dash/src/netaddress.cpp

// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2015 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#include <netaddress.h>
#include <netbase.h>
#include <crypto/common.h>
#include <crypto/sha3.h>
#include <hash.h>
#include <prevector.h>
#include <tinyformat.h>
#include <util/asmap.h>
#include <util/strencodings.h>
#include <util/string.h>

#include <algorithm>
#include <array>
#include <cstdint>
#include <ios>
#include <iterator>
#include <tuple>

constexpr size_t CNetAddr::V1_SERIALIZATION_SIZE;
constexpr size_t CNetAddr::MAX_ADDRV2_SIZE;

CNetAddr::BIP155Network CNetAddr::GetBIP155Network() const
{
    switch (m_net) {
    case NET_IPV4:
        return BIP155Network::IPV4;
    case NET_IPV6:
        return BIP155Network::IPV6;
    case NET_ONION:
        switch (m_addr.size()) {
        case ADDR_TORV2_SIZE:
            return BIP155Network::TORV2;
        case ADDR_TORV3_SIZE:
            return BIP155Network::TORV3;
        default:
            assert(false);
        }
    case NET_I2P:
        return BIP155Network::I2P;
    case NET_CJDNS:
        return BIP155Network::CJDNS;
    case NET_INTERNAL:   // should have been handled before calling this function
    case NET_UNROUTABLE: // m_net is never and should not be set to NET_UNROUTABLE
    case NET_MAX:        // m_net is never and should not be set to NET_MAX
        assert(false);
    } // no default case, so the compiler can warn about missing cases

    assert(false);
}

bool CNetAddr::SetNetFromBIP155Network(uint8_t possible_bip155_net, size_t address_size)
{
    switch (possible_bip155_net) {
    case BIP155Network::IPV4:
        if (address_size == ADDR_IPV4_SIZE) {
            m_net = NET_IPV4;
            return true;
        }
        throw std::ios_base::failure(
            strprintf("BIP155 IPv4 address with length %u (should be %u)", address_size,
                      ADDR_IPV4_SIZE));
    case BIP155Network::IPV6:
        if (address_size == ADDR_IPV6_SIZE) {
            m_net = NET_IPV6;
            return true;
        }
        throw std::ios_base::failure(
            strprintf("BIP155 IPv6 address with length %u (should be %u)", address_size,
                      ADDR_IPV6_SIZE));
    case BIP155Network::TORV2:
        if (address_size == ADDR_TORV2_SIZE) {
            m_net = NET_ONION;
            return true;
        }
        throw std::ios_base::failure(
            strprintf("BIP155 TORv2 address with length %u (should be %u)", address_size,
                      ADDR_TORV2_SIZE));
    case BIP155Network::TORV3:
        if (address_size == ADDR_TORV3_SIZE) {
            m_net = NET_ONION;
            return true;
        }
        throw std::ios_base::failure(
            strprintf("BIP155 TORv3 address with length %u (should be %u)", address_size,
                      ADDR_TORV3_SIZE));
    case BIP155Network::I2P:
        if (address_size == ADDR_I2P_SIZE) {
            m_net = NET_I2P;
            return true;
        }
        throw std::ios_base::failure(
            strprintf("BIP155 I2P address with length %u (should be %u)", address_size,
                      ADDR_I2P_SIZE));
    case BIP155Network::CJDNS:
        if (address_size == ADDR_CJDNS_SIZE) {
            m_net = NET_CJDNS;
            return true;
        }
        throw std::ios_base::failure(
            strprintf("BIP155 CJDNS address with length %u (should be %u)", address_size,
                      ADDR_CJDNS_SIZE));
    }

    // Don't throw on addresses with unknown network ids (maybe from the future).
    // Instead silently drop them and have the unserialization code consume
    // subsequent ones which may be known to us.
    return false;
}

bool fAllowPrivateNet = DEFAULT_ALLOWPRIVATENET;

/**
 * Construct an unspecified IPv6 network address (::/128).
 *
 * @note This address is considered invalid by CNetAddr::IsValid()
 */
CNetAddr::CNetAddr() {}

void CNetAddr::SetIP(const CNetAddr& ipIn)
{
    // Size check.
    switch (ipIn.m_net) {
    case NET_IPV4:
        assert(ipIn.m_addr.size() == ADDR_IPV4_SIZE);
        break;
    case NET_IPV6:
        assert(ipIn.m_addr.size() == ADDR_IPV6_SIZE);
        break;
    case NET_ONION:
        assert(ipIn.m_addr.size() == ADDR_TORV2_SIZE || ipIn.m_addr.size() == ADDR_TORV3_SIZE);
        break;
    case NET_I2P:
        assert(ipIn.m_addr.size() == ADDR_I2P_SIZE);
        break;
    case NET_CJDNS:
        assert(ipIn.m_addr.size() == ADDR_CJDNS_SIZE);
        break;
    case NET_INTERNAL:
        assert(ipIn.m_addr.size() == ADDR_INTERNAL_SIZE);
        break;
    case NET_UNROUTABLE:
    case NET_MAX:
        assert(false);
    } // no default case, so the compiler can warn about missing cases

    m_net = ipIn.m_net;
    m_addr = ipIn.m_addr;
}

void CNetAddr::SetLegacyIPv6(Span<const uint8_t> ipv6)
{
    assert(ipv6.size() == ADDR_IPV6_SIZE);

    size_t skip{0};

    if (HasPrefix(ipv6, IPV4_IN_IPV6_PREFIX)) {
        // IPv4-in-IPv6
        m_net = NET_IPV4;
        skip = sizeof(IPV4_IN_IPV6_PREFIX);
    } else if (HasPrefix(ipv6, TORV2_IN_IPV6_PREFIX)) {
        // TORv2-in-IPv6
        m_net = NET_ONION;
        skip = sizeof(TORV2_IN_IPV6_PREFIX);
    } else if (HasPrefix(ipv6, INTERNAL_IN_IPV6_PREFIX)) {
        // Internal-in-IPv6
        m_net = NET_INTERNAL;
        skip = sizeof(INTERNAL_IN_IPV6_PREFIX);
    } else {
        // IPv6
        m_net = NET_IPV6;
    }

    m_addr.assign(ipv6.begin() + skip, ipv6.end());
}

/**
 * Create an "internal" address that represents a name or FQDN. CAddrMan uses
 * these fake addresses to keep track of which DNS seeds were used.
 * @returns Whether or not the operation was successful.
 * @see NET_INTERNAL, INTERNAL_IN_IPV6_PREFIX, CNetAddr::IsInternal(), CNetAddr::IsRFC4193()
 */
bool CNetAddr::SetInternal(const std::string &name)
{
    if (name.empty()) {
        return false;
    }
    m_net = NET_INTERNAL;
    unsigned char hash[32] = {};
    CSHA256().Write((const unsigned char*)name.data(), name.size()).Finalize(hash);
    m_addr.assign(hash, hash + ADDR_INTERNAL_SIZE);
    return true;
}

namespace torv3 {
// https://gitweb.torproject.org/torspec.git/tree/rend-spec-v3.txt#n2135
static constexpr size_t CHECKSUM_LEN = 2;
static const unsigned char VERSION[] = {3};
static constexpr size_t TOTAL_LEN = ADDR_TORV3_SIZE + CHECKSUM_LEN + sizeof(VERSION);

static void Checksum(Span<const uint8_t> addr_pubkey, uint8_t (&checksum)[CHECKSUM_LEN])
{
    // TORv3 CHECKSUM = H(".onion checksum" | PUBKEY | VERSION)[:2]
    static const unsigned char prefix[] = ".onion checksum";
    static constexpr size_t prefix_len = 15;

    SHA3_256 hasher;

    hasher.Write(MakeSpan(prefix).first(prefix_len));
    hasher.Write(addr_pubkey);
    hasher.Write(VERSION);

    uint8_t checksum_full[SHA3_256::OUTPUT_SIZE];

    hasher.Finalize(checksum_full);

    memcpy(checksum, checksum_full, sizeof(checksum));
}

}; // namespace torv3

/**
 * Parse a TOR address and set this object to it.
 *
 * @returns Whether or not the operation was successful.
 *
 * @see CNetAddr::IsTor()
 */
bool CNetAddr::SetSpecial(const std::string& str)
{
    static const char* suffix{".onion"};
    static constexpr size_t suffix_len{6};

    if (!ValidAsCString(str) || str.size() <= suffix_len ||
        str.substr(str.size() - suffix_len) != suffix) {
        return false;
    }

    bool invalid;
    const auto& input = DecodeBase32(str.substr(0, str.size() - suffix_len).c_str(), &invalid);

    if (invalid) {
        return false;
    }

    switch (input.size()) {
    case ADDR_TORV2_SIZE:
        m_net = NET_ONION;
        m_addr.assign(input.begin(), input.end());
        return true;
    case torv3::TOTAL_LEN: {
        Span<const uint8_t> input_pubkey{input.data(), ADDR_TORV3_SIZE};
        Span<const uint8_t> input_checksum{input.data() + ADDR_TORV3_SIZE, torv3::CHECKSUM_LEN};
        Span<const uint8_t> input_version{input.data() + ADDR_TORV3_SIZE + torv3::CHECKSUM_LEN, sizeof(torv3::VERSION)};

        if (input_version != torv3::VERSION) {
            return false;
        }

        uint8_t calculated_checksum[torv3::CHECKSUM_LEN];
        torv3::Checksum(input_pubkey, calculated_checksum);

        if (input_checksum != calculated_checksum) {
            return false;
        }

        m_net = NET_ONION;
        m_addr.assign(input_pubkey.begin(), input_pubkey.end());
        return true;
    }
    }

    return false;
}

CNetAddr::CNetAddr(const struct in_addr& ipv4Addr)
{
    m_net = NET_IPV4;
    const uint8_t* ptr = reinterpret_cast<const uint8_t*>(&ipv4Addr);
    m_addr.assign(ptr, ptr + ADDR_IPV4_SIZE);
}

CNetAddr::CNetAddr(const struct in6_addr& ipv6Addr, const uint32_t scope)
{
    SetLegacyIPv6(Span<const uint8_t>(reinterpret_cast<const uint8_t*>(&ipv6Addr), sizeof(ipv6Addr)));
    scopeId = scope;
}

bool CNetAddr::IsBindAny() const
{
    if (!IsIPv4() && !IsIPv6()) {
        return false;
    }
    return std::all_of(m_addr.begin(), m_addr.end(), [](uint8_t b) { return b == 0; });
}

bool CNetAddr::IsIPv4() const { return m_net == NET_IPV4; }

bool CNetAddr::IsIPv6() const { return m_net == NET_IPV6; }

bool CNetAddr::IsRFC1918() const
{
    return IsIPv4() && (
        m_addr[0] == 10 ||
        (m_addr[0] == 192 && m_addr[1] == 168) ||
        (m_addr[0] == 172 && m_addr[1] >= 16 && m_addr[1] <= 31));
}

bool CNetAddr::IsRFC2544() const
{
    return IsIPv4() && m_addr[0] == 198 && (m_addr[1] == 18 || m_addr[1] == 19);
}

bool CNetAddr::IsRFC3927() const
{
    return IsIPv4() && HasPrefix(m_addr, std::array<uint8_t, 2>{169, 254});
}

bool CNetAddr::IsRFC6598() const
{
    return IsIPv4() && m_addr[0] == 100 && m_addr[1] >= 64 && m_addr[1] <= 127;
}

bool CNetAddr::IsRFC5737() const
{
    return IsIPv4() && (HasPrefix(m_addr, std::array<uint8_t, 3>{192, 0, 2}) ||
                        HasPrefix(m_addr, std::array<uint8_t, 3>{198, 51, 100}) ||
                        HasPrefix(m_addr, std::array<uint8_t, 3>{203, 0, 113}));
}

bool CNetAddr::IsRFC3849() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 4>{0x20, 0x01, 0x0D, 0xB8});
}

bool CNetAddr::IsRFC3964() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 2>{0x20, 0x02});
}

bool CNetAddr::IsRFC6052() const
{
    return IsIPv6() &&
           HasPrefix(m_addr, std::array<uint8_t, 12>{0x00, 0x64, 0xFF, 0x9B, 0x00, 0x00,
                                                     0x00, 0x00, 0x00, 0x00, 0x00, 0x00});
}

bool CNetAddr::IsRFC4380() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 4>{0x20, 0x01, 0x00, 0x00});
}

bool CNetAddr::IsRFC4862() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 8>{0xFE, 0x80, 0x00, 0x00,
                                                                0x00, 0x00, 0x00, 0x00});
}

bool CNetAddr::IsRFC4193() const
{
    return IsIPv6() && (m_addr[0] & 0xFE) == 0xFC;
}

bool CNetAddr::IsRFC6145() const
{
    return IsIPv6() &&
           HasPrefix(m_addr, std::array<uint8_t, 12>{0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
                                                     0x00, 0x00, 0xFF, 0xFF, 0x00, 0x00});
}

bool CNetAddr::IsRFC4843() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 3>{0x20, 0x01, 0x00}) &&
           (m_addr[3] & 0xF0) == 0x10;
}

bool CNetAddr::IsRFC7343() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 3>{0x20, 0x01, 0x00}) &&
           (m_addr[3] & 0xF0) == 0x20;
}

bool CNetAddr::IsHeNet() const
{
    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 4>{0x20, 0x01, 0x04, 0x70});
}

/**
 * Check whether this object represents a TOR address.
 * @see CNetAddr::SetSpecial(const std::string &)
 */
bool CNetAddr::IsTor() const { return m_net == NET_ONION; }

/**
 * Check whether this object represents an I2P address.
 */
bool CNetAddr::IsI2P() const { return m_net == NET_I2P; }

/**
 * Check whether this object represents a CJDNS address.
 */
bool CNetAddr::IsCJDNS() const { return m_net == NET_CJDNS; }

bool CNetAddr::IsLocal() const
{
    // IPv4 loopback (127.0.0.0/8 or 0.0.0.0/8)
    if (IsIPv4() && (m_addr[0] == 127 || m_addr[0] == 0)) {
        return true;
    }

    // IPv6 loopback (::1/128)
    static const unsigned char pchLocal[16] = {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1};
    if (IsIPv6() && memcmp(m_addr.data(), pchLocal, sizeof(pchLocal)) == 0) {
        return true;
    }

    return false;
}

bool CNetAddr::IsValid() const
{
    // unspecified IPv6 address (::/128)
    unsigned char ipNone6[16] = {};
    if (IsIPv6() && memcmp(m_addr.data(), ipNone6, sizeof(ipNone6)) == 0) {
        return false;
    }

    // CJDNS addresses always start with 0xfc
    if (IsCJDNS() && (m_addr[0] != 0xFC)) {
        return false;
    }

    // documentation IPv6 address
    if (IsRFC3849())
        return false;

    if (IsInternal())
        return false;

    if (IsIPv4()) {
        const uint32_t addr = ReadBE32(m_addr.data());
        if (addr == INADDR_ANY || addr == INADDR_NONE) {
            return false;
        }
    }

    return true;
}

bool CNetAddr::IsRoutable() const
{
    if (!IsValid())
        return false;
    if (!fAllowPrivateNet && IsRFC1918())
        return false;
    return !(IsRFC2544() || IsRFC3927() || IsRFC4862() || IsRFC6598() || IsRFC5737() || (IsRFC4193() && !IsTor()) || IsRFC4843() || IsRFC7343() || IsLocal() || IsInternal());
}

/**
 * @returns Whether or not this is a dummy address that represents a name.
 *
 * @see CNetAddr::SetInternal(const std::string &)
 */
bool CNetAddr::IsInternal() const
{
   return m_net == NET_INTERNAL;
}

bool CNetAddr::IsAddrV1Compatible() const
{
    switch (m_net) {
    case NET_IPV4:
    case NET_IPV6:
    case NET_INTERNAL:
        return true;
    case NET_ONION:
        return m_addr.size() == ADDR_TORV2_SIZE;
    case NET_I2P:
    case NET_CJDNS:
        return false;
    case NET_UNROUTABLE: // m_net is never and should not be set to NET_UNROUTABLE
    case NET_MAX:        // m_net is never and should not be set to NET_MAX
        assert(false);
    } // no default case, so the compiler can warn about missing cases

    assert(false);
}

enum Network CNetAddr::GetNetwork() const
{
    if (IsInternal())
        return NET_INTERNAL;

    if (!IsRoutable())
        return NET_UNROUTABLE;

    return m_net;
}

static std::string IPv4ToString(Span<const uint8_t> a)
{
    return strprintf("%u.%u.%u.%u", a[0], a[1], a[2], a[3]);
}

static std::string IPv6ToString(Span<const uint8_t> a)
{
    assert(a.size() == ADDR_IPV6_SIZE);
    // clang-format off
    return strprintf("%x:%x:%x:%x:%x:%x:%x:%x",
                     ReadBE16(&a[0]),
                     ReadBE16(&a[2]),
                     ReadBE16(&a[4]),
                     ReadBE16(&a[6]),
                     ReadBE16(&a[8]),
                     ReadBE16(&a[10]),
                     ReadBE16(&a[12]),
                     ReadBE16(&a[14]));
    // clang-format on
}

std::string CNetAddr::ToStringIP(bool fUseGetnameinfo) const
{
    switch (m_net) {
    case NET_IPV4:
        return IPv4ToString(m_addr);
    case NET_IPV6: {
        if (fUseGetnameinfo) {
            CService serv(*this, 0);
            struct sockaddr_storage sockaddr;
            socklen_t socklen = sizeof(sockaddr);
            if (serv.GetSockAddr((struct sockaddr*)&sockaddr, &socklen)) {
                char name[1025] = "";
                if (!getnameinfo((const struct sockaddr*)&sockaddr, socklen, name,
                                 sizeof(name), nullptr, 0, NI_NUMERICHOST))
                    return std::string(name);
            }
        }
        return IPv6ToString(m_addr);
    }
    case NET_ONION:
        switch (m_addr.size()) {
        case ADDR_TORV2_SIZE:
            return EncodeBase32(m_addr) + ".onion";
        case ADDR_TORV3_SIZE: {

            uint8_t checksum[torv3::CHECKSUM_LEN];
            torv3::Checksum(m_addr, checksum);

            // TORv3 onion_address = base32(PUBKEY | CHECKSUM | VERSION) + ".onion"
            prevector<torv3::TOTAL_LEN, uint8_t> address{m_addr.begin(), m_addr.end()};
            address.insert(address.end(), checksum, checksum + torv3::CHECKSUM_LEN);
            address.insert(address.end(), torv3::VERSION, torv3::VERSION + sizeof(torv3::VERSION));

            return EncodeBase32(address) + ".onion";
        }
        default:
            assert(false);
        }
    case NET_I2P:
        return EncodeBase32(m_addr, false /* don't pad with = */) + ".b32.i2p";
    case NET_CJDNS:
        return IPv6ToString(m_addr);
    case NET_INTERNAL:
        return EncodeBase32(m_addr) + ".internal";
    case NET_UNROUTABLE: // m_net is never and should not be set to NET_UNROUTABLE
    case NET_MAX:        // m_net is never and should not be set to NET_MAX
        assert(false);
    } // no default case, so the compiler can warn about missing cases

    assert(false);
}

std::string CNetAddr::ToString() const
{
    return ToStringIP();
}

bool operator==(const CNetAddr& a, const CNetAddr& b)
{
    return a.m_net == b.m_net && a.m_addr == b.m_addr;
}

bool operator<(const CNetAddr& a, const CNetAddr& b)
{
    return std::tie(a.m_net, a.m_addr) < std::tie(b.m_net, b.m_addr);
}

bool CNetAddr::GetInAddr(struct in_addr* pipv4Addr) const
{
    if (!IsIPv4())
        return false;
    assert(sizeof(*pipv4Addr) == m_addr.size());
    memcpy(pipv4Addr, m_addr.data(), m_addr.size());
    return true;
}

bool CNetAddr::GetIn6Addr(struct in6_addr* pipv6Addr) const
{
    if (!IsIPv6()) {
        return false;
    }
    assert(sizeof(*pipv6Addr) == m_addr.size());
    memcpy(pipv6Addr, m_addr.data(), m_addr.size());
    return true;
}

bool CNetAddr::HasLinkedIPv4() const
{
    return IsRoutable() && (IsIPv4() || IsRFC6145() || IsRFC6052() || IsRFC3964() || IsRFC4380());
}

uint32_t CNetAddr::GetLinkedIPv4() const
{
    if (IsIPv4()) {
        return ReadBE32(m_addr.data());
    } else if (IsRFC6052() || IsRFC6145()) {
        // mapped IPv4, SIIT translated IPv4: the IPv4 address is the last 4 bytes of the address
        return ReadBE32(MakeSpan(m_addr).last(ADDR_IPV4_SIZE).data());
    } else if (IsRFC3964()) {
        // 6to4 tunneled IPv4: the IPv4 address is in bytes 2-6
        return ReadBE32(MakeSpan(m_addr).subspan(2, ADDR_IPV4_SIZE).data());
    } else if (IsRFC4380()) {
        // Teredo tunneled IPv4: the IPv4 address is in the last 4 bytes of the address, but bitflipped
        return ~ReadBE32(MakeSpan(m_addr).last(ADDR_IPV4_SIZE).data());
    }
    assert(false);
}

uint32_t CNetAddr::GetNetClass() const
{
    // Make sure that if we return NET_IPV6, then IsIPv6() is true. The callers expect that.

    // Check for "internal" first because such addresses are also !IsRoutable()
    // and we don't want to return NET_UNROUTABLE in that case.
    if (IsInternal()) {
        return NET_INTERNAL;
    }
    if (!IsRoutable()) {
        return NET_UNROUTABLE;
    }
    if (HasLinkedIPv4()) {
        return NET_IPV4;
    }
    return m_net;
}

uint32_t CNetAddr::GetMappedAS(const std::vector<bool> &asmap) const {
    uint32_t net_class = GetNetClass();
    if (asmap.size() == 0 || (net_class != NET_IPV4 && net_class != NET_IPV6)) {
        return 0; // Indicates not found, safe because AS0 is reserved per RFC7607.
    }
    std::vector<bool> ip_bits(128);
    if (HasLinkedIPv4()) {
        // For lookup, treat as if it was just an IPv4 address (IPV4_IN_IPV6_PREFIX + IPv4 bits)
        for (int8_t byte_i = 0; byte_i < 12; ++byte_i) {
            for (uint8_t bit_i = 0; bit_i < 8; ++bit_i) {
                ip_bits[byte_i * 8 + bit_i] = (IPV4_IN_IPV6_PREFIX[byte_i] >> (7 - bit_i)) & 1;
            }
        }
        uint32_t ipv4 = GetLinkedIPv4();
        for (int i = 0; i < 32; ++i) {
            ip_bits[96 + i] = (ipv4 >> (31 - i)) & 1;
        }
    } else {
        // Use all 128 bits of the IPv6 address otherwise
        assert(IsIPv6());
        for (int8_t byte_i = 0; byte_i < 16; ++byte_i) {
            uint8_t cur_byte = m_addr[byte_i];
            for (uint8_t bit_i = 0; bit_i < 8; ++bit_i) {
                ip_bits[byte_i * 8 + bit_i] = (cur_byte >> (7 - bit_i)) & 1;
            }
        }
    }
    uint32_t mapped_as = Interpret(asmap, ip_bits);
    return mapped_as;
}

/**
 * Get the canonical identifier of our network group
 *
 * The groups are assigned in a way where it should be costly for an attacker to
 * obtain addresses with many different group identifiers, even if it is cheap
 * to obtain addresses with the same identifier.
 *
 * @note No two connections will be attempted to addresses with the same network
 *       group.
 */
std::vector<unsigned char> CNetAddr::GetGroup(const std::vector<bool> &asmap) const
{
    std::vector<unsigned char> vchRet;
    uint32_t net_class = GetNetClass();
    // If non-empty asmap is supplied and the address is IPv4/IPv6,
    // return ASN to be used for bucketing.
    uint32_t asn = GetMappedAS(asmap);
    if (asn != 0) { // Either asmap was empty, or address has non-asmappable net class (e.g. TOR).
        vchRet.push_back(NET_IPV6); // IPv4 and IPv6 with same ASN should be in the same bucket
        for (int i = 0; i < 4; i++) {
            vchRet.push_back((asn >> (8 * i)) & 0xFF);
        }
        return vchRet;
    }

    vchRet.push_back(net_class);
    int nBits{0};

    if (IsLocal()) {
        // all local addresses belong to the same group
    } else if (IsInternal()) {
        // all internal-usage addresses get their own group
        nBits = ADDR_INTERNAL_SIZE * 8;
    } else if (!IsRoutable()) {
        // all other unroutable addresses belong to the same group
    } else if (HasLinkedIPv4()) {
        // IPv4 addresses (and mapped IPv4 addresses) use /16 groups
        uint32_t ipv4 = GetLinkedIPv4();
        vchRet.push_back((ipv4 >> 24) & 0xFF);
        vchRet.push_back((ipv4 >> 16) & 0xFF);
        return vchRet;
    } else if (IsTor() || IsI2P() || IsCJDNS()) {
        nBits = 4;
    } else if (IsHeNet()) {
        // for he.net, use /36 groups
        nBits = 36;
    } else {
        // for the rest of the IPv6 network, use /32 groups
        nBits = 32;
    }

    // Push our address onto vchRet.
    const size_t num_bytes = nBits / 8;
    vchRet.insert(vchRet.end(), m_addr.begin(), m_addr.begin() + num_bytes);
    nBits %= 8;
    // ...for the last byte, push nBits and for the rest of the byte push 1's
    if (nBits > 0) {
        assert(num_bytes < m_addr.size());
        vchRet.push_back(m_addr[num_bytes] | ((1 << (8 - nBits)) - 1));
    }

    return vchRet;
}

std::vector<unsigned char> CNetAddr::GetAddrBytes() const
{
    if (IsAddrV1Compatible()) {
        uint8_t serialized[V1_SERIALIZATION_SIZE];
        SerializeV1Array(serialized);
        return {std::begin(serialized), std::end(serialized)};
    }
    return std::vector<unsigned char>(m_addr.begin(), m_addr.end());
}

uint64_t CNetAddr::GetHash() const
{
    uint256 hash = Hash(m_addr.begin(), m_addr.end());
    uint64_t nRet;
    memcpy(&nRet, &hash, sizeof(nRet));
    return nRet;
}

// private extensions to enum Network, only returned by GetExtNetwork,
// and only used in GetReachabilityFrom
static const int NET_UNKNOWN = NET_MAX + 0;
static const int NET_TEREDO  = NET_MAX + 1;
int static GetExtNetwork(const CNetAddr *addr)
{
    if (addr == nullptr)
        return NET_UNKNOWN;
    if (addr->IsRFC4380())
        return NET_TEREDO;
    return addr->GetNetwork();
}

/** Calculates a metric for how reachable (*this) is from a given partner */
int CNetAddr::GetReachabilityFrom(const CNetAddr *paddrPartner) const
{
    enum Reachability {
        REACH_UNREACHABLE,
        REACH_DEFAULT,
        REACH_TEREDO,
        REACH_IPV6_WEAK,
        REACH_IPV4,
        REACH_IPV6_STRONG,
        REACH_PRIVATE
    };

    if (!IsRoutable() || IsInternal())
        return REACH_UNREACHABLE;

    int ourNet = GetExtNetwork(this);
    int theirNet = GetExtNetwork(paddrPartner);
    bool fTunnel = IsRFC3964() || IsRFC6052() || IsRFC6145();

    switch(theirNet) {
    case NET_IPV4:
        switch(ourNet) {
        default:       return REACH_DEFAULT;
        case NET_IPV4: return REACH_IPV4;
        }
    case NET_IPV6:
        switch(ourNet) {
        default:         return REACH_DEFAULT;
        case NET_TEREDO: return REACH_TEREDO;
        case NET_IPV4:   return REACH_IPV4;
        case NET_IPV6:   return fTunnel ? REACH_IPV6_WEAK : REACH_IPV6_STRONG; // only prefer giving our IPv6 address if it's not tunnelled
        }
    case NET_ONION:
        switch(ourNet) {
        default:         return REACH_DEFAULT;
        case NET_IPV4:   return REACH_IPV4; // Tor users can connect to IPv4 as well
        case NET_ONION:    return REACH_PRIVATE;
        }
    case NET_TEREDO:
        switch(ourNet) {
        default:          return REACH_DEFAULT;
        case NET_TEREDO:  return REACH_TEREDO;
        case NET_IPV6:    return REACH_IPV6_WEAK;
        case NET_IPV4:    return REACH_IPV4;
        }
    case NET_UNKNOWN:
    case NET_UNROUTABLE:
    default:
        switch(ourNet) {
        default:          return REACH_DEFAULT;
        case NET_TEREDO:  return REACH_TEREDO;
        case NET_IPV6:    return REACH_IPV6_WEAK;
        case NET_IPV4:    return REACH_IPV4;
        case NET_ONION:     return REACH_PRIVATE; // either from Tor, or don't care about our address
        }
    }
}

CService::CService() : port(0)
{
}

CService::CService(const CNetAddr& cip, unsigned short portIn) : CNetAddr(cip), port(portIn)
{
}

CService::CService(const struct in_addr& ipv4Addr, unsigned short portIn) : CNetAddr(ipv4Addr), port(portIn)
{
}

CService::CService(const struct in6_addr& ipv6Addr, unsigned short portIn) : CNetAddr(ipv6Addr), port(portIn)
{
}

CService::CService(const struct sockaddr_in& addr) : CNetAddr(addr.sin_addr), port(ntohs(addr.sin_port))
{
    assert(addr.sin_family == AF_INET);
}

CService::CService(const struct sockaddr_in6 &addr) : CNetAddr(addr.sin6_addr, addr.sin6_scope_id), port(ntohs(addr.sin6_port))
{
   assert(addr.sin6_family == AF_INET6);
}

bool CService::SetSockAddr(const struct sockaddr *paddr)
{
    switch (paddr->sa_family) {
    case AF_INET:
        *this = CService(*(const struct sockaddr_in*)paddr);
        return true;
    case AF_INET6:
        *this = CService(*(const struct sockaddr_in6*)paddr);
        return true;
    default:
        return false;
    }
}

unsigned short CService::GetPort() const
{
    return port;
}

bool operator==(const CService& a, const CService& b)
{
    return static_cast<CNetAddr>(a) == static_cast<CNetAddr>(b) && a.port == b.port;
}

bool operator<(const CService& a, const CService& b)
{
    return static_cast<CNetAddr>(a) < static_cast<CNetAddr>(b) || (static_cast<CNetAddr>(a) == static_cast<CNetAddr>(b) && a.port < b.port);
}

bool CService::GetSockAddr(struct sockaddr* paddr, socklen_t *addrlen) const
{
    if (IsIPv4()) {
        if (*addrlen < (socklen_t)sizeof(struct sockaddr_in))
            return false;
        *addrlen = sizeof(struct sockaddr_in);
        struct sockaddr_in *paddrin = (struct sockaddr_in*)paddr;
        memset(paddrin, 0, *addrlen);
        if (!GetInAddr(&paddrin->sin_addr))
            return false;
        paddrin->sin_family = AF_INET;
        paddrin->sin_port = htons(port);
        return true;
    }
    if (IsIPv6()) {
        if (*addrlen < (socklen_t)sizeof(struct sockaddr_in6))
            return false;
        *addrlen = sizeof(struct sockaddr_in6);
        struct sockaddr_in6 *paddrin6 = (struct sockaddr_in6*)paddr;
        memset(paddrin6, 0, *addrlen);
        if (!GetIn6Addr(&paddrin6->sin6_addr))
            return false;
        paddrin6->sin6_scope_id = scopeId;
        paddrin6->sin6_family = AF_INET6;
        paddrin6->sin6_port = htons(port);
        return true;
    }
    return false;
}

std::vector<unsigned char> CService::GetKey() const
{
    auto key = GetAddrBytes();
    key.push_back(port / 0x100);
    key.push_back(port & 0x0FF);
    return key;
}

std::string CService::ToStringPort() const
{
    return strprintf("%u", port);
}

std::string CService::ToStringIPPort(bool fUseGetnameinfo) const
{
    if (IsIPv4() || IsTor() || IsI2P() || IsInternal()) {
        return ToStringIP(fUseGetnameinfo) + ":" + ToStringPort();
    } else {
        return "[" + ToStringIP(fUseGetnameinfo) + "]:" + ToStringPort();
    }
}

std::string CService::ToString(bool fUseGetnameinfo) const
{
    return ToStringIPPort(fUseGetnameinfo);
}

void CService::SetPort(unsigned short portIn)
{
    port = portIn;
}

CSubNet::CSubNet():
    valid(false)
{
    memset(netmask, 0, sizeof(netmask));
}

CSubNet::CSubNet(const CNetAddr& addr, uint8_t mask) : CSubNet()
{
    valid = (addr.IsIPv4() && mask <= ADDR_IPV4_SIZE * 8) ||
            (addr.IsIPv6() && mask <= ADDR_IPV6_SIZE * 8);
    if (!valid) {
        return;
    }

    assert(mask <= sizeof(netmask) * 8);

    network = addr;

    uint8_t n = mask;
    for (size_t i = 0; i < network.m_addr.size(); ++i) {
        const uint8_t bits = n < 8 ? n : 8;
        netmask[i] = (uint8_t)((uint8_t)0xFF << (8 - bits)); // Set first bits.
        network.m_addr[i] &= netmask[i]; // Normalize network according to netmask.
        n -= bits;
    }
}

/**
 * @returns The number of 1-bits in the prefix of the specified subnet mask. If
 *          the specified subnet mask is not a valid one, -1.
 */
static inline int NetmaskBits(uint8_t x)
{
    switch(x) {
    case 0x00: return 0;
    case 0x80: return 1;
    case 0xc0: return 2;
    case 0xe0: return 3;
    case 0xf0: return 4;
    case 0xf8: return 5;
    case 0xfc: return 6;
    case 0xfe: return 7;
    case 0xff: return 8;
    default: return -1;
    }
}

CSubNet::CSubNet(const CNetAddr& addr, const CNetAddr& mask) : CSubNet()
{
    valid = (addr.IsIPv4() || addr.IsIPv6()) && addr.m_net == mask.m_net;
    if (!valid) {
        return;
    }
    // Check if `mask` contains 1-bits after 0-bits (which is an invalid netmask).
    bool zeros_found = false;
    for (auto b : mask.m_addr) {
        const int num_bits = NetmaskBits(b);
        if (num_bits == -1 || (zeros_found && num_bits != 0)) {
            valid = false;
            return;
        }
        if (num_bits < 8) {
            zeros_found = true;
        }
    }

    assert(mask.m_addr.size() <= sizeof(netmask));

    memcpy(netmask, mask.m_addr.data(), mask.m_addr.size());

    network = addr;

    // Normalize network according to netmask
    for (size_t x = 0; x < network.m_addr.size(); ++x) {
        network.m_addr[x] &= netmask[x];
    }
}

CSubNet::CSubNet(const CNetAddr& addr) : CSubNet()
{
    valid = addr.IsIPv4() || addr.IsIPv6();
    if (!valid) {
        return;
    }

    assert(addr.m_addr.size() <= sizeof(netmask));

    memset(netmask, 0xFF, addr.m_addr.size());

    network = addr;
}

bool CSubNet::Match(const CNetAddr &addr) const
{
    if (!valid || !addr.IsValid() || network.m_net != addr.m_net)
        return false;
    assert(network.m_addr.size() == addr.m_addr.size());
    for (size_t x = 0; x < addr.m_addr.size(); ++x) {
        if ((addr.m_addr[x] & netmask[x]) != network.m_addr[x]) {
            return false;
        }
    }
    return true;
}

std::string CSubNet::ToString() const
{
    assert(network.m_addr.size() <= sizeof(netmask));

    uint8_t cidr = 0;

    for (size_t i = 0; i < network.m_addr.size(); ++i) {
        if (netmask[i] == 0x00) {
            break;
        }
        cidr += NetmaskBits(netmask[i]);
    }

    return network.ToString() + strprintf("/%u", cidr);
}

bool CSubNet::IsValid() const
{
    return valid;
}

bool CSubNet::SanityCheck() const
{
    if (!(network.IsIPv4() || network.IsIPv6())) return false;

    for (size_t x = 0; x < network.m_addr.size(); ++x) {
        if (network.m_addr[x] & ~netmask[x]) return false;
    }

    return true;
}

bool operator==(const CSubNet& a, const CSubNet& b)
{
    return a.valid == b.valid && a.network == b.network && !memcmp(a.netmask, b.netmask, 16);
}

bool operator<(const CSubNet& a, const CSubNet& b)
{
    return (a.network < b.network || (a.network == b.network && memcmp(a.netmask, b.netmask, 16) < 0));
}