Fix docker build

client/internal/firewall.go

@@ -1,5 +1,3 @@
-//go:build !linux
-
 package internal
 
 import (
@@ -7,8 +5,15 @@ import (
 	"runtime"
 
 	"github.com/netbirdio/netbird/client/firewall"
+	"github.com/netbirdio/netbird/client/firewall/iptables"
 )
 
 func buildFirewallManager() (fw firewall.Manager, err error) {
-	return nil, fmt.Errorf("not implemented for this OS: %s", runtime.GOOS)
+	switch runtime.GOOS {
+	case "linux":
+		return iptables.Create()
+
+	default:
+		return nil, fmt.Errorf("not implemented for this OS: %s", runtime.GOOS)
+	}
 }