【工具链】抓包分析：协议问题的定位利器

---服务器侧抓包：过滤游戏端口
function Sniff.capture(seconds, port)
    local file = "cap_" .. os.date("%H%M%S") .. ".pcap"
    os.execute(string.format(
        "tcpdump -i eth0 port %d -w %s -c 5000",
        port, file))
    return file
end

---定位某玩家的会话流
function Sniff.byUser(file, userId)
    local ip = Session.ipOf(userId)
    os.execute(string.format(
        "tcpdump -r %s host %s -w cap_%s.pcap",
        file, ip, userId))
    return "cap_" .. userId .. ".pcap"
end

---按协议结构解析会话流
function Sniff.parse(file, proto)
    local f = io.open(file, "rb")
    local out = {}
    for pkt in Sniff.packets(f) do
        local id, body = proto:decode(pkt.payload)
        if id then
            out[#out + 1] = {
                dir = pkt.dir,
                id = id,
                name = proto.nameOf(id),
                len = #pkt.payload,
                at = pkt.at,
            }
        end
    end
    return out
end