linux-kernel - Re: [RFC PATCH v3 09/12] net: add support for skbs with unreadable frags

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Message-ID: <CANn89iJNR8bYYBO92=f5_2hFoTK8+giH11o-7NHURoahwvV11w@mail.gmail.com>
Date:   Tue, 7 Nov 2023 22:17:42 +0100
From:   Eric Dumazet <edumazet@...gle.com>
To:     Stanislav Fomichev <sdf@...gle.com>
Cc:     Mina Almasry <almasrymina@...gle.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        David Ahern <dsahern@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-kselftest@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Shuah Khan <shuah@...nel.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Jeroen de Borst <jeroendb@...gle.com>,
        Praveen Kaligineedi <pkaligineedi@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Kaiyuan Zhang <kaiyuanz@...gle.com>
Subject: Re: [RFC PATCH v3 09/12] net: add support for skbs with unreadable frags

On Tue, Nov 7, 2023 at 10:05 PM Stanislav Fomichev <sdf@...gle.com> wrote:

>
> I don't understand. We require an elaborate setup to receive devmem cmsgs,
> why would some random application receive those?


A TCP socket can receive 'valid TCP packets' from many different sources,
especially with BPF hooks...

Think of a bonding setup, packets being mirrored by some switches or
even from tc.

Better double check than be sorry.

We have not added a 5th component in the 4-tuple lookups, being "is
this socket a devmem one".

A mix of regular/devmem skb is supported.