<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 V1.71.0"><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#id324691">The Samba (Posix) VFS layer</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id324696">The general interface</a></span></dt><dt><span class="sect2"><a href="vfs.html#id324766">Possible VFS operation layers</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id324811">The Interaction between the Samba VFS subsystem and the modules</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id324817">Initialization and registration</a></span></dt><dt><span class="sect2"><a href="vfs.html#id324954">How the Modules handle per connection data</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id325112">Upgrading to the New VFS Interface</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id325117">Upgrading from 2.2.* and 3.0aplha modules</a></span></dt></dl></dd><dt><span class="sect1"><a href="vfs.html#id325448">Some Notes</a></span></dt><dd><dl><dt><span class="sect2"><a href="vfs.html#id325454">Implement TRANSPARENT functions</a></span></dt><dt><span class="sect2"><a href="vfs.html#id325472">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="id324691"></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="id324696"></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="id324766"></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="id324811"></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="id324817"></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 <code class="literal">vfs objects</code> 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="id324954"></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 <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. 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="id325112"></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="id325117"></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="id325448"></a>Some Notes</h2></div></div></div><div class="sect2" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id325454"></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="id325472"></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. 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