static u32 sk_skb_convert_ctx_access(enum bpf_access_type type,
				     const struct bpf_insn *si,
				     struct bpf_insn *insn_buf,
				     struct bpf_prog *prog, u32 *target_size)
{
	struct bpf_insn *insn = insn_buf;
	int off;

	switch (si->off) {
	case offsetof(struct __sk_buff, data_end):
		off  = si->off;
		off -= offsetof(struct __sk_buff, data_end);
		off += offsetof(struct sk_buff, cb);
		off += offsetof(struct tcp_skb_cb, bpf.data_end);
		*insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg,
				      si->src_reg, off);
		break;
	default:
		return bpf_convert_ctx_access(type, si, insn_buf, prog,
					      target_size);
	}

	return insn - insn_buf;
}
Unknown