Function LookupSubNet

src/netbase.cpp:831–864

}

CSubNet LookupSubNet(const std::string& subnet_str)
{
    CSubNet subnet;
    assert(!subnet.IsValid());
    if (!ContainsNoNUL(subnet_str)) {
        return subnet;
    }

    const size_t slash_pos{subnet_str.find_last_of('/')};
    const std::string str_addr{subnet_str.substr(0, slash_pos)};
    std::optional<CNetAddr> addr{LookupHost(str_addr, /*fAllowLookup=*/false)};

    if (addr.has_value()) {
        addr = static_cast<CNetAddr>(MaybeFlipIPv6toCJDNS(CService{addr.value(), /*port=*/0}));
        if (slash_pos != subnet_str.npos) {
            const std::string netmask_str{subnet_str.substr(slash_pos + 1)};
            if (const auto netmask{ToIntegral<uint8_t>(netmask_str)}) {
                // Valid number; assume CIDR variable-length subnet masking.
                subnet = CSubNet{addr.value(), *netmask};
            } else {
                // Invalid number; try full netmask syntax. Never allow lookup for netmask.
                const std::optional<CNetAddr> full_netmask{LookupHost(netmask_str, /*fAllowLookup=*/false)};
                if (full_netmask.has_value()) {
                    subnet = CSubNet{addr.value(), full_netmask.value()};
                }
            }
        } else {
            // Single IP subnet (<ipv4>/32 or <ipv6>/128).
            subnet = CSubNet{addr.value()};
        }
    }

    return subnet;
}

bool IsBadPort(uint16_t port)
{