// 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. #ifndef NET_DNS_DNS_UDP_TRACKER_H_ #define NET_DNS_DNS_UDP_TRACKER_H_ #include #include "base/containers/circular_deque.h" #include "base/memory/raw_ptr.h" #include "base/time/default_tick_clock.h" #include "base/time/time.h" #include "net/base/net_export.h" namespace base { class TickClock; } // namespace base namespace net { // Data tracker for DNS UDP and its usage of local ports. Intended to be owned // by a DnsSession and thus keep track of the data session-wide. Responsible for // related metrics and used to inform behavior based on the stored data. // // TODO(ericorth@chromium.org): Add methods to access the stored data or // conclusions about it. class NET_EXPORT_PRIVATE DnsUdpTracker { public: static constexpr base::TimeDelta kMaxAge = base::Minutes(10); static constexpr size_t kMaxRecordedQueries = 256; // How recently an ID needs to be recorded in a recent query to be considered // "recognized". static constexpr base::TimeDelta kMaxRecognizedIdAge = base::Seconds(15); // Numbers of ID mismatches required to set the |low_entropy_| flag. Also // serves as the max number of mismatches to be recorded, as no more entries // are recorded after setting the flag. static constexpr size_t kUnrecognizedIdMismatchThreshold = 8; static constexpr size_t kRecognizedIdMismatchThreshold = 128; // Number of reuses of the same port required to set the |low_entropy_| flag. static constexpr int kPortReuseThreshold = 2; DnsUdpTracker(); ~DnsUdpTracker(); DnsUdpTracker(DnsUdpTracker&&); DnsUdpTracker& operator=(DnsUdpTracker&&); void RecordQuery(uint16_t port, uint16_t query_id); void RecordResponseId(uint16_t query_id, uint16_t response_id); void RecordConnectionError(int connection_error); // If true, the entropy from random UDP port and DNS ID has been detected to // potentially be low, e.g. due to exhaustion of the port pool or mismatches // on IDs. bool low_entropy() const { return low_entropy_; } void set_tick_clock_for_testing(base::TickClock* tick_clock) { tick_clock_ = tick_clock; } private: struct QueryData; void PurgeOldRecords(); void SaveQuery(QueryData query); void SaveIdMismatch(uint16_t it); bool low_entropy_ = false; base::circular_deque recent_queries_; // Times of recent ID mismatches, separated by whether or not the ID was // recognized from recent queries. base::circular_deque recent_unrecognized_id_hits_; base::circular_deque recent_recognized_id_hits_; raw_ptr tick_clock_ = base::DefaultTickClock::GetInstance(); }; } // namespace net #endif // NET_DNS_DNS_UDP_TRACKER_H_