How can I get container id from cgroup v1 with ebpf code?

How can I get container id from cgroup v1 with ebpf code? I can access task_struct->cgroups, but it(task_struct->cgroups) pointer content all zero.so I try task_struct->sched_task_group ,but always can not get container id。I try task_struct->group_leader and (task_struct->cgroups->dfl_cgrp) ,but result all failed.

The issue names no repository file, test, or entry point. Start by tracing how BCC handles eBPF access to task_struct and cgroup v1 data, then reproduce the reported zero or failed lookups; done means establishing a verified way to obtain the container ID or documenting the limitation.

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