tools/netblocksrv.cpp

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <string.h>
   4 #include <sys/stat.h>
   5 #include <fcntl.h>
   6 #include <unistd.h>
   7 #include <sys/types.h>
   8 #include <sys/socket.h>
   9 #include <netinet/in.h>
  10
  11 #ifndef O_BINARY
  12 #define O_BINARY 0
  13 #endif
  14
  15 typedef struct blockdevice {
  16         int id;
  17         int filefd;
  18         off_t size;
  19 } blockdevice;
  20
  21 static blockdevice *dev;
  22 static int sockfd;
  23
  24 #define BLOCKSIZE 512
  25
  26 #define MAGIC 0x14983543
  27
  28 typedef struct message {
  29         int magic;
  30         int block_id;
  31         int command;
  32         int arg;
  33         int arg2;
  34         char data[0];
  35 } message;
  36
  37 #define CMD_NULL 0
  38 #define CMD_GETSIZE 1
  39 #define CMD_READBLOCK 2
  40 #define CMD_WRITEBLOCK 3
  41
  42 static int validate_message(message *msg, int len)
  43 {
  44         if(len < sizeof(message))
  45                 return 0;
  46
  47         // validate the message
  48         if(ntohl(msg->magic) != MAGIC)
  49                 return 0;
  50         if(ntohl(msg->block_id) != 0)
  51                 return 0;
  52
  53         switch(ntohl(msg->command)) {
  54                 case CMD_NULL:
  55                 case ~CMD_NULL:
  56                 case CMD_GETSIZE:
  57                 case ~CMD_GETSIZE:
  58                 case CMD_READBLOCK:
  59                 case ~CMD_READBLOCK:
  60                 case CMD_WRITEBLOCK:
  61                 case ~CMD_WRITEBLOCK:
  62                         break;
  63                 default:
  64                         return 0;
  65         }
  66
  67         return 1;
  68 }
  69
  70 static int net_loop()
  71 {
  72         struct sockaddr_in from_addr;
  73         socklen_t slen = sizeof(struct sockaddr);
  74         char buf[4096];
  75         int err;
  76         int reply_size;
  77
  78         for(;;) {
  79                 err = recvfrom(sockfd, buf, sizeof(buf), 0, (struct sockaddr *)&from_addr, &slen);
  80                 if(err < 0) {
  81                         printf("error reading from socket\n");
  82                         return -1;
  83                 }
  84
  85                 message *msg = (message *)buf;
  86
  87                 if(!validate_message(msg, err))
  88                         continue;
  89
  90 //              printf("got message, command %d\n", ntohl(msg->command));
  91                 reply_size = sizeof(message);
  92                 switch(ntohl(msg->command)) {
  93                         case CMD_NULL:
  94                                 // respond
  95                                 msg->command = htonl(~CMD_NULL);
  96                                 break;
  97                         case CMD_GETSIZE:
  98                                 msg->command = htonl(~CMD_GETSIZE);
  99                                 printf("GETSIZE %d\n", htonl(dev->size));
 100                                 *(int *)&msg->data[0] = htonl(dev->size);
 101                                 reply_size += 4;
 102                                 break;
 103                         case CMD_READBLOCK:
 104                                 msg->command = htonl(~CMD_READBLOCK);
 105                                 printf("R %d %d\n", ntohl(msg->arg), ntohl(msg->arg2));
 106                                 if(ntohl(msg->arg) + ntohl(msg->arg2) <= dev->size) {
 107                                         lseek(dev->filefd, ntohl(msg->arg), SEEK_SET);
 108                                         read(dev->filefd, &msg->data[0], ntohl(msg->arg2));
 109                                 } else {
 110                                         printf("CMD_READBLOCK: invalid offset %d and size %d\n", ntohl(msg->arg), ntohl(msg->arg2));
 111                                         memset(&msg->data[0], 0, ntohl(msg->arg2));
 112                                 }
 113                                 reply_size += BLOCKSIZE;
 114                                 break;
 115                         case CMD_WRITEBLOCK:
 116                                 msg->command = htonl(~CMD_WRITEBLOCK);
 117                                 printf("W %d %d\n", ntohl(msg->arg), ntohl(msg->arg2));
 118                                 if(ntohl(msg->arg) + ntohl(msg->arg2) <= dev->size) {
 119                                         lseek(dev->filefd, ntohl(msg->arg), SEEK_SET);
 120                                         write(dev->filefd, &msg->data[0], ntohl(msg->arg2));
 121                                 } else {
 122                                         printf("CMD_WRITEBLOCK: invalid offset %d and size %d\n", ntohl(msg->arg), ntohl(msg->arg2));
 123                                 }
 124                                 break;
 125                         default:
 126                                 continue;
 127                 }
 128
 129                 // send the reply
 130                 err = sendto(sockfd, buf, reply_size, 0, (struct sockaddr *)&from_addr, slen);
 131                 if(err < 0) {
 132                         printf("error replying to message\n");
 133                         return -1;
 134                 }
 135         }
 136
 137         return 0;
 138 }
 139
 140 static void usage()
 141 {
 142         printf("usage: netblock <blockdev file>\n");
 143 }
 144
 145 int main(int argc, char *argv[])
 146 {
 147         int err;
 148
 149         if(argc < 2) {
 150                 usage();
 151                 return -1;
 152         }
 153
 154         dev = NULL;
 155         sockfd = -1;
 156
 157         dev = new blockdevice;
 158
 159         // open the block device and figure out how big it is
 160         dev->filefd = open(argv[1], O_RDWR|O_BINARY);
 161         if(dev->filefd < 0) {
 162                 printf("error opening file '%s'\n", argv[1]);
 163                 return -1;
 164         }
 165
 166         struct stat stat;
 167         err = fstat(dev->filefd, &stat);
 168         if(err < 0) {
 169                 printf("error statting file\n");
 170                 return -1;
 171         }
 172
 173         if(stat.st_size < 512) {
 174                 printf("file is too small to use as a block device\n");
 175                 return -1;
 176         }
 177
 178         dev->size = stat.st_size;
 179
 180         printf("opened file '%s', size %Ld\n", argv[1], dev->size);
 181
 182         dev->id = 0;
 183
 184         // open the server socket
 185         struct sockaddr_in addr;
 186         addr.sin_family = AF_INET;
 187         addr.sin_port = htons(9999);
 188         memset(&addr.sin_addr, 0, sizeof(addr.sin_addr));
 189
 190         sockfd = socket(PF_INET, SOCK_DGRAM, 0);
 191         if(sockfd < 0) {
 192                 printf("error creating socket\n");
 193                 return -1;
 194         }
 195
 196         err = bind(sockfd, (struct sockaddr *)&addr, sizeof(struct sockaddr));
 197         if(err < 0) {
 198                 printf("error binding socket\n");
 199                 return -1;
 200         }
 201
 202         net_loop();
 203
 204         return 0;
 205 }