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1<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 V1.74.0"><link rel="home" 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">&lt;<a class="email" href="mailto:ab@samba.org">ab@samba.org</a>&gt;</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">&lt;<a class="email" href="mailto:metze@samba.org">metze@samba.org</a>&gt;</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#id2559092">The Samba (Posix) VFS layer</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2559133">The general interface</a></span></dt><dt><span class="sect2"><a href="vfs.html#id2559444">Possible VFS operation layers</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id2559505">The Interaction between the Samba VFS subsystem and the modules</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2559511">Initialization and registration</a></span></dt><dt><span class="sect2"><a href="vfs.html#id2559656">How the Modules handle per connection data</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id2559857">Upgrading to the New VFS Interface</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2559863">Upgrading from 2.2.* and 3.0alpha modules</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id2560268">Some Notes</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id2560273">Implement TRANSPARENT functions</a></span></dt><dt><span class="sect2"><a href="vfs.html#id2560292">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="id2559092"></a>The Samba (Posix) VFS layer</h2></div></div></div><p>While most of Samba deployments are done using POSIX-compatible
2operating systems, there is clearly more to a file system than what is
3required by POSIX when it comes to adopting semantics of NT file
4system. Since Samba 2.2 all file-system related operations go through
5an abstraction layer for virtual file system (VFS) that is modelled
6after both POSIX and additional functions needed to transform NTFS
7semantics.
8</p><p>
9This abstraction layer now provides more features than a regular POSIX
10file system could fill in. It is not required that all of them should
11be implemented by your particular file system. However, when those
12features are available, Samba would advertize them to a CIFS client
13and they might be used by an application and in case of Windows client
14that might mean a client expects even more additional functionality
15when it encounters those features. There is a practical reason to
16allow handling of this snowfall without modifying the Samba core and
17it is fulfilled by providing an infrastructure to dynamically load VFS
18modules at run time.
19</p><p>Each VFS module could implement a number of VFS operations. The
20way it does it is irrelevant, only two things actually matter: whether
21specific implementation wants to cooperate with other modules'
22implementations or not, and whether module needs to store additional
23information that is specific to a context it is operating in. Multiple
24VFS modules could be loaded at the same time and it is even possible
25to load several instances of the same VFS module with different
26parameters.
27</p><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2559133"></a>The general interface</h3></div></div></div><p>A VFS module has three major components:
28</p><div class="itemizedlist"><ul type="disc"><li><span class="emphasis"><em>An initialization function</em></span> that is
29called during the module load to register implemented
30operations.</li><li><span class="emphasis"><em>An operations table</em></span> representing a
31mapping between statically defined module functions and VFS layer
32operations.</li><li><span class="emphasis"><em>Module functions</em></span> that do actual
33work.</li></ul></div><p>
34</p><p>While this structure has been first applied to the VFS
35subsystem, it is now commonly used across all Samba 3 subsystems that
36support loadable modules. In fact, one module could provide a number
37of interfaces to different subsystems by exposing different
38<span class="emphasis"><em>operation tables</em></span> through separate
39<span class="emphasis"><em>initialization functions</em></span>.</p><p><span class="emphasis"><em>An initialization function</em></span> is used to
40register module with Samba run-time. As Samba internal structures and
41API are changed over lifetime, each released version has a VFS
42interface version that is increased as VFS development progresses or
43any of underlying Samba structures are changed in binary-incompatible
44way. When VFS module is compiled in, VFS interface version of that
45Samba environment is embedded into the module's binary object and is
46checked by the Samba core upon module load. If VFS interface number
47reported by the module isn't the same Samba core knows about, version
48conflict is detected and module dropped to avoid any potential memory
49corruption when accessing (changed) Samba structures.
50</p><p>Therefore, initialization function passes three parameters to the
51VFS registration function, <code class="literal">smb_register_vfs()</code>
52</p><div class="itemizedlist"><ul type="disc"><li><span class="emphasis"><em>interface version number</em></span>, as constant
53 <code class="literal">SMB_VFS_INTERFACE_VERSION</code>, </li><li><span class="emphasis"><em>module name</em></span>, under which Samba core
54 will know it, and</li><li><span class="emphasis"><em>an operations' table</em></span>.</li></ul></div><p>
55</p><p>The <span class="emphasis"><em>operations' table</em></span> defines which
56functions in the module would correspond to specific VFS operations
57and how those functions would co-operate with the rest of VFS
58subsystem. Each operation could perform in a following ways:
59</p><div class="itemizedlist"><ul type="disc"><li><span class="emphasis"><em>transparent</em></span>, meaning that while
60 operation is overriden, the module will still call a previous
61 implementation, before or after its own action. This mode is
62 indicated by the constant
63 <code class="literal">SMB_VFS_LAYER_TRANSPARENT</code>;
64 </li><li><span class="emphasis"><em>opaque</em></span>, for the implementations that
65 are terminating sequence of actions. For example, it is used to
66 implement POSIX operation on top of non-POSIX file system or even
67 not a file system at all, like a database for a personal audio
68 collection. Use constant <code class="literal">SMB_VFS_LAYER_OPAQUE</code> for
69 this mode;</li><li><span class="emphasis"><em>splitter</em></span>, a way when some file system
70 activity is done in addition to the transparently calling previous
71 implentation. This usually involves mangling the result of that call
72 before returning it back to the caller. This mode is selected by
73 <code class="literal">SMB_VFS_LAYER_SPLITTER</code> constant;</li><li><span class="emphasis"><em>logger</em></span> does not change anything or
74 performs any additional VFS operations. When
75 <span class="emphasis"><em>logger</em></span> module acts, information about
76 operations is logged somewhere using an external facility (or
77 Samba's own debugging tools) but not the VFS layer. In order to
78 describe this type of activity use constant
79 <code class="literal">SMB_VFS_LAYER_LOGGER</code>;
80 </li><li>On contrary, <span class="emphasis"><em>scanner</em></span> module does call
81 other VFS operations while processing the data that goes through the
82 system. This type of operation is indicated by the
83 <code class="literal">SMB_VFS_LAYER_SCANNER</code> constant.</li></ul></div><p>
84</p><p>Fundamentally, there are three types:
85<span class="emphasis"><em>transparent</em></span>, <span class="emphasis"><em>opaque</em></span>, and
86<span class="emphasis"><em>logger</em></span>. <span class="emphasis"><em>Splitter</em></span> and
87<span class="emphasis"><em>scanner</em></span> may confuse developers (and indeed they
88are confused as our experience has shown) but this separation is to
89better expose the nature of a module's actions. Most of modules
90developed so far are either one of those three fundamental types with
91transparent and opaque being prevalent.
92</p><p>
93Each VFS operation has a vfs_op_type, a function pointer and a handle
94pointer in the struct vfs_ops and tree macros to make it easier to
95call the operations. (Take a look at
96<code class="filename">include/vfs.h</code> and
97<code class="filename">include/vfs_macros.h</code>.)
98</p><pre class="programlisting">
99typedef enum _vfs_op_type {
100 SMB_VFS_OP_NOOP = -1,
101
102 ...
103
104 /* File operations */
105
106 SMB_VFS_OP_OPEN,
107 SMB_VFS_OP_CLOSE,
108 SMB_VFS_OP_READ,
109 SMB_VFS_OP_WRITE,
110 SMB_VFS_OP_LSEEK,
111 SMB_VFS_OP_SENDFILE,
112
113 ...
114
115 SMB_VFS_OP_LAST
116} vfs_op_type;
117</pre><p>This struct contains the function and handle pointers for all operations.</p><pre class="programlisting">
118struct vfs_ops {
119 struct vfs_fn_pointers {
120 ...
121
122 /* File operations */
123
124 int (*open)(struct vfs_handle_struct *handle,
125 struct connection_struct *conn,
126 const char *fname, int flags, mode_t mode);
127 int (*close)(struct vfs_handle_struct *handle,
128 struct files_struct *fsp, int fd);
129 ssize_t (*read)(struct vfs_handle_struct *handle,
130 struct files_struct *fsp, int fd, void *data, size_t n);
131 ssize_t (*write)(struct vfs_handle_struct *handle,
132 struct files_struct *fsp, int fd,
133 const void *data, size_t n);
134 SMB_OFF_T (*lseek)(struct vfs_handle_struct *handle,
135 struct files_struct *fsp, int fd,
136 SMB_OFF_T offset, int whence);
137 ssize_t (*sendfile)(struct vfs_handle_struct *handle,
138 int tofd, files_struct *fsp, int fromfd,
139 const DATA_BLOB *header, SMB_OFF_T offset, size_t count);
140
141 ...
142 } ops;
143
144 struct vfs_handles_pointers {
145 ...
146
147 /* File operations */
148
149 struct vfs_handle_struct *open;
150 struct vfs_handle_struct *close;
151 struct vfs_handle_struct *read;
152 struct vfs_handle_struct *write;
153 struct vfs_handle_struct *lseek;
154 struct vfs_handle_struct *sendfile;
155
156 ...
157 } handles;
158};
159</pre><p>
160This macros SHOULD be used to call any vfs operation.
161DO NOT ACCESS conn-&gt;vfs.ops.* directly !!!
162</p><pre class="programlisting">
163...
164
165/* File operations */
166#define SMB_VFS_OPEN(conn, fname, flags, mode) \
167 ((conn)-&gt;vfs.ops.open((conn)-&gt;vfs.handles.open,\
168 (conn), (fname), (flags), (mode)))
169#define SMB_VFS_CLOSE(fsp, fd) \
170 ((fsp)-&gt;conn-&gt;vfs.ops.close(\
171 (fsp)-&gt;conn-&gt;vfs.handles.close, (fsp), (fd)))
172#define SMB_VFS_READ(fsp, fd, data, n) \
173 ((fsp)-&gt;conn-&gt;vfs.ops.read(\
174 (fsp)-&gt;conn-&gt;vfs.handles.read,\
175 (fsp), (fd), (data), (n)))
176#define SMB_VFS_WRITE(fsp, fd, data, n) \
177 ((fsp)-&gt;conn-&gt;vfs.ops.write(\
178 (fsp)-&gt;conn-&gt;vfs.handles.write,\
179 (fsp), (fd), (data), (n)))
180#define SMB_VFS_LSEEK(fsp, fd, offset, whence) \
181 ((fsp)-&gt;conn-&gt;vfs.ops.lseek(\
182 (fsp)-&gt;conn-&gt;vfs.handles.lseek,\
183 (fsp), (fd), (offset), (whence)))
184#define SMB_VFS_SENDFILE(tofd, fsp, fromfd, header, offset, count) \
185 ((fsp)-&gt;conn-&gt;vfs.ops.sendfile(\
186 (fsp)-&gt;conn-&gt;vfs.handles.sendfile,\
187 (tofd), (fsp), (fromfd), (header), (offset), (count)))
188
189...
190</pre></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2559444"></a>Possible VFS operation layers</h3></div></div></div><p>
191These values are used by the VFS subsystem when building the conn-&gt;vfs
192and conn-&gt;vfs_opaque structs for a connection with multiple VFS modules.
193Internally, Samba differentiates only opaque and transparent layers at this process.
194Other types are used for providing better diagnosing facilities.
195</p><p>
196Most modules will provide transparent layers. Opaque layer is for modules
197which implement actual file system calls (like DB-based VFS). For example,
198default POSIX VFS which is built in into Samba is an opaque VFS module.
199</p><p>
200Other layer types (logger, splitter, scanner) were designed to provide different
201degree of transparency and for diagnosing VFS module behaviour.
202</p><p>
203Each module can implement several layers at the same time provided that only
204one layer is used per each operation.
205</p><pre class="programlisting">
206typedef enum _vfs_op_layer {
207 SMB_VFS_LAYER_NOOP = -1, /* - For using in VFS module to indicate end of array */
208 /* of operations description */
209 SMB_VFS_LAYER_OPAQUE = 0, /* - Final level, does not call anything beyond itself */
210 SMB_VFS_LAYER_TRANSPARENT, /* - Normal operation, calls underlying layer after */
211 /* possibly changing passed data */
212 SMB_VFS_LAYER_LOGGER, /* - Logs data, calls underlying layer, logging may not */
213 /* use Samba VFS */
214 SMB_VFS_LAYER_SPLITTER, /* - Splits operation, calls underlying layer _and_ own facility, */
215 /* then combines result */
216 SMB_VFS_LAYER_SCANNER /* - Checks data and possibly initiates additional */
217 /* file activity like logging to files _inside_ samba VFS */
218} vfs_op_layer;
219</pre></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2559505"></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="id2559511"></a>Initialization and registration</h3></div></div></div><p>
220As each Samba module a VFS module should have a
221</p><pre class="programlisting">NTSTATUS vfs_example_init(void);</pre><p> function if it's staticly linked to samba or
222</p><pre class="programlisting">NTSTATUS init_module(void);</pre><p> function if it's a shared module.
223</p><p>
224This should be the only non static function inside the module.
225Global variables should also be static!
226</p><p>
227The module should register its functions via the
228</p><pre class="programlisting">
229NTSTATUS smb_register_vfs(int version, const char *name, vfs_op_tuple *vfs_op_tuples);
230</pre><p> function.
231</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
232<code class="literal">vfs objects</code> parameter to use this module.</p></dd><dt><span class="term">vfs_op_tuples</span></dt><dd><p>
233this is an array of vfs_op_tuple's.
234(vfs_op_tuples is descripted in details below.)
235</p></dd></dl></div><p>
236For each operation the module wants to provide it has a entry in the
237vfs_op_tuple array.
238</p><pre class="programlisting">
239typedef struct _vfs_op_tuple {
240 void* op;
241 vfs_op_type type;
242 vfs_op_layer layer;
243} vfs_op_tuple;
244</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">
245static vfs_op_tuple example_op_tuples[] = {
246 {SMB_VFS_OP(example_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
247 {SMB_VFS_OP(example_disconnect), SMB_VFS_OP_DISCONNECT, SMB_VFS_LAYER_TRANSPARENT},
248
249 {SMB_VFS_OP(example_rename), SMB_VFS_OP_RENAME, SMB_VFS_LAYER_OPAQUE},
250
251 /* This indicates the end of the array */
252 {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
253};
254
255NTSTATUS init_module(void)
256{
257 return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, "example", example_op_tuples);
258}
259</pre></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2559656"></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.
260</p><pre class="programlisting">
261typedef struct vfs_handle_struct {
262 struct vfs_handle_struct *next, *prev;
263 const char *param;
264 struct vfs_ops vfs_next;
265 struct connection_struct *conn;
266 void *data;
267 void (*free_data)(void **data);
268} vfs_handle_struct;
269</pre><div class="variablelist"><dl><dt><span class="term">param</span></dt><dd><p>this is the module parameter specified in the <code class="literal">vfs objects</code> 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.
270Use the SMB_VFS_NEXT_* macros to call a next module operations and
271don't access handle-&gt;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.
272You can alloc data with connection life time on the handle-&gt;conn-&gt;mem_ctx TALLOC_CTX.
273But 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.
274If you talloc your private data on the TALLOC_CTX handle-&gt;conn-&gt;mem_ctx,
275you can set this function pointer to NULL.</p></dd></dl></div><p>Some useful MACROS for handle private data.
276</p><pre class="programlisting">
277#define SMB_VFS_HANDLE_GET_DATA(handle, datap, type, ret) { \
278 if (!(handle)||((datap=(type *)(handle)-&gt;data)==NULL)) { \
279 DEBUG(0,("%s() failed to get vfs_handle-&gt;data!\n",FUNCTION_MACRO)); \
280 ret; \
281 } \
282}
283
284#define SMB_VFS_HANDLE_SET_DATA(handle, datap, free_fn, type, ret) { \
285 if (!(handle)) { \
286 DEBUG(0,("%s() failed to set handle-&gt;data!\n",FUNCTION_MACRO)); \
287 ret; \
288 } else { \
289 if ((handle)-&gt;free_data) { \
290 (handle)-&gt;free_data(&amp;(handle)-&gt;data); \
291 } \
292 (handle)-&gt;data = (void *)datap; \
293 (handle)-&gt;free_data = free_fn; \
294 } \
295}
296
297#define SMB_VFS_HANDLE_FREE_DATA(handle) { \
298 if ((handle) &amp;&amp; (handle)-&gt;free_data) { \
299 (handle)-&gt;free_data(&amp;(handle)-&gt;data); \
300 } \
301}
302</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.
303</p><pre class="programlisting">
304...
305/* File operations */
306#define SMB_VFS_OPAQUE_OPEN(conn, fname, flags, mode) \
307 ((conn)-&gt;vfs_opaque.ops.open(\
308 (conn)-&gt;vfs_opaque.handles.open,\
309 (conn), (fname), (flags), (mode)))
310#define SMB_VFS_OPAQUE_CLOSE(fsp, fd) \
311 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.close(\
312 (fsp)-&gt;conn-&gt;vfs_opaque.handles.close,\
313 (fsp), (fd)))
314#define SMB_VFS_OPAQUE_READ(fsp, fd, data, n) \
315 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.read(\
316 (fsp)-&gt;conn-&gt;vfs_opaque.handles.read,\
317 (fsp), (fd), (data), (n)))
318#define SMB_VFS_OPAQUE_WRITE(fsp, fd, data, n) \
319 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.write(\
320 (fsp)-&gt;conn-&gt;vfs_opaque.handles.write,\
321 (fsp), (fd), (data), (n)))
322#define SMB_VFS_OPAQUE_LSEEK(fsp, fd, offset, whence) \
323 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.lseek(\
324 (fsp)-&gt;conn-&gt;vfs_opaque.handles.lseek,\
325 (fsp), (fd), (offset), (whence)))
326#define SMB_VFS_OPAQUE_SENDFILE(tofd, fsp, fromfd, header, offset, count) \
327 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.sendfile(\
328 (fsp)-&gt;conn-&gt;vfs_opaque.handles.sendfile,\
329 (tofd), (fsp), (fromfd), (header), (offset), (count)))
330...
331</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.
332</p><pre class="programlisting">
333...
334/* File operations */
335#define SMB_VFS_NEXT_OPEN(handle, conn, fname, flags, mode) \
336 ((handle)-&gt;vfs_next.ops.open(\
337 (handle)-&gt;vfs_next.handles.open,\
338 (conn), (fname), (flags), (mode)))
339#define SMB_VFS_NEXT_CLOSE(handle, fsp, fd) \
340 ((handle)-&gt;vfs_next.ops.close(\
341 (handle)-&gt;vfs_next.handles.close,\
342 (fsp), (fd)))
343#define SMB_VFS_NEXT_READ(handle, fsp, fd, data, n) \
344 ((handle)-&gt;vfs_next.ops.read(\
345 (handle)-&gt;vfs_next.handles.read,\
346 (fsp), (fd), (data), (n)))
347#define SMB_VFS_NEXT_WRITE(handle, fsp, fd, data, n) \
348 ((handle)-&gt;vfs_next.ops.write(\
349 (handle)-&gt;vfs_next.handles.write,\
350 (fsp), (fd), (data), (n)))
351#define SMB_VFS_NEXT_LSEEK(handle, fsp, fd, offset, whence) \
352 ((handle)-&gt;vfs_next.ops.lseek(\
353 (handle)-&gt;vfs_next.handles.lseek,\
354 (fsp), (fd), (offset), (whence)))
355#define SMB_VFS_NEXT_SENDFILE(handle, tofd, fsp, fromfd, header, offset, count) \
356 ((handle)-&gt;vfs_next.ops.sendfile(\
357 (handle)-&gt;vfs_next.handles.sendfile,\
358 (tofd), (fsp), (fromfd), (header), (offset), (count)))
359...
360</pre></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2559857"></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="id2559863"></a>Upgrading from 2.2.* and 3.0alpha modules</h3></div></div></div><div class="orderedlist"><ol type="1"><li><p>
361Add "vfs_handle_struct *handle, " as first parameter to all vfs operation functions.
362e.g. example_connect(connection_struct *conn, const char *service, const char *user);
363-&gt; example_connect(vfs_handle_struct *handle, connection_struct *conn, const char *service, const char *user);
364</p></li><li><p>
365Replace "default_vfs_ops." with "smb_vfs_next_".
366e.g. default_vfs_ops.connect(conn, service, user);
367-&gt; smb_vfs_next_connect(conn, service, user);
368</p></li><li><p>
369Uppercase all "smb_vfs_next_*" functions.
370e.g. smb_vfs_next_connect(conn, service, user);
371-&gt; SMB_VFS_NEXT_CONNECT(conn, service, user);
372</p></li><li><p>
373Add "handle, " as first parameter to all SMB_VFS_NEXT_*() calls.
374e.g. SMB_VFS_NEXT_CONNECT(conn, service, user);
375-&gt; SMB_VFS_NEXT_CONNECT(handle, conn, service, user);
376</p></li><li><p>
377(Only for 2.2.* modules)
378Convert the old struct vfs_ops example_ops to
379a vfs_op_tuple example_op_tuples[] array.
380e.g.
381</p><pre class="programlisting">
382struct vfs_ops example_ops = {
383 /* Disk operations */
384 example_connect, /* connect */
385 example_disconnect, /* disconnect */
386 NULL, /* disk free *
387 /* Directory operations */
388 NULL, /* opendir */
389 NULL, /* readdir */
390 NULL, /* mkdir */
391 NULL, /* rmdir */
392 NULL, /* closedir */
393 /* File operations */
394 NULL, /* open */
395 NULL, /* close */
396 NULL, /* read */
397 NULL, /* write */
398 NULL, /* lseek */
399 NULL, /* sendfile */
400 NULL, /* rename */
401 NULL, /* fsync */
402 example_stat, /* stat */
403 example_fstat, /* fstat */
404 example_lstat, /* lstat */
405 NULL, /* unlink */
406 NULL, /* chmod */
407 NULL, /* fchmod */
408 NULL, /* chown */
409 NULL, /* fchown */
410 NULL, /* chdir */
411 NULL, /* getwd */
412 NULL, /* utime */
413 NULL, /* ftruncate */
414 NULL, /* lock */
415 NULL, /* symlink */
416 NULL, /* readlink */
417 NULL, /* link */
418 NULL, /* mknod */
419 NULL, /* realpath */
420 NULL, /* fget_nt_acl */
421 NULL, /* get_nt_acl */
422 NULL, /* fset_nt_acl */
423 NULL, /* set_nt_acl */
424
425 NULL, /* chmod_acl */
426 NULL, /* fchmod_acl */
427
428 NULL, /* sys_acl_get_entry */
429 NULL, /* sys_acl_get_tag_type */
430 NULL, /* sys_acl_get_permset */
431 NULL, /* sys_acl_get_qualifier */
432 NULL, /* sys_acl_get_file */
433 NULL, /* sys_acl_get_fd */
434 NULL, /* sys_acl_clear_perms */
435 NULL, /* sys_acl_add_perm */
436 NULL, /* sys_acl_to_text */
437 NULL, /* sys_acl_init */
438 NULL, /* sys_acl_create_entry */
439 NULL, /* sys_acl_set_tag_type */
440 NULL, /* sys_acl_set_qualifier */
441 NULL, /* sys_acl_set_permset */
442 NULL, /* sys_acl_valid */
443 NULL, /* sys_acl_set_file */
444 NULL, /* sys_acl_set_fd */
445 NULL, /* sys_acl_delete_def_file */
446 NULL, /* sys_acl_get_perm */
447 NULL, /* sys_acl_free_text */
448 NULL, /* sys_acl_free_acl */
449 NULL /* sys_acl_free_qualifier */
450};
451</pre><p>
452-&gt;
453</p><pre class="programlisting">
454static vfs_op_tuple example_op_tuples[] = {
455 {SMB_VFS_OP(example_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
456 {SMB_VFS_OP(example_disconnect), SMB_VFS_OP_DISCONNECT, SMB_VFS_LAYER_TRANSPARENT},
457
458 {SMB_VFS_OP(example_fstat), SMB_VFS_OP_FSTAT, SMB_VFS_LAYER_TRANSPARENT},
459 {SMB_VFS_OP(example_stat), SMB_VFS_OP_STAT, SMB_VFS_LAYER_TRANSPARENT},
460 {SMB_VFS_OP(example_lstat), SMB_VFS_OP_LSTAT, SMB_VFS_LAYER_TRANSPARENT},
461
462 {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
463};
464</pre><p>
465</p></li><li><p>
466Move the example_op_tuples[] array to the end of the file.
467</p></li><li><p>
468Add the init_module() function at the end of the file.
469e.g.
470</p><pre class="programlisting">
471NTSTATUS init_module(void)
472{
473 return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,"example",example_op_tuples);
474}
475</pre><p>
476</p></li><li><p>
477Check if your vfs_init() function does more then just prepare the vfs_ops structs or
478remember the struct smb_vfs_handle_struct.
479</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().
480 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>
481</p></li><li><p>
482(Only for 3.0alpha* modules)
483Check if your vfs_done() function contains needed code.
484</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 class="link" 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().
485</td></tr></table><p>
486</p></li><li><p>
487Check if you have any global variables left.
488Decide if it wouldn't be better to have this data on a connection basis.
489</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-&gt;data to point to such a struct on a per connection basis.</td></tr></table><p>
490
491 e.g. if you have such a struct:
492</p><pre class="programlisting">
493struct example_privates {
494 char *some_string;
495 int db_connection;
496};
497</pre><p>
498first way of doing it:
499</p><pre class="programlisting">
500static int example_connect(vfs_handle_struct *handle,
501 connection_struct *conn, const char *service,
502 const char* user)
503{
504 struct example_privates *data = NULL;
505
506 /* alloc our private data */
507 data = (struct example_privates *)talloc_zero(conn-&gt;mem_ctx, sizeof(struct example_privates));
508 if (!data) {
509 DEBUG(0,("talloc_zero() failed\n"));
510 return -1;
511 }
512
513 /* init out private data */
514 data-&gt;some_string = talloc_strdup(conn-&gt;mem_ctx,"test");
515 if (!data-&gt;some_string) {
516 DEBUG(0,("talloc_strdup() failed\n"));
517 return -1;
518 }
519
520 data-&gt;db_connection = open_db_conn();
521
522 /* and now store the private data pointer in handle-&gt;data
523 * we don't need to specify a free_function here because
524 * we use the connection TALLOC context.
525 * (return -1 if something failed.)
526 */
527 VFS_HANDLE_SET_DATA(handle, data, NULL, struct example_privates, return -1);
528
529 return SMB_VFS_NEXT_CONNECT(handle,conn,service,user);
530}
531
532static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
533{
534 struct example_privates *data = NULL;
535
536 /* get the pointer to our private data
537 * return -1 if something failed
538 */
539 SMB_VFS_HANDLE_GET_DATA(handle, data, struct example_privates, return -1);
540
541 /* do something here...*/
542 DEBUG(0,("some_string: %s\n",data-&gt;some_string));
543
544 return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
545}
546</pre><p>
547second way of doing it:
548</p><pre class="programlisting">
549static void free_example_privates(void **datap)
550{
551 struct example_privates *data = (struct example_privates *)*datap;
552
553 SAFE_FREE(data-&gt;some_string);
554 SAFE_FREE(data);
555
556 *datap = NULL;
557
558 return;
559}
560
561static int example_connect(vfs_handle_struct *handle,
562 connection_struct *conn, const char *service,
563 const char* user)
564{
565 struct example_privates *data = NULL;
566
567 /* alloc our private data */
568 data = (struct example_privates *)malloc(sizeof(struct example_privates));
569 if (!data) {
570 DEBUG(0,("malloc() failed\n"));
571 return -1;
572 }
573
574 /* init out private data */
575 data-&gt;some_string = strdup("test");
576 if (!data-&gt;some_string) {
577 DEBUG(0,("strdup() failed\n"));
578 return -1;
579 }
580
581 data-&gt;db_connection = open_db_conn();
582
583 /* and now store the private data pointer in handle-&gt;data
584 * we need to specify a free_function because we used malloc() and strdup().
585 * (return -1 if something failed.)
586 */
587 SMB_VFS_HANDLE_SET_DATA(handle, data, free_example_privates, struct example_privates, return -1);
588
589 return SMB_VFS_NEXT_CONNECT(handle,conn,service,user);
590}
591
592static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
593{
594 struct example_privates *data = NULL;
595
596 /* get the pointer to our private data
597 * return -1 if something failed
598 */
599 SMB_VFS_HANDLE_GET_DATA(handle, data, struct example_privates, return -1);
600
601 /* do something here...*/
602 DEBUG(0,("some_string: %s\n",data-&gt;some_string));
603
604 return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
605}
606</pre><p>
607</p></li><li><p>
608To make it easy to build 3rd party modules it would be useful to provide
609configure.in, (configure), install.sh and Makefile.in with the module.
610(Take a look at the example in <code class="filename">examples/VFS</code>.)
611</p><p>
612The configure script accepts <code class="option">--with-samba-source</code> to specify
613the path to the samba source tree.
614It also accept <code class="option">--enable-developer</code> which lets the compiler
615give you more warnings.
616</p><p>
617The idea is that you can extend this
618<code class="filename">configure.in</code> and <code class="filename">Makefile.in</code> scripts
619for your module.
620</p></li><li><p>
621Compiling &amp; Testing...
622</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>
623</p></li></ol></div></div></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2560268"></a>Some Notes</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2560273"></a>Implement TRANSPARENT functions</h3></div></div></div><p>
624Avoid writing functions like this:
625
626</p><pre class="programlisting">
627static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
628{
629 return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
630}
631</pre><p>
632
633Overload only the functions you really need to!
634</p></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id2560292"></a>Implement OPAQUE functions</h3></div></div></div><p>
635If you want to just implement a better version of a
636default samba opaque function
637(e.g. like a disk_free() function for a special filesystem)
638it's ok to just overload that specific function.
639</p><p>
640If you want to implement a database filesystem or
641something different from a posix filesystem.
642Make sure that you overload every vfs operation!!!
643</p><p>
644Functions your FS does not support should be overloaded by something like this:
645e.g. for a readonly filesystem.
646</p><pre class="programlisting">
647static int example_rename(vfs_handle_struct *handle, connection_struct *conn,
648 char *oldname, char *newname)
649{
650 DEBUG(10,("function rename() not allowed on vfs 'example'\n"));
651 errno = ENOSYS;
652 return -1;
653}
654</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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