// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2018 Facebook

#include <vmlinux.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_core_read.h>
#include "bpf_tracing_net.h"
#define NUM_CGROUP_LEVELS       4

__u64 cgroup_ids[NUM_CGROUP_LEVELS];
__u16 dport;

static __always_inline void log_nth_level(struct __sk_buff *skb, __u32 level)
{
        /* [1] &level passed to external function that may change it, it's
         *     incompatible with loop unroll.
         */
        cgroup_ids[level] = bpf_skb_ancestor_cgroup_id(skb, level);
}

SEC("tc")
int log_cgroup_id(struct __sk_buff *skb)
{
        struct sock *sk = (void *)skb->sk;

        if (!sk)
                return TC_ACT_OK;

        sk = bpf_core_cast(sk, struct sock);
        if (sk->sk_protocol == IPPROTO_UDP && sk->sk_dport == dport) {
                log_nth_level(skb, 0);
                log_nth_level(skb, 1);
                log_nth_level(skb, 2);
                log_nth_level(skb, 3);
        }

        return TC_ACT_OK;
}

char _license[] SEC("license") = "GPL";