chromium/third_party/ipcz/src/ipcz/link_type.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_LINK_TYPE_H_
#define IPCZ_SRC_IPCZ_LINK_TYPE_H_

#include <string>

namespace ipcz {

// Enumeration indicating what role a specific RouterLink plays along its route.
// Every end-to-end route has exactly one "central" link -- the link that
// connects one side of the route to the other -- along with any number of
// "peripheral" links extending the route away from the central link on one side
// or the other.
//
// If a peripheral link connects a router R1 to another router R2 which is
// closer to the central link, the link is considered to be "outward" from R1
// and "inward" from R2. Conversely if a peripheral link connects a router R1 to
// another router R2 which is *further* from the central link, the link is
// considered to be inward R1 and outward from R2.
//
// Finally, when two routes are joined via the MergePortals API, the merged
// portals' routers are linked together via a bridge link.
//
// The stable state of any given route is to have exactly two routers, both
// terminal, with a single central link between them. Routes which are extended
// by portal relocation or bridged via portal merges may grow into arbitrarily
// long chains of linked routers, but over time all interior routers are
// incrementally bypassed and discarded through a process of link decay and
// replacement.
//
// The different link classifications defined here help with the orchestration
// of this incremental reduction process.
struct LinkType { … };

}  // namespace ipcz

#endif  // IPCZ_SRC_IPCZ_LINK_TYPE_H_