linux-kernel - Re: [PATCH] tcp:provide 2 options for MSS/TSO window size: half the window or full window.

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] [day] [month] [year] [list]

Message-ID: <CADVnQy=4BRX-z97s2qnNjLDSOr5hce4x6xknaySy6=Wrpjhn1A@mail.gmail.com>
Date: Wed, 19 Nov 2025 11:43:30 -0500
From: Neal Cardwell <ncardwell@...gle.com>
To: "He.kai Zhang.zihan" <hk517j@...mail.com>
Cc: edumazet@...gle.com, kuniyu@...gle.com, davem@...emloft.net, 
	kuba@...nel.org, pabeni@...hat.com, horms@...nel.org, dsahern@...nel.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcp:provide 2 options for MSS/TSO window size: half the
 window or full window.

On Wed, Nov 19, 2025 at 11:30 AM He.kai Zhang.zihan <hk517j@...mail.com> wrote:

Please read the following before sending your next patch:

https://docs.kernel.org/process/maintainer-netdev.html
https://docs.kernel.org/process/submitting-patches.html

Rather than attaching patches, please use "git send-email" when
sending patches, with something like the following for networking
patches:

# first check:
./scripts/checkpatch.pl *.patch
# fix any issues

# then send:
git send-email \
  --to 'David Miller <davem@...emloft.net>' \
  --to 'Jakub Kicinski <kuba@...nel.org>' \
  --to 'Eric Dumazet <edumazet@...gle.com>' \
  --cc 'netdev@...r.kernel.org'  *.patch

On the specifics of your patch:

(1) Can you please send a tcpdump packet trace showing the problem you
are trying to solve, and then another trace showing the behavior after
your patch is applied?

(2) Can you please provide your analysis of why the existing code in
tcp_bound_to_half_wnd() does not achieve what you are looking for? It
already tries to use the full receive window when the receive window
is small. So perhaps all we need is to change the
tcp_bound_to_half_wnd() logic to not use half the receive window if
the receive window is less than 1 MSS or so, rather than using a
threshold of TCP_MSS_DEFAULT?

thanks,
neal