vfs: add vfs_shell_snap module

The shell_snap VFS module plumbs into the snapshot (aka shadow-copy)
management paths used by Samba's File Server Remote VSS Protocol (FSRVP)
server.
The following shell callouts may be configured in smb.conf:

shell_snap: check path command
	- Called when an FSRVP client wishes to check whether a given
	  share supports snapshot create/delete requests.
	- The command is called with a single <share path> argument.
	- The command must return 0 if <share path> is capable of being
	  snapshotted.

shell_snap: create command
	- Called when an FSRVP client wishes to create a snapshot.
	- The command is called with a single <share path> argument.
	- The command must return 0 status if the snapshot was
	  successfully taken.
	- The command must output the path of the newly created snapshot
	  to stdout.

shell_snap: delete command
	- Called when an FSRVP client wishes to delete a snapshot.
	- The command is called with <base share path> and
	  <snapshot share path> arguments.
	- The command must return 0 status if the snapshot was
	  successfully removed.

Signed-off-by: David Disseldorp <ddiss@samba.org>
Reviewed-by: Jeremy Allison <jra@samba.org>

source3/modules/vfs_shell_snap.c

@@ -0,0 +1,201 @@
+/*
+ * Module for snapshot management using shell callouts
+ *
+ * Copyright (C) David Disseldorp 2013-2015
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "includes.h"
+#include "include/ntioctl.h"
+#include "system/filesys.h"
+#include "smbd/smbd.h"
+
+/*
+ * Check whether a path can be shadow copied. Return the base volume, allowing
+ * the caller to determine if multiple paths lie on the same base volume.
+ */
+static NTSTATUS shell_snap_check_path(struct vfs_handle_struct *handle,
+				      TALLOC_CTX *mem_ctx,
+				      const char *service_path,
+				      char **base_volume)
+{
+	NTSTATUS status;
+	const char *cmd;
+	char *cmd_run;
+	int ret;
+	TALLOC_CTX *tmp_ctx;
+
+	cmd = lp_parm_const_string(handle->conn->params->service,
+				   "shell_snap", "check path command", "");
+	if ((cmd == NULL) || (strlen(cmd) == 0)) {
+		DEBUG(0,
+		      ("\"shell_snap:check path command\" not configured\n"));
+		status = NT_STATUS_NOT_SUPPORTED;
+		goto err_out;
+	}
+
+	tmp_ctx = talloc_new(mem_ctx);
+	if (tmp_ctx == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto err_out;
+	}
+
+	/* add service path argument */
+	cmd_run = talloc_asprintf(tmp_ctx, "%s %s", cmd, service_path);
+	if (cmd_run == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto err_tmp_free;
+	}
+
+	ret = smbrun(cmd_run, NULL);
+	if (ret != 0) {
+		DEBUG(0, ("%s failed with %d\n", cmd_run, ret));
+		status = NT_STATUS_NOT_SUPPORTED;
+		goto err_tmp_free;
+	}
+
+	/* assume the service path is the base volume */
+	*base_volume = talloc_strdup(mem_ctx, service_path);
+	if (*base_volume == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto err_tmp_free;
+	}
+	status = NT_STATUS_OK;
+err_tmp_free:
+	talloc_free(tmp_ctx);
+err_out:
+	return status;
+}
+
+static NTSTATUS shell_snap_create(struct vfs_handle_struct *handle,
+				  TALLOC_CTX *mem_ctx,
+				  const char *base_volume,
+				  time_t *tstamp,
+				  bool rw,
+				  char **base_path,
+				  char **snap_path)
+{
+	const char *cmd;
+	char *cmd_run;
+	char **qlines;
+	int numlines, ret;
+	int fd = -1;
+	TALLOC_CTX *tmp_ctx;
+	NTSTATUS status;
+
+	cmd = lp_parm_const_string(handle->conn->params->service,
+				   "shell_snap", "create command", "");
+	if ((cmd == NULL) || (strlen(cmd) == 0)) {
+		DEBUG(1, ("\"shell_snap:create command\" not configured\n"));
+		status = NT_STATUS_NOT_SUPPORTED;
+		goto err_out;
+	}
+
+	tmp_ctx = talloc_new(mem_ctx);
+	if (tmp_ctx == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto err_out;
+	}
+
+	/* add base vol argument */
+	cmd_run = talloc_asprintf(tmp_ctx, "%s %s", cmd, base_volume);
+	if (cmd_run == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto err_tmp_free;
+	}
+
+	ret = smbrun(cmd_run, &fd);
+	talloc_free(cmd_run);
+	if (ret != 0) {
+		if (fd != -1) {
+			close(fd);
+		}
+		status = NT_STATUS_UNSUCCESSFUL;
+		goto err_tmp_free;
+	}
+
+	numlines = 0;
+	qlines = fd_lines_load(fd, &numlines, PATH_MAX + 1, tmp_ctx);
+	close(fd);
+
+	/* script must return the snapshot path as a single line */
+	if ((numlines == 0) || (qlines == NULL) || (qlines[0] == NULL)) {
+		status = NT_STATUS_UNSUCCESSFUL;
+		goto err_tmp_free;
+	}
+
+	*base_path = talloc_strdup(mem_ctx, base_volume);
+	if (*base_path == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		goto err_tmp_free;
+	}
+	*snap_path = talloc_strdup(mem_ctx, qlines[0]);
+	if (*snap_path == NULL) {
+		status = NT_STATUS_NO_MEMORY;
+		talloc_free(*base_path);
+		goto err_tmp_free;
+	}
+
+	status = NT_STATUS_OK;
+err_tmp_free:
+	talloc_free(tmp_ctx);
+err_out:
+	return status;
+}
+
+static NTSTATUS shell_snap_delete(struct vfs_handle_struct *handle,
+				  TALLOC_CTX *mem_ctx,
+				  char *base_path,
+				  char *snap_path)
+{
+	const char *cmd;
+	char *cmd_run;
+	int ret;
+
+	cmd = lp_parm_const_string(handle->conn->params->service,
+				   "shell_snap", "delete command", "");
+	if ((cmd == NULL) || (strlen(cmd) == 0)) {
+		DEBUG(1, ("\"shell_snap:delete command\" not configured\n"));
+		return NT_STATUS_NOT_SUPPORTED;
+	}
+
+	/* add base path and snap path arguments */
+	cmd_run = talloc_asprintf(mem_ctx, "%s %s %s",
+				  cmd, base_path, snap_path);
+	if (cmd_run == NULL) {
+		return NT_STATUS_NO_MEMORY;
+	}
+
+	ret = smbrun(cmd_run, NULL);
+	talloc_free(cmd_run);
+	if (ret != 0) {
+		return NT_STATUS_UNSUCCESSFUL;
+	}
+
+	return NT_STATUS_OK;
+}
+
+static struct vfs_fn_pointers shell_snap_fns = {
+	.snap_check_path_fn = shell_snap_check_path,
+	.snap_create_fn = shell_snap_create,
+	.snap_delete_fn = shell_snap_delete,
+};
+
+NTSTATUS vfs_shell_snap_init(void);
+NTSTATUS vfs_shell_snap_init(void)
+{
+	return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
+				"shell_snap", &shell_snap_fns);
+}

source3/modules/wscript_build

@@ -469,6 +469,14 @@ bld.SAMBA3_MODULE('vfs_btrfs',
                  internal_module=bld.SAMBA3_IS_STATIC_MODULE('vfs_btrfs'),
                  enabled=bld.SAMBA3_IS_ENABLED_MODULE('vfs_btrfs'))
 
+bld.SAMBA3_MODULE('vfs_shell_snap',
+                 subsystem='vfs',
+                 source='vfs_shell_snap.c',
+                 deps='samba-util',
+                 init_function='',
+                 internal_module=bld.SAMBA3_IS_STATIC_MODULE('vfs_shell_snap'),
+                 enabled=bld.SAMBA3_IS_ENABLED_MODULE('vfs_shell_snap'))
+
 bld.SAMBA3_SUBSYSTEM('perfcount',
                     source='',
                      deps='smbd_base')

source3/wscript

@@ -1582,7 +1582,7 @@ main() {
                                       auth_script vfs_readahead vfs_xattr_tdb vfs_posix_eadb
                                       vfs_streams_xattr vfs_streams_depot vfs_acl_xattr vfs_acl_tdb
                                       vfs_smb_traffic_analyzer vfs_preopen vfs_catia vfs_scannedonly
-				      vfs_media_harmony vfs_unityed_media vfs_fruit
+				      vfs_media_harmony vfs_unityed_media vfs_fruit vfs_shell_snap
 				      vfs_commit
 				      vfs_worm
                                       vfs_crossrename vfs_linux_xfs_sgid