11 This section shows how a VPP developer can create a new plugin, and
12 add it to VPP. We assume that we are starting from the VPP <top-of-workspace>.
14 As an example, we will use the **make-plugin.sh** tool found in
15 **./extras/emacs**. make-plugin.sh is a simple wrapper for a comprehensive
16 plugin generator constructed from a set of emacs-lisp skeletons.
18 Create your new plugin
19 ----------------------
21 Change directory to **./src/plugins**, and run the plugin generator:
23 .. code-block:: console
26 $ ../../extras/emacs/make-plugin.sh
28 Loading /scratch/vpp-docs/extras/emacs/tunnel-c-skel.el (source)...
29 Loading /scratch/vpp-docs/extras/emacs/tunnel-decap-skel.el (source)...
30 Loading /scratch/vpp-docs/extras/emacs/tunnel-encap-skel.el (source)...
31 Loading /scratch/vpp-docs/extras/emacs/tunnel-h-skel.el (source)...
32 Loading /scratch/vpp-docs/extras/emacs/elog-4-int-skel.el (source)...
33 Loading /scratch/vpp-docs/extras/emacs/elog-4-int-track-skel.el (source)...
34 Loading /scratch/vpp-docs/extras/emacs/elog-enum-skel.el (source)...
35 Loading /scratch/vpp-docs/extras/emacs/elog-one-datum-skel.el (source)...
37 Dispatch type [dual or qs]: dual
38 (Shell command succeeded with no output)
42 The plugin generator script asks two questions: the name of the
43 plugin, and which of two dispatch types to use. Since the plugin name
44 finds its way into quite a number of places - filenames, typedef
45 names, graph arc names - it pays to think for a moment.
47 The dispatch type refers to the coding pattern used to construct
48 **node.c**, the *pro forma* data-plane node. The **dual** option
49 constructs a dual-single loop pair with speculative enqueueing. This
50 is the traditional coding pattern for load-store intensive graph
53 The **qs** option generates a quad-single loop pair which uses
54 vlib_get_buffers(...) and vlib_buffer_enqueue_to_next(...). These
55 operators make excellent use of available SIMD vector unit
56 operations. It's very simple to change a quad-single loop-pair to a
57 dual-single loop pair if you decide to do so later.
62 Here are the generated files. We'll go through them in a moment.
64 .. code-block:: console
68 CMakeLists.txt myplugin.api myplugin.c myplugin.h
69 myplugin_periodic.c myplugin_test.c node.c setup.pg
71 Due to recent build system improvements, you **don't** need to touch
72 any other files to integrate your new plugin into the vpp build. Simply
73 rebuild your workspace from scratch, and the new plugin will appear.
75 Rebuild your workspace
76 ----------------------
78 This is the straightforward way to reconfigure and rebuild your workspace:
80 .. code-block:: console
82 $ cd <top-of-workspace>
83 $ make rebuild [or rebuild-release]
85 Thanks to ccache, this operation doesn't take an annoying amount of time.
90 As a quick sanity check, run vpp and make sure that
91 "myplugin_plugin.so" and "myplugin_test_plugin.so" are loaded:
93 .. code-block:: console
95 $ cd <top-of-workspace>
98 load_one_plugin:189: Loaded plugin: myplugin_plugin.so (myplugin description goes here)
100 load_one_vat_plugin:67: Loaded plugin: myplugin_test_plugin.so
104 If this simple test fails, please seek assistance.
106 Generated Files in Detail
107 _________________________
109 This section discusses the generated files in some detail. It's fine to
110 skim this section, and return later for more detail.
115 This is the build system recipe for building your plugin. Please fix
116 the copyright notice:
118 .. code-block:: console
120 # Copyright (c) <current-year> <your-organization>
122 The rest of the build recipe is pretty simple:
124 .. code-block:: CMake
126 add_vpp_plugin (myplugin
143 As you can see, the build recipe consists of several lists of
144 files. **SOURCES** is a list of C source files. **API_FILES** is a
145 list of the plugin's binary API definition files [one such file is
146 usually plenty], and so forth.
148 **MULTIARCH_SOURCES** lists data plane graph node dispatch function
149 source files considered to be performance-critical. Specific functions
150 in these files are compiled multiple times, so that they can leverage
151 CPU-specific features. More on this in a moment.
153 If you add source files, simply add them to the indicated list(s).
158 This is the primary #include file for the new plugin. Among other
159 things, it defines the plugin's *main_t* data structure. This is the
160 right place to add problem-specific data structures. Please **resist
161 the temptation** to create a set of static or [worse yet] global
162 variables in your plugin. Refereeing name-collisions between plugins
163 is not anyone's idea of a good time.
168 For want of a better way to describe it, myplugin.c is the vpp plugin
169 equivalent of "main.c". Its job is to hook the plugin into the vpp
170 binary API message dispatcher, and to add its messages to vpp's global
171 "message-name_crc" hash table. See "myplugin_init (...")"
173 Vpp itself uses dlsym(...) to track down the vlib_plugin_registration_t
174 generated by the VLIB_PLUGIN_REGISTER macro:
178 VLIB_PLUGIN_REGISTER () =
180 .version = VPP_BUILD_VER,
181 .description = "myplugin plugin description goes here",
184 Vpp only loads .so files from the plugin directory which contain an
185 instance of this data structure.
187 You can enable or disable specific vpp plugins from the command
188 line. By default, plugins are loaded. To change that behavior, set
189 default_disabled in the macro VLIB_PLUGIN_REGISTER:
193 VLIB_PLUGIN_REGISTER () =
195 .version = VPP_BUILD_VER,
196 .default_disabled = 1
197 .description = "myplugin plugin description goes here",
200 The boilerplate generator places the graph node dispatch function
201 onto the "device-input" feature arc. This may or may not be useful.
205 VNET_FEATURE_INIT (myplugin, static) =
207 .arc_name = "device-input",
208 .node_name = "myplugin",
209 .runs_before = VNET_FEATURES ("ethernet-input"),
212 As given by the plugin generator, myplugin.c contains the binary API
213 message handler for a generic "please enable my feature on such and
214 such an interface" binary API message. As you'll see, setting up the
215 vpp message API tables is simple. Big fat warning: the scheme is
216 intolerant of minor mistakes. Example: forgetting to add
217 mainp->msg_id_base can lead to very confusing failures.
219 If you stick to modifying the generated boilerplate with care -
220 instead of trying to build code from first principles - you'll save
221 yourself a bunch of time and aggravation
226 This file contains binary API message **generation** code, which is
227 compiled into a separate .so file. The "vpp_api_test" program loads
228 these plugins, yielding immediate access to your plugin APIs for
229 external client binary API testing.
231 vpp itself loads test plugins, and makes the code available via the
232 "binary-api" debug CLI. This is a favorite way to unit-test binary
233 APIs prior to integration testing.
238 This is the generated graph node dispatch function. You'll need to
239 rewrite it to solve the problem at hand. It will save considerable
240 time and aggravation to retain the **structure** of the node dispatch
243 Even for an expert, it's a waste of time to reinvent the *loop
244 structure*, enqueue patterns, and so forth. Simply tear out and
245 replace the specimen 1x, 2x, 4x packet processing code with code
246 relevant to the problem you're trying to solve.
251 This contains the API message definition. Here we only have defined
252 a single one named ``myplugin_enable_disable`` and an implicit
253 ``myplugin_enable_disable_reply`` containing only a return value due
254 to the ``autoreply`` keyword.
256 The syntax reference for ``.api`` files can be found at VPP API Language
258 Addressing the binary API with this message will run the handler defined
259 in ``myplugin.c`` as ``vl_api_myplugin_enable_disable_t_handler``.
260 It will receive a message pointer ``*mp`` which is the struct defined
261 in ``myplugin.api`` and should return another message pointer ``*rmp``,
262 of the reply type. That's what ``REPLY_MACRO`` does.
264 To be noted, all API messages are in net-endian and vpp is host-endian,
265 so you will need to use :
267 * ``u32 value = ntohl(mp->value);``
268 * ``rmp->value = htonl(value);``
270 You can now use this API with :ref:`GoLang bindings <add_plugin_goapi>`
275 This defines a VPP process, a routine that will run indefinitely and
276 be woken up intermittently, here to process plugin events.
278 To be noted, vlib_processes aren't thread-safe, and data structures
279 should be locked when shared between workers.
281 Plugin "Friends with Benefits"
282 ------------------------------
284 In vpp VLIB_INIT_FUNCTION functions, It's reasonably common to see a
285 specific init function invoke other init functions:
289 if ((error = vlib_call_init_function (vm, some_other_init_function))
292 In the case where one plugin needs to call a init function in another
293 plugin, use the vlib_call_plugin_init_function macro:
297 if ((error = vlib_call_plugin_init_function (vm, "otherpluginname", some_init_function))
300 This allows sequencing between plugin init functions.
302 If you wish to obtain a pointer to a symbol in another plugin, use the
303 vlib_plugin_get_symbol(...) API:
307 void *p = vlib_get_plugin_symbol ("plugin_name", "symbol");
312 For more information you can read many example plugins in the directory "./src/plugins".