C library wrapper (#71)

* feat: Created the go C Wrapper files
* Made changes to README instructions.

---------

Signed-off-by: phansGithub <[email protected]>

go.mod

@@ -8,6 +8,7 @@ require (
 	github.com/go-ozzo/ozzo-validation/v4 v4.3.0
 	github.com/google/gofuzz v1.1.0
 	github.com/google/uuid v1.3.0
+	github.com/intel/afxdp-plugins-for-kubernetes/pkg/goclient v0.0.0
 	github.com/intel/afxdp-plugins-for-kubernetes/pkg/subfunctions v0.0.0
 	github.com/pkg/errors v0.9.1
 	github.com/safchain/ethtool v0.0.0-20210803160452-9aa261dae9b1
@@ -22,3 +23,4 @@ require (
 )
 
 replace github.com/intel/afxdp-plugins-for-kubernetes/pkg/subfunctions => ./pkg/subfunctions
+replace github.com/intel/afxdp-plugins-for-kubernetes/pkg/goclient => ./pkg/goclient

pkg/cclient/README.md

@@ -0,0 +1,46 @@
+# Compiling the C Library
+
+## Creating the shared library and header files:
+
+```cmd
+go build -o lib_udsclient.so -buildmode=c-shared cclient.go
+```
+- this creates the header and shared library files from the cclient.go file.
+
+## Creating the the static library and header files:
+
+```cmd
+go build -o lib_udsclient.a -buildmode=c-archive ./cclient.go
+```
+- this creates the shared library and header files
+
+## Usage
+
+After creating the library and header files as described in the previous steps,
+this is how to use the functions generated by cgo
+
+```c
+char* GetUdsClientVersion()
+``` 
+This returns the version of the handshake on your local machine/client.
+
+```c
+char* GetUdsServerVersion()
+``` 
+This returns the version of the handshake on the server/host.
+
+```c
+int RequestXskMapFd(char* device)
+``` 
+This requests an xskmap Fd for a specified device.
+
+```c
+int RequestBusyPoll(int busyTimeout, int busyBudget, int fd)
+``` 
+This requests a busy poll for a specific device by using it's fd, and specifying a timeout and a budget.
+
+```c
+void CleanUpConnection()
+``` 
+After all the other functions are called, this needs to be called after all the work you need to do is done,
+so that the connection to the UDS can be cleaned up.

pkg/cclient/cclient.go

@@ -0,0 +1,94 @@
+package main
+
+import (
+	"C"
+	"fmt"
+	"os"
+
+	"github.com/intel/afxdp-plugins-for-kubernetes/internal/uds"
+	"github.com/intel/afxdp-plugins-for-kubernetes/pkg/goclient"
+)
+
+func main() {
+	// Needed for cgo to generate the .h
+}
+
+var cleaner uds.CleanupFunc
+
+/*
+GetClientVersion is an exported version for c of the goclient GetClientVersion()
+*/
+//export GetUdsClientVersion
+func GetUdsClientVersion() *C.char {
+	return C.CString(goclient.GetClientVersion())
+}
+
+/*
+ServerVersion is an exported version for c of the goclient GetServerVersion()
+*/
+//export GetUdsServerVersion
+func GetUdsServerVersion() *C.char {
+	response, function, err := goclient.GetServerVersion()
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err.Error())
+		function()
+		return C.CString("-1")
+	}
+
+	cleaner = function
+
+	return C.CString(response)
+}
+
+/*
+GetXskMapFd is an exported version for c of the goclient XskMapFd()
+*/
+//export RequestXskMapFd
+func RequestXskMapFd(device *C.char) (fd C.int) {
+	if device != nil {
+		fdVal, function, err := goclient.RequestXSKmapFD(C.GoString(device))
+		fd = C.int(fdVal)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err.Error())
+			function()
+			return -1
+		}
+
+		cleaner = function
+		return fd
+	}
+
+	return -1
+}
+
+/*
+RequestBusyPoll is an exported version for c of the goclient RequestBusyPoll()
+*/
+//export RequestBusyPoll
+func RequestBusyPoll(busyTimeout, busyBudget, fd C.int) C.int {
+	timeout, budget, fdInt := int(busyTimeout), int(busyBudget), int(fd)
+	if timeout > -1 && budget > -1 && fdInt > -1 {
+		function, err := goclient.RequestBusyPoll(timeout, budget, fdInt)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err.Error())
+			function()
+			return -1
+		}
+		cleaner = function
+		return 0
+	}
+	return -1
+}
+
+/*
+CleanUpConnection an explicit exported cgo function to cleanup a connection after calling any of the other functions.
+Pass in one of the available function names to clean up the connection after use.
+*/
+//export CleanUpConnection
+func CleanUpConnection() {
+	if cleaner == nil {
+		fmt.Println("No cleanup function available to call")
+	} else {
+		cleaner()
+	}
+}