gznbd/gznbd.c

   1 /*
   2    (c) Marc Welz 2000, released under GPL, tested under Linux 2.2.17
   3
   4    Most of the stuff cribbed from the nbd package written by Pavel Machek
   5
   6    Unfortunately quite slow since zlib has to decompress all the stuff between
   7    seeks, so only suited to smaller files
   8
   9    Could be a neat way to do userland encryption/steganography if you have
  10    a crypto library which has a stdiolike interface to replace zlib
  11
  12    Usage
  13
  14      dd if=/dev/zero of=/tmp/image bs=1024 count=1024
  15      mke2fs -f /tmp/image
  16      mount -o loop /tmp/image /mnt/
  17      cp /bin/ls /mnt/
  18      umount /mnt
  19      sync
  20      gzip -9 /tmp/image
  21      gznbd /dev/nbd0 /tmp/image.gz
  22
  23    gznbd does not background, from another terminal type
  24
  25      mount -o ro,nocheck /dev/nbd0 /mnt/
  26      cd /mnt
  27      ls
  28      df
  29
  30    ro is important, since writes will fail horribly and nochecks
  31    speeds the mount up nicely
  32
  33  */
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <zlib.h>
  38 #include <errno.h>
  39 #include <string.h>
  40 #include <fcntl.h>
  41 #include <unistd.h>
  42
  43 #include <sys/ioctl.h>
  44 #include <sys/types.h>
  45 #include <sys/socket.h>
  46
  47 #include <netinet/in.h>
  48
  49 /* asm/types defines __u??, at least on my system */
  50 #include <asm/types.h>
  51
  52 #define u32 __u32
  53 #define u64 __u64
  54
  55 /* these headers take care of endianness */
  56 #include "../config.h"
  57 #include "../cliserv.h"
  58
  59 #define BLOCK 1024
  60
  61 /* don't ask me why this value, I only copied it */
  62 #define CHUNK BLOCK*20
  63
  64
  65 int main(int argc, char **argv)
  66 {
  67   int pr[2];
  68   int sk;
  69   int nbd;
  70   gzFile *gz;
  71   int gzerr;
  72
  73   char chunk[CHUNK];
  74   struct nbd_request request;
  75   struct nbd_reply reply;
  76
  77   u64 size;
  78   u64 from;
  79   u32 len;
  80
  81   if(argc<3){
  82     printf("Usage: %s nbdevice gzfile [size]\n",argv[0]);
  83     exit(1);
  84   }
  85
  86   gz=gzopen(argv[2], "rb");
  87   if(gz==NULL){
  88     fprintf(stderr,"%s: unable open compressed file %s\n",argv[0],argv[2]);
  89     exit(1);
  90   }
  91
  92   if(argc>3){
  93     size=atol(argv[3]);
  94     if((size==0)||(size%BLOCK)){
  95       fprintf(stderr,"%s: %s does not appear to be a valid size\n",argv[0],argv[3]);
  96       exit(1);
  97     }
  98     printf("%s: file=%s, size=%Ld\n",argv[0],argv[2],size);
  99   } else {
 100     char buffer[BLOCK];
 101     int result;
 102
 103     size=0;
 104     printf("%s: file=%s, seeking, ",argv[0],argv[2]);
 105     fflush(stdout);
 106
 107     /* expensive seek to get file size */
 108     while(BLOCK==(result=gzread(gz,buffer,BLOCK))){
 109       size+=BLOCK;
 110     }
 111
 112     if(result==0){
 113       printf("size=%Ld\n",size);
 114     } else {
 115       printf("failed\n");
 116       if(result<0){
 117         fprintf(stderr,"%s: read failed: %s\n",argv[0],gzerror(gz,&gzerr));
 118       } else {
 119         fprintf(stderr,"%s: incomplete last read, file has to be a multiple of %d\n",argv[0],BLOCK);
 120       }
 121       exit(1);
 122     }
 123
 124     if(gzrewind(gz)!=0){
 125       fprintf(stderr,"%s: unable to rewind gzfile\n",argv[0]);
 126       exit(1);
 127     }
 128
 129   }
 130
 131   if(socketpair(AF_UNIX, SOCK_STREAM, 0, pr)){
 132     fprintf(stderr,"%s: unable to create socketpair: %s\n",argv[0],strerror(errno));
 133     exit(1);
 134   }
 135
 136   switch(fork()){
 137     case -1 :
 138       fprintf(stderr,"%s: unable to fork: %s\n",argv[0],strerror(errno));
 139       exit(1);
 140       break;
 141     case 0 : /* child */
 142       gzclose(gz);
 143
 144       close(pr[0]);
 145
 146       sk=pr[1];
 147
 148       nbd=open(argv[1], O_RDWR);
 149       if(nbd<0){
 150         fprintf(stderr,"%s: unable to open %s: %s\n",argv[0],argv[1],strerror(errno));
 151         exit(1);
 152       }
 153
 154       if(ioctl(nbd,NBD_SET_SIZE,size)<0){
 155         fprintf(stderr,"%s: failed to set size for %s: %s\n",argv[0],argv[1],strerror(errno));
 156         exit(1);
 157       }
 158
 159       ioctl(nbd, NBD_CLEAR_SOCK);
 160
 161       if(ioctl(nbd,NBD_SET_SOCK,sk)<0){
 162         fprintf(stderr,"%s: failed to set socket for %s: %s\n",argv[0],argv[1],strerror(errno));
 163         exit(1);
 164       }
 165
 166       if(ioctl(nbd,NBD_DO_IT)<0){
 167         fprintf(stderr,"%s: block device %s terminated: %s\n",argv[0],argv[1],strerror(errno));
 168       }
 169
 170       ioctl(nbd, NBD_CLEAR_QUE);
 171       ioctl(nbd, NBD_CLEAR_SOCK);
 172
 173       exit(0);
 174
 175       break;
 176   }
 177
 178   /* only parent here, child always exits */
 179
 180   close(pr[1]);
 181   sk=pr[0];
 182
 183   reply.magic=htonl(NBD_REPLY_MAGIC);
 184   reply.error=htonl(0);
 185
 186   while(1){
 187
 188     if(read(sk,&request,sizeof(request))!=sizeof(request)){
 189       fprintf(stderr,"%s: incomplete request\n",argv[0]);
 190     }
 191
 192     memcpy(reply.handle,request.handle,sizeof(reply.handle));
 193
 194     len=ntohl(request.len);
 195     from=ntohll(request.from);
 196
 197 #ifdef TRACE
 198 fprintf(stderr,"%s: len=%d, from=%Ld\n",argv[0],len,from);
 199 #endif
 200
 201     if(request.magic!=htonl(NBD_REQUEST_MAGIC)){
 202       fprintf(stderr,"%s: bad magic\n",argv[0]);
 203       reply.error=htonl(EIO); /* is that the right way of doing things ? */
 204     }
 205
 206     if(ntohl(request.type)){
 207       fprintf(stderr,"%s: unsupported write request\n",argv[0]);
 208       reply.error=htonl(EROFS);
 209     }
 210
 211     if(len+sizeof(struct nbd_reply)>CHUNK){
 212       fprintf(stderr,"%s: request too long\n",argv[0]);
 213       reply.error=htonl(EIO);
 214     }
 215
 216     if(len+from>size){
 217       fprintf(stderr,"%s: request outside range\n",argv[0]);
 218       reply.error=htonl(EIO);
 219     }
 220
 221     if(reply.error==htonl(0)){
 222       gzseek(gz,from,0);
 223       if(gzread(gz,chunk+sizeof(struct nbd_reply),len)!=len){
 224         fprintf(stderr,"%s: unable to read\n",argv[0]);
 225         reply.error=htonl(EIO);
 226         len=0;
 227       }
 228     } else {
 229       len=0;
 230     }
 231
 232     memcpy(chunk,&reply,sizeof(struct nbd_reply));
 233     if(write(sk,chunk,len+sizeof(struct nbd_reply))!=(len+sizeof(struct nbd_reply))){
 234       fprintf(stderr,"%s: write failed: %s\n",argv[0],strerror(errno));
 235     }
 236   }
 237
 238   gzclose(gz);
 239
 240   return 0;
 241 }