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// 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.
#ifndef IPCZ_SRC_IPCZ_REMOTE_ROUTER_LINK_H_
#define IPCZ_SRC_IPCZ_REMOTE_ROUTER_LINK_H_
#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 {
public:
// 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` must be provided for 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_; }
// RouterLink:
LinkType GetType() const override;
RouterLinkState* GetLinkState() const override;
Ref<Router> GetLocalPeer() override;
RemoteRouterLink* AsRemoteRouterLink() override;
void AcceptParcel(Parcel& parcel) override;
void AcceptRouteClosure(SequenceNumber sequence_length) override;
void AcceptRouteDisconnected() 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 BypassPeer(const NodeName& bypass_target_node,
SublinkId bypass_request_sublink) override;
void StopProxying(SequenceNumber inbound_sequence_length,
SequenceNumber outbound_sequence_length) override;
void ProxyWillStop(SequenceNumber inbound_sequence_length) override;
void BypassPeerWithLink(SublinkId new_sublink,
FragmentRef<RouterLinkState> new_link_state,
SequenceNumber inbound_sequence_length) override;
void StopProxyingToLocalPeer(
SequenceNumber outbound_sequence_length) override;
void Deactivate() override;
std::string Describe() const override;
private:
RemoteRouterLink(Ref<NodeLink> node_link,
SublinkId sublink,
FragmentRef<RouterLinkState> link_state,
LinkType type,
LinkSide side);
~RemoteRouterLink() override;
// Sets this link's RouterLinkState. `state` must be pending or addressable
// and this must be a central link.
void SetLinkState(FragmentRef<RouterLinkState> state);
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. Only used by central links. Once
// this is set to a non-null fragment and that fragment is addressable by this
// link's node, `link_state_` is also updated to cache a pointer to this
// fragment's mapped memory.
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
#endif // IPCZ_SRC_IPCZ_REMOTE_ROUTER_LINK_H_