netdev - Re: Verify ACK packets in handshake in kernel module (Access TCP state table)

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Sat, 21 Sep 2019 05:15:29 +0200
From:   Willy Tarreau <w@....eu>
To:     Swarm <thesw4rm@...me>
Cc:     netdev@...r.kernel.org
Subject: Re: Verify ACK packets in handshake in kernel module (Access TCP
 state table)

On Fri, Sep 20, 2019 at 11:43:50PM +0000, Swarm wrote:
> First time emailing to this mailing list so please let me know if I made a
> mistake in how I sent it. I'm trying to receive a notification from the
> kernel once it verifies an ACK packet in a handshake. Problem is, there is no
> API or kernel resource I've seen that supports this feature for both
> syncookies and normal handshakes. Where exactly in the kernel does the ACK
> get verified? If there isn't a way to be notified of it, where should I start
> adding that feature into the kernel?

Just searching for TCP_ESTABLISHED immediately brought me to tcp_input.c
(tcp_rcv_state_process() to be precise), so I'm not sure you've searched
that much. As you've noticed there's nothing specifically called in this
case, but in practice a caller of accept() on a listening socket will be
woken up.

Hoping this helps,
Willy