chore(pkg/wireguard): remove duplicate link syncing, and cleanup

Fixes: #166

Author: uhthomas

pkg/wireguard/wireguard.go

@@ -1,6 +1,7 @@
 package wireguard
 
 import (
+	"errors"
 	"fmt"
 	"net"
 	"os/exec"
@@ -88,7 +89,7 @@ func createLinkUsingUserspaceImpl(iface string, wgUserspaceImplementationFallbac
 
 }
 
-func createLinkUsingKernalModule(iface string) error {
+func createLinkUsingKernelModule(iface string) error {
 	// link not created
 	wgLink := &netlink.GenericLink{
 		LinkAttrs: netlink.LinkAttrs{
@@ -104,49 +105,25 @@ func createLinkUsingKernalModule(iface string) error {
 	return nil
 }
 
-func SyncLink(_ agent.State, iface string, wgUserspaceImplementationFallback string, wgUseUserspaceImpl bool) error {
-	_, err := netlink.LinkByName(iface)
+func SyncLink(state agent.State, iface string, wgUserspaceImplementationFallback string, wgUseUserspaceImpl bool) error {
+	link, err := netlink.LinkByName(iface)
 	if err != nil {
-		if _, ok := err.(netlink.LinkNotFoundError); !ok {
-			return err
-		}
-	}
+		if errors.As(err, &netlink.LinkNotFoundError{}) {
+			if wgUseUserspaceImpl {
+				if err := createLinkUsingUserspaceImpl(iface, wgUserspaceImplementationFallback); err != nil {
+					return fmt.Errorf("create link using user space impl: %w", err)
+				}
 
-	if _, ok := err.(netlink.LinkNotFoundError); ok {
-		if wgUseUserspaceImpl {
-			err = createLinkUsingUserspaceImpl(iface, wgUserspaceImplementationFallback)
+			} else if err := createLinkUsingKernelModule(iface); err != nil {
+				fmt.Printf("could not create link using kernel module, will attempt to fallback to user space implementation: %v\n", err)
 
-			if err != nil {
-				return err
+				// Fallback to user space implementation.
+				wgUseUserspaceImpl = true
 			}
 
-		} else {
-			err = createLinkUsingKernalModule(iface)
-
-			if err != nil {
-				err = createLinkUsingUserspaceImpl(iface, wgUserspaceImplementationFallback)
-
-				if err != nil {
-					return err
-				}
-			}
-		}
-
-		// TODO: Can this be removed?
-		link, err := netlink.LinkByName(iface)
-		if err != nil {
-			return err
-		}
-		if err := netlink.LinkSetUp(link); err != nil {
-			return err
-		}
-	}
-
-	link, err := netlink.LinkByName(iface)
-	if err != nil {
-		if _, ok := err.(netlink.LinkNotFoundError); !ok {
-			return err
+			return SyncLink(state, iface, wgUserspaceImplementationFallback, wgUseUserspaceImpl)
 		}
+		return fmt.Errorf("link by name: %w", err)
 	}
 
 	addresses, err := netlink.AddrList(link, syscall.AF_INET)
@@ -165,7 +142,7 @@ func SyncLink(_ agent.State, iface string, wgUserspaceImplementationFallback str
 	}
 
 	if err := netlink.LinkSetUp(link); err != nil {
-		return err
+		return fmt.Errorf("link set up: %w", err)
 	}
 	return nil
 }