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.
Declared in <netaddress.h>
inline constexpr std::array<uint8_t, 6> INTERNAL_IN_IPV6_PREFIX = {
0xFD, 0x6B, 0x88, 0xC0, 0x87, 0x24 // 0xFD + sha256("bitcoin")[0:5].
};