type EventInfo struct {
	// Queue is the socket corresponding event queue.
	Wq *waiter.Queue

	// Mask represents events this socket registered.
	Mask waiter.EventMask

	// Ready represents events has been currently reported.
	Ready waiter.EventMask

	// Waiting represents whether there is any waiting event.
	Waiting bool
}

type InitStackArgs struct {
	// InitStr represents arguments needed to initialize plugin stack.
	InitStr string

	// FDs represents files opened during stack pre-init stage, which will
	// be used in stack initialization.
	FDs []int
}

type PluginNotifier interface {
	// AddFD registers a new socket fd and its corresponding
	// event notification info into the global fdMap.
	AddFD(fd uint32, eventinfo *EventInfo) error

	// RemoveFD unregisters a socket fd and its corresponding
	// event notification info from the global fdMap.
	RemoveFD(fd uint32)

	// UpdateFD updates the set of events the socket fd needs
	// to be notified on.
	UpdateFD(fd uint32) error
}

type PluginStack interface {
	inet.Stack

	// Init initializes plugin stack.
	Init(args *InitStackArgs) error

	// PreInit handles prepare steps before initializing plugin stack.
	// It may include joining namespace, mounting NIC, etc.
	PreInit(args *PreInitStackArgs) (string, []int, error)
}

type PreInitStackArgs struct {
	// Pid represents current process that invokes plugin stack
	// pre-init.
	Pid int
}