Add net control funcs

common/control/interface.go

@@ -0,0 +1,21 @@
+package control
+
+import (
+	"syscall"
+)
+
+type Func = func(network, address string, conn syscall.RawConn) error
+
+func Append(oldFunc Func, newFunc Func) Func {
+	if oldFunc == nil {
+		return newFunc
+	} else if newFunc == nil {
+		return oldFunc
+	}
+	return func(network, address string, conn syscall.RawConn) error {
+		if err := oldFunc(network, address, conn); err != nil {
+			return err
+		}
+		return newFunc(network, address, conn)
+	}
+}