linux-kernel - Re: Expensive tcp_collapse with high tcp

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:   Thu, 6 Jan 2022 10:55:12 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Daniel Dao <dqminh@...udflare.com>
Cc:     netdev <netdev@...r.kernel.org>,
        kernel-team <kernel-team@...udflare.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Marek Majkowski <marek@...udflare.com>
Subject: Re: Expensive tcp_collapse with high tcp_rmem limit

On Thu, Jan 6, 2022 at 10:52 AM Eric Dumazet <edumazet@...gle.com> wrote:

> I think that you should first look if you are under some kind of attack [1]
>
> Eventually you would still have to make room, involving expensive copies.
>
> 12% of 16MB is still a lot of memory to copy.
>
> [1] Detecting an attack signature could allow you to zap the socket
> and save ~16MB of memory per flow.

I forgot to ask, have you set tcp_min_snd_mss to a sensible value ?

https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=5f3e2bf008c2221478101ee72f5cb4654b9fc363