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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../https://github.com/eunomia-bpf/bpf-developer-tutorial.html">https://github.com/eunomia-bpf/bpf-developer-tutorial</a></li><li class="chapter-item expanded affix "><li class="part-title">目录</li><li class="chapter-item expanded "><a href="../0-introduce/index.html"><strong aria-hidden="true">1.</strong> 介绍 eBPF 的基本概念、常见的开发工具</a></li><li class="chapter-item expanded "><a href="../1-helloworld/index.html"><strong aria-hidden="true">2.</strong> eBPF Hello World，基本框架和开发流程</a></li><li class="chapter-item expanded "><a href="../2-kprobe-unlink/index.html"><strong aria-hidden="true">3.</strong> 使用 kprobe 监测捕获 unlink 系统调用</a></li><li class="chapter-item expanded "><a href="../3-fentry-unlink/index.html"><strong aria-hidden="true">4.</strong> 使用 fentry 监测捕获 unlink 系统调用</a></li><li class="chapter-item expanded "><a href="../4-opensnoop/index.html"><strong aria-hidden="true">5.</strong> 捕获进程打开文件的系统调用集合，使用全局变量过滤进程 pid</a></li><li class="chapter-item expanded "><a href="../5-uprobe-bashreadline/index.html"><strong aria-hidden="true">6.</strong> 使用 uprobe 捕获 bash 的 readline 函数调用</a></li><li class="chapter-item expanded "><a href="../6-sigsnoop/index.html"><strong aria-hidden="true">7.</strong> 捕获进程发送信号的系统调用集合，使用 hash map 保存状态</a></li><li class="chapter-item expanded "><a href="../7-execsnoop/index.html"><strong aria-hidden="true">8.</strong> 捕获进程执行/退出时间，通过 perf event array 向用户态打印输出</a></li><li class="chapter-item expanded "><a href="../8-exitsnoop/index.html"><strong aria-hidden="true">9.</strong> 使用 exitsnoop 监控进程退出事件，使用 ring buffer 向用户态打印输出</a></li><li class="chapter-item expanded "><a href="../9-runqlat/index.html"><strong aria-hidden="true">10.</strong> 一个 Linux 内核 BPF 程序，通过柱状图来总结调度程序运行队列延迟，显示任务等待运行在 CPU 上的时间长度</a></li><li class="chapter-item expanded "><a href="../10-hardirqs/index.html"><strong aria-hidden="true">11.</strong> 使用 hardirqs 或 softirqs 捕获中断事件</a></li><li class="chapter-item expanded "><a href="../11-bootstrap/index.html"><strong aria-hidden="true">12.</strong> 使用 bootstrap 开发用户态程序并跟踪 exec() 和 exit() 系统调用</a></li><li class="chapter-item expanded "><a href="../13-tcpconnlat/index.html"><strong aria-hidden="true">13.</strong> 使用 libbpf-bootstrap 开发程序统计 TCP 连接延时</a></li><li class="chapter-item expanded "><a href="../14-tcpstates/index.html" class="active"><strong aria-hidden="true">14.</strong> 使用 libbpf-bootstrap 记录 TCP 连接状态与 TCP RTT</a></li><li class="chapter-item expanded "><a href="../15-javagc/index.html"><strong aria-hidden="true">15.</strong> 使用 USDT 捕获用户态 Java GC 事件耗时</a></li><li class="chapter-item expanded "><a href="../16-memleak/index.html"><strong aria-hidden="true">16.</strong> 编写 eBPF 程序 Memleak 监控内存泄漏</a></li><li class="chapter-item expanded "><a href="../17-biopattern/index.html"><strong aria-hidden="true">17.</strong> 编写 eBPF 程序 Biopattern 统计随机/顺序磁盘 I/O</a></li><li class="chapter-item expanded "><a href="../18-further-reading/index.html"><strong aria-hidden="true">18.</strong> 更多的参考资料：论文列表、项目、博客等等</a></li><li class="chapter-item expanded "><a href="../19-lsm-connect/index.html"><strong aria-hidden="true">19.</strong> 使用 LSM 进行安全检测防御</a></li><li class="chapter-item expanded "><a href="../20-tc/index.html"><strong aria-hidden="true">20.</strong> 使用 eBPF 进行 tc 流量控制</a></li><li class="chapter-item expanded affix "><li class="part-title">eBPF 高级特性与进阶主题</li><li class="chapter-item expanded "><a href="../22-android/index.html"><strong aria-hidden="true">21.</strong> 在 Android 上使用 eBPF 程序</a></li><li class="chapter-item expanded "><a href="../23-http/index.html"><strong aria-hidden="true">22.</strong> 使用 eBPF socket filter 或 syscall tracepoint 追踪 HTTP 请求等七层协议</a></li><li class="chapter-item expanded "><a href="../30-sslsniff/index.html"><strong aria-hidden="true">23.</strong> 使用 uprobe 捕获多种库的 SSL/TLS 明文数据</a></li><li class="chapter-item expanded "><a href="../29-sockops/index.html"><strong aria-hidden="true">24.</strong> 使用 sockops 加速网络请求转发</a></li><li class="chapter-item expanded "><a href="../18-further-reading/ebpf-security.zh.html"><strong aria-hidden="true">25.</strong> eBPF 运行时的安全性与面临的挑战</a></li><li class="chapter-item expanded "><a href="../24-hide/index.html"><strong aria-hidden="true">26.</strong> 使用 eBPF 隐藏进程或文件信息</a></li><li class="chapter-item expanded "><a href="../25-signal/index.html"><strong aria-hidden="true">27.</strong> 使用 bpf_send_signal 发送信号终止进程</a></li><li class="chapter-item expanded "><a href="../26-sudo/index.html"><strong aria-hidden="true">28.</strong> 使用 eBPF 添加 sudo 用户</a></li><li class="chapter-item expanded "><a href="../27-replace/index.html"><strong aria-hidden="true">29.</strong> 使用 eBPF 替换任意程序读取或写入的文本</a></li><li class="chapter-item expanded "><a href="../28-detach/index.html"><strong aria-hidden="true">30.</strong> BPF的生命周期：使用 Detached 模式在用户态应用退出后持续运行 eBPF 程序</a></li><li class="chapter-item expanded "><a href="../30-sslsniff/index.html"><strong aria-hidden="true">31.</strong> 使用 eBPF 用户态捕获多种库的 SSL/TLS 明文数据</a></li><li class="chapter-item expanded affix "><li class="part-title">bcc 教程与文档</li><li class="chapter-item expanded "><a href="../bcc-documents/kernel-versions.html"><strong aria-hidden="true">32.</strong> BPF Features by Linux Kernel Version</a></li><li class="chapter-item expanded "><a href="../bcc-documents/kernel_config.html"><strong aria-hidden="true">33.</strong> Kernel Configuration for BPF Features</a></li><li class="chapter-item expanded "><a href="../bcc-documents/reference_guide.html"><strong aria-hidden="true">34.</strong> bcc Reference Guide</a></li><li class="chapter-item expanded "><a href="../bcc-documents/special_filtering.html"><strong aria-hidden="true">35.</strong> Special Filtering</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial.html"><strong aria-hidden="true">36.</strong> bcc Tutorial</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial_bcc_python_developer.html"><strong aria-hidden="true">37.</strong> bcc Python Developer Tutorial</a></li></ol>
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<h1 id="ebpf入门实践教程十四记录-tcp-连接状态与-tcp-rtt"><a class="header" href="#ebpf入门实践教程十四记录-tcp-连接状态与-tcp-rtt">eBPF入门实践教程十四：记录 TCP 连接状态与 TCP RTT</a></h1>
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<p>eBPF (扩展的伯克利数据包过滤器) 是一项强大的网络和性能分析工具，被广泛应用在 Linux 内核上。eBPF 使得开发者能够动态地加载、更新和运行用户定义的代码，而无需重启内核或更改内核源代码。</p>
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<p>在我们的 eBPF 入门实践教程系列的这一篇，我们将介绍两个示例程序：<code>tcpstates</code> 和 <code>tcprtt</code>。<code>tcpstates</code> 用于记录 TCP 连接的状态变化，而 <code>tcprtt</code> 则用于记录 TCP 的往返时间 (RTT, Round-Trip Time)。</p>
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<h2 id="tcprtt-与-tcpstates"><a class="header" href="#tcprtt-与-tcpstates"><code>tcprtt</code> 与 <code>tcpstates</code></a></h2>
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<p>网络质量在当前的互联网环境中至关重要。影响网络质量的因素有许多，包括硬件、网络环境、软件编程的质量等。为了帮助用户更好地定位网络问题，我们引入了 <code>tcprtt</code> 这个工具。<code>tcprtt</code> 可以监控 TCP 链接的往返时间，从而评估网络质量，帮助用户找出可能的问题所在。</p>
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<p>当 TCP 链接建立时，<code>tcprtt</code> 会自动根据当前系统的状况，选择合适的执行函数。在执行函数中，<code>tcprtt</code> 会收集 TCP 链接的各项基本信息，如源地址、目标地址、源端口、目标端口、耗时等，并将这些信息更新到直方图型的 BPF map 中。运行结束后，<code>tcprtt</code> 会通过用户态代码，将收集的信息以图形化的方式展示给用户。</p>
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<p><code>tcpstates</code> 则是一个专门用来追踪和打印 TCP 连接状态变化的工具。它可以显示 TCP 连接在每个状态中的停留时长，单位为毫秒。例如，对于一个单独的 TCP 会话，<code>tcpstates</code> 可以打印出类似以下的输出：</p>
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<pre><code class="language-sh">SKADDR C-PID C-COMM LADDR LPORT RADDR RPORT OLDSTATE -> NEWSTATE MS
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ffff9fd7e8192000 22384 curl 100.66.100.185 0 52.33.159.26 80 CLOSE -> SYN_SENT 0.000
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ffff9fd7e8192000 0 swapper/5 100.66.100.185 63446 52.33.159.26 80 SYN_SENT -> ESTABLISHED 1.373
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ffff9fd7e8192000 22384 curl 100.66.100.185 63446 52.33.159.26 80 ESTABLISHED -> FIN_WAIT1 176.042
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ffff9fd7e8192000 0 swapper/5 100.66.100.185 63446 52.33.159.26 80 FIN_WAIT1 -> FIN_WAIT2 0.536
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ffff9fd7e8192000 0 swapper/5 100.66.100.185 63446 52.33.159.26 80 FIN_WAIT2 -> CLOSE 0.006
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</code></pre>
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<p>以上输出中，最多的时间被花在了 ESTABLISHED 状态，也就是连接已经建立并在传输数据的状态，这个状态到 FIN_WAIT1 状态（开始关闭连接的状态）的转变过程中耗费了 176.042 毫秒。</p>
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<p>在我们接下来的教程中，我们会更深入地探讨这两个工具，解释它们的实现原理，希望这些内容对你在使用 eBPF 进行网络和性能分析方面的工作有所帮助。</p>
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<h2 id="tcpstate"><a class="header" href="#tcpstate">tcpstate</a></h2>
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<p>由于篇幅所限，这里我们主要讨论和分析对应的 eBPF 内核态代码实现。以下是 tcpstate 的 eBPF 代码：</p>
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<pre><code class="language-c">const volatile bool filter_by_sport = false;
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const volatile bool filter_by_dport = false;
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const volatile short target_family = 0;
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, MAX_ENTRIES);
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__type(key, __u16);
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__type(value, __u16);
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} sports SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, MAX_ENTRIES);
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__type(key, __u16);
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__type(value, __u16);
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} dports SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_HASH);
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__uint(max_entries, MAX_ENTRIES);
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__type(key, struct sock *);
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__type(value, __u64);
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} timestamps SEC(".maps");
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struct {
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__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
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__uint(key_size, sizeof(__u32));
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__uint(value_size, sizeof(__u32));
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} events SEC(".maps");
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SEC("tracepoint/sock/inet_sock_set_state")
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int handle_set_state(struct trace_event_raw_inet_sock_set_state *ctx)
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{
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struct sock *sk = (struct sock *)ctx->skaddr;
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__u16 family = ctx->family;
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__u16 sport = ctx->sport;
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__u16 dport = ctx->dport;
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__u64 *tsp, delta_us, ts;
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struct event event = {};
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if (ctx->protocol != IPPROTO_TCP)
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return 0;
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if (target_family && target_family != family)
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return 0;
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if (filter_by_sport && !bpf_map_lookup_elem(&sports, &sport))
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return 0;
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if (filter_by_dport && !bpf_map_lookup_elem(&dports, &dport))
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return 0;
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tsp = bpf_map_lookup_elem(&timestamps, &sk);
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ts = bpf_ktime_get_ns();
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if (!tsp)
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delta_us = 0;
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else
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delta_us = (ts - *tsp) / 1000;
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event.skaddr = (__u64)sk;
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event.ts_us = ts / 1000;
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event.delta_us = delta_us;
|
||
event.pid = bpf_get_current_pid_tgid() >> 32;
|
||
event.oldstate = ctx->oldstate;
|
||
event.newstate = ctx->newstate;
|
||
event.family = family;
|
||
event.sport = sport;
|
||
event.dport = dport;
|
||
bpf_get_current_comm(&event.task, sizeof(event.task));
|
||
|
||
if (family == AF_INET) {
|
||
bpf_probe_read_kernel(&event.saddr, sizeof(event.saddr), &sk->__sk_common.skc_rcv_saddr);
|
||
bpf_probe_read_kernel(&event.daddr, sizeof(event.daddr), &sk->__sk_common.skc_daddr);
|
||
} else { /* family == AF_INET6 */
|
||
bpf_probe_read_kernel(&event.saddr, sizeof(event.saddr), &sk->__sk_common.skc_v6_rcv_saddr.in6_u.u6_addr32);
|
||
bpf_probe_read_kernel(&event.daddr, sizeof(event.daddr), &sk->__sk_common.skc_v6_daddr.in6_u.u6_addr32);
|
||
}
|
||
|
||
bpf_perf_event_output(ctx, &events, BPF_F_CURRENT_CPU, &event, sizeof(event));
|
||
|
||
if (ctx->newstate == TCP_CLOSE)
|
||
bpf_map_delete_elem(&timestamps, &sk);
|
||
else
|
||
bpf_map_update_elem(&timestamps, &sk, &ts, BPF_ANY);
|
||
|
||
return 0;
|
||
}
|
||
</code></pre>
|
||
<p><code>tcpstates</code>主要依赖于 eBPF 的 Tracepoints 来捕获 TCP 连接的状态变化，从而跟踪 TCP 连接在每个状态下的停留时间。</p>
|
||
<h3 id="定义-bpf-maps"><a class="header" href="#定义-bpf-maps">定义 BPF Maps</a></h3>
|
||
<p>在<code>tcpstates</code>程序中，首先定义了几个 BPF Maps，它们是 eBPF 程序和用户态程序之间交互的主要方式。<code>sports</code>和<code>dports</code>分别用于存储源端口和目标端口，用于过滤 TCP 连接；<code>timestamps</code>用于存储每个 TCP 连接的时间戳，以计算每个状态的停留时间；<code>events</code>则是一个 perf_event 类型的 map，用于将事件数据发送到用户态。</p>
|
||
<h3 id="追踪-tcp-连接状态变化"><a class="header" href="#追踪-tcp-连接状态变化">追踪 TCP 连接状态变化</a></h3>
|
||
<p>程序定义了一个名为<code>handle_set_state</code>的函数，该函数是一个 tracepoint 类型的程序，它将被挂载到<code>sock/inet_sock_set_state</code>这个内核 tracepoint 上。每当 TCP 连接状态发生变化时，这个 tracepoint 就会被触发，然后执行<code>handle_set_state</code>函数。</p>
|
||
<p>在<code>handle_set_state</code>函数中，首先通过一系列条件判断确定是否需要处理当前的 TCP 连接，然后从<code>timestamps</code>map 中获取当前连接的上一个时间戳，然后计算出停留在当前状态的时间。接着，程序将收集到的数据放入一个 event 结构体中，并通过<code>bpf_perf_event_output</code>函数将该 event 发送到用户态。</p>
|
||
<h3 id="更新时间戳"><a class="header" href="#更新时间戳">更新时间戳</a></h3>
|
||
<p>最后，根据 TCP 连接的新状态，程序将进行不同的操作：如果新状态为 TCP_CLOSE，表示连接已关闭，程序将从<code>timestamps</code>map 中删除该连接的时间戳；否则，程序将更新该连接的时间戳。</p>
|
||
<p>用户态的部分主要是通过 libbpf 来加载 eBPF 程序，然后通过 perf_event 来接收内核中的事件数据：</p>
|
||
<pre><code class="language-c">static void handle_event(void* ctx, int cpu, void* data, __u32 data_sz) {
|
||
char ts[32], saddr[26], daddr[26];
|
||
struct event* e = data;
|
||
struct tm* tm;
|
||
int family;
|
||
time_t t;
|
||
|
||
if (emit_timestamp) {
|
||
time(&t);
|
||
tm = localtime(&t);
|
||
strftime(ts, sizeof(ts), "%H:%M:%S", tm);
|
||
printf("%8s ", ts);
|
||
}
|
||
|
||
inet_ntop(e->family, &e->saddr, saddr, sizeof(saddr));
|
||
inet_ntop(e->family, &e->daddr, daddr, sizeof(daddr));
|
||
if (wide_output) {
|
||
family = e->family == AF_INET ? 4 : 6;
|
||
printf(
|
||
"%-16llx %-7d %-16s %-2d %-26s %-5d %-26s %-5d %-11s -> %-11s "
|
||
"%.3f\n",
|
||
e->skaddr, e->pid, e->task, family, saddr, e->sport, daddr,
|
||
e->dport, tcp_states[e->oldstate], tcp_states[e->newstate],
|
||
(double)e->delta_us / 1000);
|
||
} else {
|
||
printf(
|
||
"%-16llx %-7d %-10.10s %-15s %-5d %-15s %-5d %-11s -> %-11s %.3f\n",
|
||
e->skaddr, e->pid, e->task, saddr, e->sport, daddr, e->dport,
|
||
tcp_states[e->oldstate], tcp_states[e->newstate],
|
||
(double)e->delta_us / 1000);
|
||
}
|
||
}
|
||
</code></pre>
|
||
<p><code>handle_event</code>就是这样一个回调函数，它会被 perf_event 调用，每当内核有新的事件到达时，它就会处理这些事件。</p>
|
||
<p>在<code>handle_event</code>函数中，我们首先通过<code>inet_ntop</code>函数将二进制的 IP 地址转换成人类可读的格式，然后根据是否需要输出宽格式，分别打印不同的信息。这些信息包括了事件的时间戳、源 IP 地址、源端口、目标 IP 地址、目标端口、旧状态、新状态以及在旧状态停留的时间。</p>
|
||
<p>这样，用户就可以清晰地看到 TCP 连接状态的变化，以及每个状态的停留时间，从而帮助他们诊断网络问题。</p>
|
||
<p>总结起来，用户态部分的处理主要涉及到了以下几个步骤：</p>
|
||
<ol>
|
||
<li>使用 libbpf 加载并运行 eBPF 程序。</li>
|
||
<li>设置回调函数来接收内核发送的事件。</li>
|
||
<li>处理接收到的事件，将其转换成人类可读的格式并打印。</li>
|
||
</ol>
|
||
<p>以上就是<code>tcpstates</code>程序用户态部分的主要实现逻辑。通过这一章的学习，你应该已经对如何在用户态处理内核事件有了更深入的理解。在下一章中，我们将介绍更多关于如何使用 eBPF 进行网络监控的知识。</p>
|
||
<h3 id="tcprtt"><a class="header" href="#tcprtt">tcprtt</a></h3>
|
||
<p>在本章节中，我们将分析<code>tcprtt</code> eBPF 程序的内核态代码。<code>tcprtt</code>是一个用于测量 TCP 往返时间(Round Trip Time, RTT)的程序，它将 RTT 的信息统计到一个 histogram 中。</p>
|
||
<pre><code class="language-c">
|
||
/// @sample {"interval": 1000, "type" : "log2_hist"}
|
||
struct {
|
||
__uint(type, BPF_MAP_TYPE_HASH);
|
||
__uint(max_entries, MAX_ENTRIES);
|
||
__type(key, u64);
|
||
__type(value, struct hist);
|
||
} hists SEC(".maps");
|
||
|
||
static struct hist zero;
|
||
|
||
SEC("fentry/tcp_rcv_established")
|
||
int BPF_PROG(tcp_rcv, struct sock *sk)
|
||
{
|
||
const struct inet_sock *inet = (struct inet_sock *)(sk);
|
||
struct tcp_sock *ts;
|
||
struct hist *histp;
|
||
u64 key, slot;
|
||
u32 srtt;
|
||
|
||
if (targ_sport && targ_sport != inet->inet_sport)
|
||
return 0;
|
||
if (targ_dport && targ_dport != sk->__sk_common.skc_dport)
|
||
return 0;
|
||
if (targ_saddr && targ_saddr != inet->inet_saddr)
|
||
return 0;
|
||
if (targ_daddr && targ_daddr != sk->__sk_common.skc_daddr)
|
||
return 0;
|
||
|
||
if (targ_laddr_hist)
|
||
key = inet->inet_saddr;
|
||
else if (targ_raddr_hist)
|
||
key = inet->sk.__sk_common.skc_daddr;
|
||
else
|
||
key = 0;
|
||
histp = bpf_map_lookup_or_try_init(&hists, &key, &zero);
|
||
if (!histp)
|
||
return 0;
|
||
ts = (struct tcp_sock *)(sk);
|
||
srtt = BPF_CORE_READ(ts, srtt_us) >> 3;
|
||
if (targ_ms)
|
||
srtt /= 1000U;
|
||
slot = log2l(srtt);
|
||
if (slot >= MAX_SLOTS)
|
||
slot = MAX_SLOTS - 1;
|
||
__sync_fetch_and_add(&histp->slots[slot], 1);
|
||
if (targ_show_ext) {
|
||
__sync_fetch_and_add(&histp->latency, srtt);
|
||
__sync_fetch_and_add(&histp->cnt, 1);
|
||
}
|
||
return 0;
|
||
}
|
||
</code></pre>
|
||
<p>首先，我们定义了一个 hash 类型的 eBPF map，名为<code>hists</code>，它用来存储 RTT 的统计信息。在这个 map 中，键是 64 位整数，值是一个<code>hist</code>结构，这个结构包含了一个数组，用来存储不同 RTT 区间的数量。</p>
|
||
<p>接着，我们定义了一个 eBPF 程序，名为<code>tcp_rcv</code>，这个程序会在每次内核中处理 TCP 收包的时候被调用。在这个程序中，我们首先根据过滤条件（源/目标 IP 地址和端口）对 TCP 连接进行过滤。如果满足条件，我们会根据设置的参数选择相应的 key（源 IP 或者目标 IP 或者 0），然后在<code>hists</code> map 中查找或者初始化对应的 histogram。</p>
|
||
<p>接下来，我们读取 TCP 连接的<code>srtt_us</code>字段，这个字段表示了平滑的 RTT 值，单位是微秒。然后我们将这个 RTT 值转换为对数形式，并将其作为 slot 存储到 histogram 中。</p>
|
||
<p>如果设置了<code>show_ext</code>参数，我们还会将 RTT 值和计数器累加到 histogram 的<code>latency</code>和<code>cnt</code>字段中。</p>
|
||
<p>通过以上的处理，我们可以对每个 TCP 连接的 RTT 进行统计和分析，从而更好地理解网络的性能状况。</p>
|
||
<p>总结起来，<code>tcprtt</code> eBPF 程序的主要逻辑包括以下几个步骤：</p>
|
||
<ol>
|
||
<li>根据过滤条件对 TCP 连接进行过滤。</li>
|
||
<li>在<code>hists</code> map 中查找或者初始化对应的 histogram。</li>
|
||
<li>读取 TCP 连接的<code>srtt_us</code>字段，并将其转换为对数形式，存储到 histogram 中。</li>
|
||
<li>如果设置了<code>show_ext</code>参数，将 RTT 值和计数器累加到 histogram 的<code>latency</code>和<code>cnt</code>字段中。</li>
|
||
</ol>
|
||
<p>tcprtt 挂载到了内核态的 tcp_rcv_established 函数上：</p>
|
||
<pre><code class="language-c">void tcp_rcv_established(struct sock *sk, struct sk_buff *skb);
|
||
</code></pre>
|
||
<p>这个函数是在内核中处理TCP接收数据的主要函数，主要在TCP连接处于<code>ESTABLISHED</code>状态时被调用。这个函数的处理逻辑包括一个快速路径和一个慢速路径。快速路径在以下几种情况下会被禁用：</p>
|
||
<ul>
|
||
<li>我们宣布了一个零窗口 - 零窗口探测只能在慢速路径中正确处理。</li>
|
||
<li>收到了乱序的数据包。</li>
|
||
<li>期待接收紧急数据。</li>
|
||
<li>没有剩余的缓冲区空间。</li>
|
||
<li>接收到了意外的TCP标志/窗口值/头部长度（通过检查TCP头部与预设标志进行检测）。</li>
|
||
<li>数据在两个方向上都在传输。快速路径只支持纯发送者或纯接收者（这意味着序列号或确认值必须保持不变）。</li>
|
||
<li>接收到了意外的TCP选项。</li>
|
||
</ul>
|
||
<p>当这些条件不满足时，它会进入一个标准的接收处理过程，这个过程遵循RFC793来处理所有情况。前三种情况可以通过正确的预设标志设置来保证，剩下的情况则需要内联检查。当一切都正常时，快速处理过程会在<code>tcp_data_queue</code>函数中被开启。</p>
|
||
<h2 id="编译运行"><a class="header" href="#编译运行">编译运行</a></h2>
|
||
<p>对于 tcpstates，可以通过以下命令编译和运行 libbpf 应用：</p>
|
||
<pre><code class="language-console">$ make
|
||
...
|
||
BPF .output/tcpstates.bpf.o
|
||
GEN-SKEL .output/tcpstates.skel.h
|
||
CC .output/tcpstates.o
|
||
BINARY tcpstates
|
||
$ sudo ./tcpstates
|
||
SKADDR PID COMM LADDR LPORT RADDR RPORT OLDSTATE -> NEWSTATE MS
|
||
ffff9bf61bb62bc0 164978 node 192.168.88.15 0 52.178.17.2 443 CLOSE -> SYN_SENT 0.000
|
||
ffff9bf61bb62bc0 0 swapper/0 192.168.88.15 41596 52.178.17.2 443 SYN_SENT -> ESTABLISHED 225.794
|
||
ffff9bf61bb62bc0 0 swapper/0 192.168.88.15 41596 52.178.17.2 443 ESTABLISHED -> CLOSE_WAIT 901.454
|
||
ffff9bf61bb62bc0 164978 node 192.168.88.15 41596 52.178.17.2 443 CLOSE_WAIT -> LAST_ACK 0.793
|
||
ffff9bf61bb62bc0 164978 node 192.168.88.15 41596 52.178.17.2 443 LAST_ACK -> LAST_ACK 0.086
|
||
ffff9bf61bb62bc0 228759 kworker/u6 192.168.88.15 41596 52.178.17.2 443 LAST_ACK -> CLOSE 0.193
|
||
ffff9bf6d8ee88c0 229832 redis-serv 0.0.0.0 6379 0.0.0.0 0 CLOSE -> LISTEN 0.000
|
||
ffff9bf6d8ee88c0 229832 redis-serv 0.0.0.0 6379 0.0.0.0 0 LISTEN -> CLOSE 1.763
|
||
ffff9bf7109d6900 88750 node 127.0.0.1 39755 127.0.0.1 50966 ESTABLISHED -> FIN_WAIT1 0.000
|
||
</code></pre>
|
||
<p>对于 tcprtt，我们可以使用 eunomia-bpf 编译运行这个例子：</p>
|
||
<p>Compile:</p>
|
||
<pre><code class="language-shell">docker run -it -v `pwd`/:/src/ ghcr.io/eunomia-bpf/ecc-`uname -m`:latest
|
||
</code></pre>
|
||
<p>或者</p>
|
||
<pre><code class="language-console">$ ecc tcprtt.bpf.c tcprtt.h
|
||
Compiling bpf object...
|
||
Generating export types...
|
||
Packing ebpf object and config into package.json...
|
||
</code></pre>
|
||
<p>运行：</p>
|
||
<pre><code class="language-console">$ sudo ecli run package.json -h
|
||
A simple eBPF program
|
||
|
||
|
||
Usage: package.json [OPTIONS]
|
||
|
||
Options:
|
||
--verbose Whether to show libbpf debug information
|
||
--targ_laddr_hist Set value of `bool` variable targ_laddr_hist
|
||
--targ_raddr_hist Set value of `bool` variable targ_raddr_hist
|
||
--targ_show_ext Set value of `bool` variable targ_show_ext
|
||
--targ_sport <targ_sport> Set value of `__u16` variable targ_sport
|
||
--targ_dport <targ_dport> Set value of `__u16` variable targ_dport
|
||
--targ_saddr <targ_saddr> Set value of `__u32` variable targ_saddr
|
||
--targ_daddr <targ_daddr> Set value of `__u32` variable targ_daddr
|
||
--targ_ms Set value of `bool` variable targ_ms
|
||
-h, --help Print help
|
||
-V, --version Print version
|
||
|
||
Built with eunomia-bpf framework.
|
||
See https://github.com/eunomia-bpf/eunomia-bpf for more information.
|
||
|
||
$ sudo ecli run package.json
|
||
key = 0
|
||
latency = 0
|
||
cnt = 0
|
||
|
||
(unit) : count distribution
|
||
0 -> 1 : 0 | |
|
||
2 -> 3 : 0 | |
|
||
4 -> 7 : 0 | |
|
||
8 -> 15 : 0 | |
|
||
16 -> 31 : 0 | |
|
||
32 -> 63 : 0 | |
|
||
64 -> 127 : 0 | |
|
||
128 -> 255 : 0 | |
|
||
256 -> 511 : 0 | |
|
||
512 -> 1023 : 4 |******************** |
|
||
1024 -> 2047 : 1 |***** |
|
||
2048 -> 4095 : 0 | |
|
||
4096 -> 8191 : 8 |****************************************|
|
||
|
||
key = 0
|
||
latency = 0
|
||
cnt = 0
|
||
|
||
(unit) : count distribution
|
||
0 -> 1 : 0 | |
|
||
2 -> 3 : 0 | |
|
||
4 -> 7 : 0 | |
|
||
8 -> 15 : 0 | |
|
||
16 -> 31 : 0 | |
|
||
32 -> 63 : 0 | |
|
||
64 -> 127 : 0 | |
|
||
128 -> 255 : 0 | |
|
||
256 -> 511 : 0 | |
|
||
512 -> 1023 : 11 |*************************** |
|
||
1024 -> 2047 : 1 |** |
|
||
2048 -> 4095 : 0 | |
|
||
4096 -> 8191 : 16 |****************************************|
|
||
8192 -> 16383 : 4 |********** |
|
||
</code></pre>
|
||
<p>完整源代码：</p>
|
||
<ul>
|
||
<li><a href="https://github.com/eunomia-bpf/bpf-developer-tutorial/tree/main/src/14-tcpstates">https://github.com/eunomia-bpf/bpf-developer-tutorial/tree/main/src/14-tcpstates</a></li>
|
||
</ul>
|
||
<p>参考资料：</p>
|
||
<ul>
|
||
<li><a href="https://github.com/iovisor/bcc/blob/master/tools/tcpstates_example.txt">tcpstates</a></li>
|
||
<li><a href="https://github.com/iovisor/bcc/blob/master/tools/tcprtt.py">tcprtt</a></li>
|
||
<li><a href="https://github.com/iovisor/bcc/blob/master/libbpf-tools/tcpstates.bpf.c">libbpf-tools/tcpstates</a></li>
|
||
</ul>
|
||
<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
|
||
<p>通过本篇 eBPF 入门实践教程，我们学习了如何使用tcpstates和tcprtt这两个 eBPF 示例程序，监控和分析 TCP 的连接状态和往返时间。我们了解了tcpstates和tcprtt的工作原理和实现方式，包括如何使用 BPF map 存储数据，如何在 eBPF 程序中获取和处理 TCP 连接信息，以及如何在用户态应用程序中解析和显示 eBPF 程序收集的数据。</p>
|
||
<p>如果您希望学习更多关于 eBPF 的知识和实践，可以访问我们的教程代码仓库 <a href="https://github.com/eunomia-bpf/bpf-developer-tutorial">https://github.com/eunomia-bpf/bpf-developer-tutorial</a> 或网站 <a href="https://eunomia.dev/zh/tutorials/">https://eunomia.dev/zh/tutorials/</a> 以获取更多示例和完整的教程。接下来的教程将进一步探讨 eBPF 的高级特性，我们会继续分享更多有关 eBPF 开发实践的内容。</p>
|
||
|
||
</main>
|
||
|
||
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