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<ol class="chapter"><li class="chapter-item expanded affix "><li class="part-title">eBPF 入门开发实践教程</li><li class="chapter-item expanded "><a href="../0-introduce/index.html"><strong aria-hidden="true">1.</strong> eBPF 入门开发实践教程一：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 入门开发实践教程二：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> eBPF 入门开发实践教程二：在 eBPF 中使用 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> eBPF 入门开发实践教程三：在 eBPF 中使用 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> eBPF 入门开发实践教程四：在 eBPF 中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> eBPF 入门开发实践教程五：在 eBPF 中使用 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> eBPF 入门开发实践教程六：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> eBPF 入门实践教程七：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> eBPF 入门开发实践教程八：在 eBPF 中使用 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> eBPF 入门开发实践教程九：一个 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> eBPF 入门开发实践教程十：在 eBPF 中使用 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> eBPF 入门开发实践教程十一：在 eBPF 中使用 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 affix "><li class="part-title">eBPF入门实践教程</li><li class="chapter-item expanded "><a href="../13-tcpconnlat/index.html"><strong aria-hidden="true">13.</strong> eBPF入门实践教程：使用 libbpf-bootstrap 开发程序统计 TCP 连接延时</a></li><li class="chapter-item expanded "><a href="../13-tcpconnlat/tcpconnlat.html"><strong aria-hidden="true">14.</strong> eBPF 入门实践教程：编写 eBPF 程序 tcpconnlat 测量 tcp 连接延时</a></li><li class="chapter-item expanded "><a href="../14-tcpstates/index.html"><strong aria-hidden="true">15.</strong> eBPF入门实践教程：使用 libbpf-bootstrap 开发程序统计 TCP 连接延时</a></li><li class="chapter-item expanded "><a href="../15-tcprtt/index.html"><strong aria-hidden="true">16.</strong> eBPF 入门实践教程：编写 eBPF 程序 Tcprtt 测量 TCP 连接的往返时间</a></li><li class="chapter-item expanded "><a href="../16-memleak/index.html"><strong aria-hidden="true">17.</strong> eBPF 入门实践教程：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">18.</strong> eBPF 入门实践教程：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">19.</strong> 更多的参考资料</a></li><li class="chapter-item expanded "><a href="../19-lsm-connect/index.html"><strong aria-hidden="true">20.</strong> eBPF 入门实践教程：使用 LSM 进行安全检测防御</a></li><li class="chapter-item expanded "><a href="../20-tc/index.html" class="active"><strong aria-hidden="true">21.</strong> eBPF 入门实践教程：使用 eBPF 进行 tc 流量控制</a></li><li class="chapter-item expanded affix "><li class="part-title">bcc Guide</li><li class="chapter-item expanded "><a href="../bcc-documents/kernel-versions.html"><strong aria-hidden="true">22.</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">23.</strong> Kernel Configuration for BPF Features</a></li><li class="chapter-item expanded "><a href="../bcc-documents/reference_guide.html"><strong aria-hidden="true">24.</strong> bcc Reference Guide</a></li><li class="chapter-item expanded "><a href="../bcc-documents/special_filtering.html"><strong aria-hidden="true">25.</strong> Special Filtering</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial.html"><strong aria-hidden="true">26.</strong> bcc Tutorial</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial_bcc_python_developer.html"><strong aria-hidden="true">27.</strong> bcc Python Developer Tutorial</a></li></ol>
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<h1 id="ebpf-入门实践教程使用-ebpf-进行-tc-流量控制"><a class="header" href="#ebpf-入门实践教程使用-ebpf-进行-tc-流量控制">eBPF 入门实践教程：使用 eBPF 进行 tc 流量控制</a></h1>
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<h2 id="tc-程序示例"><a class="header" href="#tc-程序示例">tc 程序示例</a></h2>
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<pre><code class="language-c">#include <vmlinux.h>
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#include <bpf/bpf_endian.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_tracing.h>
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#define TC_ACT_OK 0
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#define ETH_P_IP 0x0800 /* Internet Protocol packet */
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/// @tchook {"ifindex":1, "attach_point":"BPF_TC_INGRESS"}
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/// @tcopts {"handle":1, "priority":1}
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SEC("tc")
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int tc_ingress(struct __sk_buff *ctx)
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{
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void *data_end = (void *)(__u64)ctx->data_end;
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void *data = (void *)(__u64)ctx->data;
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struct ethhdr *l2;
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struct iphdr *l3;
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if (ctx->protocol != bpf_htons(ETH_P_IP))
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return TC_ACT_OK;
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l2 = data;
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if ((void *)(l2 + 1) > data_end)
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return TC_ACT_OK;
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l3 = (struct iphdr *)(l2 + 1);
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if ((void *)(l3 + 1) > data_end)
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return TC_ACT_OK;
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bpf_printk("Got IP packet: tot_len: %d, ttl: %d", bpf_ntohs(l3->tot_len), l3->ttl);
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return TC_ACT_OK;
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}
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char __license[] SEC("license") = "GPL";
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</code></pre>
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<p>这段代码定义了一个 eBPF 程序，它可以通过 Linux TC（Transmission Control）来捕获数据包并进行处理。在这个程序中，我们限定了只捕获 IPv4 协议的数据包，然后通过 bpf_printk 函数打印出数据包的总长度和 Time-To-Live（TTL）字段的值。</p>
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<p>需要注意的是，我们在代码中使用了一些 BPF 库函数，例如 bpf_htons 和 bpf_ntohs 函数，它们用于进行网络字节序和主机字节序之间的转换。此外，我们还使用了一些注释来为 TC 提供附加点和选项信息。例如，在这段代码的开头，我们使用了以下注释：</p>
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<pre><code class="language-c">/// @tchook {"ifindex":1, "attach_point":"BPF_TC_INGRESS"}
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/// @tcopts {"handle":1, "priority":1}
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</code></pre>
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<p>这些注释告诉 TC 将 eBPF 程序附加到网络接口的 ingress 附加点，并指定了 handle 和 priority 选项的值。</p>
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<p>总之，这段代码实现了一个简单的 eBPF 程序，用于捕获数据包并打印出它们的信息。</p>
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<h2 id="编译运行"><a class="header" href="#编译运行">编译运行</a></h2>
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<pre><code class="language-console">docker run -it -v `pwd`/:/src/ yunwei37/ebpm:latest
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</code></pre>
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<p>or compile with <code>ecc</code>:</p>
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<pre><code class="language-console">$ ecc tc.bpf.c
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Compiling bpf object...
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Packing ebpf object and config into package.json...
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</code></pre>
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<pre><code class="language-shell">$ sudo ecli ./package.json
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...
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Successfully started! Please run `sudo cat /sys/kernel/debug/tracing/trace_pipe` to see output of the BPF program.
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......
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</code></pre>
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<p>The <code>tc</code> output in <code>/sys/kernel/debug/tracing/trace_pipe</code> should look
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something like this:</p>
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<pre><code class="language-console">$ sudo cat /sys/kernel/debug/tracing/trace_pipe
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node-1254811 [007] ..s1 8737831.671074: 0: Got IP packet: tot_len: 79, ttl: 64
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sshd-1254728 [006] ..s1 8737831.674334: 0: Got IP packet: tot_len: 79, ttl: 64
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sshd-1254728 [006] ..s1 8737831.674349: 0: Got IP packet: tot_len: 72, ttl: 64
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node-1254811 [007] ..s1 8737831.674550: 0: Got IP packet: tot_len: 71, ttl: 64
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</code></pre>
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<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
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<p>TODO</p>
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