chromium/third_party/ipcz/src/ipcz/route_edge.h

// Copyright 2022 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef IPCZ_SRC_IPCZ_ROUTE_EDGE_H_
#define IPCZ_SRC_IPCZ_ROUTE_EDGE_H_

#include <optional>

#include "ipcz/router_link.h"
#include "ipcz/sequence_number.h"
#include "ipcz/sublink_id.h"
#include "third_party/abseil-cpp/absl/base/macros.h"
#include "util/ref_counted.h"

namespace ipcz {

class NodeLink;
class Router;
class RouterLink;

// A RouteEdge is responsible for message ingress and egress on one
// (inward-facing or outward-facing) side of a router. Every functioning router
// has one outward edge and (if proxying) one inward edge.
//
// Over the course of its lifetime a RouteEdge may utilize many different
// RouterLinks, but at any moment it has at most two: one "primary" link and one
// "decaying" link.
//
// The decaying link's usage is restricted to transmission and receipt of a
// limited range of parcels based on SequenceNumber, and once all expected
// parcels are sent and received, the link is dropped from the edge.
//
// When a RouteEdge has no decaying link, it may be able to transition its
// primary link to a decaying link, while adopting a new primary link to take
// its place. This process of incremental link replacement is the basis for ipcz
// route reduction.
//
// This object is not thread-safe.
class RouteEdge { … };

}  // namespace ipcz

#endif  // IPCZ_SRC_IPCZ_ROUTE_EDGE_H_