https://blog.dawnwl.com/tags/tcp/Recent content in TCP on 梓晨's BlogHugo -- gohugo.iozh-CN梓晨科技Sat, 10 Oct 2026 00:00:00 +0800https://blog.dawnwl.com/posts/linux-bbr/Fri, 06 Aug 2021 00:00:00 +0000https://blog.dawnwl.com/posts/linux-bbr/<h2 id="适用范围">适用范围 </h2><p>BBR 是 Linux 内核的 TCP 拥塞控制算法，适用性取决于内核编译配置、可用模块与权限，并非 Debian 专属。发行版名称不能代替内核能力检查；容器中能否修改参数还取决于宿主机与网络命名空间设置。</p> <h2 id="检查支持情况">检查支持情况 </h2><div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span><span class="lnt">2 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-sh" data-lang="sh"><span class="line"><span class="cl">uname -r </span></span><span class="line"><span class="cl">sysctl net.ipv4.tcp_available_congestion_control </span></span></code></pre></td></tr></table> </div> </div><p>如果没有 <code>bbr</code>，但系统提供对应模块，可加载后再次检查：</p> <div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span><span class="lnt">2 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-sh" data-lang="sh"><span class="line"><span class="cl">sudo modprobe tcp_bbr </span></span><span class="line"><span class="cl">sysctl net.ipv4.tcp_available_congestion_control </span></span></code></pre></td></tr></table> </div> </div><p>只有确认输出包含 <code>bbr</code> 后再修改。模块不存在时，需要换用或编译支持 BBR 的内核，不能只添加 sysctl 配置。</p> <h2 id="写入并加载配置">写入并加载配置 </h2><p>下面使用独立配置文件；已有同名文件时先检查和备份：</p> <div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span><span class="lnt">2 </span><span class="lnt">3 </span><span class="lnt">4 </span><span class="lnt">5 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-sh" data-lang="sh"><span class="line"><span class="cl"><span class="nb">printf</span> <span class="s1">&#39;%s\n&#39;</span> <span class="se">\ </span></span></span><span class="line"><span class="cl"> <span class="s1">&#39;net.core.default_qdisc = fq&#39;</span> <span class="se">\ </span></span></span><span class="line"><span class="cl"> <span class="s1">&#39;net.ipv4.tcp_congestion_control = bbr&#39;</span> <span class="se">\ </span></span></span><span class="line"><span class="cl"> <span class="p">|</span> sudo tee /etc/sysctl.d/99-bbr.conf </span></span><span class="line"><span class="cl">sudo sysctl -p /etc/sysctl.d/99-bbr.conf </span></span></code></pre></td></tr></table> </div> </div><p>开机持久化要求系统启动时读取 <code>/etc/sysctl.d/</code>，例如使用 systemd-sysctl 的系统。其他初始化系统和精简发行版需按其方式加载配置，不应仅凭文件存在判断重启后会生效。</p> <h2 id="验证">验证 </h2><div class="highlight"><div class="chroma"> <table class="lntable"><tr><td class="lntd"> <pre tabindex="0" class="chroma"><code><span class="lnt">1 </span></code></pre></td> <td class="lntd"> <pre tabindex="0" class="chroma"><code class="language-sh" data-lang="sh"><span class="line"><span class="cl">sysctl net.ipv4.tcp_congestion_control net.core.default_qdisc </span></span></code></pre></td></tr></table> </div> </div><p>预期分别为 <code>bbr</code> 与 <code>fq</code>。重启后再次验证。拥塞控制设置影响新连接，不保证所有线路测速都会提升。</p> <p>参考：<a class="link" href="https://docs.kernel.org/networking/ip-sysctl.html" target="_blank" rel="noopener" >Linux 内核 TCP sysctl 文档</a>。</p>