/*
 * This file is part of PowerDNS or dnsdist.
 * Copyright -- PowerDNS.COM B.V. and its contributors
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of version 2 of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * In addition, for the avoidance of any doubt, permission is granted to
 * link this program with OpenSSL and to (re)distribute the binaries
 * produced as the result of such linking.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
#pragma once
#include "config.h"
#include "ext/luawrapper/include/LuaContext.hpp"

#include <condition_variable>
#include <memory>
#include <mutex>
#include <string>
#include <thread>
#include <time.h>
#include <unistd.h>
#include <unordered_map>

#include <boost/variant.hpp>

#include "circular_buffer.hh"
#include "dnscrypt.hh"
#include "dnsdist-cache.hh"
#include "dnsdist-dynbpf.hh"
#include "dnsdist-idstate.hh"
#include "dnsdist-lbpolicies.hh"
#include "dnsdist-protocols.hh"
#include "dnsname.hh"
#include "doh.hh"
#include "ednsoptions.hh"
#include "iputils.hh"
#include "misc.hh"
#include "mplexer.hh"
#include "noinitvector.hh"
#include "sholder.hh"
#include "tcpiohandler.hh"
#include "uuid-utils.hh"
#include "proxy-protocol.hh"
#include "stat_t.hh"

uint64_t uptimeOfProcess(const std::string& str);

extern uint16_t g_ECSSourcePrefixV4;
extern uint16_t g_ECSSourcePrefixV6;
extern bool g_ECSOverride;

using QTag = std::unordered_map<string, string>;

class IncomingTCPConnectionState;

struct ClientState;

struct DNSQuestion
{
  DNSQuestion(InternalQueryState& ids_, PacketBuffer& data_):
    data(data_), ids(ids_), ecsPrefixLength(ids.origRemote.sin4.sin_family == AF_INET ? g_ECSSourcePrefixV4 : g_ECSSourcePrefixV6), ecsOverride(g_ECSOverride) {
  }
  DNSQuestion(const DNSQuestion&) = delete;
  DNSQuestion& operator=(const DNSQuestion&) = delete;
  DNSQuestion(DNSQuestion&&) = default;
  virtual ~DNSQuestion() = default;

  std::string getTrailingData() const;
  bool setTrailingData(const std::string&);
  const PacketBuffer& getData() const
  {
    return data;
  }
  PacketBuffer& getMutableData()
  {
    return data;
  }

  dnsheader* getHeader()
  {
    if (data.size() < sizeof(dnsheader)) {
      throw std::runtime_error("Trying to access the dnsheader of a too small (" + std::to_string(data.size()) + ") DNSQuestion buffer");
    }
    return reinterpret_cast<dnsheader*>(&data.at(0));
  }

  const dnsheader* getHeader() const
  {
    if (data.size() < sizeof(dnsheader)) {
      throw std::runtime_error("Trying to access the dnsheader of a too small (" + std::to_string(data.size()) + ") DNSQuestion buffer");
    }
    return reinterpret_cast<const dnsheader*>(&data.at(0));
  }

  bool hasRoomFor(size_t more) const
  {
    return data.size() <= getMaximumSize() && (getMaximumSize() - data.size()) >= more;
  }

  size_t getMaximumSize() const
  {
    if (overTCP()) {
      return std::numeric_limits<uint16_t>::max();
    }
    return 4096;
  }

  dnsdist::Protocol getProtocol() const
  {
    return ids.protocol;
  }

  bool overTCP() const
  {
    return !(ids.protocol == dnsdist::Protocol::DoUDP || ids.protocol == dnsdist::Protocol::DNSCryptUDP);
  }

  void setTag(std::string&& key, std::string&& value) {
    if (!ids.qTag) {
      ids.qTag = std::make_unique<QTag>();
    }
    ids.qTag->insert_or_assign(std::move(key), std::move(value));
  }

  void setTag(const std::string& key, const std::string& value) {
    if (!ids.qTag) {
      ids.qTag = std::make_unique<QTag>();
    }
    ids.qTag->insert_or_assign(key, value);
  }

  const struct timespec& getQueryRealTime() const
  {
    return ids.queryRealTime.d_start;
  }

  bool isAsynchronous() const
  {
    return asynchronous;
  }

  std::shared_ptr<IncomingTCPConnectionState> getIncomingTCPState() const
  {
    return d_incomingTCPState;
  }

  ClientState* getFrontend() const
  {
    return ids.cs;
  }

protected:
  PacketBuffer& data;

public:
  InternalQueryState& ids;
  std::unique_ptr<Netmask> ecs{nullptr};
  std::string sni; /* Server Name Indication, if any (DoT or DoH) */
  mutable std::unique_ptr<EDNSOptionViewMap> ednsOptions; /* this needs to be mutable because it is parsed just in time, when DNSQuestion is read-only */
  std::shared_ptr<IncomingTCPConnectionState> d_incomingTCPState{nullptr};
  std::unique_ptr<std::vector<ProxyProtocolValue>> proxyProtocolValues{nullptr};
  uint16_t ecsPrefixLength;
  uint8_t ednsRCode{0};
  bool ecsOverride;
  bool useECS{true};
  bool addXPF{true};
  bool asynchronous{false};
};

struct DownstreamState;

struct DNSResponse : DNSQuestion
{
  DNSResponse(InternalQueryState& ids_, PacketBuffer& data_, const std::shared_ptr<DownstreamState>& downstream):
    DNSQuestion(ids_, data_), d_downstream(downstream) { }
  DNSResponse(const DNSResponse&) = delete;
  DNSResponse& operator=(const DNSResponse&) = delete;
  DNSResponse(DNSResponse&&) = default;

  const std::shared_ptr<DownstreamState>& d_downstream;
};

/* so what could you do:
   drop,
   fake up nxdomain,
   provide actual answer,
   allow & and stop processing,
   continue processing,
   modify header:    (servfail|refused|notimp), set TC=1,
   send to pool */

class DNSAction
{
public:
  enum class Action : uint8_t { Drop, Nxdomain, Refused, Spoof, Allow, HeaderModify, Pool, Delay, Truncate, ServFail, None, NoOp, NoRecurse, SpoofRaw, SpoofPacket };
  static std::string typeToString(const Action& action)
  {
    switch(action) {
    case Action::Drop:
      return "Drop";
    case Action::Nxdomain:
      return "Send NXDomain";
    case Action::Refused:
      return "Send Refused";
    case Action::Spoof:
      return "Spoof an answer";
    case Action::SpoofPacket:
      return "Spoof a raw answer from bytes";
    case Action::SpoofRaw:
      return "Spoof an answer from raw bytes";
    case Action::Allow:
      return "Allow";
    case Action::HeaderModify:
      return "Modify the header";
    case Action::Pool:
      return "Route to a pool";
    case Action::Delay:
      return "Delay";
    case Action::Truncate:
      return "Truncate over UDP";
    case Action::ServFail:
      return "Send ServFail";
    case Action::None:
    case Action::NoOp:
      return "Do nothing";
    case Action::NoRecurse:
      return "Set rd=0";
    }

    return "Unknown";
  }

  virtual Action operator()(DNSQuestion*, string* ruleresult) const =0;
  virtual ~DNSAction()
  {
  }
  virtual string toString() const = 0;
  virtual std::map<string, double> getStats() const
  {
    return {{}};
  }
  virtual void reload()
  {
  }
};

class DNSResponseAction
{
public:
  enum class Action : uint8_t { Allow, Delay, Drop, HeaderModify, ServFail, None };
  virtual Action operator()(DNSResponse*, string* ruleresult) const =0;
  virtual ~DNSResponseAction()
  {
  }
  virtual string toString() const = 0;
  virtual void reload()
  {
  }
};

struct DynBlock
{
  DynBlock(): action(DNSAction::Action::None), warning(false)
  {
    until.tv_sec = 0;
    until.tv_nsec = 0;
  }

  DynBlock(const std::string& reason_, const struct timespec& until_, const DNSName& domain_, DNSAction::Action action_): reason(reason_), domain(domain_), until(until_), action(action_), warning(false)
  {
  }

  DynBlock(const DynBlock& rhs): reason(rhs.reason), domain(rhs.domain), until(rhs.until), action(rhs.action), warning(rhs.warning), bpf(rhs.bpf)
  {
    blocks.store(rhs.blocks);
  }

  DynBlock(DynBlock&& rhs): reason(std::move(rhs.reason)), domain(std::move(rhs.domain)), until(rhs.until), action(rhs.action), warning(rhs.warning), bpf(rhs.bpf)
  {
    blocks.store(rhs.blocks);
  }

  DynBlock& operator=(const DynBlock& rhs)
  {
    reason = rhs.reason;
    until = rhs.until;
    domain = rhs.domain;
    action = rhs.action;
    blocks.store(rhs.blocks);
    warning = rhs.warning;
    bpf = rhs.bpf;
    return *this;
  }

  DynBlock& operator=(DynBlock&& rhs)
  {
    reason = std::move(rhs.reason);
    until = rhs.until;
    domain = std::move(rhs.domain);
    action = rhs.action;
    blocks.store(rhs.blocks);
    warning = rhs.warning;
    bpf = rhs.bpf;
    return *this;
  }

  string reason;
  DNSName domain;
  struct timespec until;
  mutable std::atomic<unsigned int> blocks;
  DNSAction::Action action{DNSAction::Action::None};
  bool warning{false};
  bool bpf{false};
};

extern GlobalStateHolder<NetmaskTree<DynBlock, AddressAndPortRange>> g_dynblockNMG;

extern vector<pair<struct timeval, std::string> > g_confDelta;

using pdns::stat_t;

struct DNSDistStats
{
  stat_t responses{0};
  stat_t servfailResponses{0};
  stat_t queries{0};
  stat_t frontendNXDomain{0};
  stat_t frontendServFail{0};
  stat_t frontendNoError{0};
  stat_t nonCompliantQueries{0};
  stat_t nonCompliantResponses{0};
  stat_t rdQueries{0};
  stat_t emptyQueries{0};
  stat_t aclDrops{0};
  stat_t dynBlocked{0};
  stat_t ruleDrop{0};
  stat_t ruleNXDomain{0};
  stat_t ruleRefused{0};
  stat_t ruleServFail{0};
  stat_t ruleTruncated{0};
  stat_t selfAnswered{0};
  stat_t downstreamTimeouts{0};
  stat_t downstreamSendErrors{0};
  stat_t truncFail{0};
  stat_t noPolicy{0};
  stat_t cacheHits{0};
  stat_t cacheMisses{0};
  stat_t latency0_1{0}, latency1_10{0}, latency10_50{0}, latency50_100{0}, latency100_1000{0}, latencySlow{0}, latencySum{0}, latencyCount{0};
  stat_t securityStatus{0};
  stat_t dohQueryPipeFull{0};
  stat_t dohResponsePipeFull{0};
  stat_t outgoingDoHQueryPipeFull{0};
  stat_t proxyProtocolInvalid{0};
  stat_t tcpQueryPipeFull{0};
  stat_t tcpCrossProtocolQueryPipeFull{0};
  stat_t tcpCrossProtocolResponsePipeFull{0};
  double latencyAvg100{0}, latencyAvg1000{0}, latencyAvg10000{0}, latencyAvg1000000{0};
  double latencyTCPAvg100{0}, latencyTCPAvg1000{0}, latencyTCPAvg10000{0}, latencyTCPAvg1000000{0};
  double latencyDoTAvg100{0}, latencyDoTAvg1000{0}, latencyDoTAvg10000{0}, latencyDoTAvg1000000{0};
  double latencyDoHAvg100{0}, latencyDoHAvg1000{0}, latencyDoHAvg10000{0}, latencyDoHAvg1000000{0};
  using statfunction_t =  std::function<uint64_t(const std::string&)>;
  using entry_t = boost::variant<stat_t*, pdns::stat_t_trait<double>*, double*, statfunction_t>;
  struct EntryPair
  {
    std::string d_name;
    entry_t d_value;
  };

  SharedLockGuarded<std::vector<EntryPair>> entries{std::vector<EntryPair>{
    {"responses", &responses},
    {"servfail-responses", &servfailResponses},
    {"queries", &queries},
    {"frontend-nxdomain", &frontendNXDomain},
    {"frontend-servfail", &frontendServFail},
    {"frontend-noerror", &frontendNoError},
    {"acl-drops", &aclDrops},
    {"rule-drop", &ruleDrop},
    {"rule-nxdomain", &ruleNXDomain},
    {"rule-refused", &ruleRefused},
    {"rule-servfail", &ruleServFail},
    {"rule-truncated", &ruleTruncated},
    {"self-answered", &selfAnswered},
    {"downstream-timeouts", &downstreamTimeouts},
    {"downstream-send-errors", &downstreamSendErrors},
    {"trunc-failures", &truncFail},
    {"no-policy", &noPolicy},
    {"latency0-1", &latency0_1},
    {"latency1-10", &latency1_10},
    {"latency10-50", &latency10_50},
    {"latency50-100", &latency50_100},
    {"latency100-1000", &latency100_1000},
    {"latency-slow", &latencySlow},
    {"latency-avg100", &latencyAvg100},
    {"latency-avg1000", &latencyAvg1000},
    {"latency-avg10000", &latencyAvg10000},
    {"latency-avg1000000", &latencyAvg1000000},
    {"latency-tcp-avg100", &latencyTCPAvg100},
    {"latency-tcp-avg1000", &latencyTCPAvg1000},
    {"latency-tcp-avg10000", &latencyTCPAvg10000},
    {"latency-tcp-avg1000000", &latencyTCPAvg1000000},
    {"latency-dot-avg100", &latencyDoTAvg100},
    {"latency-dot-avg1000", &latencyDoTAvg1000},
    {"latency-dot-avg10000", &latencyDoTAvg10000},
    {"latency-dot-avg1000000", &latencyDoTAvg1000000},
    {"latency-doh-avg100", &latencyDoHAvg100},
    {"latency-doh-avg1000", &latencyDoHAvg1000},
    {"latency-doh-avg10000", &latencyDoHAvg10000},
    {"latency-doh-avg1000000", &latencyDoHAvg1000000},
    {"uptime", uptimeOfProcess},
    {"real-memory-usage", getRealMemoryUsage},
    {"special-memory-usage", getSpecialMemoryUsage},
    {"udp-in-errors", std::bind(udpErrorStats, "udp-in-errors")},
    {"udp-noport-errors", std::bind(udpErrorStats, "udp-noport-errors")},
    {"udp-recvbuf-errors", std::bind(udpErrorStats, "udp-recvbuf-errors")},
    {"udp-sndbuf-errors", std::bind(udpErrorStats, "udp-sndbuf-errors")},
    {"udp-in-csum-errors", std::bind(udpErrorStats, "udp-in-csum-errors")},
    {"udp6-in-errors", std::bind(udp6ErrorStats, "udp6-in-errors")},
    {"udp6-recvbuf-errors", std::bind(udp6ErrorStats, "udp6-recvbuf-errors")},
    {"udp6-sndbuf-errors", std::bind(udp6ErrorStats, "udp6-sndbuf-errors")},
    {"udp6-noport-errors", std::bind(udp6ErrorStats, "udp6-noport-errors")},
    {"udp6-in-csum-errors", std::bind(udp6ErrorStats, "udp6-in-csum-errors")},
    {"tcp-listen-overflows", std::bind(tcpErrorStats, "ListenOverflows")},
    {"noncompliant-queries", &nonCompliantQueries},
    {"noncompliant-responses", &nonCompliantResponses},
    {"proxy-protocol-invalid", &proxyProtocolInvalid},
    {"rdqueries", &rdQueries},
    {"empty-queries", &emptyQueries},
    {"cache-hits", &cacheHits},
    {"cache-misses", &cacheMisses},
    {"cpu-iowait", getCPUIOWait},
    {"cpu-steal", getCPUSteal},
    {"cpu-sys-msec", getCPUTimeSystem},
    {"cpu-user-msec", getCPUTimeUser},
    {"fd-usage", getOpenFileDescriptors},
    {"dyn-blocked", &dynBlocked},
    {"dyn-block-nmg-size", [](const std::string&) { return g_dynblockNMG.getLocal()->size(); }},
    {"security-status", &securityStatus},
    {"doh-query-pipe-full", &dohQueryPipeFull},
    {"doh-response-pipe-full", &dohResponsePipeFull},
    {"outgoing-doh-query-pipe-full", &outgoingDoHQueryPipeFull},
    {"tcp-query-pipe-full", &tcpQueryPipeFull},
    {"tcp-cross-protocol-query-pipe-full", &tcpCrossProtocolQueryPipeFull},
    {"tcp-cross-protocol-response-pipe-full", &tcpCrossProtocolResponsePipeFull},
    // Latency histogram
    {"latency-sum", &latencySum},
    {"latency-count", &latencyCount},
  }};
  struct MutableCounter
  {
    MutableCounter() = default;
    MutableCounter(MutableCounter&& rhs): d_value(rhs.d_value.load())
    {
    }

    mutable stat_t d_value{0};
  };
  struct MutableGauge
  {
    MutableGauge() = default;
    MutableGauge(MutableGauge&& rhs): d_value(rhs.d_value.load())
    {
    }

    mutable pdns::stat_t_trait<double> d_value{0};
  };
  SharedLockGuarded<std::map<std::string, MutableCounter, std::less<>>> customCounters;
  SharedLockGuarded<std::map<std::string, MutableGauge, std::less<>>> customGauges;
};

extern struct DNSDistStats g_stats;

class BasicQPSLimiter
{
public:
  BasicQPSLimiter()
  {
  }

  BasicQPSLimiter(unsigned int burst): d_tokens(burst)
  {
    d_prev.start();
  }

  virtual ~BasicQPSLimiter()
  {
  }

  bool check(unsigned int rate, unsigned int burst) const // this is not quite fair
  {
    if (checkOnly(rate, burst)) {
      addHit();
      return true;
    }

    return false;
  }

  bool checkOnly(unsigned int rate, unsigned int burst) const // this is not quite fair
  {
    auto delta = d_prev.udiffAndSet();

    if (delta > 0.0) { // time, frequently, does go backwards..
      d_tokens += 1.0 * rate * (delta/1000000.0);
    }

    if (d_tokens > burst) {
      d_tokens = burst;
    }

    bool ret = false;
    if (d_tokens >= 1.0) { // we need this because burst=1 is weird otherwise
      ret = true;
    }

    return ret;
  }

  virtual void addHit() const
  {
    --d_tokens;
  }

  bool seenSince(const struct timespec& cutOff) const
  {
    return cutOff < d_prev.d_start;
  }

protected:
  mutable StopWatch d_prev;
  mutable double d_tokens{0.0};
};

class QPSLimiter : public BasicQPSLimiter
{
public:
  QPSLimiter(): BasicQPSLimiter()
  {
  }

  QPSLimiter(unsigned int rate, unsigned int burst): BasicQPSLimiter(burst), d_rate(rate), d_burst(burst), d_passthrough(false)
  {
    d_prev.start();
  }

  unsigned int getRate() const
  {
    return d_passthrough ? 0 : d_rate;
  }

  bool check() const // this is not quite fair
  {
    if (d_passthrough) {
      return true;
    }

    return BasicQPSLimiter::check(d_rate, d_burst);
  }

  bool checkOnly() const
  {
    if (d_passthrough) {
      return true;
    }

    return BasicQPSLimiter::checkOnly(d_rate, d_burst);
  }

  void addHit() const override
  {
    if (!d_passthrough) {
      --d_tokens;
    }
  }

private:
  unsigned int d_rate{0};
  unsigned int d_burst{0};
  bool d_passthrough{true};
};

typedef std::unordered_map<string, unsigned int> QueryCountRecords;
typedef std::function<std::tuple<bool, string>(const DNSQuestion* dq)> QueryCountFilter;
struct QueryCount {
  QueryCount()
  {
  }
  ~QueryCount()
  {
  }
  SharedLockGuarded<QueryCountRecords> records;
  QueryCountFilter filter;
  bool enabled{false};
};

extern QueryCount g_qcount;

struct ClientState
{
  ClientState(const ComboAddress& local_, bool isTCP_, bool doReusePort, int fastOpenQueue, const std::string& itfName, const std::set<int>& cpus_): cpus(cpus_), interface(itfName), local(local_), fastOpenQueueSize(fastOpenQueue), tcp(isTCP_), reuseport(doReusePort)
  {
  }

  stat_t queries{0};
  stat_t nonCompliantQueries{0};
  mutable stat_t responses{0};
  mutable stat_t tcpDiedReadingQuery{0};
  mutable stat_t tcpDiedSendingResponse{0};
  mutable stat_t tcpGaveUp{0};
  mutable stat_t tcpClientTimeouts{0};
  mutable stat_t tcpDownstreamTimeouts{0};
  /* current number of connections to this frontend */
  mutable stat_t tcpCurrentConnections{0};
  /* maximum number of concurrent connections to this frontend reached */
  mutable stat_t tcpMaxConcurrentConnections{0};
  stat_t tlsNewSessions{0}; // A new TLS session has been negotiated, no resumption
  stat_t tlsResumptions{0}; // A TLS session has been resumed, either via session id or via a TLS ticket
  stat_t tlsUnknownTicketKey{0}; // A TLS ticket has been presented but we don't have the associated key (might have expired)
  stat_t tlsInactiveTicketKey{0}; // A TLS ticket has been successfully resumed but the key is no longer active, we should issue a new one
  stat_t tls10queries{0};   // valid DNS queries received via TLSv1.0
  stat_t tls11queries{0};   // valid DNS queries received via TLSv1.1
  stat_t tls12queries{0};   // valid DNS queries received via TLSv1.2
  stat_t tls13queries{0};   // valid DNS queries received via TLSv1.3
  stat_t tlsUnknownqueries{0};   // valid DNS queries received via unknown TLS version
  pdns::stat_t_trait<double> tcpAvgQueriesPerConnection{0.0};
  /* in ms */
  pdns::stat_t_trait<double> tcpAvgConnectionDuration{0.0};
  std::set<int> cpus;
  std::string interface;
  ComboAddress local;
  std::vector<std::pair<ComboAddress, int>> d_additionalAddresses;
  std::shared_ptr<DNSCryptContext> dnscryptCtx{nullptr};
  std::shared_ptr<TLSFrontend> tlsFrontend{nullptr};
  std::shared_ptr<DOHFrontend> dohFrontend{nullptr};
  std::shared_ptr<BPFFilter> d_filter{nullptr};
  size_t d_maxInFlightQueriesPerConn{1};
  size_t d_tcpConcurrentConnectionsLimit{0};
  int udpFD{-1};
  int tcpFD{-1};
  int tcpListenQueueSize{SOMAXCONN};
  int fastOpenQueueSize{0};
  bool muted{false};
  bool tcp;
  bool reuseport;
  bool ready{false};

  int getSocket() const
  {
    return udpFD != -1 ? udpFD : tcpFD;
  }

  bool isUDP() const
  {
    return udpFD != -1;
  }

  bool isTCP() const
  {
    return udpFD == -1;
  }

  bool isDoH() const
  {
    return dohFrontend != nullptr;
  }

  bool hasTLS() const
  {
    return tlsFrontend != nullptr || (dohFrontend != nullptr && dohFrontend->isHTTPS());
  }

  dnsdist::Protocol getProtocol() const
  {
    if (dnscryptCtx) {
      if (udpFD != -1) {
        return dnsdist::Protocol::DNSCryptUDP;
      }
      return dnsdist::Protocol::DNSCryptTCP;
    }
    if (isDoH()) {
      return dnsdist::Protocol::DoH;
    }
    else if (hasTLS()) {
      return dnsdist::Protocol::DoT;
    }
    else if (udpFD != -1) {
      return dnsdist::Protocol::DoUDP;
    }
    else {
      return dnsdist::Protocol::DoTCP;
    }
  }

  std::string getType() const
  {
    std::string result = udpFD != -1 ? "UDP" : "TCP";

    if (dohFrontend) {
      if (dohFrontend->isHTTPS()) {
        result += " (DNS over HTTPS)";
      }
      else {
        result += " (DNS over HTTP)";
      }
    }
    else if (tlsFrontend) {
      result += " (DNS over TLS)";
    }
    else if (dnscryptCtx) {
      result += " (DNSCrypt)";
    }

    return result;
  }

  void detachFilter(int socket)
  {
    if (d_filter) {
      d_filter->removeSocket(socket);
      d_filter = nullptr;
    }
  }

  void attachFilter(shared_ptr<BPFFilter> bpf, int socket)
  {
    detachFilter(socket);

    bpf->addSocket(socket);
    d_filter = bpf;
  }

  void detachFilter()
  {
    if (d_filter) {
      detachFilter(getSocket());
      for (const auto& [addr, socket] : d_additionalAddresses) {
        (void) addr;
        if (socket != -1) {
          detachFilter(socket);
        }
      }

      d_filter = nullptr;
    }
  }

  void attachFilter(shared_ptr<BPFFilter> bpf)
  {
    detachFilter();

    bpf->addSocket(getSocket());
    for (const auto& [addr, socket] : d_additionalAddresses) {
      (void) addr;
      if (socket != -1) {
        bpf->addSocket(socket);
      }
    }
    d_filter = bpf;
  }

  void updateTCPMetrics(size_t nbQueries, uint64_t durationMs)
  {
    tcpAvgQueriesPerConnection = (99.0 * tcpAvgQueriesPerConnection / 100.0) + (nbQueries / 100.0);
    tcpAvgConnectionDuration = (99.0 * tcpAvgConnectionDuration / 100.0) + (durationMs / 100.0);
  }
};

struct CrossProtocolQuery;

struct DownstreamState: public std::enable_shared_from_this<DownstreamState>
{
  DownstreamState(const DownstreamState&) = delete;
  DownstreamState(DownstreamState&&) = delete;
  DownstreamState& operator=(const DownstreamState&) = delete;
  DownstreamState& operator=(DownstreamState&&) = delete;

  typedef std::function<std::tuple<DNSName, uint16_t, uint16_t>(const DNSName&, uint16_t, uint16_t, dnsheader*)> checkfunc_t;
  enum class Availability : uint8_t { Up, Down, Auto, Lazy };
  enum class LazyHealthCheckMode : uint8_t { TimeoutOnly, TimeoutOrServFail };

  struct Config
  {
    Config()
    {
    }
    Config(const ComboAddress& remote_): remote(remote_)
    {
    }

    TLSContextParameters d_tlsParams;
    set<string> pools;
    std::set<int> d_cpus;
    checkfunc_t checkFunction;
    std::optional<boost::uuids::uuid> id;
    DNSName checkName{"a.root-servers.net."};
    ComboAddress remote;
    ComboAddress sourceAddr;
    std::string sourceItfName;
    std::string d_tlsSubjectName;
    std::string d_dohPath;
    std::string name;
    std::string nameWithAddr;
    size_t d_numberOfSockets{1};
    size_t d_maxInFlightQueriesPerConn{1};
    size_t d_tcpConcurrentConnectionsLimit{0};
    int order{1};
    int d_weight{1};
    int tcpConnectTimeout{5};
    int tcpRecvTimeout{30};
    int tcpSendTimeout{30};
    int d_qpsLimit{0};
    unsigned int checkInterval{1};
    unsigned int sourceItf{0};
    QType checkType{QType::A};
    uint16_t checkClass{QClass::IN};
    uint16_t d_retries{5};
    uint16_t xpfRRCode{0};
    uint16_t checkTimeout{1000}; /* in milliseconds */
    uint16_t d_lazyHealthCheckSampleSize{100};
    uint16_t d_lazyHealthCheckMinSampleCount{1};
    uint16_t d_lazyHealthCheckFailedInterval{30};
    uint16_t d_lazyHealthCheckMaxBackOff{3600};
    uint8_t d_lazyHealthCheckThreshold{20};
    LazyHealthCheckMode d_lazyHealthCheckMode{LazyHealthCheckMode::TimeoutOrServFail};
    uint8_t maxCheckFailures{1};
    uint8_t minRiseSuccesses{1};
    Availability availability{Availability::Auto};
    bool d_tlsSubjectIsAddr{false};
    bool mustResolve{false};
    bool useECS{false};
    bool useProxyProtocol{false};
    bool setCD{false};
    bool disableZeroScope{false};
    bool tcpFastOpen{false};
    bool ipBindAddrNoPort{true};
    bool reconnectOnUp{false};
    bool d_tcpCheck{false};
    bool d_tcpOnly{false};
    bool d_addXForwardedHeaders{false}; // for DoH backends
    bool d_lazyHealthCheckUseExponentialBackOff{false};
    bool d_upgradeToLazyHealthChecks{false};
  };

  DownstreamState(DownstreamState::Config&& config, std::shared_ptr<TLSCtx> tlsCtx, bool connect);
  DownstreamState(const ComboAddress& remote): DownstreamState(DownstreamState::Config(remote), nullptr, false)
  {
  }

  ~DownstreamState();

  Config d_config;
  stat_t sendErrors{0};
  stat_t outstanding{0};
  stat_t reuseds{0};
  stat_t queries{0};
  stat_t responses{0};
  stat_t nonCompliantResponses{0};
  struct {
    stat_t sendErrors{0};
    stat_t reuseds{0};
    stat_t queries{0};
  } prev;
  stat_t tcpDiedSendingQuery{0};
  stat_t tcpDiedReadingResponse{0};
  stat_t tcpGaveUp{0};
  stat_t tcpReadTimeouts{0};
  stat_t tcpWriteTimeouts{0};
  stat_t tcpConnectTimeouts{0};
  /* current number of connections to this backend */
  stat_t tcpCurrentConnections{0};
  /* maximum number of concurrent connections to this backend reached */
  stat_t tcpMaxConcurrentConnections{0};
  /* number of times we had to enforce the maximum concurrent connections limit */
  stat_t tcpTooManyConcurrentConnections{0};
  stat_t tcpReusedConnections{0};
  stat_t tcpNewConnections{0};
  stat_t tlsResumptions{0};
  pdns::stat_t_trait<double> tcpAvgQueriesPerConnection{0.0};
  /* in ms */
  pdns::stat_t_trait<double> tcpAvgConnectionDuration{0.0};
  pdns::stat_t_trait<double> queryLoad{0.0};
  pdns::stat_t_trait<double> dropRate{0.0};

  SharedLockGuarded<std::vector<unsigned int>> hashes;
  LockGuarded<std::unique_ptr<FDMultiplexer>> mplexer{nullptr};
private:
  LockGuarded<std::map<uint16_t, IDState>> d_idStatesMap;
  vector<IDState> idStates;

  struct LazyHealthCheckStats
  {
    boost::circular_buffer<bool> d_lastResults;
    time_t d_nextCheck{0};
    enum class LazyStatus: uint8_t { Healthy = 0, PotentialFailure, Failed };
    LazyStatus d_status{LazyStatus::Healthy};
  };
  LockGuarded<LazyHealthCheckStats> d_lazyHealthCheckStats;

public:
  std::shared_ptr<TLSCtx> d_tlsCtx{nullptr};
  std::vector<int> sockets;
  StopWatch sw;
  QPSLimiter qps;
  std::atomic<uint64_t> idOffset{0};
  size_t socketsOffset{0};
  double latencyUsec{0.0};
  double latencyUsecTCP{0.0};
  unsigned int d_nextCheck{0};
  uint16_t currentCheckFailures{0};
  uint8_t consecutiveSuccessfulChecks{0};
  std::atomic<bool> hashesComputed{false};
  std::atomic<bool> connected{false};
  bool upStatus{false};

private:
  void connectUDPSockets();

  std::thread tid;
  std::mutex connectLock;
  std::condition_variable d_connectedWait;
  std::atomic_flag threadStarted;
  bool d_stopped{false};
public:

  void start();

  bool isUp() const
  {
    if (d_config.availability == Availability::Down) {
      return false;
    }
    else if (d_config.availability == Availability::Up) {
      return true;
    }
    return upStatus;
  }

  void setUp() {
    d_config.availability = Availability::Up;
  }

  void setUpStatus(bool newStatus)
  {
    upStatus = newStatus;
    if (!upStatus) {
      latencyUsec = 0.0;
      latencyUsecTCP = 0.0;
    }
  }
  void setDown()
  {
    d_config.availability = Availability::Down;
    latencyUsec = 0.0;
    latencyUsecTCP = 0.0;
  }
  void setAuto() {
    d_config.availability = Availability::Auto;
  }
  void setLazyAuto() {
    d_config.availability = Availability::Lazy;
    d_lazyHealthCheckStats.lock()->d_lastResults.set_capacity(d_config.d_lazyHealthCheckSampleSize);
  }
  bool healthCheckRequired(std::optional<time_t> currentTime = std::nullopt);

  const string& getName() const {
    return d_config.name;
  }
  const string& getNameWithAddr() const {
    return d_config.nameWithAddr;
  }
  void setName(const std::string& newName)
  {
    d_config.name = newName;
    d_config.nameWithAddr = newName.empty() ? d_config.remote.toStringWithPort() : (d_config.name + " (" + d_config.remote.toStringWithPort()+ ")");
  }

  string getStatus() const
  {
    string status;
    if (d_config.availability == DownstreamState::Availability::Up) {
      status = "UP";
    }
    else if (d_config.availability == DownstreamState::Availability::Down) {
      status = "DOWN";
    }
    else {
      status = (upStatus ? "up" : "down");
    }
    return status;
  }

  bool reconnect(bool initialAttempt = false);
  void waitUntilConnected();
  void hash();
  void setId(const boost::uuids::uuid& newId);
  void setWeight(int newWeight);
  void stop();
  bool isStopped() const
  {
    return d_stopped;
  }
  const boost::uuids::uuid& getID() const
  {
    return *d_config.id;
  }

  void updateTCPMetrics(size_t nbQueries, uint64_t durationMs)
  {
    tcpAvgQueriesPerConnection = (99.0 * tcpAvgQueriesPerConnection / 100.0) + (nbQueries / 100.0);
    tcpAvgConnectionDuration = (99.0 * tcpAvgConnectionDuration / 100.0) + (durationMs / 100.0);
  }

  void updateTCPLatency(double udiff)
  {
    latencyUsecTCP = (127.0 * latencyUsecTCP / 128.0) + udiff / 128.0;
  }

  void incQueriesCount()
  {
    ++queries;
    qps.addHit();
  }

  void incCurrentConnectionsCount();

  bool doHealthcheckOverTCP() const
  {
    return d_config.d_tcpOnly || d_config.d_tcpCheck || d_tlsCtx != nullptr;
  }

  bool isTCPOnly() const
  {
    return d_config.d_tcpOnly || d_tlsCtx != nullptr;
  }

  bool isDoH() const
  {
    return !d_config.d_dohPath.empty();
  }

  bool passCrossProtocolQuery(std::unique_ptr<CrossProtocolQuery>&& cpq);
  int pickSocketForSending();
  void pickSocketsReadyForReceiving(std::vector<int>& ready);
  void handleUDPTimeouts();
  void reportTimeoutOrError();
  void reportResponse(uint8_t rcode);
  void submitHealthCheckResult(bool initial, bool newState);
  time_t getNextLazyHealthCheck();
  uint16_t saveState(InternalQueryState&&);
  void restoreState(uint16_t id, InternalQueryState&&);
  std::optional<InternalQueryState> getState(uint16_t id);

  dnsdist::Protocol getProtocol() const
  {
    if (isDoH()) {
      return dnsdist::Protocol::DoH;
    }
    if (d_tlsCtx != nullptr) {
      return dnsdist::Protocol::DoT;
    }
    if (isTCPOnly()) {
      return dnsdist::Protocol::DoTCP;
    }
    return dnsdist::Protocol::DoUDP;
  }

  double getRelevantLatencyUsec() const
  {
    if (isTCPOnly()) {
      return latencyUsecTCP;
    }
    return latencyUsec;
  }

  static int s_udpTimeout;
  static bool s_randomizeSockets;
  static bool s_randomizeIDs;
private:
  void handleUDPTimeout(IDState& ids);
  void updateNextLazyHealthCheck(LazyHealthCheckStats& stats, bool checkScheduled, std::optional<time_t> currentTime = std::nullopt);
};
using servers_t = vector<std::shared_ptr<DownstreamState>>;

void responderThread(std::shared_ptr<DownstreamState> state);
extern LockGuarded<LuaContext> g_lua;
extern std::string g_outputBuffer; // locking for this is ok, as locked by g_luamutex

class DNSRule
{
public:
  virtual ~DNSRule ()
  {
  }
  virtual bool matches(const DNSQuestion* dq) const =0;
  virtual string toString() const = 0;
  mutable stat_t d_matches{0};
};

struct ServerPool
{
  ServerPool(): d_servers(std::make_shared<const ServerPolicy::NumberedServerVector>())
  {
  }

  ~ServerPool()
  {
  }

  const std::shared_ptr<DNSDistPacketCache> getCache() const { return packetCache; };

  bool getECS() const
  {
    return d_useECS;
  }

  void setECS(bool useECS)
  {
    d_useECS = useECS;
  }

  std::shared_ptr<DNSDistPacketCache> packetCache{nullptr};
  std::shared_ptr<ServerPolicy> policy{nullptr};

  size_t poolLoad();
  size_t countServers(bool upOnly);
  const std::shared_ptr<const ServerPolicy::NumberedServerVector> getServers();
  void addServer(shared_ptr<DownstreamState>& server);
  void removeServer(shared_ptr<DownstreamState>& server);

private:
  SharedLockGuarded<std::shared_ptr<const ServerPolicy::NumberedServerVector>> d_servers;
  bool d_useECS{false};
};

enum ednsHeaderFlags {
  EDNS_HEADER_FLAG_NONE = 0,
  EDNS_HEADER_FLAG_DO = 32768
};

struct DNSDistRuleAction
{
  std::shared_ptr<DNSRule> d_rule;
  std::shared_ptr<DNSAction> d_action;
  std::string d_name;
  boost::uuids::uuid d_id;
  uint64_t d_creationOrder;
};

struct DNSDistResponseRuleAction
{
  std::shared_ptr<DNSRule> d_rule;
  std::shared_ptr<DNSResponseAction> d_action;
  std::string d_name;
  boost::uuids::uuid d_id;
  uint64_t d_creationOrder;
};

extern GlobalStateHolder<SuffixMatchTree<DynBlock>> g_dynblockSMT;
extern DNSAction::Action g_dynBlockAction;

extern GlobalStateHolder<ServerPolicy> g_policy;
extern GlobalStateHolder<servers_t> g_dstates;
extern GlobalStateHolder<pools_t> g_pools;
extern GlobalStateHolder<vector<DNSDistRuleAction> > g_ruleactions;
extern GlobalStateHolder<vector<DNSDistResponseRuleAction> > g_respruleactions;
extern GlobalStateHolder<vector<DNSDistResponseRuleAction> > g_cachehitrespruleactions;
extern GlobalStateHolder<vector<DNSDistResponseRuleAction> > g_selfansweredrespruleactions;
extern GlobalStateHolder<vector<DNSDistResponseRuleAction> > g_cacheInsertedRespRuleActions;
extern GlobalStateHolder<NetmaskGroup> g_ACL;

extern ComboAddress g_serverControl; // not changed during runtime

extern std::vector<shared_ptr<TLSFrontend>> g_tlslocals;
extern std::vector<shared_ptr<DOHFrontend>> g_dohlocals;
extern std::vector<std::unique_ptr<ClientState>> g_frontends;
extern bool g_truncateTC;
extern bool g_fixupCase;
extern int g_tcpRecvTimeout;
extern int g_tcpSendTimeout;
extern uint16_t g_maxOutstanding;
extern std::atomic<bool> g_configurationDone;
extern boost::optional<uint64_t> g_maxTCPClientThreads;
extern uint64_t g_maxTCPQueuedConnections;
extern size_t g_maxTCPQueriesPerConn;
extern size_t g_maxTCPConnectionDuration;
extern size_t g_tcpInternalPipeBufferSize;
extern pdns::stat16_t g_cacheCleaningDelay;
extern pdns::stat16_t g_cacheCleaningPercentage;
extern uint32_t g_staleCacheEntriesTTL;
extern bool g_apiReadWrite;
extern std::string g_apiConfigDirectory;
extern bool g_servFailOnNoPolicy;
extern size_t g_udpVectorSize;
extern bool g_allowEmptyResponse;
extern uint32_t g_socketUDPSendBuffer;
extern uint32_t g_socketUDPRecvBuffer;

extern shared_ptr<BPFFilter> g_defaultBPFFilter;
extern std::vector<std::shared_ptr<DynBPFFilter> > g_dynBPFFilters;

struct LocalHolders
{
  LocalHolders(): acl(g_ACL.getLocal()), policy(g_policy.getLocal()), ruleactions(g_ruleactions.getLocal()), cacheHitRespRuleactions(g_cachehitrespruleactions.getLocal()), cacheInsertedRespRuleActions(g_cacheInsertedRespRuleActions.getLocal()), selfAnsweredRespRuleactions(g_selfansweredrespruleactions.getLocal()), servers(g_dstates.getLocal()), dynNMGBlock(g_dynblockNMG.getLocal()), dynSMTBlock(g_dynblockSMT.getLocal()), pools(g_pools.getLocal())
  {
  }

  LocalStateHolder<NetmaskGroup> acl;
  LocalStateHolder<ServerPolicy> policy;
  LocalStateHolder<vector<DNSDistRuleAction> > ruleactions;
  LocalStateHolder<vector<DNSDistResponseRuleAction> > cacheHitRespRuleactions;
  LocalStateHolder<vector<DNSDistResponseRuleAction> > cacheInsertedRespRuleActions;
  LocalStateHolder<vector<DNSDistResponseRuleAction> > selfAnsweredRespRuleactions;
  LocalStateHolder<servers_t> servers;
  LocalStateHolder<NetmaskTree<DynBlock, AddressAndPortRange> > dynNMGBlock;
  LocalStateHolder<SuffixMatchTree<DynBlock> > dynSMTBlock;
  LocalStateHolder<pools_t> pools;
};

void tcpAcceptorThread(std::vector<ClientState*> states);

#ifdef HAVE_DNS_OVER_HTTPS
void dohThread(ClientState* cs);
#endif /* HAVE_DNS_OVER_HTTPS */

void setLuaNoSideEffect(); // if nothing has been declared, set that there are no side effects
void setLuaSideEffect();   // set to report a side effect, cancelling all _no_ side effect calls
bool getLuaNoSideEffect(); // set if there were only explicit declarations of _no_ side effect
void resetLuaSideEffect(); // reset to indeterminate state

bool responseContentMatches(const PacketBuffer& response, const DNSName& qname, const uint16_t qtype, const uint16_t qclass, const std::shared_ptr<DownstreamState>& remote, unsigned int& qnameWireLength);

bool checkQueryHeaders(const struct dnsheader* dh, ClientState& cs);

extern std::vector<std::shared_ptr<DNSCryptContext>> g_dnsCryptLocals;
int handleDNSCryptQuery(PacketBuffer& packet, DNSCryptQuery& query, bool tcp, time_t now, PacketBuffer& response);
bool checkDNSCryptQuery(const ClientState& cs, PacketBuffer& query, std::unique_ptr<DNSCryptQuery>& dnsCryptQuery, time_t now, bool tcp);

#include "dnsdist-snmp.hh"

extern bool g_snmpEnabled;
extern bool g_snmpTrapsEnabled;
extern DNSDistSNMPAgent* g_snmpAgent;
extern bool g_addEDNSToSelfGeneratedResponses;

extern std::set<std::string> g_capabilitiesToRetain;
static const uint16_t s_udpIncomingBufferSize{1500}; // don't accept UDP queries larger than this value
static const size_t s_maxPacketCacheEntrySize{4096}; // don't cache responses larger than this value

enum class ProcessQueryResult : uint8_t { Drop, SendAnswer, PassToBackend, Asynchronous };
ProcessQueryResult processQuery(DNSQuestion& dq, LocalHolders& holders, std::shared_ptr<DownstreamState>& selectedBackend);
ProcessQueryResult processQueryAfterRules(DNSQuestion& dq, LocalHolders& holders, std::shared_ptr<DownstreamState>& selectedBackend);
bool processResponse(PacketBuffer& response, const std::vector<DNSDistResponseRuleAction>& respRuleActions, const std::vector<DNSDistResponseRuleAction>& insertedRespRuleActions, DNSResponse& dr, bool muted);
bool processRulesResult(const DNSAction::Action& action, DNSQuestion& dq, std::string& ruleresult, bool& drop);
bool processResponseAfterRules(PacketBuffer& response, const std::vector<DNSDistResponseRuleAction>& cacheInsertedRespRuleActions, DNSResponse& dr, bool muted);

bool assignOutgoingUDPQueryToBackend(std::shared_ptr<DownstreamState>& ds, uint16_t queryID, DNSQuestion& dq, PacketBuffer& query, ComboAddress& dest);

ssize_t udpClientSendRequestToBackend(const std::shared_ptr<DownstreamState>& ss, const int sd, const PacketBuffer& request, bool healthCheck = false);
bool sendUDPResponse(int origFD, const PacketBuffer& response, const int delayMsec, const ComboAddress& origDest, const ComboAddress& origRemote);
void handleResponseSent(const DNSName& qname, const QType& qtype, double udiff, const ComboAddress& client, const ComboAddress& backend, unsigned int size, const dnsheader& cleartextDH, dnsdist::Protocol outgoingProtocol, dnsdist::Protocol incomingProtocol, bool fromBackend);
void handleResponseSent(const InternalQueryState& ids, double udiff, const ComboAddress& client, const ComboAddress& backend, unsigned int size, const dnsheader& cleartextDH, dnsdist::Protocol outgoingProtocol, bool fromBackend);
