release/src/router/busybox/networking/nbd-client.c

   1 /*
   2  * Copyright 2010 Rob Landley <rob@landley.net>
   3  *
   4  * Licensed under GPLv2, see file LICENSE in this source tree.
   5  */
   6 #include "libbb.h"
   7 #include <netinet/tcp.h>
   8 #include <linux/fs.h>
   9
  10 //applet:IF_NBDCLIENT(APPLET_ODDNAME(nbd-client, nbdclient, BB_DIR_USR_SBIN, BB_SUID_DROP, nbdclient))
  11
  12 //kbuild:lib-$(CONFIG_NBDCLIENT) += nbd-client.o
  13
  14 //config:config NBDCLIENT
  15 //config:       bool "nbd-client"
  16 //config:       default y
  17 //config:       help
  18 //config:         Network block device client
  19
  20 #define NBD_SET_SOCK          _IO(0xab, 0)
  21 #define NBD_SET_BLKSIZE       _IO(0xab, 1)
  22 #define NBD_SET_SIZE          _IO(0xab, 2)
  23 #define NBD_DO_IT             _IO(0xab, 3)
  24 #define NBD_CLEAR_SOCK        _IO(0xab, 4)
  25 #define NBD_CLEAR_QUEUE       _IO(0xab, 5)
  26 #define NBD_PRINT_DEBUG       _IO(0xab, 6)
  27 #define NBD_SET_SIZE_BLOCKS   _IO(0xab, 7)
  28 #define NBD_DISCONNECT        _IO(0xab, 8)
  29 #define NBD_SET_TIMEOUT       _IO(0xab, 9)
  30
  31 //usage:#define nbdclient_trivial_usage
  32 //usage:       "HOST PORT BLOCKDEV"
  33 //usage:#define nbdclient_full_usage "\n\n"
  34 //usage:       "Connect to HOST and provide a network block device on BLOCKDEV"
  35
  36 //TODO: more compat with nbd-client version 2.9.13 -
  37 //Usage: nbd-client [bs=blocksize] [timeout=sec] host port nbd_device [-swap] [-persist] [-nofork]
  38 //Or   : nbd-client -d nbd_device
  39 //Or   : nbd-client -c nbd_device
  40 //Default value for blocksize is 1024 (recommended for ethernet)
  41 //Allowed values for blocksize are 512,1024,2048,4096
  42 //Note, that kernel 2.4.2 and older ones do not work correctly with
  43 //blocksizes other than 1024 without patches
  44
  45 int nbdclient_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
  46 int nbdclient_main(int argc, char **argv)
  47 {
  48         unsigned long timeout = 0;
  49 #if BB_MMU
  50         int nofork = 0;
  51 #endif
  52         char *host, *port, *device;
  53         struct nbd_header_t {
  54                 uint64_t magic1; // "NBDMAGIC"
  55                 uint64_t magic2; // 0x420281861253 big endian
  56                 uint64_t devsize;
  57                 uint32_t flags;
  58                 char data[124];
  59         } nbd_header;
  60         struct bug_check {
  61                 char c[offsetof(struct nbd_header_t, data) == 8+8+8+4 ? 1 : -1];
  62         };
  63
  64         // Parse command line stuff (just a stub now)
  65         if (argc != 4)
  66                 bb_show_usage();
  67
  68 #if !BB_MMU
  69         bb_daemonize_or_rexec(DAEMON_CLOSE_EXTRA_FDS, argv);
  70 #endif
  71
  72         host = argv[1];
  73         port = argv[2];
  74         device = argv[3];
  75
  76         // Repeat until spanked (-persist behavior)
  77         for (;;) {
  78                 int sock, nbd;
  79                 int ro;
  80
  81                 // Make sure the /dev/nbd exists
  82                 nbd = xopen(device, O_RDWR);
  83
  84                 // Find and connect to server
  85                 sock = create_and_connect_stream_or_die(host, xatou16(port));
  86                 setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &const_int_1, sizeof(const_int_1));
  87
  88                 // Log on to the server
  89                 xread(sock, &nbd_header, 8+8+8+4 + 124);
  90                 if (memcmp(&nbd_header.magic1, "NBDMAGIC""\x00\x00\x42\x02\x81\x86\x12\x53", 16) != 0)
  91                         bb_error_msg_and_die("login failed");
  92
  93                 // Set 4k block size.  Everything uses that these days
  94                 ioctl(nbd, NBD_SET_BLKSIZE, 4096);
  95                 ioctl(nbd, NBD_SET_SIZE_BLOCKS, SWAP_BE64(nbd_header.devsize) / 4096);
  96                 ioctl(nbd, NBD_CLEAR_SOCK);
  97
  98                 // If the sucker was exported read only, respect that locally
  99                 ro = (nbd_header.flags & SWAP_BE32(2)) / SWAP_BE32(2);
 100                 if (ioctl(nbd, BLKROSET, &ro) < 0)
 101                         bb_perror_msg_and_die("BLKROSET");
 102
 103                 if (timeout)
 104                         if (ioctl(nbd, NBD_SET_TIMEOUT, timeout))
 105                                 bb_perror_msg_and_die("NBD_SET_TIMEOUT");
 106                 if (ioctl(nbd, NBD_SET_SOCK, sock))
 107                         bb_perror_msg_and_die("NBD_SET_SOCK");
 108
 109                 // if (swap) mlockall(MCL_CURRENT|MCL_FUTURE);
 110
 111 #if BB_MMU
 112                 // Open the device to force reread of the partition table.
 113                 // Need to do it in a separate process, since open(device)
 114                 // needs some other process to sit in ioctl(nbd, NBD_DO_IT).
 115                 if (fork() == 0) {
 116                         char *s = strrchr(device, '/');
 117                         sprintf(nbd_header.data, "/sys/block/%.32s/pid", s ? s + 1 : device);
 118                         // Is it up yet?
 119                         for (;;) {
 120                                 int fd = open(nbd_header.data, O_RDONLY);
 121                                 if (fd >= 0) {
 122                                         //close(fd);
 123                                         break;
 124                                 }
 125                                 sleep(1);
 126                         }
 127                         open(device, O_RDONLY);
 128                         return 0;
 129                 }
 130
 131                 // Daemonize here
 132                 if (!nofork) {
 133                         daemon(0, 0);
 134                         nofork = 1;
 135                 }
 136 #endif
 137
 138                 // This turns us (the process that calls this ioctl)
 139                 // into a dedicated NBD request handler.
 140                 // We block here for a long time.
 141                 // When exactly ioctl returns? On a signal,
 142                 // or if someone does ioctl(NBD_DISCONNECT) [nbd-client -d].
 143                 if (ioctl(nbd, NBD_DO_IT) >= 0 || errno == EBADR) {
 144                         // Flush queue and exit
 145                         ioctl(nbd, NBD_CLEAR_QUEUE);
 146                         ioctl(nbd, NBD_CLEAR_SOCK);
 147                         break;
 148                 }
 149
 150                 close(sock);
 151                 close(nbd);
 152         }
 153
 154         return 0;
 155 }