setup_classid_environment(9)

✨ NAME ✨

okay bestie, welcome to setup_classid_environment(9) from the Kernel API Manual 💖 — this one is literally about Setup the cgroupv1 net_cls environment. No cap, that's the whole name vibe.

🎀 SYNOPSIS 🎀

int setup_classid_environment (void );

🦋 ARGUMENTS 🦋

• void — no arguments, bestie. Not a single one. 💅

🌸 DESCRIPTION 🌸

okay so listen 👑: this function should only be called in a custom mount namespace, like one created by running setup_cgroup_environment. Do not just raw-dog it in your normal namespace, fr fr 💀.

bestie, this is a caveat, not a suggestion — only call it in a custom mount namespace, e.g. created by running setup_cgroup_environment. 🫶

After calling this function, cleanup_classid_environment should be called once testing is complete. Yes, cleanup is also main character energy 🧹✨.

This function will print an error to stderr and return 1 if it is unable to setup the cgroup environment. If setup is successful, 0 is returned. That's it — 1 for "bestie it didn't work 😭", 0 for "slay, it worked 💅".

🔥 SEE ALSO 🔥

• Kernel file: ./tools/testing/selftests/bpf/cgroup_helpers.c
• enable_controllers(9)
• write_cgroup_file(9)
• write_cgroup_file_parent(9)
• setup_cgroup_environment(9)
• join_cgroup(9)
• join_root_cgroup(9)
• join_parent_cgroup(9)
• set_cgroup_xattr(9)
• __cleanup_cgroup_environment(9)
• cleanup_cgroup_environment(9)
• get_root_cgroup(9)
• create_and_get_cgroup(9)
• get_cgroup_id_from_path(9)
• set_classid(9)
• join_classid(9)
• cleanup_classid_environment(9)
• get_classid_cgroup_id(9)
• get_cgroup1_hierarchy_id(9)
• open_classid(9)

okay that's the whole page, bestie 💖 source/version vibes: ./tools/testing/selftests/bpf; date: October 2026; and yes, the page itself is setup_classid_environment(9) — bye, love u, periodt 🎀✨