Re: [PATCH net-next 2/9] net: tcp: add 'drop_reason' field to struct tcp_skb_cb

[Eric Dumazet]

On Sat, Oct 29, 2022 at 6:11 AM <menglong8.dong@xxxxxxxxx> wrote:
>
> From: Menglong Dong <imagedong@xxxxxxxxxxx>
>
> Because of the long call chain on processing skb in TCP protocol, it's
> hard to pass the drop reason to the code where the skb is freed.
>
> Therefore, we can store the drop reason to skb->cb, and pass it to
> kfree_skb_reason(). I'm lucky, the struct tcp_skb_cb still has 4 bytes
> spare space for this purpose.

No, we have needs for this space for future use.

skb->cb[] purpose is to store semi-permanent info, for skbs that stay
in a queue.

Here, you need a state stored only in the context of the current context.
Stack variables are better.