blob: a5c3aebabffc148a0d316e91d289bbb7678903ac [file] [log] [blame]
// Copyright 2022 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include <atomic>
#include "ipcz/fragment_ref.h"
#include "ipcz/link_side.h"
#include "ipcz/link_type.h"
#include "ipcz/router_link.h"
#include "ipcz/router_link_state.h"
#include "ipcz/sublink_id.h"
#include "util/ref_counted.h"
namespace ipcz {
class NodeLink;
// One side of a link between two Routers living on different nodes. A
// RemoteRouterLink uses a NodeLink plus a SublinkId as its transport between
// the routers. On the other end (on another node) is another RemoteRouterLink
// using a NodeLink back to this node, with the same SublinkId.
// As with other RouterLink instances, each RemoteRouterLink is assigned a
// LinkSide at construction time. This assignment is arbitrary but will always
// be the opposite of the LinkSide assigned to the RemoteRouteLink on the other
// end.
// NOTE: This implementation must take caution when calling into any Router. See
// note on RouterLink's own class documentation.
class RemoteRouterLink : public RouterLink {
// Constructs a new RemoteRouterLink which sends messages over `node_link`
// using `sublink` specifically. `side` is the side of this link on which
// this RemoteRouterLink falls (side A or B), and `type` indicates what type
// of link it is -- which for remote links must be either kCentral,
// kPeripheralInward, or kPeripheralOutward. If the link is kCentral, a
// non-null `link_state` may be provided to use as the link's RouterLinkState.
static Ref<RemoteRouterLink> Create(Ref<NodeLink> node_link,
SublinkId sublink,
FragmentRef<RouterLinkState> link_state,
LinkType type,
LinkSide side);
const Ref<NodeLink>& node_link() const { return node_link_; }
SublinkId sublink() const { return sublink_; }
// Sets this link's RouterLinkState.
// If `state` is null and this link is on side B, this call is a no-op. If
// `state` is null and this link is on side A, this call will kick off an
// asynchronous allocation of a new RouterLinkState. When that completes, the
// new state will be adopted by side A and shared with side B.
// If `state` references a pending fragment and this link is on side A, the
// call is a no-op. If `state` references a pending fragment and this link
// is on side B, this operation will be automatically deferred until the
// NodeLink acquires a mapping of the buffer referenced by `state` and the
// fragment can be resolved to an addressable one.
// Finally, if `state` references a valid, addressable fragment, it is
// adopted as-is.
void SetLinkState(FragmentRef<RouterLinkState> state);
// RouterLink:
LinkType GetType() const override;
RouterLinkState* GetLinkState() const override;
bool HasLocalPeer(const Router& router) override;
bool IsRemoteLinkTo(const NodeLink& node_link, SublinkId sublink) override;
void AcceptParcel(Parcel& parcel) override;
void AcceptRouteClosure(SequenceNumber sequence_length) override;
void MarkSideStable() override;
bool TryLockForBypass(const NodeName& bypass_request_source) override;
bool TryLockForClosure() override;
void Unlock() override;
bool FlushOtherSideIfWaiting() override;
bool CanNodeRequestBypass(const NodeName& bypass_request_source) override;
void Deactivate() override;
std::string Describe() const override;
RemoteRouterLink(Ref<NodeLink> node_link,
SublinkId sublink,
FragmentRef<RouterLinkState> link_state,
LinkType type,
LinkSide side);
~RemoteRouterLink() override;
void AllocateAndShareLinkState();
const Ref<NodeLink> node_link_;
const SublinkId sublink_;
const LinkType type_;
const LinkSide side_;
// Local atomic cache of whether this side of the link is marked stable. If
// MarkSideStable() is called when no RouterLinkState is present, this will be
// used to remember it once a RouterLinkState is finally established.
std::atomic<bool> side_is_stable_{false};
// A reference to the shared memory Fragment containing the RouterLinkState
// shared by both ends of this RouterLink. Always null for non-central links,
// and may be null for a central links if its RouterLinkState has not yet been
// allocated or shared.
// Must be set at most once and is only retained by this object to keep the
// fragment allocated. Access is unguarded and is restricted to
// SetLinkState(), and only allowed while `link_state_` below is still null.
// Any other access is unsafe. Use GetLinkState() to get a usable reference to
// the RouterLinkState instance.
FragmentRef<RouterLinkState> link_state_fragment_;
// Cached address of the shared RouterLinkState referenced by
// `link_state_fragment_`. Once this is set to a non-null value it retains
// that value indefinitely, so any non-null value loaded from this field is
// safe to dereference for the duration of the RemoteRouterLink's lifetime.
std::atomic<RouterLinkState*> link_state_{nullptr};
} // namespace ipcz