example: Copying a directory between two guests using threads.

1 files changed, 292 insertions, 0 deletions

diff --git a/examples/copy_over.c b/examples/copy_over.c
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--- /dev/null
+++ b/examples/copy_over.c
@@ -0,0 +1,292 @@
+/* Copy a directory from one libvirt guest to another.
+ *
+ * This is a more substantial example of using the libguestfs API,
+ * demonstrating amongst other things:
+ *
+ * - using multiple handles with threads
+ * - upload and downloading (using a pipe between handles)
+ * - inspection
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/time.h>
+
+#include <pthread.h>
+
+#include <guestfs.h>
+#include <libvirt/libvirt.h>
+
+struct threaddata {
+  const char *src;
+  const char *srcdir;
+  int fd;
+  pthread_t mainthread;
+};
+
+static void *start_srcthread (void *);
+static int open_guest (guestfs_h *g, const char *dom, int readonly);
+static int64_t timeval_diff (const struct timeval *x, const struct timeval *y);
+static int compare_keys_len (const void *p1, const void *p2);
+static size_t count_strings (char *const *argv);
+
+static void
+usage (void)
+{
+  fprintf (stderr,
+    "Usage: copy_over source srcdir dest destdir\n"
+    "\n"
+    "  source  : the source domain (a libvirt guest name)\n"
+    "  srcdir  : the directory to copy from the source guest\n"
+    "  dest    : the destination domain (a libvirt guest name)\n"
+    "  destdir : the destination directory (must exist at destination)\n"
+    "\n"
+    "eg: copy_over Src /home/rjones Dest /tmp/dir\n"
+    "would copy /home/rjones from Src to /tmp/dir on Dest\n"
+    "\n"
+    "The destination guest cannot be running.\n");
+}
+
+int
+main (int argc, char *argv[])
+{
+  const char *src, *srcdir, *dest, *destdir;
+  guestfs_h *destg;
+  int fd[2];
+  pthread_t srcthread;
+  struct threaddata threaddata;
+  int err;
+  char fdname[128];
+  struct timeval start_t, end_t;
+  int64_t ms;
+
+  /* This is required when using libvirt from multiple threads. */
+  virInitialize ();
+
+  if (argc != 5) {
+    usage ();
+    exit (EXIT_FAILURE);
+  }
+
+  src = argv[1];
+  srcdir = argv[2];
+  dest = argv[3];
+  destdir = argv[4];
+
+  /* Instead of downloading to local disk and uploading, we are going
+   * to connect the source download and destination upload using a
+   * pipe.  Create that pipe.
+   */
+  if (pipe (fd) == -1) {
+    perror ("pipe");
+    exit (EXIT_FAILURE);
+  }
+
+  /* We don't want the pipe to be passed to subprocesses. */
+  if (fcntl (fd[0], F_SETFD, FD_CLOEXEC) == -1 ||
+      fcntl (fd[1], F_SETFD, FD_CLOEXEC) == -1) {
+    perror ("fcntl");
+    exit (EXIT_FAILURE);
+  }
+
+  /* The libguestfs API is synchronous, so if we want to use two
+   * handles concurrently, then we have to have two threads.  In this
+   * case the main thread (this one) is handling the destination
+   * domain (uploading), and we create one more thread to handle the
+   * source domain (downloading).
+   */
+  threaddata.src = src;
+  threaddata.srcdir = srcdir;
+  threaddata.fd = fd[1];
+  threaddata.mainthread = pthread_self ();
+  err = pthread_create (&srcthread, NULL, start_srcthread, &threaddata);
+  if (err != 0) {
+    fprintf (stderr, "pthread_create: %s\n", strerror (err));
+    exit (EXIT_FAILURE);
+  }
+
+  /* Open the destination domain. */
+  destg = guestfs_create ();
+  if (!destg) {
+    perror ("failed to create libguestfs handle");
+    pthread_cancel (srcthread);
+    exit (EXIT_FAILURE);
+  }
+  if (open_guest (destg, dest, 0) == -1) {
+    pthread_cancel (srcthread);
+    exit (EXIT_FAILURE);
+  }
+
+  gettimeofday (&start_t, NULL);
+
+  /* Begin the upload. */
+  snprintf (fdname, sizeof fdname, "/dev/fd/%d", fd[0]);
+  if (guestfs_tar_in (destg, fdname, destdir) == -1) {
+    pthread_cancel (srcthread);
+    exit (EXIT_FAILURE);
+  }
+
+  /* Close our end of the pipe.  The other thread will close the
+   * other side of the pipe.
+   */
+  close (fd[0]);
+
+  /* Wait for the other thread to finish. */
+  err = pthread_join (srcthread, NULL);
+  if (err != 0) {
+    fprintf (stderr, "pthread_join: %s\n", strerror (err));
+    exit (EXIT_FAILURE);
+  }
+
+  /* Clean up. */
+  if (guestfs_umount_all (destg) == -1)
+    exit (EXIT_FAILURE);
+  guestfs_close (destg);
+
+  gettimeofday (&end_t, NULL);
+
+  /* Print the elapsed time. */
+  ms = timeval_diff (&start_t, &end_t);
+  printf ("copy finished, elapsed time (excluding launch) was "
+          "%" PRIi64 ".%03" PRIi64 " s\n",
+          ms / 1000, ms % 1000);
+
+  exit (EXIT_SUCCESS);
+}
+
+static void *
+start_srcthread (void *arg)
+{
+  struct threaddata *threaddata = arg;
+  guestfs_h *srcg;
+  char fdname[128];
+
+  /* Open the source domain. */
+  srcg = guestfs_create ();
+  if (!srcg) {
+    perror ("failed to create libguestfs handle");
+    pthread_cancel (threaddata->mainthread);
+    exit (EXIT_FAILURE);
+  }
+  if (open_guest (srcg, threaddata->src, 1) == -1) {
+    pthread_cancel (threaddata->mainthread);
+    exit (EXIT_FAILURE);
+  }
+
+  /* Begin the download. */
+  snprintf (fdname, sizeof fdname, "/dev/fd/%d", threaddata->fd);
+  if (guestfs_tar_out (srcg, threaddata->srcdir, fdname) == -1) {
+    pthread_cancel (threaddata->mainthread);
+    exit (EXIT_FAILURE);
+  }
+
+  /* Close the pipe; this will cause the receiver to finish the upload. */
+  if (close (threaddata->fd) == -1) {
+    pthread_cancel (threaddata->mainthread);
+    exit (EXIT_FAILURE);
+  }
+
+  /* Clean up. */
+  if (guestfs_umount_all (srcg) == -1) {
+    pthread_cancel (threaddata->mainthread);
+    exit (EXIT_FAILURE);
+  }
+  guestfs_close (srcg);
+
+  return NULL;
+}
+
+/* This function deals with the complexity of adding the domain,
+ * launching the handle, and mounting up filesystems.  See
+ * 'examples/inspect_vm.c' to understand how this works.
+ */
+static int
+open_guest (guestfs_h *g, const char *dom, int readonly)
+{
+  char **roots, *root, **mountpoints;
+  size_t i;
+
+  /* Use libvirt to find the guest disks and add them to the handle. */
+  if (guestfs_add_domain (g, dom,
+                          GUESTFS_ADD_DOMAIN_READONLY, readonly,
+                          -1) == -1)
+    return -1;
+
+  if (guestfs_launch (g) == -1)
+    return -1;
+
+  /* Inspect the guest, looking for operating systems. */
+  roots = guestfs_inspect_os (g);
+  if (roots == NULL)
+    return -1;
+
+  if (roots[0] == NULL || roots[1] != NULL) {
+    fprintf (stderr, "copy_over: %s: no operating systems or multiple operating systems found\n", dom);
+    return -1;
+  }
+
+  root = roots[0];
+
+  /* Mount up the filesystems (like 'guestfish -i'). */
+  mountpoints = guestfs_inspect_get_mountpoints (g, root);
+  if (mountpoints == NULL)
+    return -1;
+
+  qsort (mountpoints, count_strings (mountpoints) / 2, 2 * sizeof (char *),
+         compare_keys_len);
+  for (i = 0; mountpoints[i] != NULL; i += 2) {
+    /* Ignore failures from this call, since bogus entries can
+     * appear in the guest's /etc/fstab.
+     */
+    (readonly ? guestfs_mount_ro : guestfs_mount)
+      (g, mountpoints[i+1], mountpoints[i]);
+    free (mountpoints[i]);
+    free (mountpoints[i+1]);
+  }
+
+  free (mountpoints);
+
+  free (root);
+  free (roots);
+
+  /* Everything ready, no error. */
+  return 0;
+}
+
+/* Compute Y - X and return the result in milliseconds.
+ * Approximately the same as this code:
+ * http://www.mpp.mpg.de/~huber/util/timevaldiff.c
+ */
+static int64_t
+timeval_diff (const struct timeval *x, const struct timeval *y)
+{
+  int64_t msec;
+
+  msec = (y->tv_sec - x->tv_sec) * 1000;
+  msec += (y->tv_usec - x->tv_usec) / 1000;
+  return msec;
+}
+
+static int
+compare_keys_len (const void *p1, const void *p2)
+{
+  const char *key1 = * (char * const *) p1;
+  const char *key2 = * (char * const *) p2;
+  return strlen (key1) - strlen (key2);
+}
+
+static size_t
+count_strings (char *const *argv)
+{
+  size_t c;
+
+  for (c = 0; argv[c]; ++c)
+    ;
+  return c;
+}