Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <5J_z4QNPMBAk4y0rGshI7mBykT1tivh3037CbQRYXTu_Ra6zuojEcI0RB04ghXQxgdtDbt3YFv6sA882mrFyTdzQePwHwvLoECnqFTnYNZI=@protonmail.com>
In-Reply-To: <5J_z4QNPMBAk4y0rGshI7mBykT1tivh3037CbQRYXTu_Ra6zuojEcI0RB04ghXQxgdtDbt3YFv6sA882mrFyTdzQePwHwvLoECnqFTnYNZI=@protonmail.com>
From:   Neal Cardwell <ncardwell@google.com>
Date:   Sun, 16 May 2021 21:55:09 -0400
Message-ID: <CADVnQymGvCTEzdd8dSLZnn0dwnHAoNiwo72yEFeNr47+Na8GDg@mail.gmail.com>
Subject: Re: Listening on a TCP socket from a Kernel Module
To:     louisrossberg <louisrossberg@protonmail.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Netdev <netdev@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Sun, May 16, 2021 at 7:20 PM louisrossberg
<louisrossberg@protonmail.com> wrote:
>
> Hello, can somebody point me in the right direction for
> what I would use to listen on a TCP socket from the
> kernel? I am working on a kernel module and have spent the
> past day looking through include/net and include/linux for
> something that would allow me to do so. I know TCP
> listening is typically done in userspace, but it should be
> possible at the kernel level right?  tcp_diag looks
> promising, but it seems like that is mainly for monitoring
> sockets, and I'm not sure if I would be able to provide
> responses from it.
>
> Louis Rossberg,
> Warped Technologies

Perhaps kernel_listen() and related functions (kernel_bind(),
kernel_accept(), etc.) in net/socket.c might do the trick for your use
case? Looking at how the callers of these functions structure their
code might give you enough to go on.

(I'm adding the Linux kernel networking mailing list to this thread as well.)

best regards,
neal