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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">入门文档</li><li class="chapter-item expanded "><a href="../0-introduce/index.html"><strong aria-hidden="true">1.</strong> lesson 0-introduce</a></li><li class="chapter-item expanded "><a href="../1-helloworld/index.html"><strong aria-hidden="true">2.</strong> lesson 1-helloworld</a></li><li class="chapter-item expanded "><a href="../2-kprobe-unlink/index.html"><strong aria-hidden="true">3.</strong> lesson 2-kprobe-unlink</a></li><li class="chapter-item expanded "><a href="../3-fentry-unlink/index.html"><strong aria-hidden="true">4.</strong> lesson 3-fentry-unlink</a></li><li class="chapter-item expanded "><a href="../4-opensnoop/index.html"><strong aria-hidden="true">5.</strong> lesson 4-opensnoop</a></li><li class="chapter-item expanded "><a href="../5-uprobe-bashreadline/index.html"><strong aria-hidden="true">6.</strong> lesson 5-uprobe-bashreadline</a></li><li class="chapter-item expanded "><a href="../6-sigsnoop/index.html"><strong aria-hidden="true">7.</strong> lesson 6-sigsnoop</a></li><li class="chapter-item expanded "><a href="../7-execsnoop/index.html"><strong aria-hidden="true">8.</strong> lesson 7-execsnoop</a></li><li class="chapter-item expanded "><a href="../8-exitsnoop/index.html"><strong aria-hidden="true">9.</strong> lesson 8-execsnoop</a></li><li class="chapter-item expanded "><a href="../9-runqlat/index.html"><strong aria-hidden="true">10.</strong> lesson 9-runqlat</a></li><li class="chapter-item expanded "><a href="../10-hardirqs/index.html"><strong aria-hidden="true">11.</strong> lesson 10-hardirqs</a></li><li class="chapter-item expanded affix "><li class="part-title">进阶文档和示例</li><li class="chapter-item expanded "><a href="../11-bootstrap/index.html"><strong aria-hidden="true">12.</strong> lesson 11-bootstrap</a></li><li class="chapter-item expanded "><a href="../12-profile/index.html"><strong aria-hidden="true">13.</strong> lesson 12-profile</a></li><li class="chapter-item expanded "><a href="../13-tcpconnlat/index.html"><strong aria-hidden="true">14.</strong> lesson 13-tcpconnlat</a></li><li class="chapter-item expanded "><a href="../14-tcpstates/index.html"><strong aria-hidden="true">15.</strong> lesson 14-tcpstates</a></li><li class="chapter-item expanded "><a href="../15-javagc/index.html"><strong aria-hidden="true">16.</strong> lesson 15-javagc</a></li><li class="chapter-item expanded "><a href="../16-memleak/index.html"><strong aria-hidden="true">17.</strong> lesson 16-memleak</a></li><li class="chapter-item expanded "><a href="../17-biopattern/index.html"><strong aria-hidden="true">18.</strong> lesson 17-biopattern</a></li><li class="chapter-item expanded "><a href="../18-further-reading/index.html"><strong aria-hidden="true">19.</strong> lesson 18-further-reading</a></li><li class="chapter-item expanded "><a href="../19-lsm-connect/index.html"><strong aria-hidden="true">20.</strong> lesson 19-lsm-connect</a></li><li class="chapter-item expanded "><a href="../20-tc/index.html"><strong aria-hidden="true">21.</strong> lesson 20-tc</a></li><li class="chapter-item expanded "><a href="../21-xdp/index.html" class="active"><strong aria-hidden="true">22.</strong> lesson 21-xdp</a></li><li class="chapter-item expanded affix "><li class="part-title">高级主题</li><li class="chapter-item expanded "><a href="../22-android/index.html"><strong aria-hidden="true">23.</strong> 在 Android 上使用 eBPF 程序</a></li><li class="chapter-item expanded "><a href="../30-sslsniff/index.html"><strong aria-hidden="true">24.</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="../23-http/index.html"><strong aria-hidden="true">25.</strong> 使用 eBPF socket filter 或 syscall trace 追踪 HTTP 请求和其他七层协议</a></li><li class="chapter-item expanded "><a href="../29-sockops/index.html"><strong aria-hidden="true">26.</strong> 使用 sockops 加速网络请求转发</a></li><li class="chapter-item expanded "><a href="../24-hide/index.html"><strong aria-hidden="true">27.</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">28.</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">29.</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">30.</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">31.</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="../18-further-reading/ebpf-security.zh.html"><strong aria-hidden="true">32.</strong> eBPF 运行时的安全性与面临的挑战</a></li><li class="chapter-item expanded "><a href="../34-syscall/index.html"><strong aria-hidden="true">33.</strong> 使用 eBPF 修改系统调用参数</a></li><li class="chapter-item expanded "><a href="../35-user-ringbuf/index.html"><strong aria-hidden="true">34.</strong> eBPF开发实践：使用 user ring buffer 向内核异步发送信息</a></li><li class="chapter-item expanded "><a href="../36-userspace-ebpf/index.html"><strong aria-hidden="true">35.</strong> 用户空间 eBPF 运行时：深度解析与应用实践</a></li><li class="chapter-item expanded "><a href="../37-uprobe-rust/index.html"><strong aria-hidden="true">36.</strong> 使用 uprobe 追踪 Rust 应用程序</a></li><li class="chapter-item expanded "><a href="../38-btf-uprobe/index.html"><strong aria-hidden="true">37.</strong> 借助 eBPF 和 BTF，让用户态也能一次编译、到处运行</a></li><li class="chapter-item expanded affix "><li class="part-title">bcc 和 bpftrace 教程与文档</li><li class="chapter-item expanded "><a href="../bcc-documents/kernel-versions.html"><strong aria-hidden="true">38.</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">39.</strong> Kernel Configuration for BPF Features</a></li><li class="chapter-item expanded "><a href="../bcc-documents/reference_guide.html"><strong aria-hidden="true">40.</strong> bcc Reference Guide</a></li><li class="chapter-item expanded "><a href="../bcc-documents/special_filtering.html"><strong aria-hidden="true">41.</strong> Special Filtering</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial.html"><strong aria-hidden="true">42.</strong> bcc Tutorial</a></li><li class="chapter-item expanded "><a href="../bcc-documents/tutorial_bcc_python_developer.html"><strong aria-hidden="true">43.</strong> bcc Python Developer Tutorial</a></li><li class="chapter-item expanded "><a href="../bpftrace-tutorial/index.html"><strong aria-hidden="true">44.</strong> bpftrace Tutorial</a></li></ol>
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<h1 id="ebpf-入门实践教程二十一-使用-xdp-进行可编程数据包处理"><a class="header" href="#ebpf-入门实践教程二十一-使用-xdp-进行可编程数据包处理">eBPF 入门实践教程二十一： 使用 XDP 进行可编程数据包处理</a></h1>
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<p>在本教程中，我们将介绍 XDP（eXpress Data Path），并通过一个简单的例子帮助你入门。之后，我们将探讨更高级的 XDP 应用，例如负载均衡器、防火墙及其他实际应用。如果你对 eBPF 或 XDP 感兴趣，请在 <a href="https://github.com/eunomia-bpf/bpf-developer-tutorial">Github</a> 上为我们点赞！</p>
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<h2 id="什么是-xdp"><a class="header" href="#什么是-xdp">什么是 XDP？</a></h2>
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<p>XDP 是 Linux 内核中的一种高性能可编程数据路径，专为网络接口级的数据包处理而设计。通过将 eBPF 程序直接附加到网络设备驱动程序上，XDP 能够在数据包到达内核网络栈之前拦截并处理它们。这使得 XDP 能够进行极低延迟和高效的数据包处理，非常适合如 DDoS 防护、负载均衡和流量过滤等任务。实际上，XDP 每核心的吞吐量可以高达 <strong>每秒 2400 万包（Mpps）</strong>。</p>
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<h3 id="为什么选择-xdp"><a class="header" href="#为什么选择-xdp">为什么选择 XDP？</a></h3>
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<p>XDP 运行在比传统 Linux 网络组件（如 cBPF）更低的层级，在网络设备驱动程序的软中断上下文中执行。它能够在数据包被内核标准网络栈处理之前对其进行处理，避免了创建 Linux 中表示网络数据包的 <code>skb_buff</code> 结构。这种早期处理为简单但频繁的操作（如丢弃恶意数据包或负载均衡服务器）带来了显著的性能提升。</p>
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<p>与其他数据包处理机制相比，XDP 在性能和可用性之间取得了平衡，它利用了 Linux 内核的安全性和可靠性，同时通过可编程的 eBPF 提供了灵活性。</p>
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<h2 id="xdp-与其他方法的比较"><a class="header" href="#xdp-与其他方法的比较">XDP 与其他方法的比较</a></h2>
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<p>在 XDP 出现之前，一些解决方案通过完全绕过内核来加速数据包处理。其中一个显著的例子是 <strong>DPDK</strong>（数据平面开发工具包）。DPDK 允许用户空间应用程序直接控制网络设备，从而实现非常高的性能。然而，这种方法也存在一些权衡：</p>
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<ol>
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<li>
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<p><strong>缺乏内核集成</strong>：DPDK 及其他内核绕过解决方案无法利用现有的内核网络功能，开发者必须在用户空间重新实现许多协议和功能。</p>
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</li>
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<li>
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<p><strong>安全边界</strong>：这些绕过技术破坏了内核的安全模型，使得难以利用内核提供的安全工具。</p>
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</li>
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<li>
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<p><strong>用户空间与内核的转换开销</strong>：当用户空间数据包处理需要与传统内核网络交互时（例如基于套接字的应用程序），数据包必须重新注入到内核中，增加了开销和复杂性。</p>
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</li>
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<li>
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<p><strong>专用 CPU 使用</strong>：为了处理高流量，DPDK 和类似解决方案通常需要专用的 CPU 核心来处理数据包，这限制了通用系统的可扩展性和效率。</p>
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</li>
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</ol>
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<p>另一个替代 XDP 的方法是使用 Linux 网络栈中的 <strong>内核模块</strong> 或 <strong>挂钩</strong>。虽然这种方法可以很好地集成现有的内核功能，但它需要大量的内核修改，且由于在数据包处理管道的后期运行，无法提供与 XDP 相同的性能优势。</p>
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<h3 id="xdp--ebpf-的优势"><a class="header" href="#xdp--ebpf-的优势">XDP + eBPF 的优势</a></h3>
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<p>XDP 与 eBPF 结合提供了介于内核绕过方案（如 DPDK）和内核集成方案之间的中间地带。以下是 XDP + eBPF 脱颖而出的原因：</p>
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<ul>
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<li>
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<p><strong>高性能</strong>：通过在网络接口卡（NIC）驱动程序级别拦截数据包，XDP 可以实现接近线速的性能，用于丢弃、重定向或负载均衡数据包，同时保持低资源消耗。</p>
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</li>
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<li>
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<p><strong>内核集成</strong>：与 DPDK 不同，XDP 在 Linux 内核中工作，允许与现有的内核网络栈和工具（如 <code>iptables</code>、<code>nftables</code> 或套接字）无缝交互。无需在用户空间重新实现网络协议。</p>
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</li>
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<li>
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<p><strong>安全性</strong>：eBPF 虚拟机确保用户定义的 XDP 程序是被隔离的，不会对内核造成不稳定影响。eBPF 的安全模型防止恶意或有缺陷的代码损害系统，提供了一个安全的可编程数据包处理环境。</p>
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</li>
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<li>
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<p><strong>不需要专用 CPU</strong>：XDP 允许数据包处理而无需将整个 CPU 核心专用于网络任务。这提高了系统的整体效率，允许更灵活的资源分配。</p>
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</li>
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</ul>
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<p>总的来说，XDP + eBPF 提供了一种强大的可编程数据包处理解决方案，结合了高性能与内核集成的灵活性和安全性。它消除了完全绕过内核方案的缺点，同时保留了内核安全性和功能的优势。</p>
|
||
<h2 id="xdp-的项目和应用案例"><a class="header" href="#xdp-的项目和应用案例">XDP 的项目和应用案例</a></h2>
|
||
<p>XDP 已经在许多高调的项目中得到应用，这些项目展示了它在实际网络场景中的强大功能和灵活性：</p>
|
||
<h3 id="1-cilium"><a class="header" href="#1-cilium">1. <strong>Cilium</strong></a></h3>
|
||
<ul>
|
||
<li><strong>描述</strong>：Cilium 是一个为云原生环境（尤其是 Kubernetes）设计的开源网络、安全和可观测性工具。它利用 XDP 实现高性能的数据包过滤和负载均衡。</li>
|
||
<li><strong>应用案例</strong>：Cilium 将数据包过滤和安全策略卸载到 XDP，实现高吞吐量和低延迟的容器化环境流量管理，同时不牺牲可扩展性。</li>
|
||
<li><strong>链接</strong>：<a href="https://cilium.io/">Cilium</a></li>
|
||
</ul>
|
||
<h3 id="2-katran"><a class="header" href="#2-katran">2. <strong>Katran</strong></a></h3>
|
||
<ul>
|
||
<li><strong>描述</strong>：Katran 是由 Facebook 开发的第 4 层负载均衡器，优化了高可扩展性和性能。它使用 XDP 处理数据包转发，开销极小。</li>
|
||
<li><strong>应用案例</strong>：Katran 每秒处理数百万个数据包，高效地将流量分配到后端服务器上，利用 XDP 在大规模数据中心中实现低延迟和高性能的负载均衡。</li>
|
||
<li><strong>链接</strong>：<a href="https://github.com/facebookincubator/katran">Katran GitHub</a></li>
|
||
</ul>
|
||
<h3 id="3-cloudflare-的-xdp-ddos-保护"><a class="header" href="#3-cloudflare-的-xdp-ddos-保护">3. <strong>Cloudflare 的 XDP DDoS 保护</strong></a></h3>
|
||
<ul>
|
||
<li><strong>描述</strong>：Cloudflare 已经实现了基于 XDP 的实时 DDoS 缓解。通过在 NIC 级别处理数据包，Cloudflare 能够在恶意流量进入网络栈之前过滤掉攻击流量，最小化 DDoS 攻击对其系统的影响。</li>
|
||
<li><strong>应用案例</strong>：Cloudflare 利用 XDP 在管道早期丢弃恶意数据包，保护其基础设施免受大规模 DDoS 攻击，同时保持对合法流量的高可用性。</li>
|
||
<li><strong>链接</strong>：<a href="https://blog.cloudflare.com/l4drop-xdp-ebpf-based-ddos-mitigations/">Cloudflare 博客关于 XDP</a></li>
|
||
</ul>
|
||
<p>这些项目展示了 XDP 在不同领域的可扩展和高效的数据包处理能力，从安全和负载均衡到云原生网络。</p>
|
||
<h3 id="为什么选择-xdp-而不是其他方法"><a class="header" href="#为什么选择-xdp-而不是其他方法">为什么选择 XDP 而不是其他方法？</a></h3>
|
||
<p>与传统方法（如 <code>iptables</code>、<code>nftables</code> 或 <code>tc</code>）相比，XDP 提供了几个明显的优势：</p>
|
||
<ul>
|
||
<li>
|
||
<p><strong>速度与低开销</strong>：XDP 直接在 NIC 驱动程序中运行，绕过了内核的大部分开销，使数据包处理更快。</p>
|
||
</li>
|
||
<li>
|
||
<p><strong>可定制性</strong>：XDP 允许开发人员通过 eBPF 创建自定义的数据包处理程序，提供比传统工具（如 <code>iptables</code>）更大的灵活性和细粒度控制。</p>
|
||
</li>
|
||
<li>
|
||
<p><strong>资源效率</strong>：XDP 不需要像 DPDK 等用户空间解决方案那样将整个 CPU 核心专用于数据包处理，因此它是高性能网络的更高效选择。</p>
|
||
</li>
|
||
</ul>
|
||
<h2 id="编写-ebpf-程序"><a class="header" href="#编写-ebpf-程序">编写 eBPF 程序</a></h2>
|
||
<pre><code class="language-C">#include "vmlinux.h"
|
||
#include <bpf/bpf_helpers.h>
|
||
|
||
/// @ifindex 1
|
||
/// @flags 0
|
||
/// @xdpopts {"old_prog_fd":0}
|
||
SEC("xdp")
|
||
int xdp_pass(struct xdp_md* ctx) {
|
||
void* data = (void*)(long)ctx->data;
|
||
void* data_end = (void*)(long)ctx->data_end;
|
||
int pkt_sz = data_end - data;
|
||
|
||
bpf_printk("packet size is %d", pkt_sz);
|
||
return XDP_PASS;
|
||
}
|
||
|
||
char __license[] SEC("license") = "GPL";
|
||
</code></pre>
|
||
<p>这是一段 C 语言实现的 eBPF 内核侧代码，它能够通过 xdp 捕获所有经过目标网络设备的数据包，计算其大小并输出到 <code>trace_pipe</code> 中。</p>
|
||
<p>值得注意的是，在代码中我们使用了以下注释：</p>
|
||
<pre><code class="language-C">/// @ifindex 1
|
||
/// @flags 0
|
||
/// @xdpopts {"old_prog_fd":0}
|
||
</code></pre>
|
||
<p>这是由 eunomia-bpf 提供的功能，我们可以通过这样的注释告知 eunomia-bpf 加载器此 xdp 程序想要挂载的目标网络设备编号，挂载的标志和选项。</p>
|
||
<p>这些变量的设计基于 libbpf 提供的 API，可以通过 <a href="https://patchwork.kernel.org/project/netdevbpf/patch/20220120061422.2710637-2-andrii@kernel.org/#24705508">patchwork</a> 查看接口的详细介绍。</p>
|
||
<p><code>SEC("xdp")</code> 宏指出 BPF 程序的类型，<code>ctx</code> 是此 BPF 程序执行的上下文，用于包处理流程。</p>
|
||
<p>在程序的最后，我们返回了 <code>XDP_PASS</code>，这表示我们的 xdp 程序会将经过目标网络设备的包正常交付给内核的网络协议栈。可以通过 <a href="https://prototype-kernel.readthedocs.io/en/latest/networking/XDP/implementation/xdp_actions.html">XDP actions</a> 了解更多 xdp 的处理动作。</p>
|
||
<h2 id="编译运行"><a class="header" href="#编译运行">编译运行</a></h2>
|
||
<p>通过容器编译：</p>
|
||
<pre><code class="language-console">docker run -it -v `pwd`/:/src/ ghcr.io/eunomia-bpf/ecc-`uname -m`:latest
|
||
</code></pre>
|
||
<p>或是通过 <code>ecc</code> 编译：</p>
|
||
<pre><code class="language-console">$ ecc xdp.bpf.c
|
||
Compiling bpf object...
|
||
Packing ebpf object and config into package.json...
|
||
</code></pre>
|
||
<p>并通过 <code>ecli</code> 运行：</p>
|
||
<pre><code class="language-console">sudo ecli run package.json
|
||
</code></pre>
|
||
<p>可以通过如下方式查看程序的输出：</p>
|
||
<pre><code class="language-console">$ sudo cat /sys/kernel/tracing/trace_pipe
|
||
node-1939 [000] d.s11 1601.190413: bpf_trace_printk: packet size is 177
|
||
node-1939 [000] d.s11 1601.190479: bpf_trace_printk: packet size is 66
|
||
ksoftirqd/1-19 [001] d.s.1 1601.237507: bpf_trace_printk: packet size is 66
|
||
node-1939 [000] d.s11 1601.275860: bpf_trace_printk: packet size is 344
|
||
</code></pre>
|
||
<h2 id="总结"><a class="header" href="#总结">总结</a></h2>
|
||
<p>本文介绍了如何使用 xdp 来处理经过特定网络设备的包，基于 eunomia-bpf 提供的通过注释向 libbpf 传递参数的方案，我们可以将自己编写的 xdp BPF 程序以指定选项挂载到目标设备，并在网络包进入内核网络协议栈之前就对其进行处理，从而获取高性能的可编程包处理能力。</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。</p>
|
||
<h2 id="参考资料"><a class="header" href="#参考资料">参考资料</a></h2>
|
||
<ul>
|
||
<li><a href="http://arthurchiao.art/blog/xdp-paper-acm-2018-zh/">http://arthurchiao.art/blog/xdp-paper-acm-2018-zh/</a></li>
|
||
<li><a href="http://arthurchiao.art/blog/linux-net-stack-implementation-rx-zh/">http://arthurchiao.art/blog/linux-net-stack-implementation-rx-zh/</a></li>
|
||
<li><a href="https://github.com/xdp-project/xdp-tutorial/tree/master/basic01-xdp-pass">https://github.com/xdp-project/xdp-tutorial/tree/master/basic01-xdp-pass</a></li>
|
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