On Sun, Dec 10, 2023 at 7:30 AM Eduard Zingerman [off-list ref] wrote:

On Thu, 2023-12-07 at 10:54 -0800, Andrii Nakryiko wrote:

quoted

Add fuller support for BPF token in high-level BPF object APIs. This is the
most frequently used way to work with BPF using libbpf, so supporting BPF
token there is critical.

Patch #1 is improving kernel-side BPF_TOKEN_CREATE behavior by rejecting to
create "empty" BPF token with no delegation. This seems like saner behavior
which also makes libbpf's caching better overall. If we ever want to create
BPF token with no delegate_xxx options set on BPF FS, we can use a new flag to
enable that.

Patches #2-#5 refactor libbpf internals, mostly feature detection code, to
prepare it from BPF token FD.

Patch #6 adds options to pass BPF token into BPF object open options. It also
adds implicit BPF token creation logic to BPF object load step, even without
any explicit involvement of the user. If the environment is setup properly,
BPF token will be created transparently and used implicitly. This allows for
all existing application to gain BPF token support by just linking with
latest version of libbpf library. No source code modifications are required.
All that under assumption that privileged container management agent properly
set up default BPF FS instance at /sys/bpf/fs to allow BPF token creation.

Patches #7-#8 adds more selftests, validating BPF object APIs work as expected
under unprivileged user namespaced conditions in the presence of BPF token.

fwiw, I've read through this patch-set and have not noticed any issues,
all seems good to me. Not sure if that worth much as I'm not terribly
familiar with code base yet.

Every extra pair of eyes is worth it :) Not finding anything obviously
broken is still a good result, thanks!

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