limit = 3
ip_list = {}

function on_stop(client_id, ip)
    local client_id_list = ip_list[ip]
    for i,v in ipairs(client_id_list) do
        if v == client_id then
            table.remove(client_id_list, i)
            break
        end
    end
    if #client_id_list == 0 then
        ip_list[ip] = nil
    end
end

function on_start(client_id, ip)
    local client_id_list = ip_list[ip]
    if not client_id_list then
        client_id_list = {}
        ip_list[ip] = client_id_list
    end
    table.insert(client_id_list, client_id)
    if #client_id_list > limit then
        local first_client_id = client_id_list[1]
        local c = http_output_client_list[first_client_id]
        c.server:close(c.client)
    end
end

function auth_request(client_id, request, callback)
    if not request then
        local c = http_output_client_list[client_id]
        on_stop(client_id, c.request.addr)
        return nil
    end

    on_start(client_id, request.addr)
    callback(true)