“Hi, I have the pleasure to announce the availability of a mirror for bpftool on GitHub, at the following URL:

https://github.com/libbpf/bpftool

This mirror is similar in spirit to the one for libbpf, and its creation was lead by the following motivations.

  1. The first goal is to provide a simpler way to build bpftool. So far, building a binary would require downloading the entire kernel repository. By contrast, the code in the GitHub mirror is mostly self-sufficient (it still requires libelf and zlib, and uses libbpf from its mirror as a git submodule), and offers an easy way to just clone and compile the tool.

  2. Because it is easier to compile and ship, this mirror should hopefully simplify bpftool packaging for distributions.

  3. Another objective was to help other projects build on top of the existing sources for bpftool. I’m thinking in particular of eBPF-for-Windows, which has been working on a proof-of-concept port of the tool for Windows. Bpftool’s mirror keeps the minimal amount of necessary headers, and stripped most of them from the definitions that are not required in our context, which should make it easier to uncouple bpftool from Linux.

  4. At last, GitHub’s automation features should help implement CI checks for bpftool, very much like libbpf is using today. The recent work conducted on libbpf’s CI and turning some of the checks into reusable GitHub Actions may help for bpftool.

Just to make it clear, bpftool’s mirror does not change the fact that all bpftool development happens on the kernel mailing-lists (in particular, the BPF mailing-list), and that the sources hosted in the kernel repository remain the reference for the tool. At this time the GitHub repository is just a mirror, and will not accept pull requests on bpftool’s sources.

Regarding synchronisation, the repository contains a script which should help cherry-pick all commits related to bpftool from the kernel repository. The idea is to regularly align bpftool on the latest version from libbpf’s mirror (that is to say, to cherry-pick all bpftool-related commits from bpf-next and bpf trees, up to the commit at which libbpf’s mirror stopped), to avoid any discrepancy between the tool and the library it relies on.

GitHub was the original home of bpftool, before Jakub moved it to kernel’s tools/ with commit 71bb428fe2c1 (“tools: bpf: add bpftool”) back in 2017. More than four years and five hundred commits later, it is time to have a stand-alone repository again! But over time, the build system and the header dependencies got somewhat intertwined, and extracting the tool again required a few careful steps. Some of them happened upstream: we addressed the licensing of a few bpftool dependencies, we switched to libbpf’s hash map implementation (instead of kernel’s), we fixed the way bpftool picks up the development headers from libbpf, and so on. Some other changes happened in the mirror, to adjust bpftool’s Makefile and build system. In the end, I’m rather happy with the result: the main Makefile in bpftool’s mirror only has a few minor changes with the reference one, and the C sources need no change at all. The tool you get from the mirror is the same as what you can compile from tools/bpf/bpftool/.

I hope that this mirror will make it easier to work and develop with bpftool. Thanks to Andrii for his feedback, and to the folks behind libbpf’s mirroring for their work, some of which I was happy to reuse.

Best regards,
Quentin”

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