--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toys/other/nbd_client.c	Sun Jul 06 19:58:49 2014 -0500
@@ -0,0 +1,128 @@
+/* nbd-client.c - network block device client
+ *
+ * Copyright 2010 Rob Landley <rob@landley.net>
+ *
+ * Not in SUSv4.
+
+// This little dance is because a NEWTOY with - in the name tries to do
+// things like prototype "nbd-client_main" which isn't a valid symbol. So
+// we hide the underscore name and OLDTOY the name we want.
+USE_NBD_CLIENT(NEWTOY(nbd_client, "<3>3ns", 0))
+USE_NBD_CLIENT(OLDTOY(nbd-client, nbd_client, OPTSTR_nbd_client, TOYFLAG_USR|TOYFLAG_BIN))
+
+config NBD_CLIENT
+  bool "nbd-client"
+  default y
+  help
+    usage: nbd-client [-ns] HOST PORT DEVICE
+
+    -n	Do not fork into background
+    -s	nbd swap support (lock server into memory)
+*/
+
+/*  TODO:
+    usage: nbd-client [-sSpn] [-b BLKSZ] [-t SECS] [-N name] HOST PORT DEVICE
+
+    -b	block size
+    -t	timeout in seconds
+    -S	sdp
+    -p	persist
+    -n	nofork
+    -d	DEVICE
+    -c	DEVICE
+*/
+
+#define FOR_nbd_client
+#include "toys.h"
+#include <linux/nbd.h>
+
+void nbd_client_main(void)
+{
+  int sock = -1, nbd, flags;
+  unsigned long timeout = 0;
+  struct addrinfo *addr, *p;
+  char *host=toys.optargs[0], *port=toys.optargs[1], *device=toys.optargs[2];
+  uint64_t devsize;
+
+  // Repeat until spanked
+
+  nbd = xopen(device, O_RDWR);
+  for (;;) {
+    int temp;
+    struct addrinfo hints;
+
+    // Find and connect to server
+
+    memset(&hints, 0, sizeof(hints));
+    hints.ai_family = PF_UNSPEC;
+    hints.ai_socktype = SOCK_STREAM;
+    if (getaddrinfo(host, port, &hints, &addr)) addr = 0;
+    for (p = addr; p; p = p->ai_next) {
+      sock = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
+      if (-1 != connect(sock, p->ai_addr, p->ai_addrlen)) break;
+      close(sock);
+    }
+    freeaddrinfo(addr);
+
+    if (!p) perror_exit("%s:%s", host, port);
+
+    temp = 1;
+    setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, &temp, sizeof(int));
+
+    // Read login data
+
+    xreadall(sock, toybuf, 152);
+    if (memcmp(toybuf, "NBDMAGIC\x00\x00\x42\x02\x81\x86\x12\x53", 16))
+      error_exit("bad login %s:%s", host, port);
+    devsize = SWAP_BE64(*(uint64_t *)(toybuf+16));
+    flags = SWAP_BE32(*(int *)(toybuf+24));
+
+    // Set 4k block size.  Everything uses that these days.
+    ioctl(nbd, NBD_SET_BLKSIZE, 4096);
+    ioctl(nbd, NBD_SET_SIZE_BLOCKS, devsize/4096);
+    ioctl(nbd, NBD_CLEAR_SOCK);
+
+    // If the sucker was exported read only, respect that locally.
+    temp = (flags & 2) ? 1 : 0;
+    xioctl(nbd, BLKROSET, &temp);
+
+    if (timeout && ioctl(nbd, NBD_SET_TIMEOUT, timeout)<0) break;
+    if (ioctl(nbd, NBD_SET_SOCK, sock) < 0) break;
+
+    if (toys.optflags & FLAG_s) mlockall(MCL_CURRENT|MCL_FUTURE);
+
+    // Open the device to force reread of the partition table.
+    if ((toys.optflags & FLAG_n) || !xfork()) {
+      char *s = strrchr(device, '/');
+      int i;
+
+      sprintf(toybuf, "/sys/block/%.32s/pid", s ? s+1 : device);
+      // Is it up yet? (Give it 10 seconds.)
+      for (i=0; i<100; i++) {
+        temp = open(toybuf, O_RDONLY);
+        if (temp == -1) msleep(100);
+        else {
+          close(temp);
+          break;
+        }
+      }
+      close(open(device, O_RDONLY));
+      if (!(toys.optflags & FLAG_n)) exit(0);
+    }
+
+    // Daemonize here.
+
+    daemon(0,0);
+
+    // Process NBD requests until further notice.
+
+    if (ioctl(nbd, NBD_DO_IT)>=0 || errno==EBADR) break;
+    close(sock);
+  }
+  close(nbd);
+
+  // Flush queue and exit.
+
+  ioctl(nbd, NBD_CLEAR_QUE);
+  ioctl(nbd, NBD_CLEAR_SOCK);
+}