bpf_skb_meta_pointer
void *bpf_skb_meta_pointer(struct sk_buff *skb, u32 offset);
memmove(dst, bpf_skb_meta_pointer(src->data, src->offset + offset), len);
return bpf_skb_meta_pointer(ptr->data, ptr->offset + offset);
memmove(bpf_skb_meta_pointer(skb, offset), from, len);