net: change CNetAddr::ip to have flexible size

Before this change `CNetAddr::ip` was a fixed-size array of 16 bytes,
not being able to store larger addresses (e.g. TORv3) and encoded
smaller ones as 16-byte IPv6 addresses.

Change its type to `prevector`, so that it can hold larger addresses and
do not disguise non-IPv6 addresses as IPv6. So the IPv4 address
`1.2.3.4` is now encoded as `01020304` instead of
`00000000000000000000FFFF01020304`.

Rename `CNetAddr::ip` to `CNetAddr::m_addr` because it is not an "IP" or
"IP address" (TOR addresses are not IP addresses).

In order to preserve backward compatibility with serialization (where
e.g. `1.2.3.4` is serialized as `00000000000000000000FFFF01020304`)
introduce `CNetAddr` dedicated legacy serialize/unserialize methods.

Adjust `CSubNet` accordingly. Still use `CSubNet::netmask[]` of fixed 16
bytes, but use the first 4 for IPv4 (not the last 4). Only allow
subnetting for IPv4 and IPv6.

Co-authored-by: Carl Dong <contact@carldong.me>

1 files changed, 198 insertions, 183 deletions

diff --git a/src/netaddress.cpp b/src/netaddress.cpp
index 87f6ce010e..cb874e5e31 100644
--- a/src/netaddress.cpp
+++ b/src/netaddress.cpp
@@ -3,79 +3,90 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <cstdint>
 #include <netaddress.h>
 #include <hash.h>
 #include <util/strencodings.h>
 #include <util/asmap.h>
 #include <tinyformat.h>
 
-static const unsigned char pchIPv4[12] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xff, 0xff };
-static const unsigned char pchOnionCat[] = {0xFD,0x87,0xD8,0x7E,0xEB,0x43};
+#include <algorithm>
+#include <array>
+#include <cstdint>
+#include <iterator>
+#include <tuple>
 
-// 0xFD + sha256("bitcoin")[0:5]
-static const unsigned char g_internal_prefix[] = { 0xFD, 0x6B, 0x88, 0xC0, 0x87, 0x24 };
+constexpr size_t CNetAddr::V1_SERIALIZATION_SIZE;
 
 /**
  * Construct an unspecified IPv6 network address (::/128).
  *
  * @note This address is considered invalid by CNetAddr::IsValid()
  */
-CNetAddr::CNetAddr()
-{
-    memset(ip, 0, sizeof(ip));
-}
+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);
+        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;
-    memcpy(ip, ipIn.ip, sizeof(ip));
+    m_addr = ipIn.m_addr;
+}
+
+template <typename T1, size_t PREFIX_LEN>
+inline bool HasPrefix(const T1& obj, const std::array<uint8_t, PREFIX_LEN>& prefix)
+{
+    return obj.size() >= PREFIX_LEN &&
+           std::equal(std::begin(prefix), std::end(prefix), std::begin(obj));
 }
 
-void CNetAddr::SetLegacyIPv6(const uint8_t ipv6[16])
+void CNetAddr::SetLegacyIPv6(Span<const uint8_t> ipv6)
 {
-    if (memcmp(ipv6, pchIPv4, sizeof(pchIPv4)) == 0) {
+    assert(ipv6.size() == ADDR_IPV6_SIZE);
+
+    size_t skip{0};
+
+    if (HasPrefix(ipv6, IPV4_IN_IPV6_PREFIX)) {
+        // IPv4-in-IPv6
         m_net = NET_IPV4;
-    } else if (memcmp(ipv6, pchOnionCat, sizeof(pchOnionCat)) == 0) {
+        skip = sizeof(IPV4_IN_IPV6_PREFIX);
+    } else if (HasPrefix(ipv6, TORV2_IN_IPV6_PREFIX)) {
+        // TORv2-in-IPv6
         m_net = NET_ONION;
-    } else if (memcmp(ipv6, g_internal_prefix, sizeof(g_internal_prefix)) == 0) {
+        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;
     }
-    memcpy(ip, ipv6, 16);
-}
 
-void CNetAddr::SetRaw(Network network, const uint8_t *ip_in)
-{
-    switch(network)
-    {
-        case NET_IPV4:
-            m_net = NET_IPV4;
-            memcpy(ip, pchIPv4, 12);
-            memcpy(ip+12, ip_in, 4);
-            break;
-        case NET_IPV6:
-            SetLegacyIPv6(ip_in);
-            break;
-        default:
-            assert(!"invalid network");
-    }
+    m_addr.assign(ipv6.begin() + skip, ipv6.end());
 }
 
 /**
- * Try to make this a dummy address that maps the specified name into IPv6 like
- * so: (0xFD + %sha256("bitcoin")[0:5]) + %sha256(name)[0:10]. Such dummy
- * addresses have a prefix of fd6b:88c0:8724::/48 and are guaranteed to not be
- * publicly routable as it falls under RFC4193's fc00::/7 subnet allocated to
- * unique-local addresses.
- *
- * CAddrMan uses these fake addresses to keep track of which DNS seeds were
- * used.
- *
+ * 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 CNetAddr::IsInternal(), CNetAddr::IsRFC4193()
+ * @see NET_INTERNAL, INTERNAL_IN_IPV6_PREFIX, CNetAddr::IsInternal(), CNetAddr::IsRFC4193()
  */
 bool CNetAddr::SetInternal(const std::string &name)
 {
@@ -85,31 +96,26 @@ bool CNetAddr::SetInternal(const std::string &name)
     m_net = NET_INTERNAL;
     unsigned char hash[32] = {};
     CSHA256().Write((const unsigned char*)name.data(), name.size()).Finalize(hash);
-    memcpy(ip, g_internal_prefix, sizeof(g_internal_prefix));
-    memcpy(ip + sizeof(g_internal_prefix), hash, sizeof(ip) - sizeof(g_internal_prefix));
+    m_addr.assign(hash, hash + ADDR_INTERNAL_SIZE);
     return true;
 }
 
 /**
- * Try to make this a dummy address that maps the specified onion address into
- * IPv6 using OnionCat's range and encoding. Such dummy addresses have a prefix
- * of fd87:d87e:eb43::/48 and are guaranteed to not be publicly routable as they
- * fall under RFC4193's fc00::/7 subnet allocated to unique-local addresses.
+ * Parse a TORv2 address and set this object to it.
  *
  * @returns Whether or not the operation was successful.
  *
- * @see CNetAddr::IsTor(), CNetAddr::IsRFC4193()
+ * @see CNetAddr::IsTor()
  */
 bool CNetAddr::SetSpecial(const std::string &strName)
 {
     if (strName.size()>6 && strName.substr(strName.size() - 6, 6) == ".onion") {
         std::vector<unsigned char> vchAddr = DecodeBase32(strName.substr(0, strName.size() - 6).c_str());
-        if (vchAddr.size() != 16-sizeof(pchOnionCat))
+        if (vchAddr.size() != ADDR_TORV2_SIZE) {
             return false;
+        }
         m_net = NET_ONION;
-        memcpy(ip, pchOnionCat, sizeof(pchOnionCat));
-        for (unsigned int i=0; i<16-sizeof(pchOnionCat); i++)
-            ip[i + sizeof(pchOnionCat)] = vchAddr[i];
+        m_addr.assign(vchAddr.begin(), vchAddr.end());
         return true;
     }
     return false;
@@ -117,28 +123,23 @@ bool CNetAddr::SetSpecial(const std::string &strName)
 
 CNetAddr::CNetAddr(const struct in_addr& ipv4Addr)
 {
-    SetRaw(NET_IPV4, (const uint8_t*)&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)
 {
-    SetRaw(NET_IPV6, (const uint8_t*)&ipv6Addr);
+    SetLegacyIPv6(Span<const uint8_t>(reinterpret_cast<const uint8_t*>(&ipv6Addr), sizeof(ipv6Addr)));
     scopeId = scope;
 }
 
-unsigned int CNetAddr::GetByte(int n) const
-{
-    return ip[15-n];
-}
-
 bool CNetAddr::IsBindAny() const
 {
-    const int cmplen = IsIPv4() ? 4 : 16;
-    for (int i = 0; i < cmplen; ++i) {
-        if (GetByte(i)) return false;
+    if (!IsIPv4() && !IsIPv6()) {
+        return false;
     }
-
-    return true;
+    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; }
@@ -148,88 +149,88 @@ bool CNetAddr::IsIPv6() const { return m_net == NET_IPV6; }
 bool CNetAddr::IsRFC1918() const
 {
     return IsIPv4() && (
-        GetByte(3) == 10 ||
-        (GetByte(3) == 192 && GetByte(2) == 168) ||
-        (GetByte(3) == 172 && (GetByte(2) >= 16 && GetByte(2) <= 31)));
+        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() && GetByte(3) == 198 && (GetByte(2) == 18 || GetByte(2) == 19);
+    return IsIPv4() && m_addr[0] == 198 && (m_addr[1] == 18 || m_addr[1] == 19);
 }
 
 bool CNetAddr::IsRFC3927() const
 {
-    return IsIPv4() && (GetByte(3) == 169 && GetByte(2) == 254);
+    return IsIPv4() && HasPrefix(m_addr, std::array<uint8_t, 2>{169, 254});
 }
 
 bool CNetAddr::IsRFC6598() const
 {
-    return IsIPv4() && GetByte(3) == 100 && GetByte(2) >= 64 && GetByte(2) <= 127;
+    return IsIPv4() && m_addr[0] == 100 && m_addr[1] >= 64 && m_addr[1] <= 127;
 }
 
 bool CNetAddr::IsRFC5737() const
 {
-    return IsIPv4() && ((GetByte(3) == 192 && GetByte(2) == 0 && GetByte(1) == 2) ||
-        (GetByte(3) == 198 && GetByte(2) == 51 && GetByte(1) == 100) ||
-        (GetByte(3) == 203 && GetByte(2) == 0 && GetByte(1) == 113));
+    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() && GetByte(15) == 0x20 && GetByte(14) == 0x01 &&
-           GetByte(13) == 0x0D && GetByte(12) == 0xB8;
+    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 4>{0x20, 0x01, 0x0D, 0xB8});
 }
 
 bool CNetAddr::IsRFC3964() const
 {
-    return IsIPv6() && GetByte(15) == 0x20 && GetByte(14) == 0x02;
+    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 2>{0x20, 0x02});
 }
 
 bool CNetAddr::IsRFC6052() const
 {
-    static const unsigned char pchRFC6052[] = {0,0x64,0xFF,0x9B,0,0,0,0,0,0,0,0};
-    return IsIPv6() && memcmp(ip, pchRFC6052, sizeof(pchRFC6052)) == 0;
+    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() && GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0 &&
-           GetByte(12) == 0;
+    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 4>{0x20, 0x01, 0x00, 0x00});
 }
 
 bool CNetAddr::IsRFC4862() const
 {
-    static const unsigned char pchRFC4862[] = {0xFE,0x80,0,0,0,0,0,0};
-    return IsIPv6() && memcmp(ip, pchRFC4862, sizeof(pchRFC4862)) == 0;
+    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 8>{0xFE, 0x80, 0x00, 0x00,
+                                                                0x00, 0x00, 0x00, 0x00});
 }
 
 bool CNetAddr::IsRFC4193() const
 {
-    return IsIPv6() && (GetByte(15) & 0xFE) == 0xFC;
+    return IsIPv6() && (m_addr[0] & 0xFE) == 0xFC;
 }
 
 bool CNetAddr::IsRFC6145() const
 {
-    static const unsigned char pchRFC6145[] = {0,0,0,0,0,0,0,0,0xFF,0xFF,0,0};
-    return IsIPv6() && memcmp(ip, pchRFC6145, sizeof(pchRFC6145)) == 0;
+    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() && GetByte(15) == 0x20 && GetByte(14) == 0x01 &&
-           GetByte(13) == 0x00 && (GetByte(12) & 0xF0) == 0x10;
+    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 3>{0x20, 0x01, 0x00}) &&
+           (m_addr[3] & 0xF0) == 0x10;
 }
 
 bool CNetAddr::IsRFC7343() const
 {
-    return IsIPv6() && GetByte(15) == 0x20 && GetByte(14) == 0x01 &&
-           GetByte(13) == 0x00 && (GetByte(12) & 0xF0) == 0x20;
+    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 3>{0x20, 0x01, 0x00}) &&
+           (m_addr[3] & 0xF0) == 0x20;
 }
 
 bool CNetAddr::IsHeNet() const
 {
-    return (GetByte(15) == 0x20 && GetByte(14) == 0x01 && GetByte(13) == 0x04 && GetByte(12) == 0x70);
+    return IsIPv6() && HasPrefix(m_addr, std::array<uint8_t, 4>{0x20, 0x01, 0x04, 0x70});
 }
 
 /**
@@ -243,13 +244,15 @@ bool CNetAddr::IsTor() const { return m_net == NET_ONION; }
 bool CNetAddr::IsLocal() const
 {
     // IPv4 loopback (127.0.0.0/8 or 0.0.0.0/8)
-    if (IsIPv4() && (GetByte(3) == 127 || GetByte(3) == 0))
+    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(ip, pchLocal, 16) == 0)
+    if (IsIPv6() && memcmp(m_addr.data(), pchLocal, sizeof(pchLocal)) == 0) {
         return true;
+    }
 
     return false;
 }
@@ -272,13 +275,16 @@ bool CNetAddr::IsValid() const
     // header20 vectorlen3 addr26 addr26 addr26 header20 vectorlen3 addr26 addr26 addr26...
     // so if the first length field is garbled, it reads the second batch
     // of addr misaligned by 3 bytes.
-    if (IsIPv6() && memcmp(ip, pchIPv4+3, sizeof(pchIPv4)-3) == 0)
+    if (IsIPv6() && memcmp(m_addr.data(), IPV4_IN_IPV6_PREFIX.data() + 3,
+                           sizeof(IPV4_IN_IPV6_PREFIX) - 3) == 0) {
         return false;
+    }
 
     // unspecified IPv6 address (::/128)
     unsigned char ipNone6[16] = {};
-    if (IsIPv6() && memcmp(ip, ipNone6, 16) == 0)
+    if (IsIPv6() && memcmp(m_addr.data(), ipNone6, sizeof(ipNone6)) == 0) {
         return false;
+    }
 
     // documentation IPv6 address
     if (IsRFC3849())
@@ -287,17 +293,11 @@ bool CNetAddr::IsValid() const
     if (IsInternal())
         return false;
 
-    if (IsIPv4())
-    {
-        // INADDR_NONE
-        uint32_t ipNone = INADDR_NONE;
-        if (memcmp(ip+12, &ipNone, 4) == 0)
-            return false;
-
-        // 0
-        ipNone = 0;
-        if (memcmp(ip+12, &ipNone, 4) == 0)
+    if (IsIPv4()) {
+        const uint32_t addr = ReadBE32(m_addr.data());
+        if (addr == INADDR_ANY || addr == INADDR_NONE) {
             return false;
+        }
     }
 
     return true;
@@ -318,7 +318,7 @@ bool CNetAddr::IsRoutable() const
 }
 
 /**
- * @returns Whether or not this is a dummy address that maps a name into IPv6.
+ * @returns Whether or not this is a dummy address that represents a name.
  *
  * @see CNetAddr::SetInternal(const std::string &)
  */
@@ -341,9 +341,9 @@ enum Network CNetAddr::GetNetwork() const
 std::string CNetAddr::ToStringIP() const
 {
     if (IsTor())
-        return EncodeBase32(&ip[6], 10) + ".onion";
+        return EncodeBase32(m_addr.data(), m_addr.size()) + ".onion";
     if (IsInternal())
-        return EncodeBase32(ip + sizeof(g_internal_prefix), sizeof(ip) - sizeof(g_internal_prefix)) + ".internal";
+        return EncodeBase32(m_addr.data(), m_addr.size()) + ".internal";
     CService serv(*this, 0);
     struct sockaddr_storage sockaddr;
     socklen_t socklen = sizeof(sockaddr);
@@ -353,13 +353,13 @@ std::string CNetAddr::ToStringIP() const
             return std::string(name);
     }
     if (IsIPv4())
-        return strprintf("%u.%u.%u.%u", GetByte(3), GetByte(2), GetByte(1), GetByte(0));
-    else
-        return strprintf("%x:%x:%x:%x:%x:%x:%x:%x",
-                         GetByte(15) << 8 | GetByte(14), GetByte(13) << 8 | GetByte(12),
-                         GetByte(11) << 8 | GetByte(10), GetByte(9) << 8 | GetByte(8),
-                         GetByte(7) << 8 | GetByte(6), GetByte(5) << 8 | GetByte(4),
-                         GetByte(3) << 8 | GetByte(2), GetByte(1) << 8 | GetByte(0));
+        return strprintf("%u.%u.%u.%u", m_addr[0], m_addr[1], m_addr[2], m_addr[3]);
+    assert(IsIPv6());
+    return strprintf("%x:%x:%x:%x:%x:%x:%x:%x",
+                     m_addr[0] << 8 | m_addr[1], m_addr[2] << 8 | m_addr[3],
+                     m_addr[4] << 8 | m_addr[5], m_addr[6] << 8 | m_addr[7],
+                     m_addr[8] << 8 | m_addr[9], m_addr[10] << 8 | m_addr[11],
+                     m_addr[12] << 8 | m_addr[13], m_addr[14] << 8 | m_addr[15]);
 }
 
 std::string CNetAddr::ToString() const
@@ -369,12 +369,12 @@ std::string CNetAddr::ToString() const
 
 bool operator==(const CNetAddr& a, const CNetAddr& b)
 {
-    return a.m_net == b.m_net && memcmp(a.ip, b.ip, 16) == 0;
+    return a.m_net == b.m_net && a.m_addr == b.m_addr;
 }
 
 bool operator<(const CNetAddr& a, const CNetAddr& b)
 {
-    return a.m_net < b.m_net || (a.m_net == b.m_net && memcmp(a.ip, b.ip, 16) < 0);
+    return std::tie(a.m_net, a.m_addr) < std::tie(b.m_net, b.m_addr);
 }
 
 /**
@@ -391,7 +391,8 @@ bool CNetAddr::GetInAddr(struct in_addr* pipv4Addr) const
 {
     if (!IsIPv4())
         return false;
-    memcpy(pipv4Addr, ip+12, 4);
+    assert(sizeof(*pipv4Addr) == m_addr.size());
+    memcpy(pipv4Addr, m_addr.data(), m_addr.size());
     return true;
 }
 
@@ -410,7 +411,8 @@ bool CNetAddr::GetIn6Addr(struct in6_addr* pipv6Addr) const
     if (!IsIPv6()) {
         return false;
     }
-    memcpy(pipv6Addr, ip, 16);
+    assert(sizeof(*pipv6Addr) == m_addr.size());
+    memcpy(pipv6Addr, m_addr.data(), m_addr.size());
     return true;
 }
 
@@ -421,15 +423,17 @@ bool CNetAddr::HasLinkedIPv4() const
 
 uint32_t CNetAddr::GetLinkedIPv4() const
 {
-    if (IsIPv4() || IsRFC6145() || IsRFC6052()) {
-        // IPv4, mapped IPv4, SIIT translated IPv4: the IPv4 address is the last 4 bytes of the address
-        return ReadBE32(ip + 12);
+    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(ip + 2);
+        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(ip + 12);
+        return ~ReadBE32(MakeSpan(m_addr).last(ADDR_IPV4_SIZE).data());
     }
     assert(false);
 }
@@ -458,10 +462,10 @@ uint32_t CNetAddr::GetMappedAS(const std::vector<bool> &asmap) const {
     }
     std::vector<bool> ip_bits(128);
     if (HasLinkedIPv4()) {
-        // For lookup, treat as if it was just an IPv4 address (pchIPv4 prefix + IPv4 bits)
+        // 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] = (pchIPv4[byte_i] >> (7 - bit_i)) & 1;
+                ip_bits[byte_i * 8 + bit_i] = (IPV4_IN_IPV6_PREFIX[byte_i] >> (7 - bit_i)) & 1;
             }
         }
         uint32_t ipv4 = GetLinkedIPv4();
@@ -470,8 +474,9 @@ uint32_t CNetAddr::GetMappedAS(const std::vector<bool> &asmap) const {
         }
     } 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 = GetByte(15 - 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;
             }
@@ -507,19 +512,15 @@ std::vector<unsigned char> CNetAddr::GetGroup(const std::vector<bool> &asmap) co
     }
 
     vchRet.push_back(net_class);
-    int nStartByte = 0;
-    int nBits = 16;
+    int nBits{0};
 
     if (IsLocal()) {
         // all local addresses belong to the same group
-        nBits = 0;
     } else if (IsInternal()) {
         // all internal-usage addresses get their own group
-        nStartByte = sizeof(g_internal_prefix);
-        nBits = (sizeof(ip) - sizeof(g_internal_prefix)) * 8;
+        nBits = ADDR_INTERNAL_SIZE * 8;
     } else if (!IsRoutable()) {
         // all other unroutable addresses belong to the same group
-        nBits = 0;
     } else if (HasLinkedIPv4()) {
         // IPv4 addresses (and mapped IPv4 addresses) use /16 groups
         uint32_t ipv4 = GetLinkedIPv4();
@@ -527,7 +528,6 @@ std::vector<unsigned char> CNetAddr::GetGroup(const std::vector<bool> &asmap) co
         vchRet.push_back((ipv4 >> 16) & 0xFF);
         return vchRet;
     } else if (IsTor()) {
-        nStartByte = 6;
         nBits = 4;
     } else if (IsHeNet()) {
         // for he.net, use /36 groups
@@ -537,23 +537,29 @@ std::vector<unsigned char> CNetAddr::GetGroup(const std::vector<bool> &asmap) co
         nBits = 32;
     }
 
-    // push our ip onto vchRet byte by byte...
-    while (nBits >= 8)
-    {
-        vchRet.push_back(GetByte(15 - nStartByte));
-        nStartByte++;
-        nBits -= 8;
-    }
+    // 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)
-        vchRet.push_back(GetByte(15 - nStartByte) | ((1 << (8 - nBits)) - 1));
+    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
+{
+    uint8_t serialized[V1_SERIALIZATION_SIZE];
+    SerializeV1Array(serialized);
+    return {std::begin(serialized), std::end(serialized)};
+}
+
 uint64_t CNetAddr::GetHash() const
 {
-    uint256 hash = Hash(ip);
+    uint256 hash = Hash(m_addr);
     uint64_t nRet;
     memcpy(&nRet, &hash, sizeof(nRet));
     return nRet;
@@ -764,29 +770,25 @@ CSubNet::CSubNet():
     memset(netmask, 0, sizeof(netmask));
 }
 
-CSubNet::CSubNet(const CNetAddr &addr, int32_t mask)
+CSubNet::CSubNet(const CNetAddr& addr, uint8_t mask) : CSubNet()
 {
-    valid = true;
+    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;
-    // Default to /32 (IPv4) or /128 (IPv6), i.e. match single address
-    memset(netmask, 255, sizeof(netmask));
-
-    // IPv4 addresses start at offset 12, and first 12 bytes must match, so just offset n
-    const int astartofs = network.IsIPv4() ? 12 : 0;
-
-    int32_t n = mask;
-    if(n >= 0 && n <= (128 - astartofs*8)) // Only valid if in range of bits of address
-    {
-        n += astartofs*8;
-        // Clear bits [n..127]
-        for (; n < 128; ++n)
-            netmask[n>>3] &= ~(1<<(7-(n&7)));
-    } else
-        valid = false;
 
-    // Normalize network according to netmask
-    for(int x=0; x<16; ++x)
-        network.ip[x] &= netmask[x];
+    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;
+    }
 }
 
 /**
@@ -809,13 +811,16 @@ static inline int NetmaskBits(uint8_t x)
     }
 }
 
-CSubNet::CSubNet(const CNetAddr &addr, const CNetAddr &mask)
+CSubNet::CSubNet(const CNetAddr& addr, const CNetAddr& mask) : CSubNet()
 {
-    valid = true;
+    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 (size_t i = mask.IsIPv4() ? 12 : 0; i < sizeof(mask.ip); ++i) {
-        const int num_bits = NetmaskBits(mask.ip[i]);
+    for (auto b : mask.m_addr) {
+        const int num_bits = NetmaskBits(b);
         if (num_bits == -1 || (zeros_found && num_bits != 0)) {
             valid = false;
             return;
@@ -824,25 +829,30 @@ CSubNet::CSubNet(const CNetAddr &addr, const CNetAddr &mask)
             zeros_found = true;
         }
     }
-    network = addr;
-    // Default to /32 (IPv4) or /128 (IPv6), i.e. match single address
-    memset(netmask, 255, sizeof(netmask));
 
-    // IPv4 addresses start at offset 12, and first 12 bytes must match, so just offset n
-    const int astartofs = network.IsIPv4() ? 12 : 0;
+    assert(mask.m_addr.size() <= sizeof(netmask));
+
+    memcpy(netmask, mask.m_addr.data(), mask.m_addr.size());
 
-    for(int x=astartofs; x<16; ++x)
-        netmask[x] = mask.ip[x];
+    network = addr;
 
     // Normalize network according to netmask
-    for(int x=0; x<16; ++x)
-        network.ip[x] &= netmask[x];
+    for (size_t x = 0; x < network.m_addr.size(); ++x) {
+        network.m_addr[x] &= netmask[x];
+    }
 }
 
-CSubNet::CSubNet(const CNetAddr &addr):
-    valid(addr.IsValid())
+CSubNet::CSubNet(const CNetAddr& addr) : CSubNet()
 {
-    memset(netmask, 255, sizeof(netmask));
+    valid = addr.IsIPv4() || addr.IsIPv6();
+    if (!valid) {
+        return;
+    }
+
+    assert(addr.m_addr.size() <= sizeof(netmask));
+
+    memset(netmask, 0xFF, addr.m_addr.size());
+
     network = addr;
 }
 
@@ -854,17 +864,22 @@ bool CSubNet::Match(const CNetAddr &addr) const
 {
     if (!valid || !addr.IsValid() || network.m_net != addr.m_net)
         return false;
-    for(int x=0; x<16; ++x)
-        if ((addr.ip[x] & netmask[x]) != network.ip[x])
+    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 = network.IsIPv4() ? 12 : 0; i < sizeof(netmask); ++i) {
+    for (size_t i = 0; i < network.m_addr.size(); ++i) {
         if (netmask[i] == 0x00) {
             break;
         }