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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 V1.75.2"><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" title="Chapter 10. VFS Modules"><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#id330849">The Samba (Posix) VFS layer</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id330877">The general interface</a></span></dt><dt><span class="sect2"><a href="vfs.html#id331145">Possible VFS operation layers</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id331195">The Interaction between the Samba VFS subsystem and the modules</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id331201">Initialization and registration</a></span></dt><dt><span class="sect2"><a href="vfs.html#id331328">How the Modules handle per connection data</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id331482">Upgrading to the New VFS Interface</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id331487">Upgrading from 2.2.* and 3.0alpha modules</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id331788">Some Notes</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id331793">Implement TRANSPARENT functions</a></span></dt><dt><span class="sect2"><a href="vfs.html#id331809">Implement OPAQUE functions</a></span></dt></dl></dd></dl></div><div class="sect1" title="The Samba (Posix) VFS layer"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id330849"></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" title="The general interface"><div class="titlepage"><div><div><h3 class="title"><a name="id330877"></a>The general interface</h3></div></div></div><p>A VFS module has three major components:
28</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>An initialization function</em></span> that is
29called during the module load to register implemented
30operations.</p></li><li class="listitem"><p><span class="emphasis"><em>An operations table</em></span> representing a
31mapping between statically defined module functions and VFS layer
32operations.</p></li><li class="listitem"><p><span class="emphasis"><em>Module functions</em></span> that do actual
33 work.</p></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 class="itemizedlist" type="disc"><li class="listitem"><p><span class="emphasis"><em>interface version number</em></span>, as constant
53 <code class="literal">SMB_VFS_INTERFACE_VERSION</code>, </p></li><li class="listitem"><p><span class="emphasis"><em>module name</em></span>, under which Samba core
54 will know it, and</p></li><li class="listitem"><p><span class="emphasis"><em>an operations' table</em></span>.</p></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 class="itemizedlist" type="disc"><li class="listitem"><p><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>;</p></li><li class="listitem"><p><span class="emphasis"><em>opaque</em></span>, for the implementations that
64 are terminating sequence of actions. For example, it is used to
65 implement POSIX operation on top of non-POSIX file system or even
66 not a file system at all, like a database for a personal audio
67 collection. Use constant <code class="literal">SMB_VFS_LAYER_OPAQUE</code> for
68 this mode;</p></li><li class="listitem"><p><span class="emphasis"><em>splitter</em></span>, a way when some file system
69 activity is done in addition to the transparently calling previous
70 implentation. This usually involves mangling the result of that call
71 before returning it back to the caller. This mode is selected by
72 <code class="literal">SMB_VFS_LAYER_SPLITTER</code> constant;</p></li><li class="listitem"><p><span class="emphasis"><em>logger</em></span> does not change anything or
73 performs any additional VFS operations. When
74 <span class="emphasis"><em>logger</em></span> module acts, information about
75 operations is logged somewhere using an external facility (or
76 Samba's own debugging tools) but not the VFS layer. In order to
77 describe this type of activity use constant
78 <code class="literal">SMB_VFS_LAYER_LOGGER</code>;
79 </p></li><li class="listitem"><p>On contrary, <span class="emphasis"><em>scanner</em></span> module does call
80 other VFS operations while processing the data that goes through the
81 system. This type of operation is indicated by the
82 <code class="literal">SMB_VFS_LAYER_SCANNER</code> constant.</p></li></ul></div><p>
83</p><p>Fundamentally, there are three types:
84<span class="emphasis"><em>transparent</em></span>, <span class="emphasis"><em>opaque</em></span>, and
85<span class="emphasis"><em>logger</em></span>. <span class="emphasis"><em>Splitter</em></span> and
86<span class="emphasis"><em>scanner</em></span> may confuse developers (and indeed they
87are confused as our experience has shown) but this separation is to
88better expose the nature of a module's actions. Most of modules
89developed so far are either one of those three fundamental types with
90transparent and opaque being prevalent.
91</p><p>
92Each VFS operation has a vfs_op_type, a function pointer and a handle
93pointer in the struct vfs_ops and tree macros to make it easier to
94call the operations. (Take a look at
95<code class="filename">include/vfs.h</code> and
96<code class="filename">include/vfs_macros.h</code>.)
97</p><pre class="programlisting">
98typedef enum _vfs_op_type {
99 SMB_VFS_OP_NOOP = -1,
100
101 ...
102
103 /* File operations */
104
105 SMB_VFS_OP_OPEN,
106 SMB_VFS_OP_CLOSE,
107 SMB_VFS_OP_READ,
108 SMB_VFS_OP_WRITE,
109 SMB_VFS_OP_LSEEK,
110 SMB_VFS_OP_SENDFILE,
111
112 ...
113
114 SMB_VFS_OP_LAST
115} vfs_op_type;
116</pre><p>This struct contains the function and handle pointers for all operations.</p><pre class="programlisting">
117struct vfs_ops {
118 struct vfs_fn_pointers {
119 ...
120
121 /* File operations */
122
123 int (*open)(struct vfs_handle_struct *handle,
124 struct connection_struct *conn,
125 const char *fname, int flags, mode_t mode);
126 int (*close)(struct vfs_handle_struct *handle,
127 struct files_struct *fsp, int fd);
128 ssize_t (*read)(struct vfs_handle_struct *handle,
129 struct files_struct *fsp, int fd, void *data, size_t n);
130 ssize_t (*write)(struct vfs_handle_struct *handle,
131 struct files_struct *fsp, int fd,
132 const void *data, size_t n);
133 SMB_OFF_T (*lseek)(struct vfs_handle_struct *handle,
134 struct files_struct *fsp, int fd,
135 SMB_OFF_T offset, int whence);
136 ssize_t (*sendfile)(struct vfs_handle_struct *handle,
137 int tofd, files_struct *fsp, int fromfd,
138 const DATA_BLOB *header, SMB_OFF_T offset, size_t count);
139
140 ...
141 } ops;
142
143 struct vfs_handles_pointers {
144 ...
145
146 /* File operations */
147
148 struct vfs_handle_struct *open;
149 struct vfs_handle_struct *close;
150 struct vfs_handle_struct *read;
151 struct vfs_handle_struct *write;
152 struct vfs_handle_struct *lseek;
153 struct vfs_handle_struct *sendfile;
154
155 ...
156 } handles;
157};
158</pre><p>
159This macros SHOULD be used to call any vfs operation.
160DO NOT ACCESS conn-&gt;vfs.ops.* directly !!!
161</p><pre class="programlisting">
162...
163
164/* File operations */
165#define SMB_VFS_OPEN(conn, fname, flags, mode) \
166 ((conn)-&gt;vfs.ops.open((conn)-&gt;vfs.handles.open,\
167 (conn), (fname), (flags), (mode)))
168#define SMB_VFS_CLOSE(fsp, fd) \
169 ((fsp)-&gt;conn-&gt;vfs.ops.close(\
170 (fsp)-&gt;conn-&gt;vfs.handles.close, (fsp), (fd)))
171#define SMB_VFS_READ(fsp, fd, data, n) \
172 ((fsp)-&gt;conn-&gt;vfs.ops.read(\
173 (fsp)-&gt;conn-&gt;vfs.handles.read,\
174 (fsp), (fd), (data), (n)))
175#define SMB_VFS_WRITE(fsp, fd, data, n) \
176 ((fsp)-&gt;conn-&gt;vfs.ops.write(\
177 (fsp)-&gt;conn-&gt;vfs.handles.write,\
178 (fsp), (fd), (data), (n)))
179#define SMB_VFS_LSEEK(fsp, fd, offset, whence) \
180 ((fsp)-&gt;conn-&gt;vfs.ops.lseek(\
181 (fsp)-&gt;conn-&gt;vfs.handles.lseek,\
182 (fsp), (fd), (offset), (whence)))
183#define SMB_VFS_SENDFILE(tofd, fsp, fromfd, header, offset, count) \
184 ((fsp)-&gt;conn-&gt;vfs.ops.sendfile(\
185 (fsp)-&gt;conn-&gt;vfs.handles.sendfile,\
186 (tofd), (fsp), (fromfd), (header), (offset), (count)))
187
188...
189</pre></div><div class="sect2" title="Possible VFS operation layers"><div class="titlepage"><div><div><h3 class="title"><a name="id331145"></a>Possible VFS operation layers</h3></div></div></div><p>
190These values are used by the VFS subsystem when building the conn-&gt;vfs
191and conn-&gt;vfs_opaque structs for a connection with multiple VFS modules.
192Internally, Samba differentiates only opaque and transparent layers at this process.
193Other types are used for providing better diagnosing facilities.
194</p><p>
195Most modules will provide transparent layers. Opaque layer is for modules
196which implement actual file system calls (like DB-based VFS). For example,
197default POSIX VFS which is built in into Samba is an opaque VFS module.
198</p><p>
199Other layer types (logger, splitter, scanner) were designed to provide different
200degree of transparency and for diagnosing VFS module behaviour.
201</p><p>
202Each module can implement several layers at the same time provided that only
203one layer is used per each operation.
204</p><pre class="programlisting">
205typedef enum _vfs_op_layer {
206 SMB_VFS_LAYER_NOOP = -1, /* - For using in VFS module to indicate end of array */
207 /* of operations description */
208 SMB_VFS_LAYER_OPAQUE = 0, /* - Final level, does not call anything beyond itself */
209 SMB_VFS_LAYER_TRANSPARENT, /* - Normal operation, calls underlying layer after */
210 /* possibly changing passed data */
211 SMB_VFS_LAYER_LOGGER, /* - Logs data, calls underlying layer, logging may not */
212 /* use Samba VFS */
213 SMB_VFS_LAYER_SPLITTER, /* - Splits operation, calls underlying layer _and_ own facility, */
214 /* then combines result */
215 SMB_VFS_LAYER_SCANNER /* - Checks data and possibly initiates additional */
216 /* file activity like logging to files _inside_ samba VFS */
217} vfs_op_layer;
218</pre></div></div><div class="sect1" title="The Interaction between the Samba VFS subsystem and the modules"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id331195"></a>The Interaction between the Samba VFS subsystem and the modules</h2></div></div></div><div class="sect2" title="Initialization and registration"><div class="titlepage"><div><div><h3 class="title"><a name="id331201"></a>Initialization and registration</h3></div></div></div><p>
219As each Samba module a VFS module should have a
220</p><pre class="programlisting">NTSTATUS vfs_example_init(void);</pre><p> function if it's staticly linked to samba or
221</p><pre class="programlisting">NTSTATUS init_module(void);</pre><p> function if it's a shared module.
222</p><p>
223This should be the only non static function inside the module.
224Global variables should also be static!
225</p><p>
226The module should register its functions via the
227</p><pre class="programlisting">
228NTSTATUS smb_register_vfs(int version, const char *name, vfs_op_tuple *vfs_op_tuples);
229</pre><p> function.
230</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
231<code class="literal">vfs objects</code> parameter to use this module.</p></dd><dt><span class="term">vfs_op_tuples</span></dt><dd><p>
232this is an array of vfs_op_tuple's.
233(vfs_op_tuples is descripted in details below.)
234</p></dd></dl></div><p>
235For each operation the module wants to provide it has a entry in the
236vfs_op_tuple array.
237</p><pre class="programlisting">
238typedef struct _vfs_op_tuple {
239 void* op;
240 vfs_op_type type;
241 vfs_op_layer layer;
242} vfs_op_tuple;
243</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">
244static vfs_op_tuple example_op_tuples[] = {
245 {SMB_VFS_OP(example_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
246 {SMB_VFS_OP(example_disconnect), SMB_VFS_OP_DISCONNECT, SMB_VFS_LAYER_TRANSPARENT},
247
248 {SMB_VFS_OP(example_rename), SMB_VFS_OP_RENAME, SMB_VFS_LAYER_OPAQUE},
249
250 /* This indicates the end of the array */
251 {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
252};
253
254NTSTATUS init_module(void)
255{
256 return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, "example", example_op_tuples);
257}
258</pre></div><div class="sect2" title="How the Modules handle per connection data"><div class="titlepage"><div><div><h3 class="title"><a name="id331328"></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.
259</p><pre class="programlisting">
260typedef struct vfs_handle_struct {
261 struct vfs_handle_struct *next, *prev;
262 const char *param;
263 struct vfs_ops vfs_next;
264 struct connection_struct *conn;
265 void *data;
266 void (*free_data)(void **data);
267} vfs_handle_struct;
268</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.
269Use the SMB_VFS_NEXT_* macros to call a next module operations and
270don'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.
271You can alloc data with connection life time on the handle-&gt;conn-&gt;mem_ctx TALLOC_CTX.
272But 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.
273If you talloc your private data on the TALLOC_CTX handle-&gt;conn-&gt;mem_ctx,
274you can set this function pointer to NULL.</p></dd></dl></div><p>Some useful MACROS for handle private data.
275</p><pre class="programlisting">
276#define SMB_VFS_HANDLE_GET_DATA(handle, datap, type, ret) { \
277 if (!(handle)||((datap=(type *)(handle)-&gt;data)==NULL)) { \
278 DEBUG(0,("%s() failed to get vfs_handle-&gt;data!\n",FUNCTION_MACRO)); \
279 ret; \
280 } \
281}
282
283#define SMB_VFS_HANDLE_SET_DATA(handle, datap, free_fn, type, ret) { \
284 if (!(handle)) { \
285 DEBUG(0,("%s() failed to set handle-&gt;data!\n",FUNCTION_MACRO)); \
286 ret; \
287 } else { \
288 if ((handle)-&gt;free_data) { \
289 (handle)-&gt;free_data(&amp;(handle)-&gt;data); \
290 } \
291 (handle)-&gt;data = (void *)datap; \
292 (handle)-&gt;free_data = free_fn; \
293 } \
294}
295
296#define SMB_VFS_HANDLE_FREE_DATA(handle) { \
297 if ((handle) &amp;&amp; (handle)-&gt;free_data) { \
298 (handle)-&gt;free_data(&amp;(handle)-&gt;data); \
299 } \
300}
301</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.
302</p><pre class="programlisting">
303...
304/* File operations */
305#define SMB_VFS_OPAQUE_OPEN(conn, fname, flags, mode) \
306 ((conn)-&gt;vfs_opaque.ops.open(\
307 (conn)-&gt;vfs_opaque.handles.open,\
308 (conn), (fname), (flags), (mode)))
309#define SMB_VFS_OPAQUE_CLOSE(fsp, fd) \
310 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.close(\
311 (fsp)-&gt;conn-&gt;vfs_opaque.handles.close,\
312 (fsp), (fd)))
313#define SMB_VFS_OPAQUE_READ(fsp, fd, data, n) \
314 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.read(\
315 (fsp)-&gt;conn-&gt;vfs_opaque.handles.read,\
316 (fsp), (fd), (data), (n)))
317#define SMB_VFS_OPAQUE_WRITE(fsp, fd, data, n) \
318 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.write(\
319 (fsp)-&gt;conn-&gt;vfs_opaque.handles.write,\
320 (fsp), (fd), (data), (n)))
321#define SMB_VFS_OPAQUE_LSEEK(fsp, fd, offset, whence) \
322 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.lseek(\
323 (fsp)-&gt;conn-&gt;vfs_opaque.handles.lseek,\
324 (fsp), (fd), (offset), (whence)))
325#define SMB_VFS_OPAQUE_SENDFILE(tofd, fsp, fromfd, header, offset, count) \
326 ((fsp)-&gt;conn-&gt;vfs_opaque.ops.sendfile(\
327 (fsp)-&gt;conn-&gt;vfs_opaque.handles.sendfile,\
328 (tofd), (fsp), (fromfd), (header), (offset), (count)))
329...
330</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.
331</p><pre class="programlisting">
332...
333/* File operations */
334#define SMB_VFS_NEXT_OPEN(handle, conn, fname, flags, mode) \
335 ((handle)-&gt;vfs_next.ops.open(\
336 (handle)-&gt;vfs_next.handles.open,\
337 (conn), (fname), (flags), (mode)))
338#define SMB_VFS_NEXT_CLOSE(handle, fsp, fd) \
339 ((handle)-&gt;vfs_next.ops.close(\
340 (handle)-&gt;vfs_next.handles.close,\
341 (fsp), (fd)))
342#define SMB_VFS_NEXT_READ(handle, fsp, fd, data, n) \
343 ((handle)-&gt;vfs_next.ops.read(\
344 (handle)-&gt;vfs_next.handles.read,\
345 (fsp), (fd), (data), (n)))
346#define SMB_VFS_NEXT_WRITE(handle, fsp, fd, data, n) \
347 ((handle)-&gt;vfs_next.ops.write(\
348 (handle)-&gt;vfs_next.handles.write,\
349 (fsp), (fd), (data), (n)))
350#define SMB_VFS_NEXT_LSEEK(handle, fsp, fd, offset, whence) \
351 ((handle)-&gt;vfs_next.ops.lseek(\
352 (handle)-&gt;vfs_next.handles.lseek,\
353 (fsp), (fd), (offset), (whence)))
354#define SMB_VFS_NEXT_SENDFILE(handle, tofd, fsp, fromfd, header, offset, count) \
355 ((handle)-&gt;vfs_next.ops.sendfile(\
356 (handle)-&gt;vfs_next.handles.sendfile,\
357 (tofd), (fsp), (fromfd), (header), (offset), (count)))
358...
359</pre></div></div><div class="sect1" title="Upgrading to the New VFS Interface"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id331482"></a>Upgrading to the New VFS Interface</h2></div></div></div><div class="sect2" title="Upgrading from 2.2.* and 3.0alpha modules"><div class="titlepage"><div><div><h3 class="title"><a name="id331487"></a>Upgrading from 2.2.* and 3.0alpha modules</h3></div></div></div><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem"><p>
360Add "vfs_handle_struct *handle, " as first parameter to all vfs operation functions.
361e.g. example_connect(connection_struct *conn, const char *service, const char *user);
362-&gt; example_connect(vfs_handle_struct *handle, connection_struct *conn, const char *service, const char *user);
363</p></li><li class="listitem"><p>
364Replace "default_vfs_ops." with "smb_vfs_next_".
365e.g. default_vfs_ops.connect(conn, service, user);
366-&gt; smb_vfs_next_connect(conn, service, user);
367</p></li><li class="listitem"><p>
368Uppercase all "smb_vfs_next_*" functions.
369e.g. smb_vfs_next_connect(conn, service, user);
370-&gt; SMB_VFS_NEXT_CONNECT(conn, service, user);
371</p></li><li class="listitem"><p>
372Add "handle, " as first parameter to all SMB_VFS_NEXT_*() calls.
373e.g. SMB_VFS_NEXT_CONNECT(conn, service, user);
374-&gt; SMB_VFS_NEXT_CONNECT(handle, conn, service, user);
375</p></li><li class="listitem"><p>
376(Only for 2.2.* modules)
377Convert the old struct vfs_ops example_ops to
378a vfs_op_tuple example_op_tuples[] array.
379e.g.
380</p><pre class="programlisting">
381struct vfs_ops example_ops = {
382 /* Disk operations */
383 example_connect, /* connect */
384 example_disconnect, /* disconnect */
385 NULL, /* disk free *
386 /* Directory operations */
387 NULL, /* opendir */
388 NULL, /* readdir */
389 NULL, /* mkdir */
390 NULL, /* rmdir */
391 NULL, /* closedir */
392 /* File operations */
393 NULL, /* open */
394 NULL, /* close */
395 NULL, /* read */
396 NULL, /* write */
397 NULL, /* lseek */
398 NULL, /* sendfile */
399 NULL, /* rename */
400 NULL, /* fsync */
401 example_stat, /* stat */
402 example_fstat, /* fstat */
403 example_lstat, /* lstat */
404 NULL, /* unlink */
405 NULL, /* chmod */
406 NULL, /* fchmod */
407 NULL, /* chown */
408 NULL, /* fchown */
409 NULL, /* chdir */
410 NULL, /* getwd */
411 NULL, /* utime */
412 NULL, /* ftruncate */
413 NULL, /* lock */
414 NULL, /* symlink */
415 NULL, /* readlink */
416 NULL, /* link */
417 NULL, /* mknod */
418 NULL, /* realpath */
419 NULL, /* fget_nt_acl */
420 NULL, /* get_nt_acl */
421 NULL, /* fset_nt_acl */
422 NULL, /* set_nt_acl */
423
424 NULL, /* chmod_acl */
425 NULL, /* fchmod_acl */
426
427 NULL, /* sys_acl_get_entry */
428 NULL, /* sys_acl_get_tag_type */
429 NULL, /* sys_acl_get_permset */
430 NULL, /* sys_acl_get_qualifier */
431 NULL, /* sys_acl_get_file */
432 NULL, /* sys_acl_get_fd */
433 NULL, /* sys_acl_clear_perms */
434 NULL, /* sys_acl_add_perm */
435 NULL, /* sys_acl_to_text */
436 NULL, /* sys_acl_init */
437 NULL, /* sys_acl_create_entry */
438 NULL, /* sys_acl_set_tag_type */
439 NULL, /* sys_acl_set_qualifier */
440 NULL, /* sys_acl_set_permset */
441 NULL, /* sys_acl_valid */
442 NULL, /* sys_acl_set_file */
443 NULL, /* sys_acl_set_fd */
444 NULL, /* sys_acl_delete_def_file */
445 NULL, /* sys_acl_get_perm */
446 NULL, /* sys_acl_free_text */
447 NULL, /* sys_acl_free_acl */
448 NULL /* sys_acl_free_qualifier */
449};
450</pre><p>
451-&gt;
452</p><pre class="programlisting">
453static vfs_op_tuple example_op_tuples[] = {
454 {SMB_VFS_OP(example_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
455 {SMB_VFS_OP(example_disconnect), SMB_VFS_OP_DISCONNECT, SMB_VFS_LAYER_TRANSPARENT},
456
457 {SMB_VFS_OP(example_fstat), SMB_VFS_OP_FSTAT, SMB_VFS_LAYER_TRANSPARENT},
458 {SMB_VFS_OP(example_stat), SMB_VFS_OP_STAT, SMB_VFS_LAYER_TRANSPARENT},
459 {SMB_VFS_OP(example_lstat), SMB_VFS_OP_LSTAT, SMB_VFS_LAYER_TRANSPARENT},
460
461 {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
462};
463</pre><p>
464</p></li><li class="listitem"><p>
465Move the example_op_tuples[] array to the end of the file.
466</p></li><li class="listitem"><p>
467Add the init_module() function at the end of the file.
468e.g.
469</p><pre class="programlisting">
470NTSTATUS init_module(void)
471{
472 return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,"example",example_op_tuples);
473}
474</pre><p>
475</p></li><li class="listitem"><p>
476Check if your vfs_init() function does more then just prepare the vfs_ops structs or
477remember the struct smb_vfs_handle_struct.
478</p><table border="0" summary="Simple list" class="simplelist"><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().
479 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>
480</p></li><li class="listitem"><p>
481(Only for 3.0alpha* modules)
482Check if your vfs_done() function contains needed code.
483</p><table border="0" summary="Simple list" class="simplelist"><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().
484</td></tr></table><p>
485</p></li><li class="listitem"><p>
486Check if you have any global variables left.
487Decide if it wouldn't be better to have this data on a connection basis.
488</p><table border="0" summary="Simple list" class="simplelist"><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>
489
490 e.g. if you have such a struct:
491</p><pre class="programlisting">
492struct example_privates {
493 char *some_string;
494 int db_connection;
495};
496</pre><p>
497first way of doing it:
498</p><pre class="programlisting">
499static int example_connect(vfs_handle_struct *handle,
500 connection_struct *conn, const char *service,
501 const char* user)
502{
503 struct example_privates *data = NULL;
504
505 /* alloc our private data */
506 data = (struct example_privates *)talloc_zero(conn-&gt;mem_ctx, sizeof(struct example_privates));
507 if (!data) {
508 DEBUG(0,("talloc_zero() failed\n"));
509 return -1;
510 }
511
512 /* init out private data */
513 data-&gt;some_string = talloc_strdup(conn-&gt;mem_ctx,"test");
514 if (!data-&gt;some_string) {
515 DEBUG(0,("talloc_strdup() failed\n"));
516 return -1;
517 }
518
519 data-&gt;db_connection = open_db_conn();
520
521 /* and now store the private data pointer in handle-&gt;data
522 * we don't need to specify a free_function here because
523 * we use the connection TALLOC context.
524 * (return -1 if something failed.)
525 */
526 VFS_HANDLE_SET_DATA(handle, data, NULL, struct example_privates, return -1);
527
528 return SMB_VFS_NEXT_CONNECT(handle,conn,service,user);
529}
530
531static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
532{
533 struct example_privates *data = NULL;
534
535 /* get the pointer to our private data
536 * return -1 if something failed
537 */
538 SMB_VFS_HANDLE_GET_DATA(handle, data, struct example_privates, return -1);
539
540 /* do something here...*/
541 DEBUG(0,("some_string: %s\n",data-&gt;some_string));
542
543 return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
544}
545</pre><p>
546second way of doing it:
547</p><pre class="programlisting">
548static void free_example_privates(void **datap)
549{
550 struct example_privates *data = (struct example_privates *)*datap;
551
552 SAFE_FREE(data-&gt;some_string);
553 SAFE_FREE(data);
554
555 *datap = NULL;
556
557 return;
558}
559
560static int example_connect(vfs_handle_struct *handle,
561 connection_struct *conn, const char *service,
562 const char* user)
563{
564 struct example_privates *data = NULL;
565
566 /* alloc our private data */
567 data = (struct example_privates *)malloc(sizeof(struct example_privates));
568 if (!data) {
569 DEBUG(0,("malloc() failed\n"));
570 return -1;
571 }
572
573 /* init out private data */
574 data-&gt;some_string = strdup("test");
575 if (!data-&gt;some_string) {
576 DEBUG(0,("strdup() failed\n"));
577 return -1;
578 }
579
580 data-&gt;db_connection = open_db_conn();
581
582 /* and now store the private data pointer in handle-&gt;data
583 * we need to specify a free_function because we used malloc() and strdup().
584 * (return -1 if something failed.)
585 */
586 SMB_VFS_HANDLE_SET_DATA(handle, data, free_example_privates, struct example_privates, return -1);
587
588 return SMB_VFS_NEXT_CONNECT(handle,conn,service,user);
589}
590
591static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
592{
593 struct example_privates *data = NULL;
594
595 /* get the pointer to our private data
596 * return -1 if something failed
597 */
598 SMB_VFS_HANDLE_GET_DATA(handle, data, struct example_privates, return -1);
599
600 /* do something here...*/
601 DEBUG(0,("some_string: %s\n",data-&gt;some_string));
602
603 return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
604}
605</pre><p>
606</p></li><li class="listitem"><p>
607To make it easy to build 3rd party modules it would be useful to provide
608configure.in, (configure), install.sh and Makefile.in with the module.
609(Take a look at the example in <code class="filename">examples/VFS</code>.)
610</p><p>
611The configure script accepts <code class="option">--with-samba-source</code> to specify
612the path to the samba source tree.
613It also accept <code class="option">--enable-developer</code> which lets the compiler
614give you more warnings.
615</p><p>
616The idea is that you can extend this
617<code class="filename">configure.in</code> and <code class="filename">Makefile.in</code> scripts
618for your module.
619</p></li><li class="listitem"><p>
620Compiling &amp; Testing...
621</p><table border="0" summary="Simple list" class="simplelist"><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>
622</p></li></ol></div></div></div><div class="sect1" title="Some Notes"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id331788"></a>Some Notes</h2></div></div></div><div class="sect2" title="Implement TRANSPARENT functions"><div class="titlepage"><div><div><h3 class="title"><a name="id331793"></a>Implement TRANSPARENT functions</h3></div></div></div><p>
623Avoid writing functions like this:
624
625</p><pre class="programlisting">
626static int example_close(vfs_handle_struct *handle, files_struct *fsp, int fd)
627{
628 return SMB_VFS_NEXT_CLOSE(handle, fsp, fd);
629}
630</pre><p>
631
632Overload only the functions you really need to!
633</p></div><div class="sect2" title="Implement OPAQUE functions"><div class="titlepage"><div><div><h3 class="title"><a name="id331809"></a>Implement OPAQUE functions</h3></div></div></div><p>
634If you want to just implement a better version of a
635default samba opaque function
636(e.g. like a disk_free() function for a special filesystem)
637it's ok to just overload that specific function.
638</p><p>
639If you want to implement a database filesystem or
640something different from a posix filesystem.
641Make sure that you overload every vfs operation!!!
642</p><p>
643Functions your FS does not support should be overloaded by something like this:
644e.g. for a readonly filesystem.
645</p><pre class="programlisting">
646static int example_rename(vfs_handle_struct *handle, connection_struct *conn,
647 char *oldname, char *newname)
648{
649 DEBUG(10,("function rename() not allowed on vfs 'example'\n"));
650 errno = ENOSYS;
651 return -1;
652}
653</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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