docs: Improve new plugin doc & add govpp API doc

[vpp.git] / docs / gettingstarted / developers / add_plugin_goapi.rst

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+.. _add_plugin_goapi:
+
+Add a plugin's GO API
+=====================
+
+In order to use your plugin's API with GO, you will need to use
+a GO client and GO definitions of the API messages that you defined
+in ``myplugin.api`` (go bindings).
+
+These two things can be found in `govpp <https://github.com/FDio/govpp>`_
+
+* The API client lives in `./core`
+* The api-generator lives in `./binapigen`
+* A sample of its output (the go bindings) for VPP's latest version lives in `./binapi`
+
+To generate the go bindings for your plugin. Assuming :
+* ``/home/vpp`` is a VPP clone with your plugin in it.
+* ``/home/controlplane`` is a go controlplane repo
+
+.. code-block:: console
+
+    $ mkdir /home/controlplane/vpp-go-bindings
+    $ git clone https://github.com/FDio/govpp>
+    $ cd govpp
+    $ BINAPI_DIR=/home/controlplane/vpp-go-bindings VPP_DIR=/home/vpp make gen-binapi-from-code
+
+This will generate the go-bindings in ``/home/controlplane/vpp-go-bindings``
+For example ``vpp-go-bindings/myplugin/myplugin.ba.go`` will contain :
+
+.. code-block:: go
+
+    // MypluginEnableDisable defines message 'myplugin_enable_disable'.
+    type MypluginEnableDisable struct {
+           EnableDisable bool                           `binapi:"bool,name=enable_disable" json:"enable_disable,omitempty"`
+           SwIfIndex     interface_types.InterfaceIndex `binapi:"interface_index,name=sw_if_index" json:"sw_if_index,omitempty"`
+    }
+
+
+You can then use the generated go bindings in your go code like this :
+
+.. code-block:: go
+
+    package main
+
+    import (
+           "fmt"
+           "git.fd.io/govpp.git"
+           "git.fd.io/govpp.git/binapi/interfaces"
+           "git.fd.io/govpp.git/binapi/vpe"
+
+           "myplugin.io/controlplane/vpp-go-bindings/myplugin/myplugin"
+    )
+
+    func main() {
+           // Connect to VPP
+           conn, _ := govpp.Connect("/run/vpp/api.sock")
+           defer conn.Disconnect()
+
+           // Open channel
+           ch, _ := conn.NewAPIChannel()
+           defer ch.Close()
+
+           request := &vpe.MypluginEnableDisable{
+               EnableDisable: true,
+           }
+           reply := &vpe.MypluginEnableDisableReply{}
+
+           err := ch.SendRequest(request).ReceiveReply(reply)
+           if err != nil {
+                   fmt.Errorf("SendRequest: %w\n", err)
+           }
+    }
+
+As you will need to import (or ``go get "git.fd.io/govpp.git"``) to leverage the API
+client in your code, you might want to use the api-generator directly from the
+clone ``go build`` fetches for you. You can do this with :
+
+.. code-block:: console
+
+  $ export GOVPP_DIR=$(go list -f '{{.Dir}}' -m git.fd.io/govpp.git)
+  $ cd $GOVPP_DIR && go build -o /some/bin/dir ./cmd/binapi-generator
+  $ # instead of make gen-binapi-from-code you can rewrite the code to target
+  $ # your version ./binapi-generator