mirror of
https://github.com/eunomia-bpf/bpf-developer-tutorial.git
synced 2026-02-06 03:44:46 +08:00
implement tcp rtt tool (#26)
This commit is contained in:
try-agaaain
@@ -7,17 +7,193 @@
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网络质量，帮助用户定位问题来源。
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当有tcp链接建立时，该工具会自动根据当前系统的支持情况，选择合适的执行函数。
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在执行函数中，`tcprtt`会收集tcp链接的各项基本底薪，包括地址，源端口，目标端口，耗时
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在执行函数中，`tcprtt`会收集tcp链接的各项基本信息，包括地址，源端口，目标端口，耗时
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等等，并将其更新到直方图的map中。运行结束后通过用户态代码，展现给用户。
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## 编写 eBPF 程序
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TODO
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```c
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// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2021 Wenbo Zhang
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#include <vmlinux.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_core_read.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_endian.h>
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#include "tcprtt.h"
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#include "bits.bpf.h"
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#include "maps.bpf.h"
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char LICENSE[] SEC("license") = "Dual BSD/GPL";
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const volatile bool targ_laddr_hist = false;
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const volatile bool targ_raddr_hist = false;
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const volatile bool targ_show_ext = false;
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const volatile __u16 targ_sport = 0;
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const volatile __u16 targ_dport = 0;
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const volatile __u32 targ_saddr = 0;
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const volatile __u32 targ_daddr = 0;
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const volatile bool targ_ms = false;
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#define MAX_ENTRIES 10240
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/// @sample {"interval": 1000, "type" : "log2_hist"}
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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, u64);
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__type(value, struct hist);
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} hists SEC(".maps");
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static struct hist zero;
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SEC("fentry/tcp_rcv_established")
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int BPF_PROG(tcp_rcv, struct sock *sk)
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{
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const struct inet_sock *inet = (struct inet_sock *)(sk);
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struct tcp_sock *ts;
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struct hist *histp;
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u64 key, slot;
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u32 srtt;
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if (targ_sport && targ_sport != inet->inet_sport)
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return 0;
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if (targ_dport && targ_dport != sk->__sk_common.skc_dport)
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return 0;
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if (targ_saddr && targ_saddr != inet->inet_saddr)
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return 0;
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if (targ_daddr && targ_daddr != sk->__sk_common.skc_daddr)
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return 0;
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if (targ_laddr_hist)
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key = inet->inet_saddr;
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else if (targ_raddr_hist)
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key = inet->sk.__sk_common.skc_daddr;
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else
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key = 0;
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histp = bpf_map_lookup_or_try_init(&hists, &key, &zero);
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if (!histp)
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return 0;
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ts = (struct tcp_sock *)(sk);
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srtt = BPF_CORE_READ(ts, srtt_us) >> 3;
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if (targ_ms)
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srtt /= 1000U;
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slot = log2l(srtt);
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if (slot >= MAX_SLOTS)
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slot = MAX_SLOTS - 1;
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__sync_fetch_and_add(&histp->slots[slot], 1);
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if (targ_show_ext) {
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__sync_fetch_and_add(&histp->latency, srtt);
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__sync_fetch_and_add(&histp->cnt, 1);
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}
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return 0;
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}
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```
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这段代码是基于eBPF的网络延迟分析工具，它通过hooking TCP协议栈中的tcp_rcv_established函数来统计TCP连接的RTT分布。下面是这段代码的主要工作原理：
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1. 首先定义了一个名为"hists"的eBPF哈希表，用于保存RTT直方图数据。
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2. 当tcp_rcv_established函数被调用时，它首先从传入的socket结构体中获取TCP相关信息，包括本地/远程IP地址、本地/远程端口号以及TCP状态信息等。
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3. 接下来，代码会检查用户指定的条件是否匹配当前TCP连接。如果匹配失败，则直接返回。
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4. 如果匹配成功，则从"hists"哈希表中查找与本地/远程IP地址匹配的直方图数据。如果该IP地址的直方图不存在，则创建一个新的直方图并插入哈希表中。
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5. 接下来，代码会从socket结构体中获取当前TCP连接的RTT(srtt)，并根据用户设置的选项来将srtt值进行处理。如果用户设置了"-ms"选项，则将srtt值除以1000。
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6. 接着，代码会将srtt值转换为直方图的槽位(slot)，并将该槽位的计数器+1。
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7. 如果用户设置了"-show-ext"选项，则还会累加直方图的总延迟(latency)和计数(cnt)。
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## 编译运行
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eunomia-bpf 是一个结合 Wasm 的开源 eBPF 动态加载运行时和开发工具链，它的目的是简化 eBPF 程序的开发、构建、分发、运行。可以参考 <https://github.com/eunomia-bpf/eunomia-bpf> 下载和安装 ecc 编译工具链和 ecli 运行时。我们使用 eunomia-bpf 编译运行这个例子。
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TODO
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Compile:
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```shell
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docker run -it -v `pwd`/:/src/ yunwei37/ebpm:latest
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```
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或者
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```console
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$ ecc runqlat.bpf.c runqlat.h
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Compiling bpf object...
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Generating export types...
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Packing ebpf object and config into package.json...
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```
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Run:
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```console
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$ sudo ecli run package.json -h
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A simple eBPF program
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Usage: package.json [OPTIONS]
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Options:
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--verbose Whether to show libbpf debug information
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--targ_laddr_hist Set value of `bool` variable targ_laddr_hist
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--targ_raddr_hist Set value of `bool` variable targ_raddr_hist
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--targ_show_ext Set value of `bool` variable targ_show_ext
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--targ_sport <targ_sport> Set value of `__u16` variable targ_sport
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--targ_dport <targ_dport> Set value of `__u16` variable targ_dport
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--targ_saddr <targ_saddr> Set value of `__u32` variable targ_saddr
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--targ_daddr <targ_daddr> Set value of `__u32` variable targ_daddr
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--targ_ms Set value of `bool` variable targ_ms
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-h, --help Print help
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-V, --version Print version
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Built with eunomia-bpf framework.
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See https://github.com/eunomia-bpf/eunomia-bpf for more information.
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$ sudo ecli run package.json
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key = 0
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latency = 0
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cnt = 0
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(unit) : count distribution
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0 -> 1 : 0 | |
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2 -> 3 : 0 | |
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4 -> 7 : 0 | |
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8 -> 15 : 0 | |
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16 -> 31 : 0 | |
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32 -> 63 : 0 | |
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64 -> 127 : 0 | |
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128 -> 255 : 0 | |
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256 -> 511 : 0 | |
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512 -> 1023 : 4 |******************** |
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1024 -> 2047 : 1 |***** |
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2048 -> 4095 : 0 | |
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4096 -> 8191 : 8 |****************************************|
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key = 0
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latency = 0
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cnt = 0
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(unit) : count distribution
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0 -> 1 : 0 | |
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2 -> 3 : 0 | |
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4 -> 7 : 0 | |
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8 -> 15 : 0 | |
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16 -> 31 : 0 | |
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32 -> 63 : 0 | |
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64 -> 127 : 0 | |
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128 -> 255 : 0 | |
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256 -> 511 : 0 | |
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512 -> 1023 : 11 |*************************** |
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1024 -> 2047 : 1 |** |
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2048 -> 4095 : 0 | |
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4096 -> 8191 : 16 |****************************************|
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8192 -> 16383 : 4 |********** |
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```
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## 总结
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TODO
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tcprtt是一个基于eBPF的TCP延迟分析工具。通过hooking TCP协议栈中的tcp_rcv_established函数来统计TCP连接的RTT分布，可以对指定的TCP连接进行RTT分布统计，并将结果保存到eBPF哈希表中。同时，这个工具支持多种条件过滤和RTT分布数据扩展功能，以便用户可以更好地进行网络性能分析和调优。
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更多的例子和详细的开发指南，请参考 eunomia-bpf 的官方文档：<https://github.com/eunomia-bpf/eunomia-bpf>
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完整的教程和源代码已经全部开源，可以在 <https://github.com/eunomia-bpf/bpf-developer-tutorial> 中查看。
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31
src/15-tcprtt/bits.bpf.h
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31
src/15-tcprtt/bits.bpf.h
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@@ -0,0 +1,31 @@
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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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#ifndef __BITS_BPF_H
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#define __BITS_BPF_H
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#define READ_ONCE(x) (*(volatile typeof(x) *)&(x))
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#define WRITE_ONCE(x, val) ((*(volatile typeof(x) *)&(x)) = val)
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static __always_inline u64 log2(u32 v)
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{
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u32 shift, r;
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r = (v > 0xFFFF) << 4; v >>= r;
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shift = (v > 0xFF) << 3; v >>= shift; r |= shift;
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shift = (v > 0xF) << 2; v >>= shift; r |= shift;
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shift = (v > 0x3) << 1; v >>= shift; r |= shift;
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r |= (v >> 1);
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return r;
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}
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static __always_inline u64 log2l(u64 v)
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{
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u32 hi = v >> 32;
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if (hi)
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return log2(hi) + 32;
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else
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return log2(v);
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}
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#endif /* __BITS_BPF_H */
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26
src/15-tcprtt/maps.bpf.h
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26
src/15-tcprtt/maps.bpf.h
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@@ -0,0 +1,26 @@
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// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
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// Copyright (c) 2020 Anton Protopopov
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#ifndef __MAPS_BPF_H
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#define __MAPS_BPF_H
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#include <bpf/bpf_helpers.h>
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#include <asm-generic/errno.h>
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static __always_inline void *
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bpf_map_lookup_or_try_init(void *map, const void *key, const void *init)
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{
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void *val;
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long err;
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val = bpf_map_lookup_elem(map, key);
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if (val)
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return val;
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err = bpf_map_update_elem(map, key, init, BPF_NOEXIST);
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if (err && err != -EEXIST)
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return 0;
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return bpf_map_lookup_elem(map, key);
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}
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#endif /* __MAPS_BPF_H */
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75
src/15-tcprtt/tcprtt.bpf.c
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75
src/15-tcprtt/tcprtt.bpf.c
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@@ -0,0 +1,75 @@
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// SPDX-License-Identifier: GPL-2.0
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// Copyright (c) 2021 Wenbo Zhang
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#include <vmlinux.h>
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#include <bpf/bpf_helpers.h>
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#include <bpf/bpf_core_read.h>
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#include <bpf/bpf_tracing.h>
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#include <bpf/bpf_endian.h>
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#include "tcprtt.h"
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#include "bits.bpf.h"
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#include "maps.bpf.h"
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char LICENSE[] SEC("license") = "Dual BSD/GPL";
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const volatile bool targ_laddr_hist = false;
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const volatile bool targ_raddr_hist = false;
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const volatile bool targ_show_ext = false;
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const volatile __u16 targ_sport = 0;
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const volatile __u16 targ_dport = 0;
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const volatile __u32 targ_saddr = 0;
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const volatile __u32 targ_daddr = 0;
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const volatile bool targ_ms = false;
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#define MAX_ENTRIES 10240
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/// @sample {"interval": 1000, "type" : "log2_hist"}
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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, u64);
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__type(value, struct hist);
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} hists SEC(".maps");
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static struct hist zero;
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SEC("fentry/tcp_rcv_established")
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int BPF_PROG(tcp_rcv, struct sock *sk)
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{
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const struct inet_sock *inet = (struct inet_sock *)(sk);
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struct tcp_sock *ts;
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struct hist *histp;
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u64 key, slot;
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u32 srtt;
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if (targ_sport && targ_sport != inet->inet_sport)
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return 0;
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if (targ_dport && targ_dport != sk->__sk_common.skc_dport)
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return 0;
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if (targ_saddr && targ_saddr != inet->inet_saddr)
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return 0;
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if (targ_daddr && targ_daddr != sk->__sk_common.skc_daddr)
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return 0;
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if (targ_laddr_hist)
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key = inet->inet_saddr;
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else if (targ_raddr_hist)
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key = inet->sk.__sk_common.skc_daddr;
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else
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key = 0;
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histp = bpf_map_lookup_or_try_init(&hists, &key, &zero);
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if (!histp)
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return 0;
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ts = (struct tcp_sock *)(sk);
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srtt = BPF_CORE_READ(ts, srtt_us) >> 3;
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if (targ_ms)
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srtt /= 1000U;
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slot = log2l(srtt);
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if (slot >= MAX_SLOTS)
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slot = MAX_SLOTS - 1;
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__sync_fetch_and_add(&histp->slots[slot], 1);
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if (targ_show_ext) {
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__sync_fetch_and_add(&histp->latency, srtt);
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__sync_fetch_and_add(&histp->cnt, 1);
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}
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return 0;
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}
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13
src/15-tcprtt/tcprtt.h
Normal file
13
src/15-tcprtt/tcprtt.h
Normal file
@@ -0,0 +1,13 @@
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/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */
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#ifndef __TCPRTT_H
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#define __TCPRTT_H
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#define MAX_SLOTS 27
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struct hist {
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unsigned long long latency;
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unsigned long long cnt;
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unsigned int slots[MAX_SLOTS];
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};
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#endif /* __TCPRTT_H */
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Reference in New Issue
Block a user