#include <amxmodx>
#include <amxmisc>

#define KICK_MSG "your kick message"

public plugin_init()
{
    register_plugin(PLUGIN, VERSION, AUTHOR)
    register_cvar("amx_only_steam", "1")
}
public client_putinserver(id)
{
    if (get_cvar_num("amx_only_steam") == 1)
        return PLUGIN_HANDLER

    if (is_user_bot(id) && is_user_hltv(id))
        return PLUGIN_HANDLED

    if (get_user_flags(id) & ADMIN_IMMUNITY)
        return PLUGIN_HANDLED

    if (get_cvar_num("amx_only_steam") == 1)
    {
        new ui[32]
        new uname[32]
        get_user_ip(id, uip, 31, 1)
        get_user_name(id, uname, 31)

        if (!isSteam(id))
        {
            log_amx("User ^"%s^" ^"%s^" kicked due to invalid IP address", uname, uip)
            server_cmd("kick #%d ^"%s^"", get_user_userid(id), KICK_MSG)
        }
    }

    return PLUGIN_CONTINUE
}
bool:isSteam(id)
{
    new bool:result = false
    new pcv_dp_r_protocol = get_cvar_pointer ("dp_r_protocol")
    new pcv_dp_r_id_provider = get_cvar_pointer ("dp_r_id_provider")
    if (pcv_dp_r_protocol && pcv_dp_r_id_provider)
    {
        server_cmd("dp_clientinfo %d", id)
        server_exec()
        new authprov = get_pcvar_num(pcv_dp_r_id_provider)

        if (authprov == 2) result = true
    }

    return result
}