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// Copyright 2020 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 <memory>
#include <vector>
#include "base/memory/weak_ptr.h"
#include "base/observer_list_types.h"
#include "base/optional.h"
#include "net/base/net_export.h"
#include "net/dns/dns_config.h"
namespace net {
class DnsSession;
class HostCache;
class URLRequestContext;
// Per-URLRequestContext data used by HostResolver. Expected to be owned by the
// ContextHostResolver, and all usage/references are expected to be cleaned up
// or cancelled before the URLRequestContext goes out of service.
class NET_EXPORT_PRIVATE ResolveContext : public base::CheckedObserver {
ResolveContext(URLRequestContext* url_request_context, bool enable_caching);
ResolveContext(const ResolveContext&) = delete;
ResolveContext& operator=(const ResolveContext&) = delete;
~ResolveContext() override;
// Sets the "current" session for this ResolveContext and clears all session-
// specific properties.
// Find the index of a DoH server to use for this attempt. Starts from
// |starting_doh_server_index| and finds the first eligible server (wrapping
// around as necessary) below failure limits, or of no eligible servers are
// below failure limits, the one with the oldest last failure. If in AUTOMATIC
// mode, a server is only eligible after a successful DoH probe. Returns
// nullopt if there are no eligible DoH servers or |session| is not the
// current session.
base::Optional<size_t> DohServerIndexToUse(
size_t starting_doh_server_index,
DnsConfig::SecureDnsMode secure_dns_mode,
const DnsSession* session);
// Returns the number of DoH servers with successful probe states. Always 0 if
// |session| is not the current session.
size_t NumAvailableDohServers(const DnsSession* session) const;
// Returns whether |doh_server_index| is marked available. Always |false| if
// |session| is not the current session.
bool GetDohServerAvailability(size_t doh_server_index,
const DnsSession* session) const;
// Record the latest DoH probe state. Noop if |session| is not the current
// session.
void SetProbeSuccess(size_t doh_server_index,
bool success,
const DnsSession* session);
URLRequestContext* url_request_context() { return url_request_context_; }
void set_url_request_context(URLRequestContext* url_request_context) {
url_request_context_ = url_request_context;
HostCache* host_cache() { return host_cache_.get(); }
// Invalidate or clear saved per-context cached data that is not expected to
// stay valid between connections or sessions (eg the HostCache and DNS server
// stats). |new_session|, if non-null, will be the new "current" session for
// which per-session data will be kept.
void InvalidateCaches(DnsSession* new_session);
const DnsSession* current_session_for_testing() const {
return current_session_.get();
bool IsCurrentSession(const DnsSession* session) const;
URLRequestContext* url_request_context_;
std::unique_ptr<HostCache> host_cache_;
// Per-session data is only stored and valid for the latest session. Before
// accessing, should check that |current_session_| is valid and matches a
// passed in DnsSession.
// Using a WeakPtr, so even if a new session has the same pointer as an old
// invalidated session, it can be recognized as a different session.
// TODO( Make const DnsSession once server stats have been
// moved and no longer need to be read from DnsSession for availability logic.
base::WeakPtr<DnsSession> current_session_;
std::vector<bool> doh_server_availability_;
} // namespace net