNOWN) {
 264             int len;
 265             /* Before we mess with the options, get the default values */
 266             len=sizeof(val);
 267             ISOCK_getsockopt(icp->sid,IPPROTO_IP,IP_TTL,(char *)&val,&len);
 268             icp->default_opts.Ttl=val;
 269
 270             len=sizeof(val);
 271             ISOCK_getsockopt(icp->sid,IPPROTO_IP,IP_TOS,(char *)&val,&len);
 272             icp->default_opts.Tos=val;
 273             /* FIXME: missing: handling of IP 'flags', and all the other options */
 274         }
 275
 276         val=RequestOptions->Ttl;
 277         ISOCK_setsockopt(icp->sid,IPPROTO_IP,IP_TTL,(char *)&val,sizeof(val));
 278         val=RequestOptions->Tos;
 279         ISOCK_setsockopt(icp->sid,IPPROTO_IP,IP_TOS,(char *)&val,sizeof(val));
 280         /* FIXME:  missing: handling of IP 'flags', and all the other options */
 281
 282         icp->default_opts.OptionsSize=IP_OPTS_CUSTOM;
 283     } else if (icp->default_opts.OptionsSize==IP_OPTS_CUSTOM) {
 284         int val;
 285
 286         /* Restore the default options */
 287         val=icp->default_opts.Ttl;
 288         ISOCK_setsockopt(icp->sid,IPPROTO_IP,IP_TTL,(char *)&val,sizeof(val));
 289         val=icp->default_opts.Tos;
 290         ISOCK_setsockopt(icp->sid,IPPROTO_IP,IP_TOS,(char *)&val,sizeof(val));
 291         /* FIXME: missing: handling of IP 'flags', and all the other options */
 292
 293         icp->default_opts.OptionsSize=IP_OPTS_DEFAULT;
 294     }
 295
 296     /* Get ready for receiving the reply
 297      * Do it before we send the request to minimize the risk of introducing delays
 298      */
 299     FD_ZERO(&fdr);
 300     FD_SET(icp->sid,&fdr);
 301     timeout.tv_sec=Timeout/1000;
 302     timeout.tv_usec=(Timeout % 1000)*1000;
 303     addrlen=sizeof(addr);
 304     ier=ReplyBuffer;
 305     ip_header=ReplyBuffer+sizeof(ICMP_ECHO_REPLY);
 306     endbuf=ReplyBuffer+ReplySize;
 307     maxlen=ReplySize-sizeof(ICMP_ECHO_REPLY);
 308
 309     /* Send the packet */
 310     TRACE("Sending %d bytes (RequestSize=%d) to %s\n", reqsize, RequestSize, inet_ntoa(addr.sin_addr));
 311 #if 0
 312     if (TRACE_ON(icmp)){
 313         unsigned char* buf=(unsigned char*)reqbuf;
 314         int i;
 315         printf("Output buffer:\n");
 316         for (i=0;i<reqsize;i++)
 317             printf("%2x,", buf[i]);
 318         printf("\n");
 319     }
 320 #endif
 321
 322     gettimeofday(&send_time,NULL);
 323     res=ISOCK_sendto(icp->sid, reqbuf, reqsize, 0, (struct sockaddr*)&addr, sizeof(addr));
 324     free(reqbuf);
 325     if (res<0) {
 326         if (errno==EMSGSIZE)
 327             SetLastError(IP_PACKET_TOO_BIG);
 328         else {
 329             switch (errno) {
 330             case ENETUNREACH:
 331                 SetLastError(IP_DEST_NET_UNREACHABLE);
 332                 break;
 333             case EHOSTUNREACH:
 334                 SetLastError(IP_DEST_NET_UNREACHABLE);
 335                 break;
 336             default:
 337                 TRACE("unknown error: errno=%d\n",errno);
 338                 SetLastError(ERROR_UNKNOWN);
 339             }
 340         }
 341         return 0;
 342     }
 343
 344     /* Get the reply */
 345     ip_header_len=0; /* because gcc was complaining */
 346     while ((res=ISOCK_select(icp->sid+1,&fdr,NULL,NULL,&timeout))>0) {
 347         gettimeofday(&recv_time,NULL);
 348         res=ISOCK_recvfrom(icp->sid, (char*)ip_header, maxlen, 0, (struct sockaddr*)&addr,&addrlen);
 349         TRACE("received %d bytes from %s\n",res, inet_ntoa(addr.sin_addr));
 350         ier->Status=IP_REQ_TIMED_OUT;
 351
 352         /* Check whether we should ignore this packet */
 353         if ((ip_header->ip_p==IPPROTO_ICMP) && (res>=sizeof(struct ip)+ICMP_MINLEN)) {
 354             ip_header_len=ip_header->ip_hl << 2;
 355             icmp_header=(struct icmp*)(((char*)ip_header)+ip_header_len);
 356             TRACE("received an ICMP packet of type,code=%d,%d\n",icmp_header->icmp_type,icmp_header->icmp_code);
 357             if (icmp_header->icmp_type==ICMP_ECHOREPLY) {
 358                 if ((icmp_header->icmp_id==id) && (icmp_header->icmp_seq==seq))
 359                     ier->Status=IP_SUCCESS;
 360             } else {
 361                 switch (icmp_header->icmp_type) {
 362                 case ICMP_UNREACH:
 363                     switch (icmp_header->icmp_code) {
 364                     case ICMP_UNREACH_HOST:
 365 #ifdef ICMP_UNREACH_HOST_UNKNOWN
 366                     case ICMP_UNREACH_HOST_UNKNOWN:
 367 #endif
 368 #ifdef ICMP_UNREACH_ISOLATED
 369                     case ICMP_UNREACH_ISOLATED:
 370 #endif
 371 #ifdef ICMP_UNREACH_HOST_PROHIB
 372                     case ICMP_UNREACH_HOST_PROHIB:
 373 #endif
 374 #ifdef ICMP_UNREACH_TOSHOST
 375                     case ICMP_UNREACH_TOSHOST:
 376 #endif
 377                         ier->Status=IP_DEST_HOST_UNREACHABLE;
 378                         break;
 379                     case ICMP_UNREACH_PORT:
 380                         ier->Status=IP_DEST_PORT_UNREACHABLE;
 381                         break;
 382                     case ICMP_UNREACH_PROTOCOL:
 383                         ier->Status=IP_DEST_PROT_UNREACHABLE;
 384                         break;
 385                     case ICMP_UNREACH_SRCFAIL:
 386                         ier->Status=IP_BAD_ROUTE;
 387                         break;
 388                     default:
 389                         ier->Status=IP_DEST_NET_UNREACHABLE;
 390                     }
 391                     break;
 392                 case ICMP_TIMXCEED:
 393                     if (icmp_header->icmp_code==ICMP_TIMXCEED_REASS)
 394                         ier->Status=IP_TTL_EXPIRED_REASSEM;
 395                     else
 396                         ier->Status=IP_TTL_EXPIRED_TRANSIT;
 397                     break;
 398                 case ICMP_PARAMPROB:
 399                     ier->Status=IP_PARAM_PROBLEM;
 400                     break;
 401                 case ICMP_SOURCEQUENCH:
 402                     ier->Status=IP_SOURCE_QUENCH;
 403                     break;
 404                 }
 405                 if (ier->Status!=IP_REQ_TIMED_OUT) {
 406                     struct ip* rep_ip_header;
 407                     struct icmp* rep_icmp_header;
 408                     /* The ICMP header size of all the packets we accept is the same */
 409                     rep_ip_header=(struct ip*)(((char*)icmp_header)+ICMP_MINLEN);
 410                     rep_icmp_header=(struct icmp*)(((char*)rep_ip_header)+(rep_ip_header->ip_hl << 2));
 411
 412                     /* Make sure that this is really a reply to our packet */
 413                     if (ip_header_len+ICMP_MINLEN+(rep_ip_header->ip_hl << 2)+ICMP_MINLEN>ip_header->ip_len) {
 414                         ier->Status=IP_REQ_TIMED_OUT;
 415                     } else if ((rep_icmp_header->icmp_type!=ICMP_ECHO) ||
 416                         (rep_icmp_header->icmp_code!=0) ||
 417                         (rep_icmp_header->icmp_id!=id) ||
 418                         (rep_icmp_header->icmp_seq!=seq) ||
 419                         (rep_icmp_header->icmp_cksum!=cksum)) {
 420                         /* This was not a reply to one of our packets after all */
 421                         TRACE("skipping type,code=%d,%d id,seq=%d,%d cksum=%d\n",
 422                             rep_icmp_header->icmp_type,rep_icmp_header->icmp_code,
 423                             rep_icmp_header->icmp_id,rep_icmp_header->icmp_seq,
 424                             rep_icmp_header->icmp_cksum);
 425                         TRACE("expected type,code=8,0 id,seq=%d,%d cksum=%d\n",
 426                             id,seq,
 427                             cksum);
 428                         ier->Status=IP_REQ_TIMED_OUT;
 429                     }
 430                 }
 431             }
 432         }
 433
 434         if (ier->Status==IP_REQ_TIMED_OUT) {
 435             /* This packet was not for us.
 436              * Decrease the timeout so that we don't enter an endless loop even
 437              * if we get flooded with ICMP packets that are not for us.
 438              */
 439             timeout.tv_sec=Timeout/1000-(recv_time.tv_sec-send_time.tv_sec);
 440             timeout.tv_usec=(Timeout % 1000)*1000+send_time.tv_usec-(recv_time.tv_usec-send_time.tv_usec);
 441             if (timeout.tv_usec<0) {
 442                 timeout.tv_usec+=1000000;
 443                 timeout.tv_sec--;
 444             }
 445             continue;
 446         } else {
 447             /* This is a reply to our packet */
 448             memcpy(&ier->Address,&ip_header->ip_src,sizeof(IPAddr));
 449             /* Status is already set */
 450             ier->RoundTripTime=(recv_time.tv_sec-send_time.tv_sec)*1000+(recv_time.tv_usec-send_time.tv_usec)/1000;
 451             ier->DataSize=res-ip_header_len-ICMP_MINLEN;
 452             ier->Reserved=0;
 453             ier->Data=endbuf-ier->DataSize;
 454             memmove(ier->Data,((char*)ip_header)+ip_header_len+ICMP_MINLEN,ier->DataSize);
 455             ier->Options.Ttl=ip_header->ip_ttl;
 456             ier->Options.Tos=ip_header->ip_tos;
 457             ier->Options.Flags=ip_header->ip_off >> 13;
 458             ier->Options.OptionsSize=ip_header_len-sizeof(struct ip);
 459             if (ier->Options.OptionsSize!=0) {
 460                 ier->Options.OptionsData=ier->Data-ier->Options.OptionsSize;
 461                 /* FIXME: We are supposed to rearrange the option's 'source route' data */
 462                 memmove(ier->Options.OptionsData,((char*)ip_header)+ip_header_len,ier->Options.OptionsSize);
 463                 endbuf=ier->Options.OptionsData;
 464             } else {
 465                 ier->Options.OptionsData=NULL;
 466                 endbuf=ier->Data;
 467             }
 468
 469             /* Prepare for the next packet */
 470             ier++;
 471             ip_header=(struct ip*)(((char*)ip_header)+sizeof(ICMP_ECHO_REPLY));
 472             maxlen=endbuf-(char*)ip_header;
 473
 474             /* Check out whether there is more but don't wait this time */
 475             timeout.tv_sec=0;
 476             timeout.tv_usec=0;
 477         }
 478         FD_ZERO(&fdr);
 479         FD_SET(icp->sid,&fdr);
 480     }
 481     res=ier-(ICMP_ECHO_REPLY*)ReplyBuffer;
 482     if (res==0)
 483         SetLastError(IP_REQ_TIMED_OUT);
 484     TRACE("received %d replies\n",res);
 485     return res;
 486 }
 487
 488 /*
 489  * Copyright (c) 1989 The Regents of the University of California.
 490  * All rights reserved.
 491  *
 492  * This code is derived from software contributed to Berkeley by
 493  * Mike Muuss.
 494  *
 495  * Redistribution and use in source and binary forms, with or without
 496  * modification, are permitted provided that the following conditions
 497  * are met:
 498  * 1. Redistributions of source code must retain the above copyright
 499  *    notice, this list of conditions and the following disclaimer.
 500  * 2. Redistributions in binary form must reproduce the above copyright
 501  *    notice, this list of conditions and the following disclaimer in the
 502  *    documentation and/or other materials provided with the distribution.
 503  * 3. All advertising materials mentioning features or use of this software
 504  *    must display the following acknowledgement:
 505  *      This product includes software developed by the University of
 506  *      California, Berkeley and its contributors.
 507  * 4. Neither the name of the University nor the names of its contributors
 508  *    may be used to endorse or promote products derived from this software
 509  *    without specific prior written permission.
 510  *
 511  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 512  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 513  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 514  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 515  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 516  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 517  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 518  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 519  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 520  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 521  * SUCH DAMAGE.
 522  *
 523  */