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+<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>Chapter 10. VFS Modules</title><link rel="stylesheet" href="samba.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.68.1"><link rel="start" href="index.html" title="SAMBA Developers Guide"><link rel="up" href="pt03.html" title="Part III. Samba Subsystems"><link rel="prev" href="rpc-plugin.html" title="Chapter 9. RPC Pluggable Modules"><link rel="next" href="parsing.html" title="Chapter 11. The smb.conf file"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 10. VFS Modules</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="rpc-plugin.html">Prev</a> </td><th width="60%" align="center">Part III. Samba Subsystems</th><td width="20%" align="right"> <a accesskey="n" href="parsing.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en"><div class="titlepage"><div><div><h2 class="title"><a name="vfs"></a>Chapter 10. VFS Modules</h2></div><div><div class="author"><h3 class="author"><span class="firstname">Alexander</span> <span class="surname">Bokovoy</span></h3><div class="affiliation"><div class="address"><p><code class="email"><<a href="mailto:ab@samba.org">ab@samba.org</a>></code></p></div></div></div></div><div><div class="author"><h3 class="author"><span class="firstname">Stefan</span> <span class="surname">Metzmacher</span></h3><div class="affiliation"><div class="address"><p><code class="email"><<a href="mailto:metze@samba.org">metze@samba.org</a>></code></p></div></div></div></div><div><p class="pubdate"> 27 May 2003 </p></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="sect1"><a href="vfs.html#id2525317">The Samba (Posix) VFS layer</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2525323">The general interface</a></span></dt><dt><span class="sect2"><a href="vfs.html#id2525419">Possible VFS operation layers</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id2525480">The Interaction between the Samba VFS subsystem and the modules</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2525487">Initialization and registration</a></span></dt><dt><span class="sect2"><a href="vfs.html#id2525637">How the Modules handle per connection data</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id2525842">Upgrading to the New VFS Interface</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2525848">Upgrading from 2.2.* and 3.0aplha modules</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id2526400">Some Notes</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2526406">Implement TRANSPARENT functions</a></span></dt><dt><span class="sect2"><a href="vfs.html#id2526426">Implement OPAQUE functions</a></span></dt></dl></dd></dl></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2525317"></a>The Samba (Posix) VFS layer</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2525323"></a>The general interface</h3></div></div></div><p>
+Each VFS operation has a vfs_op_type, a function pointer and a handle pointer in the
+struct vfs_ops and tree macros to make it easier to call the operations.
+(Take a look at <code class="filename">include/vfs.h</code> and <code class="filename">include/vfs_macros.h</code>.)
+</p><pre class="programlisting">
+typedef enum _vfs_op_type {
+ SMB_VFS_OP_NOOP = -1,
+
+ ...
+
+ /* File operations */
+
+ SMB_VFS_OP_OPEN,
+ SMB_VFS_OP_CLOSE,
+ SMB_VFS_OP_READ,
+ SMB_VFS_OP_WRITE,
+ SMB_VFS_OP_LSEEK,
+ SMB_VFS_OP_SENDFILE,
+
+ ...
+
+ SMB_VFS_OP_LAST
+} vfs_op_type;
+</pre><p>This struct contains the function and handle pointers for all operations.</p><pre class="programlisting">
+struct vfs_ops {
+ struct vfs_fn_pointers {
+ ...
+
+ /* File operations */
+
+ int (*open)(struct vfs_handle_struct *handle,
+ struct connection_struct *conn,
+ const char *fname, int flags, mode_t mode);
+ int (*close)(struct vfs_handle_struct *handle,
+ struct files_struct *fsp, int fd);
+ ssize_t (*read)(struct vfs_handle_struct *handle,
+ struct files_struct *fsp, int fd, void *data, size_t n);
+ ssize_t (*write)(struct vfs_handle_struct *handle,
+ struct files_struct *fsp, int fd,
+ const void *data, size_t n);
+ SMB_OFF_T (*lseek)(struct vfs_handle_struct *handle,
+ struct files_struct *fsp, int fd,
+ SMB_OFF_T offset, int whence);
+ ssize_t (*sendfile)(struct vfs_handle_struct *handle,
+ int tofd, files_struct *fsp, int fromfd,
+ const DATA_BLOB *header, SMB_OFF_T offset, size_t count);
+
+ ...
+ } ops;
+
+ struct vfs_handles_pointers {
+ ...
+
+ /* File operations */
+
+ struct vfs_handle_struct *open;
+ struct vfs_handle_struct *close;
+ struct vfs_handle_struct *read;
+ struct vfs_handle_struct *write;
+ struct vfs_handle_struct *lseek;
+ struct vfs_handle_struct *sendfile;
+
+ ...
+ } handles;
+};
+</pre><p>
+This macros SHOULD be used to call any vfs operation.
+DO NOT ACCESS conn->vfs.ops.* directly !!!
+</p><pre class="programlisting">
+...
+
+/* File operations */
+#define SMB_VFS_OPEN(conn, fname, flags, mode) \
+ ((conn)->vfs.ops.open((conn)->vfs.handles.open,\
+ (conn), (fname), (flags), (mode)))
+#define SMB_VFS_CLOSE(fsp, fd) \
+ ((fsp)->conn->vfs.ops.close(\
+ (fsp)->conn->vfs.handles.close, (fsp), (fd)))
+#define SMB_VFS_READ(fsp, fd, data, n) \
+ ((fsp)->conn->vfs.ops.read(\
+ (fsp)->conn->vfs.handles.read,\
+ (fsp), (fd), (data), (n)))
+#define SMB_VFS_WRITE(fsp, fd, data, n) \
+ ((fsp)->conn->vfs.ops.write(\
+ (fsp)->conn->vfs.handles.write,\
+ (fsp), (fd), (data), (n)))
+#define SMB_VFS_LSEEK(fsp, fd, offset, whence) \
+ ((fsp)->conn->vfs.ops.lseek(\
+ (fsp)->conn->vfs.handles.lseek,\
+ (fsp), (fd), (offset), (whence)))
+#define SMB_VFS_SENDFILE(tofd, fsp, fromfd, header, offset, count) \
+ ((fsp)->conn->vfs.ops.sendfile(\
+ (fsp)->conn->vfs.handles.sendfile,\
+ (tofd), (fsp), (fromfd), (header), (offset), (count)))
+
+...
+</pre></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2525419"></a>Possible VFS operation layers</h3></div></div></div><p>
+These values are used by the VFS subsystem when building the conn->vfs
+and conn->vfs_opaque structs for a connection with multiple VFS modules.
+Internally, Samba differentiates only opaque and transparent layers at this process.
+Other types are used for providing better diagnosing facilities.
+</p><p>
+Most modules will provide transparent layers. Opaque layer is for modules
+which implement actual file system calls (like DB-based VFS). For example,
+default POSIX VFS which is built in into Samba is an opaque VFS module.
+</p><p>
+Other layer types (logger, splitter, scanner) were designed to provide different
+degree of transparency and for diagnosing VFS module behaviour.
+</p><p>
+Each module can implement several layers at the same time provided that only
+one layer is used per each operation.
+</p><pre class="programlisting">
+typedef enum _vfs_op_layer {
+ SMB_VFS_LAYER_NOOP = -1, /* - For using in VFS module to indicate end of array */
+ /* of operations description */
+ SMB_VFS_LAYER_OPAQUE = 0, /* - Final level, does not call anything beyond itself */
+ SMB_VFS_LAYER_TRANSPARENT, /* - Normal operation, calls underlying layer after */
+ /* possibly changing passed data */
+ SMB_VFS_LAYER_LOGGER, /* - Logs data, calls underlying layer, logging may not */
+ /* use Samba VFS */
+ SMB_VFS_LAYER_SPLITTER, /* - Splits operation, calls underlying layer _and_ own facility, */
+ /* then combines result */
+ SMB_VFS_LAYER_SCANNER /* - Checks data and possibly initiates additional */
+ /* file activity like logging to files _inside_ samba VFS */
+} vfs_op_layer;
+</pre></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2525480"></a>The Interaction between the Samba VFS subsystem and the modules</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2525487"></a>Initialization and registration</h3></div></div></div><p>
+As each Samba module a VFS module should have a
+</p><pre class="programlisting">NTSTATUS vfs_example_init(void);</pre><p> function if it's staticly linked to samba or
+</p><pre class="programlisting">NTSTATUS init_module(void);</pre><p> function if it's a shared module.
+</p><p>
+This should be the only non static function inside the module.
+Global variables should also be static!
+</p><p>
+The module should register its functions via the
+</p><pre class="programlisting">
+NTSTATUS smb_register_vfs(int version, const char *name, vfs_op_tuple *vfs_op_tuples);
+</pre><p> function.
+</p><div class="variablelist"><dl><dt><span class="term">version</span></dt><dd><p>should be filled with SMB_VFS_INTERFACE_VERSION</p></dd><dt><span class="term">name</span></dt><dd><p>this is the name witch can be listed in the
+<span><strong class="command">vfs objects</strong></span> parameter to use this module.</p></dd><dt><span class="term">vfs_op_tuples</span></dt><dd><p>
+this is an array of vfs_op_tuple's.
+(vfs_op_tuples is descripted in details below.)
+</p></dd></dl></div><p>
+For each operation the module wants to provide it has a entry in the
+vfs_op_tuple array.
+</p><pre class="programlisting">
+typedef struct _vfs_op_tuple {
+ void* op;
+ vfs_op_type type;
+ vfs_op_layer layer;
+} vfs_op_tuple;
+</pre><div class="variablelist"><dl><dt><span class="term">op</span></dt><dd><p>the function pointer to the specified function.</p></dd><dt><span class="term">type</span></dt><dd><p>the vfs_op_type of the function to specified witch operation the function provides.</p></dd><dt><span class="term">layer</span></dt><dd><p>the vfs_op_layer in whitch the function operates.</p></dd></dl></div><p>A simple example:</p><pre class="programlisting">
+static vfs_op_tuple example_op_tuples[] = {
+ {SMB_VFS_OP(example_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
+ {SMB_VFS_OP(example_disconnect), SMB_VFS_OP_DISCONNECT, SMB_VFS_LAYER_TRANSPARENT},
+
+ {SMB_VFS_OP(example_rename), SMB_VFS_OP_RENAME, SMB_VFS_LAYER_OPAQUE},
+
+ /* This indicates the end of the array */
+ {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
+};
+
+NTSTATUS init_module(void)
+{
+ return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, "example", example_op_tuples);
+}
+</pre></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2525637"></a>How the Modules handle per connection data</h3></div></div></div><p>Each VFS function has as first parameter a pointer to the modules vfs_handle_struct.
+</p><pre class="programlisting">
+typedef struct vfs_handle_struct {
+ struct vfs_handle_struct *next, *prev;
+ const char *param;
+ struct vfs_ops vfs_next;
+ struct connection_struct *conn;
+ void *data;
+ void (*free_data)(void **data);
+} vfs_handle_struct;
+</pre><div class="variablelist"><dl><dt><span class="term">param</span></dt><dd><p>this is the module parameter specified in the <span><strong class="command">vfs objects</strong></span> parameter.</p><p>e.g. for 'vfs objects = example:test' param would be "test".</p></dd><dt><span class="term">vfs_next</span></dt><dd><p>This vfs_ops struct contains the information for calling the next module operations.
+Use the SMB_VFS_NEXT_* macros to call a next module operations and
+don't access handle->vfs_next.ops.* directly!</p></dd><dt><span class="term">conn</span></dt><dd><p>This is a pointer back to the connection_struct to witch the handle belongs.</p></dd><dt><span class="term">data</span></dt><dd><p>This is a pointer for holding module private data.
+You can alloc data with connection life time on the handle->conn->mem_ctx TALLOC_CTX.
+But you can also manage the memory allocation yourself.</p></dd><dt><span class="term">free_data</span></dt><dd><p>This is a function pointer to a function that free's the module private data.
+If you talloc your private data on the TALLOC_CTX handle->conn->mem_ctx,
+you can set this function pointer to NULL.</p></dd></dl></div><p>Some useful MACROS for handle private data.
+</p><pre class="programlisting">
+#define SMB_VFS_HANDLE_GET_DATA(handle, datap, type, ret) { \
+ if (!(handle)||((datap=(type *)(handle)->data)==NULL)) { \
+ DEBUG(0,("%s() failed to get vfs_handle->data!\n",FUNCTION_MACRO)); \
+ ret; \
+ } \
+}
+
+#define SMB_VFS_HANDLE_SET_DATA(handle, datap, free_fn, type, ret) { \
+ if (!(handle)) { \
+ DEBUG(0,("%s() failed to set handle->data!\n",FUNCTION_MACRO)); \
+ ret; \
+ } else { \
+ if ((handle)->free_data) { \
+ (handle)->free_data(&(handle)->data); \
+ } \
+ (handle)->data = (void *)datap; \
+ (handle)->free_data = free_fn; \
+ } \
+}
+
+#define SMB_VFS_HANDLE_FREE_DATA(handle) { \
+ if ((handle) && (handle)->free_data) { \
+ (handle)->free_data(&(handle)->data); \
+ } \
+}
+</pre><p>How SMB_VFS_LAYER_TRANSPARENT functions can call the SMB_VFS_LAYER_OPAQUE functions.</p><p>The easiest way to do this is to use the SMB_VFS_OPAQUE_* macros.
+</p><pre class="programlisting">
+...
+/* File operations */
+#define SMB_VFS_OPAQUE_OPEN(conn, fname, flags, mode) \
+ ((conn)->vfs_opaque.ops.open(\
+ (conn)->vfs_opaque.handles.open,\
+ (conn), (fname), (flags), (mode)))
+#define SMB_VFS_OPAQUE_CLOSE(fsp, fd) \
+ ((fsp)->conn->vfs_opaque.ops.close(\
+ (fsp)->conn->vfs_opaque.handles.close,\
+ (fsp), (fd)))
+#define SMB_VFS_OPAQUE_READ(fsp, fd, data, n) \
+ ((fsp)->conn->vfs_opaque.ops.read(\
+ (fsp)->conn->vfs_opaque.handles.read,\
+ (fsp), (fd), (data), (n)))
+#define SMB_VFS_OPAQUE_WRITE(fsp, fd, data, n) \
+ ((fsp)->conn->vfs_opaque.ops.write(\
+ (fsp)->conn->vfs_opaque.handles.write,\
+ (fsp), (fd), (data), (n)))
+#define SMB_VFS_OPAQUE_LSEEK(fsp, fd, offset, whence) \
+ ((fsp)->conn->vfs_opaque.ops.lseek(\
+ (fsp)->conn->vfs_opaque.handles.lseek,\
+ (fsp), (fd), (offset), (whence)))
+#define SMB_VFS_OPAQUE_SENDFILE(tofd, fsp, fromfd, header, offset, count) \
+ ((fsp)->conn->vfs_opaque.ops.sendfile(\
+ (fsp)->conn->vfs_opaque.handles.sendfile,\
+ (tofd), (fsp), (fromfd), (header), (offset), (count)))
+...
+</pre><p>How SMB_VFS_LAYER_TRANSPARENT functions can call the next modules functions.</p><p>The easiest way to do this is to use the SMB_VFS_NEXT_* macros.
+</p><pre class="programlisting">
+...
+/* File operations */
+#define SMB_VFS_NEXT_OPEN(handle, conn, fname, flags, mode) \
+ ((handle)->vfs_next.ops.open(\
+ (handle)->vfs_next.handles.open,\
+ (conn), (fname), (flags), (mode)))
+#define SMB_VFS_NEXT_CLOSE(handle, fsp, fd) \
+ ((handle)->vfs_next.ops.close(\
+ (handle)->vfs_next.handles.close,\
+ (fsp), (fd)))
+#define SMB_VFS_NEXT_READ(handle, fsp, fd, data, n) \
+ ((handle)->vfs_next.ops.read(\
+ (handle)->vfs_next.handles.read,\
+ (fsp), (fd), (data), (n)))
+#define SMB_VFS_NEXT_WRITE(handle, fsp, fd, data, n) \
+ ((handle)->vfs_next.ops.write(\
+ (handle)->vfs_next.handles.write,\
+ (fsp), (fd), (data), (n)))
+#define SMB_VFS_NEXT_LSEEK(handle, fsp, fd, offset, whence) \
+ ((handle)->vfs_next.ops.lseek(\
+ (handle)->vfs_next.handles.lseek,\
+ (fsp), (fd), (offset), (whence)))
+#define SMB_VFS_NEXT_SENDFILE(handle, tofd, fsp, fromfd, header, offset, count) \
+ ((handle)->vfs_next.ops.sendfile(\
+ (handle)->vfs_next.handles.sendfile,\
+ (tofd), (fsp), (fromfd), (header), (offset), (count)))
+...
+</pre></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2525842"></a>Upgrading to the New VFS Interface</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2525848"></a>Upgrading from 2.2.* and 3.0aplha modules</h3></div></div></div><div class="orderedlist"><ol type="1"><li><p>
+Add "vfs_handle_struct *handle, " as first parameter to all vfs operation functions.
+e.g. example_connect(connection_struct *conn, const char *service, const char *user);
+-> example_connect(vfs_handle_struct *handle, connection_struct *conn, const char *service, const char *user);
+</p></li><li><p>
+Replace "default_vfs_ops." with "smb_vfs_next_".
+e.g. default_vfs_ops.connect(conn, service, user);
+-> smb_vfs_next_connect(conn, service, user);
+</p></li><li><p>
+Uppercase all "smb_vfs_next_*" functions.
+e.g. smb_vfs_next_connect(conn, service, user);
+-> SMB_VFS_NEXT_CONNECT(conn, service, user);
+</p></li><li><p>
+Add "handle, " as first parameter to all SMB_VFS_NEXT_*() calls.
+e.g. SMB_VFS_NEXT_CONNECT(conn, service, user);
+-> SMB_VFS_NEXT_CONNECT(handle, conn, service, user);
+</p></li><li><p>
+(Only for 2.2.* modules)
+Convert the old struct vfs_ops example_ops to
+a vfs_op_tuple example_op_tuples[] array.
+e.g.
+</p><pre class="programlisting">
+struct vfs_ops example_ops = {
+ /* Disk operations */
+ example_connect, /* connect */
+ example_disconnect, /* disconnect */
+ NULL, /* disk free *
+ /* Directory operations */
+ NULL, /* opendir */
+ NULL, /* readdir */
+ NULL, /* mkdir */
+ NULL, /* rmdir */
+ NULL, /* closedir */
+ /* File operations */
+ NULL, /* open */
+ NULL, /* close */
+ NULL, /* read */
+ NULL, /* write */
+ NULL, /* lseek */
+ NULL, /* sendfile */
+ NULL, /* rename */
+ NULL, /* fsync */
+ example_stat, /* stat */
+ example_fstat, /* fstat */
+ example_lstat, /* lstat */
+ NULL, /* unlink */
+ NULL, /* chmod */
+ NULL, /* fchmod */
+ NULL, /* chown */
+ NULL, /* fchown */
+ NULL, /* chdir */
+ NULL, /* getwd */
+ NULL, /* utime */
+ NULL, /* ftruncate */
+ NULL, /* lock */
+ NULL, /* symlink */
+ NULL, /* readlink */
+ NULL, /* link */
+ NULL, /* mknod */
+ NULL, /* realpath */
+ NULL, /* fget_nt_acl */
+ NULL, /* get_nt_acl */
+ NULL, /* fset_nt_acl */
+ NULL, /* set_nt_acl */
+
+ NULL, /* chmod_acl */
+ NULL, /* fchmod_acl */
+
+ NULL, /* sys_acl_get_entry */
+ NULL, /* sys_acl_get_tag_type */
+ NULL, /* sys_acl_get_permset */
+ NULL, /* sys_acl_get_qualifier */
+ NULL, /* sys_acl_get_file */
+ NULL, /* sys_acl_get_fd */
+ NULL, /* sys_acl_clear_perms */
+ NULL, /* sys_acl_add_perm */
+ NULL, /* sys_acl_to_text */
+ NULL, /* sys_acl_init */
+ NULL, /* sys_acl_create_entry */
+ NULL, /* sys_acl_set_tag_type */
+ NULL, /* sys_acl_set_qualifier */
+ NULL, /* sys_acl_set_permset */
+ NULL, /* sys_acl_valid */
+ NULL, /* sys_acl_set_file */
+ NULL, /* sys_acl_set_fd */
+ NULL, /* sys_acl_delete_def_file */
+ NULL, /* sys_acl_get_perm */
+ NULL, /* sys_acl_free_text */
+ NULL, /* sys_acl_free_acl */
+ NULL /* sys_acl_free_qualifier */
+};
+</pre><p>
+->
+</p><pre class="programlisting">
+static vfs_op_tuple example_op_tuples[] = {
+ {SMB_VFS_OP(example_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
+ {SMB_VFS_OP(example_disconnect), SMB_VFS_OP_DISCONNECT, SMB_VFS_LAYER_TRANSPARENT},
+
+ {SMB_VFS_OP(example_fstat), SMB_VFS_OP_FSTAT, SMB_VFS_LAYER_TRANSPARENT},
+ {SMB_VFS_OP(example_stat), SMB_VFS_OP_STAT, SMB_VFS_LAYER_TRANSPARENT},
+ {SMB_VFS_OP(example_lstat), SMB_VFS_OP_LSTAT, SMB_VFS_LAYER_TRANSPARENT},
+
+ {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
+};
+</pre><p>
+</p></li><li><p>
+Move the example_op_tuples[] array to the end of the file.
+</p></li><li><p>
+Add the init_module() function at the end of the file.
+e.g.
+</p><pre class="programlisting">
+NTSTATUS init_module(void)
+{
+ return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,"example",example_op_tuples);
+}
+</pre><p>
+</p></li><li><p>
+Check if your vfs_init() function does more then just prepare the vfs_ops structs or
+remember the struct smb_vfs_handle_struct.
+</p><table class="simplelist" border="0" summary="Simple list"><tr><td>If NOT you can remove the vfs_init() function.</td></tr><tr><td>If YES decide if you want to move the code to the example_connect() operation or to the init_module(). And then remove vfs_init().
+ e.g. a debug class registration should go into init_module() and the allocation of private data should go to example_connect().</td></tr></table><p>
+</p></li><li><p>
+(Only for 3.0alpha* modules)
+Check if your vfs_done() function contains needed code.
+</p><table class="simplelist" border="0" summary="Simple list"><tr><td>If NOT you can remove the vfs_done() function.</td></tr><tr><td>If YES decide if you can move the code to the example_disconnect() operation. Otherwise register a SMB_EXIT_EVENT with smb_register_exit_event(); (Described in the <a href="modules.html" title="Chapter 8. Modules">modules section</a>) And then remove vfs_done(). e.g. the freeing of private data should go to example_disconnect().
+</td></tr></table><p>
+</p></li><li><p>
+Check if you have any global variables left.
+Decide if it wouldn't be better to have this data on a connection basis.
+</p><table class="simplelist" border="0" summary="Simple list"><tr><td>If NOT leave them as they are. (e.g. this could be the variable for the private debug class.)</td></tr><tr><td>If YES pack all this data into a struct. You can use handle->data to point to such a struct on a per connection basis.</td></tr></table><p>
+
+ e.g. if you have such a struct:
+</p><pre class="programlisting">
+struct example_privates {
+ char *some_string;
+ int db_connection;
+};
+</pre><p>
+first way of doing it:
+</p><pre class="programlisting">
+static int example_connect(vfs_handle_struct *handle,
+ connection_struct *conn, const char *service,
+ const char* user)
+{
+ struct example_privates *data = NULL;
+
+ /* alloc our private data */
+ data = (struct example_privates *)talloc_zero(conn->mem_ctx, sizeof(struct example_privates));
+ if (!data) {
+ DEBUG(0,("talloc_zero() failed\n"));
+ return -1;
+ }
+
+ /* init out private data */
+ data->some_string = talloc_strdup(conn->mem_ctx,"test");
+ if (!data->some_string) {
+ DEBUG(0,("talloc_strdup() failed\n"));
+ return -1;
+ }
+
+ data->db_connection = open_db_conn();
+
+ /* and now store the private data pointer in handle->data
+ * we don't need to specify a free_function here because
+ * we use the connection TALLOC context.
+ * (return -1 if something failed.)
+ */
+ VFS_HANDLE_SET_DATA(handle, data, NULL, struct example_privates, return -1);
+
+ return SMB_VFS_NEXT_CONNECT(handle,conn,service,user);
+}
+
+static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
+{
+ struct example_privates *data = NULL;
+
+ /* get the pointer to our private data
+ * return -1 if something failed
+ */
+ SMB_VFS_HANDLE_GET_DATA(handle, data, struct example_privates, return -1);
+
+ /* do something here...*/
+ DEBUG(0,("some_string: %s\n",data->some_string));
+
+ return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
+}
+</pre><p>
+second way of doing it:
+</p><pre class="programlisting">
+static void free_example_privates(void **datap)
+{
+ struct example_privates *data = (struct example_privates *)*datap;
+
+ SAFE_FREE(data->some_string);
+ SAFE_FREE(data);
+
+ *datap = NULL;
+
+ return;
+}
+
+static int example_connect(vfs_handle_struct *handle,
+ connection_struct *conn, const char *service,
+ const char* user)
+{
+ struct example_privates *data = NULL;
+
+ /* alloc our private data */
+ data = (struct example_privates *)malloc(sizeof(struct example_privates));
+ if (!data) {
+ DEBUG(0,("malloc() failed\n"));
+ return -1;
+ }
+
+ /* init out private data */
+ data->some_string = strdup("test");
+ if (!data->some_string) {
+ DEBUG(0,("strdup() failed\n"));
+ return -1;
+ }
+
+ data->db_connection = open_db_conn();
+
+ /* and now store the private data pointer in handle->data
+ * we need to specify a free_function because we used malloc() and strdup().
+ * (return -1 if something failed.)
+ */
+ SMB_VFS_HANDLE_SET_DATA(handle, data, free_example_privates, struct example_privates, return -1);
+
+ return SMB_VFS_NEXT_CONNECT(handle,conn,service,user);
+}
+
+static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
+{
+ struct example_privates *data = NULL;
+
+ /* get the pointer to our private data
+ * return -1 if something failed
+ */
+ SMB_VFS_HANDLE_GET_DATA(handle, data, struct example_privates, return -1);
+
+ /* do something here...*/
+ DEBUG(0,("some_string: %s\n",data->some_string));
+
+ return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
+}
+</pre><p>
+</p></li><li><p>
+To make it easy to build 3rd party modules it would be usefull to provide
+configure.in, (configure), install.sh and Makefile.in with the module.
+(Take a look at the example in <code class="filename">examples/VFS</code>.)
+</p><p>
+The configure script accepts <code class="option">--with-samba-source</code> to specify
+the path to the samba source tree.
+It also accept <code class="option">--enable-developer</code> which lets the compiler
+give you more warnings.
+</p><p>
+The idea is that you can extend this
+<code class="filename">configure.in</code> and <code class="filename">Makefile.in</code> scripts
+for your module.
+</p></li><li><p>
+Compiling & Testing...
+</p><table class="simplelist" border="0" summary="Simple list"><tr><td><strong class="userinput"><code>./configure <code class="option">--enable-developer</code></code></strong> ...</td></tr><tr><td><strong class="userinput"><code>make</code></strong></td></tr><tr><td>Try to fix all compiler warnings</td></tr><tr><td><strong class="userinput"><code>make</code></strong></td></tr><tr><td>Testing, Testing, Testing ...</td></tr></table><p>
+</p></li></ol></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2526400"></a>Some Notes</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2526406"></a>Implement TRANSPARENT functions</h3></div></div></div><p>
+Avoid writing functions like this:
+
+</p><pre class="programlisting">
+static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
+{
+ return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
+}
+</pre><p>
+
+Overload only the functions you really need to!
+</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2526426"></a>Implement OPAQUE functions</h3></div></div></div><p>
+If you want to just implement a better version of a
+default samba opaque function
+(e.g. like a disk_free() function for a special filesystem)
+it's ok to just overload that specific function.
+</p><p>
+If you want to implement a database filesystem or
+something different from a posix filesystem.
+Make sure that you overload every vfs operation!!!
+</p><p>
+Functions your FS does not support should be overloaded by something like this:
+e.g. for a readonly filesystem.
+</p><pre class="programlisting">
+static int example_rename(vfs_handle_struct *handle, connection_struct *conn,
+ char *oldname, char *newname)
+{
+ DEBUG(10,("function rename() not allowed on vfs 'example'\n"));
+ errno = ENOSYS;
+ return -1;
+}
+</pre></div></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="rpc-plugin.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="pt03.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="parsing.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Chapter 9. RPC Pluggable Modules </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 11. The smb.conf file</td></tr></table></div></body></html>
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