text: // Copyright (c) 2009-2020 The Bitcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_NETADDRESS_H
  #define BITCOIN_NETADDRESS_H
  
  #if defined(HAVE_CONFIG_H)
  #include <config/bitcoin-config.h>
  #endif
  
  #include <attributes.h>
  #include <compat.h>
  #include <crypto/siphash.h>
  #include <prevector.h>
  #include <random.h>
  #include <serialize.h>
  #include <tinyformat.h>
  #include <util/strencodings.h>
  #include <util/string.h>
  
  #include <array>
  #include <cstdint>
  #include <ios>
  #include <string>
  #include <vector>
  
  /**
   * A flag that is ORed into the protocol version to designate that addresses
   * should be serialized in (unserialized from) v2 format (BIP155).
   * Make sure that this does not collide with any of the values in `version.h`
   * or with `SERIALIZE_TRANSACTION_NO_WITNESS`.
   */
  static constexpr int ADDRV2_FORMAT = 0x20000000;
  
  /**
   * A network type.
   * @note An address may belong to more than one network, for example `10.0.0.1`
   * belongs to both `NET_UNROUTABLE` and `NET_IPV4`.
   * Keep these sequential starting from 0 and `NET_MAX` as the last entry.
   * We have loops like `for (int i = 0; i < NET_MAX; ++i)` that expect to iterate
   * over all enum values and also `GetExtNetwork()` "extends" this enum by
   * introducing standalone constants starting from `NET_MAX`.
   */
  enum Network {
      /// Addresses from these networks are not publicly routable on the global Internet.
      NET_UNROUTABLE = 0,
  
      /// IPv4
      NET_IPV4,
  
      /// IPv6
      NET_IPV6,
  
      /// TOR (v2 or v3)
      NET_ONION,
  
      /// I2P
      NET_I2P,
  
      /// CJDNS
      NET_CJDNS,
  
      /// A set of addresses that represent the hash of a string or FQDN. We use
      /// them in AddrMan to keep track of which DNS seeds were used.
      NET_INTERNAL,
  
      /// Dummy value to indicate the number of NET_* constants.
      NET_MAX,
  };
  
  /// Prefix of an IPv6 address when it contains an embedded IPv4 address.
  /// Used when (un)serializing addresses in ADDRv1 format (pre-BIP155).
  static const std::array<uint8_t, 12> IPV4_IN_IPV6_PREFIX{
      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF};
  
  /// Prefix of an IPv6 address when it contains an embedded TORv2 address.
  /// Used when (un)serializing addresses in ADDRv1 format (pre-BIP155).
  /// Such dummy IPv6 addresses are guaranteed to not be publicly routable as they
  /// fall under RFC4193's fc00::/7 subnet allocated to unique-local addresses.
  static const std::array<uint8_t, 6> TORV2_IN_IPV6_PREFIX{
      0xFD, 0x87, 0xD8, 0x7E, 0xEB, 0x43};
  
  /// Prefix of an IPv6 address when it contains an embedded "internal" address.
  /// Used when (un)serializing addresses in ADDRv1 format (pre-BIP155).
  /// The prefix comes from 0xFD + SHA256("bitcoin")[0:5].
  /// Such dummy IPv6 addresses are guaranteed to not be publicly routable as they
  /// fall under RFC4193's fc00::/7 subnet allocated to unique-local addresses.
  static const std::array<uint8_t, 6> INTERNAL_IN_IPV6_PREFIX{
      0xFD, 0x6B, 0x88, 0xC0, 0x87, 0x24 // 0xFD + sha256("bitcoin")[0:5].
  };
  
  /// Size of IPv4 address (in bytes).
  static constexpr size_t ADDR_IPV4_SIZE = 4;
  
  /// Size of IPv6 address (in bytes).
  static constexpr size_t ADDR_IPV6_SIZE = 16;
  
  /// Size of TORv3 address (in bytes). This is the length of just the address
  /// as used in BIP155, without the checksum and the version byte.
  static constexpr size_t ADDR_TORV3_SIZE = 32;
  
  /// Size of I2P address (in bytes).
  static constexpr size_t ADDR_I2P_SIZE = 32;
  
  /// Size of CJDNS address (in bytes).
  static constexpr size_t ADDR_CJDNS_SIZE = 16;
  
  /// Size of "internal" (NET_INTERNAL) address (in bytes).
  static constexpr size_t ADDR_INTERNAL_SIZE = 10;
  
  /// SAM 3.1 and earlier do not support specifying ports and force the port to 0.
  static constexpr uint16_t I2P_SAM31_PORT{0};
  
  /**
   * Network address.
   */
  class CNetAddr
  {
  protected:
      /**
       * Raw representation of the network address.
       * In network byte order (big endian) for IPv4 and IPv6.
       */
      prevector<ADDR_IPV6_SIZE, uint8_t> m_addr{ADDR_IPV6_SIZE, 0x0};
  
      /**
       * Network to which this address belongs.
       */
      Network m_net{NET_IPV6};
  
      /**
       * Scope id if scoped/link-local IPV6 address.
       * See https://tools.ietf.org/html/rfc4007
       */
      uint32_t m_scope_id{0};
  
  public:
      CNetAddr();
      explicit CNetAddr(const struct in_addr& ipv4Addr);
      void SetIP(const CNetAddr& ip);
  
      /**
       * Set from a legacy IPv6 address.
       * Legacy IPv6 address may be a normal IPv6 address, or another address
       * (e.g. IPv4) disguised as IPv6. This encoding is used in the legacy
       * `addr` encoding.
       */
      void SetLegacyIPv6(Span<const uint8_t> ipv6);
  
      bool SetInternal(const std::string& name);
  
      /**
       * Parse a Tor or I2P address and set this object to it.
       * @param[in] addr Address to parse, for example
       * pg6mmjiyjmcrsslvykfwnntlaru7p5svn6y2ymmju6nubxndf4pscryd.onion or
       * ukeu3k5oycgaauneqgtnvselmt4yemvoilkln7jpvamvfx7dnkdq.b32.i2p.
       * @returns Whether the operation was successful.
       * @see CNetAddr::IsTor(), CNetAddr::IsI2P()
       */
      bool SetSpecial(const std::string& addr);
  
      bool IsBindAny() const; // INADDR_ANY equivalent
      bool IsIPv4() const;    // IPv4 mapped address (::FFFF:0:0/96, 0.0.0.0/0)
      bool IsIPv6() const;    // IPv6 address (not mapped IPv4, not Tor)
      bool IsRFC1918() const; // IPv4 private networks (10.0.0.0/8, 192.168.0.0/16, 172.16.0.0/12)
      bool IsRFC2544() const; // IPv4 inter-network communications (198.18.0.0/15)
      bool IsRFC6598() const; // IPv4 ISP-level NAT (100.64.0.0/10)
      bool IsRFC5737() const; // IPv4 documentation addresses (192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24)
      bool IsRFC3849() const; // IPv6 documentation address (2001:0DB8::/32)
      bool IsRFC3927() const; // IPv4 autoconfig (169.254.0.0/16)
      bool IsRFC3964() const; // IPv6 6to4 tunnelling (2002::/16)
      bool IsRFC4193() const; // IPv6 unique local (FC00::/7)
      bool IsRFC4380() const; // IPv6 Teredo tunnelling (2001::/32)
      bool IsRFC4843() const; // IPv6 ORCHID (deprecated) (2001:10::/28)
      bool IsRFC7343() const; // IPv6 ORCHIDv2 (2001:20::/28)
      bool IsRFC4862() const; // IPv6 autoconfig (FE80::/64)
      bool IsRFC6052() const; // IPv6 well-known prefix for IPv4-embedded address (64:FF9B::/96)
      bool IsRFC6145() const; // IPv6 IPv4-translated address (::FFFF:0:0:0/96) (actually defined in RFC2765)
      bool IsHeNet() const;   // IPv6 Hurricane Electric - https://he.net (2001:0470::/36)
      bool IsTor() const;
      bool IsI2P() const;
      bool IsCJDNS() const;
      bool IsLocal() const;
      bool IsRoutable() const;
      bool IsInternal() const;
      bool IsValid() const;
  
      /**
       * Check if the current object can be serialized in pre-ADDRv2/BIP155 format.
       */
      bool IsAddrV1Compatible() const;
  
      enum Network GetNetwork() const;
      std::string ToString() const;
      std::string ToStringIP() const;
      uint64_t GetHash() const;
      bool GetInAddr(struct in_addr* pipv4Addr) const;
      Network GetNetClass() const;
  
      //! For IPv4, mapped IPv4, SIIT translated IPv4, Teredo, 6to4 tunneled addresses, return the relevant IPv4 address as a uint32.
      uint32_t GetLinkedIPv4() const;
      //! Whether this address has a linked IPv4 address (see GetLinkedIPv4()).
      bool HasLinkedIPv4() const;
  
      // The AS on the BGP path to the node we use to diversify
      // peers in AddrMan bucketing based on the AS infrastructure.
      // The ip->AS mapping depends on how asmap is constructed.
      uint32_t GetMappedAS(const std::vector<bool>& asmap) const;
  
      std::vector<unsigned char> GetGroup(const std::vector<bool>& asmap) const;
      std::vector<unsigned char> GetAddrBytes() const;
      int GetReachabilityFrom(const CNetAddr* paddrPartner = nullptr) const;
  
      explicit CNetAddr(const struct in6_addr& pipv6Addr, const uint32_t scope = 0);
      bool GetIn6Addr(struct in6_addr* pipv6Addr) const;
  
      friend bool operator==(const CNetAddr& a, const CNetAddr& b);
      friend bool operator!=(const CNetAddr& a, const CNetAddr& b) { return !(a == b); }
      friend bool operator<(const CNetAddr& a, const CNetAddr& b);
  
      /**
       * Whether this address should be relayed to other peers even if we can't reach it ourselves.
       */
      bool IsRelayable() const
      {
          return IsIPv4() || IsIPv6() || IsTor() || IsI2P();
      }
  
      /**
       * Serialize to a stream.
       */
      template <typename Stream>
      void Serialize(Stream& s) const
      {
          if (s.GetVersion() & ADDRV2_FORMAT) {
              SerializeV2Stream(s);
          } else {
              SerializeV1Stream(s);
          }
      }
  
      /**
       * Unserialize from a stream.
       */
      template <typename Stream>
      void Unserialize(Stream& s)
      {
          if (s.GetVersion() & ADDRV2_FORMAT) {
              UnserializeV2Stream(s);
          } else {
              UnserializeV1Stream(s);
          }
      }
  
      friend class CNetAddrHash;
      friend class CSubNet;
  
  private:
      /**
       * Parse a Tor address and set this object to it.
       * @param[in] addr Address to parse, must be a valid C string, for example
       * pg6mmjiyjmcrsslvykfwnntlaru7p5svn6y2ymmju6nubxndf4pscryd.onion.
       * @returns Whether the operation was successful.
       * @see CNetAddr::IsTor()
       */
      bool SetTor(const std::string& addr);
  
      /**
       * Parse an I2P address and set this object to it.
       * @param[in] addr Address to parse, must be a valid C string, for example
       * ukeu3k5oycgaauneqgtnvselmt4yemvoilkln7jpvamvfx7dnkdq.b32.i2p.
       * @returns Whether the operation was successful.
       * @see CNetAddr::IsI2P()
       */
      bool SetI2P(const std::string& addr);
  
      /**
       * BIP155 network ids recognized by this software.
       */
      enum BIP155Network : uint8_t {
          IPV4 = 1,
          IPV6 = 2,
          TORV2 = 3,
          TORV3 = 4,
          I2P = 5,
          CJDNS = 6,
      };
  
      /**
       * Size of CNetAddr when serialized as ADDRv1 (pre-BIP155) (in bytes).
       */
      static constexpr size_t V1_SERIALIZATION_SIZE = ADDR_IPV6_SIZE;
  
      /**
       * Maximum size of an address as defined in BIP155 (in bytes).
       * This is only the size of the address, not the entire CNetAddr object
       * when serialized.
       */
      static constexpr size_t MAX_ADDRV2_SIZE = 512;
  
      /**
       * Get the BIP155 network id of this address.
       * Must not be called for IsInternal() objects.
       * @returns BIP155 network id, except TORV2 which is no longer supported.
       */
      BIP155Network GetBIP155Network() const;
  
      /**
       * Set `m_net` from the provided BIP155 network id and size after validation.
       * @retval true the network was recognized, is valid and `m_net` was set
       * @retval false not recognised (from future?) and should be silently ignored
       * @throws std::ios_base::failure if the network is one of the BIP155 founding
       * networks (id 1..6) with wrong address size.
       */
      bool SetNetFromBIP155Network(uint8_t possible_bip155_net, size_t address_size);
  
      /**
       * Serialize in pre-ADDRv2/BIP155 format to an array.
       */
      void SerializeV1Array(uint8_t (&arr)[V1_SERIALIZATION_SIZE]) const
      {
          size_t prefix_size;
  
          switch (m_net) {
          case NET_IPV6:
              assert(m_addr.size() == sizeof(arr));
              memcpy(arr, m_addr.data(), m_addr.size());
              return;
          case NET_IPV4:
              prefix_size = sizeof(IPV4_IN_IPV6_PREFIX);
              assert(prefix_size + m_addr.size() == sizeof(arr));
              memcpy(arr, IPV4_IN_IPV6_PREFIX.data(), prefix_size);
              memcpy(arr + prefix_size, m_addr.data(), m_addr.size());
              return;
          case NET_INTERNAL:
              prefix_size = sizeof(INTERNAL_IN_IPV6_PREFIX);
              assert(prefix_size + m_addr.size() == sizeof(arr));
              memcpy(arr, INTERNAL_IN_IPV6_PREFIX.data(), prefix_size);
              memcpy(arr + prefix_size, m_addr.data(), m_addr.size());
              return;
          case NET_ONION:
          case NET_I2P:
          case NET_CJDNS:
              break;
          case NET_UNROUTABLE:
          case NET_MAX:
              assert(false);
          } // no default case, so the compiler can warn about missing cases
  
          // Serialize ONION, I2P and CJDNS as all-zeros.
          memset(arr, 0x0, V1_SERIALIZATION_SIZE);
      }
  
      /**
       * Serialize in pre-ADDRv2/BIP155 format to a stream.
       */
      template <typename Stream>
      void SerializeV1Stream(Stream& s) const
      {
          uint8_t serialized[V1_SERIALIZATION_SIZE];
  
          SerializeV1Array(serialized);
  
          s << serialized;
      }
  
      /**
       * Serialize as ADDRv2 / BIP155.
       */
      template <typename Stream>
      void SerializeV2Stream(Stream& s) const
      {
          if (IsInternal()) {
              // Serialize NET_INTERNAL as embedded in IPv6. We need to
              // serialize such addresses from addrman.
              s << static_cast<uint8_t>(BIP155Network::IPV6);
              s << COMPACTSIZE(ADDR_IPV6_SIZE);
              SerializeV1Stream(s);
              return;
          }
  
          s << static_cast<uint8_t>(GetBIP155Network());
          s << m_addr;
      }
  
      /**
       * Unserialize from a pre-ADDRv2/BIP155 format from an array.
       */
      void UnserializeV1Array(uint8_t (&arr)[V1_SERIALIZATION_SIZE])
      {
          // Use SetLegacyIPv6() so that m_net is set correctly. For example
          // ::FFFF:0102:0304 should be set as m_net=NET_IPV4 (1.2.3.4).
          SetLegacyIPv6(arr);
      }
  
      /**
       * Unserialize from a pre-ADDRv2/BIP155 format from a stream.
       */
      template <typename Stream>
      void UnserializeV1Stream(Stream& s)
      {
          uint8_t serialized[V1_SERIALIZATION_SIZE];
  
          s >> serialized;
  
          UnserializeV1Array(serialized);
      }
  
      /**
       * Unserialize from a ADDRv2 / BIP155 format.
       */
      template <typename Stream>
      void UnserializeV2Stream(Stream& s)
      {
          uint8_t bip155_net;
          s >> bip155_net;
  
          size_t address_size;
          s >> COMPACTSIZE(address_size);
  
          if (address_size > MAX_ADDRV2_SIZE) {
              throw std::ios_base::failure(strprintf(
                  "Address too long: %u > %u", address_size, MAX_ADDRV2_SIZE));
          }
  
          m_scope_id = 0;
  
          if (SetNetFromBIP155Network(bip155_net, address_size)) {
              m_addr.resize(address_size);
              s >> MakeSpan(m_addr);
  
              if (m_net != NET_IPV6) {
                  return;
              }
  
              // Do some special checks on IPv6 addresses.
  
              // Recognize NET_INTERNAL embedded in IPv6, such addresses are not
              // gossiped but could be coming from addrman, when unserializing from
              // disk.
              if (HasPrefix(m_addr, INTERNAL_IN_IPV6_PREFIX)) {
                  m_net = NET_INTERNAL;
                  memmove(m_addr.data(), m_addr.data() + INTERNAL_IN_IPV6_PREFIX.size(),
                          ADDR_INTERNAL_SIZE);
                  m_addr.resize(ADDR_INTERNAL_SIZE);
                  return;
              }
  
              if (!HasPrefix(m_addr, IPV4_IN_IPV6_PREFIX) &&
                  !HasPrefix(m_addr, TORV2_IN_IPV6_PREFIX)) {
                  return;
              }
  
              // IPv4 and TORv2 are not supposed to be embedded in IPv6 (like in V1
              // encoding). Unserialize as !IsValid(), thus ignoring them.
          } else {
              // If we receive an unknown BIP155 network id (from the future?) then
              // ignore the address - unserialize as !IsValid().
              s.ignore(address_size);
          }
  
          // Mimic a default-constructed CNetAddr object which is !IsValid() and thus
          // will not be gossiped, but continue reading next addresses from the stream.
          m_net = NET_IPV6;
          m_addr.assign(ADDR_IPV6_SIZE, 0x0);
      }
  };
  
  class CNetAddrHash
  {
  public:
      size_t operator()(const CNetAddr& a) const noexcept
      {
          CSipHasher hasher(m_salt_k0, m_salt_k1);
          hasher.Write(a.m_net);
          hasher.Write(a.m_addr.data(), a.m_addr.size());
          return static_cast<size_t>(hasher.Finalize());
      }
  
  private:
      const uint64_t m_salt_k0 = GetRand(std::numeric_limits<uint64_t>::max());
      const uint64_t m_salt_k1 = GetRand(std::numeric_limits<uint64_t>::max());
  };
  
  class CSubNet
  {
  protected:
      /// Network (base) address
      CNetAddr network;
      /// Netmask, in network byte order
      uint8_t netmask[16];
      /// Is this value valid? (only used to signal parse errors)
      bool valid;
  
      bool SanityCheck() const;
  
  public:
      /**
       * Construct an invalid subnet (empty, `Match()` always returns false).
       */
      CSubNet();
  
      /**
       * Construct from a given network start and number of bits (CIDR mask).
       * @param[in] addr Network start. Must be IPv4 or IPv6, otherwise an invalid subnet is
       * created.
       * @param[in] mask CIDR mask, must be in [0, 32] for IPv4 addresses and in [0, 128] for
       * IPv6 addresses. Otherwise an invalid subnet is created.
       */
      CSubNet(const CNetAddr& addr, uint8_t mask);
  
      /**
       * Construct from a given network start and mask.
       * @param[in] addr Network start. Must be IPv4 or IPv6, otherwise an invalid subnet is
       * created.
       * @param[in] mask Network mask, must be of the same type as `addr` and not contain 0-bits
       * followed by 1-bits. Otherwise an invalid subnet is created.
       */
      CSubNet(const CNetAddr& addr, const CNetAddr& mask);
  
      /**
       * Construct a single-host subnet.
       * @param[in] addr The sole address to be contained in the subnet, can also be non-IPv[46].
       */
      explicit CSubNet(const CNetAddr& addr);
  
      bool Match(const CNetAddr& addr) const;
  
      std::string ToString() const;
      bool IsValid() const;
  
      friend bool operator==(const CSubNet& a, const CSubNet& b);
      friend bool operator!=(const CSubNet& a, const CSubNet& b) { return !(a == b); }
      friend bool operator<(const CSubNet& a, const CSubNet& b);
  };
  
  /** A combination of a network address (CNetAddr) and a (TCP) port */
  class CService : public CNetAddr
  {
  protected:
      uint16_t port; // host order
  
  public:
      CService();
      CService(const CNetAddr& ip, uint16_t port);
      CService(const struct in_addr& ipv4Addr, uint16_t port);
      explicit CService(const struct sockaddr_in& addr);
      uint16_t GetPort() const;
      bool GetSockAddr(struct sockaddr* paddr, socklen_t* addrlen) const;
      bool SetSockAddr(const struct sockaddr* paddr);
      friend bool operator==(const CService& a, const CService& b);
      friend bool operator!=(const CService& a, const CService& b) { return !(a == b); }
      friend bool operator<(const CService& a, const CService& b);
      std::vector<unsigned char> GetKey() const;
      std::string ToString() const;
      std::string ToStringPort() const;
      std::string ToStringIPPort() const;
  
      CService(const struct in6_addr& ipv6Addr, uint16_t port);
      explicit CService(const struct sockaddr_in6& addr);
  
      SERIALIZE_METHODS(CService, obj)
      {
          READWRITEAS(CNetAddr, obj);
          READWRITE(Using<BigEndianFormatter<2>>(obj.port));
      }
  };
  
  #endif // BITCOIN_NETADDRESS_H
  