FITS: generating send-streams in portable format
This commit adds the command 'zfs fits-send', analogous to zfs send. The
generated send stream is compatible with the stream generated with that
from 'btrfs send' and can in principle easily be received to any filesystem.

*** 3195,3199 ****
--- 3195,3298 ----
          if (top_zfs)
                  free(top_zfs);
  
          return (err);
  }
+ 
+ /*
+  * Generate a fits stream for the dataset identified by the argument zhp.
+  *
+  * The content of the send stream is the snapshot identified by
+  * 'tosnap'.  Incremental streams are requested from the snapshot identified
+  * by "fromsnap" (if non-null)
+  * Currently no recursive send is implemented
+  */
+ int
+ zfs_fits_send(zfs_handle_t *zhp, const char *fromsnap, const char *tosnap,
+     sendflags_t *flags, int outfd, snapfilter_cb_t filter_func,
+     void *cb_arg)
+ {
+         char errbuf[1024];
+         char name[MAXPATHLEN];
+         zfs_cmd_t zc = { 0 };
+         libzfs_handle_t *hdl = zhp->zfs_hdl;
+         zfs_handle_t *thdl;
+ 
+         (void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
+             "cannot send '%s'"), zhp->zfs_name);
+ 
+         if (fromsnap && fromsnap[0] == '\0') {
+                 zfs_error_aux(zhp->zfs_hdl, dgettext(TEXT_DOMAIN,
+                     "zero-length incremental source"));
+                 return (zfs_error(zhp->zfs_hdl, EZFS_NOENT, errbuf));
+         }
+ 
+         (void) snprintf(name, sizeof (name), "%s@%s", zhp->zfs_name, tosnap);
+         if ((thdl = zfs_open(hdl, name, ZFS_TYPE_SNAPSHOT)) == NULL) {
+                 (void) fprintf(stderr, dgettext(TEXT_DOMAIN,
+                     "WARNING: could not send %s@%s: does not exist\n"),
+                     zhp->zfs_name, tosnap);
+                 return (B_TRUE);
+         }
+         zc.zc_sendobj = zfs_prop_get_int(thdl, ZFS_PROP_OBJSETID);
+         zfs_close(thdl);
+ 
+         if (fromsnap) {
+                 (void) snprintf(name, sizeof (name), "%s@%s",
+                     zhp->zfs_name, fromsnap);
+                 if ((thdl = zfs_open(hdl, name, ZFS_TYPE_SNAPSHOT)) == NULL) {
+                         (void) fprintf(stderr, dgettext(TEXT_DOMAIN,
+                             "WARNING: could not send %s@%s:\n"
+                             "incremental source (%s@%s) does not exist\n"),
+                             zhp->zfs_name, tosnap,
+                             zhp->zfs_name, fromsnap);
+                         return (B_TRUE);
+                 }
+                 zc.zc_fromobj = zfs_prop_get_int(thdl, ZFS_PROP_OBJSETID);
+                 zfs_close(thdl);
+         }
+ 
+         assert(zhp->zfs_type == ZFS_TYPE_FILESYSTEM);
+ 
+         (void) snprintf(zc.zc_name, sizeof (zc.zc_name), "%s@%s",
+             zhp->zfs_name, tosnap);
+         zc.zc_cookie = outfd;
+         zc.zc_obj = 0;
+ 
+         if (zfs_ioctl(zhp->zfs_hdl, ZFS_IOC_FITS_SEND, &zc) != 0) {
+                 char errbuf[1024];
+                 (void) snprintf(errbuf, sizeof (errbuf), dgettext(TEXT_DOMAIN,
+                     "warning: cannot send '%s'"), zhp->zfs_name);
+ 
+                 switch (errno) {
+                 case EXDEV:
+                         zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+                             "not an earlier snapshot from the same fs"));
+                         return (zfs_error(hdl, EZFS_CROSSTARGET, errbuf));
+                 case ENOENT:
+                         if (zfs_dataset_exists(hdl, zc.zc_name,
+                             ZFS_TYPE_SNAPSHOT)) {
+                                 zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+                                     "incremental source (@%s) does not exist"),
+                                     zc.zc_value);
+                         }
+                         return (zfs_error(hdl, EZFS_NOENT, errbuf));
+                 case EDQUOT:
+                 case EFBIG:
+                 case EIO:
+                 case ENOLINK:
+                 case ENOSPC:
+                 case ENOSTR:
+                 case ENXIO:
+                 case EPIPE:
+                 case ERANGE:
+                 case EFAULT:
+                 case EROFS:
+                         zfs_error_aux(hdl, strerror(errno));
+                         return (zfs_error(hdl, EZFS_BADBACKUP, errbuf));
+                 default:
+                         return (zfs_standard_error(hdl, errno, errbuf));
+                 }
+         }
+ 
+         return (0);
+ }