2 (c) Marc Welz 2000, released under GPL, tested under Linux 2.2.17
4 Most of the stuff cribbed from the nbd package written by Pavel Machek
6 Unfortunately quite slow since zlib has to decompress all the stuff between
7 seeks, so only suited to smaller files
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
14 dd if=/dev/zero of=/tmp/image bs=1024 count=1024
16 mount -o loop /tmp/image /mnt/
21 gznbd /dev/nbd0 /tmp/image.gz
23 gznbd does not background, from another terminal type
25 mount -o ro,nocheck /dev/nbd0 /mnt/
30 ro is important, since writes will fail horribly and nochecks
31 speeds the mount up nicely
44 #include <sys/ioctl.h>
45 #include <sys/types.h>
46 #include <sys/socket.h>
48 #include <netinet/in.h>
50 /* asm/types defines __u??, at least on my system */
51 #include <asm/types.h>
53 #define MY_NAME "gznbd"
55 /* these headers take care of endianness */
56 #include "../config.h"
57 #include "../cliserv.h"
61 /* don't ask me why this value, I only copied it */
62 #define CHUNK BLOCK*20
65 int main(int argc, char **argv)
74 struct nbd_request request;
75 struct nbd_reply reply;
82 printf("Usage: %s nbdevice gzfile [size]\n",argv[0]);
86 gz=gzopen(argv[2], "rb");
88 fprintf(stderr,"%s: unable open compressed file %s\n",argv[0],argv[2]);
94 if((size==0)||(size%BLOCK)){
95 fprintf(stderr,"%s: %s does not appear to be a valid size\n",argv[0],argv[3]);
98 printf("%s: file=%s, size=%Ld\n",argv[0],argv[2],size);
104 printf("%s: file=%s, seeking, ",argv[0],argv[2]);
107 /* expensive seek to get file size */
108 while(BLOCK==(result=gzread(gz,buffer,BLOCK))){
113 printf("size=%Ld\n",size);
117 fprintf(stderr,"%s: read failed: %s\n",argv[0],gzerror(gz,&gzerr));
119 fprintf(stderr,"%s: incomplete last read, file has to be a multiple of %d\n",argv[0],BLOCK);
125 fprintf(stderr,"%s: unable to rewind gzfile\n",argv[0]);
131 if(socketpair(AF_UNIX, SOCK_STREAM, 0, pr)){
132 fprintf(stderr,"%s: unable to create socketpair: %s\n",argv[0],strerror(errno));
138 fprintf(stderr,"%s: unable to fork: %s\n",argv[0],strerror(errno));
148 nbd=open(argv[1], O_RDWR);
150 fprintf(stderr,"%s: unable to open %s: %s\n",argv[0],argv[1],strerror(errno));
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));
159 ioctl(nbd, NBD_CLEAR_SOCK);
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));
166 if(ioctl(nbd,NBD_DO_IT)<0){
167 fprintf(stderr,"%s: block device %s terminated: %s\n",argv[0],argv[1],strerror(errno));
170 ioctl(nbd, NBD_CLEAR_QUE);
171 ioctl(nbd, NBD_CLEAR_SOCK);
178 /* only parent here, child always exits */
183 reply.magic=htonl(NBD_REPLY_MAGIC);
184 reply.error=htonl(0);
188 if(read(sk,&request,sizeof(request))!=sizeof(request)){
189 fprintf(stderr,"%s: incomplete request\n",argv[0]);
192 memcpy(reply.handle,request.handle,sizeof(reply.handle));
194 len=ntohl(request.len);
195 from=ntohll(request.from);
198 fprintf(stderr,"%s: len=%d, from=%Ld\n",argv[0],len,from);
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 ? */
206 if(ntohl(request.type)){
207 fprintf(stderr,"%s: unsupported write request\n",argv[0]);
208 reply.error=htonl(EROFS);
211 if(len+sizeof(struct nbd_reply)>CHUNK){
212 fprintf(stderr,"%s: request too long\n",argv[0]);
213 reply.error=htonl(EIO);
217 fprintf(stderr,"%s: request outside range\n",argv[0]);
218 reply.error=htonl(EIO);
221 if(reply.error==htonl(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);
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));