linux-kernel - Re: [PATCH v1 3/3] liveupdate: suppress TCP RST during post-kexec restore window

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Message-ID: <20260130170533.257db5fb@kernel.org>
Date: Fri, 30 Jan 2026 17:05:33 -0800
From: Jakub Kicinski <kuba@...nel.org>
To: Li Chen <me@...ux.beauty>
Cc: Jonathan Corbet <corbet@....net>, Pasha Tatashin
 <pasha.tatashin@...een.com>, Mike Rapoport <rppt@...nel.org>, Pratyush
 Yadav <pratyush@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Neal
 Cardwell <ncardwell@...gle.com>, Kuniyuki Iwashima <kuniyu@...gle.com>,
 "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, Andrew
 Morton <akpm@...ux-foundation.org>, "Borislav Petkov (AMD)" <bp@...en8.de>,
 Randy Dunlap <rdunlap@...radead.org>, Pawan Gupta
 <pawan.kumar.gupta@...ux.intel.com>, Petr Mladek <pmladek@...e.com>, Feng
 Tang <feng.tang@...ux.alibaba.com>, Kees Cook <kees@...nel.org>, Li
 RongQing <lirongqing@...du.com>, Arnd Bergmann <arnd@...db.de>, Askar Safin
 <safinaskar@...il.com>, Frank van der Linden <fvdl@...gle.com>,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org
Subject: Re: [PATCH v1 3/3] liveupdate: suppress TCP RST during post-kexec
 restore window

On Fri, 30 Jan 2026 22:51:19 +0800 Li Chen wrote:
> During a kexec-based live update, userspace may restore established TCP
> connections after the new kernel has booted (e.g. via CRIU). Any packet
> arriving for a not-yet-restored socket will hit the no-socket path and
> trigger a TCP RST, causing the peer to immediately drop the connection.

Can you not add a filter to simply drop those packets until workload is
running again? It'd actually be less racy than this hac^w patch ...