From: Florian Westphal <fw@strlen.de>
To: Kacper Kokot <kacper.kokot.44@gmail.com>
Cc: Pablo Neira Ayuso <pablo@netfilter.org>,
Phil Sutter <phil@nwl.cc>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] netfilter: TCPMSS: fix dropped packets when MSS option is unaligned
Date: Mon, 25 May 2026 23:28:25 +0200 [thread overview]
Message-ID: <ahS--cPlhv6NHAcO@strlen.de> (raw)
In-Reply-To: <20260525201116.407338-2-kacper.kokot.44@gmail.com>
Kacper Kokot <kacper.kokot.44@gmail.com> wrote:
> Padding TCP options with NOPs is optional, so it is legal to send an
> MSS option that is not aligned to a word boundary and therefore not
> aligned for checksum calculation. The current TCPMSS target is not
> robust to this: when the MSS option is unaligned it produces an
> invalid checksum, and the packet is dropped.
Is this an actual, real world bug? This code is 20+ years old, all that
this hints at is that they are always aligned in reality?
(Not disputing theoretical problem).
next prev parent reply other threads:[~2026-05-25 21:28 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-25 20:11 [PATCH] netfilter: TCPMSS: fix dropped packets when MSS option is unaligned Kacper Kokot
2026-05-25 21:28 ` Florian Westphal [this message]
2026-05-25 21:44 ` Kacper Kokot
2026-05-25 22:08 ` Fernando Fernandez Mancera
2026-05-26 9:31 ` David Laight
2026-05-26 13:50 ` kernel test robot
2026-05-26 15:18 ` David Laight
2026-05-26 16:46 ` kernel test robot
2026-05-26 23:21 ` Kacper Kokot
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