linux-kernel - Re: [RFC PATCH net-next] tcp: add a tracepoint for tcp_listen_queue

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Date:   Thu, 13 Jul 2023 09:57:47 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Yan Zhai <yan@...udflare.com>
Cc:     Ivan Babrou <ivan@...udflare.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-team@...udflare.com,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        David Ahern <dsahern@...nel.org>
Subject: Re: [RFC PATCH net-next] tcp: add a tracepoint for
 tcp_listen_queue_drop

On Wed, 12 Jul 2023 21:43:32 -0500 Yan Zhai wrote:
> Those are not unnecessary calls, e.g. a lot of those kfree_skb come
> from iptables drops, tcp validation, ttl expires, etc. On a moderately
> loaded server, it is called at a rate of ~10k/sec, which isn't
> terribly awful given that we absorb millions of attack packets at each
> data center. We used to have many consume skb noises at this trace
> point with older versions of kernels, but those have gone ever since
> the better separation between consume and drop.

I was hoping you can break them down by category.

Specifically what I'm wondering is whether we should also have 
a separation between policy / "firewall drops" and error / exception
drops. Within the skb drop reason codes, I mean.