STRUCT_OPS

[ ] LPC 2024

http://oldvger.kernel.org/bpfconf2024_material/struct_ops-lsfmmbpf-2024.pdf

这是什么高级话题？

• Fuse-BPF 看来还不在主线
  • https://lwn.net/Articles/937433/
• BPF qdisc
  • http://oldvger.kernel.org/bpfconf2024_material/BPF-Qdisc.pdf

LPC 2023

https://lpc.events/event/17/contributions/1607/attachments/1164/2407/lpc-struct_ops.pdf

The BPF struct_ops is a kernel-side feature in Linux which allows user-defined methods to be called by subsystems. For example, it is now possible to define a congestion control algorithm in BPF and then proceed to register it with the TCP subsystem in order to effectively regulate traffic

这里的代码尝试下

• https://docs.ebpf.io/linux/program-type/BPF_PROG_TYPE_STRUCT_OPS/

原始 patch

• https://lwn.net/Articles/809092/

The first use case included in this series is to implement TCP congestion control algorithm in BPF (i.e. implement struct tcp_congestion_ops in BPF).

There has been attempt to move the TCP CC to the user space (e.g. CCP in TCP).

The recent BPF advancements (in particular BTF-aware verifier, BPF trampoline, BPF CO-RE…) made implementing kernel struct ops (e.g. tcp cc) possible in BPF.

The idea is to allow implementing tcp_congestion_ops in bpf. It allows a faster turnaround for testing algorithm in the production while leveraging the existing (and continue growing) BPF feature/framework instead of building one specifically for userspace TCP CC.

信息量过大

1. BTF-aware verifier
2. BPF trampoline
3. 测试一下这里的内容 net/ipv4/bpf_tcp_ca.c
4. 和这里的 net/ipv4/tcp_dctcp.c

基本操作

sudo bpftool struct_ops show

bpftool struct_ops register bpf_cubic.o

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